Xiuqing Wang

De novo synthetic short antimicrobial peptides against cariogenic bacteria

OBJECTIVE Antimicrobial peptides (AMPs) have shown the ability to inhibit planktonic bacteria and biofilms. The objectives of this study were to de novo design and synthesize a series of cationic, amphipathic α-helical AMPs that would be shorter, less cytotoxic, and more potent than existing AMPs against cariogenic bacteria. DESIGN Three short AMPs (GH8, GLLWHLLH-NH2; GH12, GLLWHLLHHLLH-NH2; and GH16, GLLWHLLHHLLHLLHH-NH2) were designed, synthesized and characterized structurally. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against eight major cariogenic bacteria were tested to select the most promising peptide. Scanning electron microscopy (SEM) was used to observe the bacterial membrane after treatment with selected peptides. The bactericidal kinetics, effects on biofilm and cytotoxity were further investigated. RESULTS Of the three AMPs, GH12 had the most balanced structural parameters and a high content of α-helical structure. GH12 had a MIC of 4.0-8.0μg/mL and MBC of 8.0-32.0μg/mL. The corresponding values for the other two AMPs were 2- to 64- fold higher. In time-kill assays, GH12 killed all bacterial strains within 60min at 4- fold MBC. SEM observed lysis and pore formation of the cytomembrane after treatment with GH12. 8.0μg/mL GH12 inhibited Streptococcus mutans biofilm formation. Confocal laser scanning microscopy showed that GH12 effectively reduced the biomass of 1-day-old S. mutans biofilm. Cytotoxicity assays indicated that GH12 showed little toxic effect on the viability of human gingival fibroblasts. CONCLUSION These results indicate that GH12 shows antimicrobial activity against cariogenic bacteria and biofilms in vitro.

A statherin-derived peptide promotes hydroxyapatite crystallization and in situ remineralization of artificial enamel caries

In situ remineralization of hydroxyapatite on a human tooth enamel surface induced by anti-caries bioactive components is an alternative restorative strategy against dental caries. In this study, a novel biomimetic peptide DE-11, inspired by the salivary phosphoprotein statherin, was developed, and it showed beneficial potentials for the restoration of demineralized tooth enamel in vitro. The peptide DE-11 contained the initial six-peptide sequence of N-terminus of statherin extended by a mineralization hydrophilic tail composed of consecutive acidic amino acids capable of adsorbing calcium and phosphate ions. A strong adsorption capacity of DE-11 to hydroxyapatite was confirmed through Langmuir adsorption isotherm experiment and confocal laser scanning microscopy. Then, the nucleation and crystallization of hydroxyapatite due to DE-11 was characterized by scanning and transmission electron microscopy and selected-area electron diffraction. Moreover, the ability of DE-11 to promote the remineralization of initial enamel caries lesions was further evaluated. Initial lesions were created in bovine enamel blocks, which were then exposed to the peptide solution and finally immersed in artificial saliva. After 7 days, a higher percentage of surface microhardness recovery, a lower mineral loss, a shallower lesion depth, and a higher mineral content were found on the surface of the lesion body in the DE-11 group as compared to that in the negative group using surface microhardness testing, polarized light microscopy, and transverse microradiography; this indicated that DE-11 could induce in situ remineralization of hydroxyapatite on the demineralized enamel surface. Overall, these findings suggest that DE-11 is highly promising as a restorative biomaterial for enamel remineralization in the anti-caries applications.

Anti-biofilm and remineralization effects of chitosan hydrogel containing amelogenin-derived peptide on initial caries lesions

Abstract In this study, we have designed a more clinically powerful anti-caries treatment by applying the amelogenin-derived peptide QP5 to the antibacterial carrier material chitosan in a hydrogel (CS-QP5 hydrogel), and characterized its effects on the inhibition of a cariogenic biofilm and the promotion of the remineralization of the initial caries lesions. The results indicated that the CS-QP5 hydrogel sustainably inhibited the growth of the Streptococcus mutans biofilm, lactic acid production and the metabolic activity over a prolonged period of time. Moreover, the CS-QP5 hydrogel promoted the remineralization of early enamel lesions, which were indicated by surface micro-hardness (, polarized light microscopy and transverse microradiography. In conclusion, the CS-QP5 hydrogel shows good potential for caries control in the clinic because of its antibacterial effects as well as the remineralization of initial enamel carious lesions even in a biofilm model over a prolonged period of time.

