In this paper, we interrogate the influence of silver nanoparticle (AgNPs)-based model surfaces o... more In this paper, we interrogate the influence of silver nanoparticle (AgNPs)-based model surfaces on mouse kidney-derived stem cells (mKSCs) differentiation. The widespread use of silver in biomedical and consumer products requires understanding of this element's effect on kidney cells. Moreover, the potential for using stem cells in drug discovery require methods to direct their differentiation to specialized cells. Hence, we generated coated model substrates containing different concentrations of surface immobilized AgNPs, and used them to evaluate properties and functions of mKSCs. Initially, mKSCs exhibited reduced viability on higher silver containing surfaces. However, longer culture periods assisted mKSCs to recover. Greater degree of cell spreading and arborization led by AgNPs, suggest podocyte differentiation. Proximal tubule cell marker's expression revealed differentiation to the specific lineage. Although the exact mechanism underpinning these findings require sig...
Background: The aim of the systematic review was to evaluate the effect of periodontal interventi... more Background: The aim of the systematic review was to evaluate the effect of periodontal interventions on the diversity and composition of periodontal microbiota assessed by high throughput sequencing (HTS) metagenomics analysis. Methods: An electronic search of all relevant databases was conducted from database inception to May 2021 by two independent reviewers. All clinical trials that evaluated the effect of periodontal interventions on the gingival microbiota through HTS were selected. The measures of alpha diversity was used as primary outcome; richness, Shannon diversity index, and the Chao1 index, whereas relative abundances of bacterial genera was considered as secondary outcome. The Robvis tool was used to assess the risk of bias. Results: Overall, 19 studies were eligible for the systematic review, of which 10 studies were included in the meta-analysis. Periodontal intervention for test group resulted in decrease in Shannon’s diversity, richness and Chao I index as observed ...
Journal of the International Academy of Periodontology, 2020
OBJECTIVES This study investigated changes induced by Porphyromonas gingivalis and on gastrointes... more OBJECTIVES This study investigated changes induced by Porphyromonas gingivalis and on gastrointestinal histology and gut microbiome in a mouse model of experimental periodontitis. The effect of probiotic Lactobacillus rhamnosus GG (LGG) in altering these changes was also investigated. METHODS IThirty-six mice were allocated into six groups. Experimental alveolar bone loss was induced by oral inoculation with P. gingivalis and F. nucleatum. LGG was orally inoculated or orally gavaged. Gastrointestinal tissue changes were assessed using histological analysis and immunohistochemistry. Caecal microbiome was analysed by sequencing 16S rRNA genes of caecal content. RESULTS Inoculation with P. gingivalis and F. nucleatum induced inflammation throughout gastrointestinal tract (p less than 0.05), increased expression of IL-6 in ileum (p = 0.052) and altered composition of caecal microbiome (p less than 0.05) in experimental mice compared to controls. Mice treated with LGG had reduced tissue ...
The metal ion release characteristics and biocompatibility of meta-based materials are key factor... more The metal ion release characteristics and biocompatibility of meta-based materials are key factors that influence their use in orthodontics. Although stainless steel-based alloys have gained much interest and use due to their mechanical properties and cost, they are prone to localised attack after prolonged exposure to the hostile oral environment. Metal ions may induce cellular toxicity at high dosages. To circumvent these issues, orthodontic brackets were coated with a functional nano-thin layer of plasma polymer and further immobilised with enantiomers of tryptophan. Analysis of the physicochemical properties confirmed the presence of functional coatings on the surface of the brackets. The quantification of metal ion release using mass spectrometry proved that plasma functionalisation could minimise metal ion release from orthodontic brackets. Furthermore, the biocompatibility of the brackets has been improved after functionalisation. These findings demonstrate that plasma polyme...
