Biodegradable silver-loaded polycation modified nanodiamonds/polyurethane scaffold with improved antibacterial and mechanical properties for cartilage tissue repairing.

For cartilage tissue repairing, it remains a key challenge to design implant materials with antibacterial activity, proper degradation rate and mechanical property. In this research, antibacterial nanodiamonds (QND, QND-Ag) modified acrylate-terminated polyurethanes (APU) were prepared. By the addition of nanocomposites, the crystallinity of modified APU obviously increased, which indicates a strong interaction between NDs and APU. Tensile and compression tests were carried out to evaluate the improved mechanical properties. Compared with APU, APU(10%PEG)/QND-Ag possessed the increased modulus and strength, a nevertheless slight decrease in elongation at break. Due to the dual actions of contact-killing of cationic polymers and release-killing of the Ag NPs, QND-Ag-containing polyurethane showed excellent antibacterial activity against Staphylococcus aureus. Moreover, APU containing polyethylene glycol showed a significant increase in degradability rates. Consequently, owing to the dual effect of crystallinity and hydrophilicity, our modified APU exhibited the proper degradation rate adaptable to the healing rate of cartilage tissue. Furthermore, the CCK-8 results demonstrated that synthesized samples were low toxic. Therefore, APU(10%PEG)/QND-Ag holds great promise for the application of cartilage tissue repairing.

Novel resin-based dental material with anti-biofilm activity and improved mechanical property by incorporating hydrophilic cationic copolymer functionalized nanodiamond.

There is an increasing clinical need to design dental restorative materials that combine excellent mechanical property and anti-biofilm activity. In the current study, photocurable polycation functionalized nanodiamond (QND) was synthesized and proposed as novel filler for dental resins. By reason of increased repulsive force between nanoparticles and enhanced compatibility with resin matrix, QND dispersed uniformly in reinforced resins, which would help to transfer stress and deformation from the matrix to fillers more efficiently, resulting in a significant improvement in mechanical properties. Notably, the Vickers's hardness, flexural strength and flexural modulus of resins containing 1.0 wt% QND were 44.5, 36.1 and 41.3% higher than that of control, respectively. The antibacterial activity against Streptococcus mutans (S. mutans) showed that QND-incorporated resins produced anti-adhesive property due to their hydrophilic surfaces and could suppress bacterial growth as a result of the contact-killing effect of embedded nanocomposites. As the synergistic effect of anti-adhesive and bactericidal performance, resins loading 1.0~1.5 wt% QNDs displayed excellent anti-biofilm activity. Meanwhile, the results of macrophage cytotoxicity showed that the proliferation of RAW 264.7 cells remained 84.3%, even at a concentration of 1.0 wt% QNDs after 7-day incubation. Therefore, the QND-containing dental resin with the combination of high mechanical property, bacteria-repellent capability and antibacterial performance holds great potential as a restorative material based on this scheme.

Development of a novel resin-based dental material with dual biocidal modes and sustained release of Ag+ ions based on photocurable core-shell AgBr/cationic polymer nanocomposites.

Research on the incorporation of cutting-edge nano-antibacterial agent for designing dental materials with potent and long-lasting antibacterial property is demanding and provoking work. In this study, a novel resin-based dental material containing photocurable core-shell AgBr/cationic polymer nanocomposite (AgBr/BHPVP) was designed and developed. The shell of polymerizable cationic polymer not only provided non-releasing antibacterial capability for dental resins, but also had the potential to polymerize with other methacrylate monomers and prevented nanoparticles from aggregating in the resin matrix. As a result, incorporation of AgBr/BHPVP nanocomposites did not adversely affect the flexural strength and modulus but greatly increased the Vicker's hardness of resin disks. By continuing to release Ag+ ions without the impact of anaerobic environment, resins containing AgBr/BHPVP nanoparticles are particularly suitable to combat anaerobic cariogenic bacteria. By reason of the combined bactericidal effect of the contact-killing cationic polymers and the releasing-killing Ag+ ions, AgBr/BHPVP-containing resin disks had potent bactericidal activity against S. mutans. The long-lasting antibacterial activity was also achieved through the sustained release of Ag+ ions due to the core-shell structure of the nanocomposites. The results of macrophage cytotoxicity showed that the cell viability of dental resins loading less than 1.0 wt% AgBr/BHPVP was close to that of neat resins. The AgBr/BHPVP-containing dental resin with dual bactericidal capability and long term antimicrobial effect is a promising material aimed at preventing second caries and prolonging the longevity of resin composite restorations.

