Antifouling and antibacterial behaviors of capsaicin-based pH responsive smart coatings in marine environments

Fabrication of Stable Liquid-like Wetting Buckled Surfaces as Bioinspired Antibiofouling Coatings by Using Silicon-Containing Block Copolymers

Inspired by animals with a slippery epidermis, durable slippery antibiofouling coatings with liquid-like wetting buckled surfaces are successfully constructed in this study by combining dynamic-interfacial-release-induced buckling with self-assembled silicon-containing diblock copolymer (diBCP). The core diBCP material is polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS). Because silicon-containing polymers with intrinsic characters of low surface energy, they easily flow over and cover a surface after it has undergone controlled thermal treatment, generating a slippery wetting layer on which can eliminate polar interactions with biomolecules. Additionally, microbuckled patterns result in curved surfaces, which offer fewer points at which organisms can attach to the surface. Different from traditional slippery liquid-infused porous surfaces, the proposed liquid-like PDMS wetting layer, chemically bonded with PS, is stable and slippery but does not flow away. PS-b-PDMS diBCPs with various PDMS volume fractions are studied to compare the influence of PDMS segment length on antibiofouling performance. The surface characteristics of the diBCPs─ease of processing, transparency, and antibiofouling, anti-icing, and self-cleaning abilities─are examined under various conditions. Being able to fabricate ecofriendly silicon-based lubricant layers without needing to use fluorinated compounds and costly material precursors is an advantage in industrial practice.

Biocidal effects of organometallic materials supported on ZSM-5 Zeolite: Influence of the physicochemical and surface properties

Antifouling coatings containing biocidal agents can be used to prevent the accumulation of biotic deposits on submerged surfaces; however, several commercial biocides can negatively affect the ecosystem. In this study, various formulations of a potential biocide product comprising copper nanoparticles and capsaicin supported on zeolite ZSM-5 were analyzed to determine the influence of the concentration of each component. The incorporation of copper was evidenced by scanning electron microscopy and energy dispersive spectroscopy. Similarly, Fourier-transform infrared spectroscopy confirmed that capsaicin was supported on the zeolite surface. The presence of capsaicin on the external zeolite surface significantly reduced the surface area of the zeolite. Finally, bacterial growth inhibition analysis showed that copper nanoparticles inhibited the growth of strains Idiomarina loihiensis UCO25, Pseudoalteromonas sp. UCO92, and Halomonas boliviensis UCO24 while the organic component acted as a reinforcing biocide.

Comparative study between three carbonaceous nanoblades and nanodarts for antimicrobial applications

The design of nanostructured materials occupies a privileged position in the development and management of affordable and effective technology in the antibacterial sector. Here, we discuss the antimicrobial properties of three carbonaceous nanoblades and nanodarts materials of graphene oxide (GO), reduced graphene oxide (RGO), and single-wall carbon nanotubes (SWCNTs) that have a mechano-bactericidal effect, and the ability to piercing or slicing bacterial membranes. To demonstrate the significance of size, morphology and composition on the antibacterial activity mechanism, the designed nanomaterials have been characterized. The minimum inhibitory concentration (MIC), standard agar well diffusion, and transmission electron microscopy were utilized to evaluate the antibacterial activity of GO, RGO, and SWCNTs. Based on the evidence obtained, the three carbonaceous materials exhibit activity against all microbial strains tested by completely encapsulating bacterial cells and causing morphological disruption by degrading the microbial cell membrane in the order of RGO > GO > SWCNTs. Because of the external cell wall structure and outer membrane proteins, the synthesized carbonaceous nanomaterials exhibited higher antibacterial activity against Gram-positive bacterial strains than Gram-negative and fungal microorganisms. RGO had the lowest MIC values (0.062, 0.125, and 0.25 mg/mL against B. subtilis, S. aureus, and E. coli, respectively), as well as minimum fungal concentrations (0.5 mg/mL for both A. fumigatus and C. albicans). At 12 hr, the cell viability values against tested microbial strains were completely suppressed. Cell lysis and death occurred as a result of severe membrane damage caused by microorganisms perched on RGO nanoblades. Our work gives an insight into the design of effective graphene-based antimicrobial materials for water treatment and remediation.

