Surface hydration for antifouling and bio-adhesion

Robust Transient Semi-Glue Tape: Ultrastrong Adhesion Empowered by Water Activation and Self-Locking

In adhesive industry, tapes are renowned for their superior flexibility, repeatability, and ease of storage compared to glues. However, conventional adhesive tapes often suffer from low adhesion strength (<500 kPa). This work introduces an innovative adhesive tape composed of an amphiphilic copolymer and a hydrophobic ionic liquid, achieving an ultrahigh adhesion strength of up to 3.1 MPa on various substrates, making a record-high strength to date for tape-type adhesives. This exceptional adhesion performance is facilitated by water droplets applied at the bonding interface, transforming the adhesive surface into a glue-like property without the need for curing treatments or additional auxiliary equipment. By combining the advantageous features of both glues and tapes, these adhesives are termed as transient semi-glue tapes (TSGT). The mechanism behind such water activation and self-locking process is elucidated, and a general preparation approach is developed. Furthermore, the repeatability and recyclability of TSGT are demonstrated, offering an ingenious solution to this long-standing engineering challenge.

Cu2-xS homojunction coatings empower titanium implants with near-infrared-triggered antibacterial and antifouling properties

For decades, implant-associated infections (IAIs) caused by pathogenic bacteria have been associated with high failure and mortality rates in implantation surgeries, posing a serious threat to global public health. Therefore, developing a functionalized biomaterial coating with anti-fouling and anti-bacterial functions is crucial for alleviating implant infections. Herein, a near-infrared-responsive anti-bacterial and anti-adhesive coating (Ti-PEG-Cu2-xS) constructed on the surface of titanium (Ti) implants is reported. This coating is composed of nano-Cu2-xS with anti-bacterial activity and super-hydrophilic polyethylene glycol (PEG). Under near-infrared irradiation, the nano-catalyst Cu2-xS on the surface of Ti-PEG-Cu2-xS induces bacterial death by catalyzing the production of singlet oxygen (1O2). The Ti-PEG-Cu2-xS coating can effectively prevent bacterial adhesion and biofilm formation. This coating combines the antibacterial mechanisms of "active attack" and "passive defense", which can kill bacteria and inhibit biofilm formation. The results of in vitro and in vivo experiments have shown that Ti-PEG-Cu2-xS exhibits excellent anti-bacterial properties under near-infrared irradiation and can effectively prevent implant-related infections caused by Escherichia coli (E. coli) ATCC 8739 and Staphylococcus aureus (S. aureus). The antibacterial efficiency of Ti-PEG-Cu2-xS coatings against E. coli was 99.96% ± 0.058% and that of S. aureus was 99.66% ± 0.26%, respectively. In addition, the Ti-PEG-Cu2-xS coating has good blood compatibility and excellent bactericidal ability. Therefore, this multifunctional coating combines a non-adhesive surface strategy and a near-infrared phototherapy sterilization method, effectively blocking the initial attachment and proliferation of bacteria on implants via photothermal/photodynamic effects and providing a promising method for preventing bacterium-induced IAIs.

Eggshell membrane powder reinforces adhesive polysaccharide hydrogels for wound repair

Multifunctional polysaccharide hydrogels with strong tissue adhesion, and antimicrobial and hemostatic properties are attractive wound healing materials. In this study, a chitosan-based hydrogel (HCS) was designed, and its properties were enhanced by incorporating oxidized eggshell membrane (OEM). Hydrogel characterization and testing results showed that the hydrogel had excellent antimicrobial properties, cytocompatibility, satisfactory adhesion properties on common substrates, and wet-state adhesion capacity. A rat liver injury model confirmed the significant hemostatic effect of the hydrogel. Finally, the ability of the hydrogel to promote wound healing was verified using rat skin wound repair experiments. Our findings indicate that HCS/OEM hydrogels with added eggshell membrane fibers have better self-healing properties, mechanical strength, adhesion, hemostatic properties, and biocompatibility than HCS hydrogels, in addition to having superior repair performance in wound repair experiments. Overall, the multifunctional polysaccharide hydrogels fabricated in this study are ideal for wound repair.

Novel biomimetic macromolecules system for highly efficient lubrication, ROS scavenging and osteoarthritis treatment

The early stages of osteoarthritis (OA) in the joints are typically characterized by two key factors: the dysfunction of articular cartilage lubrication and inflammation resulting from the excessive production of reactive oxygen species (ROS). Synthetic injectable macromolecular materials present great potential for preventing the progression of early OA. In this study, to mimic the excellent lubricity of brush-like aggregates found in natural synovial fluid, we develop a novel macromolecular biolubricant (CS-PS-DA) by integrating adhesion and hydration groups onto backbone of natural biomacromolecules. CS-PS-DA exhibits a strong affinity for cartilage surfaces, enabling the formation of a stable lubrication layer at the sliding interface of degraded cartilages to restore joint lubrication performance. In vitro results from ROS scavenging and anti-inflammatory experiments indicate the great advantage of CS-PS-DA to decrease the levels of proinflammatory cytokines by inhibiting ROS overproduction. Finally, in vivo rats OA model demonstrates that intra-cavitary injection of CS-PS-DA could effectively resist cartilage wear and mitigated inflammation in the joints. This novel biolubricant provides a new and timely strategy for the treatment of OA.

Protein-Mediated Changes in Membrane Fluidity and Ordering: Insights into the Molecular Mechanism and Implications for Cellular Function

Probing protein-membrane interactions is vital for understanding biological functionality for various applications such as drug development, targeted drug delivery, and creation of functional biomaterials for medical and industrial purposes. In this study, we have investigated interaction of Human Serum Albumin (HSA) with two different lipids, dipalmitoylphosphatidylglycerol (dDPPG) and dipalmitoylphosphatidylcholine (dDPPC), using Vibrational Sum Frequency Generation spectroscopy at different membrane fluidity values. In the liquid-expanded (LE) state of the lipid, HSA (at pH 3.5) deeply intercalated lipid chains through a combination of electrostatic and hydrophobic interactions, which resulted in more ordering of the lipid chains. However, in the liquid-condensed (LC) state, protein intercalation is decreased due to tighter lipid packing. Moreover, our findings revealed distinct differences in HSA's interaction with dDPPG and dDPPC lipids. The interaction with dDPPC remained relatively weak compared to dDPPG. These results shed light on the significance of protein mediated changes in lipid characteristics, which hold considerable implications for understanding membrane protein behavior, lipid-mediated cellular processes, and lipid-based biomaterial design.

