CONICET | Buscador de Institutos y Recursos Humanos

Spin label EPR spectroscopy was used to study the pore filling of macroporous silicon with DMPC liposomes. Macroporous samples having a thickness of around 13 μm, and nearly cylindric pores of 1.0-1.2 μm diameter were obtained by electrochemical anodization of p-type silicon wafers, in darkness. The samples were oxidized in a NaOH solution, in order to turn hydrophilic the inner surface of the pore network. Then, the pore structure was filled with an aqueous solution of 100 nm unilamellar DMPC liposomes including 2 mole percent of the spin label 5-SASL. EPR spectra were acquired in X band at 30ºC after different incubation procedures. While liposomes have isotropic EPR spectra, the spectra of lipids inside porous samples when B is parallel to the pore axis were different from those with B perpendicular to the axis. Simulations of the spectra indicate that cylindrical lipid bilayers were formed covering the inner surface of the pores, although some liposomes remain. Diverse protocols were explored in order to achieve an adequate lipid hydration. We propose the use of a 2D photonic crystal made of macroporous silicon, which can sense changes in the dielectric function of the filling material, to study the effects of confinement on DMPC phase transition.