Novel lactoferrin-conjugated gallium complex to treat Pseudomonas aeruginosa wound infection.

Pseudomonas aeruginosa is one of the leading causes of opportunistic infections such as chronic wound infection that could lead to multiple organ failure and death. Gallium (Ga3+) ions are known to inhibit P. aeruginosa growth and biofilm formation but require carrier for localized controlled delivery. Lactoferrin (LTf), a two-lobed protein, can deliver Ga3+ at sites of infection. This study aimed to develop a Ga-LTf complex for the treatment of wound infection. The characterisation of the Ga-LTf complex was conducted using differential scanning calorimetry (DSC), Infra-Red (FTIR) and Inductive Coupled Plasma Optical Emission Spectrometry (ICP-OES). The antibacterial activity was assessed by agar disc diffusion, liquid broth and biofilm inhibition assays using the colony forming units (CFUs). The healing capacity and biocompatibility were evaluated using a P.aeruginosa infected wound in a rat model. DSC analyses showed thermal transition consistent with apo-lactoferrin; FTIR confirmed the complexation of gallium to lactoferrin. ICP-OES confirmed the controlled local delivery of Ga3+. Ga-LTf showed a 0.57 log10 CFUs reduction at 24 h compared with untreated control in planktonic liquid broth assay. Ga-LTf showed the highest antibiofilm activity with a 2.24 log10 CFUs reduction at 24 h. Furthermore, Ga-LTf complex is biocompatible without any adverse effect on brain, kidney, liver and spleen of rats tested in this study. Ga-LTf can be potentially promising novel therapeutic agent to treat pathogenic bacterial infections.

Prevalence of vancomycin-resistant Enterococci in India between 2000 and 2022: a systematic review and meta-analysis.

BACKGROUND: Vancomycin-resistant Enterococci (VRE) infections are recurrently reported in different parts of India in the last two decades. However, an up-to-date, countrywide information concerning the prevalence and the rate of VRE in India is limited and hence this study aimed to estimate the pooled prevalence of VRE in India. METHODS: A literature search was performed using various databases. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed throughout. Cross-sectional studies reporting the prevalence of VRE in India from human samples whereby at least two Enterococci were isolated between 1 January 2000 and 31 December 2022 were sought for inclusion. Data were extracted and analysed using Microsoft Excel and Comprehensive Meta-analysis version 4, respectively. RESULTS: Nineteen studies were included in the analyses. A collective total of 3683 Enterococci isolates were examined, of which 368 were VRE strains. The pooled prevalence of VRE in India was calculated at 12.4% (95% CI: 8.6-17.5; Q = 189.69; I2 = 90.51%; p = < 0.001). E. faecalis was the most frequently isolated species (1450 [39.37%]) followed by E. faecium (724 [19.66%]). Amongst the VRE strains, E. faecium was the most prevalent (214 [58.15%]) followed by E. faecalis (134 [36.41%]). An upsurge in the rate of VRE infections was observed in India over time: VRE prevalence was estimated at 4.8% between 2000 and 2010 and 14.1% between 2011 and 2020. CONCLUSION: This study presents the most up-to-date information on the rate of VRE infections in India. Though lower than the findings for some less developed countries, VRE prevalence in India is notable and on the rise.

Antibacterial, remineralising and matrix metalloproteinase inhibiting scandium-doped phosphate glasses for treatment of dental caries.

