Intrinsic Hydrophobic Cairnlike Multilayer Films for Antibacterial Effect with Enhanced Durability

Chitosan-Urushiol nanofiber membrane with enhanced acid resistance and broad-spectrum antibacterial activity

Due to the large specific surface area and rich pore structure, chitosan nanofiber membrane has many advantages over conventional gel-like or film-like products. However, the poor stability in acidic solutions and relatively weak antibacterial activity against Gram-negative bacteria severely restrict its use in many industries. Here, we present a chitosan-urushiol composite nanofiber membrane prepared by electrospinning. Chemical and morphology characterization revealed that the formation of chitosan-urushiol composite involved the Schiff base reaction between catechol and amine groups and the self-polymerization of urushiol. The unique crosslinked structure and multiple antibacterial mechanisms endowed the chitosan-urushiol membrane with outstanding acid resistance and antibacterial performance. After immersion in HCl solution at pH 1, the membrane maintained its intact appearance and satisfactory mechanical strength. In addition to its good antibacterial performance against Gram-positive Staphylococcus aureus (S. aureus), the chitosan-urushiol membrane exhibited synergistic antibacterial activity against Gram-negative Escherichia coli (E. coli) that far exceeded that of neat chitosan membrane and urushiol. Moreover, cytotoxicity and hemolysis assays revealed that the composite membrane had good biocompatibility similar to that of neat chitosan. In short, this work provides a convenient, safe, and environmentally friendly method to simultaneously enhance the acid resistance and broad-spectrum antibacterial activity of chitosan nanofiber membranes.

Safety assessment of oil extracted from lacquer (Toxicodendron vernicifluum (Stokes) F.A. Barkley) seed: acute and subchronic toxicity studies in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Toxicodendron vernicifluum (Stokes) F.A. Barkley (RVS) is an economic tree species and widely distributed in East Asia. Wood parts and raw lacquers of RVS have been used in coatings, herbal medicines or food supplements, and the leaves, flowers, roots, and fruits of RVS are also widely used in medicine traditionally. Lacquer seed oil (LSO) has potential health benefits and has not previously been evaluated for safety.

AIM OF THE STUDY

The aim of the present study was to investigate the toxicological potential of LSO by acute and subchronic toxicity tests.

MATERIALS AND METHODS

The characterization of fatty acids of the LSO was carried out by gas chromatography. In the acute toxicity study, LSO was administered at single doses of 5000 or 10000 mg/kg by oral gavage. The subchronic toxicity study was conducted by daily oral administration of LSO at doses of 1250, 2500 and 5000 mg/kg/day for 30 consecutive days. The animals were evaluated for clinical observations, body weight, organ weight, feed consumption, biochemical and hematological parameters, and liver, lung, and kidney histology.

RESULTS

There were no mortality and toxic changes were observed in acute toxicity study. The results of subchronic toxicity showed no toxicologically significant changes in clinical observations, body weight, organ weight, biochemical or hematological parameters. Histopathologic results indicated slight hepatic steatosis and inflammatory infiltration in the rats of 5000 mg/kg/day LSO treated group. However, the histopathologic observation was not confirmed by hepatic biochemical analysis.

CONCLUSIONS

These results suggested that the LD₅₀ of LSO is over 10000 mg/kg and LSO is non-toxic for SD rats in acute toxicity study. The no observed adverse effect level (NOAEL) of LSO in rats is considered to be 5000 mg/kg/day, and liver is the potential target organ of LSO for 30-day subchronic toxicity study.

Improved Measurements of the Physical Properties of Oriental Lacquers Using Atomic Force Microscopy and a Nanoindenter

Researchers have widely investigated Oriental lacquers to identify the chemical composition and have elucidated corresponding polymerization mechanisms using rigorous analytical techniques. However, researchers generally test the physical properties of Oriental lacquers by conventional methods that are perhaps overly simplistic. Here, we propose accurate and quantitative methods for evaluating the physical properties of Korean, Vietnamese, and Myanmarese lacquer films using atomic force microscopy (AFM), a nanoindenter, and a 90° peel tester. We obtained surface images of the lacquers in accordance with drying time using scanning electron microscopy and AFM. The Korean lacquer film exhibited fast hardening speed, enhanced hardness, and strong adhesion strength compared with the other lacquers, although the Myanmarese lacquer film had a smoother surface than the Korean lacquer film. We used our characterization approach for evaluating a mixed Korean/Myanmarese (50/50 w/w) lacquer. Our proposed measurement techniques for Oriental lacquer films provided results that agreed with qualitative results from conventional tests. Force–distance curves in AFM and force–displacement with nanoindenter for Oriental lacquer films showed more accurate and quantitative data on the mechanical properties. Thus, researchers will find our approach useful when they optimize the chemical compositions and improve the physical properties of Oriental lacquer films for industrial applications.

