Capsaicin-Inspired Thiol-Ene Terpolymer Networks Designed for Antibiofouling Coatings

Structurally Heterogeneous Amphiphilic Conetworks of Poly(vinyl imidazole) Derivatives with Potent Antimicrobial Properties and Cytocompatibility

We report the construction of amphiphilic conetwork (APCN)-based surfaces with potent antimicrobial activity and biofilm inhibition ability. The construction strategy is based on the separation of lipophilic alkyl groups (>C6) from the cationic network to obtain good antibacterial properties. The reaction of partially alkylated poly(vinyl imidazole) with the activated halide compounds followed by coating a glass or poly(dimethylsiloxane) (PDMS) sheet leads to the formation of the APCN surface. The dangling alkyl chains, crosslinking junctions, and unreacted vinyl imidazole groups are heterogeneously distributed in the APCNs. The swelling, mechanical property, and phase morphology of the APCN films have been evaluated. Bacterial cell disrupting potency of the APCN coatings increases with increasing alkyl chain length from C6 to C18 with somewhat more of an effect on Escherichia coli as compared to Bacillus subtilis bacteria. The minimum inhibitory amount of the APCNs on glass and a hydrophobic PDMS surface is in the range of 0.02-0.04 mg/cm2 depending on the chain length of the alkyl and the degree of quaternization. The effect of the type of crosslinker for the construction of the conetwork on the antimicrobial property has been evaluated to elucidate the exclusive design of the APCNs. The APCN-based coatings provide potent biocidal activity without much negatively affecting the hemocompatibility and cytocompatibility. These APCNs provide a good model system for comparative evaluation of the biocidal property and structural effect on the biocidal activity.

Antifouling Slippery Surface against Marine Biofouling

Titanium and its alloys have become the most excellent structure materials for naval seawater pipelines due to their high strength and good corrosion resistance. However, marine biofouling poses a serious threat to titanium alloy piping systems because of their good biocompatibility. Recently, the biomimetic antifouling coating, a novel antifouling method, has received great attention. Here, based on this biomimetic idea, we develop a nontoxic antifouling slippery surface (AFSS) using silicone oil, silane coupling agent, nanosilica, nanoceramic coating, epoxy resin, and capsaicin. The developed AFSS has excellent slippery performance for various droplets, good durability, and a superior self-cleaning property. Additionally, the antifouling performance of the AFSS was significantly enhanced, as confirmed by the reduced adhesion of proteins (70.7%), bacteria (97.2%), and algae (97.7%) compared to the ordinary titanium alloy. With these excellent properties, the AFSS was expected to be a promising candidate for protecting titanium alloy piping systems from marine biofouling.

Capsaicin-Modified Fluorosilicone Based Acrylate Coating for Marine Anti-Biofouling

Capsaicin has been extensively studied for its excellent antifouling activity and very low environmental toxicity. However, mixing natural capsaicin with coatings can cause rapid capsaicin leakage, severely shortening its antifouling cycle. In this study, we describe the preparation and performance of a new capsaicin-modified marine antifouling organofluorosilicone, which is based on silicone and fluorine acrylate monomers covalently bound to an organic antimicrobial monomer, HMBA (N-(4-hydroxy-3-methoxybenzyl)-acrylamide) on a polymer network. The chemical grafting of HMBA into the polymer has improved the problem of short antifouling life of the coating due to antifouling agent leakage and the environmental pollution caused by the leakage. The study focused on the synthesis of pristine acrylate monomers with organic bioactive groups prepared from vanillin amine salts and their co-polymerization in the presence of distal acrylate oligomers. The resulting cross-linked films were characterized using infrared spectroscopy, contact angle, and adhesion analyses. The results indicate that the materials had good adhesion, low surface energy, and were resistant to prolonged immersion in water. The polyacrylate coating synthesized from acrylate exhibited antibacterial and anti-algae activity. Biological tests on the marine microorganisms, Pseudomonas species, Shewanella species, and Navicula incerta, revealed a 97%, 98%, and 99% reduction compared to the blank control group, respectively, indicating that the coating has strong anti-adhesive ability. This work is expected to develop a promising material for marine antifouling.

Synergistically Improved Antifouling Efficiency of a Bioinspired Self-renewing Interface via a Borneol/ Boron Acrylate Polymer

Underwater facilities are often perplexed by severe and ubiquitous biofouling. The widely applied commercial antifouling materials still have several challenges in static applications. Herein, a polymer containing isoborneol and borane (PBABs), the borneol derivative structure and grafted pyridine-triphenylborane (PTPB) as antifouling groups were prepared by radical polymerization. PBABs showed high antibacterial rates for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) of up to 95.1% and 81.1%, respectively, confirming superior antibacterial adhesion propertys. More importantly, PBABs effectively reduced the expression of mussel adhesion protein, indicating superior antifouling propertys, resulting from the synergistic effect of multiple antifouling functional groups on the material's surface. Therefore, the PBABs have been evaluated as noncytotoxic, low-cost, easily synthesized, and mass-produced, which demonstrates their great potential for actual marine applications.

