The recent advances in surface antibacterial strategies for biomedical catheters

Poly(sulfobetaine) versus poly(ethylene glycol) based copolymer modified polyurethane catheters for antifouling

Polyurethane (PU) catheters are commonly used in clinical treatment. However, the hydrophobic nature of the PU catheter surface leads to adhesion or adsorption to platelets, proteins, bacteria, and other molecules when used in human treatment. To achieve a surface with strong hydrophilicity, high stability and excellent biocompatibility, it is necessary to functionalize the PU catheters. In this paper, a coating with antifouling function was constructed on the surface of PU catheters using plasma technology and an amide coupling reaction. A series of characterization methods, including X-ray photoelectron spectroscopy (XPS), water contact angles (WCA), and atomic force microscopy (AFM), were used to prove the successful modification of the polymer coatings. The coatings showed good stability under conditions such as PBS (pH 7.4, 720 h), 75% ethanol (6 h) and 1 wt% SDS (10 min). Additionally, the coatings exhibit excellent hemocompatibility and antibacterial properties. The PU/PEI/PCSB coating has the best anti-fouling performance among them, which means that using the PCSB copolymer has the potential to modify different clinical catheters into highly effective antifouling coatings.

Hydroxyl silicone oil grafting onto a rough thermoplastic polyurethane surface created durable super-hydrophobicity

Indwelling medical catheters are frequently utilized in medical procedures, but they are highly susceptible to infection, posing a vital challenge for both health workers and patients. In this study, the superhydrophobic micro-nanostructure surface was constructed on the surface of thermoplastic polyurethane (TPU) membrane using heavy calcium carbonate (CaCO3) template. To decrease the surface free energy, hydroxyl silicone oil was grafted onto the surface, forming a super-hydrophobic surface. The water contact angle (WCA) increased from 91.1° to 143 ± 3° when the concentration of heavy calcium CaCO3 was 20% (weight-to-volume (w/v)). However, the increased WCA was unstable and tended to decrease over time. After grafting hydroxyl silicone oil, the WCA rose to 152.05 ± 1.62° and remained consistently high for a period of 30 min. Attenuated total reflection infrared spectroscopy (ATR-FTIR) analysis revealed a chemical crosslinking between silicone oil and the surface of TPU. Furthermore, Scanning electron microscope (SEM) image showed the presence of numerous nanoparticles on the micro surface. Atomic force microscope (AFM) testing indicated a significant improvement in surface roughness. This method of creating a hydrophobic surface demonstrated several advantages, including resistance to cell, bacterial, protein, and platelet adhesion and good biosecurity. Therefore, it holds promising potential for application in the development of TPU-based medical catheters with antibacterial properties.

Metal-Organic Framework-Based Antimicrobial Touch Surfaces to Prevent Cross-Contamination

Infection diseases are a major threat to global public health, with nosocomial infections being of particular concern. In this context, antimicrobial coatings emerge as a promising prophylactic strategy to reduce the transmission of pathogens and control infections. Here, antimicrobial door handle covers to prevent cross-contamination are prepared by incorporating iodine-loaded UiO-66 microparticles into a potentially biodegradable polyurethane polymer (Baycusan eco E 1000). These covers incorporate MOF particles that serve as both storage reservoirs and delivery systems for the biocidal iodine. Under realistic touching conditions, the door handle covers completely inhibit the transmission of Gram-positive bacterial species (Staphylococcus aureus, and Enterococcus faecalis), Gram-negative bacterial species (Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii), and fungi (Candida albicans). The covers remain effective even after undergoing multiple contamination cycles, after being cleaned, and when tinted to improve discretion and usability. Furthermore, as the release of iodine from the door handle covers follow hindered Fickian diffusion, their antimicrobial lifetime is calculated to be as long as approximately two years. Together, these results demonstrate the potential of these antimicrobial door handle covers to prevent cross-contamination, and underline the efficacy of integrating MOFs into innovative technologies.

Tackling catheter-associated urinary tract infections with next-generation antimicrobial technologies

Urinary catheters and other medical devices associated with the urinary tract such as stents are major contributors to nosocomial urinary tract infections (UTIs) as they provide an access path for pathogens to enter the bladder. Considering that catheter-associated urinary tract infections (CAUTIs) account for approximately 75% of UTIs and that UTIs represent the most common type of healthcare-associated infections, novel anti-infective device technologies are urgently required. The rapid rise of antimicrobial resistance in the context of CAUTIs further highlights the importance of such preventative strategies. In this review, the risk factors for pathogen colonization in the urinary tract are dissected, taking into account the nature and mechanistics of this unique environment. Moreover, the most promising next-generation preventative strategies are critically assessed, focusing in particular on anti-infective surface coatings. Finally, emerging approaches in this field and their likely clinical impact are examined.

