Efficacy of chlorine-based disinfectants to control Legionella within premise plumbing systems.

Legionella is an opportunistic waterborne pathogen that causes Legionnaires' disease. It poses a significant public health risk, especially to vulnerable populations in health care facilities. It is ubiquitous in manufactured water systems and is transmitted via inhalation or aspiration of aerosols/water droplets generated from water fixtures (e.g., showers and hand basins). As such, the effective management of premise plumbing systems (building water systems) in health care facilities is essential for reducing the risk of Legionnaires' disease. Chemical disinfection is a commonly used control method and chlorine-based disinfectants, including chlorine, chloramine, and chlorine dioxide, have been used for over a century. However, the effectiveness of these disinfectants in premise plumbing systems is affected by various interconnected factors that can make it challenging to maintain effective disinfection. This systematic literature review identifies all studies that have examined the factors impacting the efficacy and decay of chlorine-based disinfectant within premise plumbing systems. A total of 117 field and laboratory-based studies were identified and included in this review. A total of 20 studies directly compared the effectiveness of the different chlorine-based disinfectants. The findings from these studies ranked the typical effectiveness as follows: chloramine > chlorine dioxide > chlorine. A total of 26 factors were identified across 117 studies as influencing the efficacy and decay of disinfectants in premise plumbing systems. These factors were sorted into categories of operational factors that are changed by the operation of water devices and fixtures (such as stagnation, temperature, water velocity), evolving factors which are changed in-directly (such as disinfectant concentration, Legionella disinfectant resistance, Legionella growth, season, biofilm and microbe, protozoa, nitrification, total organic carbon(TOC), pH, dissolved oxygen(DO), hardness, ammonia, and sediment and pipe deposit) and stable factors that are not often changed(such as disinfectant type, pipe material, pipe size, pipe age, water recirculating, softener, corrosion inhibitor, automatic sensor tap, building floor, and construction activity). A factor-effect map of each of these factors and whether they have a positive or negative association with disinfection efficacy against Legionella in premise plumbing systems is presented. It was also found that evaluating the effectiveness of chlorine disinfection as a water risk management strategy is further complicated by varying disinfection resistance of Legionella species and the form of Legionella (culturable/viable but non culturable, free living/biofilm associated, intracellular replication within amoeba hosts). Future research is needed that utilises sensors and other approaches to measure these key factors (such as pH, temperature, stagnation, water age and disinfection residual) in real time throughout premise plumbing systems. This information will support the development of improved models to predict disinfection within premise plumbing systems. The findings from this study will inform the use of chlorine-based disinfection within premise plumbing systems to reduce the risk of Legionnaires disease.

Recent Advances in Superhydrophobic Materials Development for Maritime Applications.

Underwater superhydrophobic surfaces stand as a promising frontier in materials science, holding immense potential for applications in underwater infrastructure, vehicles, pipelines, robots, and sensors. Despite this potential, widespread commercial adoption of these surfaces faces limitations, primarily rooted in challenges related to material durability and the stability of the air plastron during prolonged submersion. Factors such as pressure, flow, and temperature further complicate the operational viability of underwater superhydrophobic technology. This comprehensive review navigates the evolving landscape of underwater superhydrophobic technology, providing a deep dive into the introduction, advancements, and innovations in design, fabrication, and testing techniques. Recent breakthroughs in nanotechnology, magnetic-responsive coatings, additive manufacturing, and machine learning are highlighted, showcasing the diverse avenues of progress. Notable research endeavors concentrate on enhancing the longevity of plastrons, the fundamental element governing superhydrophobic behavior. The review explores the multifaceted applications of superhydrophobic coatings in the underwater environment, encompassing areas such as drag reduction, anti-biofouling, and corrosion resistance. A critical examination of commercial offerings in the superhydrophobic coating landscape offers a current perspective on available solutions. In conclusion, the review provides valuable insights and forward-looking recommendations to propel the field of underwater superhydrophobicity toward new dimensions of innovation and practical utility.

Electrical stimulation to human dermal papilla cells for hair regenerative medicine.

