Membranes from Acrylonitrile-Based Polymers for Selective Cultivation of Human Keratinocytes

Thermoresponsive polyurethane/siloxane membrane for wound dressing and cell sheet transplantation: In-vitro and in-vivo studies

Polyurethane/siloxane based wound dressing for transferring fibroblast cell sheet to wounded skin and ability to provide an optimum condition for cellular activity at damaged tissue was prepared in this research. The dressing was made thermoresponsive, via the introduction of a poly(N-isopropyl acrylamide) copolymer into the backbone of dressing. The ability of membrane for adhesion, growth, and proliferation of fibroblast cells was improved via surface modification with gelatin. The optimized dressing exhibited appropriate tensile strength (4.5MPa) and elongation at break (80%) to protect wound against physical forces. Due to controlled equilibrium water absorption of about 89% and water vapor transmission rate of 2040g/m(2)day, the dressing could maintain the favorable moist environment over moderate to high exuding wounds. The grown cell sheet on dressing membrane could easily roll up from the surface just with lowering the temperature. The in vivo study of the wound dressed with cell loaded membrane confirmed the accelerated healing and production of tissue with complete re-epithelization, enhanced vascularization, and increased collagen deposition on the damaged area.

Nylon-3 polymers that enable selective culture of endothelial cells

Substrates that selectively encourage the growth of specific cell types are valuable for the engineering of complex tissues. Some cell-selective peptides have been identified from extracellular matrix proteins; these peptides have proven useful for biomaterials-based approaches to tissue repair or regeneration. However, there are very few examples of synthetic materials that display selectivity in supporting cell growth. We describe nylon-3 polymers that support in vitro culture of endothelial cells but do not support the culture of smooth muscle cells or fibroblasts. These materials may be promising for vascular biomaterials applications.

Influence of co-monomer ratio on the chemical properties and cytotoxicity of poly[acrylonitrile-co-(N-vinylpyrrolidone)] nanoparticles

PURPOSE

A system of nanoparticles with varying hydrophilicities may include promising biomaterial candidates as they offer various cellular uptake properties and a range of drug encapsulation efficacies, which would be advantageous in regenerative therapies. Therefore, a model system of nanoparticles with varying hydrophilicities was synthesized and assessed for its candidacy as a biomaterial.

METHODS

Here, acrylonitrile (AN) was copolymerized with N-vinylpyrrolidone (NVP) in a mini-emulsion to form a family of nanoparticles, thereby enabling the systematic variation of the copolymer hydrophilicity. The nanoparticles based on these copolymers were prepared and characterized using 1H-NMR, dynamic light scattering, differential scanning calorimetry, and thermal gravimetric analysis. Finally, the cytotoxicity of the nanoparticles was assessed by conducting indirect tests using L929 fibroblasts.

RESULTS

The nanoparticles showed well controlled NVP/AN molar ratios as determined by 1H NMR, well defined diameters ranging from approximately 100 nm to 200 nm, and increasing glass transition temperatures with increasing molar NVP content. Finally, L929 fibroblasts only slightly changed their morphology upon incubation with material eluates.

CONCLUSIONS

Poly[acrylonitrile-co-(N-vinylpyrrolidone)] nanoparticles with varying amounts of NVP were shown to be a promising model system for further biological assessment.

Creation of biofunctionalized micropatterns on poly(methyl methacrylate) by single-step phase separation method

In this study, the polymer thin films containing micropatterns and biological functionalities were created by one-step procedure. The adjustable compositions among poly(methyl methacrylate) (PMMA), solvents, nonsolvent, and additional macromolecules formed the polymer thin films with different diameters ranging from 5 to 37 μm. The influences of topographical and chemical cues were investigated by directly cultivating L-929 fibroblasts on the prepared samples. The results revealed the predominant effect of surface topography that the cell density of L-929 fibroblasts increased proportionally with the average diameter of microconcaves. The cell number raised significantly on the PMMA thin films containing type I collagen and dopamine, with or without microstructures. On the other hand, the addition of bovine serum albumin in PMMA limited the growth of cells. The surface chemical composition and cell responses were evaluated by electron spectroscopy for chemical analysis (ESCA), viability assay, and immunostaining, respectively. This work proposed a simple and effective approach to incorporate the biological functions and surface topography simultaneously onto surface of materials that provided further applications for biomedical materials.