OBJECTIVES: Antibiotic resistance is increasingly a growing global threat. This study aimed to investigate the potential use of newly developed scandium-doped phosphate-based glasses (Sc-PBGs) as an antibacterial and anticariogenic agent through controlled release of Sc3+ ions. METHODS: Sc-PBGs with various calcium and sodium oxide contents were produced and characterised using thermal and spectroscopic analysis. Degradation behaviour, ion release, antibacterial action against Streptococcus mutans, anti-matrix metalloproteinase-2 (MMP-2) activity, remineralisation potential and in vivo biocompatibility were also investigated. RESULTS: The developed glass system showed linear Sc3+ ions release over time. The released Sc3+ shows statistically significant inhibition of S. mutans biofilm (1.2 log10 CFU reduction at 6 h) and matrix metalloproteinase-2 (MMP-2) activity, compared with Sc-free glass and positive control. When Sc-PBGs were mounted alongside enamel sections, subjected to acidic challenges, alternating hyper- and hypomineralisation layers consistent with periods of re- and demineralisation were observed demonstrating their potential remineralising action. Furthermore, Sc-PBGs produced a non-toxic response when implanted subcutaneously for 2 weeks in Sprague Dawley rats. SIGNIFICANCE: Since Sc3+ ions might act on various enzymes essential to the biological mechanisms underlying caries, Sc-PBGs could be a promising therapeutic agent against cariogenic bacteria.

Quantifying the demineralisation of enamel using a hyperspectral camera measuring fluorescence loss.

BACKGROUND: The gold standard for quantifying mineral loss of enamel is transverse microradiography (TMR) and is complimented by the non-destructive quantitative light induced fluorescence (QLF) which measures changes in autofluorescence. Fluorescence loss has been shown to correlate with mineral loss. Building upon the established method, the use of hyperspectral fluorescence imaging (HI) allows the capture of a broader range of wavelengths to quantify fluorescence changes more accurately. METHODS: Bovine Enamel was demineralised within the dual constant depth film fermenter over 14 days and analysed using TMR, QLF and HI. The mineral change values were compared using Pearson's Correlation Coefficient. RESULTS: The analysis showed a statistically significant correlation that was equal between TMR and HI (r = 0.844) and TMR and QLF (r = 0.844), but weaker between QLF and HI (r = 0.811). CONCLUSIONS: The correlations indicate that HI is a promising valid non-destructive method for quantifying mineral loss from bovine enamel that is as accurate as QLF and complements TMR.

The cariogenic effect of starch on oral microcosm grown within the dual constant depth film fermenter.

Evidence on the link between starch intake and caries incidence is conflicting, therefore the cariogenicity of starch compared with sucrose was explored using a dual Constant Depth Film Fermenter (dCDFF) biotic model system. Bovine enamel discs were used as a substrate and the dCDFF was inoculated using human saliva. CDFF units were supplemented with artificial saliva growth media at a constant rate to mimic resting salivary flow rate over 14 days. The CDFF units were exposed to different conditions, 2% sucrose or 2% starch 8 times daily and either no additional fluoride or 1450 ppm F- twice daily. Bovine enamel discs were removed at intervals (days 3, 7, 10 and 14) for bacterial enumeration and enamel analysis using Quantitative Light Induced Fluorescence (QLF) and Transverse Microradiography (TMR). Results showed that in the absence of fluoride there was generally no difference in mineral loss between enamel exposed to either sucrose or starch when analysed using TMR and QLF (P > 0.05). In the presence of fluoride by day 14 there was significantly more mineral loss under starch than sucrose when analysed with TMR (P < 0.05). It was confirmed that starch and sucrose are similarly cariogenic within the dCDFF in the absence of fluoride. With the aid of salivary amylase, the bacteria utilise starch to produce an acidic environment similar to that of bacteria exposed to sucrose only. In the presence of fluoride, starch was more cariogenic which may be due to the bacteria producing a more hydrophobic intercellular matrix lowering the penetration of fluoride through the biofilm. This is significant as it indicates that the focus on sugars being the primary cause of caries may need re-evaluating and an increase in focus on carbohydrates is needed as they may be similarly cariogenic as sugars if not more so.

Evidence of an in vitro Coupled Diffusion Mechanism of Lesion Formation within Microcosm Dental Plaque.

