Poly-Epsilon-Lysine Hydrogels with Dynamic Crosslinking Facilitates Cell Proliferation

Injectable pH- and Ultrasound-Responsive Dual-Crosslinked Dextran/Chitosan/TiO2 Nanocomposite Hydrogels for Antibacterial Applications

Combining exogenous and endogenous antibacterial mechanisms has been demonstrated to enhance therapeutic efficacy significantly. This study constructs an innovative type of exogenous and endogenous antibacterial nanocomposite hydrogels with injectable dual-crosslinked networks and dual-stimuli responsiveness. The primary network establishes imine bonds between the functionalized dextran featuring norbornenes and aldehydes (NorAld-Dex) and the quaternized chitosan (QCS). The imine bonds provide self-healing, injectability, and pH-responsiveness to the hydrogel network. The secondary network is established by integrating thiolated mesoporous silica-coated titanium dioxide nanoparticles (TiO2@MS-SH) into the hydrogel network via an ultrasound-activated thiol-norbornene reaction with NorAld-Dex. The microstructures and properties of NorAld-Dex/QCS/TiO2@MS-SH hydrogels can be fine-tuned by adjusting the sonication time to increase the amount of thiol-norbornene crosslinks in the network. Effective antibacterial performance of NorAld-Dex/QCS/TiO2@MS-SH hydrogels at low pH has been demonstrated with the synergistic effect of the acid-induced dissociation of the hydrogel network, protonated QCS, and the reactive oxygen species (ROS) generated by TiO2@MS-SH nanoparticles under ultrasound irradiation. In summary, NorAld-Dex/QCS/TiO2@MS-SH nanocomposite hydrogel is an advanced dual stimuli-responsive antibacterial platform with customizable microstructures and properties, offering great potential for biomedical applications.

Integrating Metabolic Oligosaccharide Engineering and SPAAC Click Chemistry for Constructing Fibrinolytic Cell Surfaces

To effectively solve the problem of significant loss of transplanted cells caused by thrombosis during cell transplantation, this study simulates the human fibrinolytic system and combines metabolic oligosaccharide engineering with strain-promoted azide-alkyne cycloaddition (SPAAC) click chemistry to construct a cell surface with fibrinolytic activity. First, a copolymer (POL) of oligoethylene glycol methacrylate (OEGMA) and 6-amino-2-(2-methylamido)hexanoic acid (Lys) was synthesized by reversible addition-fragmentation chain transfer (RAFT) copolymerization, and the dibenzocyclooctyne (DBCO) functional group was introduced into the side chain of the copolymer through an active ester reaction, resulting in a functionalized copolymer DBCO-PEG4-POL with ε-lysine ligands. Then, azide functional groups were introduced onto the surface of HeLa model cells through metabolic oligosaccharide engineering, and DBCO-PEG4-POL was further specifically modified onto the surface of HeLa cells via the SPAAC "click" reaction. In vitro investigations revealed that compared with unmodified HeLa cells, modified cells not only resist the adsorption of nonspecific proteins such as fibrinogen and human serum albumin but also selectively bind to plasminogen in plasma while maintaining good cell viability and proliferative activity. More importantly, upon the activation of adsorbed plasminogen into plasmin, the modified cells exhibited remarkable fibrinolytic activity and were capable of promptly dissolving the primary thrombus formed on their surfaces. This research not only provides a novel approach for constructing transplantable cells with fibrinolytic activity but also offers a new perspective for effectively addressing the significant loss of transplanted cells caused by thrombosis.

Aldehyde-mediated adaptive membranes with self-healing and antimicrobial properties for endometrial repair

Traditional treatment methods for irreversible endometrial damage face a number of challenges in clinical practice, the most important of which are bacterial infection and the inability to restore endometrial function. By modifying glucan, oxidized dextran (OD) with multifunctional aldehyde groups was obtained in this study. Based on the dynamic Schiff base reaction between gelatin (GA) and OD, a GA-OD adaptive membrane with good biocompatibility, self-healing, biodegradability, and antimicrobial properties was created. In vitro studies revealed that GA and OD cross-linking overcame GA's low gel temperature, accelerated gelling, and improved mechanical properties, hydrophilicity, and degradability. The dynamic bond formed by the reaction between GA and OD caused the GA-OD film to self-heal. Meanwhile, the GA-OD membrane had antibacterial properties. To assess the repair effect of GA-OD film, an in vivo rat endometrial injury model filled with GA-OD adaptive membrane was created. According to the results of the study, the GA-OD membrane was biocompatible, and the uterine tissue did not have edema and inflammation. Further study on the postoperative endometrial regeneration effect of GA-OD material showed that it had an excellent ability for epithelial reconstruction and cell proliferation. As a result, the use of GA-OD composite film in endometrial repair has promising therapeutic implications.

Shear-responsive boundary-lubricated hydrogels attenuate osteoarthritis

Lipid-based boundary layers formed on liposome-containing hydrogels can facilitate lubrication. However, these boundary layers can be damaged by shear, resulting in decreased lubrication. Here, a shear-responsive boundary-lubricated drug-loaded hydrogel is created by incorporating celecoxib (CLX)-loaded liposomes within dynamic covalent bond-based hyaluronic acid (HA) hydrogels (CLX@Lipo@HA-gel). The dynamic cross-linked network enables the hydrogel to get restructured in response to shear, and the HA matrix allows the accumulation of internal liposome microreservoirs on the sliding surfaces, which results in the formation of boundary layers to provide stable lubrication. Moreover, hydration shells formed surrounding the hydrogel can retard the degradation process, thus helping in sustaining lubrication. Furthermore, in vitro and in vivo experiments found that CLX@Lipo@HA-gels can maintain anabolic-catabolic balance, alleviate cartilage wear, and attenuate osteoarthritis progression by delivering CLX and shear-responsive boundary lubrication. Overall, CLX@Lipo@HA-gels can serve as shear-responsive boundary lubricants and drug-delivery vehicles to alleviate friction-related diseases like osteoarthritis.

