Pegylated titanates have been prepared as biomedical supports in the form of thin films. The independent preparation of a polyethylene glycol (PEG) and a titanium isopropoxide (TIPT) precursor was followed by mixing at different molar ratios and spin casting onto Si (100) substrates to form the films. Activation of the hybrid structure was induced by annealing at temperatures right below the PEG melting point. Structural and compositional changes during these steps were followed by Fourier transformed infrared (FTIR) spectroscopy, XPS and water contact angle (CA) measurements. Biofunctionality of the pegylated titanates as antifouling ophthalmic films was tested on the one hand by determination of optical constants using genetic algorithms. On the other hand, indication of surface biocompatibility was provided by seeding mesenchymal stem cells.
IntroductionThe sol-gel processing of hybrid materials containing an inorganic matrix bearing a molecular structure is currently in expansion in the field of biomaterials. In this configuration, the created structures benefit from the stability of the inorganic matrix and the biological response determined by the molecular groups. This approach has been generally applied to produce hybrid films with a wide spectrum of functionalities including biomedical, structural, anticorrosion, optical and electronic applications. [1] In the biomedical field, the organic phase may principally bear two kinds of molecules. On the one hand, those providing chemical bonds destined to enhance cell proliferation or initiate the adhesion cascade of a target biomolecule or, on the other hand, molecular structures with an antifouling character aiming at the inhibition of unspecific interactions at the interface. Biofunctional hybrid films that modified cell adhesion [2] and allowed the controlled molecular immobilization of DNA [3] have been already proposed by our group. These films were prepared by the sol-gel process using titanium isopropoxide (TIPT) as precursor leading to the inorganic phase, which has previously led to optically functional films. [4] Materials used for the fabrication of ophthalmic lenses (both intra and exo) require a complex equilibrium of optical, surface antifouling and mechanical properties to become functional. In this work we propose the use of poly(ethylene-glycol) (PEG), a recurrent polymer used in antifouling applications at biomolecular and cellular level, [5] to form hybrid films with TIPT as potential enhancers of optical and surface properties of ophthalmic lenses in view of the reputed antifouling properties of PEG and the above-mentioned optical properties of TIPT.
ExperimentalFor film preparation, TIPT and PEG precursors were prepared in a two-step process from TIPT (Puurum, Fluka) and PEG (MW 6000, Fluka). Firstly, we prepared a 0.4 M TIPT solution in ethanol containing a precise TIPT/water ratio (r w = 0.82) and controlled pH (pH = 1.27). [4] Secondly, a selected quantity of PEG was dissolved in toluene to form a 5% w/v solution. Mixtures were prepar...