Synergistic antibacterial effect and mechanism between Cu2O nanoparticles and quaternary ammonium salt in moisture-curable acrylic coatings

Combining with various antibacterial mechanisms is the preferred strategy to fabricate coatings with effective antibacterial performance. Herein, Cu2O nanoparticles and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride, a kind of quaternary ammonium salt (QAS), were simultaneously incorporated into a moisture-curable acrylic resin in order to achieve both contact-killing and release-killing abilities for antibacterial coatings. The surface morphology, surface composition and basic properties of the coatings were thoroughly characterized. The antibacterial performance of the coatings was determined by in-vitro bacteriostatic test. Under the constant total mass fraction of antibacterial agents, both Cu2O and QAS content possessed the highest value on the coating surface at Cu2O/QAS mass ratio of 1:1, and correspondingly, the coatings reached sterilizing rate above 99 % against both E. coli and S. loihica, indicating the existence of synergistic effect between Cu2O and QAS. The synergistic antibacterial mechanism of the coatings involved two aspects. Firstly, the combination of contact-killing and release-killing biocides resulted in high bactericidal and antibiofilm activity against different bacteria. Further, the grafting of QAS molecules on the surface of Cu2O particles brought about the spontaneous migration of nanoparticles to the coating surface. The interaction between Cu2O and QAS also inhibited the phase separation of QAS and prolonged the release of Cu2+ at the same time. The coatings, therefore, exhibited stable antibacterial performance at varied service conditions.

Novel bioactive nanospheres show effective antibacterial effect against multiple endodontic pathogens

Aim

The current study evaluated the antibacterial activity of a newly developed quaternary ammonium polymethacrylate (QAPM)-containing bioactive glasses (BGs) via a two-step method by our group, namely BGs-HAEMB, and explored its cytotoxicity and biocompatibility.

Methods

The antibacterial effects of the BGs-HAEMB against planktonic bacteria, bacterial biofilm formation, and experimental root canal biofilms of persistent pathogens (Enterococcus faecalis, Streptococcus sanguis and Porphyromonas endodontalis) associated with endodontic infection were evaluated in vitro by agar diffusion tests, direct contact tests and live/dead staining. The cytotoxicity and biocompatibility of BGs-HAEMB were evaluated by CCK-8 assays in vitro and a skin implantation model in vivo.

Results

Compared to three clinically used endodontic sealers (Endofill, AH Plus, and iRoot SP), BGs-HAEMB exhibited the relatively strongest antibacterial effect against E. faecalis, S. sanguis and P. endodontalis after sitting for 14 and 28 days (P < 0.01). SEM images and CLSM images also showed that for each tested bacteria, BGs-HAEMB killed the most microorganism among all the experimental groups, regardless of treatment for 7 days or 28 days (P < 0.05). Besides, the BGs-HAEMB-treated groups showed a relatively low cytotoxicity (RGRs ranging from 88.6% to 102.9%) after 1, 3, and 7 days of exposure. Meanwhile, after 28 days of implantation, the inflammatory grade in BGs-HAEMB treated group was assessed as Grade I, in which the average numbers of inflammatory cells (6.7 ± 2.1) were less than 25.

Conclusions

BGs-HAEMB exerted a long-term and stable antibacterial effect. The remarkable biocompatibility of BGs-HAEMB in vitro and in vivo confirmed its possible clinical application as a potential alternative in the development of the next generation of endodontic sealers.