Highly efficient GPCR immobilization with enhanced fouling resistance, salt tolerance, and chromatographic performance

The feasibility of immobilized protein-based biodetection relies critically on the activity of the immobilized proteins as well as the biocompatibility of the protein surface. Although many protein immobilization strategies have been developed with satisfied detection readout signals. Non-specific interactions caused by the protein-coating surface are still of great concern since they often interfere with or affect the reliability of detection. Herein, we developed a highly efficient G protein-coupled receptor (GPCR) immobilization method by the combination of polyethylene glycol (PEG) with a self-labeling enzyme-catalyzed reaction. The immobilization relies on the covalent interaction between the fusion tag of a target GPCR (kinase domain of epidermal growth factor receptor, EGFR) and its covalent inhibitor ibrutinib, which is modified on PEGylated silica gels. Two types of GPCRs, N-methyl-D-aspartate 2 A receptor (NMDAR2A) and endothelin A receptor (ETAR), were used as examples to realize protein immobilization. The GPCR modified gels and the affinity columns packed with them have been extensively characterized, in terms of non-specific adsorptions, retention factor (k'), half peak width (W1/2), tailing factor (Tf), theoretical plates (N), and association and dissociation constants of the ligands with the receptors. The immobilized GPCRs with reduced non-specific interactions and enhanced fouling resistance, salt tolerance, and chromatographic performance were clearly observed. We believe it is the first work to introduce PEGylation in GPCR immobilization and provide comprehensive proof-of-concept studies to illustrate the improved antifouling property, salt tolerance, and chromatographic performance. This method could be generally applicable in other immobilized protein-based technology for reliable biodetection.

Novel Antifouling Coatings by Zwitterionic Silica Grafting on Glass Substrates

Zwitterionic silica coatings for surface functionalization are greatly prominent because of their simple and fast preparation, high availability, and effective antifouling properties. In this work, two zwitterionic sulfobetaine silane coatings, i.e., mono-SBSi and tris-SBSi, were deposited on glass surfaces and tested for antifouling of biological material and biofilm using human cancer cell and seawater, respectively. The used zwitterionic precursors mono-SBSi and tris-SBSi differ by the number of hydrolyzable silane groups: mono-SBSi contains one trimethoxysilane group, whereas tris-SBSi contains three of these functions. First, X-ray photoelectron spectroscopy indicates the successful grafting of zwitterionic coatings onto a glass surface. Characterization using atomic force microscopy shows the different morphologies and roughness of the two coatings. The glass surface became more hydrophilic after the grafting of zwitterionic coatings than the bare glass substrate. The antifouling properties of two coatings were evaluated via human cancer cell adsorption. Interestingly, the tris-SBSi coating displays a significantly lower level of cell adsorption compared to that of both mono-SBSi coating and the non-modified control surface. The same trend was observed for biofilm formation in seawater. Finally, the toxicity of mono-SBSi and tris-SBSi coatings was evaluated on zebrafish embryos, indicating the good biocompatibility of both coatings. Our results indicate interesting antifouling properties of zwitterionic coatings. The chemical constitution of the used precursor has an impact on the antifouling properties of the formed coating: the tris-SBSi-based zwitterionic silica coatings display improved antifouling properties compared to those of the mono-SBSi-based coating. Besides, the use of trisilylated precursors should result in the formation of more resistant and robust coatings due to the higher number of grafting functions. For all these reasons, we anticipate that tris-SBSi coatings will open new perspectives for antifouling applications for biological environments and implants.

Porous Laser-Scribed Graphene Electrodes Modified with Zwitterionic Moieties: A Strategy for Antibiofouling and Low-Impedance Interfaces

Laser-scribed graphene electrodes (LSGEs) are promising platforms for the development of electrochemical biosensors for point-of-care settings and continuous monitoring and wearable applications. However, the frequent occurrence of biofouling drastically reduces the sensitivity and selectivity of these devices, hampering their sensing performance. Herein, we describe a versatile, low-impedance, and robust antibiofouling interface based on sulfobetaine-zwitterionic moieties. The interface induces the formation of a hydration layer and exerts electrostatic repulsion, protecting the electrode surface from the nonspecific adsorption of various biofouling agents. We demonstrate through electrochemical and microscopy techniques that the modified electrode exhibits outstanding antifouling properties, preserving more than 90% of the original signal after 24 h of exposure to bovine serum albumin protein, HeLa cells, and Escherichia coli bacteria. The promising performance of this antifouling strategy suggests that it is a viable option for prolonging the lifetime of LSGEs-based sensors when operating on complex biological systems.

Diffusely Charged Polymeric Zwitterions as Loosely Hydrated Marine Antifouling Coatings

Polymeric zwitterions exhibit exceptional fouling resistance through the formation of a strongly hydrated surface of immobilized water molecules. While being extensively tested for their performance in biomedical, membrane, and, to a lesser extent, marine environments, few studies have investigated how the molecular design of the zwitterion may enhance its performance. Furthermore, while theories of zwitterion antifouling mechanisms exist for molecular-scale foulant species (e.g., proteins and small molecules), it remains unclear how molecular-scale mechanisms influence the micro- and macroscopic interactions of relevance for marine applications. The present study addresses these gaps through the use of a modular zwitterion chemistry platform, which is characterized by a combination of surface-sensitive sum frequency generation (SFG) vibrational spectroscopy and marine assays. Zwitterions with increasingly delocalized cations demonstrate improved fouling resistance against the green alga Ulva linza. SFG spectra correlate well with the assay results, suggesting that the more diffuse charges exhibit greater surface hydration with more bound water molecules. Hence, the number of bound interfacial water molecules appears to be more influential in determining the marine antifouling activities of zwitterionic polymers than the binding strength of individual water molecules at the interface.