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.

Research Progress of Natural Products and Their Derivatives in Marine Antifouling

With the increasing awareness of environmental protection, it is necessary to develop natural product extracts as antifouling (AF) agents for alternatives to toxic biocides or metal-based AF paints to control biofouling. This paper briefly summarizes the latest developments in the natural product extracts and their derivatives or analogues from marine microorganisms to terrestrial plants as AF agents in the last five years. Moreover, this paper discusses the structures-activity relationship of these AF compounds and expands their AF mechanisms. Inspired by the molecular structure of natural products, some derivatives or analogues of natural product extracts and some novel strategies for improving the AF activity of protective coatings have been proposed as guidance for the development of a new generation of environmentally friendly AF agents.

Trans-cinnamaldehyde loaded chitosan based nanocapsules display antibacterial and antibiofilm effects against cavity-causing Streptococcus mutans

Background

Dental caries is a multifactorial disease, and the bacteria such as Streptococcus mutans (S. mutans) is one of the risk factors. The poor effect of existing anti-bacterial is mainly related to drug resistance, the short time of drug action, and biofilm formation.

Methods

To address this concern, we report here on the cinnamaldehyde (CA) loaded chitosan (CS) nanocapsules (CA@CS NC) sustained release CA for antibacterial treatment. The size, ζ-potential, and morphology were characterized. The antibacterial activities in vitro were studied by growth curve assay, pH drop assay, biofilm assay, and qRT-PCR In addition, cytotoxicity assay, organ index, body weight, and histopathology results were analyzed to evaluate the safety and biocompatibility in a rat model.

Results

CA@CS NC can adsorb the bacterial membrane due to electronic interaction, releasing CA slowly for a long time. At the same time, it has reliable antibacterial activity against S. mutans and downregulated the expression levels of QS, virulence, biofilm, and adhesion genes. In addition, it greatly reduced the cytotoxicity of CA and significantly inhibited dental caries in rats without obvious toxicity.

Conclusion

Our results showed that CA@CS NC had antibacterial and antibiofilm effects on S. mutans and inhibit dental caries. Besides, it showed stronger efficacy and less toxicity, and was able to adsorb bacteria releasing CA slowly, providing a new nanomaterial solution for the treatment of dental caries.

Inhibition Effect of Pseudomonas stutzeri on the Corrosion of X70 Pipeline Steel Caused by Sulfate-Reducing Bacteria

Microbiologically influenced corrosion (MIC) is a common phenomenon in water treatment, shipping, construction, marine and other industries. Sulfate-reducing bacteria (SRB) often lead to MIC. In this paper, a strain of Pseudomonas stutzeri (P. stutzeri) with the ability to inhibit SRB corrosion is isolated from the soil through enrichment culture. P. stutzeri is a short, rod-shaped, white and transparent colony with denitrification ability. Our 16SrDNA sequencing results verify the properties of P. stutzeri strains. The growth conditions of P. stutzeri bacteria and SRB are similar, and the optimal culture conditions are about 30 °C, pH 7, and the stable stage is reached in about seven days. The bacteria can coexist in the same growth environment. Using the weight loss method, electrochemical experiments and composition analysis techniques we found that P. stutzeri can inhibit the corrosion of X70 steel by SRB at 20~40 °C, pH 6~8. Furthermore, long-term tests at 3, 6 and 9 months reveal that P. stutzeri can effectively inhibit the corrosion of X70 steel caused by SRB.

A novel all-organic microcapsule with excellent long-term antibacterial and anti-corrosion performances

This work successfully synthesized the salicylic acid@polyurea-formaldehyde (SA@PUF) microcapsules with PUF microcapsules as shell material and SA as core material. The loading content of SA in the PUF microcapsules was approximately 40 %. The SA@PUF microcapsules had excellent long-term antibacterial properties because the PUF microcapsules controlled the release of SA antifouling agents with the ability to induce reactive oxygen species generation and inactivate bacteria. The antibacterial efficiency of SA@PUF microcapsules after 35 days against Staphylococcus aureus and Pseudomonas aeruginosa remained at 80 % and 81 %, increased by 60 % and 62 % compared with pure SA, respectively. The impedance modulus at 0.01 Hz of the SA@PUF coating reached 5.51 GΩ cm², much higher than blank coating (2.55 GΩ cm²) and PUF coating (4.94 GΩ cm²), indicating that the anti-corrosion property of the SA@PUF coating was much better. This work would contribute to developing novel coatings with long-term antibacterial activity and excellent anti-corrosion performance.