Hydrophilic biomaterial intravenous hydrogel catheter for complication reduction in PICC and midline catheters

INTRODUCTION

More than 30% of peripherally inserted central catheters (PICCs) and midline catheters experience complications. Most complications are related to thrombotic cellular adherence to catheter materials.

AREAS COVERED

This manuscript outlines PICC and midline catheter complications, the need to reduce complications and how hydrogel catheters may provide a solution to address these unmet needs based on available evidence.

EXPERT OPINION

Patients commonly require PICC or midline catheters for treatment to establish a reliable form of intravenous access. Catheters, while reliable in most cases, are not without complications, including occlusion, thrombosis and infection, each related to cellular adherence to the catheter material. Hydrophilic catheter coatings and composites have been developed to mitigate these thrombotic complications, reduce adherence of blood and bacterial cells to catheters and provide greater patient safety with these devices. Hydrogel materials are highly biocompatible and have been effective in reducing cellular adherence and the formation of biofilms on surfaces. Smooth hydrophilic catheter surfaces are potentially more comfortable for the patient, with reduced friction during insertion and removal. A catheter constructed of hydrophilic biomaterial, a hydrogel composite material, may minimize thrombotic complications in PICC and midline catheters, improving catheter performance and outcomes for patients.

A Facile Surface Modification Scheme for Medical-Grade Titanium and Polypropylene Using a Novel Mussel-Inspired Biomimetic Polymer with Cationic Quaternary Ammonium Functionalities for Antibacterial Application

Medical device-associated infection remains a critical problem in the healthcare setting. Different clinical- or device-related methods have been attempted to reduce the infection rate. Among these approaches, creating a surface with bactericidal cationic functionality has been proposed. To do so, a sophisticated multi-step chemical procedure would be needed. Instead, a simple immersion approach was utilized in this investigation to render the titanium and polypropylene surface with the quaternary ammonium functionality by using a mussel-inspired novel lab-synthesized biomimetic catechol-terminated polymer, PQA-C8. The chemical oxidants, CuSO4/H2O2, as well as dopamine, were added into the novel PQA-C8 polymer immersion solution for one-step surface modification. Additionally, a two-step immersion scheme, in which the polypropylene substrate was first immersed in the dopamine solution and then in the PQA-C8 solution, was also attempted. Surface analysis results indicated the surface characteristics of the modified substrates were affected by the immersion solution formulation as well as the procedure utilized. The antibacterial assay has shown the titanium substrates modified by the one-step dopamine + PQA-C8 mixtures with the oxidants added and the polypropylene modified by the two-step scheme exhibited bacterial reduction percentages greater than 90% against both Gram-positive S. aureus and Gram-negative E. coli and these antibacterial substrates were non-cytotoxic.

In Situ Growth of Functional Hydrogel Coatings by a Reactive Polyurethane for Biomedical Devices

Surface modification of thermoplastic polyurethane (TPU) could significantly enhance its suitability for biomedical devices and public health products. Nevertheless, customized modification of polyurethane surfaces with robust interfacial bonding and diverse functions via a simple method remains an enormous challenge. Herein, a novel thermoplastic polyurethane with a photoinitiated benzophenone unit (BPTPU) is designed and synthesized, which can directly grow functional hydrogel coating on polyurethane (PU) in situ by initiating polymerization of diverse monomers under ultraviolet irradiation, without the involvement of organic solvent. The resulting coating not only exhibits tissue-like softness, controllable thickness, lubrication, and robust adhesion strength but also provides customized functions (i.e., antifouling, stimuli-responsive, antibacterial, and fluorescence emission) to the original passive polymer substrates. Importantly, BPTPU can be blended with commercial TPU to produce the BPTPU-based tube by an extruder. Only a trace amount of BPTPU can endow the tube with good photoinitiated capacity. As a proof of concept, the hydrophilic hydrogel-coated BPTPU is shown to mitigate foreign body response in vivo and prevent thrombus formation in rat blood circulation without anticoagulants in vitro. This work offers a new strategy to guide the design of functional polyurethane, an elastomer-hydrogel composite, and holds great prospects for clinical translation.

Novel Antibacterial Materials and Coatings-A Perspective by the Editors

The fight between humans and bacteria has escalated to a new level.

A robust mixed-charge zwitterionic polyurethane coating integrated with antibacterial and anticoagulant functions for interventional blood-contacting devices

Antifouling coatings based on zwitterionic polymers have been widely applied for surface modification of interventional blood-contacting devices to combat thrombosis and infection. However, the weak adhesion stability of the zwitterionic coating to the device surface is still the key challenge. In this work, biocompatible mixed-charge zwitterionic polyurethane (MPU) polymers, that bear equal amounts of cationic quaternary amine groups and anionic carboxyl groups, were developed and further uniformly dip-coated onto a thermoplastic polyurethane (TPU) substrate with a commercial aliphatic isocyanate cross-linker (AIC). During the curing process, AIC not only crosslinks MPU chains into a polymer network but also reacts with hydroxyl groups of TPU to interlink the polymer network to the substrate, resulting in a cross-linking reinforced MPU coating (CMPU) with excellent mechanical robustness and adhesion strength. Taking advantage of the mixed-charge feature, the final zwitterionic CMPU coating exhibits both excellent antifouling and antibacterial activities against protein adsorption and bacterial growth, respectively, which is beneficial for effectively inhibiting the occurrence of in vivo infection. Moreover, anticoagulation studies show that CMPU-coated TPU catheters can also prevent the formation of blood clots in ex vivo rabbit blood circuits without anticoagulants. Hence, the designed CMPU coating has immense potential to address thrombosis and infection for interventional blood-contacting devices.