One-pot method for preparation of capsaicin-containing double-network hydrogels for marine antifouling

Marine biofouling which interferes with normal marine operation and also causes huge economic loss has become a worldwide problem. With the development of society, there is an urgent need to develop non-toxic and efficient anti-fouling strategies. Capsaicin is an environmentally friendly antifouling agent, but controlling the stable release of capsaicin from the coating is still a challenge to be solved. To achieve long-lasting antifouling property, in this work, we incorporate a derivative of capsaicin N-(4-hydroxy-3-methoxybenzyl)acrylamide (HMBA) to prepare double network (DN) hydrogels and make HMBA a part of the polymer network. Polyvinyl alcohol (PVA) has good hydrophilicity, and as a soft and ductile network, acrylamide (AM) and HMBA can polymerize to generate a rigid and brittle network. By adjusting the content of HMBA in the DN hydrogels, we can obtain a PVA–PAHX hydrogel with high mechanical strength, low swelling rate, and excellent antifouling effect, which provides a feasible way for the practical application of a hydrogel coating in long-term marine antifouling.

Double-network hydrogel coatings containing capsaicin analogs were prepared by a one-pot method based on a green strategy, by incorporating a derivative of capsaicin N-(4-hydroxy-3-methoxybenzyl) acrylamide into the polymer network. An antifouling effect can be achieved.

Preparation and evaluation of polyphenol derivatives as potent antifouling agents: addition of a side chain affects the biological activity of polyphenols

In this study, eight polyphenol derivatives were prepared to serve as green antifoulants. Polyphenol derivatives, which can hinder the growth of bacteria and algae and decrease the adhesion of some marine organisms, showed good AF activity; in particular, the activities of these derivatives were much higher than those of the corresponding polyphenols. The antibacterial rates of the products (20 μg ml^-1) exceeded 88%. Moreover, the anti-algal rates of compounds a3, b1, b2, b3 and b4 (15 μg ml^-1) were over 57% at 240 h, but these compounds showed low toxicity, and the 120 h EC₅₀ values were > 6.60 μg ml^-1. In addition, there were fewer marine microorganisms on the test panel than on the control. The above results show that some polyphenol derivatives possess relatively high antibacterial, anti-algal, and AF activity; more notably, the addition of chlorine atoms and amide groups can further increase the activity of these derivatives.

Anti-Biofouling Polymers with Special Surface Wettability for Biomedical Applications

The use of anti-biofouling polymers has widespread potential for counteracting marine, medical, and industrial biofouling. The anti-biofouling action is usually related to the degree of surface wettability. This review is focusing on anti-biofouling polymers with special surface wettability, and it will provide a new perspective to promote the development of anti-biofouling polymers for biomedical applications. Firstly, current anti-biofouling strategies are discussed followed by a comprehensive review of anti-biofouling polymers with specific types of surface wettability, including superhydrophilicity, hydrophilicity, and hydrophobicity. We then summarize the applications of anti-biofouling polymers with specific surface wettability in typical biomedical fields both in vivo and in vitro, such as cardiology, ophthalmology, and nephrology. Finally, the challenges and directions of the development of anti-biofouling polymers with special surface wettability are discussed. It is helpful for future researchers to choose suitable anti-biofouling polymers with special surface wettability for specific biomedical applications.

Corn Oil-Water Separation: Interactions of Proteins and Surfactants at Corn Oil/Water Interfaces

Purification and collection of industrial products from oil-water mixtures are commonly implemented processes. However, the efficiencies of such processes can be severely influenced by the presence of emulsifiers that induce the formation of small oil droplets dispersed in the mixtures. Understanding of this emulsifying effect and its counteractions which occur at the oil/water interface is therefore necessary for the improvement of designs of these processes. In this paper, we investigated the interfacial mechanisms of protein-induced emulsification and the opposing surfactant-induced demulsification related to corn oil refinement. At corn oil/water interfaces, the pH-dependent emulsifying function of zein protein, which is the major storage protein of corn, was elucidated by the surface/interface-sensitive sum frequency generation (SFG) vibrational spectroscopy technique. The effective stabilization of corn oil droplets by zein protein was illustrated and correlated to its ordered amide I group at the oil/water interface. Substantial decrease of this ordering with the addition of three industrial surfactants to corn oil-zein solution mixtures was also observed using SFG, which explains the surfactant-induced destabilization and coalescence of small oil droplets. Surfactant-protein interaction was then demonstrated to be the driving force for the disordering of interfacial proteins, either by disrupting protein layers or partially excluding protein molecules from the interface. The ordered zein proteins at the interface were therefore revealed to be the critical factor for the formation of corn oil-water emulsion.

