Development of Poly(2-Methacryloyloxyethyl Phosphorylcholine)-Functionalized Hydrogels for Reducing Protein and Bacterial Adsorption

In Vitro Performance of a Long-Range Surface Plasmon Hydrogel Aptasensor for Continuous and Real-Time Vancomycin Measurement in Human Serum

This study investigated the suitability of surface modification for a long-range surface plasmon (LRSP) aptasensor using two different hydrogels, aiming at real-time monitoring of vancomycin (VCM) in undiluted serum and blood. Three different layer structures were formed on a gold surface of LRSP sensor chip using poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-N-methacryloyl-(L)-tyrosinemethylester (MAT)] (PMM) and poly[MPC-co-2-ethylhexyl methacrylate (EHMA)-co-MAT] (PMEM). The peptide aptamer for VCM was immobilized in PMM and PMEM via MAT. Among four differently prepared sensor chips, the LRSP hydrogel aptasensor with PMM, referred to as the PMM hydrogel, exhibited the highest sensor output and superior antifouling properties. Following the optimization of the PMM hydrogel preparation conditions, the shelf life of the PMM hydrogel was determined to exceed 2 weeks, and the same sensor chip could be used for 102 days without significant performance deterioration. The PMM hydrogel was then applied for VCM measurement in undiluted serum in vitro, where it demonstrated a limit of detection of 0.098 μM and a dynamic range of 0.18-100 μM, covering the therapeutic range. Additionally, the PMM hydrogel enabled the continuous measurement of various VCM concentrations in serum without rinsing and showed a concentration-dependent output in undiluted blood. These findings underscore the potential of the PMM hydrogel for real-time and direct monitoring of VCM in body fluids.

Photosensitizer-loaded hydrogels: A new antibacterial dressing

Bacterial wound infection has emerged as a pivotal threat to human health worldwide, and the situation has worsened owing to the gradual increase in antibiotic-resistant bacteria caused by the improper use of antibiotics. To reduce the use of antibiotics and avoid the increase in antibiotic-resistant bacteria, researchers are increasingly paying attention to  photodynamic therapy, which uses light to produce reactive oxygen species to kill bacteria. Treating bacteria-infected wounds by photodynamic therapy requires fixing the photosensitizer (PS) at the wound site and maintaining a certain level of wound humidity. Hydrogels are materials with a high water content and are well suited for fixing PSs at wound sites for antibacterial photodynamic therapy. Therefore, hydrogels are often loaded with PSs for treating bacteria-infected wounds via antibacterial photodynamic therapy. In this review, we systematically summarised the antibacterial mechanisms and applications of PS-loaded hydrogels for treating bacteria-infected wounds via photodynamic therapy. In addition, the recent  studies and the research status progresses of novel antibacterial hydrogels are discussed. Finally, the challenges and future prospects of PS-loaded hydrogels are reviewed.

Mussel-Inspired Antimicrobial and Antifouling Coating Constructed by the Combination of Zwitterionic Copolymers and Silver Nanoparticles

Biofouling and bacterial infections are significant challenges in biomedical devices. In this study, a biocompatible dual-functional coating with antimicrobial and antifouling properties is developed by co-depositing the zwitterionic copolymer and silver nanoparticles via a dopamine-assisted strategy. Inspired by mussel adhesion, the coating exhibits substrate-independent adhesion as a result of the formation of irreversible covalent bonds. The zwitterionic copolymer in the dual coating plays a crucial role in improving surface wettability and reducing protein adsorption and platelet and bacterial adhesion, thereby improving its antifouling property significantly. The silver nanoparticles reduced by self-polymerized polydopamine without the addition of any chemical reductants can effectively improve the antimicrobial activity. Furthermore, as the zwitterion content in the zwitterion polymer increases, the antibacterial and antifouling properties of the coating can be further advanced. The simple and effective approach presented here provides a promising pathway for constructing potent antibacterial and antifouling surfaces, demonstrating great potential for clinical applications in implanted materials.

