Detecting Respiratory Infection Causing Viruses Using Piezoelectric Plate Sensors in Thirty Minutes Without Gene Isolation and Amplification

Field: Chemical Engineering (Physical Sciences)

Respiratory viruses are the primary cause of human illnesses, exerting a substantial impact on global mortality, particularly among children younger than 5 years old and adults over 65 years. Influenza and RSV bear the highest disease burden among all the respiratory viruses worldwide. However, this changed since the Covid-19 pandemic which caused more than 772 million with more than 6.9 million deaths. Moreover, due to global vaccination and the several virus mutations the number of hospitalizations due to Covid-19-related infections has significantly reduced compared to its peak. Meanwhile, there has been an increase in hospitalizations related to seasonal epidemic-causing infections, such as Respiratory Syncytial Virus and Influenza. Furthermore, all three viruses have very similar symptoms, making it difficult for clinicians to treat patients given the reported cases of co-infections. Currently the gold standard for testing multiple viruses using a single sample is multiplexed PCR. However, these multiplexed tests are quite expensive ranging from $250-800 and take 1 - 2 days to get the results. Thus, there is an urgent need for a rapid, point of care (POC) and inexpensive multiplexed genetic test for simultaneous detecting Covid-19, Influenza, and RSV infection using a single swab sample. Piezoelectric Plate Sensors (PEPS) is a unique biosensor developed in Shih and Shih's lab has demonstrated isolation- and- amplification free genetic detection in-situ directly from patient samples with PCR sensitivity and specificity within 30 minutes. PEPS is made of a thin highly piezoelectric free-standing film made of Lead Magnesium Niobate-Lead Titanate (Pb(Mg1/3Nb2/3)O3)0.65-(PbTiO3)0.35 (PMN-PT). What is unique about PEPS is that its detection frequency shift (Δf) is inherently enhanced more than 1000 times by the unique property of the patented piezoelectric layer due to the binding stress-induced crystalline orientation switching. However, PEPS couldn't be reproduced because the PMN-PT synthesis process was not repeatable. Recently a new method was developed to synthesize PMN-PT repeatable, but the PEPS produce using this method were highly conductive and the detection (Δf) was not reliable in highly conductive lysing media at target detection temperature (60˚C). Therefore, the goal of this thesis is to fabricate PEPS that are stable at 60˚C with a low noise level in highly conductive lysing media to detect respiratory infection causing viruses using Covid-19 as a model for assay development and further explore multiplex testing using RSV and Influenza. In this study the conductivity of PEPS was decreased by synthesizing PMN-PT by reducing the amount of lead excess in the PT coating step which produced PEPS with loss factor less than 1.5% and had a noise level of 54Hz in lysing solution. Additionally, a repeatable protocol was developed to sinter PMN-PT tapes, producing flat tapes with no impurities. A Covid-19 genetic assay was developed by designing a DNA probe which was specific to all currently known Covid-19 virus variants. 20 positive and 10 negative Covid-19 patient samples were tested, achieving a detection sensitivity of 54 viruses/ml. Furthermore 20 blinded patient samples were tested, and PEPS achieved a sensitivity of 90% and specificity of 100%. To further develop multiplex testing capabilities, probe DNA was designed to specifically detect RSV, Influenza A, and Influenza B, all with similar melting temperature. PEPS exhibited high specificity toward target detection with no change in frequency shift in the presence of non-target viral particles.