Nano-Fibrous Biopolymer Hydrogels via Biological Conjugation for Osteogenesis.

Nanostructured biopolymer hydrogels have great potential in the field of drug delivery and regenerative medicine. In this work, a nano-fibrous (NF) biopolymer hydrogel was developed for cell growth factors (GFs) delivery and in vitro osteogenesis. The nano-fibrous hydrogel was produced via biological conjugation of streptavidin functionalized hyaluronic acid (HA-Streptavidin) and biotin terminated star-shaped poly(ethylene glycol) (PEG-Biotin). In the present work, in vitro gelation, mechanical properties, degradation and equilibrium swelling of the NF hydrogel were examined. The potential application of this NF gel scaffold in bone tissue engineering was confirmed by encapsulation behavior of osteoblasts. Osteoblasts seeded directly in NF gel scaffold containing cell growth factor, e.g. bone morphogenetic protein 2 (BMP-2), was to mimic the in vivo microenvironment in which cells interface biomaterials and interact with BMP-2. In combination with BMP-2, the NF hydrogel exhibited beneficial effects on osteoblast activity and differentiation, which suggested a promising future for local treatment of pathologies involving bone loss.

Poly(Lysine)-Derived Carbon Quantum Dots Conquer Enterococcus faecalis Biofilm-Induced Persistent Endodontic Infections.

Introduction: Persistent endodontic infections (PEIs) mediated by bacterial biofilm mainly cause persistent periapical inflammation, resulting in recurrent periapical abscesses and progressive bone destruction. However, conventional root canal disinfectants are highly damaging to the tooth and periodontal tissue and ineffective in treating persistent root canal infections. Antimicrobial materials that are biocompatible with apical tissues and can eliminate PEIs-associated bacteria are urgently needed. Methods: Here, ε-poly (L-lysine) derived carbon quantum dots (PL-CQDs) are fabricated using pyrolysis to remove PEIs-associated bacterial biofilms. Results: Due to their ultra-small size, high positive charge, and active reactive oxygen species (ROS) generation capacity, PL-CQDs exhibit highly effective antibacterial activity against Enterococcus faecalis (E. faecalis), which is greatly dependent on PL-CQDs concentrations. 100 µg/mL PL-CQDs could kill E. faecalis in 5 min. Importantly, PL-CQDs effectively achieved a reduction of biofilms in the isolated teeth model, disrupting the dense structure of biofilms. PL-CQDs have acceptable cytocompatibility and hemocompatibility in vitro and good biosafety in vivo. Discussion: Thus, PL-CQDs provide a new strategy for treating E. faecalis-associated PEIs.

Mussel-inspired polymer with catechol and cationic Lys functionalities for dentin wet bonding.

Mussels can form tough and long-lasting adhesions to organic and inorganic surfaces in saline and impactive severe aquatic environments. Similar to mussel adhesion, dentin bonding occurs in a wet environment. However, unlike mussels, it is difficult to achieve long-lasting bonds with dentin. Moreover, water is considered a major hindrance in dentin bonding. Inspired by the synergistic effect of cationic lysine (Lys) and catechol on the elimination of the hydration layer during mussel adhesion, a catechol- and Lys-functionalized polymerizable polymer (catechol-Lys-methacrylate [CLM]) was synthesized to replicate the complex synergy between amino acids and catechol. The bond-promoting potential of 5 â€‹mg/mL CLM primer was confirmed using an in vitro wet dentin-bonding model, which was characterized by an improvement in bond strength and durability. CLM can adhere to wet demineralized dentin, with Lys acting as a molecular vanguard to expel water. Subsequently, a myriad of interfacial interactions can be obtained by introducing the catechol group into the interface. Additionally, tough and long-lasting adhesion, similar to that formed by mussels, can be achieved by grafting CLM onto type I collagen via covalent bonds, hydrogen bonds, Van der Waals interactions, and cation-π interactions, which can enhance the mechanical and chemical stability of collagen, increase the enzymatic resistance of collagen, and provide additional physical/chemical adhesion to dentin bonds. Catechol- and cationic Lys-functionalized polymers can improve the stability of the resin-dentin interface under wet conditions.

