Abstract
Zinc oxide field effect transistors (ZnO-FET), covalently functionalized with single stranded DNA aptamers, provide a highly selective platform for label-free small molecule sensing. The nanostructured surface morphology of ZnO provides high sensitivity and room temperature deposition allows for a wide array of substrate types. Herein we demonstrate the selective detection of riboflavin down to the pM level in aqueous solution using the negative electrical current response of the ZnO-FET by covalently attaching a riboflavin binding aptamer to the surface. The response of the biofunctionalized ZnO-FET was tuned by attaching a redox tag (ferrocene) to the 3′ terminus of the aptamer, resulting in positive current modulation upon exposure to riboflavin down to pM levels.
Highlights
Development of sensing systems, whether they are for vapor or liquid states, small or large molecules, all need a scheme where highly selective detection can occur
This allows for the injection of electrons from the ferrocene molecules into the n-type ZnO semiconductor causing an increase in current upon riboflavin binding—termed the ON state AptaFET
The secondary structure adopted by the aptamer upon binding of its target, in this case riboflavin, can be transduced as an electrical signal due to the rearrangement of negative charges on the backbone of the DNA oligomer into a more compact structure on a semiconductor surface
Summary
Development of sensing systems, whether they are for vapor or liquid states, small or large molecules, all need a scheme where highly selective detection can occur. Different methods have been used to add selectivity to FET devices, such as controlling the gate voltage on metal-oxide nanowires [4], the addition of different materials such as polymers [5,6,7,8], small molecules [9], and membranes [10]. Another approach to impart selectivity is by taking inspiration from nature, by utilizing molecules such as antibodies, peptides, and oligonucleotide based (DNA or RNA) aptamers which are naturally designed to bind molecules with high specificity
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