Facile Fabrication of Multifunctional Hydrogel Nanoweb Coating Using Carboxymethyl Chitosan-Based Short Nanofibers for Blood-Contacting Medical Devices

Blood-contacting medical devices (BCDs) require antithrombotic, antibacterial, and low-friction surfaces. Incorporating a nanostructured surface with the functional hydrogel onto BCD surfaces can enhance the performances; however, their fabrication remains challenging. Here, we introduce a straightforward method to fabricate a multifunctional hydrogel-based nanostructure on BCD surfaces using O-carboxymethyl chitosan-based short nanofibers (CMC-SNFs). CMC-SNFs, fabricated via electrospinning and cutting processes, are easily sprayed and entangled onto the BCD surface. The deposited CMC-SNFs form a robust nanoweb layer via fusion at the contact area of the nanofiber interfaces. The superhydrophilic CMC-SNF nanoweb surface creates a water-bound layer that effectively prevents the nonspecific adhesion of bacteria and blood cells, thereby enhancing both antimicrobial and antithrombotic performances. Furthermore, the CMC-SNF nanoweb exhibits excellent lubricity and durability on the bovine aorta. The demonstration results of the CMC-SNF coating on catheters and sheaths provide evidence of its capability to apply multifunctional surfaces simply for diverse BCDs.

Electrified Interactions of Polyzwitterions with Charged Surfaces: Role of Dipole Orientation and Surface Potentials

The zwitterionic groups possess strong dipole moments, leading to inter- or intrachain interactions among zwitterionic polymers. This study aims to demonstrate the interaction of polyzwitterions poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), and poly(carboxybetaine methacrylate) (PCBMA) with electrified surfaces, despite their electrically neutral nature. We studied the adsorption of polyzwitterions and their monomers on electrified surfaces by using an electrochemical quartz crystal microbalance with dissipation (EQCM-D). The interaction between zwitterionic molecules and charged surfaces is explored by adjusting the surface potentials. Interestingly, the adsorption of polyzwitterions can be influenced by external potential, primarily due to the formation of polyzwitterions restricting the mobility of zwitterionic groups, affecting the adsorption behavior of polyzwitterions based on the surface potential. The impact is determined by the arrangement of positive and negative ions within the zwitterionic groups, which are the dipole orientation. Additionally, surface potentials determine the adsorption rate, amount, and chain conformation of the adsorbed thin polyzwitterion layers. The effect of ionic strength was investigated by introducing electrolytes into the aqueous solutions to assess the range of influenced surface potentials.

Unravelling Surface Modification Strategies for Preventing Medical Device-Induced Thrombosis

The use of biomaterials in implanted medical devices remains hampered by platelet adhesion and blood coagulation. Thrombus formation is a prevalent cause of failure of these blood-contacting devices. Although systemic anticoagulant can be used to support materials and devices with poor blood compatibility, its negative effects such as an increased chance of bleeding, make materials with superior hemocompatibility extremely attractive, especially for long-term applications. This review examines blood-surface interactions, the pathogenesis of clotting on blood-contacting medical devices, popular surface modification techniques, mechanisms of action of anticoagulant coatings, and discusses future directions in biomaterial research for preventing thrombosis. In addition, this paper comprehensively reviews several novel methods that either entirely prevent interaction between material surfaces and blood components or regulate the reaction of the coagulation cascade, thrombocytes, and leukocytes.

Bioinspired zwitterionic microgel-based coating: Controllable microstructure, high stability, and anticoagulant properties

Zwitterionic polymers have shown promising results in non-fouling and preventing thrombosis. However, the lack of controlled surface coverage hinders their application for biomedical devices. Inspired by the natural biological surfaces, a facile zwitterionic microgel-based coating strategy is developed by the co-deposition of poly (sulfobetaine methacrylate-co-2-aminoethyl methacrylate) microgel (SAM), polydopamine (PDA), and sulfobetaine-modified polyethyleneimine (PES). The SAMs were used to construct controllable morphology by using the PDA combined with PES (PDAS) as the intermediate layer, which can be easily modulated via adjusting the crosslinking degree and contents of SAMs. The obtained SAM/PDAS coatings exhibit high anti-protein adhesive properties and can effectively inhibit the adhesion of cells, bacteria, and platelet through the synergy of high deposition density and controllable morphology. In addition, the stability of SAM/PDAS coating is improved owing to the anchoring effects of PDAS to substrate and SAMs. Importantly, the ex vivo blood circulation test in rabbits suggests that the SAM/PDAS coating can effectively decrease thrombosis without anticoagulants. This study provides a versatile coating method to address the integration of zwitterionic microgel-based coatings with high deposition density and controllable morphology onto various substrates for wide biomedical device applications. STATEMENT OF SIGNIFICANCE: Thrombosis is a major cause of medical device implantation failure, which results in significant morbidity and mortality. In this study, inspired by natural biological surfaces (fish skin and vascular endothelial layer) and the anchoring ability of mussels, we report a convenient and efficient method to firmly anchor zwitterionic microgels using an oxidative co-deposition strategy. The prepared coating has excellent antifouling and antithrombotic properties through the synergistic effect of physical morphology and chemical composition. This biomimetic surface engineering strategy is expected to provide new insights into the clinical problems of blood-contacting devices related to thrombosis.

