fM Sensitivity Research Articles

A single gate Si1−xGex dopingless TFET functioned as an effective label-free biosensor

This paper examines the sensitivity of a newly presented heterojunction dopingless tunnel field effect transistor (HJ-DLTFET) biosensor for the label-free detection of biomolecules. The etched nanocavity is introduced in the source metal region for better sensing ability. The dielectric constants (k) of five neutral biomolecules are employed in this paper to test the sensitivity of the proposed biosensor. The electrostatic performance is investigated based on transfer characteristics, energy band, tunneling distance (λ) at source/channel (S/C) interface, drain current (ID) variation for different dielectric constant (k), drain to source voltage (VDS) variation and mole fraction (x) variation respectively. Further, the RF performance analysis includes gate/source capacitance (Cgs), total gate capacitance (Cgg), cut-off frequency (ft), and maximum frequency (fm) analysis. Similarly, sensitivity analysis consists of current sensitivity (SID), current ratio sensitivity (Sratio), average SS sensitivity (SSS), Cgs sensitivity, Cgg sensitivity, ft sensitivity, and fm sensitivity. The investigation is carried out with the variation of neutral biomolecules in terms of various k inside the cavity. Similarly, the impact of charged biomolecules on the sensitivity of the proposed biosensor is investigated. The HJ-DLTFET sensor provides the maximum sensitivity SID of 1.56 × 1010, Sratio of 5.95 × 109, and SSS of 0.80 for Gelatin (k = 12.00) at room temperature using the Silvaco TCAD simulation tool. Combining a low band gap Si0.6Ge0.4 source with a high band gap silicon channel and a high-k (HfO2) improves drain current sensitivity without impacting leakage current.

Ultrasensitive Detection of Organophosphorus Pesticides Using Single-Molecule Conductance Measurement.

Detection of organophosphorus pesticides (OPs) with high sensitivity in environmental samples is of vital importance for environmental safety and human health. However, it remains a challenge to achieve fM (10-15 mol/L) sensitivity for detecting OPs. Herein, we developed an acetylcholinesterase sensor based on 3,3',5,5'-tetramethylbenzidine (TMB) combining an enzyme-mediated strategy and scanning tunneling microscopy break junction (STM-BJ). Benefiting from the enzyme inhibition kinetics of OPs and the customized spectral clustering analysis method, our new strategy achieved the detection of methamidophos (MTMP) with a limit of 10 aM (10-17 mol/L) and 3 times higher selectivity in mixed OPs. As applied to natural lake waters, it also exhibited high reproducibility, high stability, and good recovery. This work paves a new avenue toward the application of single-molecule conductance characterizations for biochemical analysis and environmental monitoring.

Sequence-specific capture and concentration of viral RNA by type III CRISPR system enhances diagnostic

Type-III CRISPR-Cas systems have recently been adopted for sequence-specific detection of SARS-CoV-2. Here, we repurpose the type III-A CRISPR complex from Thermus thermophilus (TtCsm) for programmable capture and concentration of specific RNAs from complex mixtures. The target bound TtCsm complex generates two cyclic oligoadenylates (i.e., cA3 and cA4) that allosterically activate ancillary nucleases. We show that both Can1 and Can2 nucleases cleave single-stranded RNA, single-stranded DNA, and double-stranded DNA in the presence of cA4. We integrate the Can2 nuclease with type III-A RNA capture and concentration for direct detection of SARS-CoV-2 RNA in nasopharyngeal swabs with 15 fM sensitivity. Collectively, this work demonstrates how type-III CRISPR-based RNA capture and concentration simultaneously increases sensitivity, limits time to result, lowers cost of the assay, eliminates solvents used for RNA extraction, and reduces sample handling.

