Using a thermally responsive polymer with the intrinsic chemical and physical nature of stimuli-sensitive smart materials, it is possible to fabricate environmental switches for the controlled-release of pharmaceutical drug. Particularly, much attention has been paid to the biomedical applications of poly(N-isopropylacrylamide) (PNIPAAm) because of its unique reversible transition at a specific lower critical solution temperature (LCST). A Poly(N-isopropylacrylamide-b-poly(D,D-lactide)) (PNIPAAm-PDLA) diblock copolymer template was prepared as a micelle of sub-micrometer diameter, entrapped by an outer shell composed of a poly(L,L-lactide-b-poly(ethylene glycol)) (PLLA-PEG) copolymer. The outer surface of the structures was modified by the self-assembly of Au nanoparticles to enhance the heat transfer rate from external irradiation to the polymeric nanospheres. It is associated with our objective to force the inner sphere to collapse by thermal change and then efficiently fill the cavity of the structures with a hydrophilic drug such as bovine serum albumin (BSA). From UV/VIS, DSC spectroscopy, TEM micrographs, and a quasi-elastic light scattering (QELS) spectrometer at 25 C, the results demonstrate the successful formation of structures of PLLA-PEG@PNIPAAm-PDLA prepared by a modified-double-emulsion method with two different types of diblock copolymers composed of an inner-shell for thermal response loaded with BSA and a biodegradable outer-shell. Since the rate of drug release can be solely controlled by the outer-shell composition, it is possible to manipulate the variation in composition and enantiomeric substitutes for a specific purpose to administer the drug in a controlled fashion. The unique transition of PLLA-PEG@PNIPAAm-PDLA nanocapsules physiologically permits various kinds of feasible applications for controlled drug release systems.

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