Achieving biosensing at attomolar concentrations of cardiac troponin T in human biofluids by developing a label-free nanoplasmonic analytical assay

Abstract

Acute myocardial infarction (heart attack) is the fifth leading cause of death in the United States (Dariush et al. Circulation 2015, 131, e29-e322). This highlights the needs for early, rapid, and sensitive detection of its occurrence and severity through assaying cardiac biomarkers in human fluids. Herein we report chip-based fabrication of the first label-free, nanoplasmonic biosensor to assay cardiac Troponin T (cTnT) in human biofluids (plasma, serum, and urine) with high specificity. The sensing mechanism is based on the adsorption model that measures the localized surface plasmon resonance (LSPR) wavelength shift of anti-cTnT functionalized gold triangular nanoprisms (Au TNPs) induced by change of their local dielectric environment upon binding of cTnT. We demonstrate that controlled manipulation of sensing volume and decay length of Au TNPs together with the appropriate surface functionalization and immobilization of anti-cTnT onto TNPs allows us to achieve a limit of detection (LOD) of our cTnT assay at attomolar concentration (~15 aM) in human plasma. This LOD is at least 50 fold more sensitive than that of other label-free techniques. Furthermore, we demonstrate excellent sensitivity of our sensors in human serum and urine. Importantly, the strategy of our chip-based fabrication is extremely reproducible. We believe our powerful analytical tool for detection of cTnT directly in human biofluids using this highly reproducible, label-free LSPR sensor will have great potential for early diagnosis of heart attack and thus increase patients' survival rate.

Plasmonic triangular nanoprism sensors

“…6). 67,94 In this view, the observed LSPR shift is proportional to the change of refractive index (Dn) due to the analyte as well as how much the sensing volume V S is occupied by the analyte (V D ).…”

A Label-free Cardiac Troponin T Electrochemiluminescence Immunosensor Enhanced by Graphene Nanoplatelets

“…As stated in a report by Liyanage, Sangha and Sardar, the cTnT concentration perceived in patient with high risk of AMI is said to be >10 ng L -1 (≈ >10 pg mL -1 ). 32 The linear range of our developed immunosensor was included within the concentration range required for the detection of the unhealthy and healthy amounts of cTnT in human serum for the diagnosis and prediction of AMI. As for the limit of detection of cTnT, it was visually verified and it was observed to be 0.05 fg mL -1 .…”

Cardiac troponin biosensors: where are we now?

“…Researchers in the USA have developed a sensor that is sensitive to even attomolar concentrations of cardiac troponin in human biofluids (urine, blood, and serum). 45 This unique sensor exploits the property of localized surface plasmon resonance (LSPR) of triangular gold nanoprisms. This electroluminescence-based sensor detects the cTnT levels in the fluid as soon as binding of the detection analyte occurs.…”

“…Although this sensor displays a very high sensitivity to cTnT concentrations in symptomless or undiagnosed cases of myocardial infarction, it cannot quantify the cTnT concentration from single cell extracts. 45,46 Tadepalli et al report a similar example of an LSPR sensor, 47 which uses human troponin I binding peptide, immobilized on gold nanorods, as the detecting element. This sensor exploits the thiol group's affinity for gold.…”