Hydrogel Coatings Research Articles

State-of-the-Art Insights and Potential Applications of Cellulose-Based Hydrogels in Food Packaging: Advances towards Sustainable Trends

Leveraging sustainable packaging resources in the circular economy framework has gained significant attention in recent years as a means of minimizing waste and mitigating the negative environmental impact of packaging materials. In line with this progression, bio-based hydrogels are being explored for their potential application in a variety of fields including food packaging. Hydrogels are three-dimensional, hydrophilic networks composed of a variety of polymeric materials linked by chemical (covalent bonds) or physical (non-covalent interactions) cross-linking. The unique hydrophilic nature of hydrogels provides a promising solution for food packaging systems, specifically in regulating moisture levels and serving as carriers for bioactive substances, which can greatly affect the shelf life of food products. In essence, the synthesis of cellulose-based hydrogels (CBHs) from cellulose and its derivatives has resulted in hydrogels with several appealing features such as flexibility, water absorption, swelling capacity, biocompatibility, biodegradability, stimuli sensitivity, and cost-effectiveness. Therefore, this review provides an overview of the most recent trends and applications of CBHs in the food packaging sector including CBH sources, processing methods, and crosslinking methods for developing hydrogels through physical, chemical, and polymerization. Finally, the recent advancements in CBHs, which are being utilized as hydrogel films, coatings, and indicators for food packaging applications, are discussed in detail. These developments have great potential in creating sustainable packaging systems.

Progress in Surface Modification of Titanium Implants by Hydrogel Coatings.

Although titanium and titanium alloys have become the preferred materials for various medical implants, surface modification technology still needs to be strengthened in order to adapt to the complex physiological environment of the human body. Compared with physical or chemical modification methods, biochemical modification, such as the introduction of functional hydrogel coating on implants, can fix biomolecules such as proteins, peptides, growth factors, polysaccharides, or nucleotides on the surface of the implants, so that they can directly participate in biological processes; regulate cell adhesion, proliferation, migration, and differentiation; and improve the biological activity on the surface of the implants. This review begins with a look at common substrate materials for hydrogel coatings on implant surfaces, including natural polymers such as collagen, gelatin, chitosan, and alginate, and synthetic materials such as polyvinyl alcohol, polyacrylamide, polyethylene glycol, and polyacrylic acid. Then, the common construction methods of hydrogel coating (electrochemical method, sol-gel method and layer-by-layer self-assembly method) are introduced. Finally, five aspects of the enhancement effect of hydrogel coating on the surface bioactivity of titanium and titanium alloy implants are described: osseointegration, angiogenesis, macrophage polarization, antibacterial effects, and drug delivery. In this paper, we also summarize the latest research progress and point out the future research direction. After searching, no previous relevant literature reporting this information was found.

Fabrication of antibacterial Fe3+-carboxymethylcellulose-polyacrylamide-Ag nanoparticles hydrogel coating for urinary catheters

Catheter-associated urinary tract infections (CAUTIs) are one of the most common hospital-acquired infections. In this study, a new Fe3+-carboxymethylcellulose (CMC)-polyacrylamide (PAAm) - Ag nanoparticles (AgNPs) interpenetrating hydrogel coating with antibacterial properties on the surfaces of latex urinary catheters was prepared with a simple dipping method. The morphology, chemical composition, surface roughness, and contact angles of the coated urinary catheters were characterized by using SEM, EDS, ATR-FTIR, XPS, AFM, and contact angle instruments, respectively. The antibacterial performance of the coated urinary catheters was characterized by the inhibition zone tests. Furthermore, the toxicity profile of the coated urinary catheters was also evaluated in vitro via MTT assay and hemolysis test. The experimental results showed that the Fe3+-CMC-PAAm-AgNPs hydrogel-coated urinary catheters had strong antibacterial effects. The concentration of AgNPs after the release of 30 days was still higher than the effective antibacterial concentration of the total Ag (0.1 ppb) and was lower than the toxic concentration of human cells (10 ppm). The inhibition zone tests of the coated urinary catheter against E. coli (ATCC25922) showed that both the CMC-PAAm-AgNPs hydrogel coatings and the Fe3+-CMC-PAAm-AgNPs hydrogel coatings had clear inhibition zones in the culture medium. The addition of Fe3+ exhibited synergistic antibacterial effects with AgNPs. Moreover, the coatings also showed admirable biocompatibility and hemocompatibility. The synergistic antibacterial mechanism was also proposed. The novel Fe3+-CMC-PAAm-AgNPs hydrogel coatings for urinary catheters would have great potential in reducing CAUTIs.

