Hydrogel-forming viscous liquid in response to ROS restores the gut mucosal barrier of colitis mice via regulating oxidative redox homeostasis

The disrupted oxidative redox homeostasis plays a critical role in the progress of ulcerative colitis (UC). Herein, hydrogel-forming viscous liquid (HSD) composed of cysteamine-grafted hyaluronic acid (HS) and superoxide dismutase (SOD) has been designed for UC. When the viscous HSD liquid was infused into colitis colon, SOD would convert the pathological superoxide (O2·-) to hydrogen peroxides (H2O2), which was subsequently scavenged by HS. Accordingly, the sol-gel transition of HSD was initiated by scavenging H2O2, enhancing its adhesion toward colitis colon. H2O2-treated HSD presented the higher storage modulus and stronger adhesion force toward porcine colon than the untreated HSD. Besides, H2O2-treated HSD presented the slower erosion profile in the colitis-mimicking medium (pH 3-5), while its rapid degradation was displayed in physiologic condition (pH7.4). The combination of pH-resistant erosion and ROS-responsive adhesion for HSD rendered it with the specifical retention on the inflamed colonic mucosa of DSS-induced colitis mice. Rectally administrating HSD could effectively hinder the body weight loss, reduce the disease activity index and improve the colonic shorting of DSS-induced colitis mice. Moreover, the pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) were substantially decreased, the colonic epitheliums were well rearranged and the tight junction proteins were greatly recovered after HSD treatment. Besides, HSD also modulated the gut flora, markedly augmenting the abundance of Firmicutes, Barnesiella and Lachnospiraceae. Moreover, HSD treatment could regulate oxidative redox homeostasis via activating Nrf2-HO-1 pathway to reduce ROS and malondialdehyde and upregulate antioxidant enzymes (SOD, GPx and GSH). Collectively, HSD might be a promising therapy for UC treatments. STATEMENT OF SIGNIFICANCE: Herein, a hydrogel-forming viscous liquid (HSD) was designed by cysteamine-grafted hyaluronic acid (HS) and superoxide dismutase (SOD) for UC treatments. When the viscous HSD liquid was infused into a colitis colon, SOD would convert the pathological superoxide to hydrogen peroxides (H2O2), which was subsequently scavenged by HS. Accordingly, the sol-gel transition of HSD was initiated by scavenging H2O2, enhancing its adhesion to the colitis colon. The colonic epitheliums of DSS-induced colitis mice were well rearranged and the tight junction proteins (Zonula-1 and Claudin-5) were greatly recovered after the HSD treatment. Moreover, the HSD treatment could regulate oxidative redox homeostasis via activating the Nrf2-HO-1 pathway to reduce ROS and malondialdehyde and upregulate antioxidant enzymes (SOD, GPx and GSH).

Fabrication of yeast β-glucan/sodium alginate/γ-polyglutamic acid composite particles for hemostasis and wound healing

Particles with a porous structure can lead to quick hemostasis and provide a good matrix for cell proliferation during wound healing. Recently, many particle-based wound healing materials have been clinically applied. However, these products show good hemostatic ability but with poor wound healing ability. To solve this problem, this study fabricated APGG composite particles using yeast β-glucan (obtained from Saccharomyces cerevisiae), sodium alginate, and γ-polyglutamic acid as the starting materials. The structure of yeast β-glucan was modified with many carboxymethyl groups to obtain carboxymethylated β-glucan, which could coordinate with Ca2+ ions to form a crosslinked structure. A morphology study indicated that the APGG particles showed an irregular spheroidal structure with a low density (<0.1 g cm-3) and high porosity (>40%). An in vitro study revealed that the particles exhibited a low BCI value, low hemolysis ratio, and good cytocompatibility against L929 cells. The APGG particles could quickly stop bleeding in a mouse liver injury model and exhibited better hemostatic ability than the commercially available product Celox. Furthermore, the APGG particles could accelerate the healing of non-infected wounds, and the expression levels of CD31, α-SMA, and VEGF related to angiogenesis were significantly enhanced.

Bioadhesive and Injectable Hydrogels and Their Correlation with Mesenchymal Stem Cells Differentiation for Cartilage Repair: A Mini-Review

Injectable bioadhesive hydrogels, known for their capacity to carry substances and adaptability in processing, offer great potential across various biomedical applications. They are especially promising in minimally invasive stem cell-based therapies for treating cartilage damage. This approach harnesses readily available mesenchymal stem cells (MSCs) to differentiate into chondrocytes for cartilage regeneration. In this review, we investigate the relationship between bioadhesion and MSC differentiation. We summarize the fundamental principles of bioadhesion and discuss recent trends in bioadhesive hydrogels. Furthermore, we highlight their specific applications in conjunction with stem cells, particularly in the context of cartilage repair. The review also encompasses a discussion on testing methods for bioadhesive hydrogels and direct techniques for differentiating MSCs into hyaline cartilage chondrocytes. These approaches are explored within both clinical and laboratory settings, including the use of genetic tools. While this review offers valuable insights into the interconnected aspects of these topics, it underscores the need for further research to fully grasp the complexities of their relationship.