Relationships between Water's Structure and Solute Affinity at Polypeptoid Brush Surfaces

Excellent antifouling surfaces are generally thought to create a tightly bound layer of water that resists solute adsorption, and highly hydrophilic surfaces such as those with zwitterionic functionalities are of significant current interest as antifoulant strategies. However, despite significant proofs-of-concept, we still lack a fundamental understanding of how the nanoscopic structure of this hydration layer translates to reduced fouling, how surface chemistry can be tuned to achieve antifouling through hydration water, and why, in particular, zwitterionic surfaces seem so promising. Here, we use molecular dynamics simulations and free energy calculations to investigate the molecular relationships among surface chemistry, hydration water structure, and surface-solute affinity across a variety of surface-decorated chemistries. Specifically, we consider polypeptoid-decorated surfaces that display well-known experimental antifouling capabilities and that can be synthesized sequence specifically, with precise backbone positioning of, e.g., charged groups. Through simulations, we calculate the affinities of a range of small solutes to polypeptoid brush surfaces of varied side-chain chemistries. We then demonstrate that measures of the structure of surface hydration water in response to a particular surface chemistry signal solute-surface affinity; specifically, we find that zwitterionic chemistries produce solute-surface repulsion through highly coordinated hydration water while suppressing tetrahedral structuring around the solute, in contrast to uncharged surfaces that show solute-surface affinity. Based on the relationship of this structural perturbation to the affinity of small-molecule solutes, we propose a molecular mechanism by which zwitterionic surface chemistries enhance solute repulsion, with broader implications for the design of antifouling surfaces.

Antioxidant N-acetylcysteine removing ROS: an antifouling strategy inspired by mussels

Marine biofouling is a thorny issue that causes serious economic losses and adverse ecological impacts on marine ecosystems. Effective and promising antifouling strategies such as surface hydration, flow shear force, and lubricant injection have been developed to address this challenge. However, for the complex marine environment, they still appear inadequate. Mussels are a common fouling organism with strong surface adhesion ability. However, when hypoxia and the oxidative cross-linking reaction of 3,4-dihydroxy phenyl-L-alanine (DOPA) in the structure of adhesion proteins are disrupted, their adhesion ability will be greatly reduced. Inspired by this, we developed an effective antifouling strategy based on reactive oxygen species (ROS) scavenging using N-acetylcysteine (NAC) and evaluated its performance. As a ROS scavenger interfered with the oxidative cross-linking reaction of DOPA in an aqueous solution, the adhesion of DOPA was also affected on the surface of NAC functionalized polyvinyl chloride (PVC) (PVC-NAC). In addition, the colonization level of mussels and the adhesion rate of marine bacteria and benthic diatoms on PVC-NAC were low. The antifouling strategy proposed in this paper was eco-friendly and broad-spectrum, and may provide a new idea for solving marine biofouling and reducing the environmental and economic impacts of fouling organisms.

Interfacial Water-Dictated Oil Adhesion Based on Ion Modulation

Oil adhesion on ionic surfaces is ubiquitous in organisms and natural environments and is generally determined by surface chemical component and texture. However, when adhesion occurs, water molecules at the solid-liquid interface, acting as a bridge not only influenced by the structure and composition of the solid surface but also interacting with the neighboring oil molecules, play a crucial role but are always overlooked. Herein, we investigate the oil adhesion process on a carboxyl-terminated self-assembled monolayer surface (COOH-SAM) in ionic solutions and observe the interfacial water structure via surface-enhanced Raman scattering (SERS) in this system. It is found that the lower the tetracoordinated water content, the stronger the oil adhesion. Compared to monovalent ions, the strengthened binding of multivalent ions to the COOH-SAM surface makes the interfacial water more disordered, which eventually leads to a stronger oil adhesion. Notably, the amount of oil adhesion decreases with an increase in the thickness of the interfacial water region. The interfacial water-dictated oil adhesion has been demonstrated in capillary to simulate the water-driven oil recovery, providing a molecular-level explanation for enhanced oil recovery from low salinity water flooding and also indicating potential applications in intelligent microfluidic and seawater desalination.

Zwitterionic Polymeric Sulfur Ylides with Minimal Charge Separation Open a New Generation of Antifouling and Bactericidal Materials

Zwitterionic polymers are widely employed hydrophilic building blocks for antifouling coatings with numerous applications across a wide range of fields, including but not limited to biomedical science, drug delivery and nanotechnology. Zwitterionic polymers are considered as an attractive alternative to polyethylene glycol because of their biocompatibility and effectiveness to prevent formation of biofilms. To this end, zwitterionic polymers are classified in two categories, namely polybetaines and polyampholytes. Yet, despite a fundamental interest to drive the development of new antifouling materials, the chemical composition of zwitterionic polymer remains severely limited. Here, we show that poly(sulfur ylides) that belong to the largely overlooked class of poly(ylides), effectively prevent the formation of biofilms from pathogenic bacteria. While surface energy analysis reveals strong hydrogen-bond acceptor capabilities of poly(sulfur ylide), membrane damage of pathogenic bacteria induced by poly(sulfur ylides) indicates toxicity towards bacteria while not affecting eucaryotic cells. Such synergistic effect of poly(sulfur ylides) offers distinct advantages over polyethylene glycol when designing new antifouling materials. We expect that our findings will pave the way for the development of a range of ylide-based materials with antifouling properties that have yet to be explored, opening up new directions at the interface of chemistry, biology, and material science.