Modular, Portable, Automatically, Rapidly, Sensitive, and Selectively Essence Sensor System

The ESSENCE platform is an electrochemical sensor system that utilizes non-planar porous microelectrode microfluidic chips with a fully programmable fluidic/sample system to be a “portable, automatic, rapid, sensitive, and selective” for different emerging contaminants and liquid biopsy. The system is designed with non-planar porous microelectrode interfaces, containing different functional capturing probes for specific sensing tasks. From our previous report, this 3D non-planar structure has advantages such as increased flow’s convective fluxes and disrupts diffusive processes like the electric double layer (EDL). The porous electrode structure utilized the packing material’s higher Zeta potential than the bare glass surface, resulting in the EDL length will be significantly smaller than the clear channel. Due to a smaller EDL length, the relaxation frequency will increase, which shifts the EIS signal to a higher frequency range (1kHz to 100MHz) and results in a fast response with a higher signal-to-noise ratio in Electrochemical Impedance Spectroscopy (EIS) measurements. From the perspective of electric field penetration, the top-down electric direction covers all the packing sensing areas, providing a generally higher electronic signal response than the traditional planar electrode system, leading to a higher signal-to-noise ratio. A second feature from the perspective of microfluidics is the significant fluidic shear force generated due to flow through the porous electrode surface. This higher shear force on the surface can unbind most false-positive signals generated by non-specific binding, such as physical adhesive or biofouling. These unique benefits provide physical enhancements of sensitivity and selectivity without manipulating the chemical material in the system. Earlier we showed that our detection of the biomolecules like DNA (fM sensitivity, which can distinguish against a mismatched DNA), proteins (breast cancer biomarker p53, fM sensitivity, which can distinguish it against another breast cancer biomarker HER2), PFOS (Perfluorooctanesulfonate, 0.5 ng) under the traditional desktop Electrochemical Impedance Spectroscopy (EIS) analyzer in the total process of hourly. In this talk, we have further developed our previous ESSENCE platform to a modular, automatic, and portable, one-stop instrument for clinicians to screen for infectious diseases, liquid biopsy, and toxin detection to detect emerging pathogens while significantly reducing false positives and false negatives, but also decreasing our detecting process to 15 mins in much more hazard background conditions to meet the criteria of POC. Second, A small (15 cm x 17cm) USB programable fluidic/oscilloscope base with a 15 minutes total detecting protocol is applied to our ESSENCE system for a fast Point-of-care (POC) diagnostic. This portable ESSENCE platform can respond to the measurable EIS signals from the oscilloscope with 25 ul samples size (DNA and HER2 proteins in undiluted artificial Urine) with a fully automatic process at the uM to pM regions in 15 minutes. Each ESSENCE chip is also significantly cheaper than the ELISA; the chip costs about $20 (for an academic lab) and can be reused. Figure 1

Ligation-free isothermal nucleic acid amplification

In this study, we uncover a ligation-free DNA extension method in two adjacent fragmented probes, which are hybridized to target RNA, for developing a ligation-free nucleic acid amplification reaction. In this reaction, DNA elongation occurs from a forward probe to a phosphorothioated-hairpin probe in the presence of target RNA regardless of ligation. The second DNA elongation then occurs simultaneously at the nick site of the phosphorothioated probe and the self-priming region. Therefore, the binding site of the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) 12a is repeatedly amplified, inducing a fluorescence signal in the presence of CRISPR-Cas12a. This ligation-free isothermal gene amplification method enables the detection of target RNA with 49.2 fM sensitivity. Moreover, two types of mRNA detection are feasible, thus, demonstrating the potential of this method for cancer companion diagnostics. Notably, the proposed method also demonstrates efficacy when applied for the detection of mRNA extracted from human cells and tumor-bearing mouse tissue and urine samples. Hence, this newly developed ligation-free isothermal nucleic acid amplification system is expected to be widely used in a variety of gene detection platforms.