Antibacterial-Based Hydrogel Coatings and Their Application in the Biomedical Field—A Review

Hydrogels exhibit excellent moldability, biodegradability, biocompatibility, and extracellular matrix-like properties, which make them widely used in biomedical fields. Because of their unique three-dimensional crosslinked hydrophilic networks, hydrogels can encapsulate various materials, such as small molecules, polymers, and particles; this has become a hot research topic in the antibacterial field. The surface modification of biomaterials by using antibacterial hydrogels as coatings contributes to the biomaterial activity and offers wide prospects for development. A variety of surface chemical strategies have been developed to bind hydrogels to the substrate surface stably. We first introduce the preparation method for antibacterial coatings in this review, which includes surface-initiated graft crosslinking polymerization, anchoring the hydrogel coating to the substrate surface, and the LbL self-assembly technique to coat crosslinked hydrogels. Then, we summarize the applications of hydrogel coating in the biomedical antibacterial field. Hydrogel itself has certain antibacterial properties, but the antibacterial effect is not sufficient. In recent research, in order to optimize its antibacterial performance, the following three antibacterial strategies are mainly adopted: bacterial repellent and inhibition, contact surface killing of bacteria, and release of antibacterial agents. We systematically introduce the antibacterial mechanism of each strategy. The review aims to provide reference for the further development and application of hydrogel coatings.

Abstract 3297: Deep reactive ion etched microneedle array for in-vivo melanoma cancer monitoring via cancer exosome isolation

Abstract This study reports a deep-reactive-ion-etched microneedle device (ExoNeedle chip) coated with a hybrid hydrogel that can directly capture cancer-associated extracellular vesicles (EVs) in interstitial fluid (ISF) in a minimally invasive manner, as opposed to conventional liquid biopsy methods involving sample extraction and EV isolation in-vitro or tissue biopsies for melanoma. Tumor derived EVs give insight into a tumor’s mutational burden and provide both prognostic and diagnostic value as a liquid biopsy tool. Melanoma is an aggressive cancer with a lack of promising markers for early detection, onset of metastasis, and monitoring of recurrence. The ExoNeedle chip is intended to pierce through the epidermis and parts of the dermis to isolate melanoma secreted EVs from the ISF to alleviate these unmet needs. The microneedle arrays were created through the Deep Reactive Ion Etching (DRIE) process and a subsequent wet etching step to sharpen the needles. A 4 inch silicon wafer spin coated with 3 microns of positive photoresist was lithographically patterned and etched by DRIE using the standard Bosch processes to expose arrays of cylindrical pillars. Next, the cylindrical features were sharpened using an isotropic wet etch consisting of a mixture of hydrofluoric and nitric acid. The microneedle arrays were made and cleaved into individual patches. Meanwhile, hybrid hydrogel solution was made from Polyvinyl alcohol (PVA) and alginate by dissolving each of them separately in water under heat, followed by mixing the solutions. After centrifuging and filtering the hydrogel, it was conjugated with Annexin V (Av) protein to give it affinity for cancerous exosomes. Lastly, this hydrogel complex was added onto the microneedle patches and gelated with the help of a humidifier that deposited Ca2+ ion vapor over the hydrogel. The microneedles were first optimized and validated using melanoma cell line secreted EVs. Melanoma EVs were successfully isolated and quantified to evaluate the efficacy of the microneedle patches yielding above an 80% capture efficiency from purified serum samples. The microneedle patches were DiO stained, fluorescently imaged, visualized in a scanning electron microscope, and protein concentration was determined respectfully. Additionally, the functional hydrogel coatings on the microneedles are dissolved in ethylenediaminetetraacetic acid (EDTA), subsequently unbinding EVs from Av due to EDTA-based Ca2+ chelation. The dissolved solution is then used for enumeration and quantification of EVs by nanoparticle tracking analysis. We are further validating these patches in skin mimicking models and patient derived xenograft models of melanoma. The technology developed in this study for the isolation of melanoma EVs can broadly pave the way for minimally invasive point of care cancer diagnostics and tracking for melanoma patients. Citation Format: Scott M. Smith, Abha Kumari, Thiago Reis, Yoon-Tae Kang, Sunitha Nagrath. Deep reactive ion etched microneedle array for in-vivo melanoma cancer monitoring via cancer exosome isolation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3297.