Starch/poly (butylene adipate-co-terephthalate) blown films contained the quaternary ammonium salts with different N-alkyl chain lengths as antimicrobials

Antimicrobial biodegradable packaging is in high demand as a one-two punch against microbiological and plastic hazards. Two quaternary ammonium salts (QAS) with different N-alkyl chain lengths were used for starch/poly (butylene adipate-co-terephthalate) (PBAT) blown antimicrobial films. Dioctadecyl dimethyl ammonium chloride (D1821) contributed to a homogeneous film morphology at 5% w/w level, while micro-pores occurred with didodecyl dimethyl ammonium chloride (D1221). Increasing QAS content weakened hydrogen bonding interactions. D1821 promoted the formation of intercalated structure of nano-clays, and improved the strength, thermal stability, barrier, and surface hydrophobicity of the films. Conversely, adding D1221 decreased the mechanical properties, and significantly enhanced the surface hydrophilicity. The films with 3% and 5% w/w D1221 obviously inhibited the growth of both Staphylococcus aureus and Escherichia coli, while those with D1821 cannot show clear zone against the Gram-negative. 5% w/w D1221-loaded film delayed the growth of microorganisms in beef, of which the total viable count was 5.75 lg CFU/g after 21-day chilling storage. Findings supported that QAS had the potential for manufacturing starch/PBAT antimicrobial packaging, but the release kinetics and cytotoxicity still need to be systematically explored before application.

Fabrication of reversible bacteria-killing and bacteria-releasing cotton fabrics with anti-bacteria adhesion capacity for potential application in reusable medical materials

Nowadays, more and more smart antibacterial materials have been prepared to meet some specific application area, and most of these materials have complex fabrication processes or incompatible biocompatibility. In this paper, a smart monomer that can switch between the form of quaternary ammonium salt and zwitterionic betaine was prepared and grafted onto cotton fabric. This finished cotton was smart too, it had nice antibacterial performance (99.89 % for E. coli and 99.97 % for S. aureus) in the form of quaternary ammonium salt, and it could release most of the attached bacteria when transferred to the form of zwitterionic betaine in PBS, and the form of zwitterionic betaine could converse back to the state of quaternary ammonium salt in HAC. Simultaneously, it was biocompatible in the form of zwitterionic betaine form. Furthermore, this smart material had nice function reproducibility after repeated transformations. In general, the smart antibacterial cotton could switch between bacteria-killing and bacteria-releasing reversibly, and had good biocompatibility and nice reproducibility, showing a potential application in reusable medical protective materials.

A novel chitosan antioxidant bearing sulfhydryl group: Synthesis, characterization and activity assessment

To improve the antioxidant activity, sulfhydryl groups (-SH) were introduced into chitosan. Acylated chitosan derivatives, chitosan cationic salt derivatives, hydroxypropyl trimethylammonium chloride chitosan quaternary ammonium salt (HACC) derivatives and N,N,N-trimethyl chitosan iodine (TMC) derivatives were obtained. The chitosan derivatives were characterized by FTIR and 1H NMR to confirm the successful synthesis. Ellman's reagent was used to determine that the compound contained free sulfhydryl groups. The water solubility and thermal stability of chitosan and derivatives were evaluated. The antioxidant activities of the derivatives were verified, including DPPH radical scavenging activity, superoxide anion radical scavenging activity and reducing power activity. The novel chitosan derivatives showed excellent antioxidant activities. Toxicity assay used L929 cells proved that the derivatives had no significant toxic. The results showed that the chitosan derivatives bearing sulfhydryl groups described in this paper has a certain antioxidant effect, which provides a practical approach for further study of chitosan.

Experimental study on the effect of quaternary ammonium salt + monoethylene glycol compound to methane hydrate agglomeration in oil-water system

Natural gas hydrate has been a critical risk to the safety of offshore oil and gas well test and subsea transportation. Herein, the effect of three quaternary ammonium salt (QAS) surfactants with monoethylene glycol (MEG) to methane hydrate agglomeration in water-oil system was experimentally studied by a rocking cell. Based on the hydrate volume fraction and the slider trajectory, a classification method of the gas hydrate anti-agglomerants was established. All the QASs in this work show the capability of reducing hydrate agglomeration, among which N1,N3-didodecyl-N1,N1,N3,N3-tetramethylpropane-1,3-diaminium chloride (AA-2) has the best anti-agglomerating performance, and the slider moved at a large trajectory of 61-174 mm. The three QASs were compounded with 5, 10, and 15 wt% (based on water) MEG, respectively. Experimental results showed that AA-2 compounded with MEG (10 wt%) can effectively prevent hydrate agglomeration. The slider moved in the cell at the full trajectory range, showing the compound of grade A performance. The compound of QAS and MEG shows a synergistic effect. The addition of QAS can significantly reduce the required MEG dosage for the hydrate blockage prevention than the MEG only situation. Considering the economic factors of the filed hydrate management, the combination application of QAS + MEG may provide a promising option.

