Large-Area Interfaces for Single-Molecule Label-free Bioelectronic Detection

Abstract

Bioelectronic transducing surfaces that are nanometric in size have been the main route to detect single molecules. Though enabling the study of rarer events, such methodologies are not suited to assay at concentrations below the nanomolar level. Bioelectronic field-effect-transistors with a wide (μm 2 −mm 2 ) transducing interface are also assumed to be not suited, because the molecule to be detected is orders of magnitude smaller than the transducing surface. Indeed, it is like seeing changes on the surface of a one-kilometer-wide pond when a droplet of water falls on it. However, it is a fact that a number of large-area transistors have been shown to detect at a limit of detection lower than femtomolar; they are also fast and hence innately suitable for point-of-care applications. This review critically discusses key elements, such as sensing materials, FET-structures, and target molecules that can be selectively assayed. The amplification effects enabling extremely sensitive large-area bioelectronic sensing are also addressed.

A large-area organic transistor with 3D-printed sensing gate for noninvasive single-molecule detection of pancreatic mucinous cyst markers

“…The nominal number of MUC1 or KRAS (#Ligand) at each concentration is given by cVN A , where c is the ligand concentration, V is the volume of the standard PBS solution in which the gate is incubated (100 μL) and N A is the Avogadro number. Indeed, the 3D sensing gate was incubated into an aliquot of 100 μL of the ligand standard solution, as customary in single-molecule wide-field detection techniques [ 12 , 26 ]. The error associated with the sampling procedure can be estimated according to the Poisson distribution.…”

“…In addition, the latter exhibited LOD down to the attomolar level (aM, 10 −18 M), with a response time shorter than hundreds of seconds. As demonstrated by several research groups [ 26 ], a single molecule in 100 μl (concentration of ~ 10–20 zM) undergoes diffusion and eventually impinging at millimeter-wide surface populated with trillions of recognition elements within a timescale of minutes. It was recently demonstrated how at least one out of a few molecules (< 10) diffusing in a large volume can impinge within 10 min on the large interface, generating a detectable signal at the LOD [ 30 ].…”

The Use of Excess Electric Charge for Highly Sensitive Protein Detection: Proof of Concept

“…The lower limit of detection (LOD) attainable with the use of these methods, however, does not allow one to perform reliable detection of the majority of diagnostically relevant markers of socially significant human diseases such as cancer [2]. Rissin et al [2] justified that for early diagnosis of socially significant diseases, the highest attainable LOD value must be 10 −15 M. Furthermore, Macchia et al emphasized that this LOD value should be as low as possible-down to the single-molecule level in an ideal case [4]. The latter is particularly important since the presence of even a single biomolecule, whose behavior differs from that of the majority of biomolecules, can determine the specific performance of the entire system, and this is crucial for clinical diagnosis [4,5].…”

“…The first factor is the sensitivity of the detector employed in the bioanalytical system; the second factor is the efficiency of the delivery of the target biomolecules to a sensitive surface of a sensor element of the detector [6]. Accordingly, the LOD threshold reported by Rissin et al [2] can be overcome with the use of so-called molecular detectors, which allow one to register a reliable signal from single biomolecules of target biomarkers [1,4,6].…”

“…Upon hydrodynamic intensification at ultra-low concentrations, the time required to capture a sufficient amount of target biomolecules is fairly long (up to several hours [14]). In contrast, upon application of an electric field, the capturing process is typically much faster [3][4][5], allowing one to detect the target biomolecules in real time [10,19,20]. This is why herein we consider the latter factor-the application of an electric field for the enhancement of transport of target biomolecules towards the sensitive surface of a detection system.…”