This work investigates the cytocompatibility of several photoinitiating systems for potential cell encapsulation applications. Both UV and visible light initiating schemes were examined. The UV photoinitiators included 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651), 1-hydroxycyclohexyl phenyl ketone (Irgacure 184), 2-methyl-1-[4-(methylthio) phenyl]-2-(4-morpholinyl)-1-propanone (Irgacure 907), and 2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Darocur 2959). The visible light initiating systems included camphorquinone (CQ) with ethyl 4-N, N-dimethylaminobenzoate (4EDMAB) and triethanolamine (TEA) and the photosensitizer isopropyl thioxanthone. A cultured fibroblast cell line, NIH/3T3, was exposed to the photoinitiators at varying concentrations from 0.01% (w/w) to 0.1% (w/w) with and without the presence of initiating light. The results demonstrated that at low photoinitiator concentrations (6 0.01% (w/w)), all of the initiator molecules were cytocompatible with the exception of CQ, Irgac...

Cytocompatibility of UV and visible light photoinitiating systems on cultured NIH/3T3 fibroblasts in vitro

Photopolymerizable and degradable biomaterials are finding widespread application in the field of tissue engineering for the engineering of tissues such as bone, cartilage, and liver. The spatial and temporal control afforded by photoinitiated polymerizations has allowed for the development of injectable materials that can deliver cells and growth factors, as well as for the fabrication of scaffolding with complex structures. The materials developed for these applications range from entirely synthetic polymers (e.g., poly(ethylene glycol)) to purely natural polymers (e.g., hyaluronic acid) that are modified with photoreactive groups, with degradation based on the hydrolytic or enzymatic degradation of bonds in the polymer backbone or crosslinks. The degradation behavior also ranges from purely bulk to entirely surface degrading, based on the nature of the backbone chemistry and type of degradable units. The mechanical properties of these polymers are primarily based on factors such as the network crosslinking density and polymer concentration. As we better understand biological features necessary to control cellular behavior, smarter materials are being developed that can incorporate and mimic many of these factors.

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Review: photopolymerizable and degradable biomaterials for tissue engineering applications.

Novel poly(vinyl alcohols) (PVA) functionalized with pendant acetylene and azide groups were prepared by carbonyldiimidazole (CDI)-mediated couplings of the amines terminated with functional groups, 1-azido-2-aminoethane, propargylamine, or N-methylpropargylamine, to PVA. Low degrees (1−5%) of PVA modification were required in order to retain solubility in water. Azide-modified PVA and alkyne-modified PVA components were cross-linked by mixing of their solutions together with Cu(I) catalyst, a type of Huisgen's 1,3-dipolar azide−alkyne cycloaddition, recently defined as a powerful “click” chemistry. Reaction of the two different polymers results in a chemoselective coupling between alkynyl and azido functional groups with the multiple formation of triazole cross-links to give hydrogel formation. In another version the PVA-based hydrogels were obtained by cross-linking of alkyne-modified PVA with the telechelic bifunctional poly(ethylene glycol)−diazide cross-linker. The hydrogels prepared by these two met...

Poly(vinyl alcohol)-Based Hydrogels Formed by “Click Chemistry”

Nanoscale poly(vinyl alcohol) (PVA) fiber (100–500 nm) aggregates were prepared with an electrospinning technique. Additionally, a chemical crosslinking method was used to crosslink the nanoscale PVA fiber aggregates. Differential scanning calorimetry, wide-angle X-ray diffraction, and scanning electron microscopy techniques were employed to characterize the PVA fiber aggregates. The different crosslinking densities of the PVA fiber aggregates were obtained through the control of the weight percentage of glyoxal to PVA. The crosslinking densities due to heat treatment and chemical crosslinking were studied. The influence of heat treatment could be neglected in contrast to chemical crosslinking when the curing temperature was 120 °C. The primary factor that affected the crosslinking density was the volume of the chemical crosslinking agent. The results showed that the properly crosslinked PVA fiber aggregates had better antiwater solubility and mechanical properties than the noncrosslinked PVA fiber aggregates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1261–1268, 2002

Preparation and characterization of a nanoscale poly(vinyl alcohol) fiber aggregate produced by an electrospinning method

Characterization of hydrogels formed from acrylate modified poly(vinyl alcohol) macromers

Poly(vinyl alcohol) (PVA) was partially modified by polymer analogous reaction with acrylic and methacrylic acid and with 2-vinyl-4,4-dimethyl-azlactone to obtain water-soluble polymers with pendant (meth)acrylate and acrylamide groups. Aqueous solutions of these polymers were crosslinked by UV-irradiation within seconds to form transparent networks with potential for use in contact lenses. The water content of these hydrogels was studied as a function of polymer molecular weight, the acetate, (meth)acrylate, and methacrylamide contents and irradiation conditions. The hydrogels showed good mechanical properties, even at low crosslinker (<5 mol %) and high water contents (60–80%). The formation kinetics and stability of aggregates, investigated by combined GPC/light-scattering measurements of samples annealed and/or stored at different temperatures (−20 to 100°C), give insight into PVA secondary structures. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3603–3611, 1997

A. Muhlebach

Papers

New water-soluble photo crosslinkable polymers based on modified poly(vinyl alcohol)

Nelfilcon a, a new material for contact lenses