All-small-molecule supramolecular hydrogels assembled from guanosine 5'-monophosphate disodium salt and tobramycin for the treatment of bacterial keratitis

Mussel-Inspired In Situ Photodynamic Antibacterial Coating for Postoperative Management of Artificial Corneas

Artificial corneal (AC) implants offer hope to millions with corneal blindness, including 5 million in China. Titanium is one of the materials commonly used in the fabrication of artificial corneal scaffolders because of its light texture, high mechanical properties, and high biosafety. However, postoperative bacterial infections, especially from Pseudomonas aeruginosa and Staphylococcus aureus (S. aureus), remain a significant challenge due to the bioinert nature of titanium materials, leading to high infection rates. In this study, we introduce an innovative in situ photodynamic coating technology designed to manage postoperative infections in artificial corneas. Inspired by mussel adhesive proteins, this coating employs a composite of APTES-TA formed by Schiff base and Michael addition reactions between 3-aminopropyltriethoxysilane (APTES) and tannic acid (TA), integrated with the bacterial targeting capabilities of 4-carboxyphenylboronic acid (CPBA) and the photo-Fenton activity of FeOOH (iron(III) hydroxide). The design of the AC@APTES-TA-CPBA-FeOOH coating leverages the dynamic boronate ester bonds, which interact specifically with bacteria in tears, effectively capturing them on the surface of the artificial cornea. The coating exhibits a photocatalytic Fenton-like effect, which confers it with an exceptional bactericidal efficiency of over 99% in vitro. Furthermore, it demonstrates excellent protective functionality for mouse corneas in vivo experiments.

Nucleotide coordinated polymers, a ROS-based immunomodulatory antimicrobial, doubly kill Pseudomonas aeruginosa biofilms of implant infections

Pseudomonas aeruginosa causes high morbidity and mortality in nosocomial infections, and newly approved antibiotics have been declining for decades. A green and universal deprotonation-driven strategy is used to screen the guanylic acid-metal ion coordination polymer nanoparticles (GMC), instead of the failure of binding occurs when specific metal ion participation. We find that the precise pH-dependent oxidase-like activity of GMC-2 orchestrates a duple symphony of immune modulation for Pseudomonas aeruginosa biofilm infections. Specifically, GMC-2-mediated reactive oxygen species (ROS) regulation triggers mitochondrial dysfunction and releases damage-associated molecular patterns, engaging pattern recognition receptors and resulting in endogenous innate immune activation. Meanwhile, GMC-2-triggered ROS generation in a mildly acidic biofilm environment destroys the biofilm, exposing exogenous pathogen-associated molecular patterns. GMC-2 cannot cause resistance for Pseudomonas aeruginosa compared with conventional antibiotics. In an infected implant mouse model, Pseudomonas aeruginosa biofilms were effectively eliminated by GMC-2-mediated triggering of innate and adaptive immunity. These findings provide a universal approach for facilitating the binding of biomolecules with metal ions and highlight the precise ROS-regulating platform plays a critical role in initiating endogenous and exogenous immune activation targeted for bacterial biofilm infection.

Formulation and Release of Active Pharmaceutical Ingredients Using a Supramolecular Self-Healing Two-Component Gel

A two-component low-molecular-weight gelator (LMWG) formed from a modified amino acid and an aldehyde was formulated with active pharmaceutical ingredients (APIs). Basic APIs (propranolol, atropine) can be mixed with the LMWG prior to gel assembly while acidic APIs (naproxen, rosuvastatin) inhibit assembly by disrupting the LMWG imine bond and were loaded by diffusion after gel assembly. For diffusion-loaded gels, the API in the liquid-like phase was rapidly released, with the remainder, interacting with gel fibres, retained in the gel. Rosuvastatin release was particularly low with Saturation Transfer Difference (STD) NMR indicating interactions between the aromatic ring and the self-assembled gel network. Propranolol also interacted with the gel via its aromatic unit, and its release led to gel erosion. Using agarose as a polymer gelator additive reinforced the gel, restricting erosion. In contrast, atropine was readily released over a period of hours - it is primarily in the liquid-like phase with STD NMR indicating no interactions with the gel network. The atropine-loaded gel retained its thixotropic properties. Overall, APIs must be carefully chosen to optimise formulation/release. Of the APIs investigated, atropine has most potential for further development. Atropine has applications in treating myopia, and our results suggest potential ophthalmic applications of supramolecular gels.