Recent advances of zwitterionic based topological polymers for biomedical applications

Zwitterionic polymers, comprising hydrophilic anionic and cationic groups with the same total number of positive and negative charges on the same monomer residue, have received increasing attention due to their...

Physically Switchable Antimicrobial Surfaces and Coatings: General Concept and Recent Achievements

Bacterial environmental colonization and subsequent biofilm formation on surfaces represents a significant and alarming problem in various fields, ranging from contamination of medical devices up to safe food packaging. Therefore, the development of surfaces resistant to bacterial colonization is a challenging and actively solved task. In this field, the current promising direction is the design and creation of nanostructured smart surfaces with on-demand activated amicrobial protection. Various surface activation methods have been described recently. In this review article, we focused on the "physical" activation of nanostructured surfaces. In the first part of the review, we briefly describe the basic principles and common approaches of external stimulus application and surface activation, including the temperature-, light-, electric- or magnetic-field-based surface triggering, as well as mechanically induced surface antimicrobial protection. In the latter part, the recent achievements in the field of smart antimicrobial surfaces with physical activation are discussed, with special attention on multiresponsive or multifunctional physically activated coatings. In particular, we mainly discussed the multistimuli surface triggering, which ensures a better degree of surface properties control, as well as simultaneous utilization of several strategies for surface protection, based on a principally different mechanism of antimicrobial action. We also mentioned several recent trends, including the development of the to-detect and to-kill hybrid approach, which ensures the surface activation in a right place at a right time.

Surface Design for Antibacterial Materials: From Fundamentals to Advanced Strategies

Healthcare-acquired infections as well as increasing antimicrobial resistance have become an urgent global challenge, thus smart alternative solutions are needed to tackle bacterial infections. Antibacterial materials in biomedical applications and hospital hygiene have attracted great interest, in particular, the emergence of surface design strategies offer an effective alternative to antibiotics, thereby preventing the possible development of bacterial resistance. In this review, recent progress on advanced surface modifications to prevent bacterial infections are addressed comprehensively, starting with the key factors against bacterial adhesion, followed by varying strategies that can inhibit biofilm formation effectively. Furthermore, "super antibacterial systems" through pre-treatment defense and targeted bactericidal system, are proposed with increasing evidence of clinical potential. Finally, the advantages and future challenges of surface strategies to resist healthcare-associated infections are discussed, with promising prospects of developing novel antimicrobial materials.

Biomimetic surface coatings for marine antifouling: Natural antifoulants, synthetic polymers and surface microtopography

Marine biofouling is a ubiquitous problem that accompanies human marine activities and marine industries. It exerts detrimental impacts on the economy, environment, ecology, and safety. Traditionally, mainstream approaches utilize metal ions to prevent biological contamination, but this also leads to environmental pollution and damage to the ecosystem. Efficient and environmentally friendly coatings are urgently needed to prevent marine devices from biofouling. Since nature is always the best teacher for humans, it offers us delightful thoughts on the research and development of high-efficiency, broad-spectrum and eco-friendly antifouling coatings. In this work, we focus on the research frontier of marine antifouling coatings from a bionic perspective. Enlightened by three distinctive dimensions of bionics: chemical molecule bionic, physiological mechanism bionic, and physical structure bionic, the research status of three main bioinspired strategies, which are natural antifoulants, bioinspired polymeric antifouling coatings, and biomimetic surface microtopographies, respectively, are demonstrated. The antifouling mechanisms are further interpreted based on biomimetic comprehension. The main fabrication methods and antifouling performances of these coatings are presented along with their advantages and drawbacks. Finally, the challenges are summarized, and future research prospects are proposed. It is believed that biomimetic antifouling strategies will contribute to the development of nontoxic antifouling techniques with exceptional repellency and stability.