Polyelectrolyte multilayers generated in a microfluidic device with pH gradients direct adhesion and movement of cells

In this study, multilayers from polyethylene imine, heparin and chitosan are prepared at three different pH values of 5, 7 and 9. Water contact angle and quartz microbalance measurements show that resulting multilayers differ in terms of wetting behaviour, layer mass and mechanical properties. The multilayer is then formed within a gradient generation microfluidic (μFL) device. Polyethylene imine or heparin solutions of pH 5 are introduced into one inlet and the same solutions but at pH 9 into another inlet of the μFL device. The pH gradient established during the multilayer formation can be visualized inside the microchamber by pH sensitive fluorophores and confocal laser scanning microscopy. From this setup it is expected that properties of multilayers displayed at distinct pH values can be realised in a gradient manner inside the μFL device. Behaviour of the osteoblast cell line MG-63 seeded and cultured on top of multilayers created inside the μFL device support this hypothesis. It is observed that more cells adhere and spread on multilayers build-up at the basic side of the μFL channel, while those cells on top of multilayers built at pH 5 are fewer and smaller. These results are consistent with the behaviour of MG-63 cells seeded on multilayers formed at discrete pH values. It is particularly interesting to see that cells start to migrate from multilayers built at pH 5 to those built at pH 9 during 6 h of culture. Overall, the presented multilayer formation setup applying pH gradients leads to surfaces that promote migration of cells.

pH-dependent modulation of fibroblast adhesion on multilayers composed of poly(ethylene imine) and heparin

Adhesion of tissue cells is a prerequisite for their growth and differentiation but prevents also apoptosis. Here the layer-by-layer technique (LbL) was used to design multilayer structures of poly(ethylene imine) (PEI) and heparin (HEP) on glass as model biomaterial to control the adhesion of primary human dermal fibroblasts. Distinct surface features like wettability, charge and lateral structures were controlled by changing the pH value of the HEP solution during multilayer assembly to acidic, neutral or alkaline values. While plain terminal layers were rather cytophobic, the pre-adsorption of serum or fibronectin (FN) caused a distinct change in cell morphology in dependence on the pH setup. The effect of serum was more prominent on PEI layers probably due to their positive surface charge, whereas the effect of FN was more pronounced on HEP terminated multilayers possibly due to its ability to bind FN specifically. Those layers which hampered cell adhesion also inhibited growth of human fibroblasts under serum conditions. Conversely, on layers where cell adhesion was increased also an elevated growth and, thus, metabolic activity was observed.

Multilayer coatings on biomaterials for control of MG-63 osteoblast adhesion and growth

Here, the layer-by-layer technique (LbL) was used to modify glass as model biomaterial with multilayers of chitosan and heparin to control the interaction with MG-63 osteoblast-like cells. Different pH values during multilayer formation were applied to control their physico-chemical properties. In the absence of adhesive proteins like plasma fibronectin (pFN) both plain layers were rather cytophobic. Hence, the preadsorption of pFN was used to enhance cell adhesion which was strongly dependent on pH. Comparing the adhesion promoting effects of pFN with an engineered repeat of the FN III fragment and collagen I which both lack a heparin binding domain it was found that multilayers could bind pFN specifically because only this protein was capable of promoting cell adhesion. Multilayer surfaces that inhibited MG-63 adhesion did also cause a decreased cell growth in the presence of serum, while an enhanced adhesion of cells was connected to an improved cell growth.