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In situ 3D printing technologies is a new frontier for highly personalized medicine, which requires suitable bioink with rheology, biocompatibility, and gelation kinetics to support the right shape and mechanical properties of the printed construct. To this end, a facile design of thermo/photo dual cure composite hydrogel was proposed using MHBC and soluble collagen in this study. M/C composite hydrogel exhibited rapid thermo-induced sol-gel transition and contraction, tunable mechanical properties, proper microstructure and biodegradability for 3D cell culture, as well as improve cyto-compatibility, all of which were dependent upon the methacrylation degree of MHBC and M/C ratios. The printability of the optimal formulation (3% MHBC/1% collagen) was validated by its mild printing condition, rapid gelation of bioink at 37 °C and simple postprocessing manipulation. Both desirable printability and cyto-compatibility enable M/C composite hydrogel a potential candidate as bioink to be applied for in situ 3D bioprinting., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The aim of this study was to develop an effective cell sheet translocation method using a cell adhesive and temperature-responsive hydroxybutyl chitosan hydrogel (HBC). The polydopamine (PD)-coated HBC hydrogels were prepared by the dopamine self-polymerization on the surface of HBC hydrogel with different coating time, termed as P30, P60 and P120, respectively. Gelling property of HBC was not affected by PD coating. The PD-coated HBC hydrogels promoted the attachment and proliferation of mouse fibroblast cells (L929) and human umbilical vein endothelial cells (HUVECs), and allowed formation of monolayer cell sheet. In vitro translocation of HUVECs sheet could be obtained successively through phase transition of PD coated HBC hydrogel from gel to sol, and the cells sheet transferred from P30 hydrogel to a round cell coverglass maintained relatively complete monolayer and normal cell morphology. The results showed that P30 hydrogel has the potential to be used for cell transplantation therapy., (Copyright © 2018. Published by Elsevier B.V.)

This work targeted to investigate the potential of thermo-responsive hydroxybutyl chitosan (HBC) hydrogel using as an embolic material for occlusion of selective blood vessels. HBC hydrogel was prepared via an etherification reaction between chitosan (CS) and 1, 2-butene oxide. The hydroxybutyl groups were introduced into CS backbone, which endowed HBC hydrogel with properties of porous structure, favorable hydrophilia and rapid sol-gel interconvertibility. The gelation temperatures and gelation time respectively decreased from 30.7°C to 11.5°C and 79.60±3.19s to 7.70±1.42s at 37°C, with HBC solutions viscoelasticity increased from 3.0% to 7.0%. HBC hydrogel exhibited noncytotoxic to mouse embryo fibroblasts (MEFs) and excellent hemocompatibility with red blood cells (RBCs). After injection HBC solution into rat renal arteries, HBC solution transformed into hydrogel and attached onto blood vessel inner wall tightly, giving immediate blood vessels embolization. Meanwhile, RBCs could aggregate around HBC hydrogel to form moderate coagulation, which was beneficial to avoid hydrogel migration with blood flow. Above results suggested that HBC hydrogel could be applied as a promising embolic agent for hemorrage in the interventional vascular embolization field., (Copyright © 2017. Published by Elsevier B.V.)

The article focuses on a study which prepared chitosan-based thermosensitive hydrogels for drug delivery. Study authors showed how pH, ionic strength and CS/αΒ-GP ratio affect the thermosensitive characteristics, appearance and structure of the hydrogels. They concluded that chitosan-based thermosensitive hydrogels can be used in a sustained drug delivery system.

Abstract: A thermosensitive hydrogel has been prepared with chitosan and αβ-glycerophosphate (αβ-GP) which could be transited from solution into gel at 37°C. The thermosensitive characteristics, appearance and structure of the hydrogel were affected by concentration, molecular weight and degree of deacetylation (DD) of chitosan. Chitosan, MW 1360kDa, DD 75.4%, solution concentration 2% was optimal for preparation of chitosan-αβ-glycerophosphate (CS-αβ-GP) thermosensitive hydrogel. The appearance of the hydrogel became more compact and regular with increasing concentration and chitosan MW. Model drugs release from CS-αβ-GP hydrogel prepared by the drug being added into chitosan solution (method I) was slower than that from hydrogel prepared by the drug being directly added into chitosan hydrogel (method II).The release rate for both adriamycin and 6-mercaptopurine from CS-αβ-GP hydrogel decreased with the increase of MW of the chitosan. The hydrophilic model adriamycin was released 60–70% over 24h which was slower than that of the hydrophobic model 6-mercaptopurine. Therefore it was projected that the CS-αβ-GP hydrogel should be an ideal sustained release system especially for hydrophilic drugs. [Copyright &y& Elsevier]