Hair follicle dermal papilla cells (DPCs) are specialized mesenchymal cells that play pivotal roles in hair formation, growth, and cycles, and they are considered as a cell source in hair regenerative medicine. Rodent dermal papilla cells have been shown to induce de novo hair follicle generation in the skin of recipients following transplantation, suggesting that dermal papilla cells can reprogram epidermal microenvironments. However, human DPCs (hDPCs) lose their ability to generate de novo hair follicles under conventional culture methods. We investigated the effects of electrical stimulation (ES) on hDPCs to restore the depressed trichogenic activity. We demonstrated that ES with a polypyrrole (PPy)-modified electrode upregulated trichogenic gene expression in hDPCs in vitro, and the activated cells when transplanted into mice generated double the number of hairs compared to that without the ES. Using specific inhibitors, we revealed that the mechanisms behind the electrical activation are associated with voltage-gated ion channels. Further, ES can be adapted for hDPCs from a patient with androgenic alopecia. Thus, this approach is potentially beneficial in preparing hDPCs for hair regenerative medicine.

Fibrinogen, collagen, and transferrin adsorption to poly(3,4-ethylenedioxythiophene)-xylorhamno-uronic glycan composite conducting polymer biomaterials for wound healing applications.

We present the conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) doped with an algal-derived glycan extract, Phycotrix™ [xylorhamno-uronic glycan (XRU84)], as an innovative electrically conductive material capable of providing beneficial biological and electrical cues for the promotion of favorable wound healing processes. Increased loading of the algal XRU84 into PEDOT resulted in a reduced surface nanoroughness and interfacial surface area and an increased static water contact angle. PEDOT-XRU84 films demonstrated good electrical stability and charge storage capacity and a reduced impedance relative to the control gold electrode. A quartz crystal microbalance with dissipation monitoring study of protein adsorption (transferrin, fibrinogen, and collagen) showed that collagen adsorption increased significantly with increased XRU84 loading, while transferrin adsorption was significantly reduced. The viscoelastic properties of adsorbed protein, characterized using the ΔD/Δf ratio, showed that for transferrin and fibrinogen, a rigid, dehydrated layer was formed at low XRU84 loadings. Cell studies using human dermal fibroblasts demonstrated excellent cell viability, with fluorescent staining of the cell cytoskeleton illustrating all polymers to present excellent cell adhesion and spreading after 24 h.

Redox Polymers for Tissue Engineering.

This review will focus on the targeted design, synthesis and application of redox polymers for use in regenerative medicine and tissue engineering. We define redox polymers to encompass a variety of polymeric materials, from the multifunctional conjugated conducting polymers to graphene and its derivatives, and have been adopted for use in the engineering of several types of stimulus responsive tissues. We will review the fundamental properties of organic conducting polymers (OCPs) and graphene, and how their properties are being tailored to enhance material - biological interfacing. We will highlight the recent development of high-resolution 3D fabrication processes suitable for biomaterials, and how the fabrication of intricate scaffolds at biologically relevant scales is providing exciting opportunities for the application of redox polymers for both in-vitro and in-vivo tissue engineering. We will discuss the application of OCPs in the controlled delivery of bioactive compounds, and the electrical and mechanical stimulation of cells to drive behaviour and processes towards the generation of specific functional tissue. We will highlight the relatively recent advances in the use of graphene and the exploitation of its physicochemical and electrical properties in tissue engineering. Finally, we will look forward at the future of organic conductors in tissue engineering applications, and where the combination of materials development and fabrication processes will next unite to provide future breakthroughs.

Fungal spore adhesion on glycidoxypropyltrimethoxy silane modified silica nanoparticle surfaces as revealed by single cell force spectroscopy.