From the updated landscape of the emerging biologics for IBDs treatment to the new delivery systems

Inflammatory bowel diseases (IBDs) treatments have shifted from small-molecular therapeutics to the oncoming biologics. The first-line biologics against the moderate-to-severe IBDs are mainly involved in antibodies against integrins, cytokines and cell adhesion molecules. Besides, other biologics including growth factors, antioxidative enzyme, anti-inflammatory peptides, nucleic acids, stem cells and probiotics have also been explored at preclinical or clinical studies. Biologics with variety of origins have their unique potentials in attenuating immune inflammation or gut mucosa healing. Great advances in use of biologics for IBDs treatments have been archived in recent years. But delivering issues for biologic have also been confronted due to their liable nature. In this review, we will focus on biologics for IBDs treatments in the recent publications; summarize the current landscapes of biologics and their promise to control disease progress. Alternatively, the confronted challenges for delivering biologics will also be analyzed. To combat these drawbacks, some new delivering strategies are provided: firstly, designing the functional materials with high affinity toward biologics; secondly, the delivering vehicle systems to encapsulate the liable biologics; thirdly, the topical adhering delivery systems as enema. To our knowledge, this review is the first study to summarize the updated usage of the oncoming biologics for IBDs, their confronted challenges in term of delivery and the potential combating strategies.

Antibacterial Conductive Collagen-Based Hydrogels for Accelerated Full-Thickness Wound Healing

Antibacterial conductive hydrogels have been extensively utilized in tissue repair and regeneration on account of their unique electrochemical performances and advantages of anti-pathogenic bacterial infection. Here, multi-functional collagen-based hydrogels (CHLY) with adhesivity, conductivity, and antibacterial and antioxidant activities were developed by introducing cysteine-modified ε-poly(l-lysine) (ε-PL-SH) and in situ-polymerized polypyrrole (PPy) nanoparticles to induce full-thickness wound healing. CHLY hydrogels have a low swelling ratio, good compressive strength, and viscoelasticity due to chemical crosslinking, chelation, physical interaction, and nano-reinforcements in the matrix network of hydrogels. CHLY hydrogels possess excellent tissue adhesion ability, low cytotoxicity, enhanced cell migration ability, and good blood coagulation performance without causing hemolysis. Interestingly, the chemical conjugation of ε-PL-SH in the hydrogel matrix gives hydrogels an inherently robust and broad-spectrum antibacterial activity, while the introduction of PPy endows hydrogels with superior free radical scavenging capacity and good electroactivity. Significantly, CHLY hydrogels have advantages in alleviating persistent inflammatory response as well as promoting angiogenesis, epidermis regeneration, and orderly collagen deposition at the wound sites through their multi-functional synergies, thus effectively accelerating full-thickness wound healing and improving wound healing quality. Overall, our developed multi-functional collagen-based hydrogel dressing demonstrates promising application prospects in the field of tissue engineering to induce skin regeneration.

In situ polyphenol-adhesive hydrogel enhanced the noncarcinogenic repairing of KGF on the gut epithelial barrier on TNBS-induced colitis rats

Ulcerative colitis (UC) is a chronic recurrent disease affecting the gastrointestinal tract especially colorectum. Keratinocyte growth factor (KGF) plays the vital roles in maintaining the colonic mucosal barrier. The poor stability and off-target of KGF were two hindering factors for its clinical application. Herein, in situ hydrogel (PE) with mucoadhesive ability was constructed by using temperature-sensitive poloxamer and EGCG as hydrogel-forming material and adhesive enhancer, respectively. Incorporation of EGCG led to the slight decrease of the gelled temperature and shortened the gelled time of PE hydrogel. When the concentration of EGCG is 0.1 %, PE hydrogel exhibits the suitable viscosity of 280 ± 20 Pa·s and the strong adhesive force of 725 ± 25 mN. KGF was soluble in cold PE solution to obtain KGF-loaded PE hydrogel (KGF@PE). PE hydrogel could improve the stability of KGF in vitro. KGF@PE not only could recover greatly the body weight of TNBS-induced rats but also repair their colonic morphology and goblet cell function. Moreover, the potential of repairing the epithelial barrier was indicated by upregulating tight junction proteins. Importantly, the safety of KGF@PE hydrogel for colitis was also confirmed on AOM/DSS-induced mice models. Conclusively, KGF@PE may be a promising therapeutic platform without obvious side effect for ulcerative colitis.

