Analysis of Red Blood Cell Samples using a Handheld Shear-horizontal Surface Acoustic Wave Biosensor

Abstract

Human red blood cells (RBCs) are highly studied by researchers and clinicians alike because RBCs play an essential role in medical diagnostics. RBCs are the most abundant component of whole blood. The accurate analysis of blood samples for blood cells is crucial to help diagnose and management of several life-threatening diseases. Current techniques for analyzing blood cell counts are time-consuming and expensive, requiring a highly trained technician. Implementing a portable, label-free method enables analysis at small clinics and remote locations with reduced times of analysis and cost. The development of miniature, handheld shear-horizontal surface acoustic wave (SH-SAW) biosensors capable of accurately counting RBCs in liquid samples will improve medical diagnostics in resource-limited regions of the United States and parts of the world where access to centralized clinical laboratories is limited. A shear-horizontal surface acoustic wave is a horizontally polarized surface acoustic wave that is produced by a transducer that is fabricated onto a piezoelectric substrate such as lithium tantalate, lithium niobite, or quartz. We report a lithium tantalate SH-SAW biosensor and method for monitoring the RBC level (hematocrit level) from a whole blood sample using a shear-horizontal surface acoustic wave (SH-SAW) biosensor that uses a 500-picoliter sample well. Samples were introduced by directly pipetting whole blood onto the sample reservoir and washing away any excess material. The SH-SAW biosensor uses an immunoassay, where the antibody anti-glycophorin A is coated on the surface of the active area of the sensor. The sample is compared to a reference sample. Using Microsoft Excel statistical tools, we showed that the results demonstrate the concentration dependence of the samples with an average coefficient of variance (CV) within a sample group was 10% or less for all samples analyzed. Our successful demonstration offers proof of concept for handheld blood cell monitors for remote and resource-limited applications. To our knowledge, this is the first demonstration of an SH-SAW device being used for monitoring red blood cell counts.