Thin film coatings prepared from commercially available glycidoxypropyltrimethoxysilane (GPS) modified silica nanoparticles (SiNPs) (Bindzil® CC301 and Bindzil® CC302) have previously shown excellent antifouling performance against a broad range of microbes [Molino et al., "Hydration layer structure of biofouling-resistant nanoparticles," ACS Nano 12, 11610 (2018)]. In this work, single cell force spectroscopy (SCFS) was used to measure the biological interactions between Epicoccum nigrum fungal spores and the same silica nanoparticle-based surfaces used in the aforementioned study, including a: glass coverslip, unmodified SiNP coatings, and both low (Bindzil® CC301) and high density (CC302) GPS functionalized SiNP coatings as a function of NaCl concentration. From the SCFS curves, the spore adhesion to the surface was greatest on the glass coverslip (20-80 nN) followed by the unmodified SiNP (3-5 nN) across all salt concentrations. Upon approach to both surfaces, the spores showed a long-range attraction generally with a profile characteristic of biointeractions and likely those of the outer cell wall structures or biological constituents. The attractive force allowed the spores to initially adhere to the surface and was found to be linearly proportional to the spore adhesion. In comparison, both high and low density GPS-SINP significantly reduced the spore adhesion (0.5-0.9 nN). In addition, the spore adhesion on high density GPS-SiNP occurred in only 14%-27% of SCFS curves (40%-48% for low density GPS-SiNP) compared to 83%-97% for the unmodified SiNP, indicating that in most cases the GPS functionalization completely prevented spore adhesion. The GPS-SiNP surfaces conversely showed a long-range electrostatic repulsion at low 1mM NaCl that was replaced by short-range repulsion at the higher salt concentrations. From the findings, it is proposed that the attractive force is a critical step in initial adhesion processes of the spore. The effective antifouling properties of the GPS are attributed to the ability to negate the attractive forces, either through electrostatic repulsion in low salt conditions and primarily from short-range repulsion correlating to the previously reported combined steric-hydration effect of the GPS functionalization on SiNP coatings.

Synthesis and 3D Printing of Conducting Alginate-Polypyrrole Ionomers.

Hydrogels composed of calcium cross-linked alginate are under investigation as bioinks for tissue engineering scaffolds due to their variable viscoelasticity, biocompatibility, and erodibility. Here, pyrrole was oxidatively polymerized in the presence of sodium alginate solutions to form ionomeric composites of various compositions. The IR spectroscopy shows that mild base is required to prevent the oxidant from attacking the alginate during the polymerization reaction. The resulting composites were isolated as dried thin films or cross-linked hydrogels and aerogels. The products were characterized by elemental analysis to determine polypyrrole incorporation, electrical conductivity measurements, and by SEM to determine changes in morphology or large-scale phase separation. Polypyrrole incorporation of up to twice the alginate (monomer versus monomer) provided materials amenable to 3D extrusion printing. The PC12 neuronal cells adhered and proliferated on the composites, demonstrating their biocompatibility and potential for tissue engineering applications.

Modified silica nanoparticle coatings: Dual antifouling effects of self-assembled quaternary ammonium and zwitterionic silanes.

This work examines the antifouling effect of quaternary ammonium silane (QAS) grafted from coatings of silica nanoparticles (SiNPs), independently and in combination with a zwitterionic sulfobetaine (SB) silane. The binding of QAS to the SiNP coatings was monitored using quartz crystal microgravimetry with dissipation monitoring (QCM-D) under varied pH and solution concentrations. Adsorption of bovine serum albumin protein was reduced on QAS modified SiNP coatings prepared under alkaline conditions due to the proposed generation of a pseudozwitterionic interface, where the underlying SiNP surface presents an anionic charge at high pH. Significant reductions in protein binding were achieved at low functionalization concentrations and short modification times. Additionally, SiNP coatings modified with a combination of QAS and SB chemistries were investigated. Surface modifications were performed sequentially, varying silane concentration and order of addition, and monitored using QCM-D. Dual-functionalized surfaces presented enhanced resistance to protein adsorption compared to QAS or SB modified surfaces alone, even at low functionalization concentrations. The antiadhesive and antibacterial properties of functionalized surfaces were investigated by challenging the surfaces against the bacterium Escherichia coli. All dual-functionalized coatings showed equal or reduced bacterial adhesion compared to QAS and SB functionalizations alone, while coatings functionalized with high concentrations of combined chemistries reduced the adhesion of bacteria by up to 95% compared to control SiNP surfaces.