Antifouling polymers for nanomedicine and surfaces: recent advances

Antifouling polymers are materials that can resist nonspecific interactions with cells, proteins, and other biomolecules. Typically, they are hydrophilic polymers with polar or charged moieties that are capable of strong nonbonding interactions with water molecules. This propensity to bind water generates a surface hydration layer that reduces nonspecific interactions with other molecules and is paramount to the antifouling behavior. This property is especially useful for nanoscale applications such as nanomedicine and surface modifications at the molecular level. In nanomedicine, antifouling polymers such as poly(ethylene glycol) and its alternatives play a key role in shielding drug molecules and therapeutic proteins/genes from the immune system within nanoassemblies, thereby enabling effective delivery to target tissues. For coatings, antifouling polymers help to prevent adhesion of cells and molecules to surfaces and are thus valued in marine and biomedical device applications. In this Review, we survey recent advances in antifouling polymers in the context of nanomedicine and coatings, while shining the spotlight on the major polymer classes such as PEG, polyzwitterions, poly(oxazoline)s, and other nonionic hydrophilic polymers.

Thin continuous membrane coating with high surface energy for comprehensive antifouling seawater distillation

Membrane distillation (MD) has prominent advantages such as treating high-salinity wastewater with a low-grade thermal energy, high salt rejection, and zero discharge. However, organic fouling and mineral scaling are two major challenges for hydrophobic MD membranes when used for practical applications. Commonly, improving organic fouling- and mineral scaling-resistance require oppositely enhanced wetting properties of membrane, thus is difficult to simultaneously realize dual resistance with one membrane. Here, we proposed to use underwater thermodynamically stable high-surface-energy coating to modify the hydrophobic membrane with Janus structures comprising different surface energy. The underlayered structure meets the hydrophobicity requirements of the MD membrane, while the coating layer realizes dual resistance to organic and inorganic foulants. Theoretical analysis and experimental proof reveal that the membrane with the high-surface-energy coating layer outperforms the pristine one with approximately 10 times of longevity. This strategy provides a new way for the use of high-surface-energy materials in versatilely fouling-resistant MD process.

Supramolecular Self-Healing Antifouling Coating for Dental Materials

In orthodontic treatment, orthodontic appliances are prone to bacterial infections, which pose a risk to oral health. Surface modification of orthodontic appliances has been explored to improve their antifouling properties and impart antibacterial capabilities, inhibiting initial bacterial adhesion and biofilm formation. However, coatings are susceptible to damage in the complex oral environment, leading to a loss of functionality. Here, we have prepared an antifouling self-healing coating based on supramolecular bonding by employing a simple spin coating method. The presence of the hydrophilic zwitterionic trimethylamine N-oxide (TMAO) and the hydrophobic antimicrobial moieties triclosan acrylate (TCSA) imparts to the polymers an amphiphilic structure and enhances the interaction with bacteria, resulting in excellent antimicrobial activity and surface antifouling properties. The multiple hydrogen bonds of ureido-pyrimidinone methacrylate (UPyMA) and ionic interactions contained in the polymers not only increased the adhesion of the coating to the material substrate (approximately 3 times) but also endowed the coating with the intrinsic self-healing ability to restore the antibiofouling properties at oral temperature and humidity. Finally, the polymer coating is biologically safe both in vitro and in vivo, showing no cytotoxic effects on cells and tissues. This research offers a promising avenue for improving the performance of orthodontic appliances and contributes to the maintenance and treatment of oral health.

Electrostatic and Covalent Binding of an Antibacterial Polymer to Hydroxyapatite for Protection against Escherichia coli Colonization

Orthopedic-device-related infections are notorious for causing physical and psychological trauma to patients suffering from them. Traditional methods of treating these infections have relied heavily on antibiotics and are becoming ineffectual due to the rise of antibiotic-resistant bacteria. Mimics of antimicrobial peptides have emerged as exciting alternatives due to their favorable antibacterial properties and lack of propensity for generating resistant bacteria. In this study, the efficacy of an antibacterial polymer as a coating material for hydroxyapatite and glass surfaces, two materials with wide ranging application in orthopedics and the biomedical sciences, is demonstrated. Both physical and covalent modes of attachment of the polymer to these materials were explored. Polymer attachment to the material surfaces was confirmed via X-ray photoelectron spectroscopy and contact angle measurements. The modified surfaces exhibited significant antibacterial activity against the Gram-negative bacterium E. coli, and the activity was retained for a prolonged period on the surfaces of the covalently modified materials.

Surface hydrolysis-anchored eugenol self-polishing marine antifouling coating

Traditional self-polishing antifouling coatings kill surface organisms by releasing toxic substances, which are damaging to the ecosystem. As a natural antimicrobial substance, eugenol is environmentally friendly and has been proven by different research teams to be effective in enhancing the anti-fouling effect of coatings in the real sea. While in these previous research works, the eugenol was released directly into the seawater thus cannot further serve as surface antifouling effect, leading to a limited antifouling effect of the coating. In this work, the quaternary ammonium component was introduced into the butyl ester-based resin - poly (eugenol methacrylate - acryloyloxyethyltrimethyl ammonium chloride - hexafluorobutyl methacrylate - methyl methacrylate - butyl methacrylate - ethylene glycol methyl ether acrylate) (EMQFP) coating for the first time by simple one-step free radical polymerization method. On the one hand, the eugenol produced by hydrolysis is anchored to the quaternary ammonium on the coating surface for a period of time due to the cationic-π interaction, instead of being released into seawater immediately after hydrolysis, thus increasing the utilization rate of eugenol; on the other hand, the negatively charged carboxylate groups generated after hydrolysis in the coating are mutually attracted to quaternary ammonium through electrostatic effect, so the resin chain segment conformation on the coating surface adjusted to produce zwitterionic-like structure, and the hydration of zwitterionic inhibits primary fouling adhesion.