Investigation of the Structural Mechanism and Film Growth on Cytoprotective Type I Collagen-Based Nanocoating of Individual Cellular Surfaces

Cell surface coating using the layer-by-layer assembly (LbL) method has many advantages for biomedical applications. Because the cell surface is a dynamic and highly complex structure, it is hypothesized that LbL multilayer films on cells have characteristics different from those observed in traditional film characterization results. Here, to demonstrate the mechanism of LbL-film formation on cells, LbL films are prepared on HeLa cells using collagen (Col) and hyaluronic acid (HA). The growth behavior of the film and the main driving forces inducing the formation of an LbL film on the cells are investigated. Col self-assembles via electrostatic and hydrophobic interactions; therefore, the Col-based film on the cells grows laterally rather than volumetrically. For the film construction conditions, the ionic density and chain conformation of the polymers change, resulting in mainly hydrophobic interactions. Additional interactions, such as hydrophobic interactions and biological recognition between the substrate and building blocks, also exist and tightly stabilize the films on the cells. The Col/HA film shows an even distribution on the cell surface as the extracellular matrix, and it activates proliferation and the cytoprotective signaling pathway under harsh conditions, resulting in the focal adhesion kinase signaling pathway and low lactate dehydrogenase release. Therefore, information for film construction on cells is beneficial to understand the effectiveness of an LbL film for cells.

Structured nanofilms comprising Laponite® and bone extracellular matrix for osteogenic differentiation of skeletal progenitor cells

Functionalized scaffolds hold promise for stem cell therapy by controlling stem cell fate and differentiation potential. Here, we have examined the potential of a 2-dimensional (2D) scaffold to stimulate bone regeneration. Solubilized extracellular matrix (ECM) from human bone tissue contains native extracellular cues for human skeletal cells that facilitate osteogenic differentiation. However, human bone ECM displays limited mechanical strength and degradation stability under physiological conditions, necessitating modification of the physical properties of ECM before it can be considered for tissue engineering applications. To increase the mechanical stability of ECM, we explored the potential of synthetic Laponite® (LAP) clay as a counter material to prepare a 2D scaffold using Layer-by-Layer (LbL) self-assembly. The LAP and ECM multilayer nanofilms (ECM/LAP film) were successfully generated through electrostatic and protein-clay interactions. Furthermore, to enhance the mechanical properties of the ECM/LAP film, application of a NaCl solution wash step, instead of deionized water following LAP deposition resulted in the generation of stable, multi-stacked LAP layers which displayed enhanced mechanical properties able to sustain human skeletal progenitor cell growth. The ECM/LAP films were not cytotoxic and, critically, showed enhanced osteogenic differentiation potential as a consequence of the synergistic effects of ECM and LAP. In summary, we demonstrate the fabrication of a novel ECM/LAP nanofilm layer material with potential application in hard tissue engineering.

The Mechanisms and the Applications of Antibacterial Polymers in Surface Modification on Medical Devices

Medical device contamination caused by microbial pathogens such as bacteria and fungi has posed a severe threat to the patients' health in hospitals. Due to the increasing resistance of pathogens to antibiotics, the efficacy of traditional antibiotics treatment is gradually decreasing for the infection treatment. Therefore, it is urgent to develop new antibacterial drugs to meet clinical or civilian needs. Antibacterial polymers have attracted the interests of researchers due to their unique bactericidal mechanism and excellent antibacterial effect. This article reviews the mechanism and advantages of antimicrobial polymers and the consideration for their translation. Their applications and advances in medical device surface coating were also reviewed. The information will provide a valuable reference to design and develop antibacterial devices that are resistant to pathogenic infections.

Combating Intracellular Pathogens with Nanohybrid-Facilitated Antibiotic Delivery

BACKGROUND

Lipid polymer hybrid nanoparticles (LPHNPs) have been widely investigated in drug and gene delivery as well as in medical imaging. A knowledge of lipid-based surface engineering and its effects on how the physicochemical properties of LPHNPs affect the cell-nanoparticle interactions, and consequently how it influences the cytological response, is in high demand.