Mussel-inspired proteins functionalize catheter with antifouling and antibacterial properties

Bacterial adhesion and subsequent biofilm formation on catheter can cause inevitably infection. The development of multifunctional antibacterial coating is a promising strategy to resist the bacteria adhesion and biofilm formation. Herein, a mussel-inspired chimeric protein MZAgP is prepared and employed to modify a variety of polymeric catheters. The MZAgP is composed of mussel-adhesive peptide, zwitterionic peptide, and silver-binding peptide, which can endow catheters with antifouling, bactericidal and biocompatibility performances. Expectedly, negligible biofilm is observed on the MZAgP coated catheters after incubating with bacteria for 120 h. And ignorable hemolysis and cytotoxicity are obtained on coated catheters. In addition, the modified catheters also display persistent antifouling and bacteriostatic properties throughout 168 h under hydrodynamic conditions. Moreover, the coated catheters still remain excellent antifouling and antibacterial properties even after 2 months of storage. This multifunctional coating may be promising as antibacterial and antibiofilm material, and the coated catheters are potential in clinical application.

Can Superhydrophobic PET Surfaces Prevent Bacterial Adhesion?

Prevention of bacterial adhesion is a way to reduce and/or avoid biofilm formation, thus restraining its associated infections. The development of repellent anti-adhesive surfaces, such as superhydrophobic surfaces, can be a strategy to avoid bacterial adhesion. In this study, a polyethylene terephthalate (PET) film was modified by in situ growth of silica nanoparticles (NPs) to create a rough surface. The surface was further modified with fluorinated carbon chains to increase its hydrophobicity. The modified PET surfaces presented a pronounced superhydrophobic character, showing a water contact angle of 156° and a roughness of 104 nm (a considerable increase comparing with the 69° and 4.8 nm obtained for the untreated PET). Scanning Electron Microscopy was used to evaluate the modified surfaces morphology, further confirming its successful modification with nanoparticles. Additionally, a bacterial adhesion assay using an Escherichia coli expressing YadA, an adhesive protein from Yersinia so-called Yersinia adhesin A, was used to assess the anti-adhesive potential of the modified PET. Contrarily to what was expected, adhesion of E. coli YadA was found to increase on the modified PET surfaces, exhibiting a clear preference for the crevices. This study highlights the role of material micro topography as an important attribute when considering bacterial adhesion.

Recent nanotechnology-based strategies for interfering with the life cycle of bacterial biofilms

Biofilm formation plays an important role in the resistance development in bacteria to conventional antibiotics. Different properties of the bacterial strains within biofilms compared with their planktonic states and the protective effect of extracellular polymeric substances contribute to the insusceptibility of bacterial cells to conventional antimicrobials. Although great effort has been devoted to developing novel antibiotics or synthetic antibacterial compounds, their efficiency is overshadowed by the growth of drug resistance. Developments in nanotechnology have brought various feasible strategies to combat biofilms by interfering with the biofilm life cycle. In this review, recent nanotechnology-based strategies for interfering with the biofilm life cycle according to the requirements of different stages are summarized. Additionally, the importance of strategies that modulate the bacterial biofilm microenvironment is also illustrated with specific examples. Lastly, we discussed the remaining challenges and future perspectives on nanotechnology-based strategies for the treatment of bacterial infection.

Regulable Polyelectrolyte-Surfactant Complex for Antibacterial Biomedical Catheter Coating via a Readily Scalable Route

Constructing multifunctional surfaces is one of the practical approaches to address catheter-related multiple complications but is generally time-consuming and substrate-dependent. Herein, a novel anti-adhesion, antibacterial, low friction, and robustness coating on medical catheters are developed via a universal and readily scalable method based on a regulable polyelectrolyte surfactant complex. The complex is rapidly assembled in one step by electrostatic and hydrophobic interactions between organosilicon quaternary ammonium surfactant (N⁺ _Si ) and adjustable polyelectrolyte with cross-linkable, anti-adhesive, and anionic groups. The alcohol-soluble feature of the complex is conducive to the rapid formation of coatings on any medical device with arbitrary shapes via dip coating. Different from the conventional polyelectrolyte-surfactant complex coating, the regulated complex coating with nonleaching mode could be stable in harsh conditions (high concentration salt solution, organic reagents, etc.) because of the cross-linked structure while improving the biocompatibility and reducing the adhesion of various bacteria, proteins, and blood cells. The coated catheter exhibits good antibacterial infection in vitro and in vivo, owing to the synergistic effect of N⁺ _Si and zwitterionic groups. Therefore, the rationally designed complex supplies a facile coating approach for the potential development in combating multiple complications of the medical catheter.

