Biofouling Resistance Research Articles

Polydopamine-Assisted Modification of Anion-Exchange Membranes with Nanomaterials for Improved Biofouling Resistance and Electrodialysis Performance

The present study is the first to systematically investigate the impact of membrane modification on antifouling propensity and desalination performance of anion-exchange membranes (Ionics AR204) by...

Mussel-inspired surface functionalization of polyamide microfiltration membrane with zwitterionic silver nanoparticles for efficient anti-biofouling water disinfection

Mature microfiltration (MF) membrane is a low-cost, effective, and promising technology to provide affordable purified water for people living in developing countries. However, the lack of disinfection ability and inherent membrane fouling problems have seriously restricted the large-scale application of conventional MF treatment system in producing safe drinking water. In this work, zwitterionic silver nanoparticles (AgNPs) with surface modification of poly(carboxybetaine acrylate-co-dopamine methacryamide) (PCBDA) copolymers were robustly immobilized onto commercial polyamide MF membrane via mussel-inspired chemistry for water disinfection. The designed microfiltration membrane, named as PCBDA@AgNPs-MF, exhibited integrated properties of high and stable payload of AgNPs, broad-spectrum anti-adhesive and antimicrobial activities, and easy removal of inactivated microbial cells from membrane surface. Ascribing to the synergetic effect of anti-adhesive and antimicrobial features brought by zwitterionic PCBDA@AgNPs, the biofilms growth on polyamide membrane surface was significantly inhibited, which showed potential access to achieve long-term biofouling resistance and maintain water flux for conventional MF membrane. As water disinfection device, these attributes enabled PCBDA@AgNPs-MF to effectively disinfect the model and natural bacteria-contaminated water.

Improving the biofouling resistance of polyamide thin-film composite membrane via grafting polyacrylamide brush on the surface by in-situ atomic transfer radical polymerization

Membrane biofouling represents a major challenge ever-present in the practical application of polyamide (PA) thin-film composite (TFC) reverse osmosis (RO) membranes. This work focused on grafting polyacrylamide (PAAm) onto PA-TFC via an in-situ atomic transfer radical polymerization (ATRP) method to improve the biofouling resistance of PA-TFC. The ATRP initiators, isobutyryl bromide (iPB), were introduced into PA matrix using a bifunctional small molecule, 2-bromoisobutyryl bromide (BIBB), added in organic hexane solutions to participate in interfacial polymerization through the condensation reaction with m-phenylenediamine. The successful introduction of iPB was confirmed by membrane surface characterizations, and the iPB density in PA layer was tuned by varying the BIBB concentrations in hexane solutions based on the variation in water permeance and salt rejections of iPB-loaded PA-TFC. The ATRP for the gradual growth of PAAm brush was thus in-situ achieved on the PA-TFC surface from the pre-incorporated iPB groups and the length of PAAm chains was facilely controlled via tuning ATRP polymerization time. The PAAm grafted PA-TFC exhibited a minimum decrement of water permeance and essentially retained salt rejections relative to the un-grafted ones. More importantly, the grafted membranes presented synergistically enhanced anti-adhesion and bacteriostatic performance towards either Gram-negative Escherichia coli (E. coli) or Gram-positive Bacillus subtilis (B. subtilis). Also, the grafted membranes presented a lower final flux decline ratio (FDRf) and higher final flux recovery ratio (FRRf) in relation with the un-grafted membranes in the dynamic bovine serum albumin (BSA) fouling test. Particularly, the membrane grafted with longer PAAm chains from extended grafting time showed better anti-biofouling performance: the sterilization ratio towards E. coli and B. subtilis achieved up to 98.8% and 99.0%, respectively, and FDRf of just 3.7% and FRRf of 97.6% after 3 × 8 h BSA fouling test for the membrane subjected to 2 h ATRP grafting. The PAAm grafting induced greater water wettability of membrane surface and the flexible chain structure of PAAm were proposed to account for the enhanced anti-adhesion and bacteriostasis towards bacteria, which collaboratively led to the improved biofouling resistance.

