Improving the Stability and Sensing of Electrochemical Biosensors by Employing Trithiol-Anchoring Groups in a Six-Carbon Self-Assembled Monolayer

Abstract

Alkane thiol self-assembled monolayers (SAMs) have seen widespread utility in the fabrication of electrochemical biosensors. Their utility, however, reflects a potentially significant compromise. While shorter SAMs support efficient electron transfer, they pack poorly and are thus relatively unstable. Longer SAMs are more stable, but suffer from less efficient electron transfer, thus degrading sensor performance. Here we use the electrochemical DNA (E-DNA) sensor platform to compare the signaling and stability of biosensors fabricated using a short, six-carbon monothiol with those employing either of two commercially available, trihexylthiol anchors (a flexible Letsinger-type and a rigid adamantane type). We find that all three anchors support efficient electron transfer and E-DNA signaling, with the gain, specificity and selectivity of all three being effectively indistinguishable. The stabilities of the three anchors, however, vary significantly. Sensors anchored with the flexible trithiol exhibit enhanced stability, retaining 75% of their original signal and maintaining excellent signaling properties after 50 days storage in buffer. Likewise these sensors exhibit excellent temperature stability and robustness to electrochemical interrogation. The stability of sensors fabricated using the rigid trithiol anchor, by comparison, are similar to those of the monothiol. Both exhibit significant (>60%) loss of signal upon wet storage or thermocycling. Employing a flexible trithiol anchor in the fabrication of SAM-based electrochemical biosensors may provide a means of improving sensor robustness without sacrificing electron transfer efficiency or otherwise impeding sensor performance.

Comparing the Properties of Electrochemical-Based DNA Sensors Employing Different Redox Tags

“…2). This agrees well with previous reports of E-DNA sensors 19. The affinities of each type of sensor for the complementary target are likewise similar, with the dissociation constant of MB-based sensors (44 ± 18 nM) being slightly poorer than the Fc-based (25 ± 4 nM).…”

A sandwich-like strategy for the label-free detection of oligonucleotides by surface plasmon fluorescence spectroscopy (SPFS)

“…57,58 Also the mild dehybridization procedure by rinsing with pure water may help to conserve the sensor surface. 44,59 When in contrast to rinsing with pure water the sensor chips were rinsed with buffer solution after hybridization with the target, after a few minutes the fluorescence signal became constant. A corresponding experiment for the detection of the target T 40 is shown in Fig.…”

Surface chemistry effects on the performance of an electrochemical DNA sensor

“…E-DNA shelf life, an important parameter to consider vis a vis real-world sensor applications, can be strongly affected by the nature of the co-adsorbate [ 29,30 ]. To test this we studied the dry storage stability of our sensors by periodically taking them up in buffer and evaluating their initial (no target) peak currents (Fig.…”