The purpose of this study was to determine whether or not the dual constant-depth film fermenter (dCDFF) is able to produce caries-like enamel lesions and to ascertain further information regarding the performance of this fully functional biological caries model. Conditions were defined by the continuation (CF) or cessation (FF) of a saliva-type growth medium supply during 50-mM sucrose exposures (8 times daily). Hydroxyapatite (n = 3) and bovine enamel (n = 3) substrata were included within each condition and samples extracted after 2, 4, 8, and 16 days. Community profiles were generated for fastidious anaerobes, Lactobacillus spp., Streptococcus spp., mutans streptococci (MS), and Veillonella spp. using selective culture techniques and enamel demineralisation assessed by transverse microradiography. Results demonstrated that the dCDFF model is able to produce caries-like enamel lesions with a high degree of sensitivity where reduced ionic strength within the FF condition increased surface layer mineral deposition. Between conditions, biofilm communities did not differ significantly, although MS in the biofilms extracted from the FF condition rose to a higher proportion (by 1.5 log10 units), and Veillonella spp. were initially greater within the CF condition (by 2.5 log10 units), indicating an enhanced ability for the clearance of low-pKa acids following exposures to sucrose. However, both conditions retained the ability for caries-like lesion formation.

In silico analyses of heparin binding proteins expression in human periodontal tissues.

BACKGROUND: Periodontitis is described as a group of inflammatory diseases of the gingiva and supporting structures of the periodontium. The accumulation of plaque bacteria, which include putative periodontal pathogens, is known to initiate the disease but the host immune response is the major contributing factor for destruction of periodontal tissues. Proteins that bind to heparin heparin-binding protein (HBPs) play important roles in health and disease and interact with each other via networks known as 'heparin interactomes'. This study aimed at evaluating published datasets of HBPs and its role in periodontitis. METHODS: To elucidate the role of HBPs in periodontitis, bioinformatics analyses of published data was used. In silico analyses of published datasets were used to construct a putative HBPs interactome using an online database resource, 'STRING' (Search Tool for the Retrieval of Interacting Genes). RESULTS: PubMed searches identified 249 genes that were up regulated and 146 genes that were down regulated in periodontal disease, compared with periodontal disease-free gingival samples. In silico analyses using published datasets revealed 25 up-regulated and 23 down-regulated HBPs in periodontitis. Of these HBPs; chemokines, such as CXCL12 was up regulated where as some of the matrixmetalloproteinases (MMPs; MMP-2 and MMP9) were up-regulated while MMP-14 was down regulated. CONCLUSIONS: The results indicate that HBP analyses will provide multiple targets for the biological mechanisms underlying periodontal disease (such as MMPs, cytokines and chemokines) that will have important clinical implications in the future drug design and management of periodontal disease.

Evaluation of the co-existence of the red fluorescent plaque bacteria P. gingivalis with S. gordonii and S. mutans in white spot lesion formation during orthodontic treatment.

BACKGROUND: Early detection of white spot lesions (WSLs) around brackets during orthodontic treatment is important for treatment and prevention. But it is unclear whether red fluorescent plaque (RFP) bacteria Porphyromonas gingivalis and its co-existence with Streptococcus mutans and Streptococcus gordonii has any significant influence on this. Therefore the role of this bacterial co existence and WSLs formation during one year of fixed orthodontic therapy was evaluated. METHODS: Fourteen 12 to 22 year old (mean 15 ± 3 years) consecutive patients attending the University of Liverpool dental hospital were recruited for this study. Quantitative Light-induced Fluorescence (QLF) was used to identify RFP and enamel demineralisation, respectively, on anterior labial surfaces before and after placement of fixed orthodontic appliances. Bacterial composition was determined by denaturing gradient gel electrophoresis (DGGE) following nested PCR amplification of the 16S rRNA V2-V3 hypervariable region. RESULTS: WSLs were recorded on 4.2% of tooth surfaces and WSL development was not associated with RFP bacteria P. gingivalis presence. Differences in RFP bacteria P. gingivalis presence with S. mutans and S. gordonii, were observed before and after appliance placement. Intra subject changes in plaque flora between visits were not significantly associated with WSL development (p > 0.05). However, DGGE profiles indicated that apart from S. mutans, S. gordonii might also have a role in human enamel demineralisation. CONCLUSIONS: Fixed orthodontic brackets in adolescents may play a role in altering bacterial composition around brackets during orthodontic treatment and it is plausible that S. gordonii also have a role in human enamel demineralisation. Combinatorial approach of QLF technology and DGGE may be useful in determining bacterial composition during orthodontic therapy which could inform clinical interventions.