A randomized, single-blind, multi-center clinical observational study of a new super lubricath coating catheter latex catheters using in urethral catheterization

Polymer polyvinylpyrrolidone (PVP) can be described as the main coating. After heating and curing, it is able to build a strong adhesion to the latex catheter for creating a durable and effective hydrophilic coating. In this study, we aim to explore the advantages and disadvantages of the new super lubricath latex catheter PVP coating compared with the common latex catheter. 148 patients who participated in the study were completely randomly divided into two groups, the observation group and the control group. When the urinary catheter was incubated, indwelling in subjects' body, and removed from the subjects, the researchers accordingly recorded the subjects' comfort feedback, device safety evaluation and the patient's vital signs, relevant blood and urine examination index, electrocardiogram (ECG) changes and recorded various adverse events. PVP super lubricath coating latex catheter offered better comfort, less damage to the urethra, and no significant disadvantage in safety compared to regular latex catheters, improving quality of care and patient satisfaction compared to regular latex urinary catheters.

Design of Thermoplastic Polyurethanes with Conferred Antibacterial, Mechanical, and Cytotoxic Properties for Catheter Application

Thermoplastic polyurethanes (TPUs) are proposed as suitable solution for the fabrication of biocompatible catheters with appropriate mechanical parameters and confirmed antibacterial and cytocompatible properties. For this purpose, a series of quaternary ammonium salts (QASs) and quaternary phosphonium salts (QPSs) based monomers were prepared followed by the determination of their minimal inhibitory concentrations (MICs) against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Pseudomonas aeruginosa (P. aeruginosa). A combination of the most active ammonium (QAS-C₁₄) and phosphonium (QPS-TOP) salts led to a MIC down to 2.4 μg/mL against S. aureus and 9 μg/mL against P. aeruginosa, corroborating the existence of a synergistic effect. These quaternary onium salt (QOS) units were successfully incorporated along the polymer chain, as part of a two-step synthesis approach. The resulting TPU-QOS materials were subsequently characterized through thermal, mechanical, and surface analyses. TPU-Mix (combining the most active QAS-C₁₄ and QPS-TOP units) showed the highest antibacterial efficiency, confirming the synergistic effect between both QOS groups. Finally, an MTT assay on the SiHa cell line revealed the low cytotoxicity level of these polymeric films, making these materials suitable for biomedical application. To go one step further in the preindustrialization approach, proof of concept regarding the catheter prototype fabrication based on TPU-QAS/QPS was validated by extrusion.

Self-Disinfecting Urethral Catheter to Overcome Urinary Infections: From Antimicrobial Photodynamic Action to Antibacterial Biochemical Entities

Medical-device-related infections are considered a worldwide public health problem. In particular, urinary catheters are responsible for 75% of cases of hospital urinary infections (a mortality rate of 2.3%) and present a high cost for public and private health systems. Some actions have been performed and described aiming to avoid it, including clinical guidelines for catheterization procedure, antibiotic prophylaxis, and use of antimicrobial coated-urinary catheters. In this review paper, we present and discuss the functionalization of urinary catheters surfaces with antimicrobial entities (e.g., photosensitizers, antibiotics, polymers, silver salts, oxides, bacteriophage, and enzymes) highlighting the immobilization of photosensitizing molecules for antimicrobial photodynamic applications. Moreover, the characterization techniques and (photo)antimicrobial effects of the coated-urinary catheters are described and discussed. We highlight the most significant examples in the last decade (2011-2021) concerning the antimicrobial coated-urinary catheter and their potential use, limitations, and future perspectives.

Sustainable conversion of saturated adsorbents (SAs) from wastewater into value-added products: future prospects and challenges with toxic per- and poly-fluoroalkyl substances (PFAS)

Following circular economy principles, the reuse or recycling of saturated adsorbents (SAs or adsorbate-laden adsorbents) into a low-cost engineered product is a valuable alternative to eliminate secondary pollution after adsorption. This review evaluates the application of SAs for the generation of products that can serve as (i) antimicrobial agents or disinfectants, (ii) materials for civil construction, (iii) catalysts, (iv) fertilizers, and (v) secondary adsorbents. The importance of SAs configuration in terms of functional groups, surface area and pore morphology played a crucial role in their reutilization. The SAs-laden silver ions (Ag⁺) strongly inhibit (~ 99%) the growth of Escherichia coli and Staphylococcus aureus microbes found in drinking and wastewaters. The intra-solidification of SAs containing toxic metal pollutants (As³⁺ and F^-) with cementitious materials can effectively reduce their leaching below permissible limits of USEPA standards for their utility as additives in construction work. The existence of transition metal ions (Cu²⁺, Cr^3+/6+, Ni²⁺) on the surface of SAs boosted activity and selectivity towards the desired product during catalytic oxidation, degradation, and conversion processes. The thermally recycled SAs can assist in the secondary adsorption of pollutants from another waste solution due to a larger surface area (> 1000 m²g^-1). However, there are chances that the SAs discussed above will contain traces of PFAS. The article summarizes the challenges, performance efficacy, and future prospects at the end of each value-added product. We also highlight critical challenges for managing PFAS-laden SAs and stimulate new perspectives to minimize PFAS in air, water, and soils.