Matrine@chitosan-D-proline nanocapsules as antifouling agents with antibacterial properties and biofilm dispersibility in the marine environment

Antifoulants are the most vital substances in antifouling coatings to prevent marine organisms from colonizing the undersea substrate surfaces. In addition to antibacterial performance, inhibition of biofilm formation is an important criterion for antifouling coatings. In this study, we synthesized pH-responsive matrine@chitosan-D-proline (Mat@CS-Pro) nanocapsules of about 280 nm with antibacterial properties and biofilm dispersibility. The prepared Mat@CS-Pro nanocapsules exhibited high-level antibacterial properties, reaching about 93, 88, and 96% for E. coli, S. aureus, and P. aeruginosa, respectively. Such nanocapsules can cause irreversible damage to bacteria and cause them to lose their intact cell structures. Moreover, Mat@CS-Pro nanocapsules also possessed outstanding dispersal biofilm performances, in which the biofilm thickness of E. coli, S. aureus, and P. aeruginosa was decreased by 33, 74, and 42%, respectively, after 3 days of incubation. Besides, the Mat@CS-Pro nanocapsules had remarkable pH-responsive properties. As the environmental pH became acidic, the nanocapsules swelled to about 475 nm and the released concentration could reach 28.5 ppm after immersion for 10 h but maintained a low releasing rate in pH 8 conditions.

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.

Preparation and Properties of Environmentally Friendly Marine Antifouling Coatings Based on a Collaborative Strategy

Long-term and green marine antifouling coatings are an important means to prolong the service life of ships and other marine instruments and equipment. To accomplish this, we prepared three new green and high-efficiency antifouling coatings containing phthalimide derivatives inspired by capsaicin (PDIC-AC) by using a collaborative strategy that incorporates self-polishing, fouling repelling, and antifouling properties. Static simulation tests confirmed that the zinc acrylate resin of the PDIC-AC has excellent self-polishing properties due to changes in the roughness, surface free energy, and mass loss. Antifouling tests demonstrated that both PDIC and PDIC-AC possess efficient antibacterial and anti-algal effects. Moreover, marine field tests showed that the PDIC-AC are highly antifouling for at least 9 months, and their antifouling effect is similar to that of an antifouling coating with chlorothalonil (CT-AC). The collaborative strategy in this study can be used to research and develop long-term environmentally friendly antifouling coatings.

Influence of nutrition on Cu corrosion by Desulfovibrio vulgaris in anaerobic environment

The eutrophication of seawater is not only harmful to the environment, but also influence microbes' proliferation and then influence biocorrosion of marine engineering materials to a great extent. This study investigated the microbiologically influenced corrosion (MIC) of Cu immersed in the Desulfovibrio vulgaris (a sulfate reducing bacterium) medium with four defined nutritional degrees: total nutrition, P lacking, N lacking, and P&N lacking. When D. vulgaris was cultured in more nutritional medium, more H2S was generated and more serious corrosion of Cu occurred. The concentration of H2S corresponding to the medium with total nutrition was as high as 4.9 × 104(±913.0) ppm. The weight loss of Cu in medium with total nutrition increased by at least 50% compared with other nutritional conditions. The depth of pitting pits on Cu increased obviously with more abundant nutrient elements N and P. The electrochemical tests supported the weight loss and also showed that an obvious passivation zone was formed on the anodic polarization curve. This indicated that a protective film was formed on the surface of Cu against uniform corrosion. The analyses of thermodynamics and experiment data indicated that metabolite MIC (M-MIC) account for the Cu corrosion by D. vulgaris.

