A highly sensitive electrochemical biosensor based on AuNP-modified gold electrodes for selective determination of serum levels of crosslaps

Abstract

This article explains a step-wise protocol to develop an electrochemical sensor to quantify serum levels of C-telopeptide (CTX) crosslinks also known as crosslaps in a matter of minutes and with high level of accuracy. The technique needs only one-step (incubation) and can thus be used for point of care screening. Due to the excellent electrical properties of the as-prepared immunosensor, CTX levels were successfully measured from 1 to 1000 pg/mL. This is while the normal reference of the marker is 50-450 pg/mL, suggesting that the sensor can acceptably detect CTX. The results also showed a good correlation with ECLIA in measuring serum levels of CTX.

Keywords: Biosensor; Bone turnover marker; CTX; Crosslaps; Electrochemistry.

Fig. 1

A picture of the fabricated electrode

Fig. 2

a STEM results micrographs and b cyclic voltammogram (in 0.1 mM K₃[Fe(CN)₆], containing 0.01 M NaCl, at room temperature (23 °C) from 0.0 to 1.2 V with scan rate 0.1 V/s) of a bare gold, and b AuNP-modified c Ab-functionalized electrode (Khashayar 2017)

Fig. 3

DPV (in 0.1 mM K₃[Fe(CN)₆], containing 0.01 M NaCl, at room temperature (23 °C) with 0.025 V modulation amplitude, 0.05 s modulation time, 0.005 step potential, and voltage range from 0.5 to 1.1 V) of 1 pg/mL (lowest) and 100 pg/mL concentrations of CTX antigen

Fig. 4

Calibration curve of different CTX concentrations using the proposed immunosensor for signal tracing and amplification (Khashayar 2017)

Fig. 5

Surface preparation is typically made possible by modifying the gold surface by AuNP, leaving carboxyl groups on the surface which in turn can be activated using zero crosslength linkers such as (EDC/NHS), rapidly accepting an antibody, and detection can occur under target binding (Khashayar 2017)

Fig. 6

Response measured for CTX sensor incubated with Osteocalcin (100 pg/mL), PTH (100 pg/mL) and CTX (100 pg/mL)

Fig. 7

Statistical analysis comparing ECLIA vs. CTX sensor immunoassay a correlation plot b bland and Altman plot (Khashayar 2017)