Thermostable antifouling zwitterionic vapor-induced phase separation membranes

Biofouling resistance of membranes is generally evaluated in normal conditions of temperature. Yet, some membranes can undergo heat treatments either before use (sterilization for biomedical use) or during operation (when temperature gradient is the driving force to the separation), which can impair the anti-biofouling material. Here, we prepared zwitterionic polyvinylidene fluoride membranes by the vapor-induced phase separation (VIPS) process, using a copolymer made of styrene units and zwitterionized 4-vinylpyridine. Membranes were fully characterized by a variety of physicochemical analyses to demonstrate the formation of bi-continuous structure and the presence of the zwitterionic copolymer on the surface of the membrane. Then, anti-biofouling properties were studied at ambient temperature using Escherichia coli bacteria, whole blood, platelet rich plasma and bovine serum albumin, before moving onto their assessment at higher temperature (60 °C) or after a steam sterilization of the membranes. Results demonstrated that anti-biofouling properties were sustained despite the heat treatment, while some common zwitterionic anti-biofouling materials (sulfobetaine methacrylate) is known to fail in similar conditions. Hence, the present membranes can be applied in a large variety of domains where bi-continuous microfiltration anti-biofouling membranes are needed and undergo heat exposure or heat treatment.

Desalination membranes with ultralow biofouling via synergistic chemical and topological strategies

Biofouling is a persistent problem for desalination and water treatment membranes because it critically degrades membrane performance. Here, we report desalination membranes with ultrahigh biofouling resistance fabricated using a synergistic anti-biofouling strategy that combines topological and chemical antifouling modifications. Specifically, both the surface topology and the chemistry of desalination membranes were tailored by creating a biomimetic Sharklet pattern and integrating hydrophilic tannic acid and biocidal silver nanoparticles (AgNPs). The resultant membrane significantly enhanced biofouling resistance compared to the membranes modified by either the topological or chemical modifications alone due to the combinatorial antifouling effect. Importantly, the topological anti-biofouling effect was much more significant than the chemical effect under dynamic flow conditions due to the unique surface flows generated by the Sharklet geometry. Interestingly, the surface flow characteristics of the Sharklet pattern also effectively suppressed the leaching of the incorporated AgNPs and thus prolonged their anti-biofouling effect, highlighting the synergistic effect of the proposed combination strategy. This approach opens a new avenue for the fabrication of functional membranes, coatings and surfaces with superior antifouling and self-cleaning functions by elucidating the underlying antifouling mechanisms.

Superhydrophobic, superamphiphobic and SLIPS materials as anti-corrosion and anti-biofouling barriers

Multifunctional interfacial materials with special wettability including superhydrophobic, superamphiphobic, and SLIPS exhibited promising potentials for corrosion and biofouling resistance.

Construction of Bi/Bi5O7I anchored on a polymer with boosted interfacial charge transfer for biofouling resistance and photocatalytic H2 evolution

The prepared coatings possess hydrogen production, antifouling performance, self-cleaning properties, this strategy can be a promising candidate to restrict biofouling and photocatalytic hydrogen production for marine coating applications.

Polyurethane coating with heterogeneity structure induced by microphase separation: A new combination of antifouling and cavitation erosion resistance

Cavitation erosion and biofouling are the most severe factors of metal materials fatigue failure and degradation in seawater. Herein, a series of hydrophobic fluorinated polyurethane coatings (SFPU-x) with various contents of fluorinated isocyanate prepolymer (FIP) were synthesized via a simple addition reaction for anti-cavitation erosion property combined with biofouling resistance. The microstructure and phase composition of as prepared coatings were analyzed by ATR-IR, SEM, TG, EDS and AFM. The addition of FIP increases the content of hard segments microregion and affects the microphase separation of the coating and induces the construction of surface heterogeneity microstructures. The static water contact angle and water absorption were measured as well. The antifouling tests were conducted using Nitzschia Closterium cell and the fluorescence labeled bovine serum albumin (FITC-BSA) as fouling models. Especially, the SFPU-5 coating with 5% FIP shows excellent antifouling and cavitation erosion resistance abilities due to surface heterogeneity microstructure, the attachment rates of FITC-BSA (1.1 %) and Nitzschia cell (1.3 %) far less than that of SFPU-0 coating (72.3 % and 85.1 %), respectively. Marine field test for 30 days also proven the antifouling properties of the SFPU-5 coating. In addition, there were no obvious holes and cracks on the surface of SFPU-5 after 10 h of cavitation, the cumulative mass loss were 2.7 mg and 2.9 mg in deionized water and in seawater, respectively.