Bioinspired nanopillar surface for switchable mechano-bactericidal and releasing actions

Constructing safe and effective antibacterial surfaces has continuously received great attention, especially in healthcare-related fields. Bioinspired mechano-bactericidal nanostructure surfaces could serve as a promising strategy to reduce surface bacterial contamination while avoiding the development of antibiotic resistance. Although effective, these nanostructure surfaces are prone to be contaminated by the accumulation of dead bacteria, inevitably compromising their long-term antibacterial activity. Herein, a bioinspired nanopillar surface with both mechano-bactericidal and releasing actions is developed, via grafting zwitterionic polymer (poly(sulfobetaine methacrylate) (PSBMA)) on ZnO nanopillars. Under dry conditions, this nanopillar surface displays remarkable mechano-bactericidal activity, because the collapsed zwitterionic polymer layer makes no essential influence on nanopillar structure. Once being incubated with aqueous solution, the surface could readily detach the killed bacteria and debris, owing to the swelling of the zwitterionic layer. Consequentially, the surface antibacterial performances can be rapidly and controllably switched between mechano-bactericidal action and bacteria-releasing activity, guaranteeing a long-lasting antibacterial performance. Notably, these collaborative antibacterial behaviors are solely based on physical actions, avoiding the risk of triggering bacteria resistance. The resultant nanopillar surface also enjoys the advantages of substrate-independency and good biocompatibility, offering potential antibacterial applications for biomedical devices and hospital surfaces.

Mussel-Inspired Multicomponent Codeposition Strategy toward Antibacterial and Lubricating Multifunctional Coatings on Bioimplants

Bacterial infections and limited surface lubrication are the two key challenges for bioimplants in dynamic contact with tissues. However, the simultaneous lubricating and antibacterial properties of the bioimplants have rarely been investigated. In this work, we successfully developed a multifunctional coating with simultaneous antibacterial and lubricating properties for surface functionalization of bioimplant materials. The multifunctional coating was fabricated on a polyurethane (PU) substrate via polydopamine (PDA)-assisted multicomponent codeposition, containing polyethyleneimine (PEI) and trace amounts of copper (Cu) as synergistic antibacterial components and zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) as the lubricating component. The obtained PDA(Cu)/PEI/PMPC coating showed excellent antibacterial activity (antibacterial efficiency: ∼99%) to both Escherichia coli and Staphylococcus aureus compared with bare PU. The excellent antibacterial properties were attributed to the combined effect of anti-adhesion capability of hydrophilic PMPC and PEI and bactericidal activity of Cu in the coating. Meanwhile, the coefficient of friction of the coating was significantly decreased by ∼52% compared with bare PU owing to the high hydration feature of PMPC, suggesting the superior lubricating property. Furthermore, the PDA(Cu)/PEI/PMPC coating was highly biocompatible toward human umbilical vein endothelial cells demonstrated by in vitro cytotoxicity tests. This study not only contributes to the chemistry of PDA-assisted multicomponent codeposition but also provides a facile and practical way for rational design of multifunctional coatings for medical devices.

One-step coordination of metal-phenolic networks as antibacterial coatings with sustainable and controllable copper release for urinary catheter applications

Catheter-associated urinary tract infections (CAUTIs) draw great concern due to increased demand for urinary catheters in hospitalization. Encrustation caused by urinary pathogens, especially Proteus mirabilis, results in blocking of the catheter lumen and further infections. In this study, a facile and low-cost surface modification strategy of urinary catheters was developed using one-step coordination of tannic acid (TA) and copper ions. The copper content of the coating could be manipulated by the number of TA-Cu (TC) layers, and the coating released copper in a pH-responsive manner. The coating exhibited high antibacterial efficiency (killed >99% of planktonic bacteria, and reduced biofilm coverage to <1% after 24 h) due to the synergistic antimicrobial effect of TA and copper ions. In vivo study with a rabbit model indicated that with two TC layers, the coated catheter could effectively inhibit bacterial growth in urine and colonization on the surface, and reduce encrustation formation. In addition, the TC-coated catheter exhibited better tissue compatibility compared to the unmodified catheter, probably due to the antibacterial performance of the coating. Such a straightforward coating strategy with good in vitro and in vivo antibacterial properties and biocompatibility holds great promise for combating CAUTIs in clinical practice.

