Biocompatible polyaniline nanocomposites build a soft interface between biology and opto-electronics.

Polyaniline, in its doped conducting form of emeraldine salt, has been synthesized in aqueous dispersion, in the presence of different water soluble polymers used as steric stabilizers. PANI nanoparticles of different shape and size distribution have been obtained as aqueous dispersions and either deposited onto rigid substrates or immobilized into crosslinked polymer networks, yielding to soft hydrogel-based nanocomposites. Gelation of the aqueous dispersions has been proved possible by inducing “in-situ” chemical crosslinking of the steric stabilizer used during PANI synthesis or by addition of other crosslinkable, water soluble polymers, with a variety of techniques, ranging from high energy irradiation to more conventional chemical methodologies, including also UV photocrosslinking. Objective of this research is to develop a functional nanocomposites platform that combines the electro-optic properties of the conducting polymer nanoparticles with process flexibility, highly hydrophilic character and biocompatibility of the polymer matrix materials, to yield novel materials with multi-application potential in diagnostic, therapeutic and regenerative medicine. For the purpose, the morphology of the different colloidal PANI systems has been studied at different scales, with SEM or TEM, as appropriate. The electrochemical activity of PANI at the variance of pH has been assessed through cyclic voltammetry. Both the colloidal dispersions and their gelled analogues have been characterized for their UV-vis absorption and photo-emission properties. These properties have been related to the nature and extent of interaction between the conjugated polymer nanoparticles and the stabilizing polymer. Selected hydrogel nanocomposites have been subjected to MTT assays in order to ascertain the absence of cytotoxicity as the first necessary step to assess their biocompatibility