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We prepared a new environment-friendly dual-function anti-fouling coating with simultaneous self-renewal and sterilization. The (Fe/TOB-PR) 20 coating displayed excellent antimicrobial properties and resistance to microbial adhesion which was attributed to the renewal of the surface and the generation of antibacterial substance (TOB) in the coating. [Display omitted] • Self-assembled Schiff-Base metal complex coatings were built from completely natural products. • The coating degradation was uniform and controlled and would not led to the accumulation of microplastics. • (Fe/TOB-PR) 20 coating exhibited excellent antimicrobial properties and resistance to microbial adhesion. • The coating could be assembled on various substrates. Marine biological fouling has caused huge economic losses and environmental problems. Therefore, it was essential to develop effectively environment-friendly biofouling resistance technology. Here, inspired by the natural module of bacterial secretions, animal and plant extracts, we synthesized Schiff based compounds through Tobramycin (TOB) from Streptomyces and Protocatechualdehyde (PR) from black fern. Furthermore, a dynamic self-renewal Schiff based metal composite coating- (Fe/TOB-PR) n was prepared via layer by layer self-assembly (LBL) method. It was proved to be a versatile coating, which could adhere to different types of substrates. Hydrolytic degradation tests showed that the degradation of the (Fe/TOB-PR) 20 coating was regular and controlled. Moreover, compared with the blank glass substrate, the antibacterial rate of (Fe/TOB-PR) 20 reached 97 % after 24 h, and the test further shows that the durability of the antibacterial performance benefits from the greater coating thickness. Such coatings displayed excellent anti-bacteria and anti-algae adhesion properties which was attributed to the renewal of the surface and the generation of antibacterial substance (TOB) in the coating. Further, the coating eventually degraded to natural micromolecule monomer, avoiding the occurrence of microplastics. It provides research ideas for fabricating environment-friendly anti-biofouling coatings. [ABSTRACT FROM AUTHOR]

[Display omitted] Marine optical instruments are commonly suffering serious biofouling problem caused by the adhesion of marine microorganisms, which severely affects the instruments to monitor the marine environment. Herein, we developed a robust solid slippery surface (SSS) by fabricated a covalently attached polydimethylsiloxane (PDMS) layer on glass substrate to solve the biofouling problem of marine optical instrument windows. The SSS could effectively inhibit the settlements of marine microorganism (bacteria and alga) in various environmental conditions, resulting from the high flexibility of PDMS molecular chains, and thus could maintain its high underwater-transparency. The antifouling mechanism of SSS was results from the weak nonspecific electrostatic Lifshitz-van der Waals forces and less specific hydrogen bonds between SSS and microorganism, which was been confirmed via both single bacterial force spectroscopy measurement and molecular dynamics simulation. Compared with the traditional slippery lubricant-infused porous surface (SLIPS), the SSS exhibited a better robust mechanical stability than that of the SLIPS. In addition, our study provides a valuable method to fabricated the SSS with reliable underwater-transmittance and antifouling properties, which is promised for the applications for the antifouling of marine optical instruments. [ABSTRACT FROM AUTHOR]

[Display omitted] Hydrophobic micro-porous membrane such as polyvinylidene fluoride (PVDF) with excellent thermal-/chemical-stability and low surface energy has received extensive attention in industrial water treatment and sustainable energy conversion. However, undesirable contaminants caused by inevitable proteins or microorganisms adhesion may lead to a rapid loss of separation efficiency, which significantly deteriorate their porous structures and eventually limit their practical performance. Herein, we present a scalable approach for fabricating comb-like copolymer modified PVDF membranes (PVDF-PN@AgNPs) that prevent bacteria from proliferating on the surface and temperature-controlled release of adhered contaminants. Comb-like structured copolymers were imparted to a polydopamine (PDA)-treated PVDF membrane by Michael addition reaction, which enabled a covalent binding of comb-like structured copolymers to the membrane. Such unique structural design of grafted copolymer, containing hydrophilic side chain and temperature-responsive chain backbone, stably prevents bacteria adhesion and provides reversible surface wettability. Therefore, the resultant membranes were evaluated to prevent bacterial adhesion, high touch-killing efficiency and temperature-controlled contaminants release (~99% of protein and ~75% of bacteria). Moreover, with the collapse and stretch of grafted copolymer chain backbone, the synthetic membrane further reversibly adjusted inner micro-porous structure and surface wettability, which eventually helped to achieve variable water fluid transport efficiency. This study not only provides a feasible structural design for stably coping with the challenging of antifouling and subsequent contamination adhesion of PVDF membrane, but also potentially answers the significant gap between lab research advances and practical application, particularly in the industrial membrane field. [ABSTRACT FROM AUTHOR]

