Effect of surface wettability on the adhesion of proteins

Polyaniline-based bovine serum albumin imprinted electrochemical sensor for ultra-trace-level detection in clinical and food safety applications

Monitoring bovine serum albumin (BSA) at ultra-low levels is crucial for clinical and food safety applications, as it plays a significant role in identifying various health conditions and potential risks, necessitating fast, trace-level detection of BSA. This study proposes an approach to address these challenges by employing molecularly imprinted polymer (MIP) to develop an ultra-trace-level and cost-effective BSA sensing platform. The MIP electrochemical sensor was developed using polyaniline (PANI) combined with the protein crosslinker glutaraldehyde (GA) to optimize BSA surface imprinting in the MIP. As a result, the sensor achieves a sensitivity of 1.24 μA/log(pg/mL), with a picomolar detectable limit of 2.3 pg/mL (0.035 pM) and a wide detection range from 20 pg/mL to 200,000 pg/mL (0.303 pM to 3030 pM), making it suitable for clinical and food safety applications. Additionally, the study explores the interaction between an acidic surfactant protein eluent (acetic acid with sodium dodecyl sulfate, AcOH-SDS) and BSA vacant sites, enhancing recognition and re-binding. The PANI-based MIP sensor demonstrates initial feasibility and practicality in commercial milk and real human serum, opening avenues for early disease detection and ensuring food safety in BSA-related immune responses.

Surface modification of polydimethylsiloxane by the cataractous eye protein isolate

Polydimethylsiloxane (PDMS), even though widely used in microfluidic applications, its hydrophobic nature restricts its utility in some cases. To address this, PDMS may be used in conjunction with a hydrophilic material. Herein, the PDMS surface is modified by plasma treatment followed by cross-linking with the cataractous eye protein isolate (CEPI). CEPI-PDMS composites are prepared at three pH and the effects of CEPI on the chemical, physical, and electrical properties of PDMS are extensively investigated. The cross-linking between PDMS and the protein are confirmed by FTIR, and the contact angle measurements indicate the improved hydrophilic nature of the composite films as compared to PDMS. Atomic Force Microscopy results demonstrate that the surface roughness is enhanced by the incorporation of the protein and is a function of the pH. The effective elastic modulus of the composites is improved by the incorporation of protein into the PDMS matrix. Measurements of the dielectric properties of these composites indicate that they behave as capacitors at lower frequency range while demonstrating resistive characteristics at higher frequency. These composites provide preliminary ideas in developing flexible devices for potential applications in diverse areas such as energy storage materials, and thermo-elective wireless switching devices.

Understanding the "Berg limit": the 65° contact angle as the universal adhesion threshold of biomatter

Surface phenomena in aqueous environments such as long-range hydrophobic attraction, macromolecular adhesion, and even biofouling are predominantly influenced by a fundamental parameter-the water contact angle. The minimal contact angle required for these and related phenomena to occur has been repeatedly reported to be around 65° and is commonly referred to as the "Berg limit." However, the universality of this specific threshold across diverse contexts has remained puzzling. In this perspective article, we aim to rationalize the reoccurrence of this enigmatic contact angle. We show that the relevant scenarios can be effectively conceptualized as three-phase problems involving the surface of interest, water, and a generic oil-like material that is representative of the nonpolar constituents within interacting entities. Our analysis reveals that attraction and adhesion emerge when substrates display an underwater oleophilic character, corresponding to a "hydrophobicity under oil", which occurs for contact angles above approximately 65°. This streamlined view provides valuable insights into macromolecular interactions and holds implications for technological applications.

Tailoring Thermoresponsive Polymer Architecture to Enhance Antifouling and Fouling Reversibility of Membranes

Cleaning a fouled membrane using warm water, instead of commonly used fouling control chemicals, is an approach advocated in resource-limited settings, where small-scale membrane filtration is used to provide clean water. Thermoresponsive polymers coated onto membranes undergo a conformational change across their lower critical solution temperature (LCST), enabling foulant removal during such temperature-swing cleaning. However, their intrinsic hydrophobicity above the LCST poses a fundamental material challenge. In this study, we examine how thermoresponsive polymers can be optimally copolymerized with hydrophilic polymers by precisely manipulating monomer arrangement of thermoresponsive N-isopropylacrylamide and hydrophilic 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate. We successfully grafted these copolymers with different monomer arrangements onto poly(ether sulfone) ultrafiltration membranes while maintaining other polymer characteristics, such as the degree of polymerization and grafting density, constant. We found that placing hydrophilic polymer blocks at the outermost surface above the thermoresponsive polymer blocks is critical to achieving high surface hydrophilicity while preserving the thermoresponsive functionality. We demonstrate enhanced fouling resistance and efficient temperature-swing cleaning with optimized copolymer design based on their interaction with bovine serum albumin during static adsorption, filtration, and cleaning processes. These findings emphasize the importance of accurately tailoring the polymer architecture to enable more efficient filtration with reduced fouling and the capability to effectively clean the fouled membrane by simply using warm water.

Multi-scale, multi-level anisotropic silk fibroin/metformin scaffolds for repair of peripheral nerve injury

Silk fibroin (SF) as a natural polymer has a long history of application in various regenerative medicine fields, but there are still many shortcomings in silk fibroin for using as nerve scaffolds, which limit its clinical application in peripheral nerve regeneration (PNR). In this work, a multi-scale and multi-level metformin (MF)-loaded silk fibroin scaffold with anisotropic micro-nano composite topology was prepared by micromolding electrospinning for accelerating PNR. The scaffolds were characterized for morphology, wettability, mechanical properties, degradability, and drug release, and Schwann cells (SCs) and dorsal root ganglia (DRG) were cultured on the scaffolds to assess their effects on neural cell behavior. Finally, the gene expression differences of neural cells cultured on scaffolds were analyzed by gene sequencing and RT-qPCR to explore the possible signaling pathways and mechanisms. The results showed that the scaffolds had excellent mechanical properties and hydrophilicity, slow degradation rate and drug release rate, which were enough to support the repair of peripheral nerve injury for a long time. In Vitro cell experiments showed that the scaffolds could significantly promote the orientation of SCs and axons extension of DRG. Gene sequencing and RT-qPCR revealed that the scaffolds could up-regulate the expression of genes related to SCs proliferation, adhesion, migration, and myelination. In summary, the scaffolds hold great potential for promoting PNR at the micro/nano multiscale and physical/chemical levels and show promising application for the treatment of peripheral nerve injury in the future.

