Quaternary Ammonium Salt Groups Research Articles

Antimicrobial Hybrid Coatings Combining Enhanced Biocidal Activity under Visible-Light Irradiation with Stimuli-Renewable Properties.

Hybrid, organic-inorganic, biocidal films exhibiting polishing properties were developed as effective long-lasting antimicrobial surface coatings. The films were prepared using cationically modified chitosan, synthesized by the reaction with 3-bromo-N,N,N-trimethylpropan-1-aminium bromide, to introduce permanent biocidal quaternary ammonium salt (QAS) groups along the polymer backbone and were cross-linked by a novel, pH-cleavable acetal cross-linker, which allowed polishing the hybrid coatings with the solution pH. TiO2 nanoparticles, modified with reduced graphene oxide (rGO) sheets, to narrow their band gap energy value and shift their photocatalytic activity in the visible light regime, were introduced within the polymer film to enhance its antibacterial activity. The hybrid coatings exhibited an effective biocidal activity in the dark (∼2 Log and ∼3 Log reduction for Gram-negative and Gram-positive bacteria, respectively), when only the QAS sites interacted with the bacteria membrane, and an excellent biocidal action upon visible-light irradiation (∼5 Log and ∼6 Log reduction for Gram-negative and Gram-positive bacteria, respectively) due to the synergistic antimicrobial effect of the QAS moieties and the rGO-modified TiO2 nanoparticles. The gradual decrease in the film thickness, upon immersion of the coatings in mildly basic (pH 8), neutral (pH 7), and acidic (pH 6) media, reaching 10, 20, and 70% reduction, respectively, after 60 days of immersion time, confirmed the polishing behavior of the films, whereas their effective antimicrobial action was retained. The biocompatibility of the hybrid films was verified in human cell culture studies. The proposed approach enables the facile development of highly functional coatings, combining biocompatibility and bactericidal action with a "kill and self-clean" mechanism that allows the regeneration of the outer surface of the coating leading to a strong and prolonged antimicrobial action.

Quaternary ammonium functionalized cationic polythiophene for the detection and imaging of gram-positive bacteria

The persistence of bacterial infections in humans causes severe adverse health consequences and uncertainties in the global economy. It is of great advantage to develop a rapid tool for the earlier diagnosis and treatment of pathogenic infections. In this work, an active polythiophene derivative containing reactive pentafluorophenyl (PFP) ester groups was prepared via Fe3+-catalyzed oxidative polymerization using PFP thiophene-3-acetate as the monomer. The active polythiophene derivative was conjugated with N,N-dimethyl-1,3-propanediamine via ester-amine reaction, followed by quaternization with 1-bromobutane. The resultant polythiophene derivative (QPDMAPTA) possesses the quaternary ammonium salt groups on its side chain and shows cationic zeta potential of + 12.79 eV at neutral pH. The as-prepared QPDMAPTA exhibits high-level antibacterial action against gram-positive bacteria (Staphylococcus aureus (S. aureus), Staphylococcus epidermidis (S. epidermidis), and methicillin-resistant S. aureus) as compared with gram-negative bacteria (Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa)). Furthermore, the zeta potential measurements show higher uptake of QPDMAPTA by gram-positive bacteria than the gram-negative bacteria, which depicts the active role of the biological interactions with the charged QPDMAPTA in its differential uptake and bactericidal effect. This phenomenon also facilitates the identification of gram-positive bacteria by observing the color changes of collected bacterial cakes before and after treatment with QPDMAPTA. The fluorescent nature of QPDMAPTA can be used for imaging and detection of gram-positive bacteria via adopting a fluorescent technique.

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.

Dual-crosslinked mussel-inspired smart hydrogels with enhanced antibacterial and angiogenic properties for chronic infected diabetic wound treatment via pH-responsive quick cargo release