Objective: To assess the effect of osmotic stress on various bacteria in a planktonic milieu and ... more Objective: To assess the effect of osmotic stress on various bacteria in a planktonic milieu and the effect of exposure to sodium hypochlorite (NaOCl) on the microbial cells previously subjected to osmotic stress. Methods: Enterococcus faecalis, Streptococcus sanguinis, Fusobacterium nucleatum, Porphyromonas gingivalis and Prevotella intermedia were suspended as follows: Iso-osmotic group 0.9% NaCl; Hypo-osmotic group “ultrapure water”; Hyper-osmotic group 9% NaCl solution for 120 hours before exposure to 0.0001% NaOCl for 10 minutes. Quantitative analyses of viable cells were performed at 0 and 120 hours and after exposure to NaOCl to obtain colony forming units (CFU/mL). A linear mixed-effects model was used to find the association between mean CFU/mL (logarithmic transformation) and the interaction of solution Group and Time (P<0.001). Results: F. nucleatum, P. gingivalis and P. intermedia did not survive after 24 hours in any of the solutions and were excluded from further testing. For S. sanguinis there were significant differences at each time interval, when holding solution group constant. After 120 hours, the Hyper-osmotic group presented with the highest CFU/mL and was significantly different to the Iso-osmotic group (P<0.001). For E. Faecalis, there was a significant difference for each pairwise comparison of time (P<0.001) in mean CFU/mL between 0 hours and 120 hours for the Iso-osmotic and Hyper-osmotic groups. At 120 hours, no significant differences were found between the three groups. Significant differences were also found between 0 hours and Post-NaOCl administration, and between 120 hours and Post-NaOCl administration for all three groups (P<0.001). Exposure to NaOCl after hypo-osmotic stress was associated with significantly less CFU/mL for S. sanguinis compared to hyperosmosis and iso-osmosis (P<0.001) and for E. Faecalis only compared to hyperosmosis (P<0.001). Conclusion: S. sanguinis and E. faecalis were able to withstand osmotic stress for 120 hours. Hypo-osmotic stress before contact with NaOCl was associated with lower viable bacterial numbers, when compared to the other media for the above species. Hyper-osmotic stress was associated with higher viable bacterial numbers after NaOCl exposure for E. faecalis.
BACKGROUND Tooth discolouration could occur due to bacterial contamination in traumatized teeth. ... more BACKGROUND Tooth discolouration could occur due to bacterial contamination in traumatized teeth. Hydrogen peroxide is the commonly used bleaching agent. However, due to concerns over safety, alternative bleaching regimes such as sodium perborate (S) and thiourea-hydrogen peroxide (T) have been investigated. METHODS Apices resected and pulp extirpated 99 premolars were divided into two groups. Group 1 and 2 was injected with blood and blood/bacteria, stored anaerobically for 35 days. The two groups were treated by bleaching with water, S or T. Teeth were rebleached after 7 days. Colourimetric evaluation was assessed using digital imaging, CasMatch standardization and CIE L*a*b colour system preoperatively, 35 days of staining and 7 and 14 of bleaching. A linear mixed model with fixed effects of time, group and bleach was used to examine colour difference. RESULTS Blood-stained teeth were significantly redder and darker on day 35 compared with blood/bacteria-stained teeth. After bleaching, blood-stained teeth retained significant redness compared with blood/bacteria-stained teeth using either S or T. T produced a significantly whiter shade in both the groups after 14 days. CONCLUSIONS Blood-stained teeth were significantly darker and red compared with blood/bacteria-stained teeth. T bleaching regime was more effective than S.
The coexistence of bacteria in natural environments can often be explained in terms of competitio... more The coexistence of bacteria in natural environments can often be explained in terms of competition for a growth-limiting substrate(s), and the outcome of such competition depends upon relevant growth parameters such as substrate affinity and yield. Dental plaque bacteria are frequently carbon and energy limited. Growth parameters for seven oral Streptococcus species and one Actinomyces viscosus strain were estimated under glucose-limited conditions in continuous culture. In all strains, mixed-acid fermentation occurred at low growth rates, while amounts of lactate increased at higher growth rates. Two important growth parameters, mumax and Y glucose, were very similar in the two serotype c Streptococcus mutans strains (T8 and Ingbritt), one of the serotype d/g Streptococcus mutans strains (OMZ65), and the two Streptococcus milleri strains (699B3 and B448). Two other serotype d/g S. mutans strains (KIR and B13) were divergent from this group and had lower mumax values and a lower Y g...