High performances of cellulose nanocrystal based bicomponent supramolecular hydrogel lubricant

To improve the limitations of water-based lubricants, a novel cellulose nanocrystal based supramolecular hydrogel (CNC/x-DG/y) was prepared by mixing cellulose nanocrystal (CNC) and diglycerol (DG) into deionized water (DW). The hydrogel was characterized to determine its material ratio and gelation mechanism. When DW was fixed at 1 mL, CNC content should be no <2.4 wt% and DG content 0.1-1.3 mL. The gelification was driven by the multiple H-bond network between CNC and DG, which immobilized water molecules. The rheological performances, the anti-rust property and the volatilization behaviour of the hydrogel were further studied. The results showed that the hydrogel had satisfactory viscoelasticity, excellent thermal stability, strong creep recovery, high anti-rust performance and low volatilization rate, which were exactly its advantages for use as lubricant. A typical representative of the hydrogel, namely CNC/2.4-DG/0.1, was selected to evaluate the tribological performances, and the resulting worn surfaces were analyzed. CNC/2.4-DG/0.1 exhibited a lower friction coefficient of 0.059 and a smaller wear volume of 0.81 × 10-3 mm3, compared to DW(1 mL) + CNC(2.4 wt%) and DW(1 mL) + DG(0.1 mL). The outstanding tribological performances of CNC/2.4-DG/0.1 were reasonably attributed to the synergistic mending effect of CNC and DG and the dissipative effect of H-bonds between the two.

Oriented cellulose hydrogel: Directed tissue regeneration for reducing corneal leukoplakia and managing fungal corneal ulcers

Fungal corneal ulcer is one of the leading causes of corneal blindness in developing countries. Corneal scars such as leukoplakia are formed due to inflammation, oxidative stress and non-directed repair, which seriously affect the patients' subsequent visual and life quality. In this study, drawing inspiration from the oriented structure of collagen fibers within the corneal stroma, we first proposed the directional arrangement of CuTA-CMHT hydrogel system at micro and macro scales based on the 3D printing extrusion method combined with secondary patterning. It played an antifungal role and induced oriented repair in therapy of fungal corneal ulcer. The results showed that it effectively inhibited Candida albicans, Aspergillus Niger, Fusarium sapropelum, which mainly affects TNF, NF-kappa B, and HIF-1 signaling pathways, achieving effective antifungal functions. More importantly, the fibroblasts interacted with extracellular matrix (ECM) of corneal stroma through formation of focal adhesions, promoted the proliferation and directional migration of cells in vitro, induced the directional alignment of collagen fibers and corneal stromal orthogonally oriented repair in vivo. This process is mainly associated with MYLK, MYL9, and ITGA3 molecules. Furthermore, the downregulation the growth factors TGF-β and PDGF-β inhibits myofibroblast development and reduces scar-type ECM production, thereby reducing corneal leukoplakia. It also activates the PI3K-AKT signaling pathway, promoting corneal healing. In conclusion, the oriented CuTA-CMHT hydrogel system mimics the orthogonal arrangement of collagen fibers, inhibits inflammation, eliminates reactive oxygen species, and reduces corneal leukoplakia, which is of great significance in the treatment of fungal corneal ulcer and is expected to write a new chapter in corneal tissue engineering.

Critical Conditions Regulating the Gelation in Macroionic Cluster Solutions

The critical gelation conditions observed in dilute aqueous solutions of multiple nanoscale uranyl peroxide molecular clusters are reported, in the presence of multivalent cations. This gelation is dominantly driven by counterion-mediated attraction. The gelation areas in the corresponding phase diagrams all appear in similar locations, with a characteristic triangle shape outlining three critical boundary conditions, corresponding to the critical cluster concentration, cation/cluster ratio, and the degree of counterion association with increasing cluster concentration. These interesting phrasal observations reveal general conditions for gelation driven by electrostatic interactions in hydrophilic macroionic solutions.