The germicidal effect, biosafety and mechanical properties of antibacterial resin composite in cavity filling

In recent years, dental resin materials have become increasingly popular for cavity filling. However, these materials can shrink during polymerization, leading to microleakages that enable bacteria to erode tooth tissue and cause secondary caries. As a result, there is great clinical demand for the development of antibacterial resins. The principle of antibacterial resin includes contact killing and filler-release killing of bacteria. For contact killing, quaternary ammonium salts (QACs) and antibacterial peptides (AMPs) can be added. For filler-release killing, chlorhexidine (CHX) and nanoparticles are used. These antibacterial agents are effective against gram-positive bacteria, gram-negative bacteria, fungi, and more. Among them, QACs has a lasting antibacterial effect, and silver nanoparticles even have a certain ability to kill viruses. Biocompatibility-wise, QACs, AMPs, and CHX have low cytotoxicity to cells when added into the resin. However, nanoparticles with smaller particle sizes have higher cytotoxicity. In terms of mechanical properties, QACs, AMPs, and CHX do not negatively affect the resin. However, the addition of magnesium oxide can have a negative impact. This paper reviews the types and antibacterial principles of commonly used antibacterial resins in recent years, evaluates their antibacterial effect, biological safety, and mechanical properties, and provides references for selecting clinical filling materials.

Quaternary ammonium salts targeted regulate the surface charge distribution of activated carbon: A study of their binding modes and modification effects

Activated carbon (AC) is negatively charged in aqueous solution, which seriously restricts its application range. Quaternary ammonium salt as a common cationic surfactant was utilized to modify the surface charge distribution of materials. The evolution of the surface charge distribution of AC modified by benzalkonium chloride (BAC), diallyl dimethyl ammonium chloride (DDA) and 3-chloro-2-hydroxypropyl tri-methyl ammonium chloride (CTA) was investigated. Results showed that the surface charge of AC modified by CTA does not change significantly. BAC has a high molecular weight, low surface electrostatic potential and large steric hindrance due to its hydrophobic long-chain alkyl. The diffusion of BAC molecules from solution to AC changed its charge distribution. But these molecules were difficult to combine with AC surface, and most of them were adsorbed into the pores of AC to form aggregates, resulting in a significant reduction in the surface area. BAC modified AC could enhance the adsorption capacity of F^- in aqueous solution through electrostatic attraction, but the improvement effect was limited due to the reduction of surface area, and the maximum adsorption capacity was only increased from 1.18 to 3.31 mg/g. DDA has a small molecular weight and high surface electrostatic potential and easily binds to the surface of AC. Some CC bonds in DDA combined with the ionized hydrogen ions derived from phenolic hydroxyl groups in AC to form carbonium-ions. Then, they could react with AC to form ether bonds, causing DDA to be closely bonded with the surface of AC. DDA realizes the targeted regulation of the surface charge distribution of AC, it has little effect on the porous structure of AC. The modified AC still maintained strong adsorption capacity, and the maximum adsorption capacity for F^- was 54.98 mg/g. Meanwhile, a large number of zeolites were loaded on the modified AC and formed coating structures.

