Anti-biofouling and antibacterial surfaces via a multicomponent coating deposited from an up-scalable atmospheric-pressure plasma-assisted CVD process

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

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

Combination of Enzymes with Materials to Give Them Antimicrobial Features: Modern Trends and Perspectives

Multidrug-resistant bacteria form serious problems in many areas, including medicine and the food industry. At the same time, great interest is shown in the transfer or enhancement of antimicrobial properties to various materials by modifying them with enzymes. The use of enzymes in biomaterials with antimicrobial properties is important because enzymes can be used as the main active components providing antimicrobial properties of functionalized composite biomaterials, or can serve as enhancers of the antimicrobial action of certain substances (antibiotics, antimicrobial peptides, metal nanoparticles, etc.) against cells of various microorganisms. Enzymes can simultaneously widen the spectrum of antimicrobial activity of biomaterials. This review presents the most promising enzymes recently used for the production of antibacterial materials, namely hydrolases and oxidoreductases. Computer modeling plays an important role in finding the most effective combinations between enzymes and antimicrobial compounds, revealing their possible interactions. The range of materials that can be functionalized using enzymes looks diverse. The physicochemical characteristics and functionalization methods of the materials have a significant impact on the activity of enzymes. In this context, fibrous materials are of particular interest. The purpose of this review is to analyze the current state of the art in this area.

Substrate-independent and widely applicable deposition of antibacterial coatings

Antibacterial coatings are regarded as a necessary tool to prevent implant-related infections. Substrate-independent and widely applicable coating techniques are gaining significant interest to synthesize different types of antibacterial films, which can be relevant from a fundamental and application-oriented perspective. Plasma polymer- and polydopamine-based antibacterial coatings represent the most widely studied and versatile approaches among these coating techniques. Both single- and dual-functional antibacterial coatings can be fabricated with these approaches and a variety of dual-functional antibacterial coating strategies can still be explored in future work. These coatings can potentially be used for a wide range of different implants (material, shape, and size). However, for most implants, significantly more fundamental knowledge needs to be gained before these coatings can find real-life use.

Fluid-driven bacterial accumulation in proximity of laser-textured surfaces

In this work we investigated the role of fluid in the initial phase of bacterial adhesion on textured surfaces, focusing onto the approach of the bacterial cells towards the surface. In particular, stainless steel surfaces textured via femtosecond laser interaction have been considered. The method combined a simulation routine, based on the numerical solution of Navier-Stokes equations, and the use of a theoretical model, based on the Smoluchowski's equation. Results highlighted a slowdown of the fluid velocity field in correspondence of the surface dales. In addition, a shear induced accumulation on the top of the surface protrusions was predicted for motile bacterial species, E. coli. In particular, we observed a role of the surface protrusions in increasing the range over which motile bacterial species are attracted towards the surface through a rheotactic mechanism. In other words, we found that, in certain conditions of fluid flow and textured surface morphology, surface protrusions act as a sort of "rheotactic antennas".

State of the art in nonthermal plasma processing for biomedical applications: Can it help fight viral pandemics like COVID-19?

Plasma processing finds widespread biomedical applications, such as the design of biosensors, antibiofouling surfaces, controlled drug delivery systems, and in plasma sterilizers. In the present coronavirus disease (COVID-19) situation, the prospect of applying plasma processes like surface activation, plasma grafting, plasma-enhanced chemical vapor deposition/plasma polymerization, surface etching, plasma immersion ion implantation, crosslinking, and plasma decontamination to provide timely solutions in the form of better antiviral alternatives, practical diagnostic tools, and reusable personal protective equipment is worth exploring. Herein, the role of nonthermal plasmas and their contributions toward healthcare are timely reviewed to engage different communities in assisting healthcare associates and clinicians, not only to combat the current COVID-19 pandemic but also to prevent similar kinds of future outbreaks.

