Special Session FO-8
Smart Polymers for Biomedical Applications

Session FO-8.1 - Shape-memory and Shape-changing Polymers for Biomedical Applications

FO-8.1:IL01  Thermally Activated Shape Memory Polymers
D.J. MAITLAND, T. LANDSMAN, Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA

We will present our latest work with thermally activated shape memory polymer (SMP) polyurethane materials and devices. Recent progress with the SMP devices include multiple device applications (stroke treatments, stents, other interventional devices), functional animal studies, synthesis and characterization of new SMP materials, in vivo and in vitro biocompatibility studies and device-tissue interactions for the laser, resistive, or magnetic-field activated actuators. The CIMTEC 2014 paper will highlight our most recent work in SMPs and SMP devices: foam scaffolds for treating aneurysms, healing pathology of implanted foams, clotting dynamics in the foam, new SMP materials, and modeling SMP devices.


FO-8.1:IL02  Degradable Shape Memory Polymers for Orthopedic Applications
JIE SONG, JIANWEN XU, T. FILION, A. KUTIKOV, Department of Orthopedics & Physical Rehabilitation, Department of Cell & Developmental Biology, University of Massachusetts Medical School, Worcester, MA, USA

Regenerative medicine aspires to reduce reliance on or overcome limitations associated with donor tissue-mediated repair. A major roadblock in translating scaffold-based regenerative medicine into clinical practice is the lack of materials combining tissue-like physical and biochemical properties with desirable surgical handling characteristics to enable their safe delivery and integration with target tissue. Nanostructured material design platform provides a unique opportunity to integrate physical, biochemical, and mechanical signals for complex regenerative medicine applications. In this talk, a nanoparticle-mediated strategy towards high-performance thermal-responsive shape memory polymer (SMP) implants for weight-bearing orthopedic applications will be presented. The discussion will be focused on addressing the multiple challenges relating to the biological applications of thermal-responsive SMP implants (e.g. achieving high shape memory performance around physiological temperatures, functionalization with biomolecules/integration with biominerals without compromising shape memory performances/mechanical integrity) via well-controlled network designs. The biocompatibility of these SMPs including the immunogenicity of their degradation products in vivo will also be discussed.


FO-8.1:IL03  Shape-memory Nanopatterns Direct Cell Orientation
M. EBARA, K. UTO, T. AOYAGI, National Institute for Materials Science (NIMS), Tsukuba, Japan

We report here that the direction of aligned cells on nanopatterns can be tuned to a perpendicular direction without use of any biochemical reagents. This was enabled by shape-memory activation of nanopatterns that transition from a memorized temporal pattern to the original permanent pattern by heating. The thermally induced shape-memory nanopatterns were prepared by chemically crosslinking semi-crystalline poly(caprolactone) (PCL) in a mold to show shape-memory effects over its melting temperature (Tm = 33oC). To investigate the role of dynamic and reversible surface nanopatterns on cell alignment on the PCL films before and after a topographic transition, NIH 3T3 fibroblasts were seeded on fibronectin-coated PCL films with a temporary grooved topography (grooves with a height of 300 nm and width of 2 μm are spaced 9 μm apart). Interestingly, cells did not change their direction just after the surface transition. However, cell alignment was gradually lost with time, and finally cells realigned parallel to the emerged permanent grooves. The addition of cytoskeletal inhibitor prevented realignment. These results clearly indicate that cells can sense dynamic changes in the surrounding environments and spontaneously adapt to a new environment by remodeling their cytoskeleton.


FO-8.1:L04  Scaffold Roughness Regulates the Endothelial Differentiation of Human Adipose Derived Mesenchymal Stem Cells
ZHENGDONG LI^{1, 2}, WEIWEI WANG¹, K. KRATZ^{1, 3}, XUN XU^{1, 2}, M. ROCH¹, A. KURTZ¹, M. GOSSEN¹, F. JUNG^{1, 3}, NAN MA^{1, 3}, A. LENDLEIN^{1, 3}, ¹Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow, Germany; ²Institute of Chemistry and Biochemistry, Free University of Berlin, Berlin, Germany; ³Helmholtz Virtual Institute - Multifunctional Materials in Medicine, Berlin and Teltow, Germany

The fate and functions of stem cells are strongly dependent on the physicochemical conditions of the scaffold. Here, we reported that the microscale roughness of the scaffold could affect the human adipose tissue derived mesenchymal stem cells (hADSCs). Polymeric inserts with different roughness (0.12 ± 0.04 µm (R0); 3.52 ± 0.26 µm (R1); 16.04 ± 1.24 µm (R2)) were coated with fibronectin for cell culture. There was no significant influence of roughness on cell adhesion, cell morphology and cytoskeletal structure. Surface R2 facilitated cell proliferation and decreased the apoptosis. With the increase of the roughness level, an increasing trend of the endothelial differentiation was observed. 6.61 ± 3.60% vWF positive cells were detected on R2, which was higher than that on R0 (0.51 ± 0.11%) and R1 (2.09 ±0.62%). The conditioned media (CM) collected from hADSCs cultured on the scaffolds with different roughness also affected the cells. CM-R1 and CM-R2 significantly improved, compared with CM-R0, the migration activity of the hADSCs. CM-R1 significantly enhanced the capillary-like tube formation of the cells. Our finding demonstrated that the appropriate level of surface roughness could be used to regulate hADSCs and direct their differentiation towards endothelial cells.


FO-8.1:IL05  Shape-­changing Materials for Basic and Applied Mechanobiology
J.H. HENDERSON, Syracuse University, Syracuse, NY, USA

In vitro studies have begun to elucidate the principles through which biophysical aspects of extracellular matrix (ECM) behavior support and regulate tissue development, disease, and healing. Engineered 2D and 3D substrates and scaffolds have provided increasingly powerful tools with which to investigate the relationships between cell mechanical behavior and ECM composition and organization. But substrates and scaffolds are often static structures, unchanged over time, providing poor mimics of dynamic in vivo environments. As engineered in vitro environments become more accurate biochemical and biophysical tools for investigating, modeling, and engineering in vivo environments, the critical next step for many areas of cell biomechanics and mechanobiology will be incorporation of increased programmable physical functionality into the environments. To this end, we have been investigating the use of shape memory polymers for the study and application of mechanobiology. Here we will present ongoing work on programmable cell culture substrates and scaffolds. The use of such substrates and scaffolds for investigation of mechanotransduction, cell biomechanical function, cell soft-­matter physics, and for tissue engineering and regenerative medicine will be discussed.