Antibacterial and Alkali-responsive Cationic Waterborne Polyurethane Based on Modification of Aloe Emodin

Cationic water-based polyurethane(CWPU) was synthesized to explore aloe-emodin modifies to obtain CWPU materials with better comprehensive performance. It provides a simple way to synthesize antibacterial waterborne polyurethane, which is to introduce the end-blocking group of herbal extracts into the structure. It contains synergistic antibacterial effect of herbal antibacterial and quaternary ammonium ion on Escherichia coli. It makes the material resist the erosion of bacterial, and increase the service life of materials. When the pH value of the environment changes, the UV absorbance of the aloe-emodin modified cationic water-based polyurethane(AE-CWPU) also changes. Therefore, within a certain detection range, AE-CWPU has great applications in the field of smart response materials. The modified thermodynamic properties have been improved, and the mechanical properties basically maintained the maximum stress, and the elongation at break was reduced.

Tailorable antibacterial and cytotoxic chitosan derivatives by introducing quaternary ammonium salt and sulfobetaine

Chitosan (CS) derivatives with improved water solubility, antibacterial activity and adequate biocompatibility are attracting increasingly interest in medical application. Herein, we have successfully synthesized isocyanate terminated quaternary ammonium salt (IQAS) and sulfopropylbetaine (ISB) to be readily covalently bounded to CS skeleton by selective reaction with amino and hydroxyl groups. And their molecular structures and crystallinity were confirmed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and X-ray diffraction. The effect of the substitution degree, carbon chain length, content ratio of IQAS/ISB on their water solubility, antibacterial activity and cytotoxicity were systematically investigated, which shows that those properties of the CS derivatives can be tailored by adjusting the grafted antibacterial agents and their additive amount. The structure-property relationship of these CS derivatives may provide a solid guidance on the development of CS derivatives for more efficient practical applications.

Cationic covalent-organic framework for sulfur storage with high-performance in lithium-sulfur batteries

Covalent organic frameworks (COFs) with pre-designed structure and customized properties have been employed as sulfur storage materials for lithium-sulfur (Li-S) batteries. In this work, a cationic mesoporous COF (COF-NI) was synthesized by grafting a quaternary ammonium salt group onto the pore channel of COFs via a one-pot three components tandem reaction strategy. The post-functionalized COFs were utilized as the matrix framework to successfully construct the Li-S battery with high-speed capacity and long-term stability. The experimental results showed that, after loading active material sulfur, cationic COF-NI effectively suppressed the shuttle effect of the intermediate lithium polysulfide species in Li-S batteries, and exhibited better cycle stability than the as-obtained neutral COF (COF-Bu). For example, compared with COF-Bu based sulfur cathode (521 mA h g^-1), the cationic COF-NI based sulfur cathode maintained a discharge capacity of 758 mA h g^-1 after 100 cycles. These results clearly showed that appropriate pore environment of COFs can be prepared by rational design, which can reduce the shuttle effect of lithium polysulfide species and improve the performance of Li-S battery.

Structural stability of DHMAI antibacterial dental composite following in vitro biological aging

OBJECTIVE

To assess the impact of the quaternary ammonium antibacterial agent, Dimethyl-Hexadecyl-Methacryloxyethyl-Ammonium Iodide (DHMAI), on structural stability of an experimental resin composite after biological aging.

METHODS

Experimental resin composites containing 7.5% of DHMAI were incubated in a biological medium in the presence of a Streptococcus Mutans (SM) strain during 3 months. The physicochemical, mechanical, and thermal properties, before and after 3 months of aging, were evaluated using: Degree of Conversion (DC), Residual Functions (RF), Vitreous Transition (Tg), Thermal Expansion Coefficient (CTE) and thermal degradation using Fourier Transform Infrared Spectroscopy Analysis (FTIRATR), Differential Scanning Calorimetry (DSC), Thermo Mechanical analyses (TMA) and Thermo Gravimetric Analysis (TG).

RESULTS

Incorporation of DHAMI increased DC and decreased RF. After aging, DHMAI decreased and slowed RF release. Incorporation of 7.5% DHAMI provided significant modification of the thermal behavior (Tg and thermal degradation) but did not affect CTE. After aging, DHMAI enhanced the structural stability and improved resistance against biodegradation compared to the control composite.