Transition Metal Engineering of Molybdenum Disulfide Nanozyme for Biomimicking Anti-Biofouling in Seawater

Nature has evolved diverse strategies to battle surface biofouling colonization and thus provides us novel insights into designing and developing advanced nontoxic antibiofouling materials and technologies. Mimicking the defense mechanisms of natural haloperoxidases in marine algae in response to biofilm colonization, here we show that the less active MoS₂ shows efficient haloperoxidase-mimicking activity through judicious transition metal engineering. Cobalt-doped MoS₂ (Co-MoS₂) displays an excellent haloperoxidase-mimicking performance in catalyzing the Br^- oxidation into germicidal HOBr, roughly 2 and 23 times higher than the nickel-doped MoS₂ and pristine MoS₂, respectively. Accordingly, Co-MoS₂ shows an outstanding antimicrobial effect against drug-resistant bacteria and antibiofouling performance in real field tests in marine environments. The realization of robust haloperoxidase-mimicking activity of MoS₂ via metal engineering may open a new avenue to design highly active transition metal dichalcogenides for antibacterial and antibiofouling applications.

Limiting nitrate triggered increased EPS film but decreased biocorrosion of copper induced by Pseudomonas aeruginosa

Biocorrosion of Cu remains a significant challenge in marine engineering but the mechanism is still not clear. The nutrients in marine environment affect the microbe's growth and the formation of biofilm, and then affect biocorrosion of metal to a large extent. In this study, the effect of NO3- concentration in Pseudomonas aeruginosa (P. aeruginosa) medium on the formation of extracellular polymer substance (EPS) film and biocorrosion of Cu were studied. The experiments results showed that limiting NO3- in culture medium triggered increased EPS film but decreased biocorrosion of Cu induced by P. aeruginosa. With increase of NO3- content in the culture medium, the Cu surface attached less polysaccharides and proteins, but the Cu corrosion rate was accelerated. The weight loss of Cu and the maximum pit depth were both increased with increase of NO3- content. The XPS and XRD analyses indicated that the major corrosion product is Cu2O. The increased corrosion rate with increase of the NO3- level were attributed to the EET-MIC route, the formation of Cu(NH3)2+, and the more loose EPS film.

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.

Physically Switchable Antimicrobial Surfaces and Coatings: General Concept and Recent Achievements

Bacterial environmental colonization and subsequent biofilm formation on surfaces represents a significant and alarming problem in various fields, ranging from contamination of medical devices up to safe food packaging. Therefore, the development of surfaces resistant to bacterial colonization is a challenging and actively solved task. In this field, the current promising direction is the design and creation of nanostructured smart surfaces with on-demand activated amicrobial protection. Various surface activation methods have been described recently. In this review article, we focused on the "physical" activation of nanostructured surfaces. In the first part of the review, we briefly describe the basic principles and common approaches of external stimulus application and surface activation, including the temperature-, light-, electric- or magnetic-field-based surface triggering, as well as mechanically induced surface antimicrobial protection. In the latter part, the recent achievements in the field of smart antimicrobial surfaces with physical activation are discussed, with special attention on multiresponsive or multifunctional physically activated coatings. In particular, we mainly discussed the multistimuli surface triggering, which ensures a better degree of surface properties control, as well as simultaneous utilization of several strategies for surface protection, based on a principally different mechanism of antimicrobial action. We also mentioned several recent trends, including the development of the to-detect and to-kill hybrid approach, which ensures the surface activation in a right place at a right time.

Smart Adsorbents for Aquatic Environmental Remediation

A noticeable interest and steady rise in research studies reporting the design and assessment of smart adsorbents for sequestering aqueous metal ions and xenobiotics has occurred in the last decade. This motivates compiling and reviewing the characteristics, potentials, and performances of this new adsorbent generation's metal ion and xenobiotics sequestration. Herein, stimuli-responsive adsorbents that respond to its media (as internal triggers; e.g., pH and temperature) or external triggers (e.g., magnetic field and light) are highlighted. Readers are then introduced to selective adsorbents that selectively capture materials of interest. This is followed by a discussion of self-healing and self-cleaning adsorbents. Finally, the review ends with research gaps in material designs.

