IADR Abstract Archives
Colorimetric Detection of Mutans Streptococci Using Magnetic Nanoparticles
Objectives: Chair-side detection of mutans streptococci (MS: Streptococcus mutans and Streptococcus sobrinus) is an important aid to clinical dental caries risk assessment. Automutanolysin (Aml) is a peptidoglycan hydrolase whose cell wall binding domain (CWBD) has substrate specificity towards MS. This study aimed to develop a visual detection assay using magnetic nanoparticles (MNPs) conjugated with CWBD of Aml.
Methods: MNPs were grafted with poly(acrylic-acid) providing active carboxyl-groups for conjugation with CWBD of Aml. To determine the binding specificity to MS, the CWBD-conjugated-MNPs were mixed with pure cultures of standard strains of 4 different species of streptococci. Bacteria-bound MNPs were then separated from unbound-cells by magnets and re-suspended in phosphate buffer saline. The suspension was then filtered through a membrane (pore-size 0.8µm). The color intensity of MNPs remained on the membrane represents the quantity of bound-bacteria. Moreover, to determine the capture efficiency (CE) of the CWBD-conjugated MNPs, bacterial cultures were incubated with the CWBD-conjugated MNPs and the amounts of cells before and that remained after the incubation were determined by colony count (CFU). The CE was calculated using the formula: CFUbefore-CFUafter/CFUbefore x 100.
Results: The color intensity of CWBD-conjugated MNPs bound to MS was higher than those bound to the non-MS. This result implies that the CWBD-conjugated MNPs have greater binding specificity towards MS than non-MS. Moreover, the capture efficiency of the CWBD-conjugated MNPs for S. mutans and S. sobrinus were 77 and 69%, respectively, whereas that for S. sanguinis and S. salivarius (non-MS) was 38 and 15%, respectively. These values confirmed the specificity of the CWBD-conjugated MNPs towards S. mutans and S. sobrinus, but not to non-MS.
Conclusions: These results suggest that the colorimetric assay using MNPs conjugated with CWBD can specifically bind to MS and could be developed into a visual MS detection tool.
Methods: MNPs were grafted with poly(acrylic-acid) providing active carboxyl-groups for conjugation with CWBD of Aml. To determine the binding specificity to MS, the CWBD-conjugated-MNPs were mixed with pure cultures of standard strains of 4 different species of streptococci. Bacteria-bound MNPs were then separated from unbound-cells by magnets and re-suspended in phosphate buffer saline. The suspension was then filtered through a membrane (pore-size 0.8µm). The color intensity of MNPs remained on the membrane represents the quantity of bound-bacteria. Moreover, to determine the capture efficiency (CE) of the CWBD-conjugated MNPs, bacterial cultures were incubated with the CWBD-conjugated MNPs and the amounts of cells before and that remained after the incubation were determined by colony count (CFU). The CE was calculated using the formula: CFUbefore-CFUafter/CFUbefore x 100.
Results: The color intensity of CWBD-conjugated MNPs bound to MS was higher than those bound to the non-MS. This result implies that the CWBD-conjugated MNPs have greater binding specificity towards MS than non-MS. Moreover, the capture efficiency of the CWBD-conjugated MNPs for S. mutans and S. sobrinus were 77 and 69%, respectively, whereas that for S. sanguinis and S. salivarius (non-MS) was 38 and 15%, respectively. These values confirmed the specificity of the CWBD-conjugated MNPs towards S. mutans and S. sobrinus, but not to non-MS.
Conclusions: These results suggest that the colorimetric assay using MNPs conjugated with CWBD can specifically bind to MS and could be developed into a visual MS detection tool.