Probing Interfacial Behavior and Antifouling Activity of Adsorbed Copolymers at Solid/Liquid Interfaces

Polymers containing poly(ethylene glycol) (PEG) units can exhibit excellent antifouling properties, which have been proposed/used for coating of biomedical implants, separation membranes, and structures in marine environments, as well as active ingredients in detergent formulations to avoid soil redepositioning in textile laundry. This study aimed to elucidate the molecular behavior of a copolymer poly(MMA-co-MPEGMA) containing antiadhesive PEG side chains and a backbone of poly(methyl methacrylate), at a buried polymer/solution interface. Polyethylene terephthalate (PET) was used as a substrate to model polyester textile surfaces. Sum frequency generation (SFG) vibrational spectroscopy was applied to examine the interfacial behavior of the copolymer at PET/solution interfaces in situ and in real time. Complementarily, copolymer adsorption on PET and subsequent antiadhesion against protein foulants were probed by quartz-crystal microbalance experiments with dissipation monitoring (QCM-D). Both applied techniques show that poly(MMA-co-MPEGMA) adsorbs significantly to the PET/solution interface at bulk polymer solution concentrations as low as 2 ppm, while saturation of the surface was reached at 20 ppm. The hydrophobic MMA segments provide an anchor for the copolymer to bind onto PET in an ordered way, while the pendant PEG segments are more disordered but contain ordered interfacial water. In the presence of considerable amounts of dissolved surfactants, poly(MMA-co-MPEGMA) could still effectively adsorb on the PET surface and remained stable at the surface upon washing with hot and cold water or surfactant solution. In addition, it was found that adsorbed poly(MMA-co-MPEGMA) provided the PET surface with antiadhesive properties and could prevent protein deposition, highlighting the superior surface affinity and antifouling performance of the copolymer. The results obtained in this work demonstrate that amphiphilic copolymers containing PMMA anchors and PEG side chains can be used in detergent formulations to modify polyester surfaces during laundry and reduce deposition of proteins (and likely also other soils) on the textile.

Probing the behavior and kinetic studies of amphiphilic acrylate copolymers with bovine serum albumin

This article presents that acrylate copolymers are the potential candidate against the adsorption of bovine serum albumin (BSA). A series of copolymers poly(methyl methacrylate) (pMMA), poly(3-sulfopropyl methacrylate-co-methyl methacrylate) p(SPMA-co-MMA), and poly(dimethylaminoethyl methacrylate-co-methyl methacrylate) p(DMAEMA-co-MMA) were synthesized via free radical polymerization. These amphiphilic copolymers are thermally stable with a glass transition temperature (Tg) 50-120 °C and observed the impact of surface charge on amphiphilic copolymers to control interactions with the bovine serum albumin (BSA). These copolymers pMD1 and pMS1 have surface charges, - 56.6 and - 72.6 mV at pH 7.4 in PBS buffer solution that controls the adsorption capacity of bovine serum albumin (BSA) on polymers surface. Atomic force microscopy (AFM) analysis showed minimum roughness of 0.324 nm and 0.474 nm for pMS1 and pMD1. Kinetic studies for BSA adsorption on these amphiphilic copolymers showed the best fitting of the pseudo-first-order model that showed physisorption and attained at 25 °C and pH 7.4 within 24 h.

Determination of protein conformation and orientation at buried solid/liquid interfaces

Protein structures at solid/liquid interfaces mediate interfacial protein functions, which are important for many applications. It is difficult to probe interfacial protein structures at buried solid/liquid interfaces in situ at the molecular level. Here, a systematic methodology to determine protein molecular structures (orientation and conformation) at buried solid/liquid interfaces in situ was successfully developed with a combined approach using a nonlinear optical spectroscopic technique - sum frequency generation (SFG) vibrational spectroscopy, isotope labeling, spectra calculation, and computer simulation. With this approach, molecular structures of protein GB1 and its mutant (with two amino acids mutated) were investigated at the polymer/solution interface. Markedly different orientations and similar (but not identical) conformations of the wild-type protein GB1 and its mutant at the interface were detected, due to the varied molecular interfacial interactions. This systematic strategy is general and can be widely used to elucidate protein structures at buried interfaces in situ.

Polyacrylic acid/polyethylene glycol hybrid antifouling interface for photoelectrochemical immunosensing of NSE based on ZnO/CdSe

In this paper, a novel photoelectrochemical (PEC) immunosensor based on ZnO/CdSe semiconductor composite material was constructed to detect neuron-specific enolase (NSE) in a super-sensitive and quantitative way. The antifouling interface composed of polyacrylic acid (PAA) and polyethylene glycol (PEG) can prevent non-specific proteins from adhering to the electrode surface. As an electron donor, ascorbic acid (AA) can increase the photocurrent's stability and intensity by clearing away photogenerated holes. Because of the specific recognition between antigen and antibody, the quantitative detection of NSE can be achieved. The PEC antifouling immunosensor based on ZnO/CdSe has a wide linear range (0.10 pg mL^-1-100 ng mL^-1) and a low detection limit (34 fg mL^-1), which has potential application in the clinical diagnosis of small cell lung cancer.

Fouling Resistance and Release Properties of Poly(sulfobetaine) Brushes with Varying Alkyl Chain Spacer Lengths and Molecular Weights

We examined the effects of alkyl carbon spacer length (CSL) and molecular weight on fouling resistance and release properties of zwitterionic poly(sulfobetaine methacrylate) brushes. Using surface-initiated atom transfer radical polymerization, we synthesized two series of brushes with CSL = 3 and 4 and molecular weight from 19 to 1500 kg ·mol^-1, corresponding to dry brush thickness from around 6 to 180 nm. The brush with CSL = 3 was nearly completely wet with water (independent of molecular weight), whereas the brush with CSL = 4 exhibited a strong increase in water contact angle with molecular weight. Though the two-brush series had distinct wetting properties, both series of brushes exhibited similarly great resistance against fouling by Staphylococcus epidermidis bacteria and Aspergillus niger fungi spores when submerged in water, indicating that neither molecular weight nor CSL strongly affected the antifouling behavior. We also compared the efficacy of brushes against fouling by fungi and silicon oil in air. Brushes grafted to filter paper were strongly fouled by fungi and silicon oil in air. Grafting the polymers to the filter paper, however, greatly enhanced removal of the foulant upon rinsing. The removal of fungi and silicon oil when rinsed with a salt solution was enhanced by 219 and 175%, respectively, as compared to a blank filter paper control. Thus, our results indicate that these zwitterionic brushes can promote foulant removal for dry applications in addition to their well-known fouling resistance in submerged conditions.