FO-8.1:IL06  Shape Memory Polymer Foams for Medical Device Applications
T.S. WILSON, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA; A. BOYLE, Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA

This presentation will review the current state of the art in shape memory polymer foams directed at biomedical applications. The general history of SMP foam development will be summarized with emphasis on the major developments related to biomedical applications. This will be followed by a summary of the twelve or so years our group has spent developing SMP foams utilizing a device based design approach to targeting specifically foams for the embolization of cerebral aneurysms. Device functional requirements will be described, leading to desired material characteristics, in turn leading to the design of specific polymer chemistries, macromolecular structures, and foam macrostructures. Finally, some of the remaining challenges toward the application of SMP foams in devices will be presented.


FO-8.1:IL07  Reversible Actuation of Polymer Networks by Directed Crystallization
M. BEHL, K. KRATZ, U. NÖCHEL, A. LENDLEIN, Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow, Germany

Shape-memory polymers have evolved as a valuable technology for biomedical applications but were limited by their one-way character: SMP can be programmed in a new temporary shape, from which they recover their original shape when heated, but do not return to their programmed temporary shape upon cooling again. Here we present multiphase polymer networks, which can be repetitively actuated under stress-free conditions between two different, programmable shapes either as a reversible, bidirectional shape-memory effect or as a temperature-memory polymer actuation [1, 2]. In both cases it turned out that the key to success was the separation of the shape shifting geometry from the actuation capability obtained by directed crystallization of polymer chain segments kept under constant stress. It is supposed that this reversible actuation technology will stimulate the design of smart biomedical devices such as reversible fastening devices.
References
[1] M. Behl, K. Kratz, J. Zotzmann, U. Noechel, A. Lendlein, Adv. Mater. 2013, 25, 4466-4469.
[2] M. Behl, K. Kratz, U. Noechel, T. Sauter, A. Lendlein, Proc Natl Acad Sci USA 2013, 110, 12555-12559.


FO-8.1:L08  Amphiphilc Shape Recovery Functional Nanocellulose Aerogels
YOU-LO HSIEH, FENG JIANG, Fiber and Polymer Science, University of California, Davis, CA, USA

Super-absorbent amphiphilic aerogels have been robustly fabricated from nanocellulose via green processes. Cellulose nanofibrils, as thin as 1 nm and as long as few micrometers, have been isolated at nearly 100% yield from under-utilized agricultural and processing byproducts. By targeting geometrical dimensions, surface functionalities and aqueous suspension conditions, the chemically and structurally versatile nanocellulose could be assembled into a variety of fibrillar and microporous-to-mesoporous network structures, such as aerogels. Nanocellulose aerogels of ultralow density (1.7 mg/cm3), super porosity (99.5%), super-amphiphilic absorbency (e.g., 210 g/g wáter, 375 g/g hydrocarbons) have shown exceptional wet resiliency and full wáter-activated shape recovery over 100 cycles. The amphiphilicity could be further tuned toward greater hydrophobicity, affording excellent selective absorption of non-polar liquids from water. The unique super-hydrophilicity, super-oleophilicity, enzyme binding and antimicrobial behaviors of these nanocellulose aerogels will be presented for applications in selective separation, bioactive agent carriers and catalysis.
The authors acknowledge funding from USDA NIFA and California Rice Research Board as well as Chevron, NSF DBIO722538 and NIH RR11


Session FO-8.2 - Light-sensitive Polymers for Biomedical Applications

FO-8.2:IL01  Synthesis, Functionalization and Biological Applications of Porous Polymer Surfaces
P. LEVKIN, Karlsruhe Institute of Technology, Institute of Toxicology and Genetics Heidelberg University, Applied Physical Chemistry, Eggenstein-Leopoldshafen, Germany

Water on superhydrophilic surfaces spreads or is absorbed very quickly, while water on superhydrophobic water repellent surfaces forms spherical droplets and rolls off the surface easily. Combining these two extreme states of superhydrophilicity and superhydrophobicity on the same surface in precise two-dimensional micropatterns opens exciting new functionalities and possibilities in a wide variety of applications from cell, droplet, and hydrogel microarrays for screening to surface tension confined microchannels for separation and diagnostic devices. In this talk I will present our recent results on the development of both superhydrophobic and superhydrophilic polymer surfaces, their functionalization and micropatterning. Different biological applications of produced polymer substrates, including cell patterning, cell screening, formation of slippery antibiofouling and cell repellant surfaces, will be discussed.


FO-8.2:IL02  Dynamic Cell Microenvironments
A. DEL CAMPO, Max-Planck-Institut für Polymerforschung, Mainz, Germany

Cells in vivo are exposed to spatially encoded signals that dynamically change over time, and so does cell response. Different chemical and physical signals over a wide range of concentration, time- and length scales are involved. In vitro modelling of this scenario requires the development of tools that enable remote control of multiple chemical and physical properties of the cellular microenvironment independently. Photoremovable protecting groups (cages) sensitive to different wavelengths have been used for this purpose and allow phototunable cellular microenvironments with biologically relevant physical and chemical characteristics that can be modulated on-demand. These provide new capabilities for understanding how cells receive information and how these signals switch on/off proliferation and specialization programs to either promote tissue growth, destruction or dysfunction and can be applied to a rational design of materials for regenerative medicine.


FO-8.2:L03  Reversible Photochromic Polynorbornenes Bearing Spiropyran Side Groups for Layer-by-layer Coatings
L. FLOREA¹, C. MOLONEY¹, D. NIXON¹, S. MOULTON², G.W. WALLACE², F. BENITO-LOPEZ^{1, 3}, D. DIAMOND¹, ¹INSIGHT, National Centre for Sensor Research, Dublin City University, Dublin, Ireland; ²ARC Centre of Excellence for Electromaterials Science and Intelligent Polymer Research Institute, University of Wollongong; ³CIC microGUNE, Arrasate-Mondragón, Spain

A great number of stimuli-responsive materials have been reported in the recent years and they find applicability in fields ranging from optoelectronics, surface coatings, photonics and biomedicine. A particular attractive class of stimuli-responsive materials are photo-responsive materials as light is an environment-friendly stimulus and can be applied remotely, in a non-invasive manner. Photo-responsive materials have been the subject of many investigations over the past decade due to their potential applications, particularly in the design and development of memory devices, artificial muscles, soft-actuators and drug delivery, among others[1]. In the field of photo-responsive polymers, the layer-by-layer (LbL) approach offers a simple and effective method to fabricate uniform thin films capable of photo-modulation.
In this context, we are focusing our investigations on the synthesis of LbL coatings based on new photochromic norbornenes polymers bearing spiropyran side groups. We have shown that these LbL coatings are capable of disassembling upon photostimulation. When used for the coating of microcapsules, these polymers have the ability to be used for photo-controlled drug delivery.
[1] L. Florea, D. Diamond, F. Benito-Lopez, Macromol. Mater. Eng. 2012, 297, 11.


