Antifouling and antibacterial zwitterionic hydrogels as soft contact lens against ocular bacterial infections

Polycarboxybetaine in advanced drug delivery systems: From structure-function relationship to therapeutic applications

Zwitterionic polycarboxybetaines (PCBs), combining quaternary ammonium cations and carboxylate anions in their repeating units, have emerged as promising materials for drug delivery applications. Their exceptional hydration, biocompatibility, and antifouling properties make them attractive alternatives to polyethylene glycol (PEG), particularly given growing concerns about immunogenicity of PEG. PCBs can be functionalized through various methods, including modification of side-chain moieties, adjustment of spacer length between charged groups, and incorporation of responsive elements. When applied to delivery drug, PCBs have been successfully developed into multiple formats including micelles, hydrogels, liposomes, and nanoparticles. Notably, in protein drug delivery, PCBs demonstrate significant advantages such as enhancing protein stability, extending circulation time, improving penetration through biological barriers, and reducing immunogenicity. Despite these promising features, several challenges remain, including complex synthesis requirements, limited mechanical properties, and pending FDA approval as pharmaceutical excipients. This review provides a comprehensive analysis of PCBs from the structure-function relationship, synthesis methods, and applications in drug delivery systems, while examining current limitations and future prospects.

Dual-functional hCe-pHEMA contact lenses for ocular antibiotic release, antioxidant protection, and in vivo corneal bacterial infection treatment

Ocular bacterial infections are typically associated with elevated levels of reactive oxygen species (ROS). Nevertheless, for treating ocular bacterial keratitis (BK), broad-spectrum antibiotics in eye drops or ointments are unable to inhibit ROS and encounter swift clearance and reduced bioavailability. This work developed antibiotic levofloxacin (LEV)-loaded hollow ceria nanoparticles (hCe NPs, ROS scavengers), which were embedded into poly-hydroxyethyl methacrylate (pHEMA) hydrogels to prepare dual-functional contact lenses (LEV@hCe-pHEMA), enabling extended ocular drug delivery and enhanced bioavailability. The integration of LEV@hCe NPs within pHEMA contact lenses preserved good optical transmittance (> 90.0 %), fortified UV-blocking capacities (200-400 nm), achieved controllable LEV release (84.2 % within 120 h), and enhanced ROS scavenging-antioxidative potential (78.4 % within 60 min). In vitro cytotoxicity evaluations revealed low cytotoxicity (cell viability >95.0 %) of the hCe-pHEMA contact lenses and affirmed their good biocompatibility. Notably, LEV@hCe-pHEMA exhibited significant antibacterial efficacy against S. aureus ATCC29213 (89.8 %) and E. coli ATCC25922 (94.2 %), demonstrating their therapeutic potential. In vivo safety evaluations in rabbit models showed no ocular irritation or pathological changes during a 7-day wearing period, confirming the good biocompatibility of the hCe-pHEMA lenses. LEV@hCe-pHEMA contact lenses could be utilized to treat rabbit BK model induced by S. aureus. It could near-completely remove the keratitis (within 7 days), reducing corneal edema and further recovering corneal transparency. The results suggested that LEV@hCe-pHEMA contact lenses could be employed as promising dual-functional smart ocular drug delivery systems for non-invasive ocular therapy.

Zwitterionic Hydrogels: From Synthetic Design to Biomedical Applications

Zwitterionic hydrogels have emerged as a highly promising class of biomaterials, attracting considerable attention due to their unique properties and diverse biomedical applications. Zwitterionic moieties, with their balanced positive and negative charges, endow hydrogels with exceptional hydration, resistance to nonspecific protein adsorption, and low immunogenicity due to their distinctive molecular structure. These properties facilitate various biomedical applications, such as medical device coatings, tissue engineering, drug delivery, and biosensing. This review explores the structure-property relationships in zwitterionic hydrogels, highlighting recent advances in their design principles, synthesis methods, structural characteristics, and biomedical applications. To meet the evolving and growing demand for the biomedical field, this review examines current challenges and explores future research directions for optimizing the multifunctional properties of zwitterionic hydrogels. As promising candidates for advanced biomaterials, zwitterionic hydrogels are poised to address critical challenges in biomedical applications, paving the way for improved therapeutic outcomes and broader applicability in healthcare.