METHODS

Herein, we have engineered antibiotic-loaded (doxycycline or vancomycin) LPHNPs with cationic and zwitterionic lipids and examined the effects on their physicochemical characteristics (size and charge), antibiotic entrapment efficiency, and the in vitro intracellular bacterial killing efficiency against Mycobacterium smegmatis or Staphylococcus aureus infected macrophages.

RESULTS

The incorporation of cationic or zwitterionic lipids in the LPHNP formulation resulted in a size reduction in LPHNPs formulations and shifted the surface charge of bare NPs towards positive or neutral values. Also observed were influences on the drug incorporation efficiency and modulation of the drug release from the biodegradable polymeric core. The therapeutic efficacy of LPHNPs loaded with vancomycin was improved as its minimum inhibitory concentration (MIC) (2 µg/mL) versus free vancomycin (4 µg/mL). Importantly, our results show a direct relationship between the cationic surface nature of LPHNPs and its intracellular bacterial killing efficiency as the cationic doxycycline or vancomycin loaded LPHNPs reduced 4 or 3 log CFU respectively versus the untreated controls.

CONCLUSION

In our study, modulation of surface charge in the nanomaterial formulation increased macrophage uptake and intracellular bacterial killing efficiency of LPHNPs loaded with antibiotics, suggesting alternate way for optimizing their use in biomedical applications.

Prevention of Bacterial Colonization Based on Self-Assembled Metal-Phenolic Nanocoating from Rare-Earth Ions and Catechin

Clinically related infection is a critical risk for human health and is usually caused by biofilm formation on medical devices. Herein, typical polyphenols, catechin (Cat), and rare-earth ions (Re³⁺) were used for self-assembled Cat-Re nanoparticles that can be facilely coated on the surface of a polyamide (PA) membrane to synergistically prevent bacterial adhesion and subsequent biofilm formation. The antibacterial adhesion feature of the assembled Cat-Re nanoparticles coated on the PA membrane surface was assessed using Pseudomonas aeruginosa, one of the most common pathogenic bacteria, as probe bacteria under static and dynamic simulation flow conditions. The Cat-Re nanocoating showed excellent antibacterial and anti-adhesion activities against P. aeruginosa and successfully prevented biofilm formation on the material's surface. Regardless of the conditions, the Cat-Re nanocoating significantly suppressed the growth and attachment of P. aeruginosa and maintained >90% inhibition activity with favorable reusability and long-term stability. The results suggest that the self-assembled rare-earth-phenolic nanocoating has promising application potential in the prevention of medical device-related biofilm formation.

Precision synthesis of 3-substituted urushiol analogues and the realization of their urushiol-like performance

Urushiol is a resource-limited natural coating material with diverse applications; however, the synthesis of urushiol analogues and the realization of their urushiol-like performance remain challenging. Herein, four urushiol analogues, namely, 3-((4-alkenoylpiperazin-1-yl)methyl)catechols with the precise 3-substitution pattern on a catechol as that found in urushiol were synthesized by employing the Mannich reaction of catechol with formaldehyde and N-Boc-piperazine as the key step in a two-step route. By using optimization, the advantages of convenience in operation, cost-effectiveness, and scalability could be obtained. The electropolymerization of these analogues on copper was found to be practical due to their higher aerobic stability than urushiol, affording robust coatings with desirable hardness, adhesion strength, hydrophobicity, and thermal stability. Furthermore, the coatings exhibited effective corrosion protection on copper with initial anticorrosion efficiency up to 99.9% and comparatively higher efficiency (more than 97%) after 4 weeks of immersion in 3.5 wt% NaCl solution. The evidence from the electrochemical and infrared spectroscopic characterization data revealed that the electropolymerization process mechanically involved the free radical coupling of phenoxyl radicals to themselves and to the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bonds in the side chain, forming a robust crosslinking coating. This work paves a way for the synthesis of high-performance urushiol analogues with potential applications as metal protection materials.

Regioselective Mannich reaction was performed on catechol, yielding 3-substituted urushiol analogues that could be electropolymerized to achieve the desirable urushiol-like performance.