Carboxybetaine functionalized nanosilicas as protein resistant surface coatings.

Materials with protein resistant properties are increasingly sought after for their potential application as low-fouling surface coatings. Hydrophilic coatings with improved resistance to protein fouling have been prepared from zwitterionic carboxybetaine (CB) functionalized silica nanoparticles (SiNPs). The authors report three methods of coating preparation via direct tethering of CB to predeposited particle films, a two-step surface functionalization process, and deposition of CB functionalized particle dispersions. The pH at which aqueous CB solutions were prepared and reacted to SiNPs was found to drastically influence the mechanism of CB attachment and affect the protein resistance of the resultant coatings. Depending on the method of coating preparation, protein binding to functionalized particle coatings was reduced by up to 94% compared to unfunctionalized SiNP control surfaces. As a result, all three methods offer simple and scalable fabrication routes for the generation of hydrophilic, zwitterionic interfaces with improved inhibition to protein fouling.

Public Health Risks Associated with Heavy Metal and Microbial Contamination of Drinking Water in Australia.

Recently in Australia concerns have been raised regarding the contamination of municipal drinking water supplies with lead. This is of particular concern to children due to the impact of lead exposure on cognitive development and as such these findings have received much media attention. The response from legislators has been swift, and The Victorian School Building Authority has announced that all new schools and school upgrade works will only use lead-free tapware and piping systems. However, while the immediate replacement of lead-containing brass fittings may seem a logical and obvious response, it does not consider the potential implications on microbial contamination. This is particularly concerning given the increasing public health threat posed by opportunistic premise plumbing pathogens (OPPPs). This commentary explores this public health risk of lead exposure from plumbing materials compared to the potential public health risks from OPPPs. Non-tuberculous mycobacterium was chosen as the example OPPP, and the influence on plumbing material and its public health burden in Australia is explored. This commentary highlights the need for future research into the influence of plumbing material on OPPPs prior to any changes in legislation regarding plumbing material.

On Low-Concentration Inks Formulated by Nanocellulose Assisted with Gelatin Methacrylate (GelMA) for 3D Printing toward Wound Healing Application.

Cellulose nanofibrils (CNFs) in the form of hydrogels stand out as a platform biomaterial in bioink formulation for 3D printing because of their low cytotoxicity and structural similarity to extracellular matrices. In the present study, 3D scaffolds were successfully printed with low-concentration inks formulated by 1 w/v % 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized CNF with less than 1 w/v % gelatin methacrylate (GelMA). Quartz crystal microbalance with dissipation monitoring (QCM-D) measurements showed strong interaction between the two biopolymers. The UV cross-linking ability of GelMA (≤1 w/v %) was enhanced in the presence of TEMPO-oxidized CNFs. Multiple factors including strong physical interaction between CNF and GelMA, in situ cross-linking of CNF by Ca2+, and UV cross-linking of GelMA enabled successful 3D printing of low-concentration inks of CNF/GelMA into scaffolds possessing good structural stability. The mechanical strength of the scaffolds was tuned in the range of 2.5 to 5 kPa. The cell culture with 3T3 fibroblasts revealed noncytotoxic and biocompatible features for the formulated inks and printed scaffolds. More importantly, the incorporated GelMA in the CNF hydrogel promoted the proliferation of fibroblasts. The developed low-concentration CNF/GelMA formulations with a facile yet effective approach to fabricate scaffolds showed great potential in 3D printing for wound healing application.

Zwitterion Functionalized Silica Nanoparticle Coatings: The Effect of Particle Size on Protein, Bacteria, and Fungal Spore Adhesion.