Paper based low-cost flexible SERS sensor for food adulterant detection

A simple in-situ one-step silver mirror reaction (SMR) was utilized for the growth of silver nanostructures (AgNS) on filter paper (P1,0.01; P2,0.1; and P3,0.2M AgNO 3 ) for SERS substrates. Concentration dependent growth of AgNS, with the evolution of multifaceted structures have been achieved. Further, SERS substrates were employed to detect Methylene blue (MB) and Crystal violet (CV) and fM sensitivity was achieved. Water spiked with melamine and urea were detected at limit of detection (LOD) of 0.1 mM; 0.2 mM concentrations, and for milk samples detection level was found to be 1.69 mM; 0.48mM respectively. Reproducibility of SERS sensor was achieved, with RSD values of <8% for water spiked samples, and for whole milk it was <12.28%. The achieved sensitivity and LODs for water and whole milk samples were found to be either superior or comparable with reported literature. Moreover, the stability of P3 SERS substrate was examined after 4 months for MB, CV, whole milk spiked with melamine and urea, and found to be ¿94% efficiency. Thus, the fabricated paper based SERS substrate, offers high sensitivity, selectivity, stability, and cost-effective approach, for on-site detection of chemical contaminant in water and milk samples. • Paper Based Low-cost Flexible SERS Sensor for Food Adulterant was demonstrated. • The paper sensor validated with MB and CV (LODs: 7.9 and 11.9) fM respectively. • Water spiked melamine and urea demonstrate sensitivity with 0.1 and 0.2 mM. • Whole milk spiked melamine and urea demonstrate sensitivity with 1.69 and 0.48 mM. • Stability of sensor was tested after 4 months and found >94% efficiency.

Essence - A New Electrochemical Platform

There is a great demand for a fast, on-site screening test, especially during the COVID-19 pandemic. However, most point-of-care (POC) sensors usually suffer from insufficient sensitivity and selectivity. Often these devices have a very high rate of false positives and false negatives. The incorrect data could result in low customer usage (both the patient and the doctor) due to decreased confidence in the results. Portable ELISA-based kits can have low rates of false-positive and false negatives. However, ELISA is inherently complicated and often requires a specialist on-site to ensure the success of each sample's high costs and time.Here we show a new electrochemical platform called ESSENCE. ESSENCE is an Electrochemical Sensor that uses a Shear-Enhanced, flow-through Nanoporous Capacitive Electrode. ESSENCE can overcome current electrochemical sensors' selectivity and sensitivity limitations. The ESSENCE sensor architecture is a microfluidic channel sandwiched between two gold micro-electrode glass slides, formed a non-planar interdigitated porous electrode that improved electric field penetration compared with the traditional planar interdigitated electrode. The porous electrode structure used in this research has a high Zeta potential compared to the bare glass surface. This results in a significantly smaller Debye double-layer (EDL) length than in a clear channel. Due to a smaller EDL length, the relaxation frequency increases, which shifts the EIS signal to a higher frequency range (1kHz to 100MHz) and results in a fast response with a higher signal-to-noise ratio in Electrochemical Impedance Spectroscopy(EIS) measurements.Further, the modular fabrication of the ESSENCE chip allows ESSENCE to target different biomolecules from DNAs to protein cancer biomarkers by simply changing the packed transducer material. However, the packing material’s conductivity represents a significant challenge to the electrochemical response of ESSENCE. The high conductivity of the transducer material shorts the system leading to a pure resistive response. Impedance spectroscopy (EIS) response of ESSENCE cannot be distinguished enough to determine if the sensor is working. ESSENCE has a switchable electrode system for usage in multiple configurations like a material electrode, clear electrode, and working electrode to overcome these limitations. For carbon nanotube (CNT) transducers with functionalized oligos on the CNT, a 20-fold jump in the signal is noticed from the working electrode configuration compared to the other configurations. It is worthwhile to note that depending on the biomolecule (DNA or Protein), the surface charge transfer resistance (Rct) in the EIS signal of ESSENCE can either show a decrease (DNA) or increase (protein) on the binding of the target bio-molecule (target DNA to DNA or target protein to protein). The change in the Rct depends on the charge of the molecule. It has been seen that on the binding of a target protein, the active area of the electrode surface decreased, leading to a reduction in current and a concomitant increase in Rct. On binding of the target DNA, the capture-target DNA pair essentially becomes a part of the electrode due to its charge. This increase in charge is more significant than any reduction in the surface area due to the DNA's binding. This leads to an increase in current to the packed electrode, leading to a concomitant decrease in Rct.The fluid flow through the porous electrode increases mixing, minimizes diffusion, and generates a significantly enhanced fluidic shear force. This force e can unbind most of the false-positive signals generated by non-specific binding, such as physical adhesive or biofouling. The porous electrode also provides a high surface area to volume ratio to capture the target analyte leading to increased sensitivity. We have an automatic fluidic control system in ESSENCE that minimized any errors in the operation of ESSENCE. Our system has high selectivity and sensitivity for DNA (fM sensitivity, selective against non-target DNA), breast cancer biomarker proteins (p53, pg/L sensitivity, selective against non-target HER2). Figure 1