Polyphenol-driven facile assembly of a nanosized acid fibroblast growth factor-containing coacervate accelerates the healing of diabetic wounds

Diabetic wounds are challenging to heal due to complex pathogenic abnormalities. Routine treatment with acid fibroblast growth factor (aFGF) is widely used for diabetic wounds but hardly offers a satisfying outcome due to its instability. Despite the emergence of various nanoparticle-based protein delivery approaches, it remains challenging to engineer a versatile delivery system capable of enhancing protein stability without the need for complex preparation. Herein, a polyphenol-driven facile assembly of nanosized coacervates (AE-NPs) composed of aFGF and Epigallocatechin-3-gallate (EGCG) was constructed and applied in the healing of diabetic wounds. First, the binding patterns of EGCG and aFGF were predicted by molecular docking analysis. Then, the characterizations demonstrated that AE-NPs displayed higher stability in hostile conditions than free aFGF by enhancing the binding activity of aFGF to cell surface receptors. Meanwhile, the AE-NPs also had a powerful ability to scavenge reactive oxygen species (ROS) and promote angiogenesis, which significantly accelerated full-thickness excisional wound healing in diabetic mice. Besides, the AE-NPs suppressed the early scar formation by improving collagen remodeling and the mechanism was associated with the TGF-β/Smad signaling pathway. Conclusively, AE-NPs might be a potential and facile strategy for stabilizing protein drugs and achieving the scar-free healing of diabetic wounds. STATEMENT OF SIGNIFICANCE: Diabetic chronic wound is among the serious complications of diabetes that eventually cause the amputation of limbs. Herein, a polyphenol-driven facile assembly of nanosized coacervates (AE-NPs) composed of aFGF and EGCG was constructed. The EGCG not only acted as a carrier but also possessed a therapeutic effect of ROS scavenging. The AE-NPs enhanced the binding activity of aFGF to cell surface receptors on the cell surface, which improved the stability of aFGF in hostile conditions. Moreover, AE-NPs significantly accelerated wound healing and improved collagen remodeling by regulating the TGF-β/Smad signaling pathway. Our results bring new insights into the field of polyphenol-containing nanoparticles, showing their potential as drug delivery systems of macromolecules to treat diabetic wounds.

Injectable polylysine and dextran hydrogels with robust antibacterial and ROS-scavenging activity for wound healing

Cutaneous wound management remains a major concern due to uncontrolled inflammation and bacterial infection in clinical care. A desirable hydrogel dressing with antibacterial and antioxidative properties can drive wound healing by inhibiting infection and inflammation. Herein, a multifunctional hydrogel based on polylysine-graft-cysteine (EPL-SH)/oxidized dextran (ODex) was fabricated for promoting skin tissue regeneration. The engineered hydrogel possessed versatile properties including tunable gelation time (60-300 s), typical rheological behavior, suitable swelling and degradation progress, injectable and self-healing ability. The unique hydrogels also displayed promising tissue adhesiveness, high cell affinity, excellent antioxidant and antimicrobial activity. Furthermore, the in vivo full-thickness skin defect experiment demonstrated the simple-to-implement injectable hydrogels could significantly promoting wound healing by improving the collagen deposition and angiogenesis. The manufacture of our multifunctional hydrogels dressing affords a new strategy for improving efficacy of cutaneous wound treatment.

A methacrylated hyaluronic acid network reinforced Pluronic F-127 gel for treatment of bacterial keratitis

In this study, we developed a novel in situ thermoresponsive gel by introducing crosslinked methacrylated hyaluronic acid (HA-MA) networks into Pluronic F-127 (PF-127) gel (HP gel) to achieve levofloxacin (LFX) delivery in bacterial keratitis treatment. The interactions between PF-127 and HA-MA networks were studied by scanning electron microscopy, rheology, dynamic light scattering, differential scanning calorimetry, and small angle X-ray scattering. The results showed that the HP gel exhibited a higher critical gelling temperature and lower viscosity than the PF-127 gel (P gel), and could form a uniform thin layer on the ocular surface. Moreover, the drug release profile and gel dissolution rate revealed that the HA-MA network could retard the diffusion and dissolution of drug molecules and prolong the drug release time, which corresponded to an enhanced antibacterial ability of the HP-LFX gel. Furthermore, the HP gel exhibited low cytotoxicity to human corneal epithelial cells (HCECs). Finally, an in vivo pharmacodynamic study was conducted with rabbit keratitis models. An improved treatment efficacy was observed after application of the HP-LFX gels. This study highlights the potential of HP gels in ophthalmic drug delivery.