Microbiologically influenced corrosion inhibition mechanisms in corrosion protection: A review

Microbial activities can change the properties of biofilm/metal interfaces to accelerate or decelerate the corrosion of metals in a given environment. Microbiologically influenced corrosion inhibition (MICI) is the inhibition of corrosion that is directly or indirectly induced by microbial action. Compared with conventional methods for protection from corrosion, MICI is environmentally friendly and an emerging approach for the prevention and treatment of (bio)corrosion. However, due to the diversity of microorganisms and the fact that their metabolic processes are greatly complicated by environmental factors, MICI is still facing challenges for practical application. This review provides a comprehensive overview of the mechanisms of MICI under different conditions and their advantages and disadvantages for potential applications in corrosion protection.

Charge transfer channels of silver @ cuprous oxide heterostructure core-shell nanoparticles strengthen high photocatalytic antibacterial activity

Marine biological fouling has always been a hot research topic. In this study, silver @ cuprous oxide (Ag@Cu₂O) core-shell nanoparticles were synthesized via in-situ synthesis method and developed an outstanding antibacterial activity. The bacteriostasis efficiency of Ag@Cu₂O reached to 99% and 98% against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. The minimum inhibitory concentration of Ag@Cu₂O decreased from 113.6 μg/mL to 56.8 μg/mL compared with Cu₂O. Ag@Cu₂O had better antibacterial activity than Cu₂O with lower content of Cu₂O and was more environment friendly. The heterostructure formed at the interface between Ag and Cu₂O promoted the separation and diffusion of photogenerated electron-hole pairs through the charge transfer channel and promoted the generation of reactive oxygen species. The outstanding antibacterial activity of Ag@Cu₂O was strongly depended on the generation of the reactive oxygen species. Density functional theory and finite element method calculations demonstrated that the structure of core-shell improved photocatalytic efficiency. Additionally, synergetic effect of released Ag⁺ and Cu²⁺ also enhanced the bacteriostasis rate and the long-term antifouling performance in 60 days. Hence, the synthesized core-shell Ag@Cu₂O can be applied as novel antifoulants in the marine field.

Evaluation of Rate of Adhesion of Lactobacillus namurensis Strain GYP-74 to Porous Fine Ceramics

This study aimed to evaluate the ratio of adherence of lactic acid bacteria (LAB) to porous fine ceramics in order to develop a novel LAB-rich pickle container for the production of functional fermented vegetables. Some LAB were isolated from the salted rice bran used for pickling (Nukadoko in Japanese). These isolates were classified in Lactobacillus namurensis by phylogenetic analysis. Some pottery-shard (PS) samples were prepared by varying the mixing rate of polyacetal (POM) resin to clay (0–30% (v/v)) and the burning temperature (1000 °C or 1100 °C). A test of the adherence of strain GYP-74 to the PSs was performed. The results showed that the adherence rate was significantly higher in the PSs burned at 1100 °C as compared with those burned at 1000 °C. A pore distribution analysis showed that pore sizes of less than a few µm and pore sizes in the range of a few µm to a few hundred µm were mainly distributed in the PSs without and with POM, respectively. X-ray diffraction analysis showed that both PSs with and without POM contained quartz and hematite. The PSs burned at 1000 °C and 1100 °C specifically contained microcline and mullite, respectively. This study revealed the basal information regarding what makes PSs adequate for LAB adhesion.

Polymers with Hemiaminal Ether Linkages for pH-Responsive Antibacterial Materials

Antibacterial materials containing biocides suffer from the fact that biocides are usually quickly released and hence display a limited antibacterial ability over a long period of time. To overcome this problem, the antibacterial agent 6-chloropurine is conjugated to a monomer via a hemiaminal ether linkage. The functional monomer is then reacted with a urethane acrylate by photopolymerization to yield thin polymer coatings. The release of the antibacterial agent from the coatings is sustained due to the slow kinetics of the hydrolysis of the hemiaminal ether linkage. Antibacterial performance is achieved against S. aureus and E. coli bacteria. This simple strategy can be applied for the rapid preparation of antibacterial coatings on various substrates and other applications such as antifouling or anticorrosion coatings.