Dynamic Cross-Linking Network Construction of Carboxymethyl Starch Enabling Temperature and Strain Bimodal Film Sensors

Building stimulus-responsive units in the hydrogel coatings remains challenging for film sensors consisting of alternated layers of inert substrates and hydrogel coatings. An interesting film sensor with a carboxymethyl starch-based hydrogel coating was developed here. The cross-linking networks of carboxymethyl starch play the roles of structure-constructing units and stimulus-controlling units simultaneously, endowing the coatings with thermal sensing and strain sensing capabilities. The dynamic cross-links formed via the boronic ester bonds are temperature-sensitive, releasing or consuming additional acid ions with temperature alteration, and also as primary networks give the hydrogel strength and stretchability with the assistance of semi-penetrated polyacrylamide chains. Therefore, as-prepared flexible film sensors can be used to detect the periodic changes of human temperature and small-scale motion with multiple working modes, discriminating the physical states related to human health. Moreover, this kind of starch-based coating is degradable in a strongly alkaline solution and the inert substrate layer can protect the skin from erosion caused by direct hydrogel-skin contact, and thereby the film sensor is human- and environmentally friendly. This work also proposes a strategy of building temperature-sensitive units in the film sensor via regulating the chemical networks, instead of tuning physical structures.

Study on the Interaction of Plasma-Polymerized Hydrogel Coatings with Aqueous Solutions of Different pH.

Amphiphilic hydrogels from mixtures of 2-hydroxyethyl methacrylate and 2-(diethylamino)ethyl methacrylate p(HEMA-co-DEAEMA) with specific pH sensitivity and hydrophilic/hydrophobic structures were designed and polymerized via plasma polymerization. The behavior of plasma-polymerized (pp) hydrogels containing different ratios of pH-sensitive DEAEMA segments was investigated concerning possible applications in bioanalytics. In this regard, the morphological changes, permeability, and stability of the hydrogels immersed in solutions of different pHs were studied. The physico-chemical properties of the pp hydrogel coatings were analyzed using X-ray photoelectron spectroscopy, surface free energy measurements, and atomic force microscopy. Wettability measurements showed an increased hydrophilicity of the pp hydrogels when stored in acidic buffers and a slightly hydrophobic behavior after immersion in alkaline solutions, indicating a pH-dependent behavior. Furthermore, the pp (p(HEMA-co-DEAEMA) (ppHD) hydrogels were deposited on gold electrodes and studied electrochemically to investigate the pH sensitivity of the hydrogels. The hydrogel coatings with a higher ratio of DEAEMA segments showed excellent pH responsiveness at the studied pHs (pH 4, 7, and 10), demonstrating the importance of the DEAEMA ratio in the functionality of pp hydrogel films. Due to their stability and pH-responsive properties, pp (p(HEMA-co-DEAEMA) hydrogels are conceivable candidates for functional and immobilization layers for biosensors.

Mechanical and tribological characterisations of PEG-based hydrogel coatings on XLPE surfaces

Hydrophilic hydrogel coatings can impart enhanced tribological and antifouling properties to biomedical device surfaces. The influence of crosslinking on the elastic moduli of poly (ethylene glycol) (PEG) hydrogels is well established, however, the effect of crosslinking on the ability of the hydrogels to form coatings on crosslinked polyethylene (XLPE) substrates is not fully understood, nor are the mechanics and tribological performance of the resultant hydrogel coated substrates. PEG hydrogels of four different crosslinking levels (5, 7.5, 10 and 12.5% crosslinker concentrations) were deposited onto XLPE substrates. Crosslinked matched hydrogel plugs were also manufactured for mechanical analysis. The wear performance and friction evolution of coated pins were assessed against sterilised cobalt chromium discs at a contact pressure of 0.08 MPa under an elliptical orbital motion. The indentation results showed an increase in the elastic modulus with increasing crosslinker concentration, which was augmented further by gamma sterilisation treatment. Hydrogel coated pins exhibited reduced friction levels compared to uncoated pins, and confocal imaging in conjuction with the roughness monitoring indicated that the coatings protected the asperities from being removed. The friction values increased as the tests progressed, in line with the coverage of the hydrogel coating decreasing and forming a hybrid XLPE/gel vs CoCr contact. The 10% cross-linker hydrogel coating produced the lowest friction and wear of all the coatings tested.