Advances in surface modifications of the silicone breast implant and impact on its biocompatibility and biointegration

Silicone breast implants are commonly used for cosmetic and oncologic surgical indications owing to their inertness and being nontoxic. However, complications including capsular contracture and anaplastic large cell lymphoma have been associated with certain breast implant surfaces over time. Novel implant surfaces and modifications of existing ones can directly impact cell-surface interactions and enhance biocompatibility and integration. The extent of foreign body response induced by breast implants influence implant success and integration into the body. This review highlights recent advances in breast implant surface technologies including modifications of implant surface topography and chemistry and effects on protein adsorption, and cell adhesion. A comprehensive online literature search was performed for relevant articles using the following keywords silicone breast implants, foreign body response, cell adhesion, protein adsorption, and cell-surface interaction. Properties of silicone breast implants impacting cell-material interactions including surface roughness, wettability, and stiffness, are discussed. Recent studies highlighting both silicone implant surface activation strategies and modifications to enhance biocompatibility in order to prevent capsular contracture formation and development of anaplastic large cell lymphoma are presented. Overall, breast implant surface modifications are being extensively investigated in order to improve implant biocompatibility to cater for increased demand for both cosmetic and oncologic surgeries.

Tailoring the Hydrophilicity for Delayed Condensation Frosting in Antifogging Coatings

In the last few decades, numerous studies have focused on designing suitable hydrophilic materials to inhibit surface-induced fog or frost under extreme conditions. As fogging and condensation frosting on a film involves molecular interaction with water prior to forming discrete droplets on the surface, it is essential to control the extent of a film to strongly bind with water molecules for antifogging coatings. While the water contact angle measurement is commonly used to probe the hydrophilicity of a film, it oftentimes fails to predict the antifogging and antifrosting performance as this value only reflects the wettability of a given surface to water droplet. In this work, a polysaccharide-based film composed of chitosan (CHI) and carboxymethyl cellulose (CMC) is used as the model system and oligo(ethylene glycol) (OEG) moieties are additionally introduced to study the effect of OEG moieties on antifogging and condensation frosting. We show that the film containing OEG-grafted CHI exhibits excellent frost-resistant capability due to the OEG moieties in the film that serve as active sites for water molecules to strongly interact in a nonfreezable state.

Adsorption characteristics of peptides on ω-functionalized self-assembled monolayers: a molecular dynamics study

Molecular dynamics simulations were employed to investigate the adsorption behavior of a variety of amino-acid side-chain analogs (SCAs) and a β-hairpin (HP7) peptide on a series of liquid-like self-assembled monolayers (SAMs) with terminal functional groups of -OH, -OCH₃, -CH₃, and -CF₃. The relationships between the adsorption free energy of the SCAs and the interfacial properties of water on the SAMs were examined to determine the acute predictors of protein adsorption on the SAM surfaces. The structural changes of HP7 on the SAM surfaces were also investigated to understand the relationship between the surface nature and protein denaturation. It was found that the adsorption free energy of the SCAs was linearly related to the surface hydrophobicity, which was computed as the free energy of cavity formation near the SAM-water interfaces. In addition, the hydrophobic -CH₃ and -CF₃ SAMs produced substantial conformational changes in HP7 because of the strong hydrophobic attractions to the nonpolar side chains. The hydrophilic surface terminated by -OH also promoted structural changes in HP7 resulting from the formation of hydrogen bonds between the hydrophilic tail and HP7. Consequently, the moderate amphiphilic surface terminated by -OCH₃ avoided the denaturation of HP7 most efficiently, thus improving the biocompatibility of the surface. In conclusion, these results provide a deep understanding of protein adsorption for a wide range of polymeric surfaces, and they can potentially aid the design of appropriate biocompatible coatings for medical applications.

Versatile and Easily Designable Polyester-Laser Toner Interfaces for Site-Oriented Adsorption of Antibodies

Laser toners appear as attractive materials for barriers and easily laminated interphases for Lab-on-a-Foil microfluidics, due to the excellent adhesion to paper and various membranes or foils. This work shows for the first time a comprehensive study on the adsorption of antibodies on toner-covered poly(ethylene terephthalate) (PET@toner) substrates, together with assessment of such platforms in rapid prototyping of disposable microdevices and microarrays for immunodiagnostics. In the framework of presented research, the surface properties and antibody binding capacity of PET substrates with varying levels of toner coverage (0–100%) were characterized in detail. It was proven that polystyrene-acrylate copolymer-based toner offers higher antibody adsorption efficiency compared with unmodified polystyrene and PET as well as faster adsorption kinetics. Comparative studies of the influence of pH on the effectiveness of antibodies immobilization as well as measurements of surface ζ-potential of PET, toner, and polystyrene confirmed the dominant role of hydrophobic interactions in adsorption mechanism. The applicability of PET@toner substrates as removable masks for protection of foil against permanent hydrophilization was also shown. It opens up the possibility of precise tuning of wettability and antibody binding capacity. Therefore, PET@toner foils are presented as useful platforms in the construction of immunoarrays or components of microfluidic systems.

Selective strategies for antibacterial regulation of nanomaterials

Recalcitrant bacterial infection, as a worldwide challenge, causes large problems for human health and is attracting great attention. The excessive antibiotic-dependent treatment of infections is prone to induce antibiotic resistance. A variety of unique nanomaterials provide an excellent toolkit for killing bacteria and preventing drug resistance. It is of great importance to summarize the design rules of nanomaterials for inhibiting the growth of pathogenic bacteria. We completed a review involving the strategies for regulating antibacterial nanomaterials. First, we discuss the antibacterial manipulation of nanomaterials, including the interaction between the nanomaterial and the bacteria, the damage of the bacterial structure, and the inactivation of biomolecules. Next, we identify six main factors for controlling the antibacterial activity of nanomaterials, including their element composition, size dimensions, surface charge, surface topography, shape selection and modification density. Every factor possesses a preferable standard for maximizing antibacterial activity, providing universal rules for antibacterial regulation of nanomaterials. We hope this comprehensive review will help researchers to precisely design and synthesize nanomaterials, developing intelligent antibacterial agents to address bacterial infections.