Aflibercept Loaded Eye-Drop Hydrogel Mediated with Cell-Penetrating Peptide for Corneal Neovascularization Treatment

Corneal neovascularization (CoNV) is a major cause of visual impairment worldwide. Currently, available treatment options have limited efficacy and are associated with adverse effects due to biological barriers and clearance mechanisms. To address this challenge, a novel topical delivery system is developed-Gel 2_1&Eylea-an aflibercept-loaded eye-drop hydrogel mediated with cell-penetrating peptide 1. Gel 2_1&Eylea demonstrates superior membrane permeability, increased stability, and prolonged drug retention time on the ocular surface, and thus may improve drug efficacy. In a rabbit CoNV model, Gel 2_1&Eylea significantly reduces the density of neovascularization with no adverse effects on normal corneoscleral limbal vessels, demonstrating high efficacy and biocompatibility. This work identifies a promising treatment for CoNV which has the potential to benefit other ocular neovascular diseases.

Smart coating by thermo-sensitive Pluronic F-127 for enhanced corneal healing via delivery of biological macromolecule progranulin

As a leading cause of vision impairment and blindness, corneal alkali burns lead to long-term visual deterioration or even permanent visual impairment while effective treatment strategies remain a challenge. Herein, a thermo-sensitive hydrogel with the combination of multi-functional protein progranulin (PGRN), a biological macromolecule consisting of several hundred amino acids and possessing a high molecular weight, is efficiently prepared through a convenient stirring and mixing at the low temperature. The hydrogel can be easily administrated to the ocular surface contacting with the cornea, which can be immediately transformed into gel-like state due to the thermo-responsive behavior, realizing a site-specific coating to isolate further external stimulation. The smart coating not only exhibits excellent transparency and biocompatibility, but also presents a constant delivery of PGRN, creating a nutritious and supportive micro-environment for the ocular surface. The results show that the prepared functional hydrogel can efficiently suppress inflammation, accelerate re-epithelization, and intriguingly enhance axonal regeneration via modulation of multiple signaling pathways, indicating the novel designed HydrogelPGRN is a promising therapy option for serious corneal injury.

Bacteria-Targeting Nanosilver-Based Antibacterial Drugs for Efficient Treatment of Drug-Resistant Bacterial-Infected Keratitis

Keratitis caused by drug-resistant bacteria is a severe condition that can lead to corneal perforation and even blindness, making effective treatment a top priority amid growing antibiotic resistance. Eye drops for anti-inflammatory treatment necessitate frequent administration of high doses throughout every day due to bacterial resistance resulting from antibiotic overuse and the low bioavailability of drugs. To overcome these issues, an antibacterial nanocomposite is prepared via conjugating random copolymers of galactose and 3-(acrylamide)phenylboronic acid to the surface of silver nanoparticles. The customized nanocomposites trigger specific binding to bacteria, resulting in excellent retention of the drug on the ocular surface, resulting in rapid and powerful killing of bacteria and inhibition of bacterial proliferation. Due to its superior drug delivery capabilities to the ocular surface, the functionalized nanocomplex markedly amplifies the anti-inflammatory efficacy, even at low doses. This effect is achieved by impeding immune cell infiltration and diminishing the synthesis of inflammatory mediators and cytokines, thereby suggesting enhanced healing properties for corneal inflammation. This study demonstrates a promising nanocomposite which is an effective and safe antibacterial strategy for bacterial keratitis with favorable prognostic and clinical conversion potential.

Multifunctional Polymer Vesicles for Synergistic Antibiotic-Antioxidant Treatment of Bacterial Keratitis

As an acute ophthalmic infection, bacterial keratitis (BK) can lead to severe visual morbidity, such as corneal perforation, intraocular infection, and permanent corneal opacity, if rapid and effective treatments are not available. In addition to eradicating pathogenic bacteria, protecting corneal tissue from oxidative damage and promoting wound healing by relieving inflammation are equally critical for the efficient treatment of BK. Besides, it is very necessary to improve the bioavailability of drugs by enhancing the ocular surface adhesion and corneal permeability. In this investigation, therefore, a synergistic antibiotic-antioxidant treatment of BK was achieved based on multifunctional block copolymer vesicles, within which ciprofloxacin (CIP) was simultaneously encapsulated during the self-assembly. Due to the phenylboronic acid residues in the corona layer, these vesicles exhibited enhanced muco-adhesion, deep corneal epithelial penetration, and bacteria-targeting, which facilitated the drug delivery to corneal bacterial infection sites. Additionally, the abundant thioether moieties in the hydrophobic membrane enabled the vesicles to both have ROS-scavenging capacity and accelerated CIP release at the inflammatory corneal tissue. In vivo experiments on a mice model demonstrated that the multifunctional polymer vesicles achieved efficient treatment of BK, owing to the enhanced corneal adhesion and penetration, bacteria targeting, ROS-triggered CIP release, and the combined antioxidant-antibiotic therapy. This synergistic strategy holds great potential in the treatment of BK and other diseases associated with bacterial infections.