Construction of a Soft Antifouling PAA/PSBMA Hydrogel Coating with High Toughness and Low Swelling through the Dynamic Coordination Bonding Provided by Al(OH)3 Nanoparticles

Marine biofouling, resulting from the adhesion of marine organisms to ship surfaces, has long been a significant issue in the maritime industry. In this paper, we focused on utilizing soft and hydrophilic hydrogels as a potential approach for antifouling (AF) coatings. Acrylic acid (AA) with a polyelectrolyte effect and N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine (SBMA) with an antipolyelectrolyte effect were selected as monomers. By adjusting the monomer ratio, we were able to create hydrogel coatings that exhibited low swelling ratio in both fresh water and seawater. The Al(OH)3 nanoparticle, as a physical cross-linker, provided better mechanical properties (higher tensile strength and larger elongation at break) than the chemical cross-linker through the dynamic coordination bonds and plentiful hydrogen bonds. Additionally, we incorporated trehalose into the hydrogel, enabling the repair of the hydrogel network through covalent-like hydrogen bonding. The zwitterion compound SBMA endowed the hydrogel with excellent AF performance. It was found that the highest SBMA content did not lead to the best antibacterial performance, as bacterial adhesion quantity was also influenced by the charge of the hydrogel. The hydrogel with appropriate SBMA content being close to electrical neutrality exhibits the strongest zwitterionic property of PSBMA chains, resulting in the best antibacterial adhesion performance. Furthermore, the pronounced hydrophilicity of SBMA enhanced the lubrication of the hydrogel surface, thereby reducing the friction resistance when applied to the hull surface during ship navigation.

Comparative Evaluation of Pseudomonas aeruginosa Adhesion to a Poly-(2-Methacryloyloxyethyl Phosphorylcholine)-Modified Silicone Hydrogel Contact Lens

Pseudomonas aeruginosa is the most common causative agent associated with microbial keratitis. During contact lens wear, pathogens may be introduced into the ocular environment, which might cause adverse events. Lehfilcon A is a recently developed contact lens with a water gradient surface composed of polymeric 2-methacryloyloxyethyl phosphorylcholine (MPC). MPC is re-ported to impart anti-biofouling properties onto modified substrates. Therefore, in this in vitro experimental study, we tested the capability of lehfilcon A to resist adhesion by P. aeruginosa. Quantitative bacterial adhesion assays using five strains of P. aeruginosa were conducted to compare the adherence properties of lehfilcon A to five currently marketed silicone hydrogel (SiHy) contact lenses (comfilcon A, fanfilcon A, senofilcon A, senofilcon C, and samfilcon A). Compared to lehfilcon A, we observed 26.7 ± 8.8 times (p = 0.0028) more P. aeruginosa binding to comfilcon A, 30.0 ± 10.8 times (p = 0.0038) more binding to fanfilcon A, 18.2 ± 6.2 times (p = 0.0034) more binding to senofilcon A, 13.6 ± 3.9 times (p = 0.0019) more binding to senofilcon C, and 29.5 ± 11.8 times (p = 0.0057) more binding to samfilcon A. These results demonstrate that, for various strains of P. aeruginosa, lehfilcon A reduces bacterial adhesion compared to other contact lens materials.

Research progress in decellularized extracellular matrix hydrogels for intervertebral disc degeneration

As one of the most common clinical disorders, low back pain (LBP) influences patient quality of life and causes substantial social and economic burdens. Many factors can result in LBP, the most common of which is intervertebral disc degeneration (IDD). The progression of IDD cannot be alleviated by conservative or surgical treatments, and gene therapy, growth factor therapy, and cell therapy have their own limitations. Recently, research on the use of hydrogel biomaterials for the treatment of IDD has garnered great interest, and satisfactory treatment results have been achieved. This article describes the classification of hydrogels, the methods of decellularized extracellular matrix (dECM) production and the various types of gel formation. The current research on dECM hydrogels for the treatment of IDD is described in detail in this article. First, an overview of the material sources, decellularization methods, and gel formation methods is given. The focus is on research performed over the last three years, which mainly consists of bovine and porcine NP tissues, while for decellularization methods, combinations of several approaches are primarily used. dECM hydrogels have significantly improved mechanical properties after the polymers are cross-linked. The main effects of these gels include induction of stem cell differentiation to intervertebral disc (IVD) cells, good mechanical properties to restore IVD height after polymer cross-linking, and slow release of exosomes. Finally, the challenges and problems still faced by dECM hydrogels for the treatment of IDD are summarised, and potential solutions are proposed. This paper is the first to summarise the research on dECM hydrogels for the treatment of IDD and aims to provide a theoretical reference for subsequent studies.