Effect of acid-alkali treatment on serum protein adsorption and bacterial adhesion to porous titanium

Modification of the titanium (Ti) surface is widely known to influence biological reactions such as protein adsorption and bacterial adhesion in vivo, ultimately controlling osseointegration. In this study, we sought to investigate the correlation of protein adsorption and bacterial adhesion with the nanoporous structure of acid-alkali-treated Ti implants, shedding light on the modification of Ti implants to promote osseointegration. We fabricated nontreated porous Ti (NTPT) by powder metallurgy and immersed it in mixed acids and NaOH to obtain acid-alkali-treated porous Ti (AAPT). Nontreated dense sample (NTDT) served as control. Our results showed that nanopores were formed after acid-alkali treatment. AAPT showed a higher specific surface area and became much more hydrophilic than NTPT and NTDT (p < 0.001). Compared to dense samples, porous samples exhibited a lower zeta potential and higher adsorbed protein level at each time point within 120 min (p < 0.001). AAPT formed a thicker protein layer by serum precoating than NTPT and NTDT (p < 0.001). The main adsorbed proteins on AAPT and NTPT were albumin, α1 antitrypsin, transferrin, apolipoprotein A1, complement C3 and haptoglobin α1 chain. The amounts of bacteria adhering to the serum-precoated samples were lower than those adhering to the nonprecoated samples (p < 0.05). Lower-molecular-weight proteins showed higher affinity to porous Ti. In conclusion, acid-alkali treatment facilitated protein adsorption by porous Ti, and the protein coating tended to prevent bacteria from adhering. These findings may be utilized for Ti implant modification aimed at reducing bacterial adhesion and enhancing osseointegration. Graphical abstract.

In Situ Regeneration of Silicon Microring Biosensors Coated with Parylene C

Optical biosensors support disease diagnostic applications, offering high accuracy and sensitivity due to label-free detection and their optical resonance enhancement. However, optical biosensors based on noble metal nanoparticles and precise micro-electromechanical system technology are costly, which is an obstacle for their applications. Here, we proposed a biosensor reuse method with nanoscale parylene C film, taking the silicon-on-insulator microring resonator biosensor as an example. Parylene C can efficiently adsorb antibody by one-step modification without any surface treatment, which simplifies the antibody modification process of sensors. Parylene C (20 nm thick) was successfully coated on the surface of the microring to modify anti-carcinoembryonic antigen (anti-CEA) and specifically detect CEA. After sensing, parylene C was successfully removed without damaging the sensing surface for the sensor reusing. The experimental results demonstrate that the sensing response did not change significantly after the sensor was reused more than five times, which verifies the repeatability and reliability of the reusable method by using parylene C. This framework can potentially reduce the cost of biosensors and promote their further applications.

Self-adhering implantable device of titanium: Enhanced soft-tissue adhesion by sandblast pretreatment

Self-adhering implantable devices, which can be immobilized inside the bodies without suturing nor organic glues, made of metallic biomaterials would be optimal devices for preventing device-related complications such as device migration after implantation. We reported previously that acid-treated commercially-pure titanium (CpTi) adhered directly and immediately on hydrous non-keratinized soft tissues. Herein, we investigated the influence of sandblasting as pretreatment for acid-treated CpTi to increase its soft tissue adhesiveness. First, the effects of sandblasting conditions (i.e., pressure, distance and time) were investigated in terms of the sandblasted surface area and the degree of deformation (i.e., internal stress formation) of CpTi films. The effect of the sandblasting on the immediate soft tissue adhesion of acid-treated CpTi was investigated using an ex vivo shear adhesion test with mouse dermal tissues. The optimal sandblasting pretreatment remarkably improved the soft tissue adhesion strength of acid-treated CpTi (102 ± 19 kPa) compared with the non-sandblasted counterparts (41 ± 2 kPa). Finally, the CpTi adhesive was applied for immobilizing a near field communication (NFC) device in vivo, and was shown to have strong immediate adhesion to muscle fascia.

Competition between Hydrogen Bonding and Dispersion Force in Water Adsorption and Epoxy Adhesion to Boron Nitride: From the Flat to the Curved

Hexagonal boron nitride (h-BN) is a material with excellent thermal conductivity and electrical insulation, used as an additive to various matrices. To increase the affinity of h-BN to them, hydrogen bonds should be formed at the interface. In reality, however, they are not formed; the N atoms are not capable of accepting hydrogen bonds due to the delocalization of their lone pair electrons over the B-N π bonds. To make it form hydrogen bonds, one may need to break the planarity of h-BN so that the orbital overlap in the B-N π bonds can be reduced. This idea is verified with first-principles calculations on the adsorption of a water molecule on hypothetical h-BN surfaces, the planarity of which is broken. One can do it in silico but not in vitro. BN nanotubes (BNNTs) are considered as a more realistic BN surface with nonplanarity. The hydrogen bond is shown to become stronger as the curvature of the tube increases. On the contrary, the strength of the dispersion force acting at the interface becomes weaker. In water adsorption, these two interactions are in competition with each other. However, in epoxy adhesion, the interaction due to dispersion forces is overwhelmingly stronger than that due to hydrogen bonding. The smaller the curvature of the surface, the smaller the distance between more atoms at the interface; thus, the interaction due to dispersion forces maximized.

An aqueous-based process to bioactivate poly(ε-caprolactone)/mesoporous bioglass composite surfaces by prebiotic chemistry-inspired polymer coatings for biomedical applications

Despite the wide use of aliphatic polyesters, such as poly(L-lactic acid) (PLLA) and poly(ε-caprolactone) (PCL), for many biomedical applications, these materials are limited due to their hydrophobic properties and lack of functional groups to bond with ligands to enhance the cell reorganization. Recently, a composite consisting of bioglass and PCL was demonstrated to enhance the mechanical strength and to improve the degradation rate. Although numerous approaches have been developed to improve the wettability of aliphatic polyesters to create a favorable interface with cells, only few surface modification methods can be independently applied to surfaces with different material. In this work, mesoporous bioglass (MBG) nanoparticles embedded in PCL films were modified by the polymerization of aminomalonitrile (AMN) with 3,4,5-trihydroxybenzaldehyde (THBA). The copolymer layer was further utilized as a mediator to conjugate chitosan and evaluate the antibacterial efficacy. Our results show that the hydrophilicity of the composite membranes significantly improved after treatment. In addition, after immersion in simulated body fluid (SBF) for 14 days, hydroxyapatite formation was only observed on the treated membranes. This result demonstrates that the surface treatment did not alter the MBG bioactivity. Moreover, the cell culture results reveal that the extension level of cells and expression of alkaline phosphatase activity (ALP) of osteoblast-like (MG63) cells were higher on treated composite films compared to untreated ones. The results imply that the treatment procedure can be simultaneously and homogeneously applied to the organic/inorganic composites. In addition, Staphylococcus aureus adhesion on AMN-co-THBA and chitosan/ AMN-co-THBA was significantly lower than untreated PCL. Moreover, the percentage of dead bacteria was highest on the chitosan/ AMN-co-THBA membranes. These results indicate that the AMN-co-THBA modification can be used in composite materials and complex constructs, and it provides a potential method to create versatile surface properties for biomedical applications.

