Functionalized hollow microcapsules built by multilayer self-assembly of photo-activatable polyelectrolytes

C.D. BORSARELLI (CONFERENCISTA)

Viña del Mar

Encuentro; XIV ENCUENTRO LATINOAMERICANO DE FOTOQUIMICA Y FOTOBIOLOGIA; 2019

USACH

The fabrication of hollow microcapsules (HMC) with a polyelectrolyte shell assembled by the layer-by-layer (LbL) technique onto the surface of removable micro-templates has received large attention, because of their potential applications in diverse areas ranging from medicine and biotechnology, up to catalysis and synthetic chemistry. The properties and applications of the HMC can be tuned by selecting the micro-template that controls shape and size, polyelectrolyte nature for mechanical and interfacial characteristics, and additives occluded in the core and/or shell for specific functionality. Typical synthetic polyelectrolytes used for multilayer formation are sodium poly(styrene sulfonate) (PSS), poly(vinyl sulfate) (PVS); poly(ethylenimine) (PEI) and poly(allylamine hydrochloride) (PAH); among other biological polyelectrolytes such as DNA, chitosans, and proteins. The functionalization of the microcapsule shell can be obtained by decoration with organic dyes, metal nanoparticles, antigens, or using intrinsically functionalized polyelectrolytes.Therefore, the functionalized HMC can be able to respond to external stimuli, such as pH, temperature, light, ionic strength, etc., generating specific responses for instance controlled release, molecular recognition and sensing, redox, and photo-redox functions, among others.Here, we present a couple of recent examples of functionalized HMC constructed using CaCO3 microspheres as sacrificial templates covered with photo-activatable polyelectrolytes such: i) DNA-bioinspired polymer grafting the vinylbenzylthymine (VBT) monomer between ionic units of sodium vinylphenylsulfonate (VPS) or vinylbenzyltriethylammonium chloride (VBA), which are able to crosslink through thymine dimers by UVB irradiation, controlling HMC mechanical stability and permeability; and ii) poly(allylamine hydrochloride) with covalent attached rose Bengal (PAH-RB) and sodium poly(styrene sulfonate) (PSS) as counter-polyelectrolyte to form HMC with singlet oxygen photosensitizing properties.The presented results remark the versatility and suitability of HMC grafted with photo-activatable polyelectrolytes for its application in controlled release of occluded substrates and photo-oxidation reactions with a micro-sized photosensitizer easily removable and reusing in aqueous solutions.