Time-encoded electrical detection of trace RNA biomarker by integrating programmable molecular amplifier on chip.

One of the serious challenges facing modern point-of-care (PoC) molecular diagnostic platforms relate to reliable detection of low concentration biomarkers such as nucleic acids or proteins in biological samples. Non-specific analyte-receptor interactions due to competitive binding in the presence of abundant molecules, inefficient mass transport and very low number of analyte molecules in sample volume, in general pose critical hurdles for successful implementation of such PoC platforms for clinical use. Focusing on these specific challenges, this work reports a unique PoC biosensor that combines the advantages of nanoscale biologically-sensitive field-effect transistor arrays (BioFET-arrays) realized in a wafer-scale top-down nanofabrication as high sensitivity electrical transducers with that of sophisticated molecular programs (MPs) customized for selective recognition of analyte miRNAs and amplification resulting in an overall augmentation of signal transduction strategy. The MPs realize a programmable universal molecular amplifier (PUMA) in fluidic matrix on chip and provide a biomarker-triggered exponential release of small nucleic acid sequences easily detected by receptor-modified BioFETs. A common miRNA biomarker LET7a was selected for successful demonstration of this novel biosensor, achieving limit of detection (LoD) down to 10 fM and wide dynamic ranges (10 pM-10 nM) in complex physiological solutions. As the determination of biomarker concentration is implemented by following the electrical signal related to analyte-triggered PUMA in time-domain instead of measuring the threshold shifts of BioFETs, and circumvents direct hybridization of biomarkers at transducer surface, this new strategy also allows for multiple usage (>3 times) of the biosensor platform suggesting exceptional cost-effectiveness for practical use.

Delineating charge and capacitance transduction in system-integrated graphene-based BioFETs used as aptasensors for malaria detection.

Despite significant eradication efforts, malaria remains a persistent infectious disease with high mortality due to the lack of efficient point-of-care (PoC) screening solutions required to manage low-density asymptomatic parasitemia. In response, we demonstrate a quantitative electrical biosensor based on system-integrated two-dimensional field-effect transistors (2DBioFETs) of reduced graphene oxide (rGO) as transducer for high sensitivity screening of the main malaria biomarker, Plasmodium falciparum lactate dehydrogenase (PfLDH). The 2DBioFETs were biofunctionalized with pyrene-modified 2008s aptamers as specific PfLDH receptors. While we systematically optimize biosensor interface for optimal performance, aptamer-protein transduction at 2DBioFETs is elucidated based on delineation of charge and capacitance in an updated analytical model for two-dimensional rGO/biofunctional layer/electrolyte (2DiBLE) interfaces. Our 2DBioFET-aptasensors display a limit-of-detection down to 0.78 fM (0.11 pg/mL), dynamic ranges over 9 orders of magnitude (subfemto to submicromolar), high sensitivity, and selectivity in human serum validating their diagnostic potential as rapid PoC tests for malarial management.