Cellulose Acetate Phthalate-Based pH-Responsive Cyclosporine A-Loaded Contact Lens for the Treatment of Dry Eye

Cyclosporine A (CsA) as an eye drop is an effective treatment for dry eye. However, it has potential side effects and a short ocular residence time. To overcome these obstacles, we developed a cellulose acetate phthalate-based pH-responsive contact lens (CL) loaded with CsA (CsA-CL). The CsA was continuously released from the CsA-CL at physiological conditions (37 °C, pH 7.4) without an initial burst. CsA was well-contained in the selected storage condition (4 °C, pH 5.4) for as long as 90 days. In safety assays, cytotoxicity, ocular irritation, visible light transmittance, and oxygen permeability were in a normal range. CsA concentrations in the conjunctiva, cornea, and lens increased over time until 12 h. When comparing the therapeutic efficacy between the normal control, experimental dry eye (EDE), and treatment groups (CsA eye drop, naïve CL, and CsA-CL groups), the tear volume, TBUT, corneal fluorescein staining at 7 and 14 days, conjunctival goblet cell density, and corneal apoptotic cell counts at 14 days improved in all treatment groups compared to EDE, with a significantly better result in the CsA-CL group compared with other groups (all p < 0.05). The CsA-CL could be an effective, stable, and safe option for inflammatory dry eye.

Phosphorylcholine-Based Contact Lenses for Sustained Release of Resveratrol: Design, Antioxidant and Antimicrobial Performances, and In Vivo Behavior

Design of advanced contact lenses (CLs) demands materials that are safe and comfortable for the wearers and that preserve the normal eye microbiota, avoiding chronic inflammation and biofilm development. This work aimed to combine the natural antibiofouling phosphorylcholine and the antioxidant and prebiotic resveratrol as integral components of CLs that may have the additional performance of preventing oxidative-stress related eye diseases. Different from previous uses of 2-methacryloyloxyethyl phosphorylcholine (MPC) as coating, we explored the feasibility of adding MPC at high proportions as a comonomer of 2-hydroxyethyl methacrylate (HEMA)-based hydrogels while still allowing for the loading of the hydrophobic resveratrol. Homogeneous distribution of MPC along the hydrogel depth (confirmed by Raman spectroscopy) notably increased solvent uptake and the proportion of free water while it decreased Young's modulus. Relevantly, MPC did not hinder the uptake of resveratrol by CLs (>10 mg/g), which indeed showed network/water partition coefficients of >100. Protocols for CLs sterilization and loading of resveratrol under aseptic conditions were implemented, and the effects of tear proteins on resveratrol release rate were investigated. CLs sustained resveratrol release for more than 24 h in vitro, and sorption of albumin onto the hydrogel, although attenuated by MPC, slowed down the release. The combination of MPC and resveratrol reduced P. aeruginosa and S. aureus growth as tested in a novel hydrogel disk-agar interface biofilm growth setup. The developed CLs showed excellent anti-inflammatory properties and biocompatibility in in ovo and rabbit tests and provided higher and more prolonged levels of resveratrol in tear fluid, which favored resveratrol biodistribution in anterior and posterior eye segments compared to eye drops. Correlations between the release profiles of resveratrol in vitro and in vivo were assessed. Relevantly, the CLs preserved the antioxidant properties of resveratrol during the entire 8 h of wearing. In sum, CLs prepared with high proportion in MPC may help address safety and comfort requirements while having drug releasing capabilities.

Recent Advances in Mechanical Reinforcement of Zwitterionic Hydrogels

As a nonspecific protein adsorption material, a strong hydration layer provides zwitterionic hydrogels with excellent application potential while weakening the interaction between zwitterionic units, leading to poor mechanical properties. The unique anti-polyelectrolyte effect in ionic solution further restricts the application value due to the worsening mechanical strength. To overcome the limitations of zwitterionic hydrogels that can only be used in scenarios that do not require mechanical properties, several methods for strengthening mechanical properties based on enhancing intermolecular interaction forces and polymer network structure design have been extensively studied. Here, we review the works on preparing tough zwitterionic hydrogel. Based on the spatial and molecular structure design, tough zwitterionic hydrogels have been considered as an important candidate for advanced biomedical and soft ionotronic devices.