Photothermal-enhanced antibacterial and antioxidant hydrogel dressings based on catechol-modified chitosan-derived carbonized polymer dots for effective treatment of wound infections.

Bacterial infection and excessive reactive oxygen species (ROS) remain challenging factors contributing to the delayed healing of chronic wounds. Although various antibacterial and antioxidant hydrogel dressings have been developed to accelerate wound healing, multifunctional hydrogels fabricated by rationally designing and introducing carbonized polymer dots (CPDs) have rarely been reported. Herein, inspired by the mussel biomimetic approach, we synthesized 3,4-dihydroxybenzaldehyde functionalized chitosan (DFC), and then the polymeric precursor was pyrolyzed into CPDs with abundant amino and catechol groups on the surface, which endowed it with a highly positively charged surface that could activate the photothermal effect under near-infrared (NIR) light irradiation. Finally, the nanocomposite hydrogel (PVA@CPDs) was simply constructed by directly mixing polyvinyl alcohol (PVA) with CPDs, utilizing the freeze-thaw cycle method to form a gel, in which, CPDs as a center of polyfunctional nanoparticles drove the formation of PVA microcrystalline crosslinking and endowed the PVA substrate with versatile functionalities. Remarkable and comprehensive improvements in the swelling behavior, mechanical properties and adhesive strength of the hydrogel could be conveniently achieved with the suitable loading of CPDs. The in vitro experiments demonstrated that the PVA@CPDs hydrogel presented broad-spectrum and rapid bactericidal activity, concurrently acting as an effective antioxidant being able to scavenge free radicals. In addition, no obvious cytotoxicity was observed for the multifunctional hydrogel after incubation with L02 cells. In vivo evaluation in an infected full-thickness skin wound model demonstrated that the PVA@CPDs hydrogel promoted wound closure without any side effects. As a consequence, the current work manifests a facile yet versatile strategy to develop effective and biocompatible multifunctional hydrogel dressings for bacteria-infected wound healing.

Antibacterial effects of three experimental quaternary ammonium salt (QAS) monomers on bacteria associated with oral infections.

The aim of this study was to test the antibacterial effects of three experimental quaternary ammonium salt monomers in order to evaluate their potential applications as dental materials. In vitro susceptibility testing of the monomers was performed by the broth dilution method on bacteria associated with oral infections: Streptococcus mutans ATCC 25175, Actinomyces viscosus ATCC 15987, Staphylococcus aureus ATCC 29213 and Lactobacillus casei ATCC 393. The time-kill kinetics of the monomer with relatively higher antibacterial activity against S. mutans were also investigated. It was found that all the tested bacteria strains were susceptible to the three monomers, among which methacryloxylethyl cetyl ammonium chloride (DMAE-CB) exhibited the lowest minimal inhibitory concentrations, ranging from 1.2 to 4.8 microg/ml. The time-kill curve showed that DMAE-CB achieved 99.44% killing at 19.2 microg/ml (4 times the minimal bactericidal concentration) against S. mutans after 1 min and 100% killing within 10 min of contact. This result indicates that the quaternary ammonium salt monomer DMAE-CB may be a candidate antibacterial agent for incorporation into dental restorative materials.

Designing of membrane-active nano-antimicrobials based on cationic copolymer functionalized nanodiamond: Influence of hydrophilic segment on antimicrobial activity and selectivity.