SIGNIFICANCE

The development of an antibacterial dental composite based on DHMAI improved its physical, mechanical, and thermal behaviors, possibly enhancing dental composite longevity. Results suggest that DHMAI could be used in the composition of other bioactive dental materials.

Bactericidal and antifouling electrospun PVA nanofibers modified with a quaternary ammonium salt and zwitterionic sulfopropylbetaine

Bacterial adhesion and colonization on material surfaces have attracted great attention due to their potential threat to human health. Combining bactericidal and antifouling functions has been confirmed as an optimal strategy to prevent microbial infection. In this work, biodegradable electrospun polyvinyl alcohol (PVA) nanofibers were chosen due to its high specific area and abundant reactive hydroxyl groups. A quaternary ammonium salt (IQAS) and zwitterionic sulfopropylbetaine (ISB), both containing isocyanate (NCO) groups, were chemically bonded to the PVA nanofiber surface via a coupling reaction between the OH groups of the PVA nanofibers and the NCO groups of IQAS or ISB. The results indicated that the antimicrobial rates of PVA nanofibers modified by IQAS (0.5%) reached 99.9% against both gram-positive Staphylococcus aureus (S. aureus, ATCC 6538) and gram-negative Escherichia coli (E. coli, ATCC 25922). Additionally, the live/dead staining and cytotoxicity test indicated that the dual functional IQAS/ISB/PVA nanofibers exhibited excellent bactericidal and antifouling activities with low cytotoxicity. This work may provide practical guidelines to fabricate bactericidal and antifouling materials for healthcare applications, including but not limited to wound dressings, textile, food packaging and air filtration.

Construction of antimicrobial and biocompatible cotton textile based on quaternary ammonium salt from rosin acid

Antimicrobial cotton textiles (CT) show great promise for wound dressings. However, modifying CTs to have antimicrobial properties requires balancing the killing of microbes while protecting normal cells. In this study, the surface of CT was modified using maleopimaric acid quaternary ammonium cations (MPA-N⁺) from rosin acid. The surfaces morphology and chemical composition were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), which confirmed that the MPA-N⁺ modified CT (CT-g-MPA-N⁺) was prepared. CT-g-MPA-N⁺ shows strong and broad spectrum antimicrobial activities against Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus). It also exhibits prominent durability of antimicrobial capability even after soaking in PBS for 6 days, and can effectively inhibit bacterial biofilm formation. Most importantly, the excellent biocompatibility of CT-g-MPA-N⁺ was verified by hemocompatible and cytotoxic assays. This work is believed to be promising method to prepare antimicrobial cotton textiles by surface modification and suggest the great potential application in wound dressing.

Cetylpyridinium chloride is a potent AMP-activated kinase (AMPK) inducer and has therapeutic potential in cancer

AMP-activated protein kinase (AMPK) is a eukaryotic energy sensor and protector from mitochondrial/energetic stress that is also a therapeutic target for cancer and metabolic disease. Metformin is an AMPK inducer that has been used in cancer therapeutic trials. Through screening we isolated cetylpyridinium chloride (CPC), a drug known to dose-dependently inhibit mitochondrial complex 1, as a potent and dose-dependent AMPK stimulator. Mitochondrial biogenesis and bioenergetics changes have also been implicated in glioblastoma, which is the most aggressive form of brain tumors. Cetylpyridinium chloride has been administered in humans as a safe drug-disinfectant for several decades, and we report here that under in vitro conditions, cetylpyridinium chloride kills glioblastoma cells in a dose dependent manner at a higher efficacy compared to current standard of care drug, temozolomide.

