Near-Infrared Light-Triggered Dissociation of Block Copolymer Micelles Using Upconverting Nanoparticles

We demonstrate a novel strategy enabling the use of a continuous-wave diode near-infrared (NIR) laser to disrupt block copolymer (BCP) micelles and trigger the release of their “payloads”. By encapsulating NaYF₄:TmYb upconverting nanoparticles (UCNPs) inside micelles of poly(ethylene oxide)-<i>block</i>-poly(4,5-dimethoxy-2-nitrobenzyl methacrylate) and exposing the micellar solution to 980 nm light, photons in the UV region are emitted by the UCNPs, which in turn are absorbed by <i>o</i>-nitrobenzyl groups on the micelle core-forming block, activating the photocleavage reaction and leading to the dissociation of BCP micelles and release of co-loaded hydrophobic species. Our strategy of using UCNPs as an internal UV or visible light source upon NIR light excitation represents a general and efficient method to circumvent the need for UV or visible light excitation that is a common drawback for light-responsive polymeric systems developed for potential biomedical applications

Near Infrared Light Triggered Release of Biomacromolecules from Hydrogels Loaded with Upconversion Nanoparticles

Using a photosensitive hybrid hydrogel loaded with upconversion nanoparticles (UCNPs), we show that continuous-wave near-infrared (NIR) light (980 nm) can be used to induce the gel–sol transition and release large, inactive biomacromolecules (protein and enzyme) entrapped in the hydrogel into aqueous solution “on demand”, where their bioactivity is recovered. This study is a new demonstration and development in harnessing the unique multiphoton effect of UCNPs for photosensitive materials of biomedical interest

A “Plug-and-Play” Method to Prepare Water-Soluble Photoresponsive Encapsulated Upconverting Nanoparticles Containing Hydrophobic Molecular Switches

A convenient and versatile protocol to encapsulate lanthanide doped upconverting nanoparticles by an amphiphilic polymer shell containing photoresponsive diarylethene chromophores was developed. The assemblies are all water-soluble and fluoresce in the visible region of the spectrum when excited with 980 nm near-infrared light. The fluorescent emission can be selectively and reversibly modulated by alternatively irradiating the photoresponsive nanoparticles with UV light and visible light, which triggers ring-closing and ring-opening reactions of the chromophores, respectively. Fluorescence lifetime experiments suggest that the quenching mechanism is a combination of energy transfer and emission-reabsorption processes. These photoresponsive upconverting nanoparticles have the potential to advance bioimaging and other applications in nanophotonics

Analysis of the Shell Thickness Distribution on NaYF₄/NaGdF₄ Core/Shell Nanocrystals by EELS and EDS

The structure and chemical composition of the shell distribution on NaYF₄/NaGdF₄ core/shell nanocrystals have been investigated with scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDS). The core and shell contrast in the high-angle annular dark-field (HAADF) images combined with the EELS and EDS signals indicate that Gd is indeed on the surface, but for many of the particles, the shell growth was anisotropic