Zwitterionic Biomaterials

The term "zwitterionic polymers" refers to polymers that bear a pair of oppositely charged groups in their repeating units. When these oppositely charged groups are equally distributed at the molecular level, the molecules exhibit an overall neutral charge with a strong hydration effect via ionic solvation. The strong hydration effect constitutes the foundation of a series of exceptional properties of zwitterionic materials, including resistance to protein adsorption, lubrication at interfaces, promotion of protein stabilities, antifreezing in solutions, etc. As a result, zwitterionic materials have drawn great attention in biomedical and engineering applications in recent years. In this review, we give a comprehensive and panoramic overview of zwitterionic materials, covering the fundamentals of hydration and nonfouling behaviors, different types of zwitterionic surfaces and polymers, and their biomedical applications.

Escherichia coli Biofilm Formation, Motion and Protein Patterns on Hyaluronic Acid and Polydimethylsiloxane Depend on Surface Stiffness

The surface stiffness of the microenvironment is a mechanical signal regulating biofilm growth without the risks associated with the use of bioactive agents. However, the mechanisms determining the expansion or prevention of biofilm growth on soft and stiff substrates are largely unknown. To answer this question, we used PDMS (polydimethylsiloxane, 9-574 kPa) and HA (hyaluronic acid gels, 44 Pa-2 kPa) differing in their hydration. We showed that the softest HA inhibited Escherichia coli biofilm growth, while the stiffest PDMS activated it. The bacterial mechanical environment significantly regulated the MscS mechanosensitive channel in higher abundance on the least colonized HA-44Pa, while Type-1 pili (FimA) showed regulation in higher abundance on the most colonized PDMS-9kPa. Type-1 pili regulated the free motion (the capacity of bacteria to move far from their initial position) necessary for biofilm growth independent of the substrate surface stiffness. In contrast, the total length travelled by the bacteria (diffusion coefficient) varied positively with the surface stiffness but not with the biofilm growth. The softest, hydrated HA, the least colonized surface, revealed the least diffusive and the least free-moving bacteria. Finally, this shows that customizing the surface elasticity and hydration, together, is an efficient means of affecting the bacteria's mobility and attachment to the surface and thus designing biomedical surfaces to prevent biofilm growth.

Antifouling and Antibacterial Surfaces Grafted with Sulfur-Containing Copolymers

Antifouling and antibacterial surfaces that can prevent nonspecific biological adhesion are important to support a myriad of biomedical applications. In this study, we have used an innovative photopolymerization technology to develop sulfur-containing polymer-grafted antifouling and antibacterial surfaces. The relationship between the hydrophilic property and the capability to resist protein and macrophage adsorption of the surface copolymer brushes was investigated. The sulfide monomer incorporated into the surface copolymer brushes can be further ionized to carry positive charges and impart antibacterial activity, leading to surfaces with dual antifouling and antibacterial functions. We believe that the reported sulfur-containing polymer brushes can be considered an emerging and important polymer for antifouling and antibacterial applications.

Biomimetic materials based on zwitterionic polymers toward human-friendly medical devices

This review summarizes recent research on the design of polymer material systems based on biomimetic concepts and reports on the medical devices that implement these systems. Biomolecules such as proteins, nucleic acids, and phospholipids, present in living organisms, play important roles in biological activities. These molecules are characterized by heterogenic nature with hydrophilicity and hydrophobicity, and a balance of positive and negative charges, which provide unique reaction fields, interfaces, and functionality. Incorporating these molecules into artificial systems is expected to advance material science considerably. This approach to material design is exceptionally practical for medical devices that are in contact with living organisms. Here, it is focused on zwitterionic polymers with intramolecularly balanced charges and introduce examples of their applications in medical devices. Their unique properties make these polymers potential surface modification materials to enhance the performance and safety of conventional medical devices. This review discusses these devices; moreover, new surface technologies have been summarized for developing human-friendly medical devices using zwitterionic polymers in the cardiovascular, cerebrovascular, orthopedic, and ophthalmology fields.

Precise Fabrication of Porous Microspheres by Iso-Density Emulsion Combined with Microfluidics

Polymer porous microspheres with large specific surface areas and good fluidity have promising important applications in the biomedical field. However, controllable fabrication of porous microspheres with precise size, morphology, and pore structure is still a challenge, and phase separation caused by the instability of the emulsion is the main factor affecting the precise preparation of porous microspheres. Herein, a method combining the iso-density emulsion (IDE) template and microfluidics was proposed to realize the controllable preparation of polymer porous microspheres. The IDE exhibited excellent stability with minimal phase separation within 4 h, thus showing potential advantages in the large-scale preparation of porous microspheres. With the IDE template combined microfluidics technique and the use of a customized amphoteric copolymer, PEG-b-polycaprolactone, polycaprolactone (PCL) porous microspheres with porosity higher than 90% were successfully prepared. Afterwards, the main factors, including polymer concentration, water–oil ratio and homogenization time were investigated to regulate the pore structure of microspheres, and microspheres with different pore sizes (1–30 μm) were obtained. PCL porous microspheres exhibited comparable cell viability relative to the control group and good potential as cell microcarriers after surface modification with polydopamine. The modified PCL porous microspheres implanted subcutaneously in rats underwent rapid in vivo degradation and tissue ingrowth. Overall, this study demonstrated an efficient strategy for the precise preparation of porous microspheres and investigated the potential of the as-prepared PCL porous microspheres as cell microcarriers and micro-scaffolds.