A KPV-binding double-network hydrogel restores gut mucosal barrier in an inflamed colon

Ulcerative colitis (UC) usually occurs in the superficial mucosa of the colorectum. Here, a double-network hydrogel (PMSP) was constructed from maleimided γ-polyglutamic acid and thiolated γ-polyglutamic acid through crosslinking of thiol-maleimide and self-oxidized thiols. PMSP with a negative charge specifically adhered to the inflamed mucosa with positively charged proteins rather than to the healthy mucosa. PMSP exhibited good mechanical strength with storage modulus (G') of 17.6 Pa and a linear viscoelastic region (LVR) of 107.2% strain. Moreover, PMSP showed a stronger bio-adhesive force toward the inflamed tissue-mimicking substrate than toward its healthy counterpart. In vivo imaging confirmed that PMSP specifically adhered to the inflamed colonic mucosa of rats with TNBS-induced UC. KPV (Lys-Pro-Val) as a model drug was easily captured by PMSP through electrostatic interactions, thus retaining its bioactivity for a longer time under high temperature conditions. Moreover, the alleviating effect of KPV on rats with TNBS-induced colitis was significantly improved by PMSP after intracolonic administration. The epithelial barrier of the colon also effectively recovered following PMSP-KPV treatment. PMSP-KPV also modulated the gut flora, markedly augmenting the abundance of beneficial microorganisms in gut homeostasis. The mechanism by which PMSP-KPV induces a therapeutic effect may be associated with the inhibition of oxidative stress. Conclusively, the PMSP hydrogel seems to be a promising rectal delivery system for the therapy of UC. STATEMENT OF SIGNIFICANCE: Ulcerative colitis (UC) is a chronic and relapsing disease of the gastrointestinal tract. A key therapeutic approach to treat UC is to repair the mucosal barriers. Here, a double-network hydrogel (PMSP) was constructed from maleimided and thiolated γ-polyglutamic acid through crosslinking of thiol-maleimide and self-oxidized thiols. The negatively charged PMSP specifically adhered to the inflamed colon rather than its healthy counterpart and was retained for a longer time. KPV as a model drug was easily captured by PMSP, which provided better stability to KPV when exposed to high temperature of 50 °C. The epithelial mucosal barrier of the colon was effectively recovered by the rectal administration of PMSP-KPV to rats with TNBS-induced UC. Moreover, PMSP-KPV modulated the gut flora of colitic rats, markedly augmenting the abundance of beneficial microorganisms. Conclusively, PMSP seems to be a promising rectal delivery system for UC therapy.

Mechanoadaptive injectable hydrogel based on poly(γ-glutamic acid) and hyaluronic acid regulates fibroblast migration for wound healing

Injectable hydrogels have shown therapeutic effects on wound repair, but most of them exhibit poor mechanical strength. The impacts of stiff injectable hydrogels on cell behavior and wound healing remain unclear. Herein, an injectable hydrogel was developed based on thiolated poly(γ-glutamic acid) (γ-PGA-SH) and glycidyl methacrylate-conjuated oxidized hyaluronic acid (OHA-GMA). Thiol-methacrylate Michael chemistry-mediated post-stabilization and increase of polymer concentration were found to improve the mechanical strength of γ-PGA-SH/OHA-GMA hydrogel. Moreover, in vitro studies confirmed its biodegradability, biocompatibility, and self-healing property. Using the mechanically-tunable hydrogel, it further showed that fibroblasts migrated faster on the surface of stiffer hydrogel, but infiltrated slowly inside it compared with softer hydrogel. In animal experiments, the injectable hydrogel could promote wound healing by increasing collagen deposition and vascularization. In summary, γ-PGA-SH/OHA-GMA hydrogel is able to regulate migration and infiltration of fibroblasts by altering stiffness and offers effective in situ forming scaffolds towards skin tissue regeneration.

Bioadhesive hydrogel comprising bilirubin/β-cyclodextrin inclusion complexes promote diabetic wound healing

CONTEXT

Chronic non-healing diabetic wound therapy is an important clinical challenge. Manipulating the release of bioactive factors from an adhesive hydrogel is an effective approach to repair chronic wounds. As an endogenous antioxidant, bilirubin (BR) has been shown to promote wound healing. Nonetheless, its application is limited by its low water solubility and oxidative degradation.

OBJECTIVE

This study developed a bilirubin-based formulation for diabetic wound healing.