The porcine enamel matrix derivative, EMD(®), which is the active component of Emdogain(®), is us... more The porcine enamel matrix derivative, EMD(®), which is the active component of Emdogain(®), is used widely in periodontics because of its ability to promote the regeneration of soft and hard tissues and to reduce inflammation. Previous studies have used indirect methods to explain its angiogenic and proliferative effects on cells associated with wound healing. In this study we used proteomic techniques to identify proteins in EMD other than amelogenins.
For dental plaque organisms such as Streptococcus sanguis, the ecological importance of the abili... more For dental plaque organisms such as Streptococcus sanguis, the ecological importance of the ability to utilize arginine as an energy source has been established in previous studies. The present investigation was undertaken to determine the ability of a strain of S. sanguis to process unsubstituted arginine-containing peptides. The organism was grown under glucose-limited conditions in a chemically defined medium, and peptide was added to washed, resting cells in a pH-stat at pH 7.0. Filtrates taken at appropriate time intervals were assayed for peptide, free amino acids, and metabolites. Irrespective of the position of the arginine residue, all peptides tested were attacked, although those that possessed a C-terminal arginine (including a tetrapeptide) were processed at a faster rate than were those in which arginine was N terminal. However, C-terminal arginine was cleaved only slowly from a peptide containing 24 residues. In each case, most of the released arginine was converted to...
3D printing provides numerous opportunities for designing tissue engineering constructs with intr... more 3D printing provides numerous opportunities for designing tissue engineering constructs with intricate porosity, geometry and favourable mechanical properties and has the potential to revolutionize medical treatments.
2-Methyl-2-oxazoline plasma polymerized silver nanoparticles containing coatings are not toxic to... more 2-Methyl-2-oxazoline plasma polymerized silver nanoparticles containing coatings are not toxic towards mouse kidney derived stem cells (mKSCs) and regulate mKSCs differentiation.
In this paper, we interrogate the influence of silver nanoparticle (AgNPs)-based model surfaces o... more In this paper, we interrogate the influence of silver nanoparticle (AgNPs)-based model surfaces on mouse kidney-derived stem cells (mKSCs) differentiation. The widespread use of silver in biomedical and consumer products requires understanding of this element's effect on kidney cells. Moreover, the potential for using stem cells in drug discovery require methods to direct their differentiation to specialized cells. Hence, we generated coated model substrates containing different concentrations of surface immobilized AgNPs, and used them to evaluate properties and functions of mKSCs. Initially, mKSCs exhibited reduced viability on higher silver containing surfaces. However, longer culture periods assisted mKSCs to recover. Greater degree of cell spreading and arborization led by AgNPs, suggest podocyte differentiation. Proximal tubule cell marker's expression revealed differentiation to the specific lineage. Although the exact mechanism underpinning these findings require sig...
Background: The aim of the systematic review was to evaluate the effect of periodontal interventi... more Background: The aim of the systematic review was to evaluate the effect of periodontal interventions on the diversity and composition of periodontal microbiota assessed by high throughput sequencing (HTS) metagenomics analysis. Methods: An electronic search of all relevant databases was conducted from database inception to May 2021 by two independent reviewers. All clinical trials that evaluated the effect of periodontal interventions on the gingival microbiota through HTS were selected. The measures of alpha diversity was used as primary outcome; richness, Shannon diversity index, and the Chao1 index, whereas relative abundances of bacterial genera was considered as secondary outcome. The Robvis tool was used to assess the risk of bias. Results: Overall, 19 studies were eligible for the systematic review, of which 10 studies were included in the meta-analysis. Periodontal intervention for test group resulted in decrease in Shannon’s diversity, richness and Chao I index as observed ...