Development of an Ultrasmall and Biocompatible Platinum Nanozyme Encapsulated by Zwitterionic Dendrimer for Highly Sensitive Detection of Glucose

Many kinds of noble metal nanoparticles can mimic the peroxidase-like function of horseradish peroxidase, which results in their wide applications in bio-related detection and drug delivery. However, those metal nanoparticles usually have low stability and reduced catalytic activity in biological complex medium. Herein, a zwitterionic peroxidase-like enzyme has been developed, which has high stability in fibrinogen solutions and high sensitivity for glucose detection. Maleic anhydride, cysteamine, and zwitterionic peptide EKEKC (EK-5) were used to modify generation 5 poly(amido amine) dendrimers (G5 PAMAM) to prepare zwitterionic dendrimer G5MEKnC with nonfouling properties. Finally, the G5MEKnC-encapsulated platinum nanoparticles (Pt_n-G5MEK50C) were prepared by entrapping the platinum nanoparticles (1.40 nm) in the catalytic centers in the interior of G5MEK50C. Pt₅₅-G5MEK50C showed high stability in the buffer solution and the fibrinogen solution within 4 days. They also displayed high biocompatibility toward HeLa cells based on cytotoxicity results and morphological observations. Furthermore, the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine with H₂O₂ by Pt₅₅-G5MEK50C followed the Michaelis-Menten equation, which confirmed their peroxidase-like properties. The catalytic mechanism was due to the generation of ^•OH from H₂O₂. More importantly, the peroxidase-like ability of Pt₅₅-G5MEK50C was successfully used to establish a method for the determination of glucose concentration with a broad linear range of 1-2000 μM and a low detection limit of 0.1 μM. This method was highly accurate for the determination of glucose concentration in plasma. The zwitterionic dendrimer template enhanced the properties of Pt₅₅-G5MEK50C. Taken together, a new kind of biocompatible nanozyme has been developed and successfully used for the sensitive detection of glucose in bio-related medium.

Surface Hydration and Antifouling Activity of Zwitterionic Polymers

It is believed that the strong surface hydration of zwitterionic polymers leads to excellent antifouling properties. This Perspective presents the recent developments in studies on such surface hydration in situ using sum frequency generation (SFG) vibrational spectroscopy. SFG research provides direct molecular level evidence that zwitterionic polymers have strong surface hydration, which prevents protein adsorption and marine animal attachment. The salt effect and protein interaction on surface hydration of zwitterionic polymers have also been examined using SFG. Possible future research directions on surface hydration of new zwitterionic polymers including zwitterionic hydrogels, copolymers, and mixed charged polymers are discussed. It is also important to combine experimental SFG studies with computer simulations to further elucidate the surface hydration to understand antifouling mechanisms.

Composite Polyelectrolyte Photothermal Hydrogel with Anti-biofouling and Antibacterial Properties for the Real-World Application of Solar Steam Generation

Solar steam generation provides a promising and low-cost solution for freshwater production in energy scarcity areas. However, in real-world applications, evaporators are easily affected by microorganism contamination in source water, causing surface corrosion, structural damage, or even invalidation. Developing anti-biofouling and antibacterial evaporators is significant for long-term stable freshwater production. Herein, a composite polyelectrolyte photothermal hydrogel consisting of sulfobetaine methacrylate (SBMA), [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC), and polypyrrole (PPy) with anti-biofouling and antibacterial properties is developed. Crediting sufficient ammonium groups and zwitterionic segments, the optimized polyelectrolyte hydrogel exhibits an ∼90% antibacterial ratio against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and effectively controls biological contamination. Under 1.0 kW m^-2 solar irradiation, a rapid water evaporation rate of ∼1.690 kg m^-2 h^-1 and a high solar-to-evaporation efficiency of ∼95.94% are achieved with the photothermal hydrogel. We show that a lab-made setup integrated with the hydrogel can realize ∼0.455 kg m^-2 h^-1 freshwater production from seawater under natural sunlight. Moreover, the hydrogel exhibits excellent durability with a stable evaporation rate of ∼1.617 kg m^-2 h^-1 in real seawater for over 6 weeks, making it fullhearted in the real-world application of solar steam generation.

Preparation and characterization of photopolymerized poly(l-lactide-co-ε-caprolactone-co-N-vinyl-2-pyrrolidone) network as anti-biofouling materials

The anti-biofouling properties have important applications in the medical field. In this study, cross-linked networks were prepared by photopolymerizing two synthetic macromonomers, including fumaric acid monoethyl ester (FAME) functionalized, three-armed poly(l-lactide) prepolymers (3-PLLA-F) and poly(ε-caprolactone) prepolymers (2-PCL-F), with N-vinyl-2-pyrrolidone (NVP) as the diluent. The prepared networks were characterized by their thermal properties, mechanical properties, cytotoxicity experiments and anti-biofouling properties. The Young's modulus and tensile strength of networks decreased by increasing PCL content. In contrast, the elongation of networks significantly increased. Moreover, no obvious cytotoxicity was observed, and the adhesion of L929 fibroblasts and platelets was resisted. Combined with Digital Light Processing technology (DLP) in the future, the designed polymer network could potentially be commercial in the field of biological anti-fouling materials.

The poly(l-lactide-co-ε-caprolactone-co-N-vinyl-2-pyrrolidone) network formed by UV curing could resist the adhesion of L929 fibroblasts, platelets and bacteria. It could be used in the field of customized biomaterials with biological anti-fouling.

Processes of molecular adsorption and ordering enhanced by mechanical stimuli under high contact pressure

Adsorbed molecular films, referred to as boundary films in tribology, are widely used in various industrial products as a keyway for surface functionalisation, such as lubricity, wettability, and adhesion. Because boundary films are thin nanometre-scale molecular layers and can easily be removed, their formation process cannot be elucidated in detail. In this study, to analyse the growth dynamics of boundary films, the film thickness and molecular orientation of the boundary film of a fatty acid used as an additive in rolling contact as mechanical stimuli were measured in situ. The measurements were performed on simple test lubricants, which were composed of n-hexadecane and stearic acid, at rolling tribological condition between steel and glass (or sapphire) surfaces by ultrathin film interferometry combined with sum-frequency generation spectroscopy according to a unique protocol. The results quantitatively demonstrate shear-induced boundary film formation. The insight gained from these results is anticipated to enable the formulation of high-performance lubricant additives to further reduce friction loss and high-performance glues that can be freely designed for removability.