Future antiviral polymers by plasma processing

Coronavirus disease 2019 (COVID-19) is largely threatening global public health, social stability, and economy. Efforts of the scientific community are turning to this global crisis and should present future preventative measures. With recent trends in polymer science that use plasma to activate and enhance the functionalities of polymer surfaces by surface etching, surface grafting, coating and activation combined with recent advances in understanding polymer-virus interactions at the nanoscale, it is promising to employ advanced plasma processing for smart antiviral applications. This trend article highlights the innovative and emerging directions and approaches in plasma-based surface engineering to create antiviral polymers. After introducing the unique features of plasma processing of polymers, novel plasma strategies that can be applied to engineer polymers with antiviral properties are presented and critically evaluated. The challenges and future perspectives of exploiting the unique plasma-specific effects to engineer smart polymers with virus-capture, virus-detection, virus-repelling, and/or virus-inactivation functionalities for biomedical applications are analysed and discussed.

Preparation and Antifouling Property of Polyurethane Film Modified by PHMG and HA Using Layer-by-Layer Assembly

To reduce the possibility of bacterial infection and implant-related complications, surface modification on polyurethane (PU) film is an ideal solution to endow hydrophobic PU with antibacterial and antifouling properties. In this work, a variety of polyhexamethylene guanidine/ hyaluronic acid (PHMG/HA) multilayer films were self-assembled layer-by-layer on PU films using polyanions, carboxyl-activated HA, and polycations PHMG by controlling the concentration of these polyelectrolytes as well as the number of layers self-assembled. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) spectra, water contact angle (WCA), and A Atomic force microscope (AFM) of PU and modified PU films were studied. Protein adsorption and bacterial adhesion as well as the cytotoxicity against L929 of the film on selected PU-(PHMG/HA)₅/5-5 were estimated. The results showed that PU-(PHMG/HA)₅/5-5 had the best hydrophilicity among all the prepared films, possessing the lowest level of protein adsorption. Meanwhile, this film showed efficient broad-spectrum antibacterial performance as well as significant resistance of bacterial adhesion of more than a 99.9% drop for the selected bacteria. Moreover, almost no influence on cell viability of L929 enhanced the biocompatibility of film. Therefore, the modified PU films with admirable protein absorption resistance, antimicrobial performance, and biocompatibility would have promising applications in biomedical aspect.

Anti-Biofouling Features of Eco-Friendly Oleamide-PDMS Copolymers

The biofouling of marine organisms on a surface induces serious economic damage. One of the conventional anti-biofouling strategies is the use of toxic chemicals. In this study, a new eco-friendly oleamide-PDMS copolymer (OPC) is proposed for sustainable anti-biofouling and effective drag reduction. The anti-biofouling characteristics of the OPC are investigated using algal spores and mussels. The proposed OPC is found to inhibit the adhesion of algal spores and mussels. The slippery features of the fabricated OPC surfaces are examined by direct measurement of pressure drops in channel flows. The proposed OPC surface would be utilized in various industrial applications including marine vehicles and biomedical devices.

Recent Advancements in the Use of Aerosol-Assisted Atmospheric Pressure Plasma Deposition

Atmospheric pressure plasma allows for the easy modification of materials’ surfaces for a wide range of technological applications. Coupling the aerosol injection of precursors with atmospheric pressure plasma largely extends the versatility of this kind of process; in fact solid and, in general, scarcely volatile precursors can be delivered to the plasma, extending the variety of chemical pathways to surface modification. This review provides an overview of the state of the art of aerosol-assisted atmospheric pressure plasma deposition. Advantages (many), and drawbacks (few) will be illustrated, as well as hints as to the correct coupling of the atomization source with the plasma to obtain specific coatings. In particular, the deposition of different organic, hybrid inorganic–organic and bioactive nanocomposite coatings will be discussed. Finally, it will be shown that, in particular cases, unique core–shell nanocapsules can be obtained.