Biodegradable Anti-Biofilm Fiber-Membrane Ureteral Stent Constructed with a Robust Biomimetic Superhydrophilic Polycationic Hydration Surface Exhibiting Synergetic Antibacterial and Antiprotein Properties

The biofouling of ureteral stents and subsequent urinary tract infections mainly come from the adsorption and adhesion of proteins and microorganisms and their ensuing proliferation. Although general polycationic surfaces in implants have good antibacterial activities, they suffer from limited durability due to severe protein and bacterial adsorption. Here, a biodegradable and anti-biofilm fiber-membrane structured ureteral stent (FMBUS) with synergetic contact-killing antibacterial activity and antiprotein adsorption is described. The stent is prepared by generating hyperbranched poly(amide-amine)-grafted polydopamine microparticles (≈300 nm) on the surface of fibers by in situ polymerization and Schiff base reactions. The biomimetic surface endows the FMBUS with a positive charge (+21.36 mV) and superhydrophilicity (water contact angle: 0°). As a result, the stents fulfilled the following functions: i) reduced attachment of host protein due to superhydrophilicity (Lysozyme: 92.1%; human serum albumin: 39.4%); ii) high bactericidal activities against contact pathogenic bacteria (contact-killing rate: 99.9999% for both E. coli and S. aureus; antiadhesion rate: 99.2% for E. coli and 99.9999% for S. aureus); iii) biocompatibility in vitro (relative growth rate of L929: >90% on day 3) and in vivo; and iv) gradient biodegradability to avoid a second surgery of stent extraction 1-2 weeks after implantation.

Precise and rapid solvent-assisted geometric protein self-patterning with submicron spatial resolution for scalable fabrication of microelectronic biosensors

Precise and high-resolution coupling of functional proteins with micro-transducers is critical for the manufacture of miniaturized bioelectronic devices. Moreover, electrochemistry on microelectrodes has had a major impact on electrochemical analysis and sensor technologies, since the small size of microelectrode affects the radial diffusion flux of the analyte to deliver enhanced mass transport and electrode kinetics. However, a large technology gap has existed between the process technology associated with such microelectronics and the conventional bio-conjugation techniques that are generally used. Here, we report on a high-resolution and rapid geometric protein self-patterning (GPS) method using solvent-assisted protein-micelle adsorption printing to couple biomolecules onto microelectrodes with a minimum feature size of 5 μm and a printing time of about a minute. The GPS method is versatile for micropatterning various biomolecules including enzymes, antibodies and avidin-biotinylated proteins, delivering good geometric alignment and preserving biological functionality. We further demonstrated that enzyme-coupled microelectrodes for glucose detection exhibited good electrochemical performance which benefited from the GPS method to maximize effective signal transduction at the bio-interface. These microelectrode arrays maintained fast convergent analyte diffusion displaying typical steady-state I-V characteristics, fast response times, good linear sensitivity (0.103 nA mm^-2 mM^-1, R² = 0.995) and an ultra-wide linear dynamic range (2-100 mM). Our findings provide a new technical solution for the precise and accurate coupling of biomolecules to a microelectronic array with important implications for the scaleup and manufacture of diagnostics, biofuel cells and bioelectronic devices that could not be realized economically by other existing techniques.

The role of surfaces on amyloid formation

Interfaces can strongly accelerate or inhibit protein aggregation, destabilizing proteins that are stable in solution or, conversely, stabilizing proteins that are aggregation-prone. Although this behaviour is well-known, our understanding of the molecular mechanisms underlying surface-induced protein aggregation is still largely incomplete. A major challenge is represented by the high number of physico-chemical parameters involved, which are highly specific to the considered combination of protein, surface properties, and solution conditions. The key aspect determining the role of interfaces is the relative propensity of the protein to aggregate at the surface with respect to bulk. In this review, we discuss the multiple molecular determinants that regulate this balance. We summarize current experimental techniques aimed at characterizing protein aggregation at interfaces, and highlight the need to complement experimental analysis with theoretical modelling. In particular, we illustrate how chemical kinetic analysis can be combined with experimental methods to provide insights into the molecular mechanisms underlying surface-induced protein aggregation, under both stagnant and agitation conditions. We summarize recent progress in the study of important amyloids systems, focusing on selected relevant interfaces.

Correlating the Influence of Disulfides in Monolayers across Photoelectron Spectroscopy Wettability and Tunneling Charge-Transport

Despite their ubiquity, self-assembled monolayers (SAMs) of thiols on coinage metals are difficult to study and are still not completely understood, particularly with respect to the nature of thiol-metal bonding. Recent advances in molecular electronics have highlighted this deficiency due to the sensitivity of tunneling charge-transport to the subtle differences in the overall composition of SAMs and the chemistry of their attachment to surfaces. These advances have also challenged assumptions about the spontaneous formation of covalent thiol-metal bonds. This paper describes a series of experiments that correlate changes in the physical properties of SAMs to photoelectron spectroscopy to unambiguously assign binding energies of noncovalent interactions to physisorbed disulfides. These disulfides can be converted to covalent metal-thiolate bonds by exposure to free thiols, leading to the remarkable observation of the total loss and recovery of length-dependent tunneling charge-transport. The identification and assignment of physisorbed disulfides solve a long-standing mystery and reveal new, dynamic properties in SAMs of thiols.

Altered Surface Hydrophilicity on Copolymer Scaffolds Stimulate the Osteogenic Differentiation of Human Mesenchymal Stem Cells

BACKGROUND

Recent studies have suggested that both poly(l-lactide-co-1,5-dioxepan-2-one) (or poly(LLA-co-DXO)) and poly(l-lactide-co-ε-caprolactone) (or poly(LLA-co-CL)) porous scaffolds are good candidates for use as biodegradable scaffold materials in the field of tissue engineering; meanwhile, their surface properties, such as hydrophilicity, need to be further improved.