Precisely Structured Nitric-Oxide-Releasing Copolymer Brush Defeats Broad-Spectrum Catheter-Associated Biofilm Infections In Vivo

Gram-negative bacteria cannot be easily eradicated by antibiotics and are a major source of recalcitrant infections of indwelling medical devices. Among various device-associated infections, intravascular catheter infection is a leading cause of mortality. Prior approaches to surface modification, such as antibiotics impregnation, hydrophilization, unstructured NO-releasing, etc., have failed to achieve adequate infection-resistant coatings. We report a precision-structured diblock copolymer brush (H(N)-b-S) composed of a surface antifouling block of poly(sulfobetaine methacrylate) (S) and a subsurface bactericidal block (H(N)) of nitric-oxide-emitting functionalized poly(hydroxyethyl methacrylate) (H) covalently grafted from the inner and outer surfaces of a polyurethane catheter. The block copolymer architecture of the coating is important for achieving good broad-spectrum anti-biofilm activity with good biocompatibility and low fouling. The coating procedure is scalable to clinically useful catheter lengths. Only the block copolymer brush coating ((H(N)-b-S)) shows unprecedented, above 99.99%, in vitro biofilm inhibition of Gram-positive and Gram-negative bacteria, 100-fold better than previous coatings. It has negligible toxicity toward mammalian cells and excellent blood compatibility. In a murine subcutaneous infection model, it achieves >99.99% biofilm reduction of Gram-positive and Gram-negative bacteria compared with <90% for silver catheter, while in a porcine central venous catheter infection model, it achieves >99.99% reduction of MRSA with 5-day implantation. This precision coating is readily applicable for long-term biofilm-resistant and blood-compatible copolymer coatings covalently grafted from a wide range of medical devices.

Engineering and Application Perspectives on Designing an Antimicrobial Surface

Infections, contaminations, and biofouling resulting from micro- and/or macro-organisms remained a prominent threat to the public health, food industry, and aqua-/marine-related applications. Considering environmental and drug resistance concerns as well as insufficient efficacy on biofilms associated with conventional disinfecting reagents, developing an antimicrobial surface potentially improved antimicrobial performance by directly working on the microbes surrounding the surface area. Here we provide an engineering perspective on the logic of choosing materials and strategies for designing antimicrobial surfaces, as well as an application perspective on their potential impacts. In particular, we analyze and discuss requirements and expectations for specific applications and provide insights on potential misconnection between the antimicrobial solution and its targeted applications. Given the high translational barrier for antimicrobial surfaces, future research would benefit from a comprehensive understanding of working mechanisms for potential materials/strategies, and challenges/requirements for a targeted application.

Recent Advances on Electrochemical Biosensing Strategies toward Universal Point-of-Care Systems

A number of very recently developed electrochemical biosensing strategies are promoting electrochemical biosensing systems into practical point-of-care applications. The focus of research endeavors has transferred from detection of a specific analyte to the development of general biosensing strategies that can be applied for a single category of analytes, such as nucleic acids, proteins, and cells. In this Minireview, recent cutting-edge research on electrochemical biosensing strategies are described. These developments resolved critical challenges regarding the application of electrochemical biosensors to practical point-of-care systems, such as rapid readout, simple biosensor fabrication method, ultra-high detection sensitivity, direct analysis in a complex biological matrix, and multiplexed target analysis. This Minireview provides general guidelines both for scientists in the biosensing research community and for the biosensor industry on development of point-of-care system, benefiting global healthcare.

Influence of Hydrophobic Cross-Linkers on Carboxybetaine Copolymer Stimuli Response and Hydrogel Biological Properties