Nanomedicine for the Detection and Treatment of Ocular Bacterial Infections

Ocular bacterial infection is a prevalent cause of blindness worldwide, with substantial consequences for normal human life. Traditional treatments for ocular bacterial infections areless effective, necessitating the development of novel techniques to enable accurate diagnosis, precise drug delivery, and effective treatment alternatives. With the rapid advancement of nanoscience and biomedicine, increasing emphasis has been placed on multifunctional nanosystems to overcome the challenges posed by ocular bacterial infections. Given the advantages of nanotechnology in the biomedical industry, it can be utilized to diagnose ocular bacterial infections, administer medications, and treat them. In this review, the recent advancements in nanosystems for the detection and treatment of ocular bacterial infections are discussed; this includes the latest application scenarios of nanomaterials for ocular bacterial infections, in addition to the impact of their essential characteristics on bioavailability, tissue permeability, and inflammatory microenvironment. Through an in-depth investigation into the effect of sophisticated ocular barriers, antibacterial drug formulations, and ocular metabolism on drug delivery systems, this review highlights the challenges faced by ophthalmic medicine and encourages basic research and future clinical transformation based on ophthalmic antibacterial nanomedicine.

Smart G-quadruplex hydrogels: From preparations to comprehensive applications

In recent years, the accelerated development of G-quadruplexes and hydrogels has driven the development of intelligent biomaterials. Based on the excellent biocompatibility and special biological functions of G-quadruplexes, and the hydrophilicity, high-water retention, high water content, flexibility and excellent biodegradability of hydrogels, G-quadruplex hydrogels are widely used in various fields by combining the dual advantages of G-quadruplexes and hydrogels. Here, we provide a systematic and comprehensive classification of G-quadruplex hydrogels in terms of preparation strategies and applications. This paper reveals how G-quadruplex hydrogels skillfully utilize the special biological functions of G-quadruplexes and the skeleton structure of hydrogels, and expounds its applications in the fields of biomedicine, biocatalysis, biosensing and biomaterials. In addition, we deeply analyze the challenges in preparation, applications, stability and safety of G-quadruplex hydrogels, as well as potential future development directions.

Constructing ROS-Responsive Supramolecular Gel with Innate Antibacterial Properties

Bacterial infections, especially antibiotic-resistant bacterial infections, pose a significant threat to human health. Supramolecular gel with innate antibacterial properties is an advanced material for the treatment of bacterial infections, which have attracted great attention. Herein, a reactive oxygen species (ROS)-responsive innate antibacterial supramolecular gel is developed by a bottom-up approach based on phenylalanine and hydrazide with innate antibacterial properties. The structure of gelators and intermediate products was characterized by proton nuclear magnetic resonance (1H NMR) and a high-resolution mass spectrum (HRMS). The results of 1H NMR and the Fourier transform infrared spectrum (FT-IR) experiment disclosed that hydrogen bonding and the π-π stacking force are the important self-assembly driving forces of gelators. The microstructure and mechanical properties of gel were studied by Scanning electron microscope (SEM) and Rheometer, respectively. An in vitro degradation experiment proved that the gelator has ROS-responsive degradation properties. The in vitro drug release experiment further manifested that antibiotic-loaded gel has ROS-responsive drug-release performances. An in vitro cytotoxicity experiment showed that the supramolecular gel has good biocompatibility and could promote cell proliferation. The in vitro antibacterial experiment proved that the supramolecular gel has excellent inherent antibacterial properties, and the antibacterial rate against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was 98.6% and 99.1%, respectively. The ROS-responsive supramolecular gel as a novel antibacterial agent has great application prospects in treating antibiotic-resistant bacterial-infected wounds and preventing the development of bacterial resistance.