Biofouling inhibition for aquaculture cage nets through a coating nano zinc and silicon oxides incorporated with polyaniline

Biofouling is one of the problems faced by cage aquaculture farmers, and its management is expensive. In this present study, polyethylene aquaculture cage nets were coated with the nano structured oxides of zinc and silicon incorporated with polyaniline. Fourier transform infrared spectroscopy and scanning electron microscope data evidenced that a thick coating of nano particle was formed on polyethylene. The oxides were attached to the quinoid part of polyaniline. The antifouling efficiency of treated cage net was tested by exposing in the Cochin estuary for three months. A webbing treated with 0.01% of each of the nano zinc oxide (ZnO) and silicon dioxide (SiO2) exhibited the highest biofouling resistance. Reinforcement of nano SiO2 with ZnO increased biofouling resistance as the former complemented the coating to make the system more efficient.

Improved biomarker quantification of silicon nanowire field-effect transistor immunosensors with signal enhancement by RNA aptamer: Amyloid beta as a case study

Quantifying proteins at ultra-low levels in high ionic-strength solutions by silicon nanowire field-effect transistor (SiNWFET) immunosensors is critically hindered due to the limited Debye length, charge distributions and uncontrollable orientations of protein molecules on the NW surfaces. In this study, we propose a novel strategy to overcome this issue by employing aptamer as bio-amplifier for different types of SiNWFET immunosensors to quantify Amyloid Beta (Aβ) 1-42, a biomarker for early-stage diagnosis of Alzheimer disease (AD) with ultra-low level in human serum (HS), as a representative target. Our method, presented for the first time, exhibits an outstanding performance in combination with mSAM-SiNWFET immunosensors (designed by integrating SiNWFET as transducer, mouse antibody as bio-receptor, and mixed self-assembled monolayers (mSAMs) for biofouling resistance) to sense Aβ 1-42 down to 100 fg/mL in HS, the lowest level achieved in comparison with the most advanced sensing technologies for Aβ 1-42. The empirical data also reveal that varied concentrations of Aβ 1-42 in diverse high ionic-strength environments (150 mM BTP and HS) express good linear relationship with signal amplified by aptamer. This novel approach is therefore potentially applied for early-stage diagnosis of AD and other clinical trials of biomarkers with ultra-low content in blood.

H2O2-Triggered Rapid Deposition of Poly(caffeic acid) Coatings: A Mechanism-Based Entry to Versatile and High-Efficient Molecular Separation.

Plant-derived polyphenol coating offers a promising route to fabricate functional surfaces for different substrate materials. However, almost all of the deposition approaches are time-consuming and involve inefficient processes, and the mechanisms behind the coating deposition are rarely understood. Herein, we report a rational methodology to achieve the rapid deposition of poly(caffeic acid) (PCA) by using H2O2 as a trigger under the assistance of copper sulfate (CuSO4). The comparative monomer structure of PCA oxidation polymerization has illustrated a significant distinction in the reaction path for PCA coating deposition which has never been reported before. Until now, the unprecedented fast velocity for polyphenol coating has been obtained, and the PCA coating exhibits excellent homogeneity, spatiotemporal tunability, and firm stability. Moreover, three different types of filtration membranes, poly(vinylidene fluoride) microfiltration membrane (PVDF MF membrane), poly(ether sulfone) (PES) ultrafiltration (UF) hollow fiber membrane, and PCA-coated PES nanofiltration (NF) membrane, are all successfully dip-coated using H2O2-triggered PCA coating. Without synthetic complexities and intricate procedures, the formation of hydrophilic and homogeneous PCA aggregates on the surface and/or inside pore walls resulted in various membranes. The as-prepared PCA-coated PVDF MF membrane demonstrates excellent oil/water separation efficiency of less than 150 ppm and a flux recovery rate of approximately 90% even after five cycles. By one-step co-deposition of PCA and poly(2-ethyl-2-oxazoline) (PEtOx) on the PES UF membrane surface, hydrophilicity and biofouling resistance are implemented for efficient protein filtration. The PES NF membrane formed by the PCA layer exhibits high mono-/divalent ion selectivity and excellent chlorine resistance. Overall, these results represent a rapid and sustainable approach to tailor PCA coatings for versatile liquid separation processes.

