Electrochemical-aptamer based (E-AB) sensors represent a universal specific, selective, and sensitive sensing platform for the detection of small molecule targets. Their specific detection abilities are afforded by oligonucleotide (RNA or DNA) aptamers employed as electrode-bound biorecognition elements. Sensor signaling is predicated on bindinginduced changes in conformation and/or flexibility of the aptamer that is readily measurable electrochemically. While sensors fabricated using DNA aptamers can achieve specific and selective detection even in unadulterated sample matrices, such as blood serum, RNA-based sensors fail when challenged in the same sample matrix without significant sample pretreatment. This failure is at least partially a result of enzymatic degradation of the RNA sensing element. This degradation destroys the sensing aptamer inhibiting the quantitative measurement of the target analyte and thus limits the application of E-AB sensors constructed with RNA aptamer. To circumvent this, we demonstrate that a biocompatible hydrogel membrane protects the RNA aptamer sensor surface from enzymatic degradation for at least 3 hours - a remarkable improvement over the rapid (~minutes) degradation of unprotected sensors. To demonstrate this, we characterize the response of sensors fabricated with representative DNA and RNA aptamers directed against the aminoglycoside antibiotic, tobramycin in blood serum both protected and unprotected by a polyacrylamide membrane. Furthermore, we find encapsulation of the sensor surface with the hydrogel does not significantly impede the detection ability of aptamer-based sensors. This hydrogel-aptamer interface will thus likely prove useful for the long-term monitoring of therapeutics in complex biological media.
Electrochemical aptamer-based sensors (E-AB sensors) represent a promising new approach to the detection of small
molecules. E-AB sensors comprise an aptamer that is attached at one end to an electrode surface. The distal end of the
aptamer probed is modified with an electroactive redox marker for signal transduction. Herein we report on the
optimization of a cocaine-detecting E-AB sensor via optimization of the geometry of the aptamer. We explore two new
aptamer architectures, one in which we concatenate three cocaine aptamers into a poly-aptamer and a second in which
we divide the cocaine aptamer into pieces connected via an unstructured, 60-thymine linker. Both of these structures are
designed such that the reporting redox tag will be located farther from the electrode in the unfolded, target-free
conformation. Consistent with this, we find that signal gains of these two constructs are two to three times higher than
that of the original E-AB architecture. Likewise all three architectures are selective enough to deploy directly in complex
sample matrices, such as undiluted whole blood, with all three sensors successfully detecting the presence of cocaine.
The findings in this ongoing study should be of value in future efforts to optimize the signaling of electrochemical
aptamer-based sensors.
Conference Committee Involvement (5)
Smart Biomedical and Physiological Sensor Technology XIV
9 April 2017 | Anaheim, CA, United States
Smart Biomedical and Physiological Sensor Technology XIII
18 April 2016 | Baltimore, MD, United States
Smart Biomedical and Physiological Sensor Technology XII
23 April 2015 | Baltimore, MD, United States
Smart Biomedical and Physiological Sensor Technology XI
7 May 2014 | Baltimore, MD, United States
Smart Biomedical and Physiological Sensor Technology X
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