Picosensor-Optical Microarray Technology for Clinical Diagnosis of Type of Diabetes
The presence of ultra-low levels of insulin (picomolar) in blood demands the need for highly sensitive, reliable, and user-friendly novel analytical sensors to diagnose the type of diabetes, and thus aid doctors in deciding a treatment plan promptly. While absorbance, chemiluminescence, and radio-label based immunoassays for serum insulin detection are currently available, these methods require chemical labels and their tedious conjugation to antibodies along with the specific needs for substrate, reagents, and instruments, to only yield the indirect insulin measurements. Thus, increasing the simplicity of insulin detection by a label-free immunoassay with high sensitivity is very advantageous.
Our group has designed an insulin-sensor based on magnetic nanoparticles conjugation of insulin in serum and blood, and detected the insulin levels using a surface immobilized antibody. We initially constructed the sensor on gold coated quartz crystals to optimize the experimental and assay conditions, and detected the insulin levels based on oscillation frequency and impedance signal changes. We then extended the detection mode to insulin-oxidation signals measured by a square wave voltammetry, which needed a high surface area carbon nanostructured electrodes. Following this, we transferred the sensor approach into a gold-array system to detect insulin levels by an optical-microarray imager. Our approach is highly sensitive that enabled the detection of clinically relevant pM levels. The analytical figure-of-merit of the described insulin-sensor and microarray system offering multi-independent detection modes will be discussed. We propose that the presented methods are generic to detecting other clinically important biomarkers with the required detection sensitivity.
Acknowledgements. Financial support by Oklahoma State University is greatly acknowledged.