The healing of chronic diabetic wounds remains a key challenge due to its susceptibility to bacterial infection, the inflammatory wound microenvironment, and difficulty in angiogenesis. Herein, a pH-responsive, mussel-inspired, double-crosslinking injectable, and adhesive smart hydrogel formula was exploited to overcome these obstacles simultaneously. The multifunctional double-crosslinking hydrogel was developed through the formation of catechol-catechol adducts and a Schiff-based reaction between amino groups (−NH2) in chitosan quaternary ammonium salt (HTCC) and aldehyde groups (–CHO) in oxidized dextran-dopamine (OD-DA). The double-crosslinking mechanism gave the hydrogels great mechanical properties. Most importantly, via the effective encapsulation of silver nanoparticles (AgNPs) and pro-angiogenic drug deferoxamine (DFO), the hydrogel was given with antibacterial and angiogenic features respectively. At the infected diabetic wound area, the double Schiff base bonds (DA and OD; HTCC and OD-DA) in the hydrogels could quickly achieve pH-response and accomplish a sustained and controlled release of drugs to accelerate wound healing. Through the combination of AgNPs and HTCC, the hydrogel exhibited antimicrobial capacities to gram-positive bacteria (S. aureus) and gram-negative bacteria (E. coli), it did not cause toxic side effects and avoided drug resistance. The DFO released at the infected diabetic wound area promoted angiogenesis by enhancing the expression of hypoxia-inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF). We elucidated the mechanisms by which the designed hydrogels accelerated the healing of bacterial infected diabetic wounds in vitro and in vivo, and our hydrogels represented a general strategy for the healing of a wide range of tissue injuries.

Monodisperse polystyrene microspheres containing quaternary ammonium salt groups by two-stage dispersion polymerization: effect of reaction parameters on particle size and size distribution

A facile approach to prepare monodisperse polystyrene (PS) particles containing quaternary ammonium salts with long alkyl chain was reported. The PS particles containing quaternary ammonium salts are prepared by two-stage dispersion polymerization in ethanol/water (80/20 w/w) mixture with polyvinylpyrrolidone (PVP) as a steric stabilizer and fatty alcohol polyoxyethylene ether (AEO-9) as a co-stabilizer. Polymerizations are conducted using N′-dimethyl-N-n-dodecyl-N-2-methacryloyloxyethylammonium bromide (QDMDB) as a comonomer added in the second stage. We identify reaction conditions where one can obtain the functional polystyrene microspheres with a size distribution less than 3%. The influence of the initiator concentration, the styrene monomer concentration, the stabilizer concentration, and QDMDB comonomer concentration on the average particle size and the efficient of variation are investigated comprehensively. The novel particles are examined using scanning electron microscopy (SEM), gel permeation chromatography (GPC), zeta potential, and nuclear magnetic resonance (1H NMR). QDMDB comonomer not only functionalized the polystyrene particles but also proved to be effective in controlling the particle size and size distribution. According to these results, we show that two-stage dispersion polymerization is an effective pathway for the structure design of the functional microspheres.

Preparation of intrinsic antibacterial silicone rubber with matrix tethering quaternary ammonium salt groups

The immobilization of the antibacterial agent in the matrix is crucial to endow materials with excellent antibacterial activity. In this paper, a strategy was presented to prevent the antibacterial agent leaching out from the cross-linking network of silicone rubber via construction of the matrix tethering quaternary ammonium salt (QAS) groups by covalent bond. A series of hydroxyl-terminated polysiloxanes with pendent QAS groups were prepared and characterized. The polysiloxanes were subsequently used as a matrix for preparing an intrinsic antibacterial silicone rubber. SEM analysis indicated a high compatibility of the formulations of silicone rubber. The silicone rubber exhibits excellent antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Most importantly, the silicone rubber exhibits prominent durability of antibacterial activity even after staying in the natural environment for 3 months. Moreover, the hydrophilicity of silicone rubber could be adjusted by the content of QAS groups.

Antimicrobial Activities of Thermoplastic Polyurethane/Clay Nanocomposites against Pathogenic Bacteria.

As a thermoplastic polymer with an impressive combination of mechanical properties and biological compatibility, thermoplastic polyurethane (TPU) is one of the important polymers used in various applications such as biomaterials, conducting materials, and tissue engineering. Nanocomposites made of TPUs with nanoclays were prepared by melt-compounding, and the effects of clay on antibacterial activities and physical properties of nanocomposites were investigated. X-ray powder diffraction, water contact angle, and TEM results were analyzed to investigate the effects of dispersion and modification of clays in TPU/clay nanocomposites. Using the pour plating method, scanning electron microscopy technique, and disk diffusion test, TPU/clay nanocomposites were observed to show contact killing activity against bacteria. The antibacterial activities of TPU/clay nanocomposites were found to be affected by the dispersion state and amount of organic modifier of clays. TPU nanocomposites containing 5 wt % organically modified clay showed 98.5% killing efficiency against Gram-negative Escherichia coli and 99.9% against Gram-positive Staphylococcus aureus, while neat TPU showed almost none. The positively charged quaternary ammonium salt groups of clay in TPU/clay nanocomposites interacted with the negatively charged cytoplasmic membrane of bacteria, and the dead bacteria were eliminated by weakened adhesion on hydrophobic backbone surfaces.