Preparation of Zwitterionic Sulfobetaines and Study of Their Thermal Properties and Nanostructured Self-Assembling Features

Zwitterionic polymers have garnered significant attention for their distinctive properties, such as biocompatibility, antifouling capabilities, and resistance to protein adsorption, making them promising candidates for a wide range of applications, including drug delivery, oil production inhibitors, and water purification membranes. This study reports the synthesis and characterization of zwitterionic monomers and polymers through the modification of linear, vinyl, and aromatic heterocyclic functional groups via reaction with 1,3-propanesultone. Four zwitterionic polymers with varying molecular structures-ranging from linear to five and six membered ring systems-were synthesized: poly(sulfobetaine methacrylamide) (pSBMAm), poly(sulfobetaine-1-vinylimidazole) (pSB1VI), poly(sulfobetaine-2-vinylpyridine) (pSB2VP), and poly(sulfobetaine-4-vinylpyridine) (pSB4VP). Their molecular weights, thermal behavior, and self-assembly properties were analyzed using gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and zeta potential measurements. The glass transition temperatures (Tg) ranged from 276.52 °C for pSBMAm to 313.69 °C for pSB4VP, while decomposition temperatures exhibited a similar trend, with pSBMAm degrading at 301.03 °C and pSB4VP at 387.14 °C. The polymers' self-assembly behavior was strongly dependent on pH and their surface charge, particularly under varying pH conditions: spherical micelles were observed at neutral pH, while fractal aggregates formed at basic pH. These results demonstrate that precise modifications of the chemical structure, specifically in the linear, imidazole, and pyridine moieties, enable fine control over the thermal properties and self-assembly behavior of polyzwitterions. Such insights are essential for tailoring polymer properties for targeted applications in filtration membranes, drug delivery systems, and solid polymer electrolytes, where thermal stability and self-assembly play crucial roles.

A "Janus" Zwitterionic Hydrogel Patch for Tissue Repair and Prevention of Post-Operative Adhesions

Anti-peritoneal adhesions (PA) are very important after abdominal surgery for that PA often leads to other medical problems and imposes a huge financial burden on the national healthcare system. In this work, a "Janus" zwitterionic hydrogel patch where one side can adhere firmly to the tissue, while the other side has anti-fouling properties and has little interaction with the surrounding tissue has been developed. The "Janus" hydrogel patch is prepared by in situ formation of a bonding polymer layer poly(acrylic-co-N-hydroxysuccinimide acrylate) on one side of zwitterionic hydrogel. The mechanical, swelling, adhesion, biodegradability and biocompatibility tests are performed to study the function of "Janus" hydrogel patch to prevent wound adhesion and rapid repair. It is found that the adhesive side of the hydrogel patch has stable adhesion to tissues, avoiding the slippage faced by many commercial anti-adhesion gels in the body. The other zwitterionic side can resist proteins and fibroblasts and prevent external interactions or adhesion with other tissues. This convenient and effective method provides a new idea for the design of postoperative anti-adhesion materials and broadens the application of hydrogels in the biomedical field.

Ag/Cu nanoparticles-loaded glycocalyx biomimetic corneal bandage lenses for combatting bacterial keratitis

Bacterial keratitis is a major cause of blindness, hindered by the rising threat of antibiotic resistance. Although corneal bandage lenses (CBLs) are widely utilized in ophthalmic treatment, their effectiveness in treating bacterial keratitis remains limited due to risks of secondary infections, patient discomfort, and complications. In this study, we developed a novel biomimetic coating on CBLs by grafting Ag/Cu bimetallic nanoparticles (Ag/Cu-NPs) and thiol-functionalized heparin (Hep-SH) using a rapid polydopamine (PDA) deposition technique, effectively mimicking the ocular surface glycocalyx structure. The resulting Ag/Cu-NPs/Hep-SH coated CBLs (PNH-CBLs) exhibited significant antibacterial activity, with over 80 % reduction in Staphylococcus aureus (S. aureus) and 70 % in Escherichia coli (E. coli) due to the sustained release of Ag+ and Cu2+, along with displaying favorable in vitro biocompatibility. Animal experiments conducted on New Zealand white rabbits with bacterial keratitis demonstrated successful treatment therapeutic outcomes, with PNH-CBLs leading to a significant decrease in clinical score. These biomimetic lenses also exhibited selective anti-protein adsorption properties, minimizing inflammation and promoting surface lubrication. Overall, this innovative approach addresses critical challenges in antibiotic resistance and offers a promising therapeutic strategy for managing ophthalmic infectious diseases.

