Self-powered Biosensor for Rapid Pathogen Detection

Introduction:: Rapid detection of bacterial and viral pathogens is necessary to provide real-time results to mitigate illness outbreaks, allow timely and proper treatment to patients, and facilitate epidemiology studies. Traditional culture enrichment methods are time-consuming and labor-intensive, and require trained personnel, limiting their use in resource-constrained settings. Although rapid testing methods such as lateral flow assays offer some benefits, they are limited in their sensitivity and can only provide qualitative detection results (presence/absence) without the aid of external instruments. The need for point-of-care biosensors that are affordable, user-friendly, sensitive, specific, rapid, and equipment-free while providing informative readouts has become increasingly urgent in the cases of outbreaks and pandemics.

Self-powered biosensors have emerged as a promising solution to overcome the limitations of these detection methods. Most reported self-powered biosensors employed enzymatic biofuel cells. Their applications are limited due to the susceptibility of enzymes to storage and reaction temperatures and inhibitors present in biological samples. To meet the urgent needs for point-of-care biosensors, we developed a nanomaterial-based self-powered electrochemical biosensor using lithium manganese oxide (LMO) nanoparticles as working electrode material which is deposited on a screen-printed carbon electrode chip (SPCE). Upon the presence of the target pathogen, based on the removal of pre-deposited non-conductive blocker nanoparticles from the working electrode (cathode) surface, the electrode can be activated to allow redox reaction to happen and generate a current that is proportional to the concentration of the target pathogens.

Materials and Methods:: The principle of the self-powered biosensor is shown in Figure 1. A slurry containing lithium manganese oxide (LMO) nanoparticles is prepared and deposited on the working electrode of an SPCE to serve as the cathode. Then the LMO-modified working electrode is pre-delithiated (oxidized). A layer of non-conductive blockers (silica nanoparticle-aptamer conjugates) is deposited on pre-delithiated cathode surface. When LiCl electrolyte is added to the electrode surface, the blockers block the access of lithium ions to the electrode surface and therefore block the charge transfer. Magnetic nanoparticles (MNPs) functionalized with specific aptamers capture the target pathogens and separated them from the sample matrix when a magnetic field is applied. Then the MNP-pathogen complexes are introduced to the electrode system, where they form MNP-pathogen-silica complexes due to the specific binding of the aptamers on silica particles to the pathogen. When a magnetic field is applied, these complexes are removed away from the electrode surface, thus increasing the access of lithium ions and further increasing the charge transfer and current. The time for each step is shown, with a detection time from samples to readouts of less than 30 min.

Results, Conclusions, and Discussions:: To demonstrate the self-powering and sensing capability of the LMO-modified SPCE chip, we introduced different concentrations of LiCl electrolyte (1M, 0.1M, and 0.01M) to the electrode surface, and electrochemical studies were conducted by cyclic voltammetry (CV). The generated current was proportional to the concentration of lithium ions. To investigate the efficacy of the blocking layer, we coated the LMO-modified working electrode with varying amounts (2 to 9 mg) of silica nanoparticles and recorded CV. We observed that the current increased as the amount of silica decreased. The results confirmed that the blocking was effective in preventing the access of lithium ions and the removal of the blockers allowed the redox reaction between LMO and lithium ions to happen. The current generated due to the redox reaction was dependent on the amount of blockers removed and lithium ions accessing the working electrode surface. These results demonstrated the potential of generating current (power) upon the presence of the target pathogen which results in the removal of blockers and access of lithium ions to the working electrode.

Based on the results obtained from the electrochemical studies, it is concluded that the LMO-modified SPCE chip demonstrated self-powering and sensing capacities. We are using this chip to demonstrate the self-powered biosensor with example pathogens, Salmonella, and optimizing the performance of the biosensor. This involves testing the biosensor with a sample containing the pathogen of interest to evaluate its sensitivity, selectivity, and reproducibility. Since this biosensing principle can be applied to detect various pathogens by changing the pathogen-specific aptamers, it can be potentially adapted in various in-field and point-of-care detection scenarios and extended to more applications to ensure public health and safety.

Acknowledgements (Optional): :

References (Optional): :