A novel injectable thermo/photo dual-crosslinking hydrogel based on modified chitosan for fast sealing open globe injury

Open globe injuries (OGIs) demand immediate attention to prevent further complications and improve vision prognosis. Herein, we developed a thermo/photo dual-crosslinking injectable hydrogel, HBC_m_Arg, for rapidly sealing OGIs in emergency ophthalmic cases. HBC_m_Arg was prepared with arginine and methacrylic anhydride modified hydroxybutyl chitosan (HBC). HBC_m_Arg was initially in liquid form at 25 °C, enabling easy injection at the injury site. After reaching the ocular surface temperature, it underwent reversible heat-induced gelation to achieve in situ transformation. Further, HBC_m_Arg was capable of rapid photocrosslinking under UV light, forming a dual network structure to bolster mechanical strength, thereby facilitating effective OGI closure. Biocompatibility assessments, including in vitro studies with three ocular cell types and in vivo experiments on rabbit eyes, confirmed the safety profile of HBC_m_Arg. Ex vivo and in vivo burst pressure tests demonstrated the hydrogel's ability to promptly restore intraocular pressure and withstand elevated pressures, underscoring its potential for OGI stabilization. Additionally, the suitable degradation of HBC_m_Arg within ocular tissues, coupled with its stability in ex vivo assessments, presented a delicate balance between stability and biodegradability. In conclusion, HBC_m_Arg holds promise for improving emergency ophthalmic care by providing a rapid, effective, and safe way to seal OGIs in critical situations.

Acellular embryoid body and hydroxybutyl chitosan composite hydrogels promote M2 macrophage polarization and accelerate diabetic cutaneous wound healing

Diabetic wound healing is delayed due to persistent inflammation, and macrophage-immunomodulating biomaterials can control the inflammatory phase and shorten the healing time. In this study, acellular embryoid bodies (aEBs) were prepared and mixed with thermosensitive hydroxybutyl chitosan (HBC) hydrogels to produce aEB/HBC composite hydrogels. The aEB/HBC composite hydrogels exhibited reversible temperature-sensitive phase transition behavior and a hybrid porous network. In vitro analysis showed that the aEB/HBC composite hydrogels exhibited better antimicrobial activity than the PBS control, aEBs or HBC hydrogels and promoted M0 to M2 polarization but not M1 to M2 macrophage repolarization in culture. The in vivo results showed that the aEB/HBC composite hydrogels accelerated cutaneous wound closure, re-epithelialization, ingrowth of new blood vessels, and collagen deposition and reduced the scar width during wound healing in diabetic mice over time. Macrophage phenotype analysis showed that the aEB/HBC composite hydrogels induce M2 macrophage reactions continually, upregulate M2-related mRNA and protein expression and downregulate M1-related mRNA and protein expression. Therefore, the aEB/HBC composite hydrogels have excellent antimicrobial activity, promote M2 macrophage polarization and accelerate the functional and structural healing of diabetic cutaneous wounds.

Preparation and sustained-release mechanism of hydroxybutyl chitosan/graphene oxide temperature-sensitive hypoglycaemic subcutaneous implants

The current situation of diabetes prevention and control is extremely severe. For instance, glimepiride (GLM), a third-generation sulfonylurea, demonstrates suboptimal clinical efficacy in oral dosage forms, which underscores the pressing need for the development of a new dosage form. Recently, in situ gel subcutaneous implants have garnered considerable attention. Hydroxybutyl chitosan (HBC) can spontaneously crosslink to form a thermosensitive hydrogel and has good biocompatibility. However, its application is hindered by its limited mechanical properties. Graphene oxide (GO), known for its stable dispersion in water, can load GLM through π-π stacking interactions. When combined with HBC, GO enhances the mechanical properties and stability of the hydrogel. Therefore, an HBC-GO@GLM hydrogel was prepared. Rheological analysis revealed that the incorporation of GO increased the critical gelation temperature of the 5 wt% HBC hydrogel from 19.1°C to 27.2°C, considerably enhancing the mechanical properties of the hydrogel. Using encapsulation efficiency as an evaluation index, the optimal encapsulation efficiency of GO@GLM was determined to be 73.53% ± 0.45% with a drug loading capacity of 27.39 ± 0.17% using the Box-Behnken design model. Computer simulation technology validated the interaction between the materials and the drug release mechanism. Pharmacokinetic results showed that compared to the HBC@GLM group, the half-life (t1/2), mean residence time and the area under the curve for the HBC-GO@GLM group were approximately 3 times those of the HBC@GLM group. Subcutaneous implantation of the HBC-GO@GLM hydrogel for drug delivery considerably extended the drug's action time in the body, thereby maintaining blood sugar levels within a normal and stable range for an extended period.