Metal-organic framework derived hollow CoFe@C composites by the tunable chemical composition for efficient microwave absorption

Controlling the composition and microstructure of nanomaterials is still a significant challenge in developing high-performance microwave absorption (MA) materials. Herein, metal-organic framework (MOF)-derived hollow CoFe@C nanoboxes are designed and prepared through the facile regulating the mass ratios of ZIF-67/PFC and a thermal annealing treatment. The CoFe@C composite can achieve an excellent MA performance, which have two high reflection loss (RL) values at different thickness. A RL value of -31.0 dB is obtained at 11.84 GHz with a matching thickness of 2.4 mm, and a RL value can reach -44.1 dB (4.08 GHz) at a matching thickness of 5.8 mm, and a correspondingly wide absorbing bandwidth (5.20 GHz, from 9.7 to 14.9 GHz) is simultaneously obtained at a matching thickness of 2.3 mm. The magnetic loss, interfacial polarization and hollow structure are the main reasons for their excellent MA capability. This work provides a research idea for the development of the efficient MOF-based MA materials in practical application.

Extraction, purification, bioactivity and pharmacological effects of capsaicin: a review

Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide), a well-known vanilloid, which is the main spicy component in chili peppers, showing several biological activities and the potential applications range from food flavorings to therapeutics. Traditional extraction of capsaicin by organic solvents was time-consuming, some new methods such as aqueous two-phase method and ionic liquid extraction method have been developed. During past few decades, an ample variety of biological effects of capsaicin have been evaluated. Capsaicin can be used in biofilms and antifouling coatings due to its antimicrobial activity, allowing it has a promising application in food packaging, food preservation, marine environment and dental therapy. Capsaicin also play a crucial role in metabolic disorders, including weight loss, pressure lowing and insulin reduction effects. In addition, capsaicin was identified effective on preventing human cancers, such as lung cancer, stomach cancer, colon cancer and breast cancer by inducing apoptosis and inhibiting cell proliferation of tumor cells. Previous research also suggest the positive effects of capsaicin on pain relief and cognitive impairment. Capsaicin, the agonist of transient receptor potential vanilloid type 1 (TRPV1), could selectively activate TRPV1, inducing Ca²⁺ influx and related signaling pathways. Recently, gut microbiota was also involved in some diseases therapeutics, but its influence on the effects of capsaicin still need to be deeply studied. In this review, different extraction and purification methods of capsaicin, its biological activities and pharmacological effects were systematically summarized, as well as the possible mechanisms were also deeply discussed. This article will give an updated and better understanding of capsaicin-related biological effects and provide theoretical basis for its further research and applications in human health and manufacture development.

Research progress of environmentally friendly marine antifouling coatings

The antifouling mechanisms and research progress in the past three years of environmentally friendly marine antifouling coatings are introduced in this work.

Amphiphilic Marine Antifouling Coatings Based on a Hydrophilic Polyvinylpyrrolidone and Hydrophobic Fluorine-Silicon-Containing Block Copolymer

The development of environmentally friendly and highly efficient antifouling coatings is vastly desirable in the marine industry. Herein, we prepared a novel amphiphilic block copolymer that combined hydrophilic polyvinylpyrrolidone (PVP) with hydrophobic poly(1-(1H,1H,2H,2H-perfluorodecyloxy)-3-(3,6,9-trioxadecyloxy)-propan-2-yl acrylate) (PFA) and polydimethylsiloxane (PDMS). The amphiphilic copolymer (PVP-PFA-PDMS) was blended into a cross-linked PDMS matrix to form a set of controlled surface composition and surface-renewal coatings with efficient antifouling and fouling-release properties. These coatings incorporated the biofouling settlement resistance ability attributed to the hydrophilic PVP segments and the reduced adhesion strength attributed to the low surface energy of fluorine-silicon-containing segments. As expected, the coatings showed an excellent antifouling performance against bacteria and marine unicellular Navicula parva diatoms (98.1 and 98.5% of reduction, respectively) and fouling-release performance against pseudobarnacle adhesion (84.3% of reduction) compared to the pristine PDMS coating. Moreover, a higher-content PVP-based coatings presented higher ability to resist biofouling adhesion. The nontoxic antifouling coating developed in this paper hold the potential to be applied in a variety of marine industrial facilities.

