Microfluidic based electrochemical rapid detection system for the management of periodontal disease

Abstract

Oral diseases impair the quality of life. Therefore, identifying and recognising the bacteria that cause inflammatory diseases such as periodontitis at an early stage is crucial for the success of treatment. Point-of-care (POC) diagnostic systems are a promising approach enabling real-time detection and on-site data analysis in one device. However, these systems require a bacterial lysis procedure that fulfils POC requirements such as portability, sensitivity, fast response and minimal or no reliance on external equipment. Ionic liquids (IL) such as 1-ethyl-3-methylimidazolium acetate are an alternative to instrument-intensive thermal lysis (heating to 95 °C, 6 minutes). In this study, a total microbial load assay developed by Genspeed Biotech GmbH (Genspeed) using Escherichia coli (E. coli) as a model bacterium was investigated as part of the HydroChip2 project (FFG 883914). The main objective was to answer the following questions: Question 1, does the IL interfere with the chemiluminescence (CL) or the electrochemical (EC) assay? Question 2, is CL detection of E. coli on injection-moulded microfluidic chips (PerioPOC Pro Chips, Genspeed) comparable to low-cost and less resource-intensive roll-to-roll microfluidic chips (Fold-Chips)? Question 3, how comparable are the detection results obtained with the different approaches such as CL and EC? For question 1 on the influence of IL on the assay, it was found that depending on the volume concentration IL supports DNA-DNA and DNA-RNA hybridisation but prevents hybridisation at high concentrations (>40%(v/v)). This was observed using both the CL method and the EC method and, therefore, the IL concentration was set to 20%(v/v) IL for the assays. It was also investigated whether the IL had a negative effect on the EC measurements, but this could be ruled out for 20%(v/v) IL. When comparing the PerioPOC Pro-Chips with the Fold-Chips for question 2, it was found that although the Fold-Chips have a lower CL intensity, a bacterial measurement with a similar detection limit of ~104cfu/μl was possible, making the Fold-Chips comparable to the PerioPOC Pro-Chips. For question 3, the CL and EC measurement methods were compared in their performance for the detection of E. coli. The results show that the EC method is about one order of magnitude more sensitive than the CL method. However, further tests need to determine whether the advantage of the EC method for low-cost POC systems can be supported by sufficient sensitivity.