Synthesis and properties of waterborne UV‐curable polydimethylsiloxane‐based polyurethane oligomers: UV‐cured film with excellent water resistance and thermostability

This paper designed and synthesized a series of waterborne UV-curable polydimethylsiloxane‐based polyurethane oligomers which contain polydimethylsiloxane segment in the end of the main chain, a plurality of double bonds in the side chain and two kinds of hydrophilic groups including nonionic polyethylene glycol with low molecular weight and ionic quaternary ammonium salt groups. The unique structure endowed not only the oligomer with an excellent water solubility, but also the UV-cured film with hydrophobicity, thermostability and mechanical properties. The prepared oligomers could form a stable white emulsion and had excellent photopolymerization capability, and their conversions of double bonds were all over 92%. The UV-cured film containing long chain polydimethylsiloxane exhibited better hydrophobicity, heat resistance and tensile strength. The polydimethylsiloxane segment located in the end of the oligomer molecular chain was more conducive to its enrichment in the surface of the cured films and improving of the hydrophobicity of the cured films. The water absorption, surface water contact angle and the initial decomposition temperature (T5%) of the obtained UV-cured films were 2.7%, 91 and 301 °C, respectively.

Effects of Preparation Method on the Physicochemical Properties of Cationic Nanocellulose and Starch Nanocomposites.

Nanocellulose (NC) has attracted attention in recent years for the advantages offered by its unique characteristics. In this study, the effects of the preparation method on the properties of starch films were investigated by preparing NC from cationic-modified microcrystalline cellulose (MD-MCC) using three methods: Acid hydrolysis (AH), high-pressure homogenization (HH), and high-intensity ultrasonication (US). When MD-MCC was used as the starting material, the yield of NC dramatically increased compared to the NC yield obtained from unmodified MCC and the increased zeta potential improved its suspension stability in water. The NC prepared by the different methods had a range of particle sizes and exhibited needle-like structures with high aspect ratios. Fourier transform infrared (FTIR) spectra indicated that trimethyl quaternary ammonium salt groups were introduced to the cellulose backbone during etherification. AH-NC had a much lower maximum decomposition temperature (Tmax) than HH-NC or US-NC. The starch/HH-NC film exhibited the best water vapor barrier properties because the HH-NC particles were well-dispersed in the starch matrix, as demonstrated by the surface morphology of the film. Our results suggest that cationic NC is a promising reinforcing agent for the development of starch-based biodegradable food-packaging materials.

Electropolymerization-Induced Positively Charged Phenothiazine Polymer Photoelectrode for Highly Sensitive Photoelectrochemical Biosensing.

Exploring the fabrication of an electrode with high photoelectric conversion efficiency and abundant functional groups for ideal photoelectrochemical (PEC) sensor development is highly urgent but faces a significant challenge. Herein we report an electropolymerization strategy for the preparation of phenothiazine polymeric film on an indium tin oxide (ITO) surface (PPT/ITO), within only a few seconds, and monomers. The fabricated PPT/ITO electrode possessed excellent stability and abundant quaternary ammonium salt groups for developing a highly sensitive PEC sensor through electrostatic binding with negatively charged materials. In this context, a CdS QDs-functionalized PPT/ITO electrode (CdS/PPT/ITO) was proposed and applied to the analysis of chlorpyrifos, used as a model target organophosphorous pesticide (OP). The thiocholine generated from acetylcholinesterase (AChE)-induced catalyzed hydrolysis of acetylthiocholine (ATCh) efficiently directed CdS QDs away from PPT/ITO via electrostatic repulsion, subsequently decreasing PEC current, whereas chlorpyrifos prohibited the generation of thiocholine through inhibiting AChE activity. As compared to the case where chlorpyrifos is absent, significantly enhanced PEC current is determined and is proportional to chlorpyrifos amounts. Thus, the developed CdS/PPT/ITO-based PEC sensor achieved excellent chlorpyrifos biosensing with improved sensitivity down to approximately ng/mL level with good specificity. We envision the proposed strategy will provide a new path to conveniently fabricate photoelectrodes possessing high performance, which will have more useful applications in PEC sensing.

