Biodegradable shape memory polymers functionalized with anti-biofouling interpenetrating polymer networks.

A novel type of shape memory polyurethane (SMPU) with high mechanical properties and biodegradability was constructed using a lactone copolymer (poly(ε-caprolactone-co-γ-butyrolactone), PCLBL), a diol- or triol-based chain extender (1,5-pentanediol, glycerol and 2-amino-2-hydroxymethyl-1,3-propanediol) and a diisocyanate cross-linker (1,6-hexamethylene diisocyanate). All types of SMPUs possessed high mechanical properties, and the shape recovery test indicated that the SMPU sheets prepared using a triol-chain extender with an amine group recovered completely the original shape at 80 °C. Moreover, the degradation products of the SMPUs were innoxious, which is an important property for use in the biomedical field. Furthermore, the SMPU sheets were interpenetrated with a zwitterionic polymer, poly(carboxymethyl betaine) (PCMB), using the interpenetrating polymer network (IPN) method to additionally introduce an anti-biofouling property. Water contact angle measurements of the surface of PCMB-introduced SMPU sheets showed a drastic reduction from 87° to approximately 30° due to the exposure of the PCMB chains from the SMPU sheets. These SMPU-IPN sheets suppressed significantly both protein adsorption and cell adhesion. Consequently, the PCLBL-PU-based SMPUs interpenetrated with PCMB are promising materials for biomedical devices because of their high mechanical, shape memory, biodegradable, and anti-biofouling properties. These materials are expected to be applied to biomaterials such as embolization materials for aneurysms and a novel type of membrane for postoperative adhesion prevention.

Advantages of anchoring growth factors to materials for neural stem/progenitor cell proliferation.

Biomaterials modified with proteins such as growth and trophic factors are known to precisely regulate various cell and tissue functions. However, the mechanisms for regulation with proteins anchored to a substrate have not been extensively studied. Although we previously evaluated specific signal transduction from epidermal growth factor (EGF) anchored to a substrate to neural stem/progenitor cells (NSPCs), the internalization of immobilized-EGF and the continuity of signaling transduction were not discussed in detail. This information is important to determine the value of growth factor-anchored biomaterials in the regulation of cells. Here, we tried to clarify the mechanisms underlying immobilized-growth factor in NSPC regulation using approaches from materials science and cell biology. In this evaluation, we used EGF chimeric protein (EGF-His) and NSPCs, and found that EGF anchored to a substrate facilitated continuous signal transduction in NSPCs attached to the substrate. In addition, the anchored-EGFs were finally internalized into cells only when the proteins formed a complex with their receptors on cell membranes detached from the substrate. Finally, we concluded that continuous signal transduction by anchoring to the substrate and final internalization into cells with the detachment of anchored-proteins from a substrate are important events for efficient regulation of cell function.

Interleukin-10 chimeric protein to protect transplanted neural progenitor cells from immune responses.

The provision of adhesive scaffolding and protection from inflammatory responses are important for enhancing graft survival. We previously developed a functional hydrogel that significantly enhances the survival of cells transplanted into the midbrain striatum. Although graft survival reached approximately 40% using this hydrogel, the survival of transplanted cells required further enhancements because it ultimately produced a decrease in the number of transplanted cells. Therefore, we developed a hydrogel system that can locally prevent the inflammatory response. This hydrogel was modified by the addition of the interleukin 10 chimeric protein (IL10CP), which is selectively released from the hydrogel when triggered by an inflammatory response. This design protects transplanted cells from inflammatory response, while other host cells remain unaffected. The IL10 domains are selectively released from the hydrogel, which act locally on the immune cells to prevent the inflammatory response without the administration of an immune suppressor. The selective release of IL10 domains from the hydrogel and their activity to prevent immune responses were evaluated using various approaches. Moreover, the ability of the IL10CP-modified hydrogel to protect cells was investigated using an in vitro co-culture with activated microglia. The IL10 incorporated into the hydrogel was selectively released by the activity of matrix-metalloproteinase 9 (MMP9), and the neural progenitor cells encapsulated in the IL10CP-immobilized hydrogel were protected from activated microglia by the release of IL10s from the hydrogel by the MMP9, produced by the activated microglia. These results show that the IL10CP-modified hydrogel will be useful as a biomaterial for improving the survival of transplanted cells.

Biodegradable microparticles for strictly regulating the release of neurotrophic factors.

A lot of research has been carried out in the last decade to find a cure for neurodegenerative diseases especially Parkinson's disease but to little avail. In this study we have demonstrated the use of poly(lactic-co-glycolic acid) (PLGA)/collagen biodegradable microparticles formed using water-in-oil-in-water (W/O/W) double emulsion method, as a neurotrophic factor delivery vehicle. The microparticles were encapsulated with glial cell-derived neurotrophic factor (GDNF) fused with collagen binding peptide (CBP) immobilized to the inner collagen phase. The novelty lies in the strict regulation of release of GDNF-CBP from the microparticles as compared to a burst release from standard microparticles. The microparticles were demonstrated to be non-cytotoxic till 300 µg/2 × 105 cells and revealed a maximum release of 250 ng GDNF-CBP/mg microparticles in 0.3% collagenase. Differentiation of neural progenitor cells (NPCs) into mature neurons was demonstrated by co-culturing microparticles with cells in a medium containing collagenase which enabled the release of encapsulated GDNF-CBP, signaling the differentiation of NPCs into microtubule-associated protein 2 (MAP2)-expressing neurons. The successful ability of these microparticles to deliver neurotrophic factors and allow differentiation of NPCs into mature neurons provides some scope in its use for the treatment of Parkinson's disease and other neurodegenerative diseases.