Abstract
Potassium (K+) ion is an important biological substance in the human body and plays a critical role in the maintenance of transmembrane potential and hormone secretion. Several detection techniques, including fluorescent, electrochemical, and electrical methods, have been extensively investigated to selectively recognize K+ ions. In this work, a highly sensitive and selective biosensor based on single-layer graphene has been developed for K+ ion detection under Van der Pauw measurement configuration. With pre-immobilization of guanine-rich DNA on the graphene surface, the graphene devices exhibit a very low limit of detection (≈1 nM) with a dynamic range of 1 nM–10 μM and excellent K+ ion specificity against other alkali cations, such as Na+ ions. The origin of K+ ion selectivity can be attributed to the fact that the formation of guanine-quadruplexes from guanine-rich DNA has a strong affinity for capturing K+ ions. The graphene-based biosensors with improved sensing performance for K+ ion recognition can be applied to health monitoring and early disease diagnosis.
Highlights
Potassium (K+ ) ion is predominantly an intracellular cation in biological systems [1,2], and is involved in various physiological and pathological events, including enzyme activation, Materials 2018, 11, 399; doi:10.3390/ma11030399 www.mdpi.com/journal/materialsMaterials 2018, 11, 399 nervous transmission, blood pressure/pH regulation, membrane potential modulation in living cells, etc. [3,4]
The layer number and quality of graphene films were identified as presented in Figure 1a–c, because both of them significantly affected the performance of graphene-based biosensors [29]
(1.98), and the narrow full-width at half-maximum of 2D-band (≈38 cm−1 ) demonstrate the nature of high-quality single-layer graphene prepared by the catalytic CVD method
Summary
Potassium (K+ ) ion is predominantly an intracellular cation in biological systems [1,2], and is involved in various physiological and pathological events, including enzyme activation, Materials 2018, 11, 399; doi:10.3390/ma11030399 www.mdpi.com/journal/materialsMaterials 2018, 11, 399 nervous transmission, blood pressure/pH regulation, membrane potential modulation in living cells, etc. [3,4]. Zeng et al fabricated an electrochemical transducer based on hydrothermal synthesized MoS2 nanoflowers that had a detection limit of ≈3.2 μM for determining K+ ions [14]. Lu et al synthesized Fe3 O4 /C core-shell nanoparticles grafted with guanine-rich oligonucleotides as a fluorescent sensing platform, which exhibited high sensitivity as low as 1.3 μM for K+ ion analysis [15]. In previous reports, the limited selectivity against sodium ions and the low detection sensitivity (commonly ≈μM) may restrict their clinical applications. It is of great importance and is a significant challenge to develop a nanobiosensor for highly sensitive and selective detection of K+ ions in aqueous environments.
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