Biopolymers are attractive candidates to fabricate biocompatible hydrogels, but the low water solubility of most of them at physiological pH has hindered their applications. To prepare a water-soluble derivative of chitosan (WSC) biopolymer, it was grafted with a small anionic amino acid, l-glutamic acid, using a single-step 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide coupling reaction. This resulted in a zwitterion-tethered structure onto the polymer backbone. The degree of substitution range was 13-16 ± 1.25%, which was controlled by varying the feeding reagent ratios. Differential scanning calorimetry- and X-ray diffraction-based analysis confirmed a transition from  amorphous into a moderately amorphous/crystalline morphology after amino acid grafting, which made the derivative water-soluble at physiological pH. Composite hydrogels gelated within 60 s when using this WSC together with benzaldehyde-terminated 4-arm poly(ethylene glycol) as cross-linker. The compressive modulus of these hydrogels could be easily tuned between 4.0 ± 1.0 and 31 ± 2.5 kPa, either by changing the cross-linker concentration or total solid content in the final gel. The gels were injectable at the lowest cross-linker as well as total solid content, due to the enhanced elastic behavior. These hydrogels showed biodegradability during a 1 month incubation period in phosphate-buffered saline with weight remaining of 60 ± 1.5 and 44 ± 1.45% at pHs 7.4 and 6.5, respectively. The cytocompatibility of the gels was tested using the fibroblast cell line (i.e., WI-38), which showed good cell viability on the gel surface. Therefore, these hydrogels could be an important injectable biomaterial for delivery purpose in the future.

Here silver (GA-AgNPs) and gold nanoparticles (GA-AuNPs) were synthesized by an ecofriendly method using antioxidant, gallic acid (GA) simultaneously as capping and reducing agent. Their size ranged between 15 nm and 80 nm, which was controlled or dependent on the feeding ratio of GA. There was a linear relationship between the particle sizes versus the GA content. Moreover, they indicated a negative zeta potential value, which was decreased from −33 mV to −40 mV for AgNPs and from −36 mV to −42 mV for AuNPs after the addition of GA. In a typical PEGylation reaction of them, resulted into a large increase in the particle size as well as zeta potential value. The cytotoxicity assay against human fibroblast cell line (WI-38) for 24 h and 3-days showed that they were completely safe toward these cells. Therefore, these engineered NPs could be considered promising supplementary targeting materials in future.

Self-healing composite hydrogels are prepared from sustainable biopolymers by a green chemistry approach and analyzed by physicochemical and mechanical characterization techniques for future injectable anticancer biomaterials. Watersoluble chitosan (WSC) was prepared by grafting polyethylene glycol (PEG), glutamic acid and gallic acid onto the chitosan chain by carbodiimide chemistry. This WSC showed fast gelation (t ≈ < 60 seconds) with benzaldehyde-terminated 4-arm-PEG as a crosslinker through an amine/aldehyde Schiff base reaction.The compression modulus of these gels can be controlled between 6 and 67 kPa, which was dependent on both the crosslinker content as well as the total solid content (T%). It showed injectability and complete self-healing ability at the lower solid content (T = 2%). The hydrogel nanocomposites (HNCs) were synthesized together with gold (Au) and silver (Ag) nanoparticles (NPs) and tested for cytotoxicity using fibroblast cells (WI-38) for 48 hours, which showed good biocompatibility. The in-vitro assay against cancer cells (U87MG) for 48 hours indicated that only the HNCs with incorporated AuNPs were effective agents for cancer cell apoptosis in contrast to pristine gel, pure NPs (Ag and AuNPs) and HCNs with AgNPs. Therefore, these HNCs could be effective chemotherapeutic materials for designing anticancer nanomedicines in the future.