Various methods to combine hyaluronic acid and antimicrobial peptides coatings and evaluation of their antibacterial behaviour

To prevent bacterial adhesion and contamination, biomaterials exhibiting both antiadhesive and biocidal properties are the most promising way. However, control of the properties combination is not so easy due, in particular, to antagonist mechanisms. Antibacterial surfaces against Staphylococcus epidermidis adhesion were here elaborated by using both nisin grafting and repelling polysaccharide coating. We evaluated two strategies aiming to improve the antimicrobial peptide (AMP) immobilization parameters (i.e., the accessibility and/or local density) in order to obtain the best antimicrobial activity on surfaces. We thus (i) grafted the nisin on a surface previously coated with hydrolyzed hyaluronic acid (HA) (to decrease the length of the polysaccharide chains) or (ii) coupled nisin and HA in solution before grafting this complex on surfaces. XPS analysis pointed out a lower amount of nisin on the surface for both approaches compared to the immobilization of nisin on native HA. However, an antibacterial activity was maintained, probably due to a higher local density of the AMP when surfaces were modified with hydrolyzed hyaluronic acid, leading to a better combination of antiadhesive-biocidal properties. Microscopy fluorescent observations demonstrated that accumulation of dead cells was also avoided by some coatings architecture.

Facile In Situ Preparation and In Vitro Antibacterial Activity of PDMAEMA-Based Silver-Bearing Copolymer Micelles

Well-defined polymer micelles with core-shell structure are good delivery platform for stabilizing silver nanoparticles (AgNPs) in the field of antimicrobials targeting diseases. The rational construction of the polymer structure, an efficient, facile, and green preparation approach, and comprehensive exploration of the derived AgNPs are necessary, such as size, particle stability, antibacterial activity, and other properties. Herein, we designed and assessed the in vitro antimicrobial activity of AgNPs-decorated copolymer micelles with different copolymer topologies. First, linear or four-arm star triblock copolymers with the similar molecular weight and degree of polymerization were obtained, which consisted of DMAEMA for in situ reduction of silver ions to form AgNPs without external reducing agent. HEMA and PEGMA in micellar shell gave an enhanced stability of AgNPs during blood circulation. The combination of computational modeling and experimental results indicated that both types of micelles could fabricate AgNPs with monodisperse and spherical morphology. Star copolymer micelles stabilized AgNPs had smaller average size, better stability, and higher antibacterial activity than those with linear structure, which may due to higher stability of micelles from star copolymers. Furthermore, the cytotoxicity evaluation test showed that the achieved linear or star copolymers micelles stabilized AgNPs had good biocompatibility. This work provides a facile and universal approach in the rational design of micelles stabilized AgNPs with suitable topology for fighting against a wide range of bacterial infections.

Switchable Dual-Function and Bioresponsive Materials to Control Bacterial Infections

The colonization of undesired bacteria on the surface of devices used in biomedical and clinical applications has become a persistent problem. Different types of single-function (cell resistance or bactericidal) bioresponsive materials have been developed to cope with this problem. Even though these materials meet the basic requirements of many biomedical and clinical applications, dual-function (cell resistance and biocidal) bioresponsive materials with superior design and function could be better suited for these applications. The past few years have witnessed the emergence of a new class of dual-function materials that can reversibly switch between cell-resistance and biocidal functions in response to external stimuli. These materials are finding increased applications in biomedical devices, tissue engineering, and drug-delivery systems. This review highlights the recent advances in design, structure, and fabrication of dual-function bioresponsive materials and discusses translational challenges and future prospects for research involving these materials.

Atmospheric Aerosol Assisted Pulsed Plasma Polymerization: An Environmentally Friendly Technique for Tunable Catechol-Bearing Thin Films

In this work, an atmospheric aerosol assisted pulsed plasma process is reported as an environmentally friendly technique for the preparation of tunable catechol-bearing thin films under solvent and catalyst free conditions. The approach relies on the direct injection of dopamine acrylamide dissolved in 2-hydroxyethylmethacrylate as comonomer into the plasma zone. By adjusting the pulsing of the electrical discharge, the reactive plasma process can be alternatively switch ON (tON) and OFF (tOFF) during different periods of time, thus allowing a facile and fine tuning of the catechol density, morphology and deposition rate of the coating. An optimal tON/tOFF ratio is established, that permits maximizing the catechol content in the deposited film. Finally, a diagram, based on the average energy input into the process, is proposed allowing for easy custom synthesis of layers with specific chemical and physical properties, thus highlighting the utility of the developed dry plasma route.