Low density lipoprotein (LDL) apheresis from blood plasma via anti-biofouling tuned membrane incorporated with graphene oxide-modified carrageenan

Graphene oxide (GO) and GO modified with carrageenan (GO-C) were incorporated into a tuned polysulfone/polyvinylpyrrolidone (PSf/PVP) membrane for the simultaneous separation of low-density lipoprotein (LDL) from blood plasma and the improvement of membrane resistance against biofouling. Several analyses including Fourier transform infrared (FTIR), Raman spectroscopy, energy-dispersive X-ray (EDX) elemental analysis, and mapping, X-ray diffraction (XRD), and also transmission electron microscopy (TEM) were used to study the GO and GO-C. Optical and scanning electron micrographs showed a uniform membrane surface with no aggregated particles. The morphology of the membrane cross-section revealed a double-compartment morphology for membranes containing GO (M-GOi) and GO-C (M-GO-Ci). Surface analyses including zeta potential (ZP) and water contact angle (WCA) confirmed a highly negative charge and hydrophilicity of M-GO-Ci membranes. Measurements indicated that with the addition of up to 0.7 wt% GO or GO-C, the molecular weight cut-off (MWCO) was kept between 1.1 and 1.2 million Dalton (mDa). The ratio of MWCO to molecular weight retention onset (MWRO) was determined to assess membrane selectivity; the results showed that M-GO-Ci membranes had lower values, which were more suitable for LDL apheresis. The results of blood plasma filtration tests confirmed the capability of both M-GOi and M-GO-Ci membranes to the simultaneous separate pathogenic factors, but the role of M-GO-Ci membranes toward passing other beneficial blood plasma components and reducing cardiovascular disease (CVD) risks was more tangible than the other membranes. Atomic force microscopy (AFM) results indicated that increasing membrane surface roughness especially for M-GO-Ci membranes, provided suitable conditions for the permeability of beneficial blood plasma components. Biofouling parameters confirmed that M-GO-Ci membranes had higher biofouling resistance than other membranes. Protein adsorption, prothrombin time (PT), and activated partial thromboplastin time (APTT) demonstrated the positive role of GO-C in the blood compatibility of membranes. Cell viability results showed no cytotoxicity for the membranes, implying the favorable interaction of cells and membranes especially for M-GO-Ci membranes.

Laser-induced graphitization of polydopamine leads to enhanced mechanical performance while preserving multifunctionality

Polydopamine (PDA) is a simple and versatile conformal coating material that has been proposed for a variety of uses; however in practice its performance is often hindered by poor mechanical properties and high roughness. Here, we show that blue-diode laser annealing dramatically improves mechanical performance and reduces roughness of PDA coatings. Laser-annealed PDA (LAPDA) was shown to be >100-fold more scratch resistant than pristine PDA and even better than hard inorganic substrates, which we attribute to partial graphitization and covalent coupling between PDA subunits during annealing. Moreover, laser annealing provides these benefits while preserving other attractive properties of PDA, as demonstrated by the superior biofouling resistance of antifouling polymer-grafted LAPDA compared to PDA modified with the same polymer. Our work suggests that laser annealing may allow the use of PDA in mechanically demanding applications previously considered inaccessible, without sacrificing the functional versatility that is so characteristic of PDA.

Enhanced biodeterioration and biofouling resistance of nanoparticles and inhibitor admixed fly ash based concrete in marine environments

In this paper, we report the enhanced biodeterioration and biofouling resistance of a modified fly ash based concrete, formulated by the addition of fly ash, nano-TiO2, nano-CaCO3, and corrosion inhibitor into conventional concrete. After six months of exposure in natural seawater, the modified fly ash based concrete showed a three to four order reduction in aerobic and anaerobic bacterial density, which was confirmed by epifluorescence and confocal microscopic investigations. The FESEM micrographs showed a characteristic surface morphology with uniform distribution of more calcium silicate hydrate (CSH) gels and aluminate hydrates, absence of discontinuities, pits, and cracks on the modified concrete surface which helped to resist the ingress of aggressive ions from seawater. The comparatively lesser reduction in surface pH, low water/cement ratio, better bulk thermal properties, and low surface roughness facilitated the improvement in the antimicrobial and antifouling properties of modified concrete. The addition of nanoparticles and inhibitor increased the hydration of cement resulting in the formation of more portlandite which got converted into more hydration products, producing a pore free morphology. The inherent photocatalytic activity of nano-anatase TiO2 and bactericidal activity of sodium nitrite due to the presence of reactive nitrogen species (RNS) together enhanced the biofouling and biodeterioration resistance.