Chitosan-based hydrogel wound dressing: From mechanism to applications, a review

As promising biomaterials, hydrogels are widely used in the medical engineering field, especially in wound repairing. Compared with traditional wound dressings, such as gauze and bandage, hydrogel could absorb and retain more water without dissolving or losing its three-dimensional structure, thus avoiding secondary injury and promoting wound healing. Chitosan and its derivatives have become hot research topics for hydrogel wound dressing production due to their unique molecular structure and diverse biological activities. In this review, the mechanism of wound healing was introduced systematically. The mechanism of action of chitosan in the first three stages of wound repair (hemostasis, antimicrobial properties and progranulation), the effect of chitosan deacetylation and the molecular weight on its performance are analyzed. Additionally, the recent progress in intelligent and drug-loaded chitosan-based hydrogels and the features and advantages of chitosan were discussed. Finally, the challenges and prospects for the future development of chitosan-based hydrogels were discussed.

An injectable all-small-molecule dynamic metallogel for suppressing sepsis

All-small-molecule dynamic hydrogels have shown great promise in cell culture, tissue engineering, and controlled drug release. The further development of more kinds of all-small-molecule dynamic hydrogels is severely hindered by the lack of enough commensurate building blocks from nature and on the market. Inspired by the widely developed metal-organic framework structures, herein we report a facile fabrication of metallogels by direct gelation of small molecular compounds including aminoglycosides (AGs), 2,2'-bipyridine-4,4'-dicarboxaldehyde (BIPY), and metal ions via coordination interactions and Schiff base reactions. These prepared metallogels exhibited good biodegradability and biosafety, excellent conductivity, tunable mechanical properties and potent antibacterial activities both in vitro and in vivo. This study provides a new strategy for expanding the scope of all-small-molecule dynamic metallogels for various biomedical applications.

Recent progress of antibacterial hydrogels in wound dressings

Hydrogels are essential biomaterials due to their favorable biocompatibility, mechanical properties similar to human soft tissue extracellular matrix, and tissue repair properties. In skin wound repair, hydrogels with antibacterial functions are especially suitable for dressing applications, so novel antibacterial hydrogel wound dressings have attracted widespread attention, including the design of components, optimization of preparation methods, strategies to reduce bacterial resistance, etc. In this review, we discuss the fabrication of antibacterial hydrogel wound dressings and the challenges associated with the crosslinking methods and chemistry of the materials. We have investigated the advantages and limitations (antibacterial effects and antibacterial mechanisms) of different antibacterial components in the hydrogels to achieve good antibacterial properties, and the response of hydrogels to stimuli such as light, sound, and electricity to reduce bacterial resistance. Conclusively, we provide a systematic summary of antibacterial hydrogel wound dressings findings (crosslinking methods, antibacterial components, antibacterial methods) and an outlook on long-lasting antibacterial effects, a broader antibacterial spectrum, diversified hydrogel forms, and the future development prospects of the field.

Structural Strategies for Supramolecular Hydrogels and Their Applications

Supramolecular structures are of great interest due to their applicability in various scientific and industrial fields. The sensible definition of supramolecular molecules is being set by investigators who, because of the different sensitivities of their methods and observational timescales, may have different views on as to what constitutes these supramolecular structures. Furthermore, diverse polymers have been found to offer unique avenues for multifunctional systems with properties in industrial medicine applications. Aspects of this review provide different conceptual strategies to address the molecular design, properties, and potential applications of self-assembly materials and the use of metal coordination as a feasible and useful strategy for constructing complex supramolecular structures. This review also addresses systems that are based on hydrogel chemistry and the enormous opportunities to design specific structures for applications that demand enormous specificity. According to the current research status on supramolecular hydrogels, the central ideas in the present review are classic topics that, however, are and will be of great importance, especially the hydrogels that have substantial potential applications in drug delivery systems, ophthalmic products, adhesive hydrogels, and electrically conductive hydrogels. The potential interest shown in the technology involving supramolecular hydrogels is clear from what we can retrieve from the Web of Science.