Designing cationic nano-antimicrobial is a promising solution for combating drug resistant microbes. In this work, hydrophilic cationic copolymer was applied for the surface functionalization of nanodiamonds (NDs) aiming at developing a highly membrane-active nano-antibacterial agent with satisfactory selectivity. As a result, after functionalization, the increased repulsive forces within NDs and interaction with solvent molecular network made the heavily aggregated pristine NDs break down into tiny nanoparticles with particle size ranging from 10 to 100 nm. The improved hydrophilicity and enlarged surface area endowed QND-H5 and QND-H10 a powerful bactericidal capability toward both of Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). In the further bactericidal assessment, it was also demonstrated that the formation of hydrogen bonding between the 2-hydroxyethyl methacrylate (HEMA) side chains and lipid head groups of bacterial membrane also contributed to the enhanced bactericidal ability. Field emission scanning electron microscopy analysis confirmed that as-prepared nano-hybrid acted bactericidal ability via physical nature of outer membrane and cytoplasmic membrane-separating destruction mechanism toward E. coli, which may derive from the hydrogen bonding ability, making them more effective toward bacterial. More importantly, it was found that with just 10% of HEMA, QND-H10 displayed good selectivity toward bacteria over mammalian cells as shown by the high HC50 values with relatively low MIC values, suggesting the great potential application in medical fields. These results indicate that hydrogen bonding is an important element to achieve the desired high antibacterial activity and selectivity, particularly when cationic nano-antibacterial agents are required for medical application.

Fabrication of charge reversible graphene oxide-based nanocomposite with multiple antibacterial modes and magnetic recyclability.

In this work, N-alkylated poly (4-vinylpyridine) (NPVP), a cationic polymer, was firstly applied for the surface modification of Fe3O4 nanoparticles. Then the modified Fe3O4 nanoparticles (Fe3O4@NPVP NPs) combined with graphene oxide (GO) through simple electrostatic binding. Subsequently, deposited Ag nanoparticles (Ag NPs) procedure was carried out to form the multiple antibacterial nanocomposites (GO-Fe3O4@NPVP-Ag). The synthesized nanostructures were well characterized by Transmission Electron Microscope (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared (FT-IR) and Raman spectroscopy. The zeta potentialmeasurement showed that the novel antibacterial nanocomposites exhibited a capacity of reversing its surface charge from negative (physiological pH) to positive (acidic condition). Furthermore, the incorporation of magnetic Fe3O4 NPs into the nanosystems facilitates the cyclic utilization of GO-Fe3O4@NPVP-Ag by magnetic separation. The antibacterial properties of GO-Fe3O4@NPVP-Ag nanocomposites were evaluated with Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Moreover, the cytotoxicity of GO-Fe3O4@NPVP-Ag nanocomposites was studied using NIH-3T3 cells. The results showed that the GO-Fe3O4@NPVP-Ag nanocomposites exhibited excellent antibacterial properties and low cytotoxicity, thus confirming its application as a promising rapid bactericide in various antibacterial fields.

Covalently antibacterial alginate-chitosan hydrogel dressing integrated gelatin microspheres containing tetracycline hydrochloride for wound healing.

An antibacterial and biodegradable composite hydrogel dressing integrated with microspheres is developed for drug delivery and wound healing. The mechanism of gelation is attributed to the Schiff-base reaction between aldehyde and amino groups of oxidized alginate (OAlg) and carboxymethyl chitosan (CMCS). To enhance antibacterial and mechanical properties, tetracycline hydrochloride (TH) loaded gelatin microspheres (GMs) were fabricated by an emulsion cross-linking method, followed by integrating into the OAlg-CMCS hydrogel to produce a composite gel dressing. In vitro gelation time, swelling, degradation, compressive modulus and rheological properties of the gel dressing were investigated as the function of microsphere ratios. With increasing ratios of microspheres from 10 to 40mg/mL, the composite dressing manifested shorter gelation time and lower swelling ratios, as well as higher mechanical strength. Comparing to other formulations, the gel dressing with 30mg/mL microspheres showed more suitable stabilities and mechanical properties for wound healing. Also, in vitro drug release results showed that the loaded TH could be sustained release from the composite gel dressing by contrast with pure hydrogels and microspheres. Furthermore, powerful bacteria growth inhibition effects against Escherichia coli and Staphylococcus aureus suggested that the composite gel dressing, especially the one with 30mg/mL GMs containing TH, has a promising future in treatment of bacterial infection.

Magnetic nanoparticles modified with quaternarized N-halamine based polymer and their antibacterial properties.