METHODS

We applied several different concentrations of the surfactant Tween 80 to tune the hydrophilicity of both materials. Moreover, the modification was applied not only in the form of solid scaffold as a film but also a porous scaffold. To investigate the potential application for tissue engineering, human bone marrow mesenchymal stem cells (hMSCs) were chosen to test the effect of hydrophilicity on cell attachment, proliferation, and differentiation. First, the cellular cytotoxicity of the extracted medium from modified scaffolds was investigated on HaCaT cells. Then, hMSCs were seeded on the scaffolds or films to evaluate cell attachment, proliferation, and osteogenic differentiation. The results indicated a significant increasing of wettability with the addition of Tween 80, and the hMSCs showed delayed attachment and spreading. PCR results indicated that the differentiation of hMSCs was stimulated, and several osteogenesis related genes were up-regulated in the 3% Tween 80 group. Poly(LLA-co-CL) with 3% Tween 80 showed an increased messenger Ribonucleic acid (mRNA) level of late-stage markers such as osteocalcin (OC) and key transcription factor as runt related gene 2 (Runx2).

CONCLUSION

A high hydrophilic scaffold may speed up the osteogenic differentiation for bone tissue engineering.

Comparison of Protein-Repellent Behavior of Linear versus Dendrimer-Structured Surface-Immobilized Polymers

For many biomedical applications, material surfaces should not only prevent unspecific protein adsorption and bacterial attachment as in many other applications in the food, health, or marine industry, but they should also promote the adhesion of tissue cells. In order to take a first step toward the challenging development of protein and bacteria-repelling and cell-adhesion-promoting materials, polyamine and poly(amido amine) surface coatings with terminal amine groups and varying structure (dendrimer, oligomer, polymer) were immobilized on model surfaces via silane chemistry. Physicochemical analysis showed that all modifications are hydrophilic (contact angles <60°) and possess similar surface free energies (SFEs, ∼46-54 mN/m), whereas their amine group densities and zeta potentials at physiological conditions (pH 7.4) varied greatly (-50 to +75 mV). In protein adsorption experiments with single proteins (human serum albumin (HSA) and lysozyme) as well as complex physiological fluids (fetal bovine serum (FBS) and human saliva), the amounts of adsorbed protein were found to correlate strongly with the zeta potential of the surface coatings. Both modifications based on linear polymers exhibited good protein repellency toward all proteins examined and are thus promising for testing in cell adhesion studies.

Polyelectrolyte Multilayer Films Modification with Ag and rGO Influences Platelets Activation and Aggregate Formation under In Vitro Blood Flow

Surface functionalization of materials to improve their hemocompatibility is a challenging problem in the field of blood-contacting devices and implants. Polyelectrolyte multilayer films (PEMs), which can mimic functions and structure of an extracellular matrix (ECM), are a promising solution to the urgent need for functional blood-contacting coatings. The properties of PEMs can be easily tuned in order to provide a scaffold with desired physico-chemical parameters. In this study chitosan/chondroitin sulfate (Chi/CS) polyelectrolyte multilayers were deposited on medical polyurethane. Afterwards PEMs were modified by chemical cross-linking and nanoparticles introduction. Coatings with variable properties were tested for their hemocompatibility in the cone-plate tester under dynamic conditions. The obtained results enable the understanding of how substrate properties modulate PEMs interaction with blood plasma proteins and the morphotic elements.

Fast automated processing of AFM PeakForce curves to evaluate spatially resolved Young modulus and stiffness of turgescent cells

Atomic Force Microscopy (AFM) is a powerful technique for the measurement of mechanical properties of individual cells in two (x × y) or three (x × y × time) dimensions. The instrumental progress makes it currently possible to generate a large amount of data in a relatively short time, which is particularly true for AFM operating in so-called PeakForce tapping mode (Bruker corporation). The latter corresponds to an AFM probe that periodically hits the sample surface while the pico-newton level interaction force is recorded from cantilever deflection. The method provides unprecedented high-resolution (a few tens of nm) imaging of the mechanical features of soft biological samples (e.g. bacteria, yeasts) and of hard abiotic surfaces (e.g. minerals). The rapid conversion of up to several tens of thousands spatially resolved force curves typically collected in AFM PeakForce tapping mode over a given cell surface area into comprehensive nanomechanical information requires the development of robust data analysis methodologies and dedicated numerical tools. In this work, we report an automated algorithm for (i) a rapid and unambiguous detection of the indentation regimes corresponding to non-linear and linear deformations of bacterial surfaces upon compression by the AFM probe, (ii) the subsequent evaluation of the Young modulus and cell surface stiffness, and (iii) the generation of spatial mappings of relevant nanomechanical properties at the single cell level. The procedure involves consistent evaluation of the contact point between the AFM probe and sample biosurface and that of the threshold indentation value marking the transition between non-linear and linear deformation regimes. For comparison purposes, the former regime is here analyzed on the basis of Hertz and Sneddon models corrected or not for effects of finite sample thickness. Analysis of AFM measurements performed on a selected Escherichia coli strain is detailed to demonstrate the feasibility, rapidity and robustness of the here-proposed PeakForce data treatment process. The flexibility of the algorithm allows consideration of force curve parameterizations other than that detailed here, which may be desired for investigation of e.g. eukaryotes nanomechanics. The performance of the adopted Hertz-based and Sneddon-based contact mechanics formalisms in recovering experimental data and in identifying nanomechanical heterogeneities at the bacterium scale is further thoroughly discussed.

A numerical method is proposed for the modeling of AFM PeakForce curves and the automated extraction of relevant spatially-resolved nanomechanical properties of turgescent cells.

Protein adsorption dynamics to polymer surfaces revisited-A multisystems approach

Performance and safety of materials in contact with living matter are determined by sequential and competitive protein adsorption. However, cause and consequences of these processes remain hard to be generalized and predicted. In a new attempt to address that challenge, the authors compared and analyzed the protein adsorption and displacement on various thoroughly characterized polymer substrates using a combination of surface-sensitive techniques. A multiple linear regression approach was applied to model the dependence of protein adsorption, desorption, and exchange dynamics on protein and surface characteristics. While the analysis confirmed that protein properties primarily govern the observed adsorption and retention phenomena and hydrophobicity as well as surface charge are the most relevant polymer surface properties, the authors have identified several protein-surface combinations that deviate from these patterns and deserve further investigation.

Hemocompatibility of Super-Repellent surfaces: Current and Future

Virtually all blood-contacting medical implants and devices initiate immunological events in the form of thrombosis and inflammation. Typically, patients receiving such implants are also given large doses of anticoagulants, which pose a high risk and a high cost to the patient. Thus, the design and development of surfaces with improved hemocompatibility and reduced dependence on anticoagulation treatments is paramount for the success of blood-contacting medical implants and devices. In the past decade, the hemocompatibility of super-repellent surfaces (i.e., surfaces that are extremely repellent to liquids) has been extensively investigated because such surfaces greatly reduce the blood-material contact area, which in turn reduces the area available for protein adsorption and blood cell or platelet adhesion, thereby offering the potential for improved hemocompatibility. In this review, we critically examine the progress made in characterizing the hemocompatibility of super-repellent surfaces, identify the unresolved challenges and highlight the opportunities for future research on developing medical implants and devices with super-repellent surfaces.