Amino acid-mediated negatively charged surface improve antifouling and tribological characteristics for medical applications

To prevent infections associated with biomedical catheters, various antimicrobial coatings have been investigated. However, those materials do not provide consistent antibacterial effects or biocompatibility, generally, due to degradation of the coating materials, in vivo. Additionally, biomedical catheters must have low surface friction to reduce tribological damage. In this study, we developed an antifouling surface composed of biocompatible amino acids (leucine, taurine, and aspartic acid) on polyimide, via modification using a series of facile immersion steps with waterborne reactions. The naturally derived amino acid could be formed highly biostable amide bonds on the polyimide surface like peptides. The amino acid-modified surface formed a water layer with antifouling performance through the hydrophilic properties of amino acids. Amino acid-mediated modification reduced adhesion up to 84.45% and 94.81% against Escherichia coli and Staphylococcus epidermidis, respectively, and exhibited an excellent prevention to adhesion against the proteins, albumin and fibrinogen. Evaluation of the surface friction of the catheter revealed a dramatic reduction in the tribological force after amino acid modification on polyimide that of 0.81 N to aspartic acid of 0.44 N. These results clearly demonstrate a reduced occurrence of infections, thrombi and tribological damage following the relatively facile surface modification of catheters. The proposed modification method can be used in a continuous manufacturing process via using the same time of modification steps for the easy producing the product. Moreover, the method uses biocompatible naturally derived materials and can be applied to medical equipment that requires biocompatibility and biofunctionality with polyimide surfaces.

Probing protein aggregation at buried interfaces: distinguishing between adsorbed protein monomers, dimers, and a monomer-dimer mixture in situ

Protein adsorption on surfaces greatly impacts many applications such as biomedical materials, anti-biofouling coatings, bio-separation membranes, biosensors, antibody protein drugs etc. For example, protein drug adsorption on the widely used lubricant silicone oil surface may induce protein aggregation and thus affect the protein drug efficacy. It is therefore important to investigate the molecular behavior of proteins at the silicone oil/solution interface. Such an interfacial study is challenging because the targeted interface is buried. By using sum frequency generation vibrational spectroscopy (SFG) with Hamiltonian local mode approximation method analysis, we studied protein adsorption at the silicone oil/protein solution interface in situ in real time, using bovine serum albumin (BSA) as a model. The results showed that the interface was mainly covered by BSA dimers. The deduced BSA dimer orientation on the silicone oil surface from the SFG study can be explained by the surface distribution of certain amino acids. To confirm the BSA dimer adsorption, we treated adsorbed BSA dimer molecules with dithiothreitol (DTT) to dissociate these dimers. SFG studies on adsorbed BSA after the DTT treatment indicated that the silicone oil surface is covered by BSA dimers and BSA monomers in an approximate 6 : 4 ratio. That is to say, about 25% of the adsorbed BSA dimers were converted to monomers after the DTT treatment. Extensive research has been reported in the literature to determine adsorbed protein dimer formation using ex situ experiments, e.g., by washing off the adsorbed proteins from the surface then analyzing the washed-off proteins, which may induce substantial errors in the washing process. Dimerization is a crucial initial step for protein aggregation. This research developed a new methodology to investigate protein aggregation at a solid/liquid (or liquid/liquid) interface in situ in real time using BSA dimer as an example, which will greatly impact many research fields and applications involving interfacial biological molecules.

Water- and Acid-Sensitive Cu2O@Cu-MOF Nano Sustained-Release Capsules with Superior Antifouling Behaviors

Marine biofouling is one of the technical bottlenecks restricting the development of the global marine economy. Among the commercial self-polishing antifouling coatings, cuprous oxide is an irreplaceable component because of its efficiency and broad-spectrum antibacterial activity. However, one of the biggest obstacles to achieving long-term antifouling is the "initial burst and final decay" of cuprous oxide in the coating. Here, we lock the copper ions by establishing an antifouling unit composed of Cu₂O (core) and Cu-based metal-organic framework (Cu-MOF, shell). Cu-MOF is densely grown in situ on the periphery of Cu₂O by acid proton etching. The shell structure of Cu-MOF can effectively improve the stability of the internal Cu₂O and thus achieve the stable and slow release of copper ions. Furthermore, Cu₂O@Cu-MOF nanocapsules can also achieve active defense by rapid and complete dissolution of Cu₂O@Cu-MOF at local acidic microenvironment (pH ≤ 5) where the adhesion of fouling organisms occurs. Super-resolution fluorescence microscopy is used to explain the sterilization mechanism. Relying on the water- and acid-sensitive properties of Cu-MOF shell, the stable, controlled and efficient release of copper ions has been achieved for the Cu₂O@Cu-MOF nanocapsules in the self-polishing antifouling coatings. Thus, these controlled-release nanocapsules make long-term antifouling promising.

Molecular Simulations of Zwitterlation-induced Conformation and Dynamics Variation of Glucagon-like Peptide-1 and Insulin

Zwitterionic materials have shown their ability to improve the circulation time and stability of proteins. Zwitterionic peptides present unique potential because genetic technology can fuse them to any wild-type protein....

Lectin-Functionalized Polyethylene Glycol for Relief of Mucosal Dryness

The importance of lubrication between oral surfaces provided by the salivary film is most acutely apparent when it is disrupted, a prevalent consequence of salivary gland hypofunction experienced with aging, a symptom of certain diseases, or a side effect of some medical interventions. Sufferers report difficulty with speech and oral food processing and collectively is detrimental to quality of life. Polyethylene glycol (PEG) is widely employed as a successful biocompatible boundary lubricant in engineering and biomedical applications. It is hypothesized that the immobilization of PEG to biological materials such as oral epithelial cells and tissue can mimic the salivary film and provide durable relief from the symptoms of mucosal dryness. To do so, PEG is functionalized with a sugar binding lectin (wheat germ agglutinin) to enhance epithelial adhesion through lectin-sugar interactions. Retention and lubricity are characterized on an ex vivo oral tissue tribology rig. WGA-PEG coats and retains on mucin films, oral epithelial cells, and porcine tongue tissue, and offers sustained reduction in coefficient of friction (COF). WGA-PEG could be developed into a useful topical treatment for reducing oral friction and the perception of dry mouth.