We present a simple and facile approach for preparing antibacterial magnetic nanoparticles, which were modified with quaternarized N-halamine based cationic polymer (CPQN). The CPQN functionalized magnetic nanoparticles (MNPs-CPQN) were characterized by X-ray photoelectron spectra, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, and thermogravimetric analysis. Antibacterial properties were investigated with Gram positive bacteria S. aureus and Gram negative bacteria E. coli. Antibacterial assessment showed that the MNPs-CPQN could eliminate nearly 100% of S. aureus and 99.9% of E. coli (10(7-8) CFU/mg nanoparticles) in 5 min, while the bactericide rate of quaternized N-halamine precursor based cationic polymer coated magnetic nanoparticles (MNPs-CPQNP) were 99.6 and 95.2%, respectively. The prepared nanoparticles exhibited a good response to an external magnetic field and had a saturation magnetization of 36.6 emu g(-1). On the basis of their excellent antibacterial properties and magnetic responsiveness, the MNPs-CPQN would be a promising antibacterial material for water disinfection.

An environmentally benign dual action antimicrobial: quaternized chitosan/sodium alga acid multilayer films and silver nanoparticles decorated on magnetic nanoparticles.

There is an urgent need to develop a puissant and environmentally benign antibacterial composite that act via multiple mechanisms to make response to the potentially daunting complexity of the microbial population and microbial antibiotic resistance. In this work, a facile and green approach, layer-by-layer self-assembly technology was applied to assemble polycation quaternized chitosan (QAC) and polyanion sodium alga acid onto magnetic nanoparticles (MNPs). Then silver nanoparticles (AgNPs) with stable and narrow-sized distribution in the range of 25-35 nm were immobilized on the surface of MNPs with L-ascorbic acid as reducing agent and organic multilayers as stabilizer. Through above modification on MNPs, we expected to achieve a green dual antibacterial and recyclable composite via the combined antibacterial action of QAC and AgNPs. Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, transmission electron microscopy, zeta potentials, and dynamic light scattering were employed to confirm the success of the surface functionalization. Silver ion release process was detected by inductively coupled plasma mass spectrometry. Furthermore, the antibacterial properties of the biomaterials against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were studied. The modified MNPs exhibited rapid, efficient, and long-lasting biocidal abilities against E. coli and S. aureus. The magnetic antibacterial composite still showed excellent antibacterial efficiency during five exposure/collection/recycle procedures.

Antibacterial activity of a modified unfilled resin containing a novel polymerizable quaternary ammonium salt MAE-HB.

Resins with strong and long-lasting antibacterial properties are critical for the prevention of secondary dental caries. In this study, we evaluated the antibacterial effect and the underlying mechanism of action of an unfilled resin incorporating 2-methacryloxylethyl hexadecyl methyl ammonium bromide (MAE-HB) against Streptococcus mutans UA159 (S. mutans UA159). MAE-HB was added into unfilled resin at 10 mass%, and unfilled resin without MAE-HB served as the control. Bacterial growth was inhibited on 10%-MAE-HB unfilled resin compared with the control at 1 d, 7 d, 30 d, or 180 d (P < 0.05). The growth inhibitory effect was independent of the incubation time (P > 0.05). No significant differences in the antibacterial activities of eluents from control versus 10%-MAE-HB unfilled resins were observed at any time point (P > 0.05). The number of bacteria attached to 10%-MAE-HB unfilled resin was considerably lower than that to control. Fe-SEM and CLSM showed that 10%-MAE-HB unfilled resin disturbed the integrity of bacterial cells. Expression of the bacterial glucosyltransferases, gtfB and gtfC, was lower on 10%-MAE-HB unfilled resin compared to that on control (P < 0.05). These data indicate that incorporation of MAE-HB confers unfilled resin with strong and long-lasting antibacterial effects against S. mutans.

Antibacterial effect of a resin incorporating a novel polymerizable quaternary ammonium salt MAE-DB against Streptococcus mutans.