Transparent, Hydrophobic Fluorinated Ethylene Propylene Offers Rapid, Robust, and Irreversible Passive Adsorption of Diagnostic Antibodies for Sensitive Optical Biosensing

Current literature data is scarce and somehow contradictory in respect to the suitability of "nonstick" fluoropolymer surfaces for immobilization of biomolecules. We have previously shown empirically that transparent Teflon fluorinated ethylene propylene (FEP) offers rapid and sensitive optical biosensing of clinically relevant biomarkers. This study shows for the first time a comprehensive experimental analysis of passive adsorption of diagnostic IgG antibodies on actual Teflon FEP microfluidic strips. Full equilibrium isotherms and kinetics for passive adsorption were studied and modeled employing a protein titration method using hundreds of multibore microfluidic strips for a range of temperatures, pH, ionic strengths, and inner diameters, using both polyclonal and monoclonal antibody systems. Results were benchmarked against other plastic hydrophobic and glass hydrophilic capillary surfaces. For the first time, it was shown quantitatively that the hydrophobicity of fluoropolymer surfaces encourages the passive adsorption of diagnostic antibodies for biosensing and is insensitive to the temperature of incubation and to ionic buffer strength. The mass of captured antigen increased with increasing antibody surface coverage up to ∼400 ng/cm², with an optimal adsorbed antibody activity for 45-69% of full monolayer coverage, matching results of other biosensing surfaces. The equilibrium was reached fast, within 5-10 min, and surprisingly both the kinetics and equilibrium of antibody adsorption were dependent on the inner diameter of microcapillaries. This is a novel and relevant result that will generally impact on the design of miniaturized microfluidic biosensing devices. The antibody surface densities obtained with hydrophobic plastic surfaces were 2- to 4-fold lower than for a hydrophilic, glass surface, however the former presented a monolayered adsorption with a higher level of irreversibility, as shown by the adsorption and desorption rates around 1 order of magnitude smaller than for glass, which is highly desirable for biosensing with surface-coated biomolecules.

Development of label-free plasmonic Au-TiO2 thin film immunosensor devices

This work reports on the development of a label-free immunosensor technology, based on nanoplasmonic Au-TiO₂ thin films. The Au-TiO₂ thin films were prepared by cost-effective reactive DC magnetron sputtering, followed by a thermal annealing procedure. The latter promoted the growth of the Au nanoparticles throughout the TiO₂ matrix and induced some morphological changes, which are the base for the immunosensor device functionality. A posterior plasma etching treatment was required to partially expose the nanoparticles to the biological environment. It gave rise to a 6-fold increase of the total area of gold exposed, allowing further possibilities for the sensor sensitivity enhancement. Experimental results demonstrated the successful functionalization of the films' surface with antibodies, with the immobilization occurring preferentially in the exposed nanoparticles and negligibly on the TiO₂ matrix. Antibody adsorption surface coverage studies revealed antibody low affinity to the film's surface. Nevertheless, immunoassay development experiments showed a strong and active immobilized antibody monolayer at an optimized antibody concentration. This allowed a 236 signal-to-noise-ratio in a confocal microscope, using mouse IgG and 100 ng/ml of Fab-specific anti-mouse IgG-FITC conjugated. Label-free detection of the optimized antibody monolayer on Au-TiO₂ thin films was also tested, revealing an expected redshift in the LSPR band, which demonstrates the suitability for the development of cost-effective, label-free LSPR based immunosensor devices.

Norepinephrine Inhibits Alzheimer's Amyloid-β Peptide Aggregation and Destabilizes Amyloid-β Protofibrils: A Molecular Dynamics Simulation Study

The abnormal self-assembly of amyloid-β (Aβ) peptides into toxic fibrillar aggregates is associated with the pathogenesis of Alzheimer's disease (AD). The inhibition of β-sheet-rich oligomer formation is considered as the primary therapeutic strategy for AD. Previous experimental studies reported that norepinephrine (NE), one of the neurotransmitters, is able to inhibit Aβ aggregation and disaggregate the preformed fibrils. Moreover, exercise can markedly increase the level of NE. However, the underlying inhibitory and disruptive mechanisms remain elusive. In this work, we performed extensive replica-exchange molecular dynamic (REMD) simulations to investigate the conformational ensemble of Aβ_1-42 dimer with and without NE molecules. Our results show that without NE molecules, Aβ_1-42 dimer transiently adopts a β-hairpin-containing structure, and the β-strand regions of this β-hairpin (residues 15QKLVFFA21 and 33GLMVGGVV40) strongly resemble those of the Aβ fibril structure (residues 15QKLVFFA21 and 30AIIGLMVG37) reported in an electron paramagnetic resonance spectroscopy study. NE molecules greatly reduce the interpeptide β-sheet content and suppress the formation of the above-mentioned β-hairpin, leading to a more disordered coil-rich Aβ dimer. Five dominant binding sites are identified, and the central hydrophobic core 16KLVFFA21 site and C-terminal 31IIGLMV36 hydrophobic site are the two most favorable ones. Our data reveal that hydrophobic, aromatic stacking, hydrogen-bonding and cation-π interactions synergistically contribute to the binding of NE molecules to Aβ peptides. MD simulations of Aβ_1-42 protofibril show that NE molecules destabilize Aβ protofibril by forming H-bonds with residues D1, A2, D23, and A42. This work reveals the molecular mechanism by which NE molecules inhibit Aβ_1-42 aggregation and disaggregate Aβ protofibrils, providing valuable information for developing new drug candidates and exercise therapy against AD.