Journal of the International Academy of Periodontology, 2020
OBJECTIVES This study investigated changes induced by Porphyromonas gingivalis and on gastrointes... more OBJECTIVES This study investigated changes induced by Porphyromonas gingivalis and on gastrointestinal histology and gut microbiome in a mouse model of experimental periodontitis. The effect of probiotic Lactobacillus rhamnosus GG (LGG) in altering these changes was also investigated. METHODS IThirty-six mice were allocated into six groups. Experimental alveolar bone loss was induced by oral inoculation with P. gingivalis and F. nucleatum. LGG was orally inoculated or orally gavaged. Gastrointestinal tissue changes were assessed using histological analysis and immunohistochemistry. Caecal microbiome was analysed by sequencing 16S rRNA genes of caecal content. RESULTS Inoculation with P. gingivalis and F. nucleatum induced inflammation throughout gastrointestinal tract (p less than 0.05), increased expression of IL-6 in ileum (p = 0.052) and altered composition of caecal microbiome (p less than 0.05) in experimental mice compared to controls. Mice treated with LGG had reduced tissue ...
The metal ion release characteristics and biocompatibility of meta-based materials are key factor... more The metal ion release characteristics and biocompatibility of meta-based materials are key factors that influence their use in orthodontics. Although stainless steel-based alloys have gained much interest and use due to their mechanical properties and cost, they are prone to localised attack after prolonged exposure to the hostile oral environment. Metal ions may induce cellular toxicity at high dosages. To circumvent these issues, orthodontic brackets were coated with a functional nano-thin layer of plasma polymer and further immobilised with enantiomers of tryptophan. Analysis of the physicochemical properties confirmed the presence of functional coatings on the surface of the brackets. The quantification of metal ion release using mass spectrometry proved that plasma functionalisation could minimise metal ion release from orthodontic brackets. Furthermore, the biocompatibility of the brackets has been improved after functionalisation. These findings demonstrate that plasma polyme...
Objective: To assess the effect of osmotic stress on various bacteria in a planktonic milieu and ... more Objective: To assess the effect of osmotic stress on various bacteria in a planktonic milieu and the effect of exposure to sodium hypochlorite (NaOCl) on the microbial cells previously subjected to osmotic stress. Methods: Enterococcus faecalis, Streptococcus sanguinis, Fusobacterium nucleatum, Porphyromonas gingivalis and Prevotella intermedia were suspended as follows: Iso-osmotic group 0.9% NaCl; Hypo-osmotic group “ultrapure water”; Hyper-osmotic group 9% NaCl solution for 120 hours before exposure to 0.0001% NaOCl for 10 minutes. Quantitative analyses of viable cells were performed at 0 and 120 hours and after exposure to NaOCl to obtain colony forming units (CFU/mL). A linear mixed-effects model was used to find the association between mean CFU/mL (logarithmic transformation) and the interaction of solution Group and Time (P<0.001). Results: F. nucleatum, P. gingivalis and P. intermedia did not survive after 24 hours in any of the solutions and were excluded from further testing. For S. sanguinis there were significant differences at each time interval, when holding solution group constant. After 120 hours, the Hyper-osmotic group presented with the highest CFU/mL and was significantly different to the Iso-osmotic group (P<0.001). For E. Faecalis, there was a significant difference for each pairwise comparison of time (P<0.001) in mean CFU/mL between 0 hours and 120 hours for the Iso-osmotic and Hyper-osmotic groups. At 120 hours, no significant differences were found between the three groups. Significant differences were also found between 0 hours and Post-NaOCl administration, and between 120 hours and Post-NaOCl administration for all three groups (P<0.001). Exposure to NaOCl after hypo-osmotic stress was associated with significantly less CFU/mL for S. sanguinis compared to hyperosmosis and iso-osmosis (P<0.001) and for E. Faecalis only compared to hyperosmosis (P<0.001). Conclusion: S. sanguinis and E. faecalis were able to withstand osmotic stress for 120 hours. Hypo-osmotic stress before contact with NaOCl was associated with lower viable bacterial numbers, when compared to the other media for the above species. Hyper-osmotic stress was associated with higher viable bacterial numbers after NaOCl exposure for E. faecalis.
