title: Development of an electrochemical insulin sensor based on the insulin-linked polymorphic region.
abstract: Here we report the design and fabrication of an electrochemical aptamer-based (E-AB) sensor for detection of insulin. The aptamer used in this study is the insulin-linked polymorphic region (ILPR) sequence, a G-rich sequence that presumably undergoes ligand-induced folding to form a G-quadruplex in presence of insulin. Our circular dichroism data, however, suggests that the ILPR sequence, even in absence of the target, is predominantly in a G-quadruplex-like form. Insulin binding, however, has shown to further induce the formation of the G-quadruplex. To evaluate the potential of the ILPR sequence as a biosensing element, we constructed two E-AB insulin sensors that are identical in all aspects but the location of the methylene blue (MB) redox label. We find that the sensor fabricated with internal MB-modified probes (In-IT) shows enhanced sensing behavior when compared to one fabricated using terminal-MB modified probes (In1). The improvements observed with the In-IT sensor could be attributed to the more effective obstruction of electron transfer upon insulin binding. Overall, both sensors perform well, affording a detection limit of 10 nM and 50 nM for the In-IT and In1 sensors, respectively.
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE 68588-0304, USA.
authors.forename: Jennifer Y
authors.initials: JY
authors.lastname: Gerasimov
authors.forename: Cody S
authors.initials: CS
authors.lastname: Schaefer
authors.forename: Weiwei
authors.initials: W
authors.lastname: Yang
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Grout
authors.forename: Rebecca Y
authors.initials: RY
authors.lastname: Lai
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry; D015374:Biosensing Techniques; D002942:Circular Dichroism; D054856:G-Quadruplexes; D006801:Humans; D007328:Insulin / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D011110:Polymorphism, Genetic
chemical_list: D052157:Aptamers, Nucleotide; D007328:Insulin