Potential use of gallium-doped phosphate-based glass material for periodontitis treatment.

This study aimed at evaluating the potential effect of gallium-incorporated phosphate-based glasses towards periodontitis-associated bacteria, Porphyromonas gingivalis, and matrix metalloproteinase-13. Periodontitis describes a group of inflammatory diseases of the gingiva and supporting structures of the periodontium. They are initiated by the accumulation of plaque bacteria, such as the putative periodontal pathogen Porphyromonas gingivalis, but the host immune response such as elevated matrix metalloproteinases are the major contributing factor for destruction of periodontal tissues. Antibacterial assays of gallium-incorporated phosphate-based glasses were conducted on Porphyromonas gingivalis ATCC 33277 using disc diffusion assay on fastidious anaerobe agar and liquid broth assay in a modified tryptic soy broth. In vitro study investigated the effect of gallium on purified recombinant human matrix metalloproteinase-13 activity using matrix metalloproteinase assay kit. In vivo biocompatibility of gallium-incorporated phosphate-based glass was evaluated in rats as subcutaneous implants. Antibacterial assay of gallium displayed activity against Porphyromonas gingivalis (inhibition zone of 22 ± 0.5 mm compared with 0 mm for control glass, c-PBG). Gallium in the glass contributed to growth inhibitory effect on Porphyromonas gingivalis (up to 1.30 reductions in log 10 values of the viable counts compared with control) in a modified tryptic soy broth. In vitro study showed gallium-incorporated phosphate-based glasses inhibited matrix metalloproteinase activity significantly (p ≤ 0.01) compared with c-PBG. Evaluation of in vivo biocompatibility of gallium-incorporated phosphate-based glasses in rats showed a non-toxic and foreign body response after 2 weeks of implantation. The results indicate that gallium ions might act on multiple targets of biological mechanisms underlying periodontal disease. Moreover, gallium-incorporated phosphate-based glasses are biocompatible in a rat model. The findings warrant further investigation and will have important clinical implications in the future treatment and management of periodontitis.

Antibacterial effect of gallium and silver on Pseudomonas aeruginosa treated with gallium-silver-phosphate-based glasses.

Gallium and silver incorporated phosphate-based glasses were evaluated for antibacterial effect on the growth of Pseudomonas aeruginosa, which is a leading cause of opportunistic infections. The glasses were produced by conventional melt quenching methods at 1100°C for 1 h. Glass degradation studies were conducted by weight loss method. Disc diffusion assay and cell viability assay displayed statistically significant (p ≤ 0.0005) effect on P. aeruginosa growth which increased with decreasing calcium content in the glasses. The gallium ion release rates (1.83, 0.69 and 0.48 ppm·h(-1)) and silver ion release rates (2.97, 2.84 and 2.47 ppm·h(-1)) were found to account for this variation. Constant depth film fermentor was used to evaluate the anti-biofilm properties of the glasses. Both gallium and silver in the glass contributed to biofilm growth inhibitory effect on P. aeruginosa (up to 2.68 reduction in log 10 values of the viable counts compared with controls). The glasses were found to deliver gallium and silver in a controlled way and exerted cumulative antibacterial action on planktonic and biofilm growth of P. aeruginosa. The antibacterial, especially anti-biofilm, properties of the gallium and silver incorporated phosphate-based glasses make them a potential candidate to combat infections caused by P. aeruginosa.

Characterisation of phosphate coacervates for potential biomedical applications.