FO-8.2:L04  Light-driven Polymer Nanowire for Cell Manipulation
J. LEE¹, S. OH², J. PYO¹, J. KIM², JUNG HO JE¹, ¹X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science & Technology, Pohang, Korea; ²Institute of Nanoscience and Technology, Department of Chemical Engineering, Hanyang University, Seoul, Korea

Photomechanical soft actuator has been drawing a great attention because of its wireless and rapid actuation in applications of artificial muscle and drug delivery, etc. Development of photomechanical nanowire (NW) actuators, which is critically demanded not only for a significant enhancement of opto-mechanical energy conversion efficiency but also for minimization of light-induced biological damage[ref], has been however largely unexplored. Here, we report successful demonstration of single light-driven NW actuators based on using an azobenzene-containing supramolecule. We find that single NWs of tris(4-((E)-phenyldiazenyl)phenyl)-benzene-1,3,5-tricarboxamide (Azo-1) exhibit a reversible bending and unbending behavior upon irradiation with UV and visible light, respectively. Based on individual integration of Azo-1 (photomechanical) and polystyrene (non-photomechanical) NWs, we demonstrate a wireless light-driven NW tweezers that remotely manipulate individual live cells on exposure to UV light. Our photo-responsive NW actuators might open a new gateway for individually addressable manipulation of micro-cells in biomedical science and engineering.


FO-8.2:L05  Chemo-responsive Polymer Networks Containing Coordination Crosslinks and Covalent Netpoints
P. ZHANG^{1, 2, 3}, M. BEHL^{1, 3}, A. LENDLEIN^{1, 2, 3}, ¹Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow, Germany; ²Institute of Chemistry, University of Potsdam, Potsdam, Germany; ³Tianjin University-HZG Research Center Joint Laboratory for Biomaterials and Regenerative Medicine, Tianjin, China, and Teltow, Germany

Rhodium-phosphine coordination bonds, owing to their “dynamic” nature [1], have been utilized to build coordination polymer networks, which are capable of chemo-responsive behaviour upon addition of free phosphorous ligands. These chemo-responsive rhodium-phosphine coordination polymer networks (RPCPNs) have found a wide range of application (e.g. sensors and intelligent switches). However, the RPCPNs in which all crosslinks were based on the coordination bonds, liquefy upon stimulation.
We explored whether RPCPNs can be prepared, which provide a certain stability of the polymer network even cleavage of phosphorous ligand based crosslinks after stimulation. Our approach is based on RPCPNs containing covalent netpoints. The RPCPNs were prepared by copolymerization of n-butylacrylate with diphenylphosphinostyrene and poly(propylene glycol) dimethacrylate acting as crosslinker, which were afterwards complexed with [RhCl(COD)]₂ in chloroform. The formation of the rhodium-phosphine coordination bonds in polymer network was proved by UV-VIS and IR spectroscopy. When triphenylphosphine (Ph₃P) was added, the RPCPNs softened and swelled, but did not dissolve, indicating a stable chemo-responsive behavior.
Reference
Jos M.J. Paulusse, D.J.M. van Beek, and Rint P. Sijbesma, J. Am. Chem. Soc. 129, 2392-2397 (2007).

 
Session FO-8.3 - Smart Composites for Biomedical Applications

FO-8.3:IL01  Polyurethane Based Shape-memory Polymers
WEI MIN HUANG, Nanyang Technological University, Singapore

After being severely and quasi-plastically deformed, shape memory polymers (SMPs) are able to recover their original shape only upon the presence of the right stimulus. This phenomenon is known as the shape memory effect (SME). Typical stimuli to activate shape recovery include heat (thermo-responsive), chemical (chemo-responsive), and light (photo-responsive) etc.
As one of the most popular SMPs at present, polyurethane has been investigated extensively in the past and a range of applications, including biomedical applications due to its excellent biocompability, have been proposed and developed.
In this talk, heating-responsive SME and water-responsive SME in a few different types of polyurethanes and their composites will be reported. The fundamentals behind both effects will be discussed. Typical applications utilizing these effects either individually or in a combined manner will be presented.


FO-8.3:L03  Gold@pNIPAM Nanoparticles as Surface-enhanced Resonance Raman Spectroscopy (SERRS) Tags for Cell Differentiation
G. BODELÓN, V. MONTES-GARCÍA, C. FERNÁNDEZ-LÓPEZ, I. PASTORIZA-SANTOS, L.M. LIZ-MARZÁN, J. PÉREZ-JUSTE, University of Vigo, Dept. of Physical Chemistry, Vigo, Spain

A rapid surface-enhanced resonance Raman spectroscopy (SERRS) method has been developed for the detection and differentiated of growth factor receptors (GFR) on cells. SERRS tag labels were prepared by conjugating polyisopropylamide (pNIPAM) coated gold nanoparticles gold nanoparticles with commercial antibodies and dye molecules. After incubation with the immunogold labels, cell lines that over express GFR could easily be measured and differentiated by Raman spectroscopy. The immunogold were prepared by coating gold nanoparticles with a porous thermoresponsive polymer shell (pNIPAM) which allows the diffusion of the dye molecules (Astra blue, Nile Blue A and Malachite green), followed by coating with polyacrylic acid through the layer by layer technique. Finally, the SERRS tags were bioconjugated with the antibodies. Raman maps were collected across fixed and labelled cells lines, and the maps were used to determine specificities and organism coverages. The research presented here demonstrates the feasibility of utilizing SERRS labelling for sensitive differentiation strategies.


FO-8.3:L04  Glycopolymer Coated Gold Nanoparticle via RAFT Polymerization for Biosensing
Y. MIURA, Kyushu University, Fukuoka, Japan

Glycopolymers of polyacrylamide derivatives with mannose were prepared via the living radical　polymerization of RAFT reagent. The polymers obtained showed narrow polydispersities. The polymer terminal group was reduced to a thiol, and the resulting polymers were mixed with gold nanoparticles to prepare glycopolymer-substituted gold nanoparticles. The mannose density was adjusted by varying the copolymer preparation and the glycopolymer-polyacrylamide mixture. The colloidal stability of the polymer-coated gold nanoparticles is dependent on the mannose density. The molecular recognition abilities of the polymer were investigated using UV-vis spectroscopy. The polymer-coated nanoparticles showed strong protein recognition abilities because of multivalent binding effects. Polymers with high mannose densities showed stronger recognition abilities. An immunochromatographic assay was performed using the polymer-coated nanoparticles. The color was detected from the gold nanoparticles in the nanoparticle systems with strong molecular recognition and good colloid stability.