Understanding microbial adhesion and retention is crucial for controlling many processes, including biofilm formation, antimicrobial therapy as well as cell sorting and cell detection platforms. Cell detachment is inextricably linked to cell adhesion and retention and plays an important part in the mechanisms involved in these processes. Physico-chemical and biological forces play a crucial role in microbial adhesion interactions and altering the medium ionic strength offers a potential means for modulating these interactions. Real-time studies on the effect of ionic strength on microbial adhesion are often limited to short-term bacterial adhesion. Therefore, there is a need, not only for long-term bacterial adhesion studies, but also for similar studies focusing on eukaryotic microbes, such as yeast. Hereby, we monitored, in real-time, S. cerevisiae adhesion on gold and silica as examples of surfaces with different surface charge properties to disclose long-term adhesion, retention and detachment as a function of ionic strength using quartz crystal microbalance with dissipation monitoring. Our results show that short- and long-term cell adhesion levels in terms of mass-loading increase with increasing ionic strength, while cells dispersed in a medium of higher ionic strength experience longer retention and detachment times. The positive correlation between the cell zeta potential and ionic strength suggests that zeta potential plays a role on cell retention and detachment. These trends are similar for measurements on silica and gold, with shorter retention and detachment times for silica due to strong short-range repulsions originating from a high electron-donicity. Furthermore, the results are comparable with measurements in standard yeast culture medium, implying that the overall effect of ionic strength applies for cells in nutrient-rich and nutrient-deficient media. [ABSTRACT FROM AUTHOR]

Survival and pathogenic microbial adhesions on surfaces of materials followed by the formation of biofilms with robust resistance to antibiotics constitute the forefront of disease transmissions. Conventional strategies responding to this challenge are rather limited due to the biofouling effect of microorganisms or the irreversible consumption of antimicrobial agents embedded into the materials. Herein, we report an approach of combining photo-induced rechargeable biocidal properties with microbial resisting and releasing zwitterionic hydrophilic functions on surfaces of materials to improve antifouling performances. Poly(vinyl alcohol- co -ethylene) (EVOH) nanofibrous membranes (NFMs) were chemically incorporated with both 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BPTCD), a photoactive chemical, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), a zwitterionic monomer. Both functional agents work independently and construct concerted microbial resisting, killing, and releasing functions to reduce microbial contamination and biofilm formation. The resulted SBMA@EVOH NFMs exhibited integrated features of large ROS production capacity, ease of photoactive rechargeability and controllability, long-term stability, high biocidal efficacy (>99.9999% via contact killing), and promising antifouling performance, which enable the SBMA@EVOH NFMs to serve as a biocidal material for food safety and medical applications. [ABSTRACT FROM AUTHOR]

Graphical abstract AgNPs and PDA co-functionalized orange peel derived MACs (MACs@PDA-Ag) were synthesized for recovery uranium from simulation seawater with antifouling. Abstract Undesirable bio-adhesion of microalgae on adsorbent can influence its adsorption capacity. In this report, we fabricated a novel mussel-inspired antifouling magnetic activated carbons which derived orange peel by integrated biosorption-pyrolysis process (MACs@PDA-Ag), via co-functionalization of poly-dopamine (PDA) and Ag nanoparticles (AgNPs), for the recovery of uranium (VI) from simulated seawater with antimicrobial adhesion performance; this process did not require an additional reducing agent. The effect of pH, concentration, contact time, fouling test against nitzschia closterium f.minutissima (GY-H8) were studied. Compared with MACs (632.91 mg/g at pH 7.0), the calculated maximum adsorption capacity of MACs@PDA-Ag increased to 657.89 mg/g at pH 8.0 and showed good recyclability. These data all fitted well with the Langmuir and pseudo-second order models. The possible removal mechanism by XPS is chelation (catechol hydroxyls, amine/imine units, the metal-oxygen and carboxylic) with uranium (VI). The antifouling tests indicated that the AgNPs-modified materials displayed the antimicrobial adhesion behavior, and the viability of the microorganism was not impacted. Thereby, the direct deposition of AgNPs onto the adsorbent has shown great potential for uranium (VI) recovery with an antifouling benefit and is environmentally friendly. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Increased reliance on kill based approaches for disinfection raises concerns of antimicrobial resistance development and has significantly elevated the need for alternate approaches for skin and substrate disinfection. This study focuses on reducing harmful microbes from substrates primarily via removal and to a lesser extent by kill. Hypothesis Functional micro-particles designed to adhere to microbes, with a force greater than the force of microbial adhesion to the substrate, would result in enhanced removal-based disinfection of substrates when subject to an external force. Experiments Silica particles were functionalized with a cationic polymer to bind strongly with bacteria via Coulombic interactions. Disinfection efficacies of substrates with functional particles and control groups were evaluated under conditions relevant for handwashing. Findings Functionalized silica micro-particles result in ∼4 log reduction of E. coli from an artificial skin substrate in 30 s as compared to a maximum of 1.5 log reduction with control particles. Bacterial viability assays indicate a mechanism of action driven by enhanced removal of bacteria with minimal kill. Particle number density, size and suspension velocity along with strong particle – bacteria interactions have been found to be the primary factors responsible for the enhanced bacterial removal from surfaces. [ABSTRACT FROM AUTHOR]