Fabrication of a New Hyaluronic Acid/Gelatin Nanocomposite Hydrogel Coating on Titanium-Based Implants for Treating Biofilm Infection and Excessive Inflammatory Response

Persistent inflammation caused by implant-associated biofilm infections has emerged as a significant clinical issue. While many methods have been developed to give implants great anti-biofilm benefits, the post-inflammatory microenvironment is frequently disregarded. Oxidative stress (OS) due to excessive reactive oxygen species (ROS) is considered to be one of the specific physiological signals of the inflammation microenvironment. Herein, ZIF-90-Bi-CeO2 nanoparticles (NPs) were incorporated into a Schiff-base chemically crosslinked hydrogel composed of aldehyde-based hyaluronic acid and gelatin. Through chemical crosslinking between polydopamine and gelatin, the hydrogel coating adhered to the Ti substrate. The modified Ti substrate gained multimodal antibacterial and anti-biofilm functions, which were attributed to the photothermal effect of Bi NPs, and the release of Zn ions and CeO2 NPs. Notably, CeO2 NPs endowed the system with dual-enzyme (SOD- and CAT-like) catalytic activities. In a rat implant-associated infection (IAI) model, the dual-functional hydrogel had a biofilm-removal ability and regulated OS and inflammatory responses to facilitate osseointegration. The photothermal therapy combined with a host inflammation-microenvironment regulation strategy might provide a novel treatment for biofilm infection and the accompanying excessive inflammation.

Polyacrylamide-based hydrogel coatings improve biocompatibility of implanted pump devices.

The introduction of transcutaneous and subcutaneous implants and devices into the human body instigates fouling and foreign body responses (FBRs) that limit their functional lifetimes. Polymer coatings are a promising solution to improve the biocompatibility of such implants, with potential to enhance in vivo device performance and prolong device lifetime. Here we sought to develop novel materials for use as coatings on subcutaneously implanted devices to reduce the FBR and local tissue inflammation in comparison to gold standard materials such as poly(ethylene glycol) and polyzwitterions. We prepared a library of polyacrylamide-based copolymer hydrogels, which were selected from materials previously shown to exhibit remarkable antifouling properties with blood and plasma, and implanted them into the subcutaneous space of mice to evaluate their biocompatibility over the course of 1 month. The top performing polyacrylamide-based copolymer hydrogel material, comprising a 50:50 mixture of N-(2-hydroxyethyl)acrylamide (HEAm) and N-(3-methoxypropyl)acrylamide (MPAm), exhibited significantly better biocompatibility and lower tissue inflammation than gold standard materials. Moreover, when applied to polydimethylsiloxane disks or silicon catheters as a thin coating (45 ± 1μm), this leading copolymer hydrogel coating significantly improved implant biocompatibility. Using a rat model of insulin-deficient diabetes, we showed that insulin pumps fitted with HEAm-co-MPAm hydrogel-coated insulin infusion catheters exhibited improved biocompatibility and extended functional lifetime over pumps fitted with industry standard catheters. These polyacrylamide-based copolymer hydrogel coatings have the potential to improve device function and lifetime, thereby reducing the burden of disease management for people regularly using implanted devices.

Biodegradable and Cytocompatible Hydrogel Coating with Antibacterial Activity for the Prevention of Implant-Associated Infection.