The antibacterial properties of resins incorporating MAE-DB and the underlying mechanisms of action were evaluated. Antibacterial effects against Streptococcus mutans were tested using the film contact method, with accumulation and membrane integrity observed by scanning electron microscopy and confocal laser scanning microscopy, respectively. Quantitative PCR was used to determine expression of the S. mutans glucosyltransferase B (gtfB) gene on the surface of resins containing 10% MAE-DB. Bacterial growth was inhibited on resin containing 10% MAE-DB as compared with the control at 1 day, 7 days, 30 days, or 180 days (p < 0.05). For the 10%-MAE-DB resin, no significant differences in bacterial viability were found regardless of the time of incubation (p > 0.05). The number of bacteria attached to resin containing 10% MAE-DB was considerably lower than the control. The proportion of bacteria with damaged cell membranes was increased in the experimental resin over controls. Expression of gtfB was reduced by 10% MAE-DB compared with the control (p < 0.05). These findings demonstrate that MAE-DB can be incorporated into resin materials at sufficient concentrations for long-term antibacterial effects against S. mutans after polymerization by attenuating gtfB expression and impairing membrane integrity.

Antibacterial activity and cytotoxicity of two novel cross-linking antibacterial monomers on oral pathogens.

OBJECTIVES: The antibacterial activity and cytotoxicity of two novel cross-linking antibacterial monomers, 2-methacryloxylethyl dodecyl methyl ammonium bromide (MAE-DB) and 2-methacryloxylethyl hexadecyl methyl ammonium bromide (MAE-HB) were tested in this study. DESIGN: The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of unpolymerized MAE-DB and MAE-HB against eight strains of oral bacteria were tested using a broth dilution test. Time-kill determinations were performed to examine the kinetics of unpolymerized MAE-DB and MAE-HB against Streptococcus mutans UA159 and Streptococcus sanguinis ATCC6715. Bacterial morphology was observed using a field emission scanning electron microscope (Fe-SEM). The cytotoxicity of unpolymerized two new monomers and Bis-GMA on the human gingival fibroblast cell line H2620 was assessed using a methyl thiazolyl tetrazolium assay. RESULTS: Unpolymerized MAE-DB and MAE-HB showed strong bactericidal activity against oral bacteria. The MBC value of MAE-DB ranged from 12.2 to 24.4µg/ml and the MBC value of MAE-HB ranged from 6.2 to 48.8µg/ml. Time-kill determinations indicated that unpolymerized MAE-DB and MAE-HB had rapid killing effects against S. mutans UA159 and S. sanguinis ATCC6715 at the concentration of 4× MBC. The Fe-SEM observation showed that MAE-DB and MAE-HB could disturb the integrity of bacteria and cause lysis of bacterial cells. The median lethal concentration values on human gingival fibroblast for both monomers were between 10 and 20µg/ml, and greater than that of Bis-GMA. CONCLUSIONS: Unpolymerized MAE-DB and MAE-HB monomers had strong bactericidal activity against eight strains of oral bacteria. Their cytotoxicities were less than that of Bis-GMA.

[Preparation and antibacterial activity of quaternary ammonium salt monomers].

OBJECTIVE: To prepare three quaternary ammonium salt (QAS) monomers, and to compare their antibacterial activities against four oral bacterial strains. METHODS: Three antibacterial monomers [methacryloxyethyl benzyl dimethyl ammonium chloride (DMAE-BC), methacryloxyethyl m-chloro benzyl dimethyl ammonium chloride (DMAE-m-CBC), methacryloxyethyl cetyl dimethyl ammonium chloride (DMAE-CB)] were synthesized according to the general structure of target monomers. Their antibacterial effects were investigated using the broth dilution test on Gram-positive and Gram-negative bacterial strains (Streptococcus mutans, Streptococcus sanguis, Porphyromonas gingivalis, Prevotella melaninogenica ). RESULTS: Three different monomers were successfully obtained. All the tested bacterial strains were susceptible to the three monomers, among which DMAE-CB exhibited the lowest minimal inhibitory concentrations (MIC) ranging from 1.2 to 4.8 mg/L. CONCLUSIONS: All these three QAS monomers have different antibacterial activities against four oral bacteria strains. The data indicate that DMAE-CB may be a candidate antibacterial agent for oral infectious diseases.