Tailored design of NHS-SS-NHS cross-linked chitosan nano-hydrogels for enhanced anti-tumor efficacy by GSH-responsive drug release.

The traditional chemotherapeutic agents' disadvantages such as high toxicity, untargeting and poor water solubility lead to disappointing chemotherapy effects, which restricts its clinical application. In this work, novel size-appropriate and glutathione (GSH)-responsive nano-hydrogels were successfully prepared via the active ester method between chitosan (containing -NH2) and cross-linker (containing NHS). Especially, the cross-linker was elaborately designed to possess a disulfide linkage (SS) as well as two terminal NHS groups, namely NHS-SS-NHS. These functionalities endowed chitosan-based cross-linked scaffolds with capabilities for drug loading and delivery, as well as a GSH-responsive mechanism for drug release. The prepared nano-hydrogels demonstrated excellent performance applicable morphology, excellent drug loading efficiency (∼22.5%), suitable size (∼100 nm) and long-term stability. The prepared nano-hydrogels released over 80% doxorubicin (DOX) after incubation in 10 mM GSH while a minimal DOX release less than 25% was tested in normal physiological buffer (pH = 7.4). The unloaded nano-hydrogels did not show any apparent cytotoxicity to A 549 cells. In contrast, DOX-loaded nano-hydrogels exhibited marked anti-tumor activity against A 549 cells, especially in high GSH environment. Finally, through fluorescent imaging and flow cytometry analysis, fluorescein isothiocyanate-labeled nano-hydrogels show obvious specific binding to the GSH high-expressing A549 cells and nonspecific binding to the GSH low-expressing A549 cells. Therefore, with this cross-linking approach, our present finding suggests that cross-linked chitosan nano-hydrogel drug carrier improves the anti-tumor effect of the A 549 cells and may serve as a potential injectable delivery carrier.

Improvement of the bonding properties of cassava starch-based wood adhesives by using different types of acrylic ester.

High performance of starch-based wood adhesives (SWAs) is important for their industrial applications. In this study, we designed and demonstrated the use of different types of acrylic ester for improving the bonding performance of SWAs. Results showed that the addition of acrylic ester as the co-monomer showed significantly the bonding capacity and hydrophobicity of SWAs. Furthermore, SWAs added hexyl acrylate could improve the shear strength to 11.23 MPa and 5.63 MPa in dry and wet states, respectively. Further analysis found that the improved bonding performance of SWAs could be attributed to the low minimum film-forming temperature, the enhanced the film-forming rate and the improved hydrophobicity by the addition of hexyl acrylate. These results offer a major development in the preparation of high-performance bio-based wood adhesives.