Sunlight-Driven Wearable and Robust Antibacterial Coatings with Water-Soluble Cellulose-Based Photosensitizers.

Herein, a simple, effective, and general strategy is demonstrated to obtain a water-soluble and nontoxic cellulose-based photosensitizer (CPS) with enhanced photodynamic antibacterial activity through introducing protoporphyrin IX (PpIX) and quaternary ammonium salt (QAS) groups onto the cellulose backbone. The synergistic effect of the anchoring and diluting effect of the cellulose backbone and the electrostatic repulsion between QAS groups effectively inhibit the π-π stacking of PpIX groups, thus the as-prepared CPS exhibits markedly enhanced reactive oxygen species (ROS) yield. Meanwhile, the positively charged QAS groups endow the CPS with water-solubility and a strong attractive force to bacteria. As a result, the CPS can rapidly and efficiently kill drug-resistant bacteria strains, including E. coli and S. aureus, with a low light dose (2.4 J cm-2 ) and low concentration of PpIX groups (0.35 × 10-6 m). Benefiting from the excellent processability and formability, the CPS is readily applied as a sunlight-driven wearable and robust antibacterial coating by a spray coating and later crosslinking procedure.

Poly(quaternary ammonium salt-epoxy) grafted onto Ce doped ZnO composite: An enhanced and durable antibacterial agent

The composite after referred to as P(DMDAAC-AGE)/(Ce-ZnO) was prepared via free radical polymerization by polymer including quaternary ammonium salt and epoxy group which grafted onto the surface of Ce-ZnO. ZnO nanorods, Ce-ZnO nanorods, P(DMDAAC-AGE), P(DMDAAC-AGE)/ZnO composites, P(DMDAAC-AGE)/(Ce-ZnO) composites and commercial antimicrobials were respectively treated on the cotton fabrics and their biological properties were investigated. There is a synergistic effect between Ce-ZnO and N+ from the polymer in the fabric treated with P(DMDAAC-AGE)/(Ce-ZnO) composite so that it had a better antibacterial activity than pure polymer and pure Ce-ZnO. The antimicrobial rate of fabric treated with P(DMDAAC-AGE)/(Ce-ZnO) composite could reach up to 96%. And in order to investigate the durable ability, the fabric was washed multiple times to simulate the daily use washing. The result showed that the fabric still gave a superior antibacterial performance after 11 cycles (the equivalent of 55 times house laundering). Simultaneously, the differences in the amount of P(DMDAAC-AGE)/(Ce-ZnO) composite deposited on the fibers after washing were also investigated.

A new water-soluble polythiophene derivative as a probe for real-time monitoring adenosine 5′-triphosphatase activity in lysosome of living cells

Detection of the adenosine 5′-triphosphatase (ATPase) activity in lysosome of living cells is of great importance for clinical diagnosis of many related diseases, including cancer. In this work, a new water-soluble polythiophene derivative named ZnPT bearing both quaternary ammonium salt groups and dipicolylamine-Zn2+ (DPA-Zn2+) complexes in its side chain, was designed and synthesized for this propose. The probe mainly localized to lysosome with good biocompatibility and membrane penetration. The real-time, continuous, direct, and label-free assays were achieved through a fluorescence "turn-on" mode by taking advantages of the reaction specificity of ATPase with ATP and the high binding selectivity of ZnPT toward ATP substrate over its hydrolysis product (ADP). This well designed strategy should provide a facile and effective way for investigating ATPase-relevant biological processes.

PDMS tri-block copolymers bearing quaternary ammonium salts for epidermal antimicrobial agents: Synthesis, surface adsorption and non-skin-penetration

