A Rapid Method for Estimation of Cariogenic Bacteria Based on a Stationary Liquid Phase Lab-on-a-chip

Salivary levels of Streptococcus mutans and Lactobacillus sp. are important risk factors for dental caries. Application of current test methods is limited because of the requirement for a time-consuming incubation step or expensive laboratory instruments. In this study, we developed a rapid method for determination of the representative cariogenic bacteria, S. mutans and Lactobacillus plantarum, based on a stationary liquid phase lab-on-a-chip (SLP LOC). The method utilized two types of particles, i.e., magnetic capture particles (CPs) for capture of target bacteria and nonmagnetic labeling particles (LPs) for labeling of the captured bacteria with horseradish peroxidase (HRP). Complexes of CP-bacteria-LP were formed in a sample chamber of the LOC and transported to a detection chamber containing the chromogenic substrate of HRP by moving a magnet under the LOC. The method is simple and enabled detection of the two bacteria in a range required for caries risk diagnosis within 40 min without the use of any complicated instruments. Accordingly, this method may have applications in the rapid diagnosis of dental caries risk.