BACKGROUND Tooth discolouration could occur due to bacterial contamination in traumatized teeth. ... more BACKGROUND Tooth discolouration could occur due to bacterial contamination in traumatized teeth. Hydrogen peroxide is the commonly used bleaching agent. However, due to concerns over safety, alternative bleaching regimes such as sodium perborate (S) and thiourea-hydrogen peroxide (T) have been investigated. METHODS Apices resected and pulp extirpated 99 premolars were divided into two groups. Group 1 and 2 was injected with blood and blood/bacteria, stored anaerobically for 35 days. The two groups were treated by bleaching with water, S or T. Teeth were rebleached after 7 days. Colourimetric evaluation was assessed using digital imaging, CasMatch standardization and CIE L*a*b colour system preoperatively, 35 days of staining and 7 and 14 of bleaching. A linear mixed model with fixed effects of time, group and bleach was used to examine colour difference. RESULTS Blood-stained teeth were significantly redder and darker on day 35 compared with blood/bacteria-stained teeth. After bleaching, blood-stained teeth retained significant redness compared with blood/bacteria-stained teeth using either S or T. T produced a significantly whiter shade in both the groups after 14 days. CONCLUSIONS Blood-stained teeth were significantly darker and red compared with blood/bacteria-stained teeth. T bleaching regime was more effective than S.
The coexistence of bacteria in natural environments can often be explained in terms of competitio... more The coexistence of bacteria in natural environments can often be explained in terms of competition for a growth-limiting substrate(s), and the outcome of such competition depends upon relevant growth parameters such as substrate affinity and yield. Dental plaque bacteria are frequently carbon and energy limited. Growth parameters for seven oral Streptococcus species and one Actinomyces viscosus strain were estimated under glucose-limited conditions in continuous culture. In all strains, mixed-acid fermentation occurred at low growth rates, while amounts of lactate increased at higher growth rates. Two important growth parameters, mumax and Y glucose, were very similar in the two serotype c Streptococcus mutans strains (T8 and Ingbritt), one of the serotype d/g Streptococcus mutans strains (OMZ65), and the two Streptococcus milleri strains (699B3 and B448). Two other serotype d/g S. mutans strains (KIR and B13) were divergent from this group and had lower mumax values and a lower Y g...
The porcine enamel matrix derivative, EMD(®), which is the active component of Emdogain(®), is us... more The porcine enamel matrix derivative, EMD(®), which is the active component of Emdogain(®), is used widely in periodontics because of its ability to promote the regeneration of soft and hard tissues and to reduce inflammation. Previous studies have used indirect methods to explain its angiogenic and proliferative effects on cells associated with wound healing. In this study we used proteomic techniques to identify proteins in EMD other than amelogenins.
For dental plaque organisms such as Streptococcus sanguis, the ecological importance of the abili... more For dental plaque organisms such as Streptococcus sanguis, the ecological importance of the ability to utilize arginine as an energy source has been established in previous studies. The present investigation was undertaken to determine the ability of a strain of S. sanguis to process unsubstituted arginine-containing peptides. The organism was grown under glucose-limited conditions in a chemically defined medium, and peptide was added to washed, resting cells in a pH-stat at pH 7.0. Filtrates taken at appropriate time intervals were assayed for peptide, free amino acids, and metabolites. Irrespective of the position of the arginine residue, all peptides tested were attacked, although those that possessed a C-terminal arginine (including a tetrapeptide) were processed at a faster rate than were those in which arginine was N terminal. However, C-terminal arginine was cleaved only slowly from a peptide containing 24 residues. In each case, most of the released arginine was converted to...
3D printing provides numerous opportunities for designing tissue engineering constructs with intr... more 3D printing provides numerous opportunities for designing tissue engineering constructs with intricate porosity, geometry and favourable mechanical properties and has the potential to revolutionize medical treatments.
2-Methyl-2-oxazoline plasma polymerized silver nanoparticles containing coatings are not toxic to... more 2-Methyl-2-oxazoline plasma polymerized silver nanoparticles containing coatings are not toxic towards mouse kidney derived stem cells (mKSCs) and regulate mKSCs differentiation.
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Papers by Peter Zilm