MATERIALS AND METHODS

Bilirubin was incorporated into β-CD-based inclusion complex (BR/β-CD) which was then loaded into a bioadhesive hydrogel matrix (BR/β-CD/SGP). Scratch wound assays were performed to examine the in vitro pro-healing activity of BR/β-CD/SGP (25 μg/mL of BR). Wounds of diabetic or non-diabetic rats were covered with BR or BR/β-CD/SGP hydrogels (1 mg/mL of BR) and changed every day for a period of 7 or 21 days. Histological assays were conducted to evaluate the in vivo effect of BR/β-CD/SGP.

RESULTS

Compared to untreated (18.7%) and BR (55.2%) groups, wound closure was more pronounced (65.0%) in BR/β-CD/SGP group. In diabetic rats, the wound length in BR/β-CD/SGP group was smaller throughout the experimental period than untreated groups. Moreover, BR/β-CD/SGP decreased TNF-α levels to 7.7% on day 3, and elevated collagen deposition and VEGF expression to 11.9- and 8.2-fold on day 14. The therapeutic effects of BR/β-CD/SGP were much better than those of the BR group. Similar observations were made in the non-diabetic model.

DISCUSSION AND CONCLUSION

BR/β-CD/SGP promotes wound healing and tissue remodelling in both diabetic and non-diabetic rats, indicating an ideal wound-dressing agent.

Self-Cross-Linked Hydrogel of Cysteamine-Grafted γ-Polyglutamic Acid Stabilized Tripeptide KPV for Alleviating TNBS-Induced Ulcerative Colitis in Rats

KPV (Lys-Pro-Val), which is a tripeptide derived from α-MSH (α-melanocyte-stimulating hormone), has an anti-inflammatory effect on colitis. However, KPV solution is very unstable when rectally administered, compromising its therapeutic efficacy. Herein, cysteamine-grafted γ-polyglutamic acid (SH-PGA) was synthesized by conjugating cysteamine with the carboxyl groups of γ-PGA. The synthesized SH-PGA has the thiol grafting amount of 4.5 ± 0.3 mmol/g. Without the use of the cross-linker, the SH-PGA hydrogel with 4% of the polymer was formed by self-cross-linking of thiol groups. Moreover, the formation of the SH-PGA hydrogel was not affected by KPV. The KPV/SH-PGA hydrogel presented higher elastic modulus (G') than the corresponding viscous modulus (G″) at 0.01-10 Hz, exhibiting good mechanical stability. The KPV/SH-PGA hydrogel presented a shear-thinning behavior, which was helpful for rectal administration. Only 30% of KPV was released from the KPV/SH-PGA hydrogel within 20 min, followed by a sustained-release behavior. Importantly, the stability of KPV in the SH-PGA hydrogel was obviously enhanced, which was presented by detecting its anti-inflammatory activity and promoting cell migration potential after 2 h of exposure to 37 °C. The enhanced therapeutic effect of the KPV/SH-PGA hydrogel on colitis was confirmed on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced ulcerative colitis rats. The colitis symptoms including body weight loss and the disease activity index score were obviously attenuated by rectally administering the KPV/SH-PGA hydrogel. Besides, the KPV/SH-PGA hydrogel treatment prevented the colon shortening of TNBS-infused rats and decreased the colonic myeloperoxidase level. The morphology of the colon including the epithelial barrier, crypt, and intact goblet cells was recovered after KPV/SH-PGA hydrogel treatment. Besides, the KPV/SH-PGA hydrogel decreased the expression of proinflammatory cytokines such as tumor necrosis factor α and interleukin 6. Collectively, the KPV/SH-PGA hydrogel may provide a promising strategy for the treatment of ulcerative colitis.

Injectable adaptive self-healing hyaluronic acid/poly (γ-glutamic acid) hydrogel for cutaneous wound healing

The most significant challenge in designing wound dressings is to mimic the tissue microenvironment because of the pro-regenerative structural and functional properties of skin. Herein, we developed a type of bionic extracellular matrix (ECM) hydrogels based on thiol-modified poly (γ-glutamic acid) (γ-PGA-SH) and oxidized hyaluronic acid (HA-CHO). The rapid and reversible thiol-aldehyde addition reaction of thiols in γ-PGA-SH and aldehyde groups in HA-CHO provided hydrogels with a dynamic covalent network and endowed them with properties of adaptability and self-healing capability, which are conducive for initial wound coverage and for prolonging the lifespan of the dressing. Interestingly, these hydrogels also showed typical viscoelastic characteristics similar to those of natural ECM, degradation property in vitro and in vivo, and free radical scavenging capability. In addition, the gelation time, rheological behavior, mechanical property, porous structure, and degradation process of the hydrogels could be tuned by adjusting polymer content. Furthermore, the ECM-inspired hydrogels significantly enhanced the wound healing process in vivo in a full-thickness skin defect model compared to those by commercial dressing (Tegaderm™) by facilitating angiogenesis and promoting collagen deposition. The successful application of the multifunctional hydrogel as an antioxidant wound dressing for wound treatment significantly exhibited its great application potential for biomedical areas. STATEMENT OF SIGNIFICANCE: The application of tissue engineering techniques to repair full-thickness skin wounds remains a great challenge in clinical trials. Among the recent approaches used for wound healing, in situ forming injectable hydrogels have gained much attention, and few of them have shown satisfactory overall performance, such as integration into the wound bed, biodegradability, immunocompatibility, vascularization, and recapitulation of the structure and function of skin. In the present study, we designed a simple and convenient in situ forming injectable adaptable self-healing hydrogels with biodegradability and antioxidative properties, which could substantially improve wound healing quality at an affordable cost. The hydrogel-based wound dressing is expected to solve the abovementioned problems and help in promoting cutaneous wound healing.

