Thomas W. Barrett

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.

Novel Nanomonitor ultra-sensitive detection of troponin T

BACKGROUND Troponin is the preferred biomarker for diagnosing myocardial infarction. Point of care devices have not matched the sensitivity of laboratory-based methods for measuring troponin. The Nanomonitor is a novel point-of-care device that uses the change in electrical impedance that occurs when a biomarker binds to its antibody, which is then correlated to the concentration of the target biomarker. METHODS Performance characteristics of the Nanomonitor were evaluated and compared to a standard laboratory-based method. RESULTS The limit of detection of the Nanomonior for troponin T was 0.0088ng/l. Total imprecission was 2.38% and 0.85% at troponin T concentrations of 73ng/l and 1800ng/l. The functional sensitivity (10% coeffecient of variation) was 0.329ng/l. The linear regression had a slope of 0.996 (95% confidence interval, 0.991, 1.002), r=1.00, and an intercept of 15.88ng/l (95% confidence interval, -68.39ng/l, 100.15ng/l). The mean difference between the assays was -7.54ng/l, determined by Bland-Altman analysis. CONCLUSION The Nanomonitor preliminary results have favorable performance characteristics for detecting troponin T in patient blood, provide results in 15min, and are portable. More research is needed.

Portable nanoporous electrical biosensor for ultrasensitive detection of Troponin-T

Aim: To demonstrate the design, fabrication and testing of a portable, label-free biosensor for ultrasensitive detection of the cardiac Troponin-T (cTnT) from patient blood. Materials & methods: The biosensor is comprised of a nanoporous membrane integrated on to a microelectrode sensor platform for nanoconfinement effects. Charge perturbations due to antigen binding are recorded as impedance changes using electrochemical impedance spectroscopy. Results: The measured impedance change is used to quantitatively determine the cTnT concentration from the tested sample. We were successful in detecting and quantifying cardiac Troponin-T from a 40-patient cohort. The limit of detection was 0.01 pg/ml. Conclusion: This novel technology has promising preliminary results for rapid and sensitive detection of cTnT.

A nanomonitor compared to ELISA for C-reactive protein detection in patient blood

The nanomonitors are multi scale “point-of care” devices comprised of high density nanopores formed from the integration of nanoporous alumina membranes onto metallic microscale platforms. The nanomonitors have approximately 250,000 nanowells per sensing site and use antibody binding reactions for detection of proteins. The antigen explored was C-reactive protein (CRP), an inflammatory biomarker associated with cardiovascular disease. Protein detection on the nanomonitor was achieved through electrical impedance spectroscopy. We performed a prospective cohort study of patients undergoing vascular surgery and compared the nanomonitor results to the industry standard ELISA (enzyme-linked immuno-sorbant assay) for the measurement of CRP in patient blood using Bland-Altman and mixed effects model statistical techniques. No statistical difference was found between the nanomonitor, ELISA, and CRP results, p = 0.994. In addition, the mean inter-assay coefficient of variation (CV) for the nanomonitor was 1.3%, and mean intra-assay CV 1.8%. The mean inter-assay CV for ELISA was 6.1%, and mean intra-assay CV was 5.2%. The nanomonitor time-to-result was 15 minutes and the ELISA was 3 hours, a critical time saving for patient care. In conclusion, we validated the use of the nanomonitor in clinical patient blood samples for the detection of CRP.

Impact of combination medical therapy on mortality in vascular surgery patients.

BACKGROUND Th use of beta-blockers or statins has been associated with decreased mortality after noncardiac surgery. There are no prior perioperative studies of concurrent use of other cardioprotective drugs. OBJECTIVE To ascertain whether combinations of aspirin, beta-blockers, statins, and/or angiotensin-converting enzyme (ACE) inhibitors were associated with decreased mortality 6 months after vascular surgery. PATIENTS AND DESIGN We performed a retrospective cohort study on the 3020 patients who underwent vascular surgery between January 1998 and March 2005 at 5 regional Veterans Affairs (VA) medical centers. The Cochran-Mantel-Haenszel test was used to assess associations with 6-month all-cause mortality for the combination drug exposures compared to no exposure while adjusting for propensity score. RESULTS Exposure to all 4 of the study drugs compared to none had a propensity-adjusted relative risk (aRR) of 0.52 (95% confidence interval [CI], 0.26-1.01; P = 0.052), number needed to treat (NNT) 19; 3 drugs vs. none, aRR 0.60 (95% CI, 0.38-0.95; P = 0.030), NNT 38; 2 drugs vs. none, aRR 0.68 (95% CI, 0.46-0.99; P = 0.043), NNT 170; and 1 drug vs. none, aRR 0.88 (95% CI, 0.63-1.22; P = 0.445). ACE inhibitor exposure was common in all combinations. CONCLUSIONS Combination use of 2 to 3 study drugs, some of which included ACE inhibitors, was associated with decreased mortality after vascular surgery. Combination use of all 4 study drugs was not statistically significant due to the small number of events in this group. Further prospective studies of combination perioperative aspirin, beta-blockers, statins, and ACE inhibitors are warranted.

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