FO-8.3:L05  Thermally-induced Reversible Shape-Memory Effect of Hybrid Nanocomposites Under Constant Stress
M.Y. RAZZAQ, M. BEHL, A. LENDLEIN, Institute of Biomaterial Science, Helmholtz-Zentrum Geesthacht, Teltow,  Germany 

Here, we report on the reversible shape-memory effect of hybrid nanocomposites (H-NCs) based on oligo(ω-pentadecalactone) (OPDL) and covalently integrated magnetite nanoparticles (MNP, Ø = 10±1 nm) under constant stress conditions. The covalent integration of MNP avoids the aggregation and sedimentation of the magnetic particles during network synthesis. H-NCs with OPDL coated MNP (MNP@OPDL), which acted as additional crosslinking agents, were synthesized by cocondensation of hydroxy terminated MNP@OPDL and a three arm OPDL-macrotriol (³AOPDL, M_n = 3300 g∙mol^-1) with an aliphatic diisocyanate. The shape-memory properties of the H-NCs were quantified after a one step programming procedure in cyclic thermomechanical experiments, in which the stress was held constant during cyclic temperature variation. Here, nanocomposites showed crystallization induced elongation (CIE) and melting-induced contraction (MIC). A restraining effect of the MNP netpoints on the chain mobility, which resulted in a decreased CIE with increasing MNP content was observed. This enables SMPs, in which the extent of elongation or contraction caused by temperature change under stress can be controlled by the MNP content.
References
[1] R. Mohr et al., Proc. Natl. Acad. Sci. USA 2006, 103, 3540.
[2] M.Y. Razzaq et al.,  Adv. Mater. 2013, 25, 5730.
[3] M.Y. Razzaq et al., Mater. Res. Soc. Symp. Proc. 2009, 1140. 185.

 
Session FO-8.4 - Biomedical Applications Based on Degradable, Stimuli-responsive Polymers

FO-8.4:IL01  Thermoresponsive Nanonets for Nano- to Micro-scale Delivery of Therapeutics
G. AMEER, Institute for BioNanotechnology in Medicine, Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA

The controlled or smart release of small compounds, protein, and cells is a desirable goal for the treatment of disease, regenerative medicine, and wound healing applications. The delivery vehicle must be easy to use, not cause additional damage or trauma to tissue, and ideally be able to release multiple therapeutics of a wide rage of sizes to maximize flexibility. We developed a novel degradable non-toxic thermo-responsive biomaterial platform based on branched oligomers referred to as nanonets.  Depending on concentration, nanonets can form nanoparticles or a macroscopic elastic hydrogel with hierarchical nanoscale and microscale features. Nanonets are capable of effectively entrapping and slowly releasing bioactive proteins or a transgene product, and allow the long-term high viability and proliferation of cells within their network. Applications of nanonets in tissue engineering and wound healing will be discussed.


FO-8.4:IL02  Aliphatic Poly(carbonate)s as Versatile Materials for Tissue Engineering
I.A. BARKER¹, V.X. TRUONG¹, S. TEMPELAAR¹, L. MESPOUILLE², M. TAN², P. DUBOIS², A.P. DOVE¹, ¹Department of Chemistry, University of Warwick, Coventry, UK; ²Materials Research Institute, Center of Innovation and Research in Materials and Polymers (CIRMAP), Laboratory of Polymeric and Composite Materials, University of Mons, Mons, Belgium

Aliphatic poly(carbonate)s are gaining increasing attention over the last decade owing to their biodegradability, non-toxicity and in vivo bioresorbability. These properties, in turn, make them ideal for biomedical applications. Most notably, the synthetic versatility of these scaffolds allows for a wide range of materials to be targeted, in turn allowing the careful manipulation of polymer and materials properties.
One of our foci in this area has been the development of aliphatic poly(carbonate)s bearing an allyl-side chain. Such reactive functionality is ideal for the application of radical thiol-ene functionalization chemistries. To this end, we report the synthesis of materials with a range of properties as well as demonstrate their utility to form responsive hydrogel materials and 3D tissue engineering scaffolds.


FO-8.4:L03  Adhesive, Degradable Catecholamine Biopolymers as Hemostat, Gene Vector, and Encapsulation Agent
HAESHIN LEE, Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea

Catecholamine polymers are emerging biopolymers for material-independent adhesive properties. Well-known examples are poly(dopamine), pDA (Science 2007, 318, 426) and poly(norepinephrine), pNOR, (Angew. Chemie. Int. Ed. 2013, 52, 9187). They are formed and subsequently used by in situ polymerization from the corresponding catecholamine monomers of dopamine or norepinephrine. They exhibited excellent in vivo compatibility and biodegradability. Other types of catecholamine polymers are prepared by chemical conjugation of catechol along the backbone of cationic polymers such as chitosan or poly(ethylenimine). They demonstrated excellent adhesive properties but also exhibited additional useful functions in a variety of biomedical applications. For example, the surface coating of poly(ethylenimine)-catechol onto adeno-associate virus generated sticky virus for local gene delivery (Angew. Chemie. Int. Ed. 2012, 51, 5598). Also, catechol conjugation to chitosan increased water solubility of chitosan (60 mg/mL at pH = 7). Before the catechol conjugation, the chitosan is completely water insoluble at neutral pH. This favorable property change of the chitosan-catechol conjugate opens new opportunities to be applied in various biomedical applications such as hemostatic agents.


FO-8.4:L04  Biodegradable Coating Loaded with Cepholexin on Magnesium Alloy for Biomedical Implants
A. ZOMORODIAN¹, C. SANTOS^{1, 2}, M.J. CARMEZIM^{1, 2}, T. MOURA E SILVA^{1, 3}, J.C.S. FERNANDES¹, M.F. MONTEMOR¹, ¹ICEMS/DEQB, Instituto Superior Técnico, Technical University of Lisbon, Av. RoviscoPais, Lisboa, Portugal; ²Instituto Politécnico de Setúbal, DEM, ESTSetúbal , Portugal; ³Instituto Superior de Engenharia de Lisboa, Dep. Mech. Engineering, DEM, Lisboa, Portugal

The high susceptibility of magnesium alloys to corrosion is the main limitation regarding its use in biomedical applications as resorbable implants. In this study, a new approach was developed to control the corrosion rate of Mg alloys. Thus, a novel biocompatible polymeric coating modified with cepholexin, working as antibiotic and nano hydroxyapatite particles for enhanced biocompatibility, is applied on AZ31 magnesium alloy. The corrosion behavior of the coated samples is studied in Hank's solution by electrochemical impedance spectroscopy (EIS). To evaluate the stability of the cepholexin in the coating, Raman spectroscopy analyses will be performed. The release of cepholexin is studied by ultraviolet UV spectroscopy in Hank´s solution in order to assess its release rate.
The results revealed that the biocompatible coating controls the corrosion rate, while the presence of additives enhances the biocompatible response.
The chemical composition and the surface morphology of the coated samples, before and after the corrosion tests were evaluated by energy dispersive x-ray analysis (EXD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).