Hyaluronic acid coated bilirubin nanoparticles attenuate ischemia reperfusion-induced acute kidney injury

Acute kidney injury (AKI) is a common pathological process that is globally associated with a high morbidity and mortality rate. The underlying AKI mechanisms include over-produced reactive oxygen species (ROS), inflammatory cell infiltration, and high levels of inflammatory mediators. Bilirubin is an endogenous compound with antioxidant, anti-inflammatory and anti-apoptotic properties, and could, therefore, be a promising therapeutic candidate. Nanotechnology-mediated therapy has emerged as a novel drug delivery strategy for AKI treatment. In this study, we report a hyaluronic acid (HA) coated ε-polylysine-bilirubin conjugate (PLBR) nanoparticle (nHA/PLBR) that can selectively accumulate in injured kidneys and alleviate the oxidative/inflammatory-induced damage. The in vitro study revealed that nHA/PLBR has good stability, biocompatibility, and exhibited higher antioxidant as well as anti-apoptotic effects when compared to nPLBR or bilirubin. The in vivo study showed that nHA/PLBR could target and accumulate in the injured kidney, effectively relieve oxidative stress and inflammatory reactions, protect the structure and function of the mitochondria, and more importantly, inhibit the apoptosis of tubular cells in an ischemia/reperfusion-induced AKI rat model. Therefore, nHA/PLBR has the capacity to enhance specific biodistribution and delivery efficiency of bilirubin, thereby providing better treatment for AKI in the future.

Glucose-responsive hydrogel enhances the preventive effect of insulin and liraglutide on diabetic nephropathy of rats

Diabetic nephropathy (DN) is one of the most serious complications of diabetes mellitus. The combination of insulin (Ins) with liraglutide (Lir) has a greater potential for preventing DN than monotherapy. However, the renal protective effect of the combined Ins/Lir therapy is largely compromised due to their short half-lives after subcutaneous injection. Herein, a glucose-responsive hydrogel was designed in situ forming the dynamic boronic esters bonds between phenylboronic acid-grafted γ-Polyglutamic acid (PBA-PGA) and konjac glucomannan (KGM). It was hypothesized that the KGM/PBA-PGA hydrogel as the delivery vehicle of Ins/Lir would enhance the combinational effect of the latter on preventing the DN progress. Scan electronic microscopy and rheological studies showed that KGM/PBA-PGA hydrogel displayed good glucose-responsive property. Besides, the glucose-sensitive release profile of either Ins or Lir from KGM/PBA-PGA hydrogel was uniformly displayed at hyperglycemic level. Furthermore, the preventive efficacy of KGM/PBA-PGA hydrogel incorporating insulin and liraglutide (Ins/Lir-H) on DN progress was evaluated on streptozotocin-induced rats with diabetic mellitus (DM). At 6 weeks after subcutaneous injection of Ins/Lir-H, not only the morphology of kidneys was obviously recovered as shown by ultrasonography, but also the renal hemodynamics was significantly improved. Meanwhile, the 24-h urinary protein and albumin/creatinine ratio were well modulated. Inflammation and fibrosis were also largely inhibited. Besides, the glomerular NPHS-2 was obviously elevated after treatment with Ins/Lir-H. The therapeutic mechanism of Ins/Lir-H was highly associated with the alleviation of oxidative stress and activation of autophagy. Conclusively, the better preventive effect of the combined Ins/Lir via KGM/PBA-PGA hydrogel on DN progress was demonstrated as compared with their mixed solution, suggesting KGM/PBA-PGA hydrogel might be a potential vehicle of Ins/Lir to combat the progression of DN.