Mitigation of pesticide-mediated ocular toxicity via nanotechnology-based contact lenses: a review

The xenobiotic stress exerted by pesticides leads to the deterioration of human and animal health including ocular health. Acute or prolonged exposure to these agricultural toxicants has been implicated in a number of pathological conditions of the eye such as irritation, epiphora or hyper-lacrimation, abrasions on the ocular surface, and decreased visual acuity. The issue is compounded by the fact that tissues of the eye absorb pesticides faster than other organs of the body and are more susceptible to damage as well. However, there is a lacuna in our knowledge regarding the ways by which pesticide exposure-mediated ocular insult might be counteracted. Topical instillation of drugs known to combat the pesticide induced toxicity has been explored to mitigate the detrimental impact of pesticide exposure. However, topical eye drop solutions exhibit very low bioavailability and limited drug residence duration in the tear film decreasing their efficacy. Contact lenses have been explored in this respect to increase bioavailability of ocular drugs, while nanoparticles have lately been utilized to increase drug bioavailability and increase drug residence duration in different tissues. The current review focuses on drug delivery and futuristic aspects of corneal protection from ocular toxicity using contact lenses.

Recent advances of multifunctional zwitterionic polymers for biomedical application

Zwitterionic polymers possess equal total positive and negative charges in the repeating units, making them electrically neutral overall. This unique property results in superhydrophilicity, which makes the zwitterionic polymers highly effective in resisting protein adsorption, thus endowing the drug carriers with long blood circulation time, inhibiting thrombus formation on biomedical devices in contact with blood, and ensuring the good sensitivity of sensors in biomedical application. Moreover, zwitterionic polymers have tumor-targeting ability and pH-responsiveness, rendering them ideal candidates for antitumor drug delivery. Additionally, the high ionic conductivity of zwitterionic polymers makes them an important raw material for ionic skin. Zwitterionic polymers exhibit remarkable resistance to bacterial adsorption and growth, proving their suitability in a wide range of biomedical applications such as ophthalmic applications, and wound dressings. In this paper, we provide an in-depth analysis of the different structures and characteristics of zwitterionic polymers and highlight their unique qualities and suitability for biomedical applications. Furthermore, we discuss the limitations and challenges that must be overcome to realize the full potential of zwitterionic polymers and present an optimistic perspective for zwitterionic polymers in the biomedical fields. STATEMENT OF SIGNIFICANCE: Zwitterionic polymers have a series of excellent properties such as super hydrophilicity, anti-protein adsorption, antibacterial ability and good ionic conductivity. However, biomedical applications of multifunctional zwitterionic polymers are still a major field to be explored. This review focuses on the design and application of zwitterionic polymers-based nanosystems for targeted and responsive delivery of antitumor drugs and cancer diagnostic agents. Moreover, the use of zwitterionic polymers in various biomedical applications such as biomedical devices in contact with blood, biosensors, ionic skin, ophthalmic applications and wound dressings is comprehensively described. We discuss current results and future challenges for a better understanding of multifunctional zwitterionic polymers for biomedical applications.

Antimicrobial Hydrogels: Potential Materials for Medical Application

Microbial infections based on drug-resistant pathogenic organisms following surgery or trauma and uncontrolled bleeding are the main causes of increased mortality from trauma worldwide. The prevalence of drug-resistant pathogens has led to a significant increase in medical costs and poses a great threat to the normal life of people. This is an important issue in the field of biomedicine, and the emergence of new antimicrobial materials hydrogels holds great promise for solving this problem. Hydrogel is an important material with good biocompatibility, water absorption, oxygen permeability, adhesion, degradation, self-healing, corrosion resistance, and controlled release of drugs as well as structural diversity. Bacteria-disturbing hydrogels have important applications in the direction of surgical treatment, wound dressing, medical device coating, and tissue engineering. This paper reviews the classification of antimicrobial hydrogels, the current status of research, and the potential of antimicrobial hydrogels for one application in biomedicine, and analyzes the current research of hydrogels in biomedical applications from five aspects: metal-loaded hydrogels, drug-loaded hydrogels, carbon-material-loaded hydrogels, hydrogels with fixed antimicrobial activity and biological antimicrobial hydrogels, and provides an outlook on the high antimicrobial activity, biodegradability, biocompatibility, injectability, clinical applicability and future development prospects of hydrogels in this field.

