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1.  Evaluation of bacteria-induced enamel demineralization using optical profilometry 
Objectives
Streptococcus mutans is considered a major causative of tooth decay due to it’s ability to rapidly metabolize carbohydrates such as sucrose. One prominent excreted end product of sucrose metabolism is lactic acid. Lactic acid causes a decrease in the pH of the oral environment with subsequent demineralization of the tooth enamel. Biologically relevant bacteria-induced enamel demineralization was studied.
Methods
Optical profiling was used to measure tooth enamel decay with vertical resolution under one nanometer and lateral features with optical resolution as a result of S. mutans biofilm exposure. Comparison measurements were made using AFM.
Results
After 72 hr of biofilm exposure the enamel displayed an 8-fold increase in the observed roughness average, (Ra), as calculated over the entire measured array. Similarly, the average root mean square (RMS) roughness, RRMS, of the enamel before and after biofilm exposure for 3 days displayed a 7-fold increase. Further, the direct effect of chemically induced enamel demineralization using biologically relevant organic acids was shown. Optical profiles of the enamel surface after addition of a 30% lactic acid solution showed a significant alteration in the surface topography with a corresponding increase in respective surface roughness statistics. Similar measurements with 10% citric acid over seconds and minutes give insight into the demineralization process by providing quantitative measures for erosion rates: comparing surface height and roughness as metrics.
Significance
The strengths of optical profilometry as an analytical tool for understanding and analyzing biologically relevant processes such as biofilm induced tooth enamel demineralization were demonstrated.
doi:10.1016/j.dental.2009.07.012
PMCID: PMC3454478  PMID: 19732947
enamel erosion; optical profilometry; biofilm; Streptococcus mutans; enamel demineralization; citric acid; lactic acid; AFM
2.  Green Tea Extract Selectively Targets Nanomechanics of Live Metastatic Cancer Cells 
Nanotechnology  2011;22(21):215101.
Green tea extract (GTE) is known to be a potential anticancer agent(1) with various biological activities(2, 3) yet the precise mechanism of action is still unclear. The biomechanical response of GTE treated cells taken directly from patient’s body samples was measured using atomic force microscopy(AFM)(4). We found significant increase in stiffness of GTE treated metastatic tumor cells, with a resulting value similar to untreated normal mesothelial cells, whereas mesothelial cell stiffness after GTE treatment is unchanged. Immunofluorescence analysis showed an increase in cytoskeletal-F-actin in GTE treated tumor cells, suggesting GTE treated tumor cells display mechanical, structural and morphological features similar to normal cells, which appears to be mediated by annexin-I expression, as determined by siRNA analysis of an in vitro cell line model. Our data indicates that GTE selectively targets human metastatic cancer cells but not normal mesothelial cells, a finding that is significantly advantageous compared to conventional chemotherapy agents.
doi:10.1088/0957-4484/22/21/215101
PMCID: PMC3151463  PMID: 21451222
3.  Nanocharacterization in Dentistry 
About 80% of US adults have some form of dental disease. There are a variety of new dental products available, ranging from implants to oral hygiene products that rely on nanoscale properties. Here, the application of AFM (Atomic Force Microscopy) and optical interferometry to a range of dentistry issues, including characterization of dental enamel, oral bacteria, biofilms and the role of surface proteins in biochemical and nanomechanical properties of bacterial adhesins, is reviewed. We also include studies of new products blocking dentine tubules to alleviate hypersensitivity; antimicrobial effects of mouthwash and characterizing nanoparticle coated dental implants. An outlook on future “nanodentistry” developments such as saliva exosomes based diagnostics, designing biocompatible, antimicrobial dental implants and personalized dental healthcare is presented.
doi:10.3390/ijms11062523
PMCID: PMC2904930  PMID: 20640166
nano-characterization; dentistry; biofilms; bacterial adhesins; implants; dentine tubule; afm; interferometry; nanodentistry

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