Quaternary ammonium salts are widely used as epidermal and topical antimicrobial agents in medical treatments due to their broad activity, excellent performance and ready availability. However, their epidermal application has revealed many noticeable disadvantages, including short-term functionality, environmental toxicity, rapid antimicrobial resistance and skin penetration. Here, a series of tri-block copolymers grafted with dimethylaminopropyl benzyl chloride and based on a polydimethylsiloxane (PDMS) backbone, referred to as PDMS-b-(PDMS-g-BC)-g-PDMS, were prepared with well-controlled chain length and cationic grafting content. The quaternary ammonium salt-containing polymers were effective antimicrobial agents against epidermal pathogenic microbes, such as E. coli, S. albus and C. albicans. By incorporating hydrophilic and antimicrobial quaternary ammonium salt groups into the hydrophobic PDMS backbones, the amphiphilic tri-block copolymers were water-soluble but capable of assembling onto different surfaces, driven by electrostatic attraction or hydrophobic repulsion, which yielded long-term functionality on the surface. Moreover, the enlarged molecular size prevented penetration though full-thickness rat skins. These findings suggest a promising application of polymeric quaternary ammonium salts with hydrophobic moieties as epidermal antimicrobial agents.

Fabrication of Water-Resistant Nacre-like Polymer/Clay Nanocomposites via in Situ Polymerization.

Fabrication and characterization of water-resistant nacre-like polymer/clay nanocomposites, in which clay platelets and hydrophobic polymer chains are alternately stacked in parallel, are reported. Hydrophilic clay was converted by an ion-exchange reaction with a methacrylate monomer having a long alkyl chain and a quaternary ammonium salt group at the end. The subsequent in situ polymerization bound the neighboring clay surfaces, leading to the preferential orientation of the clay platelets owing to their high aspect ratio. The composites maintained excellent mechanical properties even after being immersed in water for more than a day. Strong shape stability was observed in water as well as in various organic solvents.

Synthesis, characterization, and the antifungal activity of chitosan derivatives containing urea groups

As an abundant and renewable polysaccharide, chitosan has been drawing broad attention due to its natural properties. For the further utilization of chitosan, chemical modification can be applied in improving its water solubility and the bioactivities. In this study, four chitosan derivatives were synthesized by the reaction of chloracetyl chitosan derivative with quaternary ammonium salt (CTCS) and urea groups bearing 4-amino-pyridine, including BCTCS, 2CBCTCS, 3CBCTCS, and 4CBCTCS. The structure characteristics of synthesized products were established based on FT-IR spectroscopy, 1H NMR, and elemental analysis. Their antifungal activities against Fusarium oxysporum f. sp. niveum, Phomopsis asparagus, Fusarium oxysporum f. sp. cucumebrium Owen, and Botrytis cinerea were estimated by hyphal measurement in vitro. Generally, the inhibition ratio of most products was higher than 80% at 1.0mg/mL. Their inhibitory activity decreased roughly in the order: 4CBCTCS>3CBCTCS>2CBCTCS>BCTCS>CTCS>chitosan, resulted from the different degrees of substitution of the effectively active groups–urea groups. Meanwhile, the effects on beneficial soil microbes, including Bacillus cereus, Bacillus subtilis, and Sinorhizobium saheli LMG7837, of these synthesized chitosan derivatives were evaluated by disk diffusion method. The results showed that these substances do not inhibit the growth of beneficial bacteria and some of them could be employed as green antifungal biomaterials.

Smart Biointerface with Photoswitched Functions between Bactericidal Activity and Bacteria-Releasing Ability.

Smart biointerfaces with capability to regulate cell-surface interactions in response to external stimuli are of great interest for both fundamental research and practical applications. Smart surfaces with "ON/OFF" switchability for a single function such as cell attachment/detachment are well-known and useful, but the ability to switch between two different functions may be seen as the next level of "smart". In this work reported, a smart supramolecular surface capable of switching functions reversibly between bactericidal activity and bacteria-releasing ability in response to UV-visible light is developed. This platform is composed of surface-containing azobenzene (Azo) groups and a biocidal β-cyclodextrin derivative conjugated with seven quaternary ammonium salt groups (CD-QAS). The surface-immobilized Azo groups in trans form can specially incorporate CD-QAS to achieve a strongly bactericidal surface that kill more than 90% attached bacteria. On irradiation with UV light, the Azo groups switch to cis form, resulting in the dissociation of the Azo/CD-QAS inclusion complex and release of dead bacteria from the surface. After the kill-and-release cycle, the surface can be easily regenerated for reuse by irradiation with visible light and reincorporation of fresh CD-QAS. The use of supramolecular chemistry represents a promising approach to the realization of smart, multifunctional surfaces, and has the potential to be applied to diverse materials and devices in the biomedical field.

