Ultrasensitive SERS immunoassay based on diatom biosilica for detection of interleukins in blood plasma

Analytical and Bioanalytical Chemistry, Aug 2017

An ultrasensitive surface-enhanced Raman scattering (SERS) immunoassay based on diatom biosilica with integrated gold nanoparticles (AuNPs) for the detection of interleukin 8 (IL-8) in blood plasma has been developed. The SERS sensing originates from unique features of the diatom frustules, which are capable of enhancing the localized surface-plasmon resonance of metal nanostructures. The SERS immune tags ware fabricated by functionalizing 70-nm Au nanoparticles with DTNB (i.e., 5,5′-dithiobis(2-nitrobenzoic acid)), which acted as a Raman reporter molecule, as well as the specific antibodies. These DTNB-labeled immune-AuNPs can form a sandwich structure with IL-8 antigens (infection marker) and the antibodies immobilized on the biosilica material. Our method showed an improved IL-8 detection limit in comparison to standard ELISA methods. The current detection limit for IL-8 using a conventional ELISA test is about 15.6 pg mL−1. The lower detection limit for IL-8 in blood plasma was estimated to be 6.2 pg mL−1. To the best of our knowledge, this is the first report on the recognition of IL-8 in human samples using a SERS-based method. This method clearly possesses high sensitivity to clinically relevant interleukin concentrations in body fluids. The average relative standard deviation of this method is less than 8%, which is sufficient for analytical analysis and comparable to those of classical ELISA methods. This SERS immunoassay also exhibits high biological specificity for the detection of IL-8 antigens. The established SERS immunoassay offers a valuable platform for the ultrasensitive and highly specific detection of immune biomarkers in a clinical setting for medical diagnostics. Graphical Abstract The SERS-based immunoassay based on naturally generated photonic biosilica for the detection of interleukin 8 (IL-8) in human plasma samples

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Ultrasensitive SERS immunoassay based on diatom biosilica for detection of interleukins in blood plasma

Ultrasensitive SERS immunoassay based on diatom biosilica for detection of interleukins in blood plasma Agnieszka Kamińska 0 1 2 Myroslav Sprynskyy 0 1 2 Katarzyna Winkler 0 1 2 Tomasz Szymborski 0 1 2 0 Department of Environmental Chemistry and Bioanalytics, Faculty of Chemistry, Nicolaus Copernicus University , 7 Gagarina Str, 87-100 Toruń , Poland 1 Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw , Poland 2 Agnieszka Kamińska An ultrasensitive surface-enhanced Raman scattering (SERS) immunoassay based on diatom biosilica with integrated gold nanoparticles (AuNPs) for the detection of interleukin 8 (IL-8) in blood plasma has been developed. The SERS sensing originates from unique features of the diatom frustules, which are capable of enhancing the localized surface-plasmon resonance of metal nanostructures. The SERS immune tags ware fabricated by functionalizing 70nm Au nanoparticles with DTNB (i.e., 5,5′-dithiobis(2nitrobenzoic acid)), which acted as a Raman reporter molecule, as well as the specific antibodies. These DTNB-labeled immune-AuNPs can form a sandwich structure with IL-8 antigens (infection marker) and the antibodies immobilized on the biosilica material. Our method showed an improved IL-8 detection limit in comparison to standard ELISA methods. The current detection limit for IL-8 using a conventional ELISA test is about 15.6 pg mL−1. The lower detection limit for IL-8 in blood plasma was estimated to be 6.2 pg mL−1. To the best of our knowledge, this is the first report on the recognition of IL-8 in human samