Immunomagnetic-Surface Enhanced Raman Spectroscopy For The Detection Of CTnⅠ

cTnⅠ is widely known as a biomarker for early diagnosis of acute myocardial infarction(AMI).Surface enhanced Raman spectroscopy(SERS)is a highly sensitive spectroscopic analysis technique that provides molecular-level information for the indepth characterization of surface structures and processes,and opens up new situations for biomedical applications.In this work,we proposed two ultra-sensitive Raman immunosensors for the detection of cTnI.In the first approach,chitosan encapsulated silver nanoparticles was labeled with Raman active molecule 5,5’-dithiobis(2-nitrobenzoic acid)(DTNB)and target molecule cTnI to construct labeled immune silver sol.Based on the competitive binding for the cTnI antibody-modified magnetic beads between the labeled immune silver sol and the free cTnI,a highly sensitive determination method for cTnI can be obtained,by quantifying the SERS signal in the supernatant.Under optimal conditions,with the irradiation of 638 nm laser,the Raman intensity at 1339 cm-1 was proportional with the concentration of cTnI.A detection limit of 40 pg mL-1(3σ,n=9)can be achieved,along with a precision of 4.79%(n=7,1 ng mL-1),and a linear range of 0.1-50 ng mL-1.The enhancement factor for silver sol was calculated to be 2.30×104.In the second approach,we proposed an ultrasensitive aptamer-antibody sandwich type Raman immunosensor for the detection of cTnI.In the nanosensor,DTNB and aptamer co-modified AuNPs was used as SERS probe,antibody-modified magnetic beads was used as capture substrate,and AuNPs-loaded filter paper was used as a solid-phase Raman-enhanced substrate.Under optimal conditions,with the irradiation of 785 nm laser,the Raman signalat 1331 cm-1 was proportional to the concentration of cTnI in the range from 0.050 ng mL-1 to 100 ng mL-1.A LOD of 15 pg mL-1(3σ,n=9)was achieved along with a precision of 6.38%(n=7,1 ng mL-1)and a enhancement factor of 1.39×106.Both methods can be applied for the recovery analysis for cTnI in serum samples,indicating their practical usefulness.