Poly(carboxybetaine) (pCB) hydrogels do not elicit a foreign body response due to their low-fouling properties, making them ideal implantable materials for in vivo drug and cell delivery. Current reported pCB hydrogels are cross-linked using cytotoxic UV-initiated radical polymerization limiting clinical and in vivo translation. For clinical translation, we require in situ and biorthogonal cross-linking of pCB hydrogels that are both low-fouling and low-swelling to limit nonspecific interactions and minimize tissue damage, respectively. To this end, we synthesized carboxybetaine (CB) random copolymers (molecular weight (MW): ∼7-33 kDa; Đ: 1.1-1.36) containing azide (pCB-azide) or strained alkyne (Dibenzocyclooctyne (DBCO); pCB-DBCO) that rapidly cross-link upon mixing. Unlike CB homopolymers and other CB copolymers studied, high DBCO content pCB-DBCO₃₀ (30% DBCO mole fraction) is thermoresponsive with a upper critical solution temperature (UCST; cloud point of ∼20 °C at 50 g/L) in water due to electrostatic associations. Due to the antipolyelectrolyte effect, pCB-DBCO₃₀ is salt-responsive and is soluble even at low temperatures in 5 M NaCl, which prevents zwitterion electrostatic associations. pCB-azide and pCB-DBCO with 0.05 to 0.16 cross-linker mole fractions rapidly formed 10 wt % hydrogels upon mixing that were low-swelling (increase of ∼10% in wet weight) while remaining low-fouling to proteins (∼10-20 μg cm^-2) and cells, making them suitable for in vivo applications. pCB-X₃₁ hydrogels composed of pCB-azide₃₂ and pCB-DBCO₃₀ formed opaque gels in water and physiological conditions that shrunk to ∼70% of their original wet weight due to pCB-DBCO₃₀'s greater hydrophobicity and interchain electrostatic interactions, which promotes nonspecific protein adsorption (∼35 μg cm^-2) and cell binding. Once formed, the electrostatic interactions in pCB-X₃₁ hydrogels are not fully reversible with heat or salt. Although, pCB-X₃₁ hydrogels are transparent when initially prepared in 5 M NaCl. This is the first demonstration of a thermo- and salt-responsive CB copolymer that can tune hydrogel protein and cell fouling properties.

Synthetic Polyampholytes as Macromolecular Cryoprotective Agents

A series of polyampholytes based on different molar ratios on N, N-dimethylaminopropyl methacrylamide (DMAPMA), acrylic acid (AA), and optionally, N- tert-butylacrylamide ( t-BuAAm), were prepared by free radical copolymerization, and tested as DMSO-free cryoprotective agents for 3T3 fibroblast cells by using a standard freeze-rethaw protocol. Polybetaines prepared by reaction of DMAPMA homo and copolymers with 1,3-propane sultone were used as additional controls. Results showed strong effects of copolymer composition, molecular weight, polymer and NaCl concentrations, on post-thaw cell viability. Binary (DMAPMA/AA) copolymers showed best post-thaw cell viability of 70% at a 30/70 mol % ratio of DMAPMA/AA, which increased to 90% upon introduction of 9 mol % t-BuAAm while maintaining the 30/70 mol % cation/anion ratio. The use of acrylamide linkages in DMAPMA ensures absence of hydrolytic loss of cationic side chains. These polyampholytes were found to decrease ice crystal size and to form a polymer-rich, ice-free layer around cells, reducing damage from intercellular ice crystals during both freezing and thawing steps. These polyampholytes also dehydrate cells during freezing, which helps protect cells from intracellular ice damage. While cell viability immediately after thawing was high, subsequent culturing revealed poor attachment and long-term viability, which is attributed to residual cell damage from intracellular ice formation. Addition of 2 wt % DMSO or 1% BSA to the polymer-based freeze medium was found to mitigate this damage and result in post-thaw viabilities matching those achieved with 10 wt % DMSO.

Radical Cation Initiated Surface Polymerization on Photothermal Rubber for Smart Antifouling Coatings

Biofouling on surfaces of various materials has attracted considerable attention in biomedical and marine industries. Surface grafting based on covalent surface-initiated polymerization offers a popular route to address this problem by providing diverse robust polymer coatings capable of preventing the biofouling in complex environments. However, the existing methods for synthesizing polymer coatings are complicated and rigorous, or require special catalysts, greatly limiting their practical applications. In this work, a radical-cation-based surface-initiated polymerization protocol to graft the surface of darkened trans-polyisoprene (TPI) rubber with a thermo-responsive smart polymer, poly(N-isopropylacrylamide) (PNIPAM), through a simple iodine doping process is reported. A series of characterizations were performed to provide adequate evidence to confirm the successful grafting. Combining the thermal sensitivity of PNIPAM with the photothermal conversion ability of the darkened rubber, efficient bacteria-killing and antifouling capabilities were successfully achieved as a result of temperature-controlled iodine release and switchable amphiphilicity of PNIPAM.

