Disposable Low-Cost Sensor for at-Home Identification of Bacterial Vaginosis

Introduction:: Bacterial Vaginosis is the most frequently occurring vaginal infection amongst childbearing-aged women worldwide, yet it is significantly underdiagnosed as a majority of patients are asymptomatic. Untreated bacterial vaginosis increases one's risk of STI acquisition, pregnancy complications, and infertility; making it a serious concern for public health officials. Unlike typical infections with a single causative agent, bacterial vaginosis is the result of an imbalance in the ratio of naturally occurring aerobic and anaerobic bacteria within the vagina. As anaerobic organisms flourish, levels of trimethylamine, a metabolic byproduct, likewise increase. Clinical diagnosis of bacterial vaginosis is most commonly made according to Amsel Criteria. In this method a fish-like odor, caused by the increased levels of trimethylamine in vaginal fluid, is used as a key diagnostic.

Materials and Methods:: Here we investigate the development of a low-cost potentiometric sensor capable of detecting trimethylamine in simulated vaginal fluid. In lieu of traditional odor-based detection of volatilized trimethylamine, we instead identify the compound in its trimethylammonium (TMA) form by coupling the sensor with a potentiometric readout. We created the ion selective electrode using a carbon black coated cotton fiber and a TMA selective membrane composed of calix[4]arene and sodium tetrakis [3,5-bis(trifluoromethyl)phenyl] borate. Potentiometric measurements were performed in simulated vaginal fluid and TMA calibration curves were generated via stepwise dilution of TMA solutions. IUPAC recommendations were used to determine the limit of detection (LOD).

Results, Conclusions, and Discussions:: When paired with a standard reference electrode, the proposed electrodes (n=5), illustrated a slope of 55.14 ± 4.44 mV/d, comparable with the theoretical Nernstian value of 59.20 mV/d. Moreover, the limit of detection of the electrode is 8.66 μM which is two orders of magnitude lower than the clinically relevant concentration of trimethylamine in vaginal fluid.

Use of this sensor would provide clinicians with a quantitative value of trimethylamine, aiding in diagnosis of asymptomatic or early stage bacterial vaginosis. Our hope is that the low-cost nature of the sensor will increase the likelihood of regular testing, thus bolstering detection of both symptomatic and asymptomatic instances of infection.


Acknowledgements (Optional): : Authors thank the University of Southern California, Viterbi Graduate Fellowship, and the Core Center of Excellence in Nano Imaging at the University of Southern California


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