Silver nanowire-carbon nanotube/coal-based carbon composite membrane with fascinating antimicrobial ability and antibiofouling under electrochemical assistance

Biofouling caused by microorganism is a serious problem that inhibits the application of membrane technology in wastewater treatment. To overcome this drawback, a novel silver nanowire-carbon nanotube/coal-based carbon (AgNW-CNT/CC) composite membrane was prepared with fascinating antimicrobial ability and electrochemically enhanced biofouling resistance. The addition of AgNWs could significantly enhance its antibacterial activity of the AgNW-CNT/CC composite membrane by releasing the silver ions or direct contact and accelerated bacterial detachment from membrane surface. The final flux of AgNW-CNT/CC composite membrane (70.5 % of its initial value) was 1.57 times higher than that for the CNT/CC membrane (45 % of its initial value) without an external voltage. Importantly, incorporating AgNWs was beneficial for electrochemical assistance, which exhibited a prominent synergistic antibiofouling performance. The flux of the cathodic AgNW-CNT/CC composite membrane was stable with acceptable flux loss (95.7 % of its initial value) under a low-voltage of 3.5 V, demonstrating the bacteria migration to the membrane surface can be inhibited by electrostatic repulsive and micro-bubbles generated via water electrolysis, thus promoting the inactivated bacteria to leave the membrane surface and avoid the formation of a biofilm, while the steady-state flux declined to 82.5 % of its initial value for electrochemically assisted CNT/CC membrane. Moreover, the regeneration of the fouled membrane can be achieved by applying an intermittent external voltage to promote the inactivated bacteria away from the membrane surface. These results suggested that the integration of electrochemistry with antimicrobial modification offers a new insight for biofouling mitigation during membrane separation.

Development of Polyvinylidene Fluoride Membrane by Incorporating Bio-Based Ginger Extract as Additive.

Biofouling on the membrane surface leads to performance deficiencies in membrane filtration. In this study, the application of ginger extract as a bio-based additive to enhance membrane antibiofouling properties was investigated. The extract was dispersed in a dimethyl acetamide (DMAc) solvent together with polyvinylidene fluoride (PVDF) to enhance biofouling resistance of the resulting membrane due to its antibiotic property. The concentrations of the ginger extract in the dope solution were varied in the range of 0–0.1 wt %. The antibacterial property of the resulting membranes was assessed using the Kirby Bauer disc diffusion method. The results show an inhibition zone formed around the PVDF/ginger membrane against Escherichia coli and Staphylococcus aureus demonstrating the efficacy of the residual ginger extract in the membrane matrix to impose the antibiofouling property. The addition of the ginger extract also enhanced the hydrophilicity in the membrane surface by lowering the contact angle from 93° to 85°, which was in good agreement with the increase in the pure water flux of up to 62%.

Interactions of Fe-N-S Co-Doped Porous Carbons with Bacteria: Sorption Effect and Enzyme-Like Properties.

Carbon-based (nano)materials doped with transition metals, nitrogen and other heteroatoms are considered active heterogeneous catalysts in a wide range of chemical processes. Recently they have been scrutinized as artificial enzymes since they can catalyze proton-coupled electron transfer reactions vital for living organisms. Herein, interactions between Gram-positive and Gram-negative bacteria and either metal-free N and/or S doped or metal containing Fe–N–S co-doped porous carbons are studied. The Fe- and N-co-doped porous carbons (Fe–N–C) exhibit enhanced affinity toward bacteria as they show the highest adsorption capacity. Fe–N–C materials also show the strongest influence on the bacteria viability with visible toxic effect. Both types of bacteria studied reacted to the presence of Fe-doped carbons in a similar manner, showing a decrease in dehydrogenases activity in comparison to controls. The N-coordinated iron-doped carbons (Fe–N–C) may exhibit oxidase/peroxidase-like activity and activate O2 dissolved in the solution and/or oxygen-containing species released by the bacteria (e.g., H2O2) to yield highly bactericidal reactive oxygen species. As Fe/N/ and/or S-doped carbon materials efficiently adsorb bacteria exhibiting simultaneously antibacterial properties, they can be applied, inter alia, as microbiological filters with enhanced biofouling resistance.

