Utilizing layer-parameter of shear horizontal surface acoustic wave biosensor for lipoprotein particle sizing

Shear horizontal surface acoustic wave (SH-SAW) sensors are widely used in biosensing for marker detection and can also measure particle size. This study leverages SH-SAW technology with a reflective-type design and unique packaging technology to distinguish lipoprotein sizes on a 3 × 5 mm sensor chip, addressing the limitations of traditional, time-consuming methods like chromatography and nuclear magnetic resonance (NMR). A 250 MHz SH-SAW biosensor on 36° rotated Y-cut 90° X-propagating quartz substrates was used, with ApoA1, ApoB48, ApoB100, and Lp(a) antibodies immobilized on a gold surface to capture lipoproteins from human plasma. The ratio of velocity to attenuation changes, defined as the layer-parameter, was analyzed, and numerical calculations validated the experimental results. ApoA1-, ApoB48- and ApoB100-containing lipoproteins, as well as Lp(a), exhibited different sizes, with corresponding layer-parameter values of -0.398 ± 0.009, -1.133 ± 0.043, -0.661 ± 0.024, and -0.497 ± 0.035, respectively. These values demonstrated a strong correlation (<i>R</i> = 0.9987) between lipoprotein size and the increase in layer thickness. This study highlights that analyzing layer-parameters enables the estimation of lipoprotein size, thereby expanding the clinical potential of SH-SAW biosensors for point-of-care testing (POCT).