Implant-associated infection (IAI) caused by pathogens colonizing on the implant surface is a serious issue in the trauma-orthopedic surgery, which often leads to implant failure. The complications of IAI bring a big threat to the clinical practice of implants, accompanied by significant economic cost and long hospitalization time. In this study, we propose an antibiotics-free strategy to address IAI-related challenges by using a biodegradable and cytocompatible hydrogel coating. To achieve this, a novel hydrogel system was developed to combine the synergistic effects of good cell affinity and antibacterial properties. The hydrogel material was prepared by modifying a photocross-linkable gelatin-based polymer (GelMA) with cationic quaternary ammonium salt (QAS) groups via a mild and simple synthesis procedure. By engineering the length of the hydrophobic carbon chain on the QAS group and the degree of functionalization, the resulting GelMA-octylQAS hydrogel exhibited an integration of good mechanical properties, biodegradability, excellent bactericidal activity against various types of bacteria, and high cytocompatibility with mammalian cells. When coated onto the implant via the in situ cross-linking procedure, our hydrogel demonstrated superior antimicrobial ability in the infective model of femoral fracture of rats. Our results suggest that the GelMA-octylQAS hydrogel might provide a promising platform for preventing and treating IAI.

Synthesis and characterization of positive volume phase transition hydrogel membrane prepared using a cellulose substrate

ABSTRACT Thermo-responsive hydrogels display swell-collapse behavior in response to changing temperature. While the hydrogels themselves have many applications such as environmental and chemical separations, the hydrogel can be incorporated within a membrane substrate to improve its mechanical properties and expand the opportunities for development and implementation. The present work describes synthesis of positive volume transition temperature responsive poly(acrylamide-co-acrylic acid) hydrogels on cellulose paper substrates. Effects of factors including co-monomer ratios, degree of crosslinking and mass loading are assessed for Series A random copolymer hydrogels in terms of permeability response. Examination of the membranes is then extended to investigate inter-penetrating networks (IPN) between acrylamide and acrylic acid homo-polymer hydrogels. Series B membranes explore the impact of nonpolar ligands on temperature response through addition of butyl methacrylate co-monomer. For both random copolymer and IPN hydrogel membranes, mass loading dominates permeability performance, though certain criteria must be met. Performance of the Series A membranes was found to be ideal when monomer ratio was 1:1 and there was a lower degree of crosslinking. Addition of butyl methacrylate did not appear to have a consistent impact on the membrane response, appearing to be tied to the degree of crosslinking for random copolymer hydrogel coatings.

PEG-Based Hydrogel Coatings: Design Tools for Biomedical Applications.

Device failure due to undesired biological responses remains a substantial roadblock in the development and translation of new devices into clinical care. Polyethylene glycol (PEG)-based hydrogel coatings can be used to confer antifouling properties to medical devices-enabling minimization of biological responses such as bacterial infection, thrombosis, and foreign body reactions. Application of hydrogel coatings to diverse substrates requires careful consideration of multiple material factors. Herein, we report a systematic investigation of two coating methods: (1) traditional photoinitiated hydrogel coatings; (2) diffusion-mediated, redox-initiated hydrogel coatings. The effects of method, substrate, and compositional variables on the resulting hydrogel coating thickness are presented. To expand the redox-based method to include high molecular weight macromers, a mechanistic investigation of the role of cure rate and macromer viscosity was necessary to balance solution infiltration and gelation. Overall, these structure-property relationships provide users with a toolbox for hydrogel coating design for a broad range of medical devices.

Hydrogel/β-FeOOH-Coated Poly(vinylidene fluoride) Membranes with Superhydrophilicity/Underwater Superoleophobicity Facilely Fabricated via an Aqueous Approach for Multifunctional Applications.

Hydrogel coatings that can endow various substrates with superior properties (e.g., biocompatibility, hydrophilicity, and lubricity) have wide applications in the fields of oil/water separation, antifouling, anti-bioadhesion, etc. Currently, the engineering of multifunctional hydrogel-coated materials with superwettability and water purification property using a simple and sustainable strategy is still largely uninvestigated but has a beneficial effect on the world. Herein, we successfully prepared poly(2-acrylamido-2-methyl-1-propanesulfonic acid) hydrogel/β-FeOOH-coated poly(vinylidene fluoride) (PVDF/PAMPS/β-FeOOH) membrane through free-radical polymerization and the in situ mineralization process. In this work, owing to the combination of hydrophilic PAMPS hydrogel coating and β-FeOOH nanorods anchored onto PVDF membrane, the resultant PVDF/PAMPS/β-FeOOH membrane achieved outstanding superhydrophilicity/underwater superoleophobicity. Moreover, the membrane not only effectively separated surfactant-stabilized oil/water emulsions, but also possessed a long-term use capacity. In addition, excellent photocatalytic activity against organic pollutants was demonstrated so that the PVDF/PAMPS/β-FeOOH membrane could be utilized to deal with wastewater. It is envisioned that these hydrogel/β-FeOOH-coated PVDF membranes have versatile applications in the fields of oil/water separation and wastewater purification.