Design, fabrication, evaluation, and in vitro study of green biomaterial and antibacterial polymeric biofilms of polyvinyl alcohol/tannic acid/CuO/ SiO2

In this study, a three-component biofilm for rapid wound dressing consisting of polyvinyl alcohol (PVA)/tannic acid (TA)/with CuO/SiO2 with different percentages (0, 5, 10, and 15 wt% NPs) is evaluated. In addition to controlling bleeding and absorption of blood and wound secretions, it protects the damaged tissue from the attack of microbes. It protects against viruses and thus reduces the treatment time. Analysis of biofilms morphology is performed by Field emission scanning electron microscopy (FE-SEM), phases in biofilms were analyzed by X-ray diffraction (XRD) analysis, chemical bonds, and functional groups are analyzed by Fourier transform infrared (FTIR) spectroscopy, and mechanical tests are performed to evaluate the strength of the samples. The thermogravimetric analysis (TGA) is applied to estimate the thermal stability of the biopolymer films with various percentages of CuO/SiO2 nanoparticles. Also, antibacterial test, bioactivity of the biofilms, the percentage of swelling ratio, and porosity of the samples were examined by immersing the samples in simulated body fluid (SBF) and Phosphate-buffered saline (PBS) for 14 days in vitro. The composite makeup of the TA/PVA sample, comprising 15 wt % CuO/SiO2 and containing 15 wt% of nanoparticles, exhibited superior heat resistance compared to other samples by an increase of 50 °C. This improvement can be attributed to the nanoparticles reaching their saturation point. The swelling ratio was assessed in both SBF and PBS, and in both instances, the sample increased by up to 10 wt% before decreasing, indicating the saturation of the nanoparticles.

Synthesis of novel interpenetrated network for ocular co-administration of timolol maleate and dorzolamide hydrochloride drugs

In the present work, novel interpenetrated networks (IPNs) of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide) (SBMA) and poly(vinyl alcohol) (PVA) were prepared for the ocular co-administration of timolol maleate (TIM) and dorzolamide hydrochloride (DORZ), two drugs widely used for the treatment of glaucoma. The successful polymerization of SBMA, in the presence of PVA, led to the formation of semi-interpenetrated pSBMA-PVA networks (IPNs), in the form of sponges, exhibiting intrinsic antimicrobial properties attributed to SBMA. Fourier-transform infrared spectroscopy (FTIR) was utilized to confirm the successful synthesis of the IPNs. Further assessments, including contact angle and water sorption measurements, highlighted their significant hydrophilicity, a feature that makes them suitable for ocular applications. Differential scanning calorimetry (DSC) measurements indicated that PVA serves as a plasticizer, while an assessment of the water sorption capacity of these materials suggested that although the incorporation of PVA results in slightly less hydrophilic materials, the prepared sponges still remain sufficiently hydrophilic for ocular use. Following their characterization, the optimal pSBMA-PVA IPN was used to encapsulate TIM and DORZ. Irritation tests, performed using the HET-CAM method, confirmed that the drug-loaded sponges were safe and potentially well-tolerated for ophthalmic use. Finally, the co-release study for the two drugs revealed a sustained release pattern in both cases, while drug release from the sponges was primarily controlled by diffusion.

Drug Delivery for Ocular Allergy: Current Formulation Design Strategies and Future Perspectives

The incidences of ocular allergy have been growing with the increase in pollution. Because of challenges in new drug development, there have been efforts to maximize the efficacy of existing drugs through drug delivery approaches. The effectiveness of drugs in ophthalmic conditions is primarily determined by permeability across the barrier, corneal retention, and sustained release. Thus, there have been widespread efforts to optimize these parameters to enhance efficacy through novel formulations. This review aims to analyze the approaches to drug delivery systems to encourage further research to optimize effectiveness. With this objective, research on drug delivery aspects of anti-allergy therapeutics was included and analyzed based on formulation/drug delivery technique, Food and Drug Administration approval limits, residence time, compatibility, pre-clinical efficacy, and potential for translational application. Conventional eye drops have concerns such as poor residence time and ocular bioavailability. The novel formulations have the potential to improve residence and bioavailability. However, the use of preservatives and the lack of regulatory approval for polymers limit the translational application. The review may assist readers in identifying novel drug delivery strategies and their limitations for the development of effective ophthalmic formulations for the treatment of ocular allergy.

