Polyelectrolyte multilayer capsules of nano- to micrometer dimensions find practical application in a wide range of fields such as drug and gene delivery, water treatment, tissue engineering, and bio-imaging. Metal nanoparticles have been explored as exclusive functional components of the layer-by-layer capsules enabling remote opening of the capsules via various external stimuli (magnetic field, ultrasound, infra-red light), enhancing their mechanical properties, and extending the range of materials for sensing applications.<br/>Classical methods for the fabrication of nanoparticle-multilayer hybrid capsule assume pre-loading of the sacrificial cores used for the templating of the multilayers with the nanoparticles. Alternatively, nanoparticles can be used as constituents of polyelectrolyte multilayers and be incorporated into the multilayer shell. Finally, for some applications or if there are limitations of employing one of these two approaches, metal nanoparticles can be impregnated into as-prepared multilayer forming a metal coating on the top of the multilayers.<br/>Here, two approaches for the fabrication of nanoparticle-multilayer hybrids are presented and compared: PRE-LOADING of metal nanoparticles into mesoporous vaterite cores used as the templates for multilayer capsules made of synthetic polymers and POST-COATING of as-prepared multilayer capsules made of bio-polyelectrolytes. Magnetite or silver spherical nanoparticles have been utilized. Synthetic multilayer system was represented by poly(allylamine hydrochloride)/poly-(sodium styrene sulfonate) polymers (PAH/PSS system), while biopolymer-based capsules have been made of poly-L-lysine/hyaluronic acid (PLL/HA system). The importance of polymer dynamics in the multilayers and the shrinkage of the capsules are discussed. The pivotal role of nanoparticle stabilizing agent in the efficiency of post-coating has been demonstrated.<br/>Such hybrid organic-inorganic structures represent promising designing tools to deliver capsule payload with remote control over release kinetics.

Metal nanoparticles meet multilayer capsules: Pros and contras of pre-loading and post-coating approaches

ACS Spring Meeting 2021

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