Combating Bacterial Biofilm Formation in Urinary Catheter by Green Silver Nanoparticle

Urinary catheters are commonly associated with urinary tract infections. This study aims to inhibit bacterial colonisation and biofilm of urinary tract catheters. Silicon catheter pieces were varnished with green silver nanoparticles (AgNPs) using Pistacia lentiscus mastic to prevent bacterial colonisation. Pomegranate rind extract was used to synthesize AgNPs. AgNPs were characterized by UV-Vis spectroscopy, X-ray crystallography, and transmission electron microscopy (TEM). Results obtained revealed that the size of most AgNPs ranged between 15–25 nm and they took crystallised metal and oxidised forms. The amounts of released silver ions from 1 cm pieces of catheters coated with AgNPs were estimated for five days and ranged between 10.82 and 4.8 µg. AgNPs coated catheters significantly inhibited the colonisation of catheters by antibiotic-resistant clinical Gram-positive (Staphylococcus epidermidis and Staphylococcus aureus) and Gram-negative (Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa) bacteria. AgNPs-varnish was more active against Gram-negative bacteria than Gram-positive bacteria. The significant inhibitory effect of coated catheters lasted for 72 h for both Gram-positive and Gram-negative bacteria. Varnishing catheters with AgNPs may help to prevent bacterial colonisation and infections.

Biocompatible tellurium nanoneedles with long-term stable antibacterial activity for accelerated wound healing

Tellurium (Te) nanomaterials (NMs) have emerged as a new antibacterial candidate to respond to the complex global health challenge of bacterial resistance. Herein, Te nanoneedles (NNs) that act both chemically and physically on bacteria are synthesized by a facile method using Na₂TeO₃, urea and glucose. It is found that the prepared Te NNs have a strong affinity to the cell membrane of bacteria and subsequently promote the generation of reactive oxygen species (ROS) in bacteria, resulting in an excellent antibacterial effect toward Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). What's more, this needle-like morphology also can physically damage the bacterial cell membranes. The Te NNs per se are inert in mammalian cells to produce ROS at a proper concentration, indicating considerable biocompatibility of this material. As a proof-of-concept, the antibacterial Te NNs were used as an anti-inflammatory reagent for promoting bacteria-infected wound healing in vivo, during which Te NNs caused no evident side effects to major organs in mice. Additionally, the antibacterial activity is maintained in the presence of surface oxidation of Te NNs after long-term dispersion in phosphate buffered saline solution. The needle-like Te NMs with long-term antibacterial stability and good biocompatibility have great potential for the treatment of associated infectious diseases.

Amino acid-mediated negatively charged surface improve antifouling and tribological characteristics for medical applications

To prevent infections associated with biomedical catheters, various antimicrobial coatings have been investigated. However, those materials do not provide consistent antibacterial effects or biocompatibility, generally, due to degradation of the coating materials, in vivo. Additionally, biomedical catheters must have low surface friction to reduce tribological damage. In this study, we developed an antifouling surface composed of biocompatible amino acids (leucine, taurine, and aspartic acid) on polyimide, via modification using a series of facile immersion steps with waterborne reactions. The naturally derived amino acid could be formed highly biostable amide bonds on the polyimide surface like peptides. The amino acid-modified surface formed a water layer with antifouling performance through the hydrophilic properties of amino acids. Amino acid-mediated modification reduced adhesion up to 84.45% and 94.81% against Escherichia coli and Staphylococcus epidermidis, respectively, and exhibited an excellent prevention to adhesion against the proteins, albumin and fibrinogen. Evaluation of the surface friction of the catheter revealed a dramatic reduction in the tribological force after amino acid modification on polyimide that of 0.81 N to aspartic acid of 0.44 N. These results clearly demonstrate a reduced occurrence of infections, thrombi and tribological damage following the relatively facile surface modification of catheters. The proposed modification method can be used in a continuous manufacturing process via using the same time of modification steps for the easy producing the product. Moreover, the method uses biocompatible naturally derived materials and can be applied to medical equipment that requires biocompatibility and biofunctionality with polyimide surfaces.

Overview of the development of slippery surfaces: Lubricants from presence to absence

The superhydrophobic surfaces inspired by the lotus have excellent performances and are known for their low contact angle hysteresis and smooth surfaces. However, there are still some problems, such as the unstable structure, poor durability, high product cost and so on that need to be improved. Those issues can be avoided via liquid-infused surfaces(LIS), which are inspired by Nepenthes and consist of a mico-nano structured substrate and a smooth continuous atomic-grade lubricant. Compared with superhydrophobic surfaces, LIS not only achieves the same hydrophobic properties but also has smaller contact angle hysteresis, smoother surface, more stable structure and lower preparation cost. Although the existence of a lubricant layer improves the performance of the material, it also leaves a hidden danger, which is easy to lose and leads to the deterioration of the durability of the material. Therefore, the lubricant-free slipper materials have attracted more and more attention in recent years due to their low volatility, good durability and excellent lubrication performance. In this review, the types of LIS lubricants and their physicochemical properties were summarized at the beginning and then the applications of LIS in various fields were introduced. At the end of this paper, some solid lubricants and their applications were described, and the future development prospects of LIS lubricants also were expected.