Tea Polyphenols Functionalized and Reduced Graphene Oxide-ZnO Composites for Selective Pb2+ Removal and Enhanced Antibacterial Activity

New materials with good purification of water quality (heavy metal ions removal and inhibition of bacteria) have increasingly attracted more research attentions. Considering the advantages of zinc oxide (ZnO) and tea polyphenol functionalized and reduced graphene oxide (TPG), the TPG-ZnO composites were prepared under moderate hydrothermal method and characterized by various methods. Lead ions (Pb2+) and Streptococcus mutans (S. mutans) were used to evaluate the adsorption capacity and antimicrobial activity of the TPG-ZnO, respectively. The influencing factors for heavy metal ions removal (pH, contact time), adsorption kinetics, and isotherms were discussed in this article. Furthermore, their antibacterial properties against S. mutans were investigated by counting of colony-forming units (CFU), scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM). Results showed that the novel TPG-ZnO composites presented higher adsorption efficiency for Pb2+ (98.92%) compared with pure ZnO and enhanced antibacterial activity effects (99.99%) towards S. mutans, compared with pure ZnO and TPG (P < 0.05). The TPG-ZnO composites are therefore promising water purification materials for application in high-efficient removal of heavy metal ions and inhibition of bacterial growth.

iTRAQ-based quantitative analysis of age-specific variations in salivary proteome of caries-susceptible individuals

BackgroundHuman saliva is a protein-rich, easily accessible source of potential biomarkers for the diagnosis of oral and systemic diseases. However, little is known about the changes in salivary proteome associated with aging of patients with dental caries. Here, we applied isobaric tags for relative and absolute quantitation (iTRAQ) in combination with multiple reaction monitoring mass spectrometry (MRM-MS) to characterize the salivary proteome profiles of subjects of different ages, presenting with and without caries, with the aim of identifying age-related biomarkers for dental caries.MethodsUnstimulated whole saliva samples were collected from 40 caries-free and caries-susceptible young adults and elderly individuals. Salivary proteins were extracted, reduced, alkylated, digested with trypsin and then analyzed using iTRAQ-coupled LC–MS/MS, followed by GO annotation, biological pathway analysis, hierarchical clustering analysis, and protein–protein interaction analysis. Candidate verification was then conducted using MRM-MS.ResultsAmong 658 salivary proteins identified using tandem mass spectrometry, 435 proteins exhibited altered expression patterns in different age groups with and without caries. Of these proteins, 96 displayed age-specific changes among caries-susceptible adults and elderly individuals, and were mainly associated with salivary secretion pathway, while 110 age-specific proteins were identified among healthy individuals. It was found that the age factor caused significant variations and played an important role in both healthy and cariogenic salivary proteomes. Subsequently, a total of 136 target proteins with complex protein–protein interactions, including 14 age-specific proteins associated with caries, were further successfully validated using MRM analysis. Moreover, non-age-specific proteins (histatin-1 and BPI fold-containing family B member 1) were verified to be important candidate biomarkers for common dental caries.ConclusionsOur proteomic analysis performed using the discovery-through-verification pipeline revealed distinct variations caused by age factor in both healthy and cariogenic salivary proteomes, highlighting the significance of age in the great potential of saliva for caries diagnosis and biomarker discovery.

Antimicrobial peptide GH12 suppresses cariogenic virulence factors of Streptococcus mutans

ABSTRACT Cariogenic virulence factors of Streptococcus mutans include acidogenicity, aciduricity, and extracellular polysaccharides (EPS) synthesis. The de novo designed antimicrobial peptide GH12 has shown bactericidal effects on S. mutans, but its interaction with virulence and regulatory systems of S. mutans remains to be elucidated. The objectives were to investigate the effects of GH12 on virulence factors of S. mutans, and further explore the function mechanisms at enzymatic and transcriptional levels. To avoid decrease in bacterial viability, we limited GH12 to subinhibitory levels. We evaluated effects of GH12 on acidogenicity of S. mutans by pH drop, lactic acid measurement and lactate dehydrogenase (LDH) assay, on aciduricity through survival rate at pH 5.0 and F1F0-ATPase assay, and on EPS synthesis using quantitative measurement, morphology observation, vertical distribution analyses and biomass calculation. Afterwards, we conducted quantitative real-time PCR to acquire the expression profile of related genes. GH12 at 1/2 MIC (4 mg/L) inhibited acid production, survival rate, EPS synthesis, and biofilm formation. The enzymatic activity of LDH and F1F0-ATPase was inhibited, and ldh, gtfBCD, vicR, liaR, and comDE genes were significantly downregulated. In conclusion, GH12 inhibited virulence factors of S. mutans, through reducing the activity of related enzymes, downregulating virulence genes, and inactivating specific regulatory systems.