Narrow pH response multilayer films with controlled release of ibuprofen on magnesium alloy

An intelligent narrow pH-triggered multilayer film was prepared on magnesium alloys, aiming to solve the implant infections during the implantation period and improve the corrosion resistance of magnesium alloys. The encapsulation of ibuprofen by chitosan (IBU@CS) makes the release of IBU sensitive to narrow pH (pH 6.8-7.4). Positive charged IBU@CS was assembled with heparin (Hep) to fabricate (Hep/IBU@CS)₁₀ film on AZ31 alloys using layer-by-layer method. The microstructure, composition and anticorrosion properties of the film were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and electrochemical experiments. Cellular activity was studied by MTT cell viability assay. The results showed that the Hep/IBU@CS multilayer films improved the corrosion resistance of magnesium alloys. The in vitro test demonstrated that the release of IBU in the film presented narrow pH sensitivity. The films showed no obvious signs of cytotoxicity conformed by the MTT assay and presented antibacterial properties. These preliminary results demonstrate the potential use of the Hep/IBU@CS multilayer films on magnesium-based implants.

Interplay of the Assembly Conditions on Drug Transport Mechanisms in Polyelectrolyte Multilayer Films

The layer-by-layer film deposition is a suitable strategy for the design and functionalization of drug carriers with superior performance, which still lacks information describing the influence of assembly conditions on the mechanisms governing the drug release process. Herein, traditional poly(acrylic acid)/poly(allylamine) polyelectrolyte multilayers (PEM) were explored as a platform to study the influence of the assembly conditions such as pH, drug loading method, and capping layer deposition on the mechanisms that control the release of calcein, the chosen model drug, from PEM. Films with 20-40 bilayers were assembled at pH 4.5 or 8.8, and the drug loading process was carried out during- or post-film assembly. Release data were fitted to three release models, namely, Higuchi, Ritger-Peppas, and Berens-Hopfenberg, to investigate the mechanism governing the drug transport, such as the apparent diffusion and the relaxation time. The postassembly drug loading method leads to a higher drug loading capacity than the during-assembly method, attributed to the washing out of calcein during film assembly steps in the latter method. Higuchi's and Ritger-Peppas' model analyses indicate that the release kinetic constant increased with the number of bilayers for the postassembly method. The opposite trend is observed for the during-assembly method. The Berens-Hopfenberg release model enabled the decoupling of each drug transport mechanism's contribution, indicating the increase of the diffusion contribution with the number of bilayers for the postassembly method at pH 4.5 and the increase of the polymer relaxation contribution for the during-assembly method at pH 8.8. Deborah's number, which represents the ratio of the polymer relaxation time to the diffusion time, follows the trends observed for the relaxation contribution for the conditions investigated. The deposition of the capping phospholipid layer over the payload also favored the polymer relaxation contribution in the drug release, featuring new strategies to investigate the drug release in PEM.

A smart and active film with tunable drug release and color change abilities for detection and inhibition of bacterial growth

Antimicrobial resistance has become a global issue and thus the development of natural products/biomedical materials composites with antibacterial activities is urgently needed. When acute wounds develop into chronic wounds, the wound environments become alkaline. As long as infections occur, the wound pH further increases, making the wounds difficult to heal. Besides, bacterial growth in poultry, meat, fish and seafood products is usually reflected in a marked increase of pH values. Herein, smart, stimuli responsive self-assembled multilayer and complex film were constructed through the formation of hydrogen bonds and hydrophobic interactions between hydroxypropyl methylcellulose (HPMC) and epigallocatechin-3-gallate (EGCG), thereby greatly reducing the hydrophilicity of HPMC and offering enhanced mechanical strength, superior free radical scavenging capability, and improved water vapor and light barrier properties. The EGCG/HPMC complex film was able to control EGCG release by tuning pH or temperature of the release medium. Furthermore, incorporation of CuS nanoparticles into the film allowed it to triggers EGCG release in an on-demand fashion under near-infrared (NIR) exposure. Bacterial growth in glucose-free nutrient broth medium caused pH to rise (near pH 8.0), leading to transformation of EGCG from phenol type to phenolate ion and then quinone, allowing for spontaneous generation of H₂O₂ to kill bacteria. The complex films changed their color in response to bacterial growth because EGCG transformed from phenol type to quinone type under alkaline condition. The green synthesized EGCG/HPMC complex films can be used as a colorimetric pH indicator and an antibacterial material for wound dressing and food packaging applications.

