We present a novel approach to construct hollow polymeric microcontainers that can be remotely addressed using a low-power near-infrared laser to release encapsulated materials. Microshells possessing walls with aggregates of gold nanoparticles are found to release encapsulated materials upon near-IR irradiation, while shells containing the same amount of nonaggregated gold nanoparticles did not release their contents. The permeability of thermally shrunk microcapsules to dextran molecules is the lowest for shells containing nonaggregated nanoparticles and the highest for microcapsules with no nanoparticles. The wall thickness, roughness, influence of concentration of encapsulated materials, and general shrinking behavior of the microcapsules are studied. Aggregation of nanoparticles increases the absorption coefficient in the near-infrared part of electromagnetic spectrum. The temperature increase upon near-infrared laser illumination for different gold nanoparticle distributions is simulated. Important implications of this approach are expected in development of drug delivery systems as well as in temperature- and light-sensitive materials and membranes.

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We present key factors that influence the mechanical stability of polyelectrolyte/nanoparticle composite microcontainers and their encapsulation behavior by thermal shrinkage. Poly(diallyldimethylammonium chloride) (PDADMAC), poly(styrenesulfonate) (PSS) microshells and citrate-stabilized gold nanoparticles are used. The presence of nanoparticles in the microshell renders the encapsulation process by heat-shrinking more difficult. The encapsulation efficiency is found to decrease as the concentration of material to be encapsulated increases. Increasing nanoparticle content in the microshell or the concentration of dextran increases the likelihood of getting fused and damaged capsules during encapsulation. On the other hand, mechanical studies show that doping microshells with gold nanoparticles significantly increases their stiffness and resistance to deformation. Internalization of capsules by cells supports that the incorporation of metal nanoparticles makes the shells more resistant to deformation. This work provides information of significant interest for the potential biomedical applications of polymeric microshells such as intracellular storage and delivery.