Antimicrobial resins with quaternary ammonium salts as a supplement to combat the antibiotic resistome in drinking water treatment plants

The increasing finding of pathogens and antibiotic resistance genes (ARGs) in drinking water has become one of the most challenging global health threats worldwide. However, conventional disinfection strategies in drinking water treatment plants (DWTPs) require further optimization in combating the antibiotic resistome. Here, we show that antimicrobial resins with quaternary ammonium salts (AMRs-QAS) exhibit great potentials in diminishing specific potential pathogens that relatively resist chlorine or UV disinfection in DWTPs, and comprehensive analyses using microscopy and fluorescence techniques revealed that the antimicrobial capacity of AMRs-QAS mainly proceed via the bacterial adsorption and cell membrane dissociation. Moreover, a total of 15 among 30 selected ARGs, as well as 4 selected potential pathogens including Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli and Staphylococcus aureus were all detected in the source water. Coupling the AMRs-QAS with 0.2 mg/L chlorine resulted in higher removal efficiencies than chlorination (2 mg/L) or UV disinfection (400 mJ cm^-2) for all the detected pathogens and ARGs in drinking water and significantly decreased the relative abundances of Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli, as well as all the detected ARGs (p < 0.05). Co-occurrences of pathogens and ARGs were revealed by a correlation network and possibly accounts for the ARGs removal. This coupled disinfection strategy overcomes the limitations of individual disinfection methods, i.e. the enrichment of specific pathogens and ARGs among bacterial populations, and provides an alternative for minimizing health risks induced by the antibiotic resistome in DWTPs.

Synthesis of graphene oxide-quaternary ammonium nanocomposite with synergistic antibacterial activity to promote infected wound healing

BACKGROUND

Bacterial infection is one of the most common complications in burn, trauma, and chronic refractory wounds and is an impediment to healing. The frequent occurrence of antimicrobial-resistant bacteria due to irrational application of antibiotics increases treatment cost and mortality. Graphene oxide (GO) has been generally reported to possess high antimicrobial activity against a wide range of bacteria in vitro. In this study, a graphene oxide-quaternary ammonium salt (GO-QAS) nanocomposite was synthesized and thoroughly investigated for synergistic antibacterial activity, underlying antibacterial mechanisms and biocompatibility in vitro and in vivo.

METHODS

The GO-QAS nanocomposite was synthesized through amidation reactions of carboxylic group end-capped QAS polymers with primary amine-decorated GO to achieve high QAS loading ratios on nanosheets. Next, we investigated the antibacterial activity and biocompatibility of GO-QAS in vitro and in vivo.

RESULTS

GO-QAS exhibited synergistic antibacterial activity against bacteria through not only mechanical membrane perturbation, including wrapping, bacterial membrane insertion, and bacterial membrane perforation, but also oxidative stress induction. In addition, it was found that GO-QAS could eradicate multidrug-resistant bacteria more effectively than conventional antibiotics. The in vitro and in vivo toxicity tests indicated that GO-QAS did not exhibit obvious toxicity towards mammalian cells or organs at low concentrations. Notably, GO-QAS topically applied on infected wounds maintained highly efficient antibacterial activity and promoted infected wound healing in vivo.

CONCLUSIONS

The GO-QAS nanocomposite exhibits excellent synergistic antibacterial activity and good biocompatibility both in vitro and in vivo. The antibacterial mechanisms involve both mechanical membrane perturbation and oxidative stress induction. In addition, GO-QAS accelerated the healing process of infected wounds by promoting re-epithelialization and granulation tissue formation. Overall, the results indicated that the GO-QAS nanocomposite could be applied as a promising antimicrobial agent for infected wound management and antibacterial wound dressing synthesis.

Design, synthesis, and herbicidal activity of novel quaternary ammonium salt derivatives

A series of novel quaternary ammonium salt derivatives were designed and synthesized by introducing the herbicide carboxylic acid into substituted aminoacetanilide compounds which derived from herbicides alachlor or acetochlor, using the intermediate derivatization methods in an attempt to obtain novel candidates for weed control. The herbicidal activity assays in greenhouse demonstrated that some of the title compounds exhibited good herbicidal activities against velvet leaf, youth-and-old age, barnyard grass, and foxtail. Especially, III9 gave the best activity (EC₅₀ (ga.i/ha): YOA 34.1, VEL 33.6, FOX 15.9, BYG 36.2). The field trials indicated that III9 had better herbicidal activity than the commercial herbicide imazethapyr to control broadleaf weeds at 150ga.i/ha. The present work demonstrated that the quaternary ammonium salt derivatives can be used as potential lead compounds for discovering novel herbicides with improved activity. III9 itself is worthy of being further developed as an herbicidal candidate. Further syntheses, structure optimization studies, and field trials around III9 are in progress.