Tissue Adhesives: From Research to Clinical Translation

Sutures, staples, clips and skin closure strips are used as the gold standard to close wounds after an injury. In spite of being the present standard of care, the utilization of these conventional methods is precarious amid complicated and sensitive surgeries such as vascular anastomosis, ocular surgeries, nerve repair, or due to the high-risk components included. Tissue adhesives function as an interface to connect the surfaces of wound edges and prevent them from separation. They are fluid or semi-fluid mixtures that can be easily used to seal any wound of any morphology - uniform or irregular. As such, they provide alternatives to new and novel platforms for wound closure methods. In this review, we offer a background on the improvement of distinctive tissue adhesives focusing on the chemistry of some of these products that have been a commercial success from the clinical application perspective. This review is aimed to provide a guide toward innovation of tissue bioadhesive materials and their associated biomedical applications.

3D Printable, Modified Trephine Designs for Consistent Anterior Lamellar Keratectomy Wounds in Rabbits

PURPOSE

Our goal is to develop a low-cost tool that can be used to create consistent, partial-thickness defects in rabbit and other large animals with minimal surgical training and that can facilitate pre-clinical testing of lamellar and in situ-forming biosynthetic matrix materials for corneal repair.

MATERIALS & METHODS

In this study, three modified trephines were designed to create deep corneal wound defects with consistent depth in large animals. The modified trephines incorporated either 3D-printed parts made from photopolymerizable resins, or custom-cut commercially available Teflon sheets. Wound defects were imaged with optical coherence tomography (OCT), and the depth was analyzed based on the OCT images.

RESULTS

The results revealed that an inner-stopper guard trephine had the best performance in creating consistent and precise wound defect depth compared to modified vacuum trephine and custom guard vacuum trephine. A 75% ± 10% cut of the cornea was achieved with the inner-stopper guard trephine. The wound defect depth by created by the inner-stopper guard trephine was independent of the corneal thickness or size of the globes. Although the cut depth of the inner-stopper guard trephine differed by the experience-level of its users, the consistency (standard deviation) of the depth was independent of experience.

CONCLUSIONS

Our studies provided three cost-efficient animal trephines that can create corneal wounds of consistent depth by lab researchers without extensive training in keratectomy.

HA/MgO nanocrystal-based hybrid hydrogel with high mechanical strength and osteoinductive potential for bone reconstruction in diabetic rats

Bone repair and regeneration processes are markedly impaired in diabetes mellitus (DM). Intervening approaches similar to those developed for normal healing conditions have been adopted to combat DM-associated bone regeneration. However, limited outcomes were achieved for these approaches. Hence, together with osteoconductive hydroxyapatite (HA) nanocrystals, osteoinductive magnesium oxide (MgO) nanocrystals were uniformly mounted into the network matrix of an organic hydrogel composed of cysteine-modified γ-polyglutamic acid (PGA-Cys) to construct a hybrid and rough hydrogel scaffold. It was hypothesized that the HA/MgO nanocrystal hybrid hydrogel (HA/MgO-H) scaffold can significantly promote bone repair in DM rats via the controlled release of Mg²⁺. The HA/MgO-H scaffold exhibited a sponge-like morphology with porous 3D networks inside it and displayed higher mechanical strength than a PGA-Cys scaffold. Meanwhile, the HA/MgO-H scaffold gradually formed a tough hydrogel with G' of more than 1000 Pa after hydration, and its high hydration swelling ratio was still retained. Moreover, after the chemical degradation of the dispersed MgO nanocrystals, slow release of Mg²⁺ from the hydrogel matrix was achieved for up to 8 weeks because of the chelation between Mg²⁺ and the carboxyl groups of PGA-Cys. In vitro cell studies showed that the HA/MgO-H scaffold could not only effectively promote the migration and proliferation of BMSCs but could also induce osteogenic differentiation. Moreover, in the 8th week after implanting the HA/MgO-H scaffold into femur bone defect zones of DM rats, more effective bone repair was presented by micro-CT imaging. The bone mineral density (397.22 ± 16.36 mg cm^-3), trabecular thickness (0.48 ± 0.07 mm), and bone tissue volume/total tissue volume (79.37 ± 7.96%) in the HA/MgO-H group were significantly higher than those in the other groups. Moreover, higher expression of COL-I and OCN after treatment with HA/MgO-H was also displayed. The bone repair mechanism of the HA/MgO-H scaffold was highly associated with reduced infiltration of pro-inflammatory macrophages (CD80⁺) and higher angiogenesis (CD31⁺). Collectively, the HA/MgO-H scaffold without the usage of bioactive factors may be a promising biomaterial to accelerate bone defect healing under diabetes mellitus.