ESSENCE – A rapid, shear-enhanced, flow-through, capacitive electrochemical platform for rapid detection of biomolecules

The rapid, sensitive, and selective detection of target analytes using electrochemical sensors is challenging. ESSENCE, a new Electrochemical Sensor that uses a Shear-Enhanced, flow-through Nanoporous Capacitive Electrode, overcomes current electrochemical sensors' response limitations, selectivity, and sensitivity limitations. ESSENCE is a microfluidic channel packed with transducer material sandwiched by a top and bottom microelectrode. The room-temperature instrument less integration process allows the switch of the transducer materials to make up the porous electrode without modifying the electrode architecture or device protocol. ESSENCE can be used to detect both biomolecules and small molecules by simply changing the packed transducer material. Electron microscopy results confirm the high porosity. In conjunction with the non-planar interdigitated electrode, the packed transducer material results in a flow-through porous electrode. Electron microscopy results confirm the high porosity. The enhanced shear forces and increased convective fluxes disrupt the electric double layer's (EDL) diffusive process in ESSENCE. This disruption migrates the EDL to high MHz frequency allowing the capture signal to be measured at around 100 kHz, significantly improving device timing (rapid detection) with a low signal-to-noise ratio. The device's unique architecture allows us multiple configuration modes for measuring the impedance signal. This allows us to use highly conductive materials like carbon nanotubes. We show that by combining single-walled carbon nanotubes as transducer material with appropriate capture probes, NP-μIDE has high selectivity and sensitivity for DNA (fM sensitivity, selective against non-target DNA), breast cancer biomarker proteins (p53, pg/L sensitivity, selective against non-target HER2).

Exploring the trans-cleavage activity of CRISPR-Cas12a for the development of a Mxene based electrochemiluminescence biosensor for the detection of Siglec-5

Sialic acid-binding immunoglobulin (Ig)-like lectins (Siglecs) is a type I transmembrane receptor on the cell surface. Siglec-5, as one of the Siglecs family, play an important role as an inhibitory receptor for leukocytes in the human body. The development of novel siglec-5 assays can help to study the pathogenesis of related diseases as well as to develop novel therapeutic drugs. We use catalytic hairpin assembly (CHA) amplification strategy combined with CRISPR-Cas12a′s side-cutting feature to build a 2D ultra-thin Ti3C2Tx (MXene) based electrochemiluminescence (ECL) biosensor for the detection of Siglec-5. By using this ECL biosensor, the cleavage of CRISPR-Cas12a is reasonably combined with CHA-mediated isothermal amplification, thereby realizing the sensitive amplification assay Siglec-5 with 20.22 fM sensitivity. By introducing pairs of sites that are not in the same double-stranded DNA into the DNA duplex, the hybridization sequence of CRISPR-Cas12a complements the targeting mechanism to enhance indirect Siglec-5 amplification assay. Also, the double-strand DNA (dsDNA) design based on CRISPR-Cas12a amplification allows the same CRISPR RNA (crRNA, also known as guide RNA (gRNA)) to detect the output of DNA duplexes from different intermediate DNAs, which provides a common way for biomarker detection based on the conversion of protein analytes to intermediate DNA strategy. This work extends the application scope of CRISPR-Cas12a to the construction of ECL biosensors, evaluates the role of lectins, which can be used for the biochemical research and clinical diagnosis of protein markers. This is the first investigative work exploring the Trans-Cleavage activity of CRISPR-Cas12a for Mxene-based ECL biosensor establishment to the best of our knowledge.