The tumor microenvironment (TME) is characterized by low pH, hypoxia, and infiltrated tumor-associated macrophages (TAMs). Therefore, regulation of TAMs polarization into anti-tumor M1 phenotype and meanwhile alleviation of the hypoxia in TME are expected to improve anti-tumor therapeutic efficacy. To this end, a novel in situ injectable nano-complexed hydrogel was developed in this study for combining tumor therapy. Thereunto, hyaluronic acid modified transfersomes loaded with chlorogenic acid functioned to reverse M2 type into M1 type via CD44 mediated internalization, the nanomedicine was entrapped in Schiff-based crosslinked injectable hydrogel (fabricated with carboxymethyl chitosan and oxidized dextran) whose linkage was labile to the acidic TME for controlled drug release. Moreover, catalase was integrated in the hydrogel enabling to convert hydrogen peroxide in TME into dissolved oxygen and alleviate tumor hypoxia. The multifunctional nano-complexed injectable hydrogel was verified to efficiently inhibit tumor growth through synergetic effects of hypoxia alleviation and TAMs polarity regulation. [Display omitted] [ABSTRACT FROM AUTHOR]

• CtNWs are incorporated with Schiff base crosslinking Chitosan/Dextran based hydrogel. • CtNWs significantly strengthen the mechanical and adhesive properties of CD hydrogel. • CtNWs complexed CD hydrogel is non-toxic, antibacterial, degradable and hemostatic. • CtNWs complexed adhesive avoids severe postoperative adhesion and necrosis. Schiff base reaction crosslinking hydrogels are advantageous by rapid formation and absence of external crosslinkers. However, poor mechanical hindered their broader applications. Here, a mechanically strengthened tissue adhesive was constructed through incorporation of chitin nano-whiskers (CtNWs) with a Schiff base crosslinking hydrogel of carboxymethyl chitosan (CMCS) and dextran dialdehyde (DDA). The optimal formulation of complexed hydrogel exhibited 1.87 folds higher compressive stress than non-complexed and 1.51 time higher adhesive strength on porcine skin. The complexed hydrogel exhibited negligible cytotoxicity, anti-swelling performance in PBS, optimum antibacterial and hemostatic capacities. In vivo implantation studies confirmed the complexed hydrogel was degradable without long-term inflammatory responses. Desirable efficacy of injectable complexed hydrogel as hemostat was demonstrated in rat liver injury model, which could avoid severe postoperative adhesion and necrosis as observed in the treatment with commercial 3 M™ vetbond™ tissue adhesive. The results highlighted that the complexed hydrogel potentiated rapid hemostasis and wound repair applications. [ABSTRACT FROM AUTHOR]

• The composite hydrogel was prepared by thermo-crosslinking and photo-crosslinking. • The composite hydrogel displayed controlled and repeatable contraction property. • The composite hydrogel provided RGD motif to significantly enhance cell adhesion. • The cell-laden composite hydrogel could be applied for contraction fabrication. Stimuli-responsive gel volume variation is reversible and has shown promising applications, which may be potential for contraction or expansion fabrication, generating shrinking or swelling volume of the original. In this study, a thermo/photo dual-crosslinking hydrogel is prepared with methacrylated hydroxylbutyl chitosan (MHBC) and gelatin methacrylate (GelMA). The M/G hydrogel undergoes sol-gel phase transition under room temperature and shrinking deformation upon elevating temperature. Besides nontoxicity and biodegradability, dual crosslink endowed the composite hydrogel with strengthened and tunable mechanical property, controlled and repeatable contraction property in response to temperature elevation from 25 ℃ to 37 ℃, and enhanced cell adhesion in 3D culture. These peculiarities of M/G hydrogel provide great potential for application in contraction fabrication to acquire high resolution or small scale features that may be limited by fabrications devices. [ABSTRACT FROM AUTHOR]