“Turn-on” fluorescence sensing of cardiac troponin I based on MnO2 nanosheet quenched mercaptopropionic acid capped Mn2+ doped zinc sulphide quantum dots

[Display omitted] •A simple, sensitive and economically feasible fluorescence immunoassay for cTnI antigen was developed.•The immunosensor was based on MPA capped Mn2+ doped ZnS QDs and MnO2 nanosheets as the FRET couple.•The probe was able to detect cTnI antigen linearly from 0 to 2 ng/mL with a low LoD of 0.05 ng/mL.•The selectivity of the developed probe was assessed in the presence of other potential interferants and other cardiac biomarkers.•Good recovery percentage was obtained for cTnI detection from human serum samples. Acute Myocardial Infarction (AMI) is the persisting serious threat among all cardiovascular diseases due to its highest mortality rates. Clinicians resort to biomarker levels pertinent to AMI in triaging patients. Among the several cardiac biomarkers, by virtue of the specificity and sensitivity, cardiac troponin I (cTnI) was recognized as the gold standard for AMI diagnosis. Immunosensors that have been developed for cTnI detection are limited by multistep process and long diagnostic time which makes them unadaptable in primary healthcare centres. Recently, Fluorescence Resonance Energy Transfer (FRET) based immunosensors have found wide applicability in biomolecule detection. Among the evolving nanomaterials, Quantum dots (QDs) have been emerged as attractive donors in FRET based sensors for biomolecules. In the present work, we report a simple and sensitive fluorescence immunosensor for cTnI detection using Mercaptopropionic acid (MPA) capped Mn2+ doped ZnS QDs and MnO2 nanosheet as the FRET couple. For the specific detection of cTnI antigen, we have coupled cTnI antibody on the surface of MPA capped Mn2+ doped ZnS QDs. cTnI can be detected linearly with a low Limit of Detection (LoD) of 0.05 ng/mL. Furthermore, the selectivity of the developed probe has also been evaluated in the presence of other potential interferants and other cardiac biomarkers. In real serum samples, good recovery percentage was obtained proving that the probe is adaptable for Point of care detection of cTnI.