Hydrophilic Micro- and Macroelectrodes with Antibiofouling Properties for Biomedical Applications

Implantable neural electrodes are generally used to record the electrical activity of neurons and to stimulate neurons in the nervous system. Biofouling triggered by inflammatory responses can dramatically affect the performance of neural electrodes, resulting in decreased signal sensitivity and consistency over time. Thus, long-term clinical applications require electrically conducting electrode materials with reduced dimensions, high flexibility, and antibiofouling properties that can reduce the degree of inflammatory reactions and increase the lifetime of neural electrodes. Carbon nanotubes (CNTs) are well known to form flexible assemblies such as CNT fibers. Herein, we report the covalent functionalization of predefined CNT fiber and film surfaces with hydrophilic, antibiofouling phosphorylcholine (PC) molecules. The electrochemical and spectroscopic characteristics, impedance properties, hydrophilicity, and in vitro antifouling nature of the functionalized CNT surfaces were evaluated. The hydrophilicity of the functionalized CNT films was demonstrated by a decrease in the static contact angle from 134.4° ± 3.9° before to 15.7° ± 1.5° after one and fully wetting after three functionalization cycles, respectively. In addition, the extent of protein absorption on the functionalized CNT films was significantly lower than that on the nonfunctionalized CNT film. Surprisingly, the faradic charge-transfer properties and impedance of the CNT assemblies were preserved after functionalization with PC molecules. These functionalized CNT assemblies are promising for the development of low-impedance neural electrodes with higher hydrophilicity and protein-fouling resistance to inhibit inflammatory responses.

Temperature-Responsive Aldehyde Hydrogels with Injectable, Self-Healing, and Tunable Mechanical Properties

Injectable and self-healing hydrogels with exemplary biocompatibility and tunable mechanical properties are urgently needed due to their significant advantages for tissue engineering applications. Here, we report a new temperature-responsive aldehyde hydrogel with dual physical-cross-linked networks and injectable and self-healing properties prepared from an ABA-type triblock copolymer, poly{[FPMA(4-formylphenyl methacrylate)-co-DEGMA[di(ethylene glycol) methyl ether methacrylate]-b-MPC(2-methacryloyloxyethyl phosphorylcholine)-b-(FPMA-co-DEGMA)}. The thermoresponsive poly(DEGMA) segments drive the dehydration and hydrophobic interaction, enabling polymer chain winding as the first cross-linking network, when the temperature is raised above the critical gelation temperature. Meanwhile, the benzaldehyde groups offer physical interactions, including hydrogen bonding and hydrophobic and π-π stacking interactions as the second cross-linking network. When increasing the benzaldehyde content in the triblock copolymers from 0 to 8.2 mol %, the critical gelation temperature of the resulted hydrogels dropped from 35.5 to 19.9 °C and the mechanical modulus increased from 21 to 1411 Pa. Owing to the physical-cross-linked networks, the hydrogel demonstrated excellent injectability and self-healing properties. The cell viabilities tested from MTT assays toward both normal lung fibroblast cells (MRC-5) and cancerous cervical (HeLa) cells were found to be 100 and 101%, respectively, for varying polymer concentrations up to 1 mg/mL. The 3D cell encapsulation of the hydrogels was evaluated by a cytotoxicity Live/Dead assay, showing 92% cell viability. With these attractive physiochemical and biological properties, this temperature-responsive aldehyde hydrogel can be a promising candidate as a cell scaffold for tissue engineering.

Recent Advances in Zwitterionic Hydrogels: Preparation, Property, and Biomedical Application

Nonspecific protein adsorption impedes the sustainability of materials in biologically related applications. Such adsorption activates the immune system by quick identification of allogeneic materials and triggers a rejection, resulting in the rapid failure of implant materials and drugs. Antifouling materials have been rapidly developed in the past 20 years, from natural polysaccharides (such as dextran) to synthetic polymers (such as polyethylene glycol, PEG). However, recent studies have shown that traditional antifouling materials, including PEG, still fail to overcome the challenges of a complex human environment. Zwitterionic materials are a class of materials that contain both cationic and anionic groups, with their overall charge being neutral. Compared with PEG materials, zwitterionic materials have much stronger hydration, which is considered the most important factor for antifouling. Among zwitterionic materials, zwitterionic hydrogels have excellent structural stability and controllable regulation capabilities for various biomedical scenarios. Here, we first describe the mechanism and structure of zwitterionic materials. Following the preparation and property of zwitterionic hydrogels, recent advances in zwitterionic hydrogels in various biomedical applications are reviewed.