Urushiol-functionalized mesoporous silica nanoparticles and their self-assembly into a Janus membrane as a highly efficient hemostatic material

Quick hemostasis plays a very important role in preventing hemorrhagic shock and death by controlling blood loss from trauma in civil and military accidents. An ideal quick hemostat should have tissue-adhesive functional groups, clotting factor activating components, and a plasma non-permeable hydrophobic layer. Inspired by the adhesive behavior of mussels, a novel efficient hemostat of urushiol-functionalized mesoporous silica nanoparticles (MSN@U) with a core-shell structure was synthesized and their hemostatic performance was evaluated for the first time. MSN@U could form an amphipathic Janus membrane (a hydrophobic layer and a hydrophilic layer in one membrane) by interfacial self-assembly. The morphology and structure of MSN@U were characterized. The results showed that MSN@U possessed a large specific surface area of 448.91 m2 g-1 and a rich porous structure with an average pore diameter of 3.94 nm. The hydrophilic catechol groups and the long hydrophobic alkyl groups of urushiol allowed MSN@U to self-assemble at the blood/air interface. The former made MSN@U tightly adhere onto blood vessel tissue through covalent bonds, while the latter formed a hydrophobic barrier layer which hindered blood from oozing. Meanwhile, MSN@U would accelerate clotting cascade reactions. These three effects made MSN@U a very quick hemostat with a hemostatic time of 22 ± 2 s on a rat liver laceration. Both in vitro and in vivo tests showed that they had a better hemostatic effect and blood compatibility than MSN. Cell viability evaluations indicated that MSN@U had no cytotoxicity. MSN@U will be a safe and promising hemostatic agent for clinical applications.

Controllable drug release from nano-layered hollow carrier by non-human enzyme

Natural polymers are widely used in biomedical applications because of their numerous effects. Especially, plant-derived natural polymers extracted from cell walls, especially wood, which is abundant, inexpensive and nontoxic to cells, have high mechanical strength to retain their turgor pressure. Plant-derived polymers are also unaffected by enzymes present in the human body, having a strong possibility to create a polymeric structure that releases drugs only exactly where needed. Therefore, plant-derived polymers are suitable for use in drug delivery systems (DDS) as they have durability with few drug leakage issues in the body. Here, to improve drug incorporation and release efficiency, we prepared a multilayer nanofilm from tannic acid (TA) and lignin extracted from plants and wood. We used a strategy involving film degradation by tannase and laccase, which are not present in humans, to depolymerize TA and lignin, respectively. The TA and lignin film was highly stable for 7 days at pH 3-7 and was readily degraded after enzyme treatment. We also observed controllable drug release and anticancer effect from the TA and lignin hollow carriers depending on enzymatic activity. By taking advantage of plant-derived polymers and non-toxic enzymatic reactions, we have demonstrated the film growth and degradation mechanism in depth and explored their use in a smart DDS with easily controlled release kinetics, which is useful as a DDS platform.

A Polysaccharide-Based Antibacterial Coating with Improved Durability for Clear Overlay Appliances

Clear overlay appliances (COAs) are widely used in orthodontic fields because they offer many advantages, such as cost-effectiveness, good formability, and good optical characteristics. However, it is necessary to frequently replace COAs because the thermoplastic polymers that are used to fabricate COAs have poor abrasion resistance and have a tendency to induce bacterial accumulation. Here, we have developed polysaccharide-based antibacterial multilayer films with enhanced durability, intended for COA applications. First, multilayer films composed of carboxymethylcellulose (CMC) and chitosan (CHI) were fabricated on polyethylene terephthalate glycol-modified (PETG), which was preferred material for COA fabrication, via a layer-by-layer (LbL) technique. Next, chemical cross-linking was introduced within the LbL-assembled multilayer films. The LbL-assembled CMC/CHI film, which was made porous and rough by the cross-linking, formed a superhydrophilic surface to prevent the adhesion of bacteria and exhibited a bacterial reduction ratio of ∼75%. Furthermore, the cross-linking of the multilayer film coated on the PETG also improved the chemical resistance and mechanical stability of the PETG under simulated intraoral conditions with artificial saliva, by increasing the bond strength between the polysaccharide chains. We attempted to accumulate datasets using our experimental design and to develop sophisticated methods to assess nanoscale changes through large-scale measurements.