The negative impacts that arise from biological fouling of surfaces have driven the development of coatings with unique physical and chemical properties that are able to prevent interactions with fouling species. Here, we report on low-fouling hydrophilic coatings presenting nanoscaled features prepared from different size silica nanoparticles (SiNPs) functionalized with zwitterionic chemistries. Zwitterionic sulfobetaine siloxane (SB) was reacted to SiNPs ranging in size from 7 to 75 nm. Particle stability and grafting density were confirmed using dynamic light scattering and thermogravimetric analysis. Thin coatings of nanoparticles were prepared by spin-coating aqueous particle suspensions. The resulting coatings were characterized using scanning electron microscopy, atomic force microscopy, and contact angle goniometry. SB functionalized particle coatings displayed increased hydrophilicity compared to unmodified particle coating controls while increasing particle size correlated with increased coating roughness and increased surface area. Coatings of zwitterated particles demonstrated a high degree of nonspecific protein resistance, as measured by quartz crystal microgravimetry. Adsorption of bovine serum albumin and hydrophobin proteins were reduced by up to 91 and 94%, respectively. Adhesion of bacteria ( Escherichia coli) to zwitterion modified particle coatings were also significantly reduced over both short and long-term assays. Maximum reductions of 97% and 94% were achieved over 2 and 24 h assay periods, respectively. For unmodified particle coatings, protein adsorption and bacterial adhesion were generally reduced with increasing particle size. Adhesion of fungal spores to SB modified SiNP coatings was also reduced, however no clear trends in relation to particle size were demonstrated.

Hydration Layer Structure of Biofouling-Resistant Nanoparticles.

Hydrophilic surface chemistries can strongly bind water to produce surfaces that are highly resistant to protein adsorption and fouling. The interfacial bound water and its distinct properties have intrigued researchers for decades, yet the relationship between the water three-dimensional structure and function in antifouling coatings remains elusive. Here, we use hydrophilic, epoxy organosilane modified silica nanoparticles to demonstrate cheap, robust, and practically applied coatings that we discover have broad-ranging, ultralow fouling properties when challenged by various proteins, bacteria, and fungal spores. To understand their excellent antifouling properties, frequency modulation-atomic force microscopy is used to directly observe the interfacial water structure at subatomic resolution, which we validate using all-atom molecular dynamic simulations that strikingly predict similar structures of water layers on the original and ultralow fouling surfaces. The convergence of experimental and modeling data reveals that suitably spaced, flexible chains with hydrophilic groups interact with water molecules to produce a connective, quasi-stable layer, consisting of dynamic interfacial water, that provides a basis for antifouling performance of ultrathin, hydrophilic surface chemistries.

Silica Nanoparticles Functionalized with Zwitterionic Sulfobetaine Siloxane for Application as a Versatile Antifouling Coating System.

The growing need to develop surfaces able to effectively resist biological fouling has resulted in the widespread investigation of nanomaterials with potential antifouling properties. However, the preparation of effective antifouling coatings is limited by the availability of reactive surface functional groups and our ability to carefully control and organize chemistries at a materials' interface. Here, we present two methods of preparing hydrophilic low-fouling surface coatings through reaction of silica-nanoparticle suspensions and predeposited silica-nanoparticle films with zwitterionic sulfobetaine (SB). Silica-nanoparticle suspensions were functionalized with SB across three pH conditions and deposited as thin films via a simple spin-coating process to generate hydrophilic antifouling coatings. In addition, coatings of predeposited silica nanoparticles were surface functionalized via exposure to zwitterionic solutions. Quartz crystal microgravimetry with dissipation monitoring was employed as a high throughput technique for monitoring and optimizing reaction to the silica-nanoparticle surfaces. Functionalization of nanoparticle films was rapid and could be achieved over a wide pH range and at low zwitterion concentrations. All functionalized particle surfaces presented a high degree of wettability and resulted in large reductions in adsorption of bovine serum albumin protein. Particle coatings also showed a reduction in adhesion of fungal spores (Epicoccum nigrum) and bacteria (Escherichia coli) by up to 87 and 96%, respectively. These results indicate the potential for functionalized nanosilicas to be further developed as versatile fouling-resistant coatings for widespread coating applications.