Antibacterial surfaces: Strategies and applications

Antibacterial surfaces are surfaces that can resist bacteria, relying on the nature of the material itself. It is significant for safe food and water, human health, and industrial equipment. Biofilm is the main form of bacterial contamination on the material surface. Preventing the formation of biofilm is an efficient way to develop antibacterial surfaces. The strategy for constructing the antibacterial surface is divided into bacteria repelling and bacteria killing based on the formation of the biofilm. Material surface wettability, adhesion, and steric hindrance determine bacteria repelling performance. Bacteria should be killed by surface chemistry or physical structures when they are attached to a material surface irreversibly. Killing approaches are usually in the light of the cell membrane of bacteria. This review summarizes the fabrication methods and applications of antibacterial surfaces from the view of the treatment of the material surfaces. We also present several crucial points for developing long-term stability, no drug resistance, broad-spectrum, and even programable antibacterial surfaces.

A sulfonate-based polypeptide toward infection-resistant coatings

Multifunctional coatings have gained significant attention for their promising potential to address the issue of medical device-related infections. However, they usually have multiple components in one layer which decreases the density of functional groups on surfaces and hence reduces the biological properties. Herein, we report a mono-component and sulfonate-based anionic polypeptide coating with on-demand antibacterial activity, antifouling property, and biocompatibility. The anionic polypeptide was prepared by ring-opening polymerization of L-cysteine-based N-carboxyanhydride (NCA) with allyl groups and a subsequent thiol-ene reaction to incorporate the sulfonate pendants. It adopted a 17.1-19.5% β-sheet conformation and self-assembled into a spherical nanoparticle. The polypeptide coating showed excellent in vitro antibacterial activity against both Gram-positive (i.e., S. aureus) and Gram-negative bacteria (i.e., E. coli) with >99% killing efficacy after acidic solution treatment and prominent antifouling property and biocompatibility after weak base treatment. An in vivo study revealed that the sulfonate-based polypeptide-coated polydimethylsiloxane (PDMS) exhibited good anti-infection property and histocompatibility.

A Natural Alternative Treatment for Urinary Tract Infections: Itxasol©, the Importance of the Formulation

Genito-urinary tract infections have a high incidence in the general population, being more prevalent among women than men. These diseases are usually treated with antibiotics, but very frequently, they are recurrent and lead to the creation of resistance and are associated with increased morbidity and mortality. For this reason, it is necessary to develop new compounds for their treatment. In this work, our objective is to review the characteristics of the compounds of a new formulation called Itxasol© that is prescribed as an adjuvant for the treatment of UTIs and composed of β-arbutin, umbelliferon and n-acetyl cysteine. This formulation, based on biomimetic principles, makes Itxasol© a broad-spectrum antibiotic with bactericidal, bacteriostatic and antifungal properties that is capable of destroying the biofilm and stopping its formation. It also acts as an anti-inflammatory agent, without the adverse effects associated with the recurrent use of antibiotics that leads to renal nephrotoxicity and other side effects. All these characteristics make Itxasol© an ideal candidate for the treatment of UTIs since it behaves like an antibiotic and with better characteristics than other adjuvants, such as D-mannose and cranberry extracts.

Quaternary tannic acid with improved leachability and biocompatibility for antibacterial medical thermoplastic polyurethane catheters

The surfaces of indwelling catheters offer sites for the adherence of bacteria to form biofilms, leading to various infections. Therefore, the development of antibacterial materials for catheters is imperative. In this study, combining the strong antibacterial effect of a quaternary ammonium salt (QAS) and the high biocompatibility of tannic acid (TA), we prepared a quaternary tannic acid (QTA) by grafting a synthesized quaternary ammonium salt, dimethyl dodecyl 6-bromohexyl ammonium bromide, onto TA. To prepare antibacterial catheters, QTA was blended with thermoplastic polyurethane (TPU) via melt extrusion, which is a convenient and easy-to-control process. Characterization of the TPU blends showed that compared with those of the QAS, dissolution rate and biocompatibility of QTA were significantly improved. On the premise that the introduction of QTA had only a slight effect on the original mechanical properties of pristine TPU, the prepared TPU/QTA maintained satisfactory antibacterial activities in vitro, under a flow state, as well as in vivo. The results verified that the TPU/QTA blend with a QTA content of 4% is effective, durable, stable, and non-toxic, and exhibits significant potential as a raw material for catheters.

