Detection and Real-Time Monitoring of LDL-Cholesterol by Redox-Free Impedimetric Biosensors

Abstract

In this work, non-faradaic impedimetric biosensor was developed for the direct detection of low-density lipoprotein (LDL-cholesterol). Unlike other electrochemical techniques, non-faradaic electrochemical impedance spectroscopy (EIS) does not require the use of redox probes which denatures targeted biomarkers. Furthermore, no reference electrode is required for detection which is commercially viable. The biosensor reported here consists of LDL-antibodies attached to interdigitated gold electrodes via standard chemical functionalization. The biosensor demonstrated a sensitivity and limit of detection (LoD) of 70 nF/log(ng/mL) and 120 pg/mL, respectively, where the LoD is well below the recommended LDL level in blood. The biosensor also demonstrated good selectivity toward LDL. Thereafter we utilized, for the first time, the non-faradaic impedimetric biosensor for the continuous monitoring of LDL in phosphate buffer saline (PBS). The biosensor showed rapid responses to LDL injections. Such an approach is essential for the development of low-cost and scalable wearable biosensors for the direct real-time monitoring of chronic diseases and hence allows early medical interventions in cases where sudden increases in LDL or other biomarkers are deadly.