Divalent ion-induced aggregation of gold nanoparticles for voltammetry Immunosensing: comparison of transducer signals in an assay for the squamous cell carcinoma antigen.

A method is described for the electrochemical determination of squamous cell carcinoma (SCC) antigen, and by testing the effect of 30nm gold nanoparticles (GNPs). Three comparative studies were performed in the presence and absence of GNPs, and with agglomerated GNPs. The divalent ion Ca(II) was used to induce a strong agglomeration of GNPs, as confirmed by colorimetry and voltammetry. Herein, colorimetry was used to test the best amount of salt needed to aggregate the GNPs. Despite, voltammetry was used to determine the status of biomolecules on the sensor. The topography of the surface of ZnO-coated interdigitated electrodes was analyzed by using 3D-nano profilometry, scanning electron microscopy, atomic force microscopy and high-power microscopy. The interaction between SCC antigen and antibody trigger vibrations on the sensor and cause dipole moment, which was measured using a picoammeter with a linear sweep from 0 to 2V at 0.01V step voltage. The sensitivity level was 10 fM by 3σ calculation for the dispersed GNP-conjugated antigen. This indicates a 100-fold enhancement compared to the condition without GNP conjugation. However, the sensitivity level for agglomerated GNPs conjugated antibody was not significant with 100 fM sensitivity. Specificity was tested for other proteins in serum, namely blood clotting factor IX, C-reactive protein, and serum albumin. The SCC antigen was quantified in spiked serum and gave recoveries that ranged between 80 and 90%. Graphical abstractSchematic representation of SCC (squamous cell carcinoma) antigen determination using divalent ion induced agglomerated GNPs. Sensitivity increment depends on the occurrence of more SCC antigen and antibody binding event via GNPs integration. Notably, lower detection limit was achieved at femto molar with proper orientation of biological molecules.

Different Methods of Staining to optimize Smear Microscopy for Diagnosis of Pulmonary and Extra Pulmonary Tuberculosis

Introduction: Tuberculosis continues to be a major public health problem especially in low income and high incidence countries like India. Aim of the study was to access and compare sensitivity and specificity of Light emitting Diode Fluorescent Microscopy (LED FM) over Light microscopy (LM) for diagnosis of pulmonary (PTB) and extra pulmonary tuberculosis (EPTB). Methods: 1446 pulmonary and 328 extra pulmonary cases suspected of tuberculosis were included in the study. Sputum samples were collected on 2 successive days while only one EPTB specimen was received in the laboratory. Results: Out of 2767 sputum specimen and 328 EPTB specimen evaluated, 603 (21.79%) sputum and 16 (4.84%) EPTB respectively were grown on culture and considered positive for Mycobacterium Tuberculosis. The sensitivity for sputum samples from ZN stain direct smear and concentration sputum smear by LM was 57.88% and 67% respectively, while the specificity of both direct and concentration smears by LM ZN staining was 100%. In case of sputum samples sensitivity of LED FM has drastically increased to 82.09% and the specificity is only slightly lower than LM that is 99.88%. For EPTB sensitivity for direct smear by LM was found to be 12.50% and concentration smear was 18.75% with 100% specificity. With LED FM sensitivity was enhanced by 43.75% with only marginally less specificity as 99.67%. All differences between culture and smear positive were highly statistically significant. (P value

Sensitive and multiplexed on-chip microRNA profiling in oil-isolated hydrogel chambers.

Although microRNAs (miRNAs) have been shown to be excellent indicators of disease state, current profiling platforms are insufficient for clinical translation. Here, we demonstrate a versatile hydrogel-based microfluidic approach and novel amplification scheme for entirely on-chip, sensitive, and highly specific miRNA detection without the risk of sequence bias. A simulation-driven approach is used to engineer the hydrogel geometry and the gel-reaction environment is chemically optimized for robust detection performance. The assay provides 22.6 fM sensitivity over a three log range, demonstrates multiplexing across at least four targets, and requires just 10.3 ng of total RNA input in a 2 hour and 15 minutes assay.

