Track 12. Biomaterials 12.1. Biomaterials for Therapeutic Delivery $259

[4] A. Lendlein, H. Jiang, O. J~nger, R. Langer. Light-induced shape-memory polymers. Nature 2005; 434: 879-882.

4937 We, 12:00-12:15 (P31) Cell-surface interactions between rat Schwann cells and a biomimet ic surface prepared by plasma act ivat ion and subsequent vapor graf t ing process Y.-T. Yang, J.-D. Liao. Department ef Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan (ROC)

Repairing of injured peripheral nerve using tissue engineering method has been developed for a decade; there still exist several obstinate bottlenecks such as the regeneration gap limit, the healing ratio of nerve functions, etc. To view tissue regeneration at the cell level, cellular behaviors, e.g. cell growth and cellular metabolism, in a microenvironment are closely related to their attached surface. Based upon this consideration, surface modification on a biodegradable 2-D or 3-D scaffold has recently paid much attention for the purpose of providing a biomimetic microenvironment in favor of cells. In this study, we applied (1) an innovative low-temperature (i.e. below the glass transition temperature) microwave plasma system for surface activation on the poly(L-lactide) membranes instead of traditional destructive alkaline or thermal treatment, (2) an in-situ acrylic acid monomer vapor grafting process (i.e. a liquid-free method to graft with a particular functional group) on the surface-activated sample and (3) a covalently bonded method, without ex- posure to oxygen, to immobilize with laminin, RGD (arginine-glycine-aspartic acid) peptide and galectin-1/Ox on the functional group-grafted sample. These processes were thereafter anticipated to take the advantage of creating a microenvironment for the affinity of Schwann cells and for the promotion of neural regeneration. X-ray photoelectron spectroscopy and micro-Fourier transform infrared spectrometry were utilized for the analysis of surface chem- istry. Primary Schwann cells obtained from 7-day-old rats were cultured on the modified membranes, and cell viability was evaluated by MTT test while phenotypic observation of adhered cells was taken by scanning electron micro- scope. Continuous stiffness measurement using nano-indenter (MTS NANO XP) was also applied to characterize cellular nano-mechanical properties on different biomimetic surfaces. Overall, surface modification of biodegradable polymers can be achieved by plasma activation and subsequent vapor grafting process. The synergetic 2-D studies on the cell-surface interactions facilitate the understanding of the relationship between a biomimetic treatment on a biodegradable surface and cellular behavior of Schwann cells, moreover, the regeneration of peripheral nerves.

5295 We, 12:15-12:30 (P31) Electro-mechanical character isat ion of Chi tosan membrane for assistance in drug del ivery N.D. Sheba Rani, P. Subrata. School of Bioscience & Engg., Jadavpur University, Kolkata, India

In recent years transdermal controlled drug delivery through biomembrane has become a popular modality due to better patient compliance and lesser adverse effects over other conventional routes. Enhancement in drug delivery is possible using various physical and electrical enhancers. In order to optimize the use of enhancers, it is important to study the electro mechanical properties of polymer membrane [1]. Membranes cast from Chitosan (CS) obtained by N-deacetylation of chitin, have been found to be a very convenient vehicle for molecular delivery of drugs, proteins or genes [2]. To utilize various beneficial properties (anti fungal, antiviral, antibacterial) effectively, electrical and mechanical characteristics are essential. No such reliable data are available, which prompted us to take up this work. Method: Chitosan (CS) was blended with PolyVinylAIcohol (PVA) to prepare membranes with various ratios. The membranes were characterized for me- chanical strength, resistivity and dielectric constant; time constant (l/Z) using Maxwell's model (q=%e -'~t) keeping the strain constant at 40% of breaking strain. Results: The CS-PVA membrane gave two E values with E1=244.44±10.94 MPa & E2=14.63±1.02 MPa for 1:1 ratio. Gamma irradiation of 25 kGy, made it stiffer. The time constants were 42±2 and 54±3s; while resistivity was 7.85±0.14 and 14.67±0.37 ~2 m and dielectric constant measured at 100 Hz was 18.64±1.29 and 18.4±1.28; while for 1 KHz frequency it was 16.03±0.32 and 16.13±0.6 for 1:1 and 1:2, respectively. Conclusion: The membrane is a bilinear viscoelastic material with time constant above 42 secs. We conclude that compared to usual electrical insulators the membrane has a relatively high dielectric constant and dielectric strength [3]. These information would be useful for better design of Iontophore- sis [4], Electroporation [5], MEMS (MicroelectromechanicalSystem) [6] etc with chitosan. Acknowledgement: This project was funded by INMAS-DRDO, Delhi.