Thermo-sensitive hydroxybutyl chitosan/diatom biosilica hydrogel with immune microenvironment regulatory for chronic wound healing

This study proposes a chronic wound therapeutic strategy based on extracellular matrix (ECM) biomimetics and immune regulation. The hydroxybutyl chitosan/diatom biosilica hydrogel (H/D) which can regulate the immune microenvironment, is prepared from hydroxybutyl chitosan (HBC) as matrix to construct the bionic ECM and diatom biosilica (DB) as structural active unit. The hierarchical porous structure of DB provides strong anchoring interface effect to enhance the mechanical strength of hydrogel, while maintaining its favorable temperature phase transition behavior, improving the material's fit to the wound and convenience of clinical use. Silicates released from DB in H/D accelerate the transition of wounds from inflammation to proliferation and remodeling. In cellular and diabetic rat models, H/D reduces inflammation (induces conversion of M1-type macrophages to M2-type), induces angiogenesis (1.96-fold of control), promotes fibroblast proliferation (180.36 % of control), collagen deposition, keratinocyte migration (47.34 % more than control), and re-epithelialization. This study validates a possible biological mechanism for H/D bioactive hydrogel-mediated regulation of the immune microenvironment and provides a simple synergistic dressing strategy.

Zinc-mineralized diatom biosilica/hydroxybutyl chitosan composite hydrogel for diabetic chronic wound healing

For sustained and stable improvement of the diabetic wound microenvironment, a temperature-sensitive composite hydrogel (ZnDBs/HBC) composed of inorganic zinc mineralized diatom biosilica (ZnDBs) and hydroxybutyl chitosan (HBC) was developed. The interfacial anchoring effect between ZnDBs and HBC enhanced the mechanical strength of the hydrogel. The mechanical strength of the composite hydrogel containing 3 wt% ZnDBs was increased by nearly 2.3times. The hydrogel can be used as a carrier for sustained release of Zn2+ for at least 72 h. In diabetic rats models, ZnDBs/HBC composite hydrogel could accelerate the inflammatory process by regulating the expression of pro-inflammatory factor IL-6 and anti-inflammatory factor IL-10, and also promote tissue cell proliferation and collagen deposition, thereby restoring the normal healing process and accelerating wound healing. The wound contraction rate of the composite hydrogel group was more than 2 times that of the control group. Therefore, ZnDBs/HBC composite hydrogel has the potential to be used as a therapeutic dressing for diabetic chronic wounds.

Emulsion stability of hydroxybutyl chitosan as emulsifier at low pH: Effects of the degree of substitutions of hydroxybutyl groups

Keeping the stability of emulsions at low pH is necessary for their successful applications in food and delivery systems. To achieve this goal, hydroxybutyl chitosan (HBC) with three degrees of substitution (DSs) was used as an emulsifier to investigate the effect of HBC structure on the emulsion stability. The DSs of HBC-5, HBC-10, and HBC-20 were 0.66, 1.51, and 2.19, respectively. The stability of oil-in-water emulsions against creaming/coalescence was positively correlated with the DS. As pH decreased to 2, HBC-20-stabilized emulsions were most stable without creaming or coalescence. After 30 days of storage, no changes in the droplet sizes of HBC-20-stabilized emulsions were observed, whereas the droplet sizes of HBC-5/10- stabilized emulsions significantly increased at low pH. The stability of HBC-20- stabilized emulsions at low pH was attributed to the higher surface activity and electrostatic repulsion. Our research revealed that the emulsion stability of HBC under low pH conditions can be controlled by the density of the hydroxybutyl groups in HBC. In vitro digestion further revealed the excellent stability of HBC-20-stabilized emulsions in simulated gastric fluid, which highlighted the enormous potential of HBC-20 to protect liposoluble drugs and nutrients from the extreme pH environment.