Intermolecular Interaction of Polymer Brushes Containing Phosphorylcholine and Inverse-Phosphorylcholine

Choline phosphate (CP) is a phosphobetaine-type zwitterionic functional group, referred to as inverse phosphorylcholine (PC) due to the reverse orientation of a positively charged quaternary amine and anionic phosphate in contrast to PC lipids in nature. The A unique dipole paring between CP and PC groups has attracted much attention in the biointerface research field. Herein, to evaluate the molecular interaction between the CP and PC groups in water, force-distance curve measurements using scanning probe microscopy (SPM) with a PC-group-functionalized cantilever was carried out on the surface of polymer brushes bearing the CP groups. Three types of methacrylate monomers bearing CP with ethyl (Et), methoxyethyl (MOE), and isopropyl (iPr) phosphates were synthesized in 42-71% yields, and polymerized by surface-initiated atom transfer radical polymerization to form polymer brushes on silicon wafers. The surface free energy of CP-polymer brushes with Et, MOE, and iPr was estimated to be 64.0, 61.4, and 57.4 mN m^-1, respectively, based on contact angle measurements. Force-distance curve measurements of polymer brushes having a CP group was conducted in water at 25 °C by SPM using a spherical probe produced by attaching a silica particle (SiP; d = 25 μm) covered with PC or CP groups to a tipless cantilever. Adhesion force larger than 14 nN was observed between the CP-polymer brushes and PC-SiP, whereas PC-polymer brushes revealed extremely low adhesion force of less than 0.6 nN with PC-SiP and propylsilane-modified SiP. The specific attractive molecular interaction between CP and PC groups was quantitatively evaluated.

Understanding how charge and hydrophobicity influence globular protein adsorption to alkanethiol and material surfaces

Globular protein adsorption to surfaces is predictable when charge and hydrophobicity is carefully controlled.

Molecular dynamics simulations of β2-microglobulin interaction with hydrophobic surfaces

Hydrophobic surfaces are known to adsorb and unfold proteins, a process that has been studied only for a few proteins. Here we address the interaction of β2-microglobulin, a paradigmatic protein for the study of amyloidogenesis, with hydrophobic surfaces. A system with 27 copies of the protein surrounded by a model cubic hydrophobic box is studied by implicit solvent molecular dynamics simulations. Most proteins adsorb on the walls of the box without major distortions in local geometry, whereas free molecules maintain proper structures and fluctuations as observed in explicit solvent molecular dynamics simulations. The major conclusions from the simulations are as follows: (i) the adopted implicit solvent model is adequate to describe protein dynamics and thermodynamics; (ii) adsorption occurs readily and is irreversible on the simulated timescale; (iii) the regions most involved in molecular encounters and stable interactions with the walls are the same as those that are important in protein-protein and protein-nanoparticle interactions; (iv) unfolding following adsorption occurs at regions found to be flexible by both experiments and simulations; (v) thermodynamic analysis suggests a very large contribution from van der Waals interactions, whereas unfavorable electrostatic interactions are not found to contribute much to adsorption energy. Surfaces with different degrees of hydrophobicity may occur in vivo. Our simulations show that adsorption is a fast and irreversible process which is accompanied by partial unfolding. The results and the thermodynamic analysis presented here are consistent with and rationalize previous experimental work.

Freely suspended perforated polymer nanomembranes for protein separations

Selective removal of nanometer-sized compounds such as proteins from fluids is an often challenging task in many scientific and industrial areas. Addressing such tasks with highly efficient and selective membranes is desirable since commonly used chromatographic approaches are expensive and difficult to scale up. Nanomembranes, molecularly thin separation layers, have been predicted and shown to possess outstanding properties but in spite ultra-fast diffusion times and high-resolution separation, to date they generally lack either of two crucial characteristics: compatibility with biological fluids and low-cost production. Here we report the fast and easy fabrication of highly crosslinked polymer membranes based on a thermoset resin (poly[(o-cresyl glycidyl ether)-co-formaldehyde (PCGF) cured with branched polyethyleneimine (PEI)) with nanoscale perforations of 25 nm diameter. During spin casting, microphase separation of a polylactide-co-glycolide induces the formation of nanometer sized domains that serve as templates for perforations which penetrate the 80 nm thick membranes. Ultrathin perforated nanomembranes can be freely suspended on the cm scale, exhibit high mechanical strength, low surface energies and a sharp permeability cutoff at a hydrodynamic diameter of 10 nm suitable for protein separations.

Osteogenic nanostructured titanium surfaces with antibacterial properties under conditions that mimic the dynamic situation in the oral cavity

The study aim was to assess the impact of different surface nanofeatures on otherwise smooth titanium surfaces on bacterial adhesion as well as on their osteogenic potential.

Conformal Coating of Co/N-Doped Carbon Layers into Mesoporous Silica for Highly Efficient Catalytic Dehydrogenation-Hydrogenation Tandem Reactions

To maximize the utilizing efficiency of cobalt (Co) and optimize its catalytic activity and stability, engineering of size and interfacial chemical properties, as well as controllable support are of ultimate importance. Here, the concept of coating uniform thin Co/N-doped carbon layers into the mesopore surfaces of mesoporous silica is proposed for heterogeneous aqueous catalysis. To approach the target, a one-step solvent-free melting-assisted coating process, i.e., heating a mixture of a cobalt salt, an amino acid (AA), and a mesoporous silica, is developed for the synthesis of mesoporous composites with thin Co/N-doped carbon layers uniformly coated within mesoporous silica, high surface areas (250-630 m² g^-1 ), ordered mesopores (7.0-8.4 nm), and high water dispersibility. The strong silica/AA adhesive interactions and AA cohesive interactions direct the uniform coating process. The metal/N coordinating, carbon anchoring, and mesopore confining lead to the formation of tiny Co nanoclusters. The carbon intercalation and N coordination optimize the interfacial properties of Co for catalysis. The optimized catalyst exhibits excellent catalytic performance for tandem hydrogenation of nitrobenzene and dehydrogenation of NaBH₄ with well-matched reaction kinetics, 100% conversion and selectivity, high turnover frequencies, up to ≈6.06 mol_nitrobenzene mol_Co^-1 min^-1 , the highest over transition-metal catalysts, and excellent stability and magnetic separability.

NanoTopoChip: High-throughput nanotopographical cell instruction

Surface topography is able to influence cell phenotype in numerous ways and offers opportunities to manipulate cells and tissues. In this work, we develop the Nano-TopoChip and study the cell instructive effects of nanoscale topographies. A combination of deep UV projection lithography and conventional lithography was used to fabricate a library of more than 1200 different defined nanotopographies. To illustrate the cell instructive effects of nanotopography, actin-RFP labeled U2OS osteosarcoma cells were cultured and imaged on the Nano-TopoChip. Automated image analysis shows that of many cell morphological parameters, cell spreading, cell orientation and actin morphology are mostly affected by the nanotopographies. Additionally, by using modeling, the changes of cell morphological parameters could by predicted by several feature shape parameters such as lateral size and spacing. This work overcomes the technological challenges of fabricating high quality defined nanoscale features on unprecedented large surface areas of a material relevant for tissue culture such as PS and the screening system is able to infer nanotopography - cell morphological parameter relationships. Our screening platform provides opportunities to identify and study the effect of nanotopography with beneficial properties for the culture of various cell types.