Resveratrol-Loaded Hydrogel Contact Lenses with Antioxidant and Antibiofilm Performance

Contact lenses (CLs) are prone to biofilm formation, which may cause severe ocular infections. Since the use of antibiotics is associated with resistance concerns, here, two alternative strategies were evaluated to endow CLs with antibiofilm features: copolymerization with the antifouling monomer 2-methacryloyloxyethyl phosphorylcholine (MPC) and loading of the antioxidant resveratrol with known antibacterial activity. MPC has, so far, been used to increase water retention on the CL surface (Proclear^® 1 day CLs). Both poly(hydroxyethyl methacrylate) (HEMA) and silicone hydrogels were prepared with MPC covering a wide range of concentrations (from 0 to 101 mM). All hydrogels showed physical properties adequate for CLs and successfully passed the hen’s egg-chorioallantoic membrane (HET-CAM) test. Silicone hydrogels had stronger affinity for resveratrol, with higher loading and a slower release rate. Ex vivo cornea and sclera permeability tests revealed that resveratrol released from the hydrogels readily accumulated in both tissues but did not cross through. The antibiofilm tests against Pseudomonas aeruginosa and Staphylococcus aureus evidenced that, in general, resveratrol decreased biofilm formation, which correlated with its concentration-dependent antibacterial capability. Preferential adsorption of lysozyme, compared to albumin, might also contribute to the antimicrobial activity. In addition, importantly, the loading of resveratrol in the hydrogels preserved the antioxidant activity, even against photodegradation. Overall, the designed hydrogels can host therapeutically relevant amounts of resveratrol to be sustainedly released on the eye, providing antibiofilm and antioxidant performance.

Synthesis and antifouling performance of tadpole-shaped poly(N-hydroxyethylacrylamide) coatings

Linear poly(N-hydroxyethylacrylamide) (PHEAA) is regarded as one of the most promising antifouling materials because of its excellent antifouling properties and good hemocompatibility. However, the antifouling performance of topological PHEAAs remains largely unknown. Herein, the preparation of antifouling surfaces based on a tadpole-shaped PHEAA coating is reported for the first time, and how the tadpole-shaped PHEAA architecture affects antifouling performance is investigated. It is shown that the tadpole-shaped PHEAA-modified surfaces exhibit better antifouling performance than linear copolymer precursor-modified surfaces with identical molar masses and chemical compositions. This may be primarily attributed to the presence of cyclic PHEAA head chain segments in the tadpole-shaped PHEAA copolymer, and the absence of interchain entanglements can facilitate the formation of smoother and densely packed grafts, which result in better antifouling properties.

Dual-Cross-Linked Network Hydrogels with Multiresponsive, Self-Healing, and Shear Strengthening Properties

Dual-cross-linked network (DCN) hydrogels with multiresponsive and self-healing properties are attracting intensive interests due to their enhanced mechanical strength for a wide range of applications. Herein, we developed a DCN hydrogel that combines a dynamic imine and a benzoxaboronic ester with a neutral pK_a value (∼7.2) as dual linkages and contains biocompatible zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] as the backbone. Oscillatory rheology result indicated shear strengthening mechanical properties compared to the single-cross-linked network (SCN) hydrogels, which use either imine bond or benzoxaboronic ester as the linkage alone. Due to the coexistence of stimuli-responsive imine and benzoxaboronic ester, the DCN hydrogels show sensitive multiple responsiveness to pH, sugar, and hydrogen peroxide. The dynamic nature of the dual linkages endows the DCN hydrogels with excellent self-healing ability after fracture. More importantly, the excellent biocompatibility and performance in three-dimensional (3D) cell encapsulation were established by a cytotoxicity Live/Dead assay, indicating DCN hydrogel's great potential as a cell culture scaffold. The biocompatible poly(MPC)-based backbone and the rapid formation of the cross-linking network make the DCN hydrogels promising candidates for future biomedical applications.

Oncogenic Epidermal Growth Factor Receptor Silencing in Cervical Carcinoma Mediated by Dynamic Sugar-Benzoxaborole Polyplexes

Although, various types of pharmaceuticals have been developed for cervical carcinomas, treatment with these drugs often results in a number of undesirable side effects, toxicity and multidrug resistance. Here, we aimed at modifying the genetic profiling of cancer cells by silencing the expression of the epidermal growth factor receptor (EGFR) gene. We have synthesized two kinds of RAFT-made, biocompatible, and cationic polymers for the encapsulation of silencing RNA (siRNA). This vector has a dual capability: it contains a cationic segment to complex with the siRNA and an omega-end modified with an oxaborole group via thiol-ene click chemistry that responds to the acidic tumor microenvironment. This structural innovation enables this macromolecule to interact with multiple polyplexes and release the siRNA in a mild acidic environment. A strategy that has shown enhanced gene silencing without elevating the cytotoxicity of the system, as determined by Western blot analysis. The success of this approach has afforded further interest in utilizing boron-carbohydrate interaction in the development of nonviral vectors for gene therapy.