Hydrogel Production Platform with Dynamic Movement Using Photo-Crosslinkable/Temperature Reversible Chitosan Polymer and Stereolithography 4D Printing Technology

BACKGROUND

Three-dimensional (3D) printing using hydrogel has made great strides when it comes to mimicking 3D artificial tissue in the medical field. However, most structures do not mimic the dynamic movement of the tissues. Without imitating dynamic movements, there are limitations on the extent to which the proper implementation of the tissue's own functions can be achieved.

METHOD

In this study, we intend to present an approach to solving this problem using hydroxybutyl methacrylated chitosan (HBC-MA), a photo-crosslinkable/temperature reversible chitosan polymer. In addition, stereolithography-3D (SLA-3D) printing technology was used, which is more likely to mimic the complex microstructure. As a control, a 3D structure made with pristine poly(ethylene glycol) dimethacrylate (PEG-DMA) was created, and a 4D structure was prepared by adding HBC-MA to poly(ethylene glycol) dimethacrylate (PEG-DMAP) resin.

RESULTS

HBC-MA caused the expansion of water into the polymer matrix at low temperature, and the 4D structure resulted in expansion of the polymer volume, generating dynamic movement due to the expansion of water. Conversely, as the temperature rose, deswelling occurred, followed by a decrease in the volume, showing a shape memory property of returning to the existing structure. Morphological, swelling, and mechanical analysis further confirmed the principle of dynamic movement. In addition, parameters were provided through calculation of the bending ratio angle (θ).

CONCLUSION

Through this, it is suggested that HBC-MA can be applied as a core polymer for SLA-4D printing, and has high potential for realizing the dynamic movement of tissue.

Thermoresponsive polysaccharide-based composite hydrogel with antibacterial and healing-promoting activities for preventing recurrent adhesion after adhesiolysis

Postoperative adhesions are very common complications after general abdominal surgery. Although adhesiolysis has been proven effective in eliminating the preexisting adhesions, the new trauma caused by surgical lysis can induce recurrent adhesion. The prevention of recurrent adhesion after adhesiolysis is more difficult because the injury is more severe and adhesion mechanism is more complicated compared with the primary adhesion. In this study, a thermoresponsive hydrogel contained galactose modified xyloglucan (mXG) and hydroxybutyl chitosan (HBC) was developed as a barrier device for recurrent adhesion prevention after adhesiolysis due to its injectability and spontaneous gelling behaviors at the body temperature without any chemical reactions or extra driving factors. First, mXG and HBC were synthesized via enzymatic modification and etherification reaction, respectively. Rheological measurements indicated that the mXG/HBC composite system showed excellent thermosensitivity properties, and their gelation temperature and time can be modulated via adjusting the mXG/HBC ratio. Moreover, the mXG/HBC hydrogel exhibited excellent cytocompatibility and hemocompatibility in vitro. Furthermore, the mXG/HBC hydrogel could promote wound healing in the rat skin wound model. Finally, the efficacy of the mXG/HBC composite hydrogel in the prevention of recurrent adhesion was evaluated in a more rigorous rat repeated-injury adhesion model. The results demonstrated that the composite hydrogel could not only effectively prevent recurrent adhesion after adhesiolysis, but also promote wound healing and reduce scare formation. These results suggested that the mXG/HBC composite hydrogel may be a promising candidate as an injectable anti-adhesion system for clinical applications.

STATEMENT OF SIGNIFICANCE

Although adhesiolysis has been proven effective in eliminating the preexisting adhesions, the new trauma caused by surgical lysis can induce recurrent adhesion. So far, most of the existing barrier systems and pharmacological approaches were developed for primary adhesion prevention while few attention has paid on prevention of recurrent adhesion after adhesiolysis. In the present study, we developed a thermoresponsive polysaccharide-based composite hydrogel by simple mixing galactose modified xyloglucan (mXG) and hydroxybutyl chitosan (HBC). The resulting mXG/HBC composite hydrogel not only was easy to handle and highly effective in preventing the recurrent adhesion after adhesiolysis, but also could promote wound healing and reduce scare formation. Our study provide an effective anti-adhesion system for preventing recurrent adhesion after adhesiolysis.