Improved Antifouling Ability for Double‐Network Hydrogel Coatings with Excellent Elastic and Toughness under Marine Tidal Environment

The marine coating in the tidal zone is crucial to restoring its protective function in the case of coating defects, mainly due to the structural damage of the coating by the alternation of wet and dry in the tidal zone and the surface damage of the coating by the impact of sand and gravel. Hydrophilic materials such as hydrogel transformed the tidal zone into an entire immersion zone. Due to the complexation of copper, the fouling problem can be effectively reduced. The coating (AAm/Alginate‐Ca/Cu‐BTA) has excellent mechanical properties (modulus: 200 kPa, toughness 128 J m−2) and significant adhesion (138 J m−2). Otherwise, herein, simultaneously mechanical tests of hydrogels at different temperatures and excellent mechanical properties (modulus: 160 kPa, toughness 100 J m−2) after 7 days of use in alternating dry and wet environments every 6 h are shown. It's proved that the coating has an excellent antifouling and anticorrosion effect. Meanwhile, theoretical study reveals the nature of the weak mechanical properties of hydrogel materials at low temperatures. This work provides an effective strategy for preparing hydrogel coatings with excellent mechanical properties and marine anticorrosion and antifouling. It also proves that hydrogels have broad application prospects in marine tidal zone by excellent water retention performance.

Recent advances in hydrogel coatings for urinary catheters

AbstractCatheters are commonly used in hospital treatment, but most of the medical materials used in the production of catheters are hydrophobic, with high surface friction and weak antibacterial properties, so a large amount of money is spent on the treatment of catheter‐related urinary tract infections worldwide every year. To improve the comfort of patients, weaken the friction and damage between urinary catheters and urethra, and reduce economic burden, coating the urethral catheter surface is a good strategy. Because of the softness, lubricity and functional network structure (load or graft different substances) of hydrogel, it has a wide range of applications for medical devices. In recent years, the studies of hydrogel coatings in urethral catheters have received more and more attention. This review mainly summarized the research progress of hydrogel coating in recent years, including its function and the method of guiding the grafting of hydrogel to the substrate, and the prospects in the future.

Antimicrobial-Loaded Polyacrylamide Hydrogels Supported on Titanium as Reservoir for Local Drug Delivery.

Arthroplasty is a highly successful treatment to restore the function of a joint. The contamination of the implant via bacterial adhesion is the first step toward the development of device-associated infections. The emerging concern about antimicrobial resistance resulted in a growing interest to develop alternative therapeutic strategies. Thus, the increment in the incidence of bacterial periprosthetic infections, the complexity of treating infections caused by organisms growing in biofilms, together with the rise in antibiotic resistant bacteria, expose the need to design novel surfaces that provide innovative solutions to these rising problems. The aim of this work is to develop a coating on titanium (Ti) suitable for inhibiting bacterial adhesion and proliferation, and hence, biofilm formation on the surface. We have successfully prepared polyacrylamide hydrogels containing the conventional antibiotic ampicillin (AMP), silver nanoparticles (AgNPs), and both, AMP and AgNPs. The release of the antibacterial agents from the gelled to aqueous media resulted in an excellent antibacterial action of the loaded hydrogels against sessile S. aureus. Moreover, a synergic effect was achieved with the incorporation of both AMP and AgNPs in the hydrogel, which highlights the importance of combining antimicrobial agents having different targets. The polyacrylamide hydrogel coating on the Ti surface was successfully achieved, as it was demonstrated by FTIR, contact angle, and AFM measurements. The modified Ti surfaces having the polyacrylamide hydrogel film containing AgNPs and AMP retained the highest antibacterial effect against S. aureus as it was found for the unsupported hydrogels. The modified surfaces exhibit an excellent cytocompatibility, since healthy, flattened MC3T3-E1 cells spread on the surfaces were observed. In addition, similar macrophage RAW 264.7 adhesion was found on all the surfaces, which could be related to a low macrophage activation. Our results indicate that AMP and AgNP-loaded polyacrylamide hydrogel films on Ti are a good alternative for designing efficient antibacterial surfaces having an excellent cytocompatibility without inducing an exacerbated immune response. The approach emerges as a superior alternative to the widely used direct adsorption of therapeutic agents on surfaces, since the antimicrobial-loaded hydrogel coatings open the possibility of modulating the concentration of the antimicrobial agents to enhance bacterial killing, and then, reducing the risk of infections in implantable materials.

