Summary
A Stanford team reports that electrostatic charge screening, rather than target-triggered DNA shape changes, dominates the signal in a benchmark aminoglycoside electrochemical sensor. The findings are from a bioRxiv preprint and concern this sensor system.
A Stanford team reports that electrostatic charge screening, rather than target-triggered changes in DNA shape, dominates the signal in a benchmark electrochemical sensor for aminoglycoside antibiotics. The findings come from a bioRxiv preprint describing laboratory measurements of the sensor’s electrical and optical behaviour.
The result challenges the usual explanation for how this particular sensor signals target binding. It also highlights why understanding a sensor’s mechanism matters: an electrical response can arise from interactions with the nucleic-acid backbone, not only from a recognition strand folding around its intended target.
The sensor’s proposed signal mechanism
Electrochemical aptamer-based sensors are designed to monitor molecules through a nucleic-acid recognition element and an electrode-associated redox reporter. In the commonly proposed structure-switching model, a target binds the nucleic acid and changes its shape. That movement alters the reporter’s distance from the electrode, changing electron transfer and producing a measurable signal.
The Stanford researchers examined a prominent aminoglycoside sensor that has often been explained using this model. Aminoglycosides carry positive electrical charges, while DNA’s phosphate backbone is negatively charged. The researchers’ alternative explanation is that the drug’s charge screens the backbone’s electrostatic charge, changing the sensor’s electrical response without requiring a target-specific shape change.
Tests point to a charge-driven response
The team compared the legacy sensor sequence with unrelated DNA controls, including generic stem-loop hairpins, unstructured poly-thymine sequences and short DNA duplexes. The preprint reports that these controls showed apparent affinities and relative changes in electron-transfer kinetics similar to those of the original sensor sequence.
Bio-layer interferometry, circular dichroism and fluorescence spectroscopy were used to examine binding and molecular structure. The researchers report that aminoglycoside association occurred across the different DNA sequences, without detectable conformational reconfiguration. Further evidence came from assays that varied polyamine charge and from fluorescence imaging at the electrode surface. Together, these measurements led the authors to conclude that large-scale electrostatic screening of the nucleic-acid backbone, rather than structure switching, is the dominant source of the signal in this sensor system.
That distinction could affect how researchers interpret sensor selectivity and design future devices: a response attributed to a particular DNA sequence may instead reflect broader electrostatic interactions. The finding is specific to the aminoglycoside benchmark examined; it does not establish that other electrochemical aptamer sensors use the same mechanism. The report is a preprint, so its findings have not yet been peer-reviewed.