Nanostructured Polymer Thin Films Fabricated with Brush-based Layer-by-Layer Self-assembly for Site-selective Construction and Drug release

Layer-by-Layer (LbL) self-assembly has been investigated for several decades. However, the conventional LbL method has performance problems on the chair-side caused by its cumbersome and time-consuming process. Thus, we investigate a new LbL self-assembly technique for the fast and high efficient preparation process based on the brush. The multilayer films fabricated by simple sequential brushing of polyelectrolyte solutions are compared to the classical dipping method. We characterize the multilayer films by characteristics such as their morphology and thickness, and compare them against those of the classic method by profilometry, atomic force microscopy. We prepare multilayer films with biocompatible polyelectrolytes, chitosan, and alginate incorporated with a hydrophobic drug carrier. For the drug carrier, a poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) block copolymer is introduced to construct micelles containing dexamethasone, which is a well-known osteogenesis-inducing drug. The hydrogen bonding behavior between adjacent layers and micelles is investigated by Fourier transform infrared spectroscopy. Additionally, we analyze the release profiles, degradation profiles and toxicity of the multilayer films for biomedical applications. From these results, we can identify the brushing LbL method as a reliable and more efficient multilayer film-construction process compared to conventional dipping LbL, especially for practical applications in dental and clinical situations.

Polyelectrolyte multilayers for bio-applications: recent advancements

The synergistic relationship between structure and the bulk properties of polyelectrolyte multilayer (PEM) films has generated tremendous interest in their application for loading and release of bioactive species. Layer-by-layer assembly is the simplest, cost effective process for fabrication of such PEMs films, leading to one of the most widely accepted platforms for incorporating biological molecules with nanometre precision. The bulk reservoir properties of PEM films render them a potential candidate for applications such as biosensing, drug delivery and tissue engineering. Various biomolecules such as proteins, DNA, RNA or other desired molecules can be incorporated into the PEM stack via electrostatic interactions and various other secondary interactions such as hydrophobic interactions. The location and availability of the biological molecules within the PEM stack mediates its applicability in various fields of biomedical engineering such as programmed drug delivery. The development of advanced technologies for biomedical applications using PEM films has seen rapid progress recently. This review briefly summarises the recent successes of PEM being utilised for diverse bio-applications.

Interfacial Stacks of Polymeric Nanofilms on Soft Biological Surfaces that Release Multiple Agents

We report a general and facile method that permits the transfer (stacking) of multiple independently fabricated and nanoscopically thin polymeric films, each containing a distinct bioactive agent, onto soft biomedically relevant surfaces (e.g., collagen-based wound dressings). By using polyelectrolyte multilayer films (PEMs) formed from poly(allyl amine hydrochloride) and poly(acrylic acid) as representative polymeric nanofilms and micrometer-thick water-soluble poly(vinyl alcohol) sacrificial films to stack the PEMs, we demonstrate that it is possible to create stacked polymeric constructs containing multiple bioactive agents (e.g., antimicrobial and antibiofilm agents) on soft and chemically complex surfaces onto which PEMs cannot be routinely transferred by stamping. We illustrate the characteristics and merits of the approach by fabricating stacks of Ga³⁺ (antibiofilm agent)- and Ag⁺ (antimicrobial agent)-loaded PEMs as prototypical examples of agent-containing PEMs and demonstrate that the stacked PEMs incorporate precise loadings of the agents and provide flexibility in terms of tuning release rates. Specifically, we show that simultaneous release of Ga³⁺ and Ag⁺ from the stacked PEMs on collagen-based wound dressings can lead to synergistic effects on bacteria, killing and dispersing biofilms formed by Pseudomonas aeruginosa (two strains: ATCC 27853 and MPAO1) at sufficiently low loadings of agents such that cytotoxic effects on mammalian cells are avoided. The approach is general (a wide range of bioactive agents other than Ga³⁺ and Ag⁺ can be incorporated into PEMs), and the modular nature of the approach potentially allows end-user functionalization of soft biological surfaces for programmed release of multiple bioactive agents.

Controlling cell adhesion using layer-by-layer approaches for biomedical applications

Controlling the adhesion of mammalian and bacterial cells at the interfaces between synthetic materials and biological environments is a real challenge in the biomedical fields such as tissue engineering, antibacterial coating, implantable biomaterials and biosensors. The surface properties of materials are known to profoundly influence the adhesion processes. To mediate the adhesion processes, polymeric coatings have been used to functionalize surfaces to introduce diverse physicochemical properties. The polyelectrolyte multilayer films built via the layer-by-layer (LbL) method, introduced by Moehwald, Decher, and Lvov 20years ago, has led to significant developments ranging from the fundamental understanding of cellular processes to controlling cell adhesion for biomedical applications. In this review, we focus our attention on the modification of surface physicochemical properties, using the LbL approach, to construct films which can either promote or inhibit mammalian/bacterial cell adhesion. We also discuss the emerging field of multifunctional surfaces capable of responding to specific cellular activity but being inert to the others.