Sensitive and Multiplexed On‐chip microRNA Profiling in Oil‐Isolated Hydrogel Chambers

AbstractAlthough microRNAs (miRNAs) have been shown to be excellent indicators of disease state, current profiling platforms are insufficient for clinical translation. Here, we demonstrate a versatile hydrogel‐based microfluidic approach and novel amplification scheme for entirely on‐chip, sensitive, and highly specific miRNA detection without the risk of sequence bias. A simulation‐driven approach is used to engineer the hydrogel geometry and the gel‐reaction environment is chemically optimized for robust detection performance. The assay provides 22.6 fM sensitivity over a three log range, demonstrates multiplexing across at least four targets, and requires just 10.3 ng of total RNA input in a 2 hour and 15 minutes assay.

SAT0392 Clinical Features of Fibromyalgia and Chronic Widespread Pain Syndrome in Patients with Mild Psoriasis. Application and Comparison of the 1990 and 2010 ACR Classification Criteria

BackgroundFibromyalgia (FM) is a frequent cause of chronic widespread pain (CWP). Although its occurrence in psoriatic subjects represents a clinical challenge in terms of diagnosis and management, such issue is...

Sensitive SNP Detection of KIF6 Gene by Quantum Dot-DNA Conjugate Probe-Based Assay

In recent years, quantum dots (QDs) have been widely used in numerous biological processes and bio-analysis as novel fluorescence indicators. In the study, we developed a quantum dot-based bio-barcode amplification in combination with a Taq DNA ligase approach for the rapid detection of a polymorphism in kinesin-like protein 6 gene (KIF6), which significantly enhances the sensitivity. A ligand-exchange reaction was performed to prepare MPA-functionalized water-soluble QDs. The amine-modified oligonucleotides were coupled to QDs surface to form functional QDs-DNA conjugates. Meanwhile, the surface of gold nanoparticles (AuNPs) was modified with both the detection probe and bio-barcode oligonucleotides. Then, the amine-modified capture DNAs were immobilized onto the chip, followed by the addition of the modified AuNPs to the modified chip surface to form sandwiched hybridization. When the capture DNA and detection probe were perfectly matched to target DNA (KIF6), Taq DNA ligase in the solution would link the gap between the two strands, resulting in a covalent linkage. The preprepared QDs-DNA conjugation was subsequently added into the system to eventually form the fluorescence assembly. There was a good linear relationship between the target DNA (KIF6) concentration (1pM to 1fM) and ΔG of spot on chip. The ΔG of single base mismatch group was far less than that of completely complementary group. The method of QD-based bio-barcode amplification can provide a detection limit with low fM sensitivity for the detection of KIF6 DNA samples.

Selective and Sensitive TNT Sensors Using Biomimetic Polydiacetylene-Coated CNT-FETs

Miniaturized smart sensors that can perform sensitive and selective real-time monitoring of target analytes are tremendously valuable for various sensing applications. We developed selective nanocoatings by combining trinitrotoluene (TNT) receptors bound to conjugated polydiacetylene (PDA) polymers with single-walled carbon nanotube field-effect transistors (SWNT-FET). Selective binding events between the TNT molecules and phage display derived TNT receptors were effectively transduced to sensitive SWNT-FET conductance sensors through the PDA coating layers. The resulting sensors exhibited an unprecedented 1 fM sensitivity toward TNT in real time, with excellent selectivity over various similar aromatic compounds. Our biomimetic receptor coating approach may be useful for the development of sensitive and selective micro- and nanoelectronic sensor devices for various other target analytes.

