Wang Ying,Hou Yajun,Li Hanxia,Yang Mingfeng,Zhao Peng,Sun Baoliang
A surface-enhanced Raman scattering (SERS)-based lateral flow assay (LFA) is described for the quantitative analysis of the proteinic stroke biomarker S100-β that has to be detected at very low concentration levels. The Raman reporter 5,5′-dithiobis-2-nitrobenzoic acid (DTNB) on gold nanoparticles (GNPs) was employed as the SERS tags. They are shown to perform much better than bare GNPs in LF strips. The S100-β protein can be detected by this method with very low detection limits by monitoring the intensity of the characteristic Raman peak of the S100-β protein-conjugated GNPs at 1332 cm −1 . Under optimized conditions, the assay works in the 1 pg·mL −1 to 40 ng·mL −1 S100-β concentration range, and the detection limit is as low as 0.14 pg·mL −1 . This is lower by a factor of 3 compared to colorimetric or fluorimetric methods.
Schematic illustration of the configuration (A) and the principle of the SERS-based lateral flow assay for quantification of S100-β (B).
The development of rapid, highly sensitive detection methods for neuron-specific enolase (NSE) and S100-β protein is very important as the levels of NSE and S100-β protein in the blood are closely related to brain injury. Therefore, we can use NSE and S100-β protein concentration detection to realize the preliminary judgment of brain injury. In this paper, we report that a simple label-free three dimensional hierarchical plasmonic nano-architecture has been designed for the sensitive surface-enhanced Raman scattering immunosensor detection of NSE and S100-β. Owing to the active group of the hollow gold nanospheres (HAuNPs), the redox molecules 4-mercaptobenzoic acid (4-MBA) and Nile blue A (NBA) absorb antibodies and provide signal generation. The prepared HAuNPs@4-MBA and HAuNPs@NBA are used as probes to easily construct a surface-enhanced Raman scattering immunosensor. When protein biomarkers are present, the sandwich nanoparticles are captured over the substrate, forming a confined plasmonic field, leading to an enhanced electromagnetic field in intensity and in space. As a result, the Raman reporter molecules are exposed to a high density of “hot spots”, which remarkably amplify the Raman signal, improving the sensitivity of the surface-enhanced Raman scattering immunosensor. Under the optimized conditions, the linear range of the proposed immunosensor is from 0.2 to 22 ng mL−1 for both NSE and S100-β. The lowest detectable concentration is 0.1 and 0.06 ng mL−1 for NSE and S100-β, respectively. The assay results for serum samples with the proposed method were in a good agreement with the standard enzyme-linked immunosorbent assay method. The proposed immunosensor is promising in clinical diagnosis. This method, which utilizes the surface-enhanced Raman scattering of HAuNPs, has great potential in the detection of biomarkers, which are vital in medical diagnoses and disease monitoring.
Jingyi Sun,Yi Zhao,Yajun Hou,Hanxia Li,Mingfeng Yang,Ying Wang,Baoliang Sun
In this work, a real-time assay for a highly sensitive, label-free, multiplexed electrochemical and surface-enhanced Raman spectroscopic (SERS) detection of stroke biomarkers by neuron-specific enolase (NSE) and S100-β protein was developed using lateral flow devices. We found two kinds of Raman dye (Nile blue A (NBA) and 4-mercaptobenzoic acid (4-MBA))-decorated Au@AgNPs, which show both strong SERS signals and electrochemical redox characteristic peaks. The lateral flow assays are performed by a two-biomarker method for the first time. A sandwich structure contains the Raman dye-labeled Au@AgNPs with the first antibody, the second antibody immobilized on the lateral flow assay biosensor, and the target antigens. Thus, in the presence of the target antigens, the Raman dye-labeled Au@AgNPs could be bonded to the modified lateral flow device surface by antibody–antigen–antibody interactions. As a result, a simultaneous immunoassay for NSE and S100-β based on multiple labels is developed using electrochemical and SERS immunoassays. The prepared immunoassay biosensor for the detection of NSE and S100-β shows high sensitivity, selectivity, low detection limit and long-term stability. Compared with different Raman signals and electrochemical characteristic peaks, this has the lowest detectable concentration for NSE and S100-β at a signal to noise ratio of 3. The proposed immunosensor can be applied to determine NSE and S100-β in human blood serum. In addition, the electrochemical and SERS immunosensor has potential applications in the diagnosis and treatment of strokes in the field of clinical research.
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