Development of an Ultrasensitive Capacitive DNA-sensor: A promising tool towards microbial diagnostics

Abstract: Popular Abstract in English A handful of diseases-causing pathogenic microorganisms claim millions of lives worldwide each year, mainly due to limited diagnostic capabilities. The lack of simple, cost-effective, sensitive and rapid on-site diagnostic tools lead to delays in the diagnoses with a subsequent lag in treatment, which in turn can result in serious complications or even loss of lives. Infectious diseases pose a serious threat to human well-being and to the economic development. For instance, the estimate economic burden of the diseases caused by antimicrobial resistant microorganisms within the European Union amounts to € 1.5 billion over all societal costs per year; in Thailand and USA the societal costs totals US$ 1.3 and 35 billion per year, respectively. Likewise, the economic cost for multi-drug resistance Tuberculosis-related deaths in Sub-Sahara Africa from year 2006 to 2015 is estimated to be US$ 519 billion. Most of the current diagnostic tools in our hospitals and clinical laboratories are capable of detecting ‘bad bugs’ (i.e. pathogenic microorganisms) when their concentration in a patient’s clinical sample is reasonably high. However, the pathogens do not reach detectable concentration until the disease has progressed and become significantly inferior. Some of the infectious diseases such as Ebola haemorrhagic fever, which has killed more than 8000 people in West Africa, need an immediate intervention to hinder the exponential spreading and to prevent the situation from becoming an even worse catastrophe than it is today. Currently, the tools for minimizing the spreading of the Ebola virus are few and merely include isolation of infected persons from the rest of the population and thereafter to simply wait out the disease. Hence, many people become infected while encountering patients during their asymptomatic stage of the disease. Although most of the current diagnostic tools are highly sophisticated, their complexity and expensive operations restrict them to off-site analysis, which additionally serve as an impediment to the efficient pathogen diagnosis in remote areas, especially in developing countries. The limited availability of on-site diagnostic capabilities has significantly increased the need for the development of rapid, cost-effective and portable devices for diagnosis of infectious diseases. In this work, a novel diagnostic device has been developed, which rapidly can detect small amount of bacteria based on the genetic material (DNA). DNA is the storage house or cellular library that contains all genetic information required in the functioning and growth of every living thing, from humans to single-cell organisms, as well as DNA-viruses. The developed device, a capacitive DNA-sensor consists of a disposable sensing chip, which is constructed using a simple and cheap manufacturing method. The capacitive DNA-sensor is automated, and it can be miniaturized and adapted for in-field use including bacterial diagnosis in remote areas under resource-limited settings. The stability and uniqueness of the DNA-material make the capacitive DNA-sensor highly effective and suitable for the targeting of specific bacteria based on their set of genes. The operational cost for the capacitive sensor is aimed to be very low as a sensing chip can be reused for at least 20 assays before replacement. Furthermore, the developed capacitive DNA-sensor is user-friendly and requires only limited amounts of training to operate.