Detection of Hepatitis B Virus Deoxyribonucleic Acid Based on Gold Nanoparticle Probe Chip

Abstract Nanoparticle-based bio-barcode amplification (BCA) approach was developed for the sensitive detection of hepatitis B virus (HBV) DNA. The BCA approach employed two sets of particles: (1) two-component oligonucleotide-modified gold nanoparticles (AuNPs): one oligonucleotide probe called signal probe (barcode DNA) is partially complementary with the target sequence of HBV DNA, and another one called detection probe is partially complementary with the signal probe; (2) single component oligonucleotide-modified magnetic microparticles (MMPs). In the presence of the target molecule, the gold nanoparticles and magnetic particles formed sandwich hybrids. Along with the isolation of sandwiched hybrids from the sample using a magnet, nonspecific-bound gold nanoparticles were removed, ensuring that only target-bound gold nanoparticles were collected. Subsequently, the bar-code DNAs were dehybridized from the gold nanoparticle by using the dithiothreitol (DTT). The detection probe with AuNP mixed with bar-code DNA solution was then added to a bar-code capture DNA-modified chip, and the spots on chip were labeled with bar-code DNA strands and AuNP probes. Finally, the scanometric detection of silver stain was introduced to further amplify the signal. The results showed that it was possible in a format that offers low fM (10−15 M) sensitivity in the detection of HBV DNA sample, and there is a good linear relationship between target concentration and spot intensity on chip. The detection of the assay could be fulfilled within 1.5 h. The method could provide a new generation of diagnostic assays for HBV or the other infectious disease.

Scrutiny on Significant Factors of Hemin Catalyzed Ag Nanoparticle as Biosensor for RNA

A responsive electrical detection technique of nucleic acids has been demonstrated on submicrogapped biosensor. This method contain immobilizing of Peptide Nucleic Acid (PNA) probes in the gap areas of a pair of interdigited microelectrodes and subsequently hybridizing with their complementary target RNA. After hybridization, hemin molecules were introduced into the RNA strand via zirconium-phosphate and zirconium-carbonate chemistries. The newly attached hemin molecules act as a catalyst to accelerate reducing ammoniacal Ag ion to form Ag nanoparticles, which span the gap of the interdigitated microelectrode. The conductance of the Ag nanoparticles directly correlated with the number of the hybridized RNA molecules. Nearly 1 fM sensitivity was achieved under optimal conditions.

Scrutiny on Significant Factors of Hemin Catalyzed Ag Nanoparticle as Biosensor for RNA

A responsive electrical detection technique of nucleic acids has been demonstrated on submicrogapped biosensor. This method contain immobilizing of Peptide Nucleic Acid (PNA) probes in the gap areas of a pair of interdigited microelectrodes and subsequently hybridizing with their complementary target RNA. After hybridization, hemin molecules were introduced into the RNA strand via zirconium-phosphate and zirconium-carbonate chemistries. The newly attached hemin molecules act as a catalyst to accelerate reducing ammoniacal Ag ion to form Ag nanoparticles, which span the gap of the interdigitated microelectrode. The conductance of the Ag nanoparticles directly correlated with the number of the hybridized RNA molecules. Nearly 1 fM sensitivity was achieved under optimal conditions.

Direct Electrocatalytic mRNA Detection Using PNA-Nanowire Sensors

We report an electrochemical nucleic acids sensing system that exhibits high sensitivity and specificity when challenged with heterogeneous samples of RNA. The platform directly detects specific RNA sequences in cellular and clinical samples without any sample labeling or PCR amplification. The sensor features an electrode platform consisting of three-dimensional gold nanowires, and DNA or RNA hybridization is detected using an electrocatalytic reporter system. In this study, probes made of peptide nucleic acid (PNA) are used to detect a newly identified cancer biomarkera gene fusion recently associated with prostate cancer. The system is able to detect the fusion sequence with 100 fM sensitivity, and retains high sensitivity even in the presence of a large excess of non-complementary sequences. Moreover, the sensor is able to detect the fusion sequence in as little as 10 ng of mRNA isolated from cell lines or 100 ng total RNA from patient tissue samples. The PNA-nanowire nucleic acids sensor described is one of the first electrochemical sensors to directly detect specific mRNAs in unamplified patient samples.