Evaluation of the starch-based flocculants on flocculation of hairwork wastewater

China is the world's largest producer of wigs, and the manufacturing generates large quantities of hairwork effluents. Coagulation/flocculation is an important step in the water treatment process. In this study, two versions of starch-based flocculants were successfully prepared through etherification and graft copolymerization, respectively. Starch-3-chloro-2-hydroxypropyl triethyl ammonium chloride (St-CTA-DQ) and starch-graft-poly[(2-methacryloyloxyethyl) trimethyl ammonium chloride] (St-g-PDMC-DQ) both contain strongly cationic quaternary ammonium salt groups, but have differing cationic contents, specifically, the degree of substitution (DS) and grafting ratio (G). Furthermore, the additional functional groups were distributed on different chain sites (the starch backbone for St-CTA-DQ, and the branch chains for St-g-PDMC-DQ). These two flocculants demonstrated superior efficiency for turbidity and UV254 removal in hairwork wastewater as well as better floc properties compared to polyaluminum chloride. The effects of pH, flocculant dose, and cationic group contents (DS and G) were systematically investigated. Consequently, it was determined that a higher cationic content in both the flocculants led to better flocculation performance as well as increased removal rates of both turbidity and UV254. This was primarily due to improved charge neutralization, which highlighted the preference towards a lower optimal dose. In addition, flocculation performance worsened as the pH level increased. Overall, St-g-PDMC-DQ exhibited similar flocculation performance to St-CTA-DQ. However, the wastewater treated by St-g-PDMC-DQ showed lower residual turbidity than when treated by St-CTA-DQ. This was attributed to the distinct branch chain architecture of St-g-PDMC-DQ, which was beneficial for coagulating the uneasily flocculated contaminants in water, such as smaller-sized colloids and water-soluble organic substances. Flocculant structural factors, specifically charge properties and chain architecture, heavily affected the final flocculation performance.

Flocculation and antimicrobial properties of a cationized starch

In this study, a series of cationized starch-based flocculants (starch-3-chloro-2-hydroxypropyl triethyl ammonium chloride, St-CTA) containing various quaternary ammonium salt groups on the starch backbone were prepared using a simple etherification reaction. All of the prepared starch-based flocculants show effective performance for the flocculation of kaolin suspension, two bacterial (Escherichia coli and Staphylococcus aureus) suspensions, and two contaminant mixtures (kaolin and each bacterium) under most pH conditions. St-CTA with a high substitution degree of CTA demonstrates improved contaminant removal efficiency because of the strong cationic nature of the grafted quaternary ammonium salt groups and the charge naturalization flocculation effect. The antibacterial effects of St-CTA were also evaluated, considering that many quaternary ammonium salt compounds elicit bactericidal effects. Three-dimensional excitation–emission matrix spectra and direct cell morphological observation under scanning electron microscopy reveal that the starch-based flocculants exhibit better antibacterial effects on the Gram-negative bacterium E. coli than on the Gram-positive bacterium S. aureus. The thicker cell wall due to the presence of abundant peptidoglycan and teichoic acids of S. aureus than E. coli explains the uneasy breakage of S. aureus cell wall after being attacked by the cationized starch-based flocculants.

Multifunctional and Regenerable Antibacterial Surfaces Fabricated by a Universal Strategy.

Development of a versatile strategy for antibacterial surfaces is of great scientific interest and practical significance. However, few methods can be used to fabricate antibacterial surfaces on substrates of different chemistries and structures. In addition, traditional antibacterial surfaces may suffer problems related to the attached dead bacteria. Herein, antibacterial surfaces with multifunctionality and regenerability are fabricated by a universal strategy. Various substrates are first deposited with multilayered films containing guest moieties, which can be further used to incorporate biocidal host molecules, β-cyclodextrin (β-CD) derivatives modified with quaternary ammonium salt groups (CD-QAS). The resulting surfaces exhibit strong biocidal activity to kill more than 95% of attached pathogenic bacteria. Notably, almost all the dead bacteria can be easily removed from the surfaces by simple immersion in sodium dodecyl sulfate, and the regenerated surfaces can be treated with new CD-QAS for continued use. Moreover, when another functional β-CD derivative molecule is co-incorporated together with CD-QAS, the surfaces exhibit both functions simultaneously, and neither specific biofunction and antibacterial activity is compromised by the presence of the other. These results thus present a promising way to fabricate multifunctional and regenerable antibacterial surfaces on diverse materials and devices in the biomedical fields.