Hypothesis It was predicted that the colloidal behaviors of archaea and bacteria with disparate surface structure were different. In this study, the effects of the physicochemical properties of microbial cell surfaces on colloidal behavior were analyzed with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, thermodynamics, and powder technology. Experiments Cell attachment and detachment from model substrates were directly observed using a parallel plate flow chamber. Gram-negative Escherichia coli and archaeal Methanosarcina barkeri were used as model microbial cells, and positively and negatively charged glass slides were used as model substrates. Findings Microbial adhesion on both substrates agreed well with predictions calculated from DLVO theory, using experimental parameters. The total number of cells detached from the substrates as a function of flow rate was fit with the Weibull distribution function. In addition, the drag force required for detachment, which was estimated from the hydrodynamic forces, had a wide distribution; however, the forces became smaller with increasing ionic strength because of reduced electrostatic interactions between the cells and the substrate. M. barkeri could not be detached from positively charged substrates because it would entail a negative change in the interfacial energy of interaction. Thus adhesion was thermodynamically favored in this case. [ABSTRACT FROM AUTHOR]

Abstract: It is commonly assumed that bacterial presence on a QCM sensor-surface is associated with a negative frequency shift according to conventional mass-loading theory. Here, we demonstrate that bacteria adhering to QCM sensor-surface may yield positive frequency shifts up to 1.9×10−6 Hz per bacterium according to a coupled-oscillator theory. Furthermore, it is demonstrated that the excretion of extracellular polymeric substances (EPS) by adhering bacteria can change the frequency shift in the negative direction by 1.7×10−6 Hz per bacterium, according to conventional mass-loading theory. The difference in frequency shifts between an EPS-producing and a non-EPS producing staphylococcal strain correlated with the excretion of 3×10−14 g EPS per bacterium, representing only a few percent of the weight of a bacterium. Thus an adsorbed molecular mass as low as a few percent of the mass of an adhering bacterium significantly alters the QCM-signal. Since adhesion of many different bacterial strains is accompanied by molecular adsorption of EPS, with potentially opposite effects on the QCM-signal, a combination of the coupled-oscillator and normal mass-loading theory has to be applied for proper interpretation of QCM-frequency shifts in bacterial detection. [Copyright &y& Elsevier]

Abstract: The microbial adhesion to hydrocarbons (MATH) assay has been used widely to characterize microbial cell hydrophobicity and/or the extent of cell adhesion to hydrophobic liquids. The classical MATH assay involves spectrophotometric absorbance measurements of the initial and final cell concentrations in an aqueous cell suspension that has been contacted with a hydrocarbon liquid. In this study, microscopic examination of the aqueous cell suspension after contact with hexadecane or a hexadecane/toluene mixture revealed the presence of hydrocarbon droplets. The hydrocarbon droplets contributed to the absorbance values during spectrophotometric measurements and caused erroneous estimates of cell concentrations and extents of microbial adhesion. A modified MATH assay that avoids such artefacts is proposed here. In this modified assay, microscopic examination of the aqueous suspension and direct cell counts provides cell concentrations that are free of interference from hydrocarbon droplets. The presence of hydrocarbon droplets was noted in MATH assays performed with three bacterial strains, and two different hydrocarbons, at ionic strengths of 0.2mM and 20mM and pH 6. In these experiments, the formation of quasi-stable hydrocarbon droplets cannot be attributed to the presence of biosurfactants, or stabilization by biocolloids. The presence of surface potential at the hydrocarbon–water interface that was characterized by electrophoretic mobility of up to −1 and −2μmcm/Vs, likely caused the formation of the quasi-stable hydrocarbon droplets that provided erroneous results using the classical MATH assay. [Copyright &y& Elsevier]