Synthesis and fouling resistance of capsaicin derivatives containing amide groups

Capsaicin, which inhibits the attachment and growth of fouling organisms, is a bioactive substance that is generally recognized as a highly active environmental algaecide agent. Its derivatives are simple in structure and have been proven to have low toxicity and be environmentally friendly. Six capsaicin derivatives were synthesized via Friedel-Crafts alkylation and characterized using melting point (MP) analysis, infrared (IR) spectroscopy, nuclear magnetic resonance (¹H NMR) spectroscopy and high-resolution mass spectrometry (HRMS). The inhibition effect and toxicity of these compounds towards Phaeodactylum tricornutum (P. tricornutum), Skeletonema costatum (S. costatum) and Chaetoceros curvisetus (C. curvisetus) were tested. The capsaicin derivatives all showed inhibitory effects. In particular, compound E with over 95% (3 mg·L^-1) inhibition and intermediate toxicity was superior to the other compounds, reflecting an environmentally friendly effect. This finding indicates that capsaicin derivatives possess the potential to become environmentally friendly algaecide agents. The fouling resistance of capsaicin derivatives incorporated into the coatings as antifouling agents was measured in the marine environment. The results showed that capsaicin derivatives possess excellent fouling resistance, with only a small amount of algae and muck attached to the tested panel at 90 days. The above results provide a scientific basis for the application of capsaicin derivatives as environmentally friendly antifouling agents.

Probing the Interfacial Interactions of Monoclonal and Bispecific Antibodies at the Silicone Oil-Aqueous Solution Interface by Using Sum Frequency Generation Vibrational Spectroscopy

Silicone oil has been widely utilized in the pharmaceutical industry especially as a lubricant coating commonly used in syringes for the smooth delivery of drugs. Protein structure perturbation and aggregation have been reported upon protein contacting silicone oil by using indirect methods and ex-situ techniques. The conclusions derived from such indirect and ex-situ methods may not truly reflect the exact nature of the protein-silicone oil interfacial interactions. Recently, we have successfully demonstrated that sum frequency generation (SFG) vibrational spectroscopy can be used as a powerful and direct method of studying the fusion protein-silicone oil interfacial interactions in situ and in real time. In this article, we studied monoclonal and bispecific antibody interactions with the silicone oil surface by using SFG spectroscopy. Being structurally and functionally different in the nature of fusion proteins and antibodies, this study is important in enhancing our current understanding of protein-silicone oil interfacial interactions. Both types of antibodies investigated here readily and strongly adsorb onto the silicone oil surface and remain stable at least for 10 h. SFG spectra in the amide I region for monoclonal and bispecific antibodies centered at 1660 and 1665 cm^-1, respectively, suggest the difference in their molecular structures. The absence of the antibody signals in the amide I region of time-dependent and static SFG spectra obtained for preadsorbed antibodies onto silicone oil after contacting polysorbate 80 (PS-80) surfactant suggests that PS-80 can effectively remove both types of antibodies from the silicone oil surface. This study demonstrated the feasibility of using SFG spectroscopy as a powerful tool for probing the antibody-interfacial interactions in situ and in real time.

Diblock Polymer Brush (PHEAA- b-PFMA): Microphase Separation Behavior and Anti-Protein Adsorption Performance

In this paper, a series of amphiphilic diblock polymers of poly(hydroxyethylacrylamide)- b-poly(1H,1H-pentafluoropropyl methacrylate) (PHEAA- b-PFMA) were grafted from silicon wafer via surface-initiated atom transfer radical polymerization (SI-ATRP). Surface wettability and chemical compositions of the modified surfaces were characterized by contact angle goniometer and X-ray photoelectron spectroscopy (XPS) respectively. Molecular weight and polydispersity of each block were measured using gel permeation chromatography (GPC). The topography and the microphase separation behavior of PHEAA- b-PFMA surfaces were investigated by atomic force microscope (AFM). The results show that only when the grafting density (σ) and thickness of PHEAA brush were in the range of 0.9-1.3 (chain/nm²) and 6.6-15.1 nm, respectively, and the ratio of PFMA/PHEAA varied from 89/42 to 89/94, could the diblock copolymer phase separate into nanostructures. Further, the antiprotein adsorption performance of the modified surfaces against BSA, fibrinogen, and lysozyme was studied. The results indicated the modified surfaces could reduce the protein adsorption compared to the pristine silicon wafer. For Fibrinogen, the antiadsorption effect of PHEAA- b-PFMA-modified surfaces with microphase segregation was better than that of corresponding PHEAA modified surfaces. The results provide further evidence that surface composition and microphase segregation of fluorinated moieties of block copolymer brushes significantly impact protein adsorption behaviors.