Abstract
During the last decade, stimuli-responsible polymers based on poly(N-isopropylacrylamide) having conformational transition in the range of physiological temperature have been discussed as novel drug delivery nanosystems. A star-like copolymer with a dextran core and grafted poly(N-isopropylacrylamide) arms (D-g-PNIPAM) was synthesized, characterized, and used as a matrix for silver sol preparation. The comparative study of the behavior of individual D-g-PNIPAM and the nanohybrid system D-g-PNIPAM/silver nanoparticles has been done in the temperature range near the lower critical solution temperature (LCST). The methods of Dynamic Light Scattering, small angle X-ray scattering, and UV-VIS absorption spectroscopy have been used. The existence of single nanoparticles and aggregated nanoparticles located in a limited polymer macromolecular volume was established. The increase of the temperature leads to slight aggregation of the silver nanoparticles at the LCST transition. Single nanoparticles do not aggregate with the temperature increase. The thermally induced collapse of end-grafted poly(N-isopropylacrylamide) chains above the LCST do not affect significantly the size characteristics of silver nanoparticles incorporated into the polymer matrix.
Highlights
The growing progress in nanotechnology and the life sciences demonstrates an urgent need for novel advanced hybrid materials composed of biocompatible polymers and inorganic components [1,2,3]
The thermally induced collapse of end-grafted poly(N-isopropylacrylamide) chains above the lower critical solution temperature (LCST) do not affect significantly the size characteristics of silver nanoparticles incorporated into the polymer matrix
The D-g-PNIPAM copolymer with dextran core (Mv = 7 × 105 g/mol) and 15 PNIPAM grafts were chosen for synthesis of a hybrid nanosystem with further precise analysis of temperature-induced changes in the polymer/Ag nanoparticles (AgNPs) nanosystem, since this polymer revealed well-defined size changes in the range of 25–40°C [21]
Summary
The growing progress in nanotechnology and the life sciences demonstrates an urgent need for novel advanced hybrid materials composed of biocompatible polymers and inorganic components [1,2,3]. PNIPAM has coil-to-globule transition at LCST and applies a pore opening and closing mechanism to the porous particles [11] This mechanism helps in the temperature-triggered release of the loaded molecules into a polymer matrix. The transition temperature for linear PNIPAM is very close to the human skin; this polymer can be applied for photodynamic anticancer therapy [12, 13]. The hybrid materials with Ag nanoparticles incorporated into a thermosensitive polymer matrix could be a real achievement in drug delivery. They can combine the local chemotherapy and antibacterial therapy with photothermal anticancer treatment. We discuss a behavior of the nanosystem consisting of Ag nanoparticles embedded into a branched PNIPAM matrix in the region of conformational transition of the polymer
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