Label-free biomolecular detection at electrically displaced liquid interfaces using interfacial electrokinetic transduction (IET)

Abstract

Biosensors require a biorecognition element that specifically binds to a target analyte, and a signal transducer, which converts this targeted binding event into a measurable signal. While current biosensing methods are capable of sensitively detecting a variety of target analytes in a laboratory setting, there are inherent difficulties in developing low-cost portable biosensors for point-of-care diagnostics using traditional optical, mass, or electroanalytical-based signal transducers. It is therefore important to develop new biosensing transducer elements for recognizing binding events at low cost and in portable environments. Here, we demonstrate a novel electrokinetic liquid biosensing method for the sensitive label-free detection of a model biomolecule against a background of serum protein. The biosensor is based on the motion of a microfluidic-generated electrical liquid interface when subjected to an external alternating current electrical field. We demonstrate that the electric field-induced motion of the interface can be used as a sensitive and specific transducer for the detection of avidin at femtomolar concentrations in solution. This new detection strategy does not require surface functionalization or fluorescent labels, and has the potential to serve as a sensitive low-cost method for portable biomarker detection.

Single-cell electro-phenotyping for rapid assessment of Clostridium difficile heterogeneity under vancomycin treatment at sub-MIC (minimum inhibitory concentration) levels

“…Traditional metrics to quantify antibiotic susceptibility based on the half maximal inhibitory concentration (IC50) or minimum inhibitory concentration (MIC) are end-point measurements, which are not suited towards detecting heterogeneity in responses within a fluctuating environment. Singlecell techniques, on the other hand, for electrophysiology-based phenotypic analysis within a droplet [32] or by using impedance [33], [34], [35], or electro-rotational analysis [36], [37], are capable of quantifying subpopulations, but they have not been applied towards studying microbial heterogeneity after antibiotic treatments. In prior work, we have demonstrated that C. difficile cell wall capacitance measurements can identify subtle alterations in S-layer glycoproteins, which can occur due to strain-based morphological differences [38] or due to cell wall reconstitution under probiotic interactions [39], and which are correlated to the colonization ability of C. difficile [40].…”

Nanoparticle-based biosensing using interfacial electrokinetic transduction

“…In previous work, we demonstrated that biomolecular binding in solution without nanoparticles produces a local increase in electrical conductivity difference across the liquid interface. 24 This was demonstrated this by measuring the magnitude of the interfacial deflection for different analyte concentrations during binding.…”

“…23 Exploiting this phenomena, we demonstrated that biomolecular binding influences the electrical conductivity at the liquid interface, and that binding can be dynamically detected by monitoring interfacial deflection at varying positions down the microchannel. 24 Biorecognition is transduced as a change in electrokinetically-induced interfacial deflection in a process we have described as interfacial electrokinetic transduction (IET). 24 This approach was used to detect model avidin:biotin biomolecular binding at avidin concentrations as low as 50 femtomolar (fM), enabling it to compete with methods like surface plasmon resonance (SPR) (3 nm to 1.5 fM) 25 and enzyme-linked immunosorbent assays (ELISAs) (100 fM and below) 26 , which are the current standard of clinical sensitivity.…”

Nanomaterial-based biosensors for biological detections

“…In addition, as demands increase, all constituents in the biosensors can be designed and manufactured in large quantities at a low cost to satisfy the needs of users. 1 In 1953, Clark et al 2 first published a paper containing the fundamental ideas of a "biosensor". Moreover, in 1967, Updike and Hicks 3 successfully reported a biosensor for glucose detection.…”