FO-8.4:L05  Microparticles from Photocrosslinked Polyesters
F. FRIESS^{1, 2}, A. LENDLEIN^{1, 2}, C. WISCHKE¹, ¹Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow, Germany; ²Institute of Chemistry, University of Potsdam, Potsdam, Germany

Photocrosslinking of functionalized telechelics in the melt has evolved to a versatile method to prepare a broad variety of polymer networks with adjustable properties and functions. Such networks are evaluated, e.g., as degradable biomaterial for smart implants^[1]. While non-crosslinked microparticles (MP) of poly(ɛ-caprolactone) are investigated and used for controlled drug delivery, low attention has been paid to the preparation and use of crosslinked MP.
Here, the synthesis of individual, spherical MP with defined properties was evaluated in an integrated process of microparticle formation and network synthesis. MP were prepared by oil-in-water emulsification of oligo(ε-caprolactone) dimethacrylate in organic solvent as oil phase. Upon exposure to UV irradiation, polymerization of methacrylate as functional moiety was induced. The MP had smooth surfaces and preserved their integrity after solvent exposure. In the future, these particles will be investigated for drug delivery.
[1] Kelch et al Biomacromolecules 2007, 8, 1018-1027
 

FO-8.4:IL06  Multifunctional Gene Nanoparticles to Mediate Proliferation and Migration of Human Vascular Endothelial Cells
YAKAI FENG^{1, 2, 3}, CHANGCAN SHI¹, QIAN LI¹, JING YANG¹, JUAN LV¹, MUSAMMIR KHAN¹, HAIXIA WANG¹, XIANGKUI REN¹, WENCHENG ZHANG⁴, ¹School of Chemical Engineering and Technology, Tianjin University, Tianjin, China; ²Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin, China; ³Tianjin University-Helmholtz-Zentrum Geesthacht, Joint Laboratory for Biomaterials and Regenerative Medicine, Tianjin, China; ⁴Graduate School of Tianjin Medical University, Tianjin, China; ⁵Department of Physiology and Pathophysiology, Logistics University of Chinese People’s Armed Police Force, Tianjin, China

Herein, we developed a novel biodegradable targeting gene carrier, i.e. multifunctional gene nanoparticles, for rapid endothelialization of endothelial cells (ECs) in vitro. A series of triblock amphiphilic copolymers, methoxy-poly(ethylene glycol)-block-poly(3(S)-methyl-2,5-morpholinedione-co-glycolide)-graft-polyethyleneimine (mPEG-b-P(MMD-co-GA)-g-PEI) with different 3(S)-methyl-2,5-morpholinedione and glycolide content were synthesized and linked with targeting peptides. Nanoparticles (NPs) were obtained via self-assembly of these copolymers. The hydrophobic core composed of P(MMD-co-GA) segments provide crosslinking points for numbers of PEG and short PEI chains to form a high hydrophilic and positive charged corona/shell of NPs. Using these NPs, potential genes (VEGF gene, ZNF580 gene) for rapid endothelialization were efficiently transported into EA.hy926 cells. Because of hydrophilic PEG chains and low molecular weight PEI in the triblock copolymers, the cytotoxicity of these NPs and their complexes with pEGFP-ZNF580 was decreased significantly. The transfection efficacy of NPs/pEGFP-ZNF580 complexes was as high as Lipofectamine^TM 2000 reagent to EA.hy926 cells in vitro. The proliferation and migration of EA.hy926 cells were improved greatly by the expression of pEGFP-ZNF580 after 60 hours. Our results indicated that the mPEG-b-P(MMD-co-GA)-g-PEI based NPs could be a suitable non-viral gene carrier for ZNF580 gene to enhance rapid endothelialization.


FO-8.4:L07  Assessment of Biodegradable Materials for Next Generation of Artificial Muscles
L.D. CHAMBERS, J. WINFIELD, I. IEROPOULOS, J. ROSSITER, Bristol Robotics Laboratory, University of Bristol, Bristol, UK; Bristol Robotics Laboratory, University of the West of England, Bristol, UK

New biodegradable materials for artificial muscles and soft actuators are required for biomedical and soft robotic applications. Here we present an investigation into the biodegradability and electroactive characteristics of a series of off-the-shelf biodegradable materials. Eight materials were examined: cellulose, collagen, two forms of natural rubber latex (NRL), chewing gum, paper, starch bio-plastic and polycaprolactone. Samples of each were buried in an outdoor compost heap at 30cm depth (1.5-20 °C) and degradation assessed every two weeks. Laboratory evaluation of the materials as actuators as well as ion exchange membranes within microbial fuel cells highlighted the NRL-glove, NRL-prophylactic, and collagen derivatives as having the greatest potential for biodegradable biomedical and soft robotic applications. For these three materials, greater than 90% biodegradation occurred in the compost heap after 285, 241, 18 days respectively. In response to electrical stimulus, the NRL materials acted as high voltage dielectric elastomer actuators and the collagen derivatives acted as low voltage ionic actuators. This assessment of the electroactivity and biodegradation characteristics of natural polymers provides a unique perspective on these important multi-functional materials.


FO-8.4:L08  Bicompatibility of a Degradable Poly[(L-lactide)-co-glycolide] Network
S. BRAUNE, S. DIETZE, T. ROCH, A. KRÜGER, S. BAUDIS, M. BEHL, K. KRATZ, F. JUNG, A. LENDLEIN, Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow, Germany

Biodegradable polymers are promising alternatives for permanent intracoronary implant materials. While providing short-term functionality/support, subsequent degradation processes allow an adequate regeneration of the surrounding tissue. Here, we study an amorphous poly[(L-lactide)-co-glycolide] (cPLGA) network, prepared from a star-shaped macrotrimethacrylate, as candidate polymer for the application as biodegradable stent material. Ethylene oxide sterilized PLGA exhibit smooth and hydrophobic surface properties as well as a Young´s modulus in the GPa range. Biocompatibility studies revealed an endotoxin load below FDA limits and cytocompatibility according to ISO 10993-5. Immunocompatibility was confirmed by analysis of the complement activation, oxidative burst and whole blood cytokine secretion. Protein adsorption and hemocompatibility analysis were carried out with fresh human blood and revealed a reduced amount of adherent thrombocytes and plasma fibrinogen on the PLGA surface, compared to the thrombogenic reference. In vitro bio-, immuno- and hemocompatibility of the PLGA network was approved and confirms it as candidate polymer for the application as degradable stent material. Further in vitro studies will focus the interaction of PLGA with cells of the human vasculature.