Preparation of polyacrylonitrile-based fibres with chelated Ag ions for antibacterial applications

The need for an excellent antibacterial material that is sufficiently powerful to never develop bacterial resistance is urgent. In this study, a series of novel polyacrylonitrile-based fibres with chelated Ag ions (referred to as Ag-SH-PANF) were prepared by a two-step chemical modification process: grafting and chelating. The properties of the as-prepared Ag-SH-PANF were characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The antibacterial activities of Ag-SH-PANF were examined against pathogenic bacteria, and an antibacterial mechanism was explicated based on the release of Ag ions from the fibres' surfaces. The results showed that, although chelation occurred between the Ag ions and the grafted amino, sulfhydryl and disulfide groups, Ag-SH-PANF retained its fine microstructure and thermal stability. Moreover, Ag-SH-PANF displayed excellent antibacterial ability against pathogenic bacteria as well as good washing durability. In terms of the antibacterial mechanism, Ag ions are the main bactericidal agents in the role of catalysts and are not consumed in the antibacterial process. Nonetheless, a relatively higher concentration of Ag ions can accelerate the bactericidal process.

Green synthesis of CuO- and Cu2O-NPs in assistance with high-gravity: The flowering of nanobiotechnology

This study, for the first time, reports the synthesis of CuO- and Cu2O nanoparticles (NPs) using the Salvia hispanica extract by a high-gravity technique. The original green synthesis procedure led to the formation of nanoparticles with promising catalytic and biological properties. The synthesized nanoparticles were fully characterized and their catalytic activity was evaluated through a typical Azide-Alkyne Cycloaddition (AAC) reaction. The potential antibacterial activity against gram positive (S. aureus) and gram negative (E. coli) bacteria were investigated. It was shown that the antibacterial properties were independent of the NP morphology as well as of the texture of the synthesis media. As a result, the presently synthesized nanoparticles showed very good photocatalytic and catalytic activities in comparison with the literature. From a biological perspective, they showed lower cytotoxicity in comparison with the literature, and also showed higher antioxidant and antibacterial activities. Thus, these present green CuO and Cu2O nanoparticles deserve further attention to improve numerous medical applications.

Computational Investigation of Antifouling Property of Polyacrylamide Brushes

Antifouling materials and coatings have broad fundamental and practical applications. Strong hydration at polymer surfaces has been proven to be responsible for their antifouling property, but molecular details of interfacial water behaviors and their functional roles in protein resistance remain elusive. Here, we computationally studied the packing structure, surface hydration, and protein resistance of four poly(N-hydroxyalkyl acrylamide) (PAMs) brushes with different carbon spacer lengths (CSLs) using a combination of molecular mechanics (MM), Monte Carlo (MC), and molecular dynamics (MD) simulations. The packing structure of different PAM brushes were first determined and served as a structural basis for further exploring the CSL-dependent dynamics and structure of water molecules on PAM brushes and their surface resistance ability to lysozyme protein. Upon determining an optimal packing structure of PAMs by MM and optimal protein orientation on PAMs by MC, MD simulations further revealed that poly(N-hydroxymethyl acrylamide) (pHMAA), poly(N-(2-hydroxyethyl)acrylamide) (pHEAA), and poly(N-(3-hydroxypropyl)acrylamide) (pHPAA) brushes with shorter CSLs = 1-3 possessed a much stronger binding ability to more water molecules than a poly(N-(5-hydroxypentyl)acrylamide) (pHPenAA) brush with CSL = 5. Consequently, CSL-induced strong surface hydration on pHMAA, pHEAA, and pHPAA brushes led to high surface resistance to lysozyme adsorption, in sharp contrast to lysozyme adsorption on the pHPenAA brush. Computational studies confirmed the experimental results of surface wettability and protein adsorption from surface plasmon resonance, contact angle, and sum frequency generation vibrational spectroscopy, highlighting that small structural variation of CSLs can greatly impact surface hydration and antifouling characteristics of antifouling surfaces, which may provide structural-based design guidelines for new and effective antifouling materials and surfaces.

Recent advances in pH-responsive nanomaterials for anti-infective therapy

The design and synthesis of pH-responsive antibacterial nanomaterials and their applications in anti-infective therapy.