Zwitterionic poly(sulfobetaine methacrylate)-based hydrogel coating for drinking water distribution systems to inhibit adhesion of waterborne bacteria

Presence of biofilms in drinking water distribution systems (DWDS) can be a nuisance, leading to several operational and maintenance issues (i.e., increased secondary disinfectants demand, pipe damage or increased flow resistance), and so far, no single control practice was found to be sufficiently effective. Here, we propose poly (sulfobetaine methacrylate) (P(SBMA))-based hydrogel coating application as a biofilm control strategy in DWDS. The P(SBMA) coating was synthetized through photoinitiated free radical polymerization on polydimethylsiloxane with different combinations of SBMA as a monomer, and N, N'-methylenebis (acrylamide) (BIS) as a cross-linker. The most stable coating in terms of its mechanical properties was obtained using 20% SBMA with a 20:1 SBMA:BIS ratio. The coating was characterized using Scanning Electron Microscopy, Energy Dispersive X-Ray Spectroscopy, and water contact angle measurements. The anti-adhesive performance of the coating was evaluated in a parallel-plate flow chamber system against adhesion of four bacterial strains representing genera commonly identified in DWDS biofilm communities, Sphingomonas and Pseudomonas. The selected strains exhibited varying adhesion behaviors in terms of attachment density and bacteria distribution on the surface. Despite these differences, after 4 h, presence of the P(SBMA)-based hydrogel coating significantly reduced the number of adhering bacteria by 97%, 94%, 98% and 99%, for Sphingomonas Sph5, Sphingomonas Sph10, Pseudomonas extremorientalis and Pseudomonas aeruginosa, respectively, compared to non-coated surfaces. These findings motivate further research into a potential application of a hydrogel anti-adhesive coating as a localized biofilm control strategy in DWDS, especially on materials known to promote excessive biofilm growth.

Zwitterionic Biomaterials

The term "zwitterionic polymers" refers to polymers that bear a pair of oppositely charged groups in their repeating units. When these oppositely charged groups are equally distributed at the molecular level, the molecules exhibit an overall neutral charge with a strong hydration effect via ionic solvation. The strong hydration effect constitutes the foundation of a series of exceptional properties of zwitterionic materials, including resistance to protein adsorption, lubrication at interfaces, promotion of protein stabilities, antifreezing in solutions, etc. As a result, zwitterionic materials have drawn great attention in biomedical and engineering applications in recent years. In this review, we give a comprehensive and panoramic overview of zwitterionic materials, covering the fundamentals of hydration and nonfouling behaviors, different types of zwitterionic surfaces and polymers, and their biomedical applications.

Interpenetrating polymeric network (IPNs) in ophthalmic drug delivery: Breaking the barriers

To maintain the therapeutic drug concentration for a prolonged period of time in aqueous and vitreous humor is primary challenge for ophthalmic drug delivery. Majority of the locally administered drug into the eye is lost as to natural reflexes like blinking and lacrimation resulting in the short span of drug residence. Consequently, less than 5% of the applied drug penetrate through the cornea and reaches the intraocular tissues. The major targets for optimal ophthalmic drug delivery are increasing drug residence time in cul-de-sac of the eye, prolonging intraocular exposure, modulating drug release from the delivery system, and minimizing pre-corneal drug loss. Development of in situ gel, contact lens, intraocular lens, inserts, artificial cornea, scaffold, etc., for ophthalmic drug delivery are few approaches to achieve these major targeted objectives for delivering the drug optimally. Interpenetrating polymeric network (IPN) or smart hydrogels or stimuli sensitive hydrogels are the class of polymers that can help to achieve the targets in ophthalmic drug delivery due to their versatility, biocompatibility and biodegradability. These novel ''smart" materials can alter their molecular configuration and result in volume phase transition in response to environmental stimuli, such as temperature, pH, ionic strength, electric and magnetic field. Hydrogel and tissue interaction, mechanical/tensile properties, pore size and surface chemistry of IPNs can also be modulated for tuning the drug release kinetics. Stimuli sensitive IPNs has been widely exploited to prepare in situ gelling formulations for ophthalmic drug delivery. Low refractive index hydrogel biomaterials with high water content, soft tissue-like physical properties, wettability, oxygen, glucose permeability and desired biocompatibility makes IPNs versatile candidate for contact lenses and corneal implants. This review article focuses on the exploration of these smart polymeric networks/IPNs for therapeutically improved ophthalmic drug delivery that has unfastened novel arenas in ophthalmic drug delivery.