Marine Microbial-Derived Antibiotics and Biosurfactants as Potential New Agents against Catheter-Associated Urinary Tract Infections

Catheter-associated urinary tract infections (CAUTIs) are among the leading nosocomial infections in the world and have led to the extensive study of various strategies to prevent infection. However, despite an abundance of anti-infection materials having been studied over the last forty-five years, only a few types have come into clinical use, providing an insignificant reduction in CAUTIs. In recent decades, marine resources have emerged as an unexplored area of opportunity offering huge potential in discovering novel bioactive materials to combat human diseases. Some of these materials, such as antimicrobial compounds and biosurfactants synthesized by marine microorganisms, exhibit potent antimicrobial, antiadhesive and antibiofilm activity against a broad spectrum of uropathogens (including multidrug-resistant pathogens) that could be potentially used in urinary catheters to eradicate CAUTIs. This paper summarizes information on the most relevant materials that have been obtained from marine-derived microorganisms over the last decade and discusses their potential as new agents against CAUTIs, providing a prospective proposal for researchers.

Host-Guest Interaction-Mediated Photo/Temperature Dual-Controlled Antibacterial Surfaces

Development of smart switchable surfaces to solve the inevitable bacteria attachment and colonization has attracted much attention; however, it proves very challenging to achieve on-demand regeneration for noncontaminated surfaces. We herein report a smart, host-guest interaction-mediated photo/temperature dual-controlled antibacterial surface, topologically combining stimuli-responsive polymers with nanobactericide. From the point of view of long-chain polymer design, the peculiar hydration layer generated by hydrophilic poly(2-hydroxyethyl methacrylate) (polyHEMA) segments severs the route of initial bacterial attachment and subsequent proliferation, while the synergistic effect on chain conformation transformation poly(N-isopropylacrylamide) (polyNIPAM) and guest complex dissociation azobenzene/cyclodextrin (Azo/CD) complex greatly promotes the on-demand bacterial release in response to the switch of temperature and UV light. Therefore, the resulting surface exhibits triple successive antimicrobial functions simultaneously: (i) resists ∼84.9% of initial bacterial attachment, (ii) kills ∼93.2% of inevitable bacteria attack, and (iii) releases over 94.9% of killed bacteria even after three cycles. The detailed results not only present a potential and promising strategy to develop renewable antibacterial surfaces with successive antimicrobial functions but also contribute a new antimicrobial platform to biomedical or surgical applications.

Antibiofilm peptides: overcoming biofilm-related treatment failure

Health leaders and scientists worldwide consider antibiotic resistance among the world's most dangerous pathogens as one of the biggest threats to global health. Antibiotic resistance has largely been attributed to genetic changes, but the role and recalcitrance of biofilms, largely due to growth state dependent adaptive resistance, is becoming increasingly appreciated. Biofilms are mono- and multi-species microbial communities embedded in an extracellular, protective matrix. In this growth state, bacteria are transcriptionally primed to survive extracellular stresses. Adaptations, affecting metabolism, regulation, surface charge, immune recognition and clearance, allow bacteria to thrive in the human body and withstand antibiotics and the host immune system. Biofilms resist clearance by multiple antibiotics and have a major role in chronic infections, causing more than 65% of all infections. No specific antibiofilm agents have been developed. Thus, there is a pressing need for alternatives to traditional antibiotics that directly inhibit and/or eradicate biofilms. Host defence peptides (HDPs) are small cationic peptides that are part of the innate immune system to both directly kill microbes but also function to modulate the immune response. Specific HDPs and their derivatives demonstrate broad-spectrum activity against biofilms. In vivo biofilm assays show efficacy in abscess, respiratory, in-dwelling device, contact lens and skin infection models. Further progress has been made through the study of ex vivo organoid and air-liquid interface models to better understand human infections and treatment while relieving the burden and complex nature of animal models. These avenues pave the way for a better understanding and treatment of the underlying cause of chronic infections that challenge the healthcare system.

Bacterial Antifouling Characteristics of Helicene-Graphene Films

Herein, we describe interfacially-assembled [7]helicene films that were deposited on graphene monolayer using the Langmuir-Schaefer deposition by utilizing the interactions of nonplanar (helicene) and planar (graphene) π–π interactions as functional antifouling coatings. Bacterial adhesion of Staphylococcus aureus on helicene—graphene films was noticeably lower than that on bare graphene, up to 96.8% reductions in bacterial adhesion. The promising bacterial antifouling characteristics of helicene films was attributed to the unique molecular geometry of helicene, i.e., nano-helix, which can hinder the nanoscale bacterial docking processes on a surface. We envision that helicene—graphene films may eventually be used as protective coatings against bacterial antifouling on the electronic components of clinical and biomedical devices.

Evaluating medical device and material thrombosis under flow: current and emerging technologies

This review highlights the importance of flow in medical device thrombosis and explores current and emerging technologies to evaluate dynamic biomaterial Thrombosis in vitro.