Influence of the Electrolyte Salt Concentration on DNA Detection with Graphene Transistors

Abstract

Liquid-gated Graphene Field-Effect Transistors (GFET) are ultrasensitive bio-detection platforms carrying out the graphene’s exceptional intrinsic functionalities. Buffer and dilution factor are prevalent strategies towards the optimum performance of the GFETs. However, beyond the Debye length (λD), the role of the graphene-electrolytes’ ionic species interactions on the DNA behavior at the nanoscale interface is complicated. We studied the characteristics of the GFETs under different ionic strength, pH, and electrolyte type, e.g., phosphate buffer (PB), and phosphate buffer saline (PBS), in an automatic portable built-in system. The electrostatic gating and charge transfer phenomena were inferred from the field-effect measurements of the Dirac point position in single-layer graphene (SLG) transistors transfer curves. Results denote that λD is not the main factor governing the effective nanoscale screening environment. We observed that the longer λD was not the determining characteristic for sensitivity increment and limit of detection (LoD) as demonstrated by different types and ionic strengths of measuring buffers. In the DNA hybridization study, our findings show the role of the additional salts present in PBS, as compared to PB, in increasing graphene electron mobility, electrostatic shielding, intermolecular forces and DNA adsorption kinetics leading to an improved sensitivity.

“Silicon-On-Insulator”-Based Nanosensor for the Revelation of MicroRNA Markers of Autism

“…In the experiments on the SOI-NS-based detection of model target oDNAs in purified test solutions, the time dependencies of the current Δ I ds (t) were recorded in real time at fixed V g = 50 V. Moreover, 1 mM potassium phosphate buffer was employed as the working medium in order to avoid the Debye screening problem, since at such salt concentration, the Debye length λ D amounts to ~6.65 nm, being sufficient for the successful registration of (probe oDNA)/(target oDNA) complex formation on the NS surface [ 39 , 40 ].…”

“…In order to avoid problems associated with the influence of the Debye screening, the electrical detection experiments were performed with the use of a low-salt (1 mM) buffer. At such a low concentration of buffer salts, λ D amounts to ~6.65 nm, and this is sufficient for the registration of a nucleic acid on the NW surface [ 40 ]. At higher concentrations of buffer salts, the electric double layer becomes shorter than the length of the DNA duplex ( λ D = 6.65 nm for 1 mM phosphate buffer), thus leading to a decrease in the detection sensitivity, since the hybridization partially occurs outside the electric double layer region [ 40 ].…”

“…In order to account for the non-specific binding, an NS devoid of immobilized oDNA probes and located within the same NS array was used as a reference NS. tion, the Debye length λD amounts to ~6.65 nm, being sufficient for the successful registration of (probe oDNA)/(target oDNA) complex formation on the NS surface [39,40].…”

The Challenges of Developing Biosensors for Clinical Assessment: A Review

“…Other attempts include downscaling the sensing area into two-dimensional (2D) or one-dimensional (1D) structures [60][61][62][63]. The 2D materials for the advanced sensing structure can be graphene [38,64,65], which enhances the detection down to attomolar and femtomolar ranges [66][67][68]. Other 2D materials, such as molybdenum disulfide (MoS 2 ), were reported to be able to boost the detection down to the femtomolar range for protein [69] and DNA detection [70].…”

The challenges of developing biosensors for clinical assessment: a review

“…Other attempts are by downscaling the sensing area into two-dimensional (2D) or onedimensional (1D) structures [60][61][62][63]. The 2D materials for the advanced sensing structure can be graphene [38,64,65] that enhances the detection down to attomolar to femtomolar ranges [66][67][68]. Other 2D materials, such as molybdenum disulfide (MoS2) reported being able to boost the detection down to the femtomolar range for protein [69] dan DNA detection [70], respectively.…”