STATEMENT OF SIGNIFICANCE

The nanotopography of biomaterial surfaces can be modified to influence adhering cells with the aim to improve the performance of medical implants and tissue culture substrates. However, the necessary knowledge of the underlying mechanisms remains incomplete. One reason for this is the limited availability of high-resolution nanotopographies on relevant biomaterials, suitable to conduct systematic biological studies. The present study shows the fabrication of a library of nano-sized surface topographies with high fidelity. The potential of this library, called the 'NanoTopoChip' is shown in a proof of principle HTS study which demonstrates how cells are affected by nanotopographies. The large dataset, acquired by quantitative high-content imaging, allowed us to use predictive modeling to describe how feature dimensions affect cell morphology.

Organic matter interactions with natural manganese oxide and synthetic birnessite

Redox reactions of inorganic and organic contaminants on manganese oxides have been widely studied. However, these reactions are strongly affected by the presence of natural organic matter (NOM) at the surface of the manganese oxide. Interestingly, the mechanism behind NOM adsorption onto manganese oxides remains unclear. Therefore, in this study, the adsorption kinetics and equilibrium of different NOM isolates to synthetic manganese oxide (birnessite) and natural manganese oxide (Mn sand) were investigated. Natural manganese oxide is composed of both amorphous and well-crystallised Mn phases (i.e., lithiophorite, birnessite, and cryptomelane). NOM adsorption on both manganese oxides increased with decreasing pH (from pH7 to 5), in agreement with surface complexation and ligand exchange mechanisms. The presence of calcium enhanced the rate of NOM adsorption by decreasing the electrostatic repulsion between NOM and Mn sand. Also, the adsorption was limited by the diffusion of NOM macromolecules through the Mn sand pores. At equilibrium, a preferential adsorption of high molecular weight molecules enriched in aromatic moieties was observed for both the synthetic and natural manganese oxide. Hydrophobic interactions may explain the adsorption of organic matter on manganese oxides. The formation of low molecular weight UV absorbing molecules was detected with the synthetic birnessite, suggesting oxidation and reduction processes occurring during NOM adsorption. This study provides a deep insight for both environmental and engineered systems to better understand the impact of NOM adsorption on the biogeochemical cycle of manganese.

Sticky Situation: An Investigation of Robust Aqueous-Based Recombinant Spider Silk Protein Coatings and Adhesives

The mechanical properties and biocompatibility of spider silks have made them one of the most sought after and studied natural biomaterials. A biomimetic process has been developed that uses water to solvate purified recombinant spider silk proteins (rSSps) prior to material formation. The absence of harsh organic solvents increases cost effectiveness, safety, and decreases the environmental impact of these materials. This development allows for the investigation of aqueous-based rSSps as coatings and adhesives and their potential applications. In these studies it was determined that fiber-based rSSps in nonfiber formations have the capability to coat and adhere numerous substrates, whether rough, smooth, hydrophobic, or hydrophilic. Further, these materials can be functionalized for a variety of processes. Drug-eluting coatings have been made with the capacity to release a variety of compounds in addition to their inherent ability to prevent blood clotting and biofouling. Additionally, spider silk protein adhesives are strong enough to outperform some conventional glues and still display favorable tissue implantation properties. The physical properties, corresponding capabilities, and potential applications of these nonfibrous materials were characterized in this study. Mechanical properties, ease of manufacturing, biodegradability, biocompatibility, and functionality are the hallmarks of these revolutionary spider silk protein materials.

Lipidation Effect on Surface Adsorption and Associated Fibrillation of the Model Protein Insulin

Lipidation of proteins is used in the pharmaceutical field to increase the therapeutic efficacy of proteins. In this study, we investigate the effect of a 14-carbon fatty acid modification on the adsorption behavior of human insulin to a hydrophobic solid surface and the subsequent fibrillation development under highly acidic conditions and elevated temperature by comparing to the fibrillation of human insulin. At these stressed conditions, the lipid modification accelerates the rate of fibrillation in bulk solution. With the use of several complementary surface-sensitive techniques, including quartz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM), and neutron reflectivity (NR), we show that there are two levels of structurally different protein organization at a hydrophobic surface for both human insulin and the lipidated analogue: a dense protein layer formed within minutes on the surface and a diffuse outer layer of fibrillar structures which took hours to form. The two layers may only be weakly connected, and proteins from both layers are able to desorb from the surface. The lipid modification increases the protein surface coverage and the thickness of both layer organizations. Upon lipidation not only the fibrillation extent but also the morphology of the fibrillar structures changes from fibril clusters on the surface to a more homogeneous network of fibrils covering the entire hydrophobic surface.

Self-Healing Superhydrophobic Fluoropolymer Brushes as Highly Protein-Repellent Coatings

Superhydrophobic surfaces with micro/nanostructures are widely used to prevent nonspecific adsorption of commercial polymeric and/or biological materials. Herein, a self-healing superhydrophobic and highly protein-repellent fluoropolymer brush was grafted onto nanostructured silicon by surface-initiated atom transfer radical polymerization (ATRP). Both the superhydrophobicity and antifouling properties (as indicated for isolated protein solutions and for 10% blood plasma) are well repaired upon serious chemical degradation (by e.g. air plasma). This brush still maintains excellent superhydrophobicity and good antifouling properties even after 5 damage-repair cycles, which opens a new door to fabricate long-term antifouling coatings on various substrates that can be used in harsh environments.

Investigation of severe UF membrane fouling induced by three marine algal species

Reducing membrane fouling caused by seawater algal bloom is a challenge for regions of the world where most of their freshwater is produced by seawater desalination. This study aims to compare ultrafiltration (UF) fouling potential of three ubiquitous marine algal species cultures (i.e., Skeletonema costatum-SKC, Tetraselmis sp.-TET, and Hymenomonas sp.-HYM) sampled at different phases of growth. Results showed that flux reduction and irreversible fouling were more severe during the decline phase as compared to the exponential phase, for all species. SKC and TET were responsible for substantial irreversible fouling but their impact was significantly lower than HYM. The development of a transparent gel layer surrounding the cell during the HYM growth and accumulating in water is certainly responsible for the more severe observed fouling. Chemical backwash with a standard chlorine solution did not recover any membrane permeability. For TET and HYM, the Hydraulically Irreversible Fouling Index (HIFI) was correlated to their biopolymer content but this correlation is specific for each species. Solution pre-filtration through a 1.2 μm membrane proved that cells and particulate algal organic matter (p-AOM) considerably contribute to fouling, especially for HYM for which the HIFI was reduced by a factor of 82.3.