Sprayable Antibacterial Hydrogels by Simply Mixing of Aminoglycoside Antibiotics and Cellulose Nanocrystals for the Treatment of Infected Wounds

Antibiotic hydrogels with sustained release profiles are recognized as promising candidates to treat local bacterial infections with reduced adverse effects. However, it still remains challenging for clinical translation of these antibiotic gels due to safety concern of gel ingredients, complicated synthesis and fabrication procedures, and unsatisfactory rheological properties for practical uses in vivo. Herein, the preparation of a type of sprayable hydrogels by ionic interactions between aminoglycosides and cellulose nanocrystals (CNC) is proposed for the treatment of local infections such as bacteria-infected wounds. The CNC-based hydrogels are applicable for all kinds of aminoglycoside antibiotics and show excellent gel stability and rheological behaviors such as shear thinning and fast self-healing, allowing facile administration by injection or spraying. The hydrogels exhibit efficient antibacterial activity both in vitro and in vivo, and accelerate bacteria-infected wounds by spraying on the infected area. The proposed hydrogels by simply mixing of aminoglycosides and CNC provide great prospects for clinical translation in the treatment of local infections.

Self-assembly hydrogels of therapeutic agents for local drug delivery

Advanced drug delivery systems are of vital importance to enhance therapeutic efficacy. Among various recently developed formulations, self-assembling hydrogels composed of therapeutic agents have shown promising potential for local drug delivery owing to their excellent biocompatibility, high drug-loading efficiency, low systemic toxicity, and sustained drug release behavior. In particular, therapeutic agents self-assembling hydrogels with well-defined nanostructures are beneficial for direct delivery to the target site via injection, not only improving drug availability, but also extending their retention time and promoting cellular uptake. In brief, the self-assembly approach offers better opportunities to improve the precision of pharmaceutical treatment and achieve superior treatment efficacies. In this review, we intend to cover the recent developments in therapeutic agent self-assembling hydrogels. First, the molecular structures, self-assembly mechanisms, and application of self-assembling hydrogels are systematically outlined. Then, we summarize the various self-assembly strategies, including the single therapeutic agent, metal-coordination, enzyme-instruction, and co-assembly of multiple therapeutic agents. Finally, the potential challenges and future perspectives are discussed. We hope that this review will provide useful insights into the design and preparation of therapeutic agent self-assembling hydrogels.

Bacterial Growth-Induced Tobramycin Smart Release Self-Healing Hydrogel for Pseudomonas aeruginosa-Infected Burn Wound Healing

Burns are a common health problem worldwide and are highly susceptible to bacterial infections that are difficult to handle with ordinary wound dressings. Therefore, burn wound repair is extremely challenging in clinical practice. Herein, a series of self-healing hydrogels (QCS/OD/TOB/PPY@PDA) with good electrical conductivity and antioxidant activity were prepared on the basis of quaternized chitosan (QCS), oxidized dextran (OD), tobramycin (TOB), and polydopamine-coated polypyrrole nanowires (PPY@PDA NWs). These Schiff base cross-links between the aminoglycoside antibiotic TOB and OD enable TOB to be slowly released and responsive to pH. Interestingly, the acidic substances during the bacteria growth process can induce the on-demand release of TOB, avoiding the abuse of antibiotics. The antibacterial results showed that the QCS/OD/TOB/PPY@PDA9 hydrogel could kill high concentrations of Pseudomonas aeruginosa (PA), Staphylococcus aureus, and Escherichia coli in a short time and showed a bactericidal effect for up to 11 days in an agar plate diffusion experiment, while showing good in vivo antibacterial activity. Excellent and long-lasting antibacterial properties make it suitable for severely infected wounds. Furthermore, the incorporation of PPY@PDA endowed the hydrogel with near-infrared (NIR) irradiation assisted bactericidal activity of drug-resistant bacteria, conductivity, and antioxidant activity. Most importantly, in the PA-infected burn wound model, the QCS/OD/TOB/PPY@PDA9 hydrogel more effectively controlled wound inflammation levels and promoted collagen deposition, vascular generation, and earlier wound closure compared to Tegaderm dressings. Therefore, the TOB smart release hydrogels with on-demand delivery are extremely advantageous for bacterial-infected burn wound healing.