FO-8.4:L09  Oligotetrahydrofurane Based Shape-memory Hydrogels
M. BALK^{1, 2}, M. BEHL^{1, 2}, U. NÖCHEL¹, A. LENDLEIN^{1, 2, 3}, ¹Institute of Biomaterial Science, Helmholtz-Zentrum Geesthacht, Teltow, Germany; ²Tianjin University - Helmholtz-Zentrum Geesthacht, Joint Laboratory for Biomaterials and Regenerative Medicine; ³Berlin-Brandenburg Center for Regenerative Therapies (BCRT), Teltow, Germany 

Hydrophilic polymer networks having elastic properties similar to those of tissue combined with a thermally-induced shape-memory effect (SME) might be interesting candidates for biomedical application. However, the incorporation of short aliphatic side chains as switching domains resulted in a temperature dependent swelling and a change in elastic properties about three orders of magnitude.^[1]
Here we describe the development of shape-memory hydrogels based on oligomeric side chains obtained by monofunctionalization of oligotetrahydrofurane (OTHF) (M_n = 7400 g·mol^-1, T_m = 31 °C) with 2isocyanato ethylmethacrylate (IEMA). Hydrogels with OTHF-IEMA as switching segment, N-vinylpyrrolidone as swelling segment, and oligo(ethylene glycol)divinylether (OEGDVE, M_n = 250 g·mol^-1) as crosslinker were synthesized by radical in-situ copolymerization with AIBN as initiator. The resulting hydrophilic networks provided switching temperatures below body temperature, an almost temperature independent swelling capability as well as a change in elastic properties about one order of magnitude. In addition, the shape-memory properties were determined as a function of the OTHF wt%.
[1] Y. Osada, H. Okuzaki, H. Hori, Nature 1992, 355, 242.

 
Session FO-8.5 - Smart, Swollen Systems for Biomedical Applications

FO-8.5:IL01  Self-oscillating Gel as Novel Biomimetic Materials
R. YOSHIDA, Department of Materials Engineering, School of Engineering, The University of Tokyo, Japan

We have been studying polymer gels with an autonomous self-oscillating function, since firstly reported in 1996. We succeeded in developing novel self-oscillating polymers and gels by utilizing the oscillating reaction, called the Belousov-Zhabotinsky (BZ) reaction. The polymer gel undergoes spontaneous cyclic swelling-deswelling changes or soluble-insoluble changes (in the case of uncrosslinked polymer) without any on-off switching of external stimuli. Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems, such as biomimetic actuators, mass transport systems and functional fluids. For example, it was demonstrated that an object was autonomously transported in the tubular self-oscillating gel by the peristaltic pumping motion similar to an intestine. Further, it is possible to create a new dynamic interface by immobilizing the self-oscillating polymer on a substrate as polymer brushes. Besides, autonomous viscosity oscillation via metallo-supramolecular chemistry, self-oscillation of a synthetic block copolymer between unimer and micellar structures, etc. were realized. Recently, novel comb-type self-oscillating gels were designed. Such recent progress on the gel will be introduced.


FO-8.5:IL02  Functional Thermoresponsive Nanogels for Biomedical Applications
M. CALDERON, Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany

Stimuli-sensitive nanogels can shrink or swell rapidly by expelling or absorbing water in response to external stimuli such as temperature, pH, electrical, and magnetic fields. The combination of nanogel properties and thermo-responsiveness generates promising candidates for the development of smart nanocarrier systems. Their potential properties can be influenced by temperature changes with high responsiveness, reveal high loading capacity, can improve drug stability, and thus can be used for stimuli-controlled drug release. Our hypothesis treats the preparation of thermoresponsive glycerol-based nanogels and the investigation of their phase behavior with respect to their potential biomedical applications. Initial focus was given to fabricate nanogels with size control over the range of 50 and 200 nm and narrow size distributions. Preliminary results about their low cytotoxicity, their capability to penetrate cell membranes, and their potential to delivery and release bioactives upon external triggers like temperature and light will be presented.


Session FO-8.6 - Smart Polymers in Biomedical Applications

FO-8.6:IL01  Responsive Nanomaterials and Anti-inflammatory Therapies
N. TIRELLI, School of Medicine/Institute of Inflammation and Repair, and School of Materials. University of Manchester, Stopford building, Manchester, UK

Inflammatory pathologies are a very heterogeneous set of biomedical phenomena that include scarring, arthritis, asthma, atherosclerosis, diabetes, several neurodegenerative diseases, reactions to infection agents, to injury or to foreign tissues (transplants), fibrosis (liver, kidneys), dermatitis, inflammatory bowel diseases (Chron’s, colitis, etc.). The increase both in the life span and in the levels of stress associated to modern life in developed countries has caused a dramatic increase in the incidence of inflammatory diseases.
Inflammatory pathologies are not only a very disparate set of diseases; they can be originated by a variety of causes, e.g. infection, mechanical damage, auto-immune reactions, degenerative diseases, and can have a variety of symptoms, e.g. affecting specific tissues or having systemic (whole body) consequences, and generally involving different cell types.
To complicate this picture, inflammation is a physiological response, therefore most anti-inflammatory therapies are inherently interfering with normal biological processes, i.e. they generally significant and undesired side effects. Therefore, it would be very advantageous to target the action of an anti-inflammatory principle only to the site of inflammation.
One of the very few points that can distinguish a localized inflammation is the extracellular oxidation potential. The upregulation of the production of oxidants (“free radicals”: Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS)) in phagocytes is indeed an ubiquitous feature of inflamed tissues. Our research focuses on the development of oxidation-sensitive structures that are able to respond to this increase in oxidation potential.
Specifically, the talk will follow the development of organic polymer structures (polysulfides) from the details of their chemical synthesis through controlled polymerisation techniques to their processing in form of colloidal/nano materials, e.g. cross-linked nanoparticles or monomolecular micelles. Specific attention will be paid to the preparation of block copolymeric and branched structures.
Polysulfides show an oxidation-responsive but also oxidant-selective behaviour; although substantially insensitive to superoxide, they are oxidized to polysulfoxides by hydrogen peroxide while are depolymerized by hypochlorite. The details of the oxidative response of these nanomaterials will be discussed.


FO-8.6:IL03  Reactions at the Interface of Droplets: A Molecular "Screw Clamp" for the Formation of Smart Nanocapsules for Biomedical Applications
K. LANDFESTER, F.R. WURM, Max Planck Institute for Polymer Research, Mainz, Germany

130 years after Schotten and Baumann, reactions at the liquid-liquid interface still hold a great potential, especially as convenient and versatile route for the preparation of (nano)materials, which are not accessible by any other technique. We are investigating the polymerization at the interface between hydrophilic and hydrophobic liquids, mainly in (mini)emulsions. At the droplet interface, monomers provided from either phase meet, and polymerize to generate a polymer, which is insoluble in both phases and thus forms a shell surrounding a liquid core. The liquid core can be water or any other hydrophilic organic solvent, dispersed in an inert organic continuous phase. Typically, polyaddition reactions, as the generation of polyurethanes from di- or polyols and diisocyanates, or more recently bio-orthogonal polyadditions such as alkyne-azide "click" reactions or polycondensations, were performed in this manner. Within this field of research we are combining classical polymerization strategies with novel demands: biocompatibility, drug delivery, sustainability, and self-healing properties.
The molecular "screw clamp" is generated at the interface forcing both reaction partners to react. This allows us to perform reactions that cannot be performed in homogeneous solution.


