A novel class of pH-responsive hollow poly(L-glutamic acid)/chitosan (PLGA/CS) nanogels was fabricated by a templating approach, which was mild and surfactant free, and combined with a “grafting from” method and intermacromolecular crosslinking technique. The surface grafting, crosslinking reaction, nanogel fabrication and microstructure were investigated by FTIR, 1H NMR, XRD, TGA, light scattering, and electron microscopy. The size of the resultant PLGA/CS nanogels could be accurately controlled by simply changing the size of the silica template. The nanogels responded to changes in environmental pH, elucidated according to the variation of the size of the nanogels and zeta potential at different pH values. Taking water-soluble antineoplastic agent mitoxantrone (MTX) as a model drug, the nanogels presented high loading ability at high-pH environment and rapid MTX release behavior under acidic conditions. MTT assays used to study the in vitro cytotoxicity of PLGA/CS nanogels showed a negligible cytotoxicity in mouse fibroblast L929 cells. Compared with bare MTX, MTX loaded PLGA/CS nanogels exhibited an enhanced inhibition effect to human gastric carcinoma SGC7901 cells. Fluorescence microscopy and flow cytometry analysis results demonstrated efficient cellular uptake of the PLGA/CS nanogels into the cells. These studies suggest that such pH-responsive PLGA/CS hollow nanogels might have great potential in controlled drug delivery systems.

Injectable hydrogels as an important biomaterial class have been widely used in regenerative medicine. A series of injectable poly(L-glutamic acid)/chitosan (PLGA/CS) hydrogels were fabricated by self-crosslinking aldehyde-modified PLGA (PLGA–CHO) and lactic acid-modified chitosan (CS–LA). The oxidation degree of PLGA–CHO and degree of substitution (DS) of CS–LA could be adjusted by the amount of sodium periodate and lactic acid, respectively. The effect of the solid content of the hydrogels, oxidation degree of PLGA–CHO and CS–LA/PLGA–CHO mass ratio on the gelation time, gel content, water uptake, mechanical properties, microscopic morphology, and in vitro degradation of the hydrogels was examined. The pH and ion sensitivity of PLGA/CS hydrogels was also examined. Encapsulation of rabbit chondrocytes within the hydrogels showed viability of the entrapped cells and cytocompatibility of the injectable hydrogels. The injectable PLGA/CS hydrogels demonstrated attractive properties for future application in pharmaceutical delivery and tissue engineering.

Injectable, in situ forming hydrogels have exhibited many advantages in regenerative medicine. Herein, we present the novel design of poly(L-glutamic acid) injectable hydrogels via the self-crosslinking of adipic dihydrazide (ADH)-modified poly(L-glutamic acid) (PLGA–ADH) and aldehyde-modified poly(L-glutamic acid) (PLGA–CHO), and investigate their potential in cartilage tissue engineering. Both the hydrazide modification degree of PLGA–ADH and oxidation degree of PLGA–CHO can be adjusted by the amount of activators and sodium periodate, respectively. Experiments reveal that the solid content of the hydrogels, –NH2/–CHO molar ratio, and oxidation degree of PLGA–CHO have a great effect on the gelation time, equilibrium swelling, mechanical properties, microscopic morphology, and in vitro degradation of the hydrogels. Encapsulation of rabbit chondrocytes within the hydrogels showed viability of the entrapped cells and cytocompatibility of the injectable hydrogels. A preliminary study exhibits injectability and rapid in vivo gel formation, as well as mechanical stability, cell ingrowth, and ectopic cartilage formation. These results suggest that the PLGA hydrogel has potential as an injectable cell delivery carrier for cartilage regeneration and could serve as a new biomaterial for tissue engineering.

Injectable hydrogels as an important biomaterial class have been widely used in regenerative medicine. A series of injectable poly(l-glutamic acid)/alginate (PLGA/ALG) hydrogels were fabricated by self-cross-linking of hydrazide-modified poly(l-glutamic acid) (PLGA-ADH) and aldehyde-modified alginate (ALG-CHO). Both the degree of PLGA modification and the oxidation degree of ALG-CHO could be adjusted by the amount of activators and sodium periodate, respectively. The effect of the solid content of the hydrogels and oxidation degree of ALG-CHO on the gelation time, equilibrium swelling, mechanical properties, microscopic morphology, and in vitro degradation of the hydrogels was examined. Encapsulation of rabbit chondrocytes within hydrogels showed viability of the entrapped cells and good biocompatibility of the injectable hydrogels. A preliminary study exhibited injectability and rapid in vivo gel formation, as well as mechanical stability, cell ingrowth, and ectopic cartilage formation. The injectable PLGA/ALG hydrogels demonstrated attractive properties for future application in a variety of pharmaceutical delivery and tissue engineering, especially in cartilage tissue engineering.