Self-healable and Conductive Hydrogel Coatings Based on Host-guest Complexation between β-Cyclodextrin and Adamantane

Simultaneously self-healable and conductive materials are desirable because of their lightness, long lifetime, and flexibility. Although supramolecular chemistry has been employed to prepare these desired materials, in many cases, additional conductive agents are required. Herein, we incorporated the host-guest complexation between cyclodextrin and adamantane into an intrinsically conductive polymer system. The obtained polymeric materials showed simultaneous self-healing properties and electrical conductivities solely as coatings without addition of any conductive agents.

Multifunctional antibacterial chitosan-based hydrogel coatings on Ti6Al4V biomaterial for biomedical implant applications

Among biomedical community, great efforts have been realized to develop antibacterial coatings that avoid implant-associated infections. To date, conventional mono-functional antibacterial strategies have not been effective enough for successful long-term implantations. Consequently, researchers have recently focused their attention on novel bifunctional or multifunctional antibacterial coatings, in which two or more antibacterial mechanisms interact synergistically. Thus, in this work different chitosan-based (CHI) hydrogel coatings were created on Ti6Al4V surface using genipin (Ti-CHIGP) and polyethylene glycol (Ti-CHIPEG) crosslinking agents. Hydrogel coatings demonstrated an exceptional in vivo biocompatibility plus a remarkable ability to promote cell proliferation and differentiation. Lastly, hydrogel coatings demonstrated an outstanding bacteria-repelling (17–28 % of S. aureus and 33–43 % of E. coli repelled) and contact killing (186–222 % of S. aureus and 72–83 % of E. coli damaged) ability. Such bifunctional antibacterial activity could be further improved by the controlled release of drugs resulting in powerful multifunctional antibacterial coatings.

Understanding the (dis)-assembly of in situ forming hydrogel coatings in a 2D model system

HypothesisInjectable hydrogels are important in situ forming implants for tissue regeneration at damaged sites. Understanding the behavior of these systems in a complex in vivo environment remains a challenge. Ultrathin films as 2D model systems are expected to provide fundamental insights into formation and (bio)degradation at material-liquid interfaces, and are also applicable as bioresponsive coatings. ExperimentsHydrogel ultrathin films are prepared by covalently cross-linking four-arm PEG macromers with maleimide end-groups (PEG4MAL) at alkaline pH using two different types of dithiol-bearing cross-linkers – thio-depsipeptide (TDP) or 3,6-Dioxa-1,8-octanedithiol (DODT). This thiol-Michael addition “click” reaction is carried out at the air-water interface using the Langmuir technique. Morphological observation in real time is carried out by Brewster angle microscopy (BAM) and in coatings using atomic force microscopy (AFM). Stability against enzymatic and oxidative degradation is evaluated in the same setup. FindingsNon-cross-linked PEG or PEG incubated with cross-linkers at slightly acidic pH desorbs from the interface over time. Cross-linking of PEG at alkaline pH renders 2D hydrogel networks (thickness <1 nm) that are stable against desorption. They are easily transferrable onto solid mica surfaces, forming homogenous coatings as revealed by AFM. The type of dithiol cross-linker used to form the branching centers influences the degradability of these 2D hydrogel networks in the presence of lipase, peroxides, or bases. For example, enzymatic degradation of the 2D hydrogel networks can be switched “on” or “off” depending on the cleavable sites in the cross-linkers.