Ravikiran Reddy

Nanomonitors: Protein Biosensors for Rapid Analyte Analysis

A technology for electrical detection of proteins has been developed using electrical conductance measurements. It is based on developing high density, low-volume multiwell plate devices. The scientific core of this technology lies in integrating nanoporous membranes with microfabricated chip platforms. This results in the conversion of individual pores into wells of picoliter volume. Specific antibodies are localized and isolated into individual wells. The formation of the antibody-antigen binding complex occurs in individual wells. The membrane allows for robust separation among individual wells. This technology has the capability to achieve near real-time detection with improved sensitivity and selectivity.

Iridium oxide nanomonitors: clinical diagnostic devices for health monitoring systems.

The objective of this research is to demonstrate the potential of iridium oxide (IrOx) nanowires based device towards detection of proteins that are disease biomarkers. This device is based on electrical detection of protein biomarkers wherein an immunoassay is built onto the iridium oxide nanowires that in turn undergoes specific electrical parameter perturbations during each binding event associated with the immunoassay. Detection of two inflammatory proteins C-reactive protein (CRP) and Myeloperoxidase (MPO) that are biomarkers of cardiovascular diseases is demonstrated. The performance metrics of the device in response to the two biomarkers in pure form and in serum samples were evaluated and compared to standard ELISA assays. The methodology that has been adopted is based on measuring impedance and calibrating its change in magnitude with concentration of proteins. We demonstrate the following performance metrics: limits of detection up to 1 ng/ml for CRP and 500 pg/ml for MPO in pure and serum samples; linear dynamic range of detection from 10 ng/ml to 100 microg/ml for CRP and 1 ng/ml to 1 microg/ml for MPO and cross-reactivity contained at less than 10% of selective binding for both the inflammatory proteins. Iridium oxide has an ability to detect very small changes to the surface charge and this capability is utilized for achieving the performance metrics and forms the basis of the key innovations of this technology, which are, improving the selectivity and sensitivity of detection.

Silicon nanosensor for diagnosis of Cardiovascular proteomic markers

A silicon nanosensor technology based on electrical impedance measurements has been developed for the detection of proteins. The nanosensor miniaturizes the high-density, low-volume multiwell plate concept. The scientific core of this technology lies in integrating nanoporous membranes with microfabricated chip platforms. This results in the conversion of individual pores into nanowells of picoliter volume. Monoclonal antibodies were localized and isolated into individual wells. Detection of two cardiac proteomic biomarkers has been demonstrated with this technology. The two proteins, C-reactive protein and NT-pro–brain natriuretic peptide (BNP), are associated with adverse cardiac outcomes in clinical samples when detected in the pg/mL concentration. The formation of the antibody-antigen binding complex occurs in individual wells. The membrane allows for robust separation among individual wells. This technology has the capability to achieve near real-time detection with improved sensitivity at 1 ag/mL for BNP and 1 fg/mL for CRP from human serum.

Electrical Immunoassays toward Clinical Diagnostics: Identification of Vulnerable Cardiovascular Plaque

A technology for electrical detection of protein biomarkers has been developed. It is based on developing high-density, low-volume multiwell plate devices. The scientific core of this technology lies in integrating nanoporous membranes with microfabricated chip platforms. This results in the conversion of individual pores into wells of picoliter volume. Specific antibodies are localized and isolated into individual wells. The formation of the antibody–antigen-binding complex occurs in individual wells. The membrane allows for robust separation among individual wells. This technology has the capability to achieve near real-time detection with improved sensitivity and selectivity. This is due to the two factors associated with the technology: (1) event-based electrochemical detection process, where the individual step in the formation of the binding complex results in a specific change to the electrochemical conductance due to the pertubation of the electrical double layer at the base of the each well. (2) The nanoporous membrane is an electrical insulator and is structurally robust throughout hence there is improved signal-to-noise ratio and cross-contamination between is minimized. Another advantage of this technique is the use of electrical signal in protein identification as compared to the use of optical methods; hence, it is a noninvasive and a label-free technique. The signal acquisition is simple and it uses the existing data acquisition and signal analysis methods. We have demonstrated the use of this technology for addressing a specific clinical problem: identification of vulnerable coronary plaque in the perioperative state.

Nanomonitors: Nanomaterial Based Devices Towards Clinical Immunoassays

The immobilization of biomolecules on a solid substrate and their localization in “small” regions are major requirements for a variety of biomedical diagnostic applications, where rapid and accurate identification of multiple biomolecules is essential. In this specific application we have fabricated nanomitors for identifying specific protein biomarkers based on the electrical detection of antibody-antigen binding events. The nanomonitor, lab-on-a-chip device technology is based on electrical detection of protein biomarkers. It is based on developing high density, low volume multi-well plate devices. The scientific core of this technology lies in integrating nanomaterial with micro fabricated chip platforms and exploiting the improve surface area to volume to improve the detection. The devices that have been developed utilize electrical detection mechanisms where capacitance and conductance changes due to protein binding are used as “signatures” for biomarker profiling. In comparison to optical methods, the electrical detection technique is non-invasive as well as a label free. The signal acquisition is simple and it uses the existing data acquisition and signal analysis methods

A Comparative Analysis of Iridium Oxide Nanowires in Electrical Detection of Biochemical Reactions

Pt, Ir, Au and few other precious metals have highly conducive electrical and chemical properties; hence have been widely used in pH sensors and bimolecular sensing applications. The chief objective of this research is to highlight and demonstrate the advantages that Iridium Oxide (IrOx) nanowires offer over these competing metals in improving the performance metrics of biomolecular sensing. Iridium oxide has very good conductivity and very high charge storing capacity, and hence has an ability to detect very small changes in the surface charge. Nanowires have an ideal morphology to crowd protein molecules and highly increase the surface area of interaction. Higher area of interaction along with iridium oxides high intrinsic physical adsorption rate, strongly enhance the rate of immobilization of biomolecules and hence enabling high sensitivity detection. Inflammatory protein, C-Reactive protein (CRP) that is a biomarker for cardiovascular disease was used as the model biomolecule for this study.