FO-8.6:IL04  Chemical Cross-linking and Mechanical Properties of Thermosensitive Tissue Adhesive Hydrogels
D.G. BARRETT, G. BUSHNELL, P.B. MESSERSMITH, Northwestern University, Evanston, IL, USA

Most synthetic polymer hydrogel tissue adhesives and sealants swell considerably in physiologic conditions, which can result in mechanical weakening and adverse medical complications. In this talk we will describe the synthesis and characterization of mechanically tough zero- or negative-swelling mussel-inspired surgical adhesives based on catechol-modified thermoresponsive block copolymers. The formation, swelling, bulk mechanical, and tissue adhesive properties of the resulting thermosensitive gels were characterized. Catechol oxidation at or below room temperature rapidly resulted in a chemically cross-linked network, with subsequent warming to physiological temperature inducing a thermal hydrophobic transition in the block copolymer and providing a mechanism for volumetric reduction and mechanical toughening. The described approach can be easily adapted for other thermally sensitive block copolymers and cross-linking strategies, representing a general approach that can be employed to control swelling and enhance mechanical properties of polymer hydrogels used in a medical context.
 
 
Poster Presentations

FO-8:P01  Photo-responsive Soft Actuators Based on Spiropyran Functionalised Hydrogels
A. DUNNE, L. FLOREA, D. DIAMOND, INSIGHT, National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin, Ireland

Hydrogels are a class of polymeric materials, which swell upon hydration. Hydrogels have been used in many areas such as microfluidic systems where they have the function of pumps or valves [1]. Incorporation of photochromic units in hydrogel materials offers new possibilities for the production of photo-responsive soft actuators [2].
Spiropyrans are one of the most popular classes of photochromic compounds [3]. In acidic environments, the spiropyran gets protonated to form the hydrophilic protonated merocyanine (MCH+) that can be reversed back to the closed hydrophobic spiropyran (SP) by irradiation with white light.
Here we demonstrate that the size and volume of a hydrogel comprising a copolymer of acrylated spiropyran can be reduced when exposed to white light irradiation. This causes the gel to shrink and water is expelled. Different ratios of the SP derivative were investigated in order to achieve increased degree of shrinking and improved kinetics. Finally, the newly obtained photo-actuators were polymerized "in situ" in microfluidic channels to obtain photo-actuated microfluidic valves suitable for biomedical applications.
[1] D. Kim, D.J. Beebe, Lab Chip, 2007, 7, 193-198.
[2] S. Sugiura et al., Sens.Act.A, 2007, 140, 176-184.
[3] L. Florea et al., Macromol. Mater. Eng, 2012, 297, 11.


FO-8:P02  Effect of Titanium Dioxide Nanoparticles on Mechanical and Thermal Properties of Poly(Lactic Acid) and Poly(Butylene Succinate) Blends
A. BUASRI, G. BURANASING, R. PIEMJAISWANG, S. YOUSATIT, V. LORYUENYONG, Department of Materials Science and Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakhon Pathom, Thailand

Poly(lactic acid) (PLA) blended with poly(butylene succinate) (PBS) were prepared by using an internal melt mixer and an injection molding machine at various contents of PBS from 0-10 wt%. The surface of titanium dioxide (TiO2) nanoparticles was treated using aminopropyl trimethoxy silane (ATS) in order to disperse them into the biopolymer blends. The mechanical and thermal properties of PLA/PBS/TiO2 nanocomposites were investigated over a range of filler content 0-10 wt%. All samples with a wide range of TiO2 addition exhibit translucency. The surface morphology showed that the addition of PBS at 10 wt% was miscible with PLA while the other contents of PBS exhibited phase separation in the blends. Additionally, a uniform dispersion of filler in the matrix existed when the nanoparticles content was less than 5 wt%. The surface treated nanoparticles played an important role in the mechanical and thermal properties of the nanocomposites because of their well dispersion and strong interfacial interaction between the nanoparticles and the PLA/PBS matrix.


FO-8:P07  Tannic Acid, as a Plant-inspired Molecular 'Stapler', for Degradable DNA Hydrogels
M. SHIN, Graduate School of Nanoscience & Technology (WCU), KAIST, Daejeon, Korea; H. LEE, Graduate School of Nanoscience & Technology (WCU) and Department of Chemistry, KAIST, Daejeon, Korea

Degradable hydrogels have been designed by inducing (i) chemical crosslinking and (ii) physical association between biodegradable polymers. In the case of the hydrogel formed by chemical crosslinking, coupling agents and organic solvents often cause toxicity for further uses. For physically formed hydrogels, it is difficult to control degradability and to use various types of polymers because of a limited set of associable polymers. Among them, DNA can be an excellent programmable polymer that can form physical hydrogels in which specific A-T and G-C base pairs are used. Here, we demonstrate a completely new concept to form DNA hydrogel, and the key idea is to use a 'molecular stapler' to physically link between DNA chains. The molecular stapler is tannic acid (TA), a plant-derived polyphenol, and the degradable DNA hydrogel was simply prepared by self-interaction between TA and DNA. Furthermore, we demonstrated the self-interaction mechanism and DNA structure in TA/DNA complexes. It is true that the hydrogel is valuable for gene therapy because DNA is released from the hydrogel by the auto-hydrolysis of TA. These findings could be very useful for the development of small molecules crosslinked gene delivery systems with better performance in vitro and in vivo.


FO-8:P08  Multi-material Swollen Polymeric Films with Biocidal Properties
L.G. KOLZUNOVA, Institute of Chemistry, FEB RAS; Far Eastern Federal University, Vladivostok, Russia

Recent studies have demonstrated high scientific and practical value of the electropolymerization method. The electrochemical method of producing novel polymer materials has real prospects of finding the place among the leading ones in this field of science and technology. Electropolymerization can be successfully used in the development of new materials based on polymethylolakrylamide with biocidal and other therapeutic properties. The method of producing a composite films comprising implanting particles with specific properties to the polymer matrix was investigated. Electropolymerization conditions provide polymerization process near the electrode and capture these particles in a polymer film directly during the electrolysis. As a result, a composite film is formed on the electrode. The advantage of the method is its one-step process and a high adhesion to the metal surface. The introduction of drugs into the polymethylolakrylamide matrix allows to obtain water-swellable film with the required antiseptic, analgesic, thrombus resistance, anti-inflammatory and other medicinal properties. Due to the fact that such films exhibit biocompatibility, swellability, porosity and semipermeable membrane properties, such films may be used for the manufacture of implants.