References [1] A.M.A.Nada, EgypUSolids 2005; 28: No.2. [2] L. Ilium, PharmRes. Sep 1998; 5(9): 1328-31. [3] J.R. Bobeck, Physiological Basis of Medical Practice 1973. [4] Guy RH. Iontophoresis: recent developments. JPharmPharmacol 1998; 50(4):

371-374. [5] Neumann E, Kakorin S, Toensing K, Principles of membrane electroporation

and transport of macromolecules. Methods in Molecul Medicine. Humana Press, Totowa, NJ. 2000; 1-35.

[6] Okino M, Mohri H. Effects of high-voltage electrical impulse and an anticancer drug on in vivo growing tumors. JpnJCancerRes. 1987; 78: 1319-1321.

7044 We, 14:00-14:30 (P34) Af f in i ty techno logy and wet chemistry in the design o f bioact ive implant surfaces H.P. Jennissen. Institut f~r Physiologische Chemie, Universit~t Duisburg- Essen, Universit~tsklinikum Essen, Germany

In designing a biologically active surface on a scaffold or implant the funda- mental knowledge of affinity technology plays a key role. Affinity technology is based on the principle of biological recognition between two binding partners. Biorecognition in itself is based on molecular recognition. A typical example is affinity chromatography. Molecular recognition is often equated with the lock- and-key principle introduced by Emil Fischer in 1894. Generally one imagines a three dimensional key and lock. However a scaffold or implant surface can also be pictured as a two-dimensional key carrying interaction sites on a binding-site lattice poised to react multivalently with the corresponding lock such as a cell or tissue [1]. Surfaces of this kind have been called juxtacrine surfaces [2]. In addition the slow release of chemotactically active molecules from the surface will attract tissue precursor cells from the surroundings to the juxtacrine surface. An example for such a system will be shown in the immobilization of bone morphogenetic protein 2 (BMP-2) on metal and hydroxyapatite surfaces. In recent years evidence has been presented that wet chemistry alone may modify a metal surface in such a way as to make it more histophilic (i.e. "tissue loving"). The result of such a wet chemistry step with chromosulfuric acid is an ultra-hydrophilic surface [3] with dynamic contact angles <10 °, absent hysteresis and a distinct nano-structure. Preliminary in vive experiments suggest an enhancement of bone growth in proximity to such surfaces. In a third application the ultrahydrophilic surface can be combined as a priming coat with the chemotactic-juxtacrine surface as the biocoat to a novel biomolecular active composite.

References [1] Jennissen H. P. Methods Mol. Biol. 2005; 305: 81-99. [2] Jennissen H. P. Ann. NY Acad. Sci. 2002; 961: 139-142. [3] Jennissen H. P. Macromol. Symp. 2005; 225: 43-69.

4056 We, 14:30-15:00 (P34) Potential o f l ip id-modif ied po lycat ions to t ransfer plasmid DNA into bone marrow stromal cells (BMSC) H. Uludag, V. Incani, E. Tunis, B. Acan, C. Olsen, C. Kucharski, A. Ghahary, A. Lavasanifar. Chemical & Material Engineering Department, Faculty ef Engineering, Univ. of Alberta, Alberta, Canada

Cationic polymers such as polyethylenimine (PEI) and poly-L-lysine (PLL) are extensively tested in vitro and in vive to deliver anionic plasmid DNA into cells. The cationic polymers condense the long, string-like DNA molecules into compact structures. This allows the passage of the DNA molecules through the primary barrier of the cells (plasma membrane), but the cationic polymers are not very efficient for DNA transfer and display significant toxicities on mammalian cells. This study was conducted to investigate the effect of a naturally-occurring lipid (palmitic acid) to enhance the ability of cationic polymers for DNA delivery into bone marrow stromal cells. These cells are commonly used in gene therapy protocols in clinics. Using constructs of poly-L-lysine and palmitic acid, we obtained polymers that were capable of condensing plasmid DNA effectively into 100-200 nm particles (as determined by Atomic Force Microscopy), and enhancing the delivery of plasmid DNA (-10-fold) into the cells (as determined by flow cytometry). Using a model gene (EGFP; Enhanced Green Fluorescent Protein), the designed polymers enabled improved expression of the EGFP gene in bone marrow stromal cells. The level of EGFP expression enabled by the designed biomaterials was comparable to the cells modified with an adenoviral vector carrying the EGFP gene. We conclude that the formulated biomaterials are superior to the currently used polymers, and provide a promising means to make clinical gene therapy a reality.