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The stimulus-responsive drug delivery system has attracted increasing attention due to its ability to enhance therapeutic efficacy and reduce side effects. Herein, a pH and glutathione (GSH) dually responsive drug carrier, hollow silica–-polyelectrolyte composite nanoparticle, was successfully prepared by using a template of spherical polyelectrolyte brush (SPB) which consists of a polystyrene (PS) core and a densely grafted linear poly(acrylic acid) (PAA) shell. The existence of PAA chains and introduction of disulfide bonds in silica framework endow the composite nanoparticles with pH and GSH dually responsive properties which were confirmed by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). With doxorubicin hydrochloride (DOX) as the model drug, the loading content and encapsulation efficiency could reach up to 43% and 96%, respectively. The drug release behavior was investigated under various environments, showing that the drug release rate increased with the decrease in pH value and the increase in GSH concentration. The prepared hollow SiO2–PAA composite nanoparticles possess a great potential as carriers for controlled drug delivery.

Hollow silica–polyelectrolyte composite nanoparticles were prepared using templates of spherical polyelectrolyte brushes which consist of a polystyrene (PS) core and a densely grafted linear poly(acrylic acid) shell. The obtained hollow particles were systematically studied by small-angle X-ray scattering (SAXS) in combination with other characterization methods such as transmission electron microscopy and dynamic light scattering. The hollow structure formed by dissolving the PS core was confirmed by the reduction of electron density to zero in the cavity through fitting SAXS data. SAXS revealed both the inward and outward expansions of the hollow silica–polyelectrolyte composite particles upon increasing pH from 3 to 9, while further increasing pH led to the partial dissolution of silica layer and even destruction of the hollow structure. SAXS was confirmed to be a unique and powerful characterization method to observe hollow silica nanoparticles, which should be ideal candidates for controlled drug delivery.

A thermo-sensitive biocompatible amphiphilic material, N-phthaloylchitosan-g-poly(N-vinylcaprolactam) which could self-assemble into spherical micelles with good stability in aqueous medium, was synthesized. Meloxicam (MLX), a strongly hydrophobic pain killer for ankylosing spondylitis, was encapsulated into the hydrophobic cores of the micelles successfully as a model drug. The micelles showed excellent stability after MLX loading. Furthermore, the prepared micelles presented obvious thermo-sensitivity with lower critical solution temperature around 32 °C, where the MLX release rate reduced obviously when the temperature increased above it. This drug delivery system could achieve long time drug release under body temperature. The obtained biosurfactant should be an ideal candidate for applications in the development of long-lasting drug delivery systems.

Tunable immobilization of bovine serum albumins (BSA) onto anionic spherical polyelectrolyte brushes (SPB) by changing BSA concentration, pH, and ionic strength was mainly observed by small-angle X-ray scattering (SAXS). Change of the BSA amount immobilized in SPB can be determined by SAXS which was confirmed by UV spectroscopy, and SAXS is the unique method to “see” the distribution of BSA in SPB. More BSA entered into brush layer upon increasing the protein concentration or decreasing the ionic strength of solutions. When pH increased from 3 to 5 (around the isoelectric point of BSA 4.9), more BSA came into the brush inner layer, while the proteins partly moved to the outer layer when pH continued to increase. After pH was higher than 7, most of BSA were desorbed from SPB. SAXS is proved to be a powerful tool to monitor the tunable immobilization and distribution of proteins in SPB.

Multilayer modified spherical polyelectrolyte brushes were prepared through alternate deposition of positively charged poly(allylamine hydrochloride) (PAH) and negatively charged poly-l-aspartic acid (PAsp) onto negatively charged spherical poly(acrylic acid) (PAA) brushes (SPBs) on a poly(styrene) core. The charge reversal determined by the zeta potential indicated the success of layer-by-layer (LBL) deposition. The change of the structure during the construction of multilayer modified SPBs was observed by small-angle X-ray scattering (SAXS). SAXS results indicated that some PAH chains were able to penetrate into the PAA brush for the PAA-PAH double-layer modified SPBs whereas part of the PAH moved towards the outer layer when the PAsp layer was loaded to form a PAA-PAH-PAsp triple-layer system. The multilayer modified SPBs were stable upon changing the pH (5 to 9) and ionic strength (1 to 100 mM). The triple-layer modified SPBs were more tolerated to high pH (even at 11) compared to the double-layer ones. SAXS is proved to be a powerful tool for studying the inner structure of multilayer modified SPBs, which can establish guidelines for the a range of potential applications of multilayer modified SPBs.