Lysozyme aptamer biosensor based on electron transfer from SWCNTs to SPQC-IDE

Lysozyme (Lys) is one of the most versatile and ubiquitous proteins with vital functional roles in innate immune systems, therefore its detection is of considerable importance. In this work, a sensitive and selective piezoelectric aptamer biosensor for Lys detection was constructed using an aptamer-wrapped-SWCNTs-modified interdigital electrode (IDE) which was connected to the oscillator circuit in series with piezoelectric quartz crystal (SPQC). The anti-Lys aptamer labeled with thiolate terminal was immobilized on gold surfaces of the SPQC-IDE by AuS bonding. SWCNTs were bonded to the surface of SPQC-IDE through π-π stacking between the nucleotide bases of anti-Lys aptamer and the SWCNTs sidewall. Modified SWCNTs can be substituted by Lys resulting in sensitive frequency change of SPQC-IDE. The detection limit is lower than 0.5 nM for Lys, while when the biosensor was used to detect Lys concentrations in prepared human saliva sample, the recoveries were in the range of 93.1-105.4%. The novel biosensor for Lys detection proposed here is characterized by its high selectivity and sensitivity and shows great potential for use in clinical applications.