FO-8:P09  Stimuli-controlled Movement of Droplets and Polymeric "Vehicles"
W. FRANCIS, L. FLOREA, D. DIAMOND, INSIGHT, National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin, Ireland

Stimuli-controlled movement of droplets or polymeric "vehicles" offers new and interesting possibilities in the area of biomedical applications, including cargo transport and drug delivery to target locations.
The motion of the "vehicle" is controlled by the release of surfactant type molecules concealed inside the "vehicle" (droplet, polymeric bead) only upon external stimulation (change in pH, photo- or electro- stimulus)[1,2]. Once released, the surfactant type molecules causes a local drop in the surface tension of the solution which in turn triggers the movement of the "vehicle" up the surface tension gradient [2].
In this work, "vehicles" are designed to move in open microfluidic channels based on the release of surfactant molecules upon electro- and photo- stimulation. The external stimulation alters the pH of the medium, which in turn leads to an increase of the solubility of the surfactant molecule in the aqueous solution.
This type of triggering of surfactant release using external stimuli aims to develop new approaches for controlling "vehicle" transport in microfluidics as well as to generate synthetic motors able to mimic biological systems.
[1] L. Florea et al., MicroTAS 2013, Freiburg, Germany, 2013.
[2] I. Lagzi et al., J. Am. Chem. Soc., 2010, 132, 1198.


FO-8:P10  Increased Stability of Polyphenol-tethered Alginate Hydrogels
SANG HYEON HONG¹, J.H. RYU², H. LEE¹, ¹Chemistry Department, KAIST, Daejeon, Republic of Korea; ²Program in Nanoscience & Technology, KAIST, Republic of Korea

Calcium-alginate hydrogels have been extensively utilized as scaffolding materials in tissue regeneration and drug delivery. However, the major drawback of the calcium-alginate gels is the rapid dissolution of the alginate polymers caused by the loss of the ionic interaction between Ca2+ and COO-. Methods to overcome the dissolution of alginate hydrogel are achieved mostly by additional cationic polymer coating on surfaces of the hydrogels. Herein, we demonstrate that the additional coating by cationic polymers is not necessary to maintain the original physicochemical integrity of the hydrogels. When using polyphenol-tethered alginate as a backbone polymer to prepare calcium alginate hydrogel at pH 7.4, the tethered polyphenol undergoes relatively slow crosslinking, which well matches the kinetics of the calcium dissociation. Thus, the original physicochemical integrity of the hydrogel maintained even after the calcium dissociation. This novel method to prepare the alginate hydrogel may increase the potential utility in a variety of biomedical applications.


FO-8:P11  New Strategy to Fabricate Catalyst-mediated Hydrogel, in which the Catalyst is not Included in the Gel
EUNKYOUNG BYUN, H. LEE, Department of Chemistry, KAIST, Daejeon, Republic of Korea; J.H. Ryu, The Graduate School of Nanoscience ant Technology, KAIST, Daejeon, Republic of Korea

Hydrogels are an attractive biomaterial for use in tissue engineering and drug delivery. In formation of catalyst-mediated hydrogels, the most challenging problem has been the incorporation of the catalyst within the hydrogel. For the covalently crosslinked hydrogels, chemical catalysts such as copper(I), NaIO4, or FeCl3, or biological catalysts (e.g. enzymes) are unavoidably incorporated in the hydrogel. The catalysis encapsulation/incorporation has been a significant problem in acquiring Food and Drug Administration (FDA) permission for human trials. In this presentation, an entirely new method to form hydrogels, whose formation is triggered by a catalyst, but the resulting hydrogels are catalyst-free is introduced. The key mechanism relies on generating chemically active yet stable intermediate along the hydrogel polymer backbones. Later in time, the intermediate (organic radicals) forms covalent bonds that result in inter-polymer chain connection that becomes hydrogels. The catalyst is immobilized on surfaces so that it does not included within the resulting hydrogel.


FO-8:P12  Natural Polymers as Heat and Moisture Exchange Devices for Medical Applications
B. VAZQUEZ, A. NICOSIA, F. BELOSI, G. SANTACHIARA, Institute of Atmospheric Sciences and Climate (ISAC-CNR), Bologna, Italy; P. MONTICELLI, Pollution Srl, Budrio (Bo), Italy; M. SANDRI, E. SAVINI, A. TAMPIERI, Institute of Science and Technology for Ceramics (ISTEC-CNR), Faenza (RA), Italy

In the last decades, Heat and Moisture Exchange (HME) devices have been increasingly used for short-term use in anaesthesia and for long-duration use in intensive care units. These devices work as heat exchangers, accumulating the patient's expired heat and moisture and returning them to the patient during the inhalation phase. Porous matrices obtained through mineralization of self-assembling blends of natural polymers (e.g. chitosan, cellulose, gelatin, alginate) with hydroxyapatite (HA) dried through a controlled lyophilization process exhibit high open and interconnected porosity and water vapour intake characteristics which make them possible candidates for HME devices in the light of a "green economy" perspective. Preliminary results have been obtained with gelatine blended with chitosan and treated with two different cross-linking agents, genipin and 1,4-butanediol diglycidyl ether (BDDGE). Tests were conducted in continuous flow as well as in cyclic flow conditions with saturated and dried air. Results show fairly good water vapour retention. This work will present data obtained with different polymeric compositions and their comparison with accepted standards.
Acknowledgments
European Project: SMILEY, NMP.2012.1.4-2 FP7 SMALL-6-310637.


FO-8:P13  Star-shaped Oligo(Ethylene Glycols) Functionalized with Desaminotyrosine and Desamino Tyrosyl Tyrosine
K.K. JULICH-GRUNER, T. ROCH, A.T. NEFFE, A. LENDLEIN, C. LOEWENBERG, Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow, Germany

The functionalization of biopolymers or synthetic polymers with functional moieties inducing self-organization of the polymer chains is one approach to design multifunctional materials. Aromatic compounds e.g. desaminotyrosine (DAT) or desamino tyrosyl tyrosine (DATT) were previously used to functionalize gelatin and form physically crosslinked networks by π-π interactions and hydrogen bonds. In this study, star-shaped oligo(ethylene glycols) (sOEG) with defined molecular weights (Mn=5, 10, 20 kDa) as model systems were functionalized with DAT and DATT. The compounds were characterized by NMR, IR spectroscopy, and MALDI-ToF mass spectrometry and showed functionalization degrees of 53-85%. Aqueous polymer solutions (10 wt.%) were characterized by rheology, showing a decrease of storage modulus G` (0.01-0.1 Pa) and loss modulus G`` (0.2-11 Pa) compared to the unfunctionalized sOEGs (G` 0.15-0.3 Pa; G`` 0.2-0.4 Pa). Furthermore, these solutions showed lower surface tension than solutions of the starting materials. Due to the structure of the macromolecule with large hydrophilic chains and hydrophobic end groups, the polymers showed properties of a surfactant and could potentially be used for solubilizing hydrophobic drugs.
This work was financed by the BMBF (Poly4Bio (0315696A)).