In this study, amorphous (Na2O)x(CaO)0.50- x(P2O5)0.50·yH2O (where x = ~0.15 and y = ~3) samples were prepared by a coacervate method. Thermal analysis showed that two types of water molecules were present in the coacervate structures: one type loosely bound and the other part of the phosphate structure. Structural studies using Fourier transform infrared spectroscopy (FTIR) and X-ray total diffraction revealed the samples to have very similar structures to melt-quenched glasses of comparable composition. Furthermore, no significant structural differences were observed between samples prepared using calcium nitrate as the calcium source or those prepared from calcium chloride. A sample containing ~1 mol% Ag2O was prepared to test the hypothesis that calcium phosphate coacervate materials could be used as delivery agents for antibacterial ions. This sample exhibited significant antibacterial activity against the bacterium Psuedomonas aeruginosa. FTIR data revealed the silver-doped sample to be structurally akin to the analogous silver-free sample.

Effect of novel antibacterial gallium-carboxymethyl cellulose on Pseudomonas aeruginosa.

Gallium has emerged as a new therapeutic agent due partly to the scarcity in development of new antibiotics. In this study, a novel antibacterial gallium exchanged carboxymethyl cellulose (Ga-CMC) has been developed and tested for the susceptibility on a common bacteria, Pseudomonas aeruginosa. The results show that an increase in average molecular weight (MW) from 90 k, 250 k to 700 k of Ga-CMC caused a decrease in antimicrobial activity against planktonic P. aeruginosa. Gallium loading of the Ga-CMC (250 k) samples was altered by varying the amount of functionality (0.7, 0.9 and 1.2 acid groups per mole of carbohydrate) which affected also its antimicrobial activity against planktonic P. aeruginosa. Further, the ability to prevent the growth of biofilms of P. aeruginosa was tested on MW = 250 k samples with 0.9 acid groups per mole of carbohydrate as this sample showed the most promising activity against planktonic P. aeruginosa. Gallium was found to reduce biofilm growth of P. aeruginosa with a maximum effect (0.85 log(10) CFU reduction compared to sodium-carboxymethyl cellulose, Na-CMC) after 24 h. Results of the solubility and ion exchange studies show that this compound is suitable for the controlled release of Ga(3+) upon their breakdown in the presence of bacteria. SEM EDX analysis confirmed that Ga(3+) ions are evenly exchanged on the cellulose surface and systematic controls were carried out to ensure that antibacterial activity is solely due to the presence of gallium as samples intrinsic acidity or nature of counterion did not affect the activity. The results presented here highlight that Ga-CMC may be useful in controlled drug delivery applications, to deliver gallium ions in order to prevent infections due to P. aeruginosa biofilms.

Role of gallium and silver from phosphate-based glasses on in vitro dual species oral biofilm models of Porphyromonas gingivalis and Streptococcus gordonii.

Phosphate-based glasses (PBGs) are excellent controlled delivery agents for antibacterial ions such as silver and gallium. The aim of this study was to assess the potential utility of novel PBGs combining both gallium and silver for use in periodontal therapy. To this end, an in vitro biofilm model with the putative periodontal pathogen, Porphyromonas gingivalis, and an initial colonizer, Streptococcus gordonii, was established. The effect of increasing calcium content in gallium-silver-doped PBG on the susceptibility of P. gingivalis was examined. A decrease in degradation rates (30.34, 25.19, 21.40 µg mm(-2) h(-1)) with increasing PBG calciumcontent (10, 11, 12 mol.% respectively) was observed, correlating well with gallium and silver ion release and antimicrobial activity against planktonic P. gingivalis (approximately 5.4log(10) colony-forming units (CFU) reduction after 24h by the C10 glass compared with controls) and S. gordonii (total growth inhibition after 32h by C10, C11 and C12 glasses compared with controls). The most potent PBG (C10) was evaluated for its ability to inhibit the biofilm growth of P. gingivalis in a newly established constant-depth film fermentor model. The simultaneous release of silver and gallium from the glass reduced P. gingivalis biofilm growth with a maximum effect (1.92log(10) CFU reduction) after 168 h. Given the emergence of antibiotic-resistant bacteria and dearth of new antibiotics in development, the glasses, especially C10, would offer effective alternatives to antibiotics or may complement current therapies through controlled, localized delivery of gallium and silver ions at infected sites in the oral cavity.