Monitoring of ammonia in marine waters using a passive sampler with biofouling resistance and neural network-based calibration

A biofouling resistant passive sampler for ammonia, where the semi-permeable barrier is a microporous hydrophobic gas-diffusion membrane, has been developed for the first time and successfully applied to determine the time-weighted average concentration of ammonia in estuarine and coastal waters for 7 days. Strategies to control biofouling of the membrane were investigated by covering it with either a copper mesh or a silver nanoparticle functionalised cotton mesh, with the former approach showing better performance. The effects of temperature, pH and salinity on the accumulation of ammonia in the newly developed passive sampler were studied and the first two parameters were found to influence it significantly. A universal calibration model for the passive sampler was developed using the Group Method Data Handling algorithm based on seawater samples spiked with known concentrations of total ammonia under conditions ranging from 10 to 30 °C, pH 7.8 to 8.2 and salinity 20 to 35. The newly developed passive sampler is affordable, user-friendly, reusable, sensitive, and can be used to detect concentrations lower than the recently proposed guideline value of 160 μg total NH3–N L−1, for a 99% species protection level, with the lowest concentration measured at 17 nM molecular NH3 (i.e., 8 μg total NH3–N L−1 at pH 8.0 and 20 °C). It was deployed at four field sites in the coastal waters of Nerm (Port Phillip Bay), Victoria, Australia. Good agreement was found between molecular ammonia concentrations obtained with passive and discrete grab sampling methods (relative difference, - 12% to - 19%).

Intrinsically antibacterial thin film composite membranes with supramolecularly assembled lysozyme nanofilm as selective layer for molecular separation

Biofouling is a pervasive and crucial issue in membrane separation processes, as it leads to the deterioration in separation efficiency. To address this issue, the antibacterial membrane with high biofouling resistance is in urgent demand, what has been remained challenging. In this work, an intrinsically antibacterial thin film composite (TFC) membranes was prepared using supramolecularly assembled lysozyme (SAL) nanofilm as a selective layer. The nanofilms were achieved by depositing onto a hydrolyzed polyacrylonitrile (h-PAN) support membrane using phase transition and aggregation of lysozyme from its aqueous solution. The prepared membranes showed a high rejection ratio towards vitamin B12 (95.3%) with a water permeation flux of 48.6 L·m−2·h−1 under 0.4 MPa, showing great potential in the molecular separation. Furthermore, the antibacterial efficiencies of the typical membrane toward E. coli and S. aureus reached 93.2% and 92.2%, respectively, indicating that the SAL selective layer can effectively resist bacterial adhesion and reproduction on the membrane surface. This work provides an innovative strategy and insight in fabricating the high-performance antibacterial TFC membranes for aqueous molecular separation via protein supramolecular assembly.

Investigation of Biocidal Effect of Microfiltration Membranes Impregnated with Silver Nanoparticles by Sputtering Technique.

Silver nanoparticles were loaded in microfiltration membranes by sputtering technique for the development of biocidal properties and biofouling resistance. This technology allows good adhesion between silver nanoparticles and the membranes, and fast deposition rate. The microfiltration membranes (15 wt.% polyethersulfone and 7.5 wt.% polyvinylpyrrolidone in N,N-dimethylacetamide) were prepared by phase inversion method, and silver nanoparticles were deposited on their surface by the physical technique of vapor deposition in a sputtering chamber. The membranes were characterized by Field Emission Scanning Electron Microscopy, and the presence of silver was investigated by Energy-Dispersive Spectroscopy and X-ray Diffraction. Experiments of silver leaching were carried out through immersion and filtration tests. After 10 months of immersion in water, the membranes still presented ~90% of the initial silver, which confirms the efficiency of the sputtering technique. Moreover, convective experiments indicated that 98.8% of silver remained in the membrane after 24 h of operation. Biocidal analyses (disc diffusion method and biofouling resistance) were performed against Pseudomonas aeruginosa and confirmed the antibacterial activity of these membranes with 0.6 and 0.7 log reduction of viable planktonic and sessile cells, respectively. These results indicate the great potential of these new membranes to reduce biofouling effects.