Mussel-Inspired Surface Functionalization of PET with Zwitterions and Silver Nanoparticles for the Dual-Enhanced Antifouling and Antibacterial Properties

Herein, we designed and constructed a dual functional surface with antimicrobial and antifouling abilities to prevent protein and bacterial attachment that are significant challenges in biomedical devices. Primary amino-group-capped sulfobetaine of DMMSA was synthesized and then grafted onto polydopamine pretreated PET sheets via click chemistry. The sheets were subsequently immersed into silver ion solution, in which the absorbed silver ions were reduced to silver nanoparticles (AgNPs) in situ by a polydopamine layer. The antifouling assays demonstrated that the resultant PET/DMMSA/AgNPs sheets exhibited great antifouling performances against bovine serum albumin (BSA), bovine fibrinogen (BFG), platelets, and bacteria, the critical proteins/microorganisms leading to implant failure. The antibacterial data suggested that the sheets had dual functions as inhibitors of bacterial growth and bactericide and could efficiently delay the biofilm formation. This repelling and killing approach is green and simple, with potential biomedical applications.

Self-Cleaning: From Bio-Inspired Surface Modification to MEMS/Microfluidics System Integration

This review focuses on self-cleaning surfaces, from passive bio-inspired surface modification including superhydrophobic, superomniphobic, and superhydrophilic surfaces, to active micro-electro-mechanical systems (MEMS) and digital microfluidic systems. We describe models and designs for nature-inspired self-cleaning schemes as well as novel engineering approaches, and we discuss examples of how MEMS/microfluidic systems integrate with functional surfaces to dislodge dust or undesired liquid residues. Meanwhile, we also examine "waterless" surface cleaning systems including electrodynamic screens and gecko seta-inspired tapes. The paper summarizes the state of the art in self-cleaning surfaces, introduces available cleaning mechanisms, describes established fabrication processes and provides practical application examples.

Smart Fluorescent Hydrogel Glucose Biosensing Microdroplets with Dual-Mode Fluorescence Quenching and Size Reduction

Fluorescent hydrogel glucose biosensor (FHGB) microdroplets were fabricated using a microfluidic method with glass capillaries having a coaxial flow-focusing geometry with cross-linked poly(acrylic acid) (PAAc) immobilized with carbon dots (CDs), glucose oxidase (GOx), and horseradish peroxidase (HRP) after the conversion of poly(acrylamide) to PAAc. The prepared FHGB droplets showed a dual response to glucose of CD fluorescence quenching and droplet size reduction upon bienzymatic reaction with glucose; the reaction of GOx and HRP with glucose produced gluconic acid and -OH radicals, which caused CD fluorescence quenching and size reduction, respectively. These small FHGB droplets showed good sensitivity (linear range of ∼30 mM with the limit of detection of 0.052 mM), high selectivity (against the main ingredients of human blood serum), and long stability (due to dry state during storage). These FHGB droplets were tested with human blood serum, and they maintained sensing performance for a long time in the dry state. Thus, the FHGB droplets demonstrate a new method to detect glucose levels with small sample amounts by the dual-mode response. They can be further applied as implanted continuous-detection biosensor droplets because of their biocompatibility.

Atmospheric Plasma Deposition of Methacrylate Layers Containing Catechol/Quinone Groups: An Alternative to Polydopamine Bioconjugation for Biomedical Applications

Bioconjugation of enzymes on coatings based on polydopamine (PDA) layers is an appealing approach to control biological responses on biomedical implant surfaces. As alternative to PDA wet deposition, a fast, solvent-free, and dynamic deposition approach based on atmospheric-pressure plasma dielectric barrier discharge process is considered to deposit on metallic surfaces acrylic-based interlayers containing highly chemically reactive catechol/quinone groups. A biomimetic approach based on covalent immobilization of Dispersin B, an enzyme with antibiofilm properties, shows the bioconjugation potential of the novel plasma polymer layers. The excellent antibiofilm activity against Staphylococcus epidermidis is comparable to the PDA-based layers prepared by wet chemical methods with slow deposition rates. A study of preosteoblastic MG-63 human cell line viability and adhesion properties on plasma polymer layers demonstrates early interaction required for biomedical applications.