Heavy metal ions are known to cause environmental pollution and several human diseases because of their inherent toxicity. Among them, Cu 2+ is an essential element for the human body, but its continuous exposure and accumulation may cause adverse effects. Thus, copper ion levels in aquatic environments are strictly regulated by international standards. Herein, we demonstrate a simple optical method for detecting Cu 2+ using plasmonic sugar nanoprobes (PSNs) composed of gold nanoparticles and polysaccharides. Gold precursors were reduced to nanoparticles and spontaneously embedded in the sugar-based polymeric network with the sulfated residues of carrageenan during the polymerization procedure. Owing to the abundant functional residues of PSNs and their affinity toward Cu 2+ , we observed the Cu 2+ -mediated preferential dissociation of the PSNs, resulting in absorbance spectral shifts and scattering shifts of the PSNs. Based on these plasmon band shifts, Cu 2+ below the EPA regulation level of 20 μM can be easily detected by the optimized experimental condition. Additionally, the reaction mechanism between the PSNs and Cu 2+ was elucidated by indepth spectroscopic analyses, which revealed that the increased binding of Cu 2+ to the sulfate groups in the PSNs induces the eventual decomposition of the PSNs.

Background Spatiotemporal regulation is one of the major considerations for developing a controlled and targeted drug delivery system to treat diseases efficiently. Light-responsive plasmonic nanostructures take advantage due to their tunable optical and photothermal properties by changing size, shape, and spatial arrangement. Results In this study, self-integrated plasmonic hybrid nanogels (PHNs) are developed for spatiotemporally controllable drug delivery through light-driven conformational change and photothermally-boosted endosomal escape. PHNs are easily synthesized through the simultaneous integration of gold nanoparticles (GNPs), thermo-responsive poly (N-isopropyl acrylamide), and linker molecules during polymerization. Wave-optic simulations reveal that the size of the PHNs and the density of the integrated GNPs are crucial factors in modulating photothermal conversion. Several linkers with varying molecular weights are inserted for the optimal PHNs, and the alginate-linked PHN (A-PHN) achieves more than 2-fold enhanced heat conversion compared with others. Since light-mediated conformational changes occur transiently, drug delivery is achieved in a spatiotemporally controlled manner. Furthermore, light-induced heat generation from cellular internalized A-PHNs enables pinpoint cytosolic delivery through the endosomal rupture. Finally, the deeper penetration for the enhanced delivery efficiency by A-PHNs is validated using multicellular spheroid. Conclusion This study offers a strategy for synthesizing light-responsive nanocarriers and an in-depth understanding of light-modulated site-specific drug delivery.

Background Spatiotemporal regulation is one of the major considerations for developing a controlled and targeted drug delivery system to treat diseases efficiently. Light-responsive plasmonic nanostructures take advantage due to their tunable optical and photothermal properties by changing size, shape, and spatial arrangement. Results In this study, self-integrated plasmonic hybrid nanogels (PHNs) are developed for spatiotemporally controllable drug delivery through light-driven conformational change and photothermally-boosted endosomal escape. PHNs are easily synthesized through the simultaneous integration of gold nanoparticles (GNPs), thermo-responsive poly (N-isopropyl acrylamide), and linker molecules during polymerization. Wave-optic simulations reveal that the size of the PHNs and the density of the integrated GNPs are crucial factors in modulating photothermal conversion. Several linkers with varying molecular weights are inserted for the optimal PHNs, and the alginate-linked PHN (A-PHN) achieves more than twofold enhanced heat conversion compared with others. Since light-mediated conformational changes occur transiently, drug delivery is achieved in a spatiotemporally controlled manner. Furthermore, light-induced heat generation from cellular internalized A-PHNs enables pinpoint cytosolic delivery through the endosomal rupture. Finally, the deeper penetration for the enhanced delivery efficiency by A-PHNs is validated using multicellular spheroid. Conclusion This study offers a strategy for synthesizing light-responsive nanocarriers and an in-depth understanding of light-modulated site-specific drug delivery. Graphical Abstract