Poly(3-hydroxybutyrate) multifunctional composite scaffolds for tissue engineering applications.

Poly(3-hydroxybutyrate) (P(3HB)) foams exhibiting highly interconnected porosity (85% porosity) were prepared using a unique combination of solvent casting and particulate leaching techniques by employing commercially available sugar cubes as porogen. Bioactive glass (BG) particles of 45S5 Bioglass grade were introduced in the scaffold microstructure, both in micrometer ((m-BG), <5 microm) and nanometer ((n-BG), 30 nm) sizes. The in vitro bioactivity of the P(3HB)/BG foams was confirmed within 10 days of immersion in simulated body fluid and the foams showed high level of protein adsorption. The foams interconnected porous microstructure proved to be suitable for MG-63 osteoblast cell attachment and proliferation. The foams implanted in rats as subcutaneous implants resulted in a non-toxic and foreign body response after one week of implantation. In addition to showing bioactivity and biocompatibility, the P(3HB)/BG composite foams also exhibited bactericidal properties, which was tested on the growth of Staphylococcus aureus. An attempt was made at developing multifunctional scaffolds by incorporating, in addition to BG, selected concentrations of Vitamin E or/and carbon nanotubes. P(3HB) scaffolds with multifunctionalities (viz. bactericidal, bioactive, electrically conductive, antioxidative behaviour) were thus produced, which paves the way for next generation of advanced scaffolds for bone tissue engineering.

Impaired bacterial attachment to light activated Ni-Ti alloy.

Ni-Ti alloy due to its unique mechanical properties, is used for many types of implants. Failure of these implants can be attributed to many different factors; however infections are a common problem. In this paper, the attachment of the bacteria, Staphylococcus aureus, to the Ni-Ti surface modified by a range of processes with and without of light activation (used to elicit antimicrobial properties of materials) was assessed and related to different surface characteristics. Before the light activation the number of bacterial colony forming units was the greatest for the samples thermally oxidised at 600°C. This sample and the spark oxidised samples showed the highest photocatalytic activity but only the thermally oxidised samples at 600°C showed a significant drop of S. aureus attachment. The findings in this study indicate that light activation and treating samples at 600°C is a promising method for Ni-Ti implant applications with inherent antimicrobial properties. Light activation was shown to be an effective way to trigger photocatalytic reactions on samples covered with relatively thick titanium dioxide via accumulation of photons in the surface and a possible increase in defects which may result in free oxygen. Moreover, light activation caused an increase in the total surface energy.

Effect of nanoparticulate bioactive glass particles on bioactivity and cytocompatibility of poly(3-hydroxybutyrate) composites.

This work investigated the effect of adding nanoparticulate (29 nm) bioactive glass particles on the bioactivity, degradation and in vitro cytocompatibility of poly(3-hydroxybutyrate) (P(3HB)) composites/nano-sized bioactive glass (n-BG). Two different concentrations (10 and 20 wt %) of nanoscale bioactive glass particles of 45S5 Bioglass composition were used to prepare composite films. Several techniques (Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray) were used to monitor their surface and bioreactivity over a 45-day period of immersion in simulated body fluid (SBF). All results suggested the P(3HB)/n-BG composites to be highly bioactive, confirmed by the formation of hydroxyapatite on material surfaces upon immersion in SBF. The weight loss and water uptake were found to increase on increasing bioactive glass content. Cytocompatibility study (cell proliferation, cell attachment, alkaline phosphatase activity and osteocalcin production) using human MG-63 osteoblast-like cells in osteogenic and non-osteogenic medium showed that the composite substrates are suitable for cell attachment, proliferation and differentiation.

Characterization of carbon nanotube (MWCNT) containing P(3HB)/bioactive glass composites for tissue engineering applications.

