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Hydrogels based scaffolds are very promising materials for a wide range of medical applications including tissue engineering and drug delivery. This study reports a covalently cross-linked composite hydrogel embedded with microspheres basing natural polysaccharides as a protein delivery system for soft tissue engineering. This biodegradable composite hydrogel derived from water-soluble chitosan and alginate derivatives upon mixing, without addition of chemical cross-linking agents. The gelation is attributed to the Schiff-base reaction between amino and aldehyde groups of N-succinyl chitosan (N-Chi) and oxidized alginate (OAlg), respectively. Meanwhile, gel-like microspheres were prepared with a diameter of 2-10 μm by conjugating sodium alginate with Ca 2+ in an aqueous emulsion via the emulsion cross-linking technique. Bull Serum Albumin (BSA) was encapsulated into alginate gel microspheres and subsequently incorporated into OAlg/N-Chi hydrogels to produce a composite scaffold. In the current work, gelation rate, morphology, mechanical properties, swelling ratio, in vitro degradation and BSA release of the composite scaffolds were examined. The results show that mechanical and stable properties of gel scaffolds can be significantly improved by embedding alginate microspheres. The alginate microspheres can serve as a filler to toughen the soft OAlg/N-Chi hydrogels. Compressive modulus of composite gel scaffolds containing 0.5 mL volume of microspheres was 57.3 KPa, which was higher than the control hydrogel without microspheres. Moreover, the controlled release of BSA encapsulated within this composite hydrogels showed significantly lower rate when compared with control hydrogel or microspheres alone. These characteristics provide a potential opportunity to use this injectable composite gel scaffold in protein delivery and soft tissue engineering applications., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Injectable hybrid hydrogels were produced by mixing crosslinked aldehyde hyaluronic acid with dexamethasone grafted water soluble chitosan, without the addition of a chemical crosslinking agent. The gelation is attributed to the Schiff-base reaction between amino and aldehyde groups of hydrogel precursors. In this article, the water soluble chitosan, N-succinyl-chitosan, grafted with dexamethasone via water soluble carbodiimide chemistry has been characterized. In vitro gelation time, morphologies, swelling, weight loss, and compressive modulus of hybrid hydrogels in phosphate buffered saline were studied. The dexamethasone grafted hydrogel showed a slightly lower gelation time, higher water uptake and faster weight loss compared to the hydrogel without dexamethasone. Human adipose-derived stem cells were encapsulated into the dexamethasone grafted hydrogel in vitro to assess the biological performance and applicability of the hydrogel as cell carrier. Results demonstrated that the dexamethasone grafted hydrogel resulted in enhanced cell adhesion and proliferation as compared to the hydrogel without dexamethasone. These characteristics provide a potential opportunity for the dexamethasone grafted hybrid hydrogel as an injectable scaffold in adipose tissue engineering applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]