•Fe3O4 nanoparticles were in situ synthesized inside nanoporous microcapsules.•Fe3O4 nanoparticles were homogeneously dispersed in the polymer matrix.•Magnetic microcapsules could be easily manipulated by an external magnetic field.•The MTX loading capacity depended on loading time and MTX concentration.•The microcapsules exhibited sustained release behavior.The magnetic polymer microcapsules, as a promising environmental stimuli-responsive delivery vehicle, have been increasingly exploited to tackle the problem of remotely navigated delivery. This study presented a novel design and fabrication of magnetic poly(l-glutamic acid)/chitosan (PGA/CS) microcapsules. Magnetic Fe3O4 nanoparticles were in situ synthesized inside nanoporous PGA/CS microcapsules and resultant magnetic PGA/CS microcapsules were characterized. Mitoxantrone (MTX), an antineoplastic drug, was chosen as a water-soluble model drug to research the loading and release properties of the microcapsules. The results showed the carboxylate groups of PGA within polyelectrolyte walls could be used as binding sites for the absorption of iron ions and reaction sites for the synthesis of magnetic nanoparticles. Magnetic PGA/CS microcapsules were dissected using a dual-beam scanning electron microscope/focused ion beam (SEM/FIB) for morphological and microstructural examination. It was found that Fe3O4 nanoparticles with size of about 10 nm were homogeneously dispersed in the polymer matrix and adhered to the pore walls of the microcapsules. Increasing the concentration of iron ions led to an increasing loading content of Fe3O4 nanoparticles and an increase in the resultant magnetization. The magnetic PGA/CS microcapsules could be easily manipulated by an external magnetic field. The MTX loading capacity depended on loading time and MTX concentration. The high loading could be ascribed to spontaneous deposition of MTX induced by electrostatic interaction. The microcapsules exhibited sustained release behavior. The MTX release from microcapsules could be best described using Korsmeyer–Peppas and Baker–Lonsdale models, indicating the diffusion mechanism of drug release from both PGA/CS microcapsules and magnetic PGA/CS microcapsules. Therefore, the novel magnetic PGA/CS microcapsules are expected to find application in drug delivery systems because of the properties of magnetic sensitivity, high drug loading and sustained release.

NiZn ferrite/silica nanocomposites with a novel watermelon-like structure were first synthesized by two-step microemulsion process. Using two separate steps allows the great flexibility to choose the core with the desired magnetic response. TEM shows that the NiZn ferrite nanoparticles are homogeneously dispersed in spheral nanosized silica matrix. Magnetic measurement reveals that dispersing the ferrite nanoparticles in silica matrix has some effect on magnetic behavior. The blocking temperature decreases upon SiO2 coating.

Injectable, in situ forming hydrogels have exhibited many advantages in regenerative medicine. Herein, we present the novel design of poly(L-glutamic acid) injectable hydrogels via the self-crosslinking of adipic dihydrazide (ADH)-modified poly(L-glutamic acid) (PLGA–ADH) and aldehyde-modified poly(L-glutamic acid) (PLGA–CHO), and investigate their potential in cartilage tissue engineering. Both the hydrazide modification degree of PLGA–ADH and oxidation degree of PLGA–CHO can be adjusted by the amount of activators and sodium periodate, respectively. Experiments reveal that the solid content of the hydrogels, –NH2/–CHO molar ratio, and oxidation degree of PLGA–CHO have a great effect on the gelation time, equilibrium swelling, mechanical properties, microscopic morphology, and in vitro degradation of the hydrogels. Encapsulation of rabbit chondrocytes within the hydrogels showed viability of the entrapped cells and cytocompatibility of the injectable hydrogels. A preliminary study exhibits injectability and rapid in vivo gel formation, as well as mechanical stability, cell ingrowth, and ectopic cartilage formation. These results suggest that the PLGA hydrogel has potential as an injectable cell delivery carrier for cartilage regeneration and could serve as a new biomaterial for tissue engineering.