Synthesis and Processing of Dynamic Covalently Crosslinked Polydextran/Carbon Dot Nanocomposite Hydrogels with Tailorable Microstructures and Properties

Using functionalized nanoparticles to crosslink hydrophilic polymers is a growing theme of directly constructing nanocomposite (NC) hydrogels. Employing dynamic covalent chemistry at the nanoparticle-polymer interface is particularly attractive due to the spontaneous formation and reversible manner of dynamic covalent bonds. However, the structure and property modulation of the dynamic covalently crosslinked NC hydrogels has not been thoroughly discussed. Here, we fabricated NC hydrogels by using amine-functionalized carbon dots (CDs) to crosslink polydextran aldehyde (PDA) polymers through imine bond formation. The role of PDA with different oxidation degrees (i.e., PDA10, PDA30, and PDA50) in affecting the microstructures and properties of PDA@CD hydrogels was systematically investigated, showing that the PDA50@CD hydrogel presented the densest structure and the highest mechanical strength among the three PDA@CD hydrogels. The pH-responsiveness, 3D printing, electrospinning, and biocompatibility of PDA@CD hydrogels were also demonstrated, showing the great promise of using PDA@CD hydrogels for applications in biomedicine and biofabrication.

Development of curcumin-loaded liposomes in lysine–collagen hydrogel for surgical wound healing

Background

A surgical wound is an incision made by a surgeon. Slow surgical wound healing may lead to chronic wounds which may be a potential health problem. The aim of this study is to formulate curcumin-loaded liposomes in lysine–collagen hydrogel for enhancing surgical wound healing. Curcumin-loaded liposomes were prepared using thin-film hydration method. The liposomal formulation was characterized by analysing its size, morphology, encapsulation efficiency, and in vitro release. The hydrogel base was prepared, and then, curcumin-loaded liposomes were infused to give formulation (F1). Curcumin-loaded liposomes were infused into the hydrogel base after which lysine and collagen were incorporated to give (F2), while (F3) comprised lysine and collagen incorporated in hydrogel base. All formulations were characterized by evaluation of the safety, stability, swelling index, pH, rheological properties, and in vivo wound healing assay. Histology and histomorphometry of tissue samples of wound area treated with formulations F1, F2, and F3 and the control, respectively, were examined.

Results

Curcumin-loaded liposomes were 5–10 µm in size, and the values for encapsulation efficiency and flux of the loaded liposomes are 99.934% and 51.229 µg/cm2/h, respectively. Formulations F1, F2, and F3 had a pH of 5.8. F1 had the highest viscosity, while F2 had the highest swelling index indications for efficient sustained release of drug from the formulation. The in vivo wound healing evaluation showed that curcumin-loaded liposomes in lysine–collagen hydrogel had the highest percentage wound contraction at 79.25% by day three post-surgical operation. Histological evaluation reflected a normal physiological structure of the layers of the epidermis and dermis after surgical wound healing in tissue samples from wound areas treated with formulations F1 and F2. The histomorphometrical values show highest percentage of collagen, lowest inflammatory rates, highest presence of microvessels, and re-epithelization rates at wound site in wounds treated with formulation F2 (curcumin-loaded liposomes in lysine–collagen hydrogel).

Conclusion

Curcumin-loaded liposomes in lysine–collagen hydrogel was found to be the most effective of the three formulations in promoting wound healing. Hence, this formulation can serve as a prototype for further development and has great potential as a smart wound dressing for the treatment of surgical wounds.

The role of aldehyde-functionalized crosslinkers on the property of chitosan hydrogels

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Use of biomaterials in corneal endothelial repair

Human corneal endothelium (HCE) is a single layer of hexagonal cells that lines the posterior surface of the cornea. It forms the barrier that separates the aqueous humor from the rest of the corneal layers (stroma and epithelium layer). This layer plays a fundamental role in maintaining the hydration and transparency of the cornea, which in turn ensures a clear vision. In vivo, human corneal endothelial cells (HCECs) are generally believed to be nonproliferating. In many cases, due to their nonproliferative nature, any damage to these cells can lead to further issues with Descemet’s membrane (DM), stroma and epithelium which may ultimately lead to hazy vision and blindness. Endothelial keratoplasties such as Descemet’s stripping automated endothelial keratoplasty (DSAEK) and Descemet’s membrane endothelial keratoplasty (DEK) are the standard surgeries routinely used to restore vision following endothelial failure. Basically, these two similar surgical techniques involve the replacement of the diseased endothelial layer in the center of the cornea by a healthy layer taken from a donor cornea. Globally, eye banks are facing an increased demand to provide corneas that have suitable features for transplantation. Consequently, it can be stated that there is a significant shortage of corneal grafting tissue; for every 70 corneas required, only 1 is available. Nowadays, eye banks face long waiting lists due to shortage of donors, seriously aggravated when compared with previous years, due to the global COVID-19 pandemic. Thus, there is an urgent need to find alternative and more sustainable sources for treating endothelial diseases, such as utilizing bioengineering to use of biomaterials as a remedy. The current review focuses on the use of biomaterials to repair the corneal endothelium. A range of biomaterials have been considered based on their promising results and outstanding features, including previous studies and their key findings in the context of each biomaterial.