(161e) Dielectrophoresis-Based Microfluidic Platform for Rapid and Label-Free Detection of Rickettsia Montanensis Infections

Tick-borne illnesses caused by Rickettsia species pose a significant public health threat, with over 50,000 cases reported to the CDC in 2019 alone. Among them, Rocky Mountain spotted fever (RMSF) is the most severe, often affecting multiple organ systems and carrying a mortality rate of 40–50% without timely treatment. Conventional diagnostic techniques such as serology and PCR often lack the speed, sensitivity, or specificity needed for early detection, emphasizing the urgent need for alternative diagnostic strategies that are rapid, reliable, and field-deployable.

This work presents a microfluidic diagnostic approach based on dielectrophoresis (DEP) for the detection of Rickettsia montanensis, a closely related model organism to the RMSF-causing Rickettsia rickettsii. DEP utilizes non-uniform electric fields to manipulate cells based on their dielectric properties, enabling selective enrichment and separation. Vero cells, the epithelial cells derived from the African green monkey kidney, were cultured and infected with R. montanensis. Dielectric characterization was performed using the 3DEP analyzer in a 500 µS/cm conductivity sugar-based medium.

A custom-designed two-inlet, two-outlet microfluidic device was designed using Fusion 360 and modeled in COMSOL Multiphysics to simulate DEP behavior under various electric field conditions. Infected and uninfected (control) cells were evaluated for their distinct electrophysiological profiles across a range of AC voltages and frequencies. To experimentally validate these models, the device is currently being fabricated using a high-resolution 3D microfluidic printer, with performance testing planned in upcoming experiments.

Preliminary results indicate clear differences in dielectric behavior between infected and healthy Vero cells. Optimal separation conditions were observed at 3 V_pp and 50 kHz, where infected cells exhibiting a significantly shifted crossover frequency, the frequency which the DEP force reverses direction, and DEP force approaches zero. Simulations further demonstrated 100% separation efficiency under defined flow conditions (250 µm/s in inlet 1 and 800 µm/s in inlet 2), supporting the theoretical viability of DEP-based detection. These findings demonstrate the feasibility to discriminate between infected and uninfected cells based on their biophysical signatures.

This study demonstrates the feasibility of a rapid, label-free diagnostic platform for Rickettsia infections using DEP-microfluidics. This technique provides real-time results without requiring labeling or specialized reagents, making it a promising tool for early detection, particularly in low-resource or point-of-care settings. Continued fabrication and testing of the 3D-printed device will further validate its utility for infectious disease diagnostics.