Poly(3-hydroxybutyrate) (P(3HB)) composites with bioactive glass particles and multiwall carbon nanotubes (MWCNTs) were prepared and used to identify whether the electrical properties of MWCNTs can be used to detect the bioactivity of P(3HB)/bioactive glass composites. The presence of MWCNTs (2-7 wt.%) increased the surface roughness of the composites. The presence of MWCNTs in low quantity enhanced MG-63 osteoblast-like cell attachment and proliferation compared to composites with higher concentration of MWCNTs. Current-voltage measurements demonstrated that the electrical resistance of the composites containing bioactive glass particles decreased over a 45-day immersion period in SBF, whereas composites without bioactive glass showed no significant change over the same period.

Development of remineralizing, antibacterial dental materials.

Light curable methacrylate dental monomers containing reactive calcium phosphate filler (monocalcium phosphate monohydrate (MCPM) with particle diameter of 29 or 90microm) and beta-tricalcium phosphate (beta-TCP) at 1:1 weight ratio in a powder:liquid ratio (PLR) of 1:1 or 3:1 and chlorhexidine diacetate (0 or 5 wt.%), were investigated. Upon light exposure, approximately 90% monomer conversion was gained irrespective of the formulation. Increasing the PLR promoted water sorption by the set material, induced expansion and enhanced calcium, phosphate and chlorhexidine release. Concomitantly, a decline in compressive and biaxial flexural strengths occurred. With a reduction in MCPM particle diameter, however, calcium and phosphate release was reduced and less deterioration in strength observed. After 24h, the remaining MCPM had reacted with water and beta-TCP, forming, within the set materials, brushite of lower solubility. This provided a novel means to control water sorption, component release and strength properties. Measurable chlorhexidine release was observed for 6weeks. Both diffusion rate and total percentage of chlorhexidine release decreased with lowering PLR or by adding buffer to the storage solutions. Higher chlorhexidine release was associated with reduced bacterial growth on agar plates and in a biofilm fermenter. In cell growth media, brushite and hydroxyapatite crystals precipitated on the composite material surfaces. Cells spread on both these crystals and the exposed polymer composite surfaces, indicating their cell compatibility. These formulations could be suitable antibacterial, biocompatible and remineralizing dental adhesives/liners.

Effect of silver-doped phosphate-based glasses on bacterial biofilm growth.

Silver-containing phosphate-based glasses were found to reduce the growth of Pseudomonas aeruginosa and Staphylococcus aureus biofilms, which are leading causes of nosocomial infections. The rates of glass degradation (1.27 to 1.41 microg.mm(-2).h(-1)) and the corresponding silver release were found to account for the variation in biofilm growth inhibitory effect.

Effect of silver content on the structure and antibacterial activity of silver-doped phosphate-based glasses.

Staphylococcus aureus can cause a range of diseases, such as osteomyelitis, as well as colonize implanted medical devices. In most instances the organism forms biofilms that not only are resistant to the body's defense mechanisms but also display decreased susceptibilities to antibiotics. In the present study, we have examined the effect of increasing silver contents in phosphate-based glasses to prevent the formation of S. aureus biofilms. Silver was found to be an effective bactericidal agent against S. aureus biofilms, and the rate of silver ion release (0.42 to 1.22 microg x mm(-2) x h(-1)) from phosphate-based glass was found to account for the variation in its bactericidal effect. Analysis of biofilms by confocal microscopy indicated that they consisted of an upper layer of viable bacteria together with a layer ( approximately 20 microm) of nonviable cells on the glass surface. Our results showed that regardless of the silver contents in these glasses (10, 15, or 20 mol%) the silver exists in its +1 oxidation state, which is known to be a highly effective bactericidal agent compared to that of silver in other oxidation states (+2 or +3). Analysis of the glasses by (31)P nuclear magnetic resonance imaging and high-energy X-ray diffraction showed that it is the structural rearrangement of the phosphate network that is responsible for the variation in silver ion release and the associated bactericidal effectiveness. Thus, an understanding of the glass structure is important in interpreting the in vitro data and also has important clinical implications for the potential use of the phosphate-based glasses in orthopedic applications to deliver silver ions to combat S. aureus biofilm infections.