Synthesis and Photopolymerization of Tween 20 Methacrylate/N-vinyl-2-Pyrrolidone Blends

a r t i c l e i n f o Poly(oxyethylene 20 sorbitan) monolaurate (Tween® 20) methacrylates were synthesized by coupling methacryloyl chloride (MeOCl) to Tween 20 in the presence of 4-(N,N-dimethylamino) pyridine, using THF as a solvent, in order to investigate their suitability as precursors for photopolymerizable hydrogels in tissue engineering applications. The degree of substitution could be controlled by adjusting the molar ratio of MeOCl and Tween 20, giving three different monomers: Tween 20 monomethacrylate, Tween 20 dimethacrylate and Tween 20 trimethacrylate. Combined 1 H NMR and MALDI-TOF MS confirmed these monomers to be of high purity and to have polydispersities less than 1.3. It was shown that aqueous solutions of the monomers were photoactive, all the methacrylate groups reacting within 30 minutes exposure to a UV light intensity of 145 mW/cm 2. Aqueous Tween 20 trimethacrylate was then combined with N-vinyl-2-pyrrolidone (NVP), giving tough copolymer hydrogels on photopolymerization, whose swelling ratios and swelling rates could be tuned by varying the Tween 20 trimethacrylate content. The use of a flexible spacer with a multifunctional monomer gives a permanent three-dimensional network, whilst maintaining degrees of swelling of between 60 and 85%, with potential for a wide range of biological and non-biological applications. Hydrogels produced by photopolymerization have been extensively investigated as biomaterials for applications such as drug delivery carriers , scaffolds, coatings and tissue engineering [1]. Photopolymerization is a method of choice since it involves relatively short reaction times and minimal heating, and it does not require organic solvents [2]. The hydro-gel may be prepared from a low viscosity aqueous solution of a mono-mer, oligomer or macromer via a free radical pathway [3], typically resulting in a highly hydrated structure. A key advantage of photo-polymerized hydrogels over chemically or physically crosslinked hydro-gels is that their mechanical properties and swelling behavior may be tuned relatively easily by varying the molecular mass and/or the concentration of the precursors. On the other hand, their development is limited by the availability of such precursors and in many cases a high degree of mechanical stability is not required. Three basic strategies have been adopted: (i) use of existing photoactive, water soluble precursors; (ii) addition of photoactive groups to existing non-photoactive hydro-philic precursors; (iii) combination of water-soluble photoinitiators with hydrophilic precursors with limited photoactivity [4]. The third strategy, based on the use of water-soluble photoinitiators, is the most versatile in terms of the range …