The role of surface charge and binding properties in silicon-based field effect nanowire biosensors

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.

Download Full-text

Elucidating the Role of Water‐Related Traps in the Operation of Polymer Field‐Effect Transistors

Advanced Electronic Materials ◽

10.1002/aelm.202100393 ◽

2021 ◽

pp. 2100393

Author(s):

Hamna F. Iqbal ◽

Matthew Waldrip ◽

Hu Chen ◽

Iain McCulloch ◽

Oana D. Jurchescu

Keyword(s):

Field Effect ◽

Field Effect Transistors

Download Full-text

Human Rev1 relies on insert-2 to promote selective binding and accurate replication of stabilized G-quadruplex motifs

Nucleic Acids Research ◽

10.1093/nar/gkab041 ◽

2021 ◽

Author(s):

Amit Ketkar ◽

Lane Smith ◽

Callie Johnson ◽

Alyssa Richey ◽

Makayla Berry ◽

...

Keyword(s):

Amino Acids ◽

Mutation Frequency ◽

Control Sequence ◽

Wild Type ◽

Binding Properties ◽

High Affinity ◽

G4 Dna ◽

G Quadruplex ◽

Forward Mutagenesis

Abstract We previously reported that human Rev1 (hRev1) bound to a parallel-stranded G-quadruplex (G4) from the c-MYC promoter with high affinity. We have extended those results to include other G4 motifs, finding that hRev1 exhibited stronger affinity for parallel-stranded G4 than either anti-parallel or hybrid folds. Amino acids in the αE helix of insert-2 were identified as being important for G4 binding. Mutating E466 and Y470 to alanine selectively perturbed G4 binding affinity. The E466K mutant restored wild-type G4 binding properties. Using a forward mutagenesis assay, we discovered that loss of hRev1 increased G4 mutation frequency >200-fold compared to the control sequence. Base substitutions and deletions occurred around and within the G4 motif. Pyridostatin (PDS) exacerbated this effect, as the mutation frequency increased >700-fold over control and deletions upstream of the G4 site more than doubled. Mutagenic replication of G4 DNA (±PDS) was partially rescued by wild-type and E466K hRev1. The E466A or Y470A mutants failed to suppress the PDS-induced increase in G4 mutation frequency. These findings have implications for the role of insert-2, a motif conserved in vertebrates but not yeast or plants, in Rev1-mediated suppression of mutagenesis during G4 replication.

Download Full-text

The role of membrane surface charge and solute physico-chemical properties in the rejection of organic acids by NF membranes

Journal of Membrane Science ◽

10.1016/j.memsci.2004.09.041 ◽

2005 ◽

Vol 249 (1-2) ◽

pp. 227-234 ◽

Cited By ~ 211

Author(s):

Christopher Bellona ◽

Jörg E. Drewes

Keyword(s):

Organic Acids ◽

Surface Charge ◽

Membrane Surface ◽

Chemical Properties ◽

Physico Chemical ◽

Membrane Surface Charge

Download Full-text

Transport of Ions and Molecules in Nanofluidic Devices

ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2008-62065 ◽

2008 ◽

Author(s):

Rohit Karnik ◽

Chuanhua Duan ◽

Kenneth Castelino ◽

Rong Fan ◽

Peidong Yang ◽

...

Keyword(s):

Surface Charge ◽

Surface Area ◽

Field Effect ◽

Electrostatic Interactions ◽

Surface Reactions ◽

Molecular Transport ◽

Large Surface Area ◽

Ionic Concentrations ◽

Nanofluidic Devices ◽

Transport Of Ions

Interesting transport phenomena arise when fluids are confined to nanoscale dimensions in the range of 1–100 nm. We examine three distinct effects that influence ionic and molecular transport as the size of fluidic channels is decreased to the nanoscale. First, the length scale of electrostatic interactions in aqueous solutions becomes comparable to nanochannel size and the number of surface charges becomes comparable to the number of ions in the channel. Second, the size of the channel becomes comparable to the size of biomolecules such as proteins and DNA. Third, large surface area-to-volume ratios result in rapid rates of surface reactions and can dramatically affect transport of molecules through the channel. These phenomena enable us to control transport of ions and molecules in unique ways that are not possible in larger channels. Electrostatic interactions enable local control of ionic concentrations and transport inside nanochannels through field effect in a nanofluidic transistor, which is analogous to the metal-oxide-semiconductor field effect transistor. Furthermore, by controlling surface charge in nanochannels, it is possible to create a nanofluidic diode that rectifies ionic transport through the channel. Biological binding events result in partial blockage of the channel, and can thus be sensed by a decrease in nanochannel conductance. At low ionic concentrations, the effect of biomolecular charge is dominant and it can lead to an increase in conductance. Surface reactions can also be used to control transport of molecules though the channel due to the large surface area-to-volume ratios. Rapid surface reactions enable a new technique of diffusion-limited patterning (DLP), which is useful for patterning of biomolecules and surface charge in nanochannels. These examples illustrate how electrostatic interactions, biomolecular size, and surface reactions can be used for controlling ionic and molecular transport through nanochannels. These phenomena may be useful for operations such as analyte focusing, pH and ionic concentration control, and biosensing in micro- and nanofluidic devices.

Download Full-text