Strategies to prevent the occurrence of resistance against antibiotics by using advanced materials

Drug resistance occurrence is a global healthcare concern responsible for the increased morbidity and mortality in hospitals, time of hospitalisation and huge financial loss. The failure of the most antibiotics to kill "superbugs" poses the urgent need to develop innovative strategies aimed at not only controlling bacterial infection but also the spread of resistance. The prevention of pathogen host invasion by inhibiting bacterial virulence and biofilm formation, and the utilisation of bactericidal agents with different mode of action than classic antibiotics are the two most promising new alternative strategies to overcome antibiotic resistance. Based on these novel approaches, researchers are developing different advanced materials (nanoparticles, hydrogels and surface coatings) with novel antimicrobial properties. In this review, we summarise the recent advances in terms of engineered materials to prevent bacteria-resistant infections according to the antimicrobial strategies underlying their design.

Surface engineering of titanium implants with enzyme-triggered antibacterial properties and enhanced osseointegrationin vivo

A catechol-functionalized coating on a Van-loaded Ti implant achieves enhanced osseointegration and effective inhibition of bacterial adhesion and enzyme-triggered antibacterial drug release.

A mussel-inspired chimeric protein as a novel facile antifouling coating

A mussel-inspired chimeric protein as a multifunctional coating was engineered, which can anchor onto various substrates readily and exhibits superior antifouling properties.

L-carnitine Derived Zwitterionic Betaine Materials

An L-carnitine derived zwitterionic betaine material was developed. The synthesized L-carnitineMA was the first zwitterionic betaine monomer from natural feedstocks. In the models of Surface coating and hydrogel, the L-carnitineMA material was able to achieve superior anti-fouling performance as good as state-of-the-art zwitterionic betaine materials.

In Vivo Anti-Biofilm and Anti-Bacterial Non-Leachable Coating Thermally Polymerized on Cylindrical Catheter

Catheters are indispensable tools of modern medicine, but catheter-associated infection is a significant clinical problem, even when stringent sterile protocols are observed. When the bacteria colonize catheter surfaces, they tend to form biofilms making them hard to treat with conventional antibiotics. Hence, there is a great need for inherently antifouling and antibacterial catheters that prevent bacterial colonization. This paper reports the preparation of nonleachable antibiofilm and antibacterial cationic film coatings directly polymerized from actual tubular silicone catheter surfaces via the technique of supplemental activator and reducing agent surface-initiated atom-transfer radical polymerization (SARA SI-ATRP). Three cross-linked cationic coatings containing (3-acrylamidopropyl) trimethylammonium chloride (AMPTMA) or quaternized polyethylenimine methacrylate (Q-PEI-MA) together with a cross-linker (polyethylene glycol dimethacrylate, PEGDMA) were tested. The in vivo antibacterial and antibiofilm effect of these nonleachable covalently linked coatings (using a mouse catheter model) can be tuned to achieve 1.95 log (98.88%) reduction and 1.26 log (94.51%) reduction of clinically relevant pathogenic bacteria (specifically with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VRE)). Our good in vivo bactericidal killing results using the murine catheter-associated urinary tract infection (CAUTI) model show that SARA SI-ATRP grafting-from technique is a viable technique for making nonleachable antibiofilm coating even on "small" (0.30/0.64 mm inner/outer diameter) catheter.

Superdurable Coating Fabricated from a Double-Sided Tape with Long Term "Zero" Bacterial Adhesion

There is no coating technology currently available to prevent the notorious biofilm formation issue. Here, a potential solution to fully address this tough issue is reported by developing a super-antifouling coating. The use of zwitterionic hydrogel (a double-sided tape) and commercial superglue is combined and a durable and ultrarobust antifouling zwitterionic (DURA-Z) coating is created that can be easily and universally applied on common substrates. Commercial superglue mostly for binding hydrophobic materials is used to strongly immobilize the superhydrophilic DURA-Z coating through interpenetration. DURA-Z coating effectively solves several key challenges preventing the current antifouling coatings from practical use, including difficult fabrication, low efficacy, poor toughness, and durability. The fabricated DURA-Z coating retains antifouling property after 90 d of immersion in water, 50 d of buffer shearing, and 30 d of water flushing, and after repeated knife scratch and sandpaper abrasion under 570 kPa. The DURA-Z coating achieves a rarely reported long-term biofilm resistance to both Gram-positive and Gram-negative bacteria and fungi: it remains almost "zero" microbe adhesion after continuously challenged by more than 109 cells mL-1 culture medium for 30 d.