Simultaneous Interpenetrating Polymer Network of Collagen and Hyaluronic Acid as an In Situ-Forming Corneal Defect Filler

Timely treatment of corneal injuries injury can help to prevent corneal scarring, blindness, and the need for corneal transplantation. This work describes a novel hydrogel that can fill corneal defects and assist in corneal regeneration. This hydrogel is a simultaneous interpenetrating polymer network (IPN) composed of collagen cross-linked via strain-promoted azide-alkyne cycloaddition reaction and hyaluronic acid cross-linked via thiol-ene Michael click reaction. The formation of the IPN gel was confirmed via FTIR spectra, UV-vis spectra, and morphological changes. We compared the gelation time, mechanical properties, transmittance, and refractive index of the IPN gel to the collagen gel, hyaluronic acid gel, and semi-IPN gel. The IPN combined the advantages of collagen and hyaluronic acid gels and supported corneal epithelial cell growth on its surface. When applied to corneal stromal defects in vivo, the IPN avoided epithelial hyperplasia, decreased stromal myofibroblast formation, and increased tight junction formation in the regenerated epithelium.

Development of mucoadhesive cationic polypeptide micelles for sustained cabozantinib release and inhibition of corneal neovascularization

Corneal neovascularization (CNV) is one of the leading risk factors for vision loss. Anti-angiogenic drugs can theoretically be extended to the treatment of CNV. However, the application of these drugs is often hindered by traditional administration methods, e.g., eye drops, which is ascribed to the unique structure of the cornea and tear film. In this study, cationic polypeptide nanoparticles with mucoadhesive ability that carry lipophilic cabozantinib (a tyrosine kinase inhibitor), called Cabo-NPs, were developed for sustained cabozantinib release and inhibition of CNV. The polypeptides were synthesized via N-carboxyanhydride ring-opening polymerization and could self-assemble into micelles with cabozantinib in aqueous solution. The Cabo-NPs possessed good biocompatibility both in corneal epithelial cells and mouse corneas. More importantly, in vitro angiogenesis assays demonstrated the strong inhibitory effect of Cabo-NPs on cell migration and tube formation. Furthermore, the Cabo-NPs exerted superior anti-angiogenic effects with remarkable reductions in the neovascular area, which were as effective as the clinical dexamethasone but without apparent side effects. The therapeutic mechanism of the Cabo-NPs is closely related to the significant decrease in proangiogenic and proinflammatory factors, suppressing neovascularization and inflammation. Overall, cationic Cabo-NPs offer a new prospect for safe and effective CNV treatment via enhancing the bioavailability of lipophilic cabozantinib.

Long-term delivery of alendronate through an injectable tetra-PEG hydrogel to promote osteoporosis therapy

Pharmacotherapy for hypercalcemia, which is mainly caused by osteoporosis, is an effective method to regulate the in vivo calcium equilibrium. From this perspective, the development of a minimally invasive gelling system for the prolonged local delivery of bisphosphonates has practical significance in the clinical therapy of bone osteoporosis. Here, a biocompatible and injectable hydrogel based on a uniform tetra-PEG network carrying a PEG-modified alendronate (ALN) prodrug for the localized elution and long-term sustained release of anti-osteoporotic small molecule drugs is reported. The obtained ALN-based tetra-PEG hydrogels exhibit rapid gel formation and excellent injectability, thereby allowing for the easy injection and consequent adaptation of hydrogels into the bone defects with irregular shapes, which promotes the ALN-based tetra-PEG hydrogels with depot formulation capacity for governing the on-demand release of ALN drugs and local reinforcement of bone osteoporosis at the implantation sites of animals. The findings imply that these injectable hydrogels mediate the optimized release of therapeutic cargoes and effectively promote in situ bone regeneration via minimally invasive procedures, which is effective for clinical osteoporosis therapy.

Progress in Research on the Role of FGF in the Formation and Treatment of Corneal Neovascularization

Corneal neovascularization (CNV) is a sight-threatening disease usually associated with inflammatory, infectious, degenerative, and traumatic disorders of the ocular surface. Fibroblast growth factor (FGF) family members play an important role in angiogenesis to induce corneal neovascularization, which significantly affects the differentiation, proliferation, metastasis, and chemotaxis of vascular endothelial cells. Both acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF) demonstrate positive staining in capillaries and induce corneal stromal cells. The anabolism of endothelial cells is induced by bFGF in corneal neovascularization. FGFs exert their effects via specific binding to cell surface-expressed specific receptors. We believe that both anti-FGF antibodies and anti-FGF receptor antibodies represent new directions for the treatment of CNV. Similar to anti-vascular endothelial growth factor antibodies, subconjunctival injection and eye drops can be considered effective forms of drug delivery.