Abstract
New Surfactant PolyIon Complex (SPIC) micelles were assembled by electrostatic complexation of an antibacterial cationic surfactant, cetylpyridinium chloride (CPC), and a double hydrophilic block copolymer containing a neutral comb block of poly(oligo(ethylene glycol) methyl ether acrylate (PEOGA) and a weak polyacid block (poly(acrylic acid) (PAA). The corresponding SPIC micelles, with a CPC/PAA core and a PEOGA corona, were succesfully used as structure directing and functionalising agents in an eco-compatible sol-gel strategy, yielding hybrid mesoporous silica (MS) nanoparticles with diameters smaller than 100 nm and a monomodal pore size distribution centred at 2.8 nm. The influence of synthesis parameters, including the pH, concentrations and ratios of components, was systematically investigated. The obtained MS nanoparticles were intrinsically functional, with copolymers grafted to the pore surface via H-bonding between silica and the PEOGA blocks, while weak polyacid blocks, complexed with CPC, were confined within the mesopores. The response of these MS hybrid nanoparticles to pH changes (pH 7.4, 4.2 and 3) indicated remarkable stability of the anchored copolymer, while CPC was selectively released under the acidic conditions typical of orodental biofilm microenvironments. This result is noteworthy, since the release of encapsulated amphiphilic drugs into water is less favorable than that of hydrophilic drugs. Owing to their dimensional, porous and chemical control, MS hybrid nanoparticles templated and functionalised with SPIC micelles will be materials of choice for developing pH-responsive biomedical devices using wet processing techniques.