Atomically Thin Hexagonal Boron Nitride Nanofilm for Cu Protection: The Importance of Film Perfection.

Outstanding protection of Cu by high-quality boron nitride nanofilm (BNNF) 1-2 atomic layers thick in salt water is observed, while defective BNNF accelerates the reaction of Cu toward water. The chemical stability, insulating nature, and impermeability of ions through the BN hexagons render BNNF a great choice for atomic-scale protection.

Quantifying Molecular-Level Cell Adhesion on Electroactive Conducting Polymers using Electrochemical-Single Cell Force Spectroscopy.

Single Cell Force Spectroscopy was combined with Electrochemical-AFM to quantify the adhesion between live single cells and conducting polymers whilst simultaneously applying a voltage to electrically switch the polymer from oxidized to reduced states. The cell-conducting polymer adhesion represents the non-specific interaction between cell surface glycocalyx molecules and polymer groups such as sulfonate and dodecylbenzene groups, which rearrange their orientation during electrical switching. Single cell adhesion significantly increases as the polymer is switched from an oxidized to fully reduced state, indicating stronger cell binding to sulfonate groups as opposed to hydrophobic groups. This increase in single cell adhesion is concomitant with an increase in surface hydrophilicity and uptake of cell media, driven by cation movement, into the polymer film during electrochemical reduction. Binding forces between the glycocalyx and polymer surface are indicative of molecular-level interactions and during electrical stimulation there is a decrease in both the binding force and stiffness of the adhesive bonds. The study provides insight into the effects of electrochemical switching on cell adhesion at the cell-conducting polymer interface and is more broadly applicable to elucidating the binding of cell adhesion molecules in the presence of electrical fields and directly at electrode interfaces.

Functionalised inherently conducting polymers as low biofouling materials.

Diatoms are a major component of microbial biofouling layers that develop on man-made surfaces placed in aquatic environments, resulting in significant economic and environmental impacts. This paper describes surface functionalisation of the inherently conducting polymers (ICPs) polypyrrole (PPy) and polyaniline (PANI) with poly(ethylene glycol) (PEG) and their efficacy as fouling resistant materials. Their ability to resist interactions with the model protein bovine serum albumin (BSA) was tested using a quartz crystal microbalance with dissipation monitoring (QCM-D). The capacity of the ICP-PEG materials to prevent settlement and colonisation of the fouling diatom Amphora coffeaeformis (Cleve) was also assayed. Variations were demonstrated in the dopants used during ICP polymerisation, along with the PEG molecular weight, and the ICP-PEG reaction conditions, all playing a role in guiding the eventual fouling resistant properties of the materials. Optimised ICP-PEG materials resulted in a significant reduction in BSA adsorption, and > 98% reduction in diatom adhesion.

Correlation of the impedance and effective electrode area of doped PEDOT modified electrodes for brain-machine interfaces.

Electrode impedance is used to assess the thermal noise and signal-to-noise ratio for brain-machine interfaces. An intermediate frequency of 1 kHz is typically measured, although other frequencies may be better predictors of device performance. PEDOT-PSS, PEDOT-DBSA and PEDOT-pTs conducting polymer modified electrodes have reduced impedance at 1 kHz compared to bare metal electrodes, but have no correlation with the effective electrode area. Analytical solutions to impedance indicate that all low-intermediate frequencies can be used to compare the electrode area at a series RC circuit, typical of an ideal metal electrode in a conductive solution. More complex equivalent circuits can be used for the modified electrodes, with a simplified Randles circuit applied to PEDOT-PSS and PEDOT-pTs and a Randles circuit including a Warburg impedance element for PEDOT-DBSA at 0 V. The impedance and phase angle at low frequencies using both equivalent circuit models is dependent on the electrode area. Low frequencies may therefore provide better predictions of the thermal noise and signal-to-noise ratio at modified electrodes. The coefficient of variation of the PEDOT-pTs impedance at low frequencies was lower than the other conducting polymers, consistent with linear and steady-state electroactive area measurements. There are poor correlations between the impedance and the charge density as they are not ideal metal electrodes.