Effectiveness of the DHMAI monomer in the development of an antibacterial dental composite

OBJECTIVE

Development of antibacterial dental composites is the ultimate goal to decrease carious disease occurrence and increase the restoration longevity. For this purpose, the quaternary ammonium dimethyl-hexadecyl-methacryloxyethyl-ammonium iodide (DHMAI) and the methacryloyloxyethylphosphorylcholine (MPC) have been incorporated in experimental methacrylate-based composite resins. This aims to first investigate the effect of each alone and then their combined effect.

METHODS

Synthesized DHMAI and commercial MPC were added either alone or combined at different concentrations to experimental dental composite. Flexural strength (FS) and modulus (FM) were tested to select the optimal concentrations. Only selected composites were evaluated for Vickers hardness (HV) and the degree of conversion (DC) using fourier transform infrared spectroscopy analysis (FTIR-ATR). Antibacterial activity was assessed using tests on colony-forming unit (CFU), scanning electron microscopy (SEM) and Alamarblue assay to measure the metabolic activity. Streptococcus mutans biofilm was chosen to be grown on the composite surfaces during 96h at 37°C.

RESULTS

Incorporation of 7.5% DHMAI in composite improved the degree of conversion and gave a strong antibacterial effect with a reduction of (∼98%) in CFU and (∼50%) of metabolic activity with acceptable mechanical properties. Addition of MPC to DHMAI affects mechanical properties of composites without providing a better antibacterial activity.

SIGNIFICANCE

Composites with DHMAI greatly reduced S. mutans biofilm and improved the degree of conversion without scarifying the composites' mechanical properties. DHMAI may have wide applicability to other dental materials in order to inhibit caries and improve the longevity of restorations.

A water-soluble pH fluorescence probe based on quaternary ammonium salt for bioanalytical applications

A novel fluorescence probe Rhodamine-Ethanediamine-Iodomethane (REI) was successfully prepared to serve as an efficient sensing platform for H(+) with fully reversibility mainly between the pH 4.2 and 7.2 in simple buffer solution. The introduction of quaternary ammonium salt with positive charge can not only manage to increase the solubility and sensitivity of probe REI, but also avoid the "alkalizing effect" due to charge-induced effect compared to the reference probe Rhodamine-Ethanediamine (RE). In particular, probe REI was well used for monitoring the weak acid pH fluctuations in lysosome of the live HeLa cells due to its excellent biological properties, including low cytotoxicity, high selectivity, good sensitivity and membrane permeability.

Durable contact active antimicrobial materials formed by a one-step covalent modification of polyvinyl alcohol, cellulose and glass surfaces

In this work we have applied a direct covalent linkage of quaternary ammonium salts (QAS) to prepare a series of contact active antimicrobial surfaces based on widely utilized materials. Formation of antimicrobial polyvinyl alcohol (PVA-QAS), cellulose (cellulose-QAS) and glass (glass-QAS) surfaces was achieved by one step synthesis with no auxiliary linkers. The X-ray photoelectron spectroscopy (XPS) revealed tridentate binding mode of the antimicrobial agent. The antimicrobial activity of the prepared materials was tested on Bacillus cereus, Alicyclobacillus acidoterrestris, Escherichia coli and Pseudomonas aeruginosa. Active site density of the modified materials was examined and found to correlate with their antimicrobial activity. Stability studies at different pH values and temperatures confirmed that the linkage of the bioactive moiety to the surface is robust and resistant to a range of pH and temperatures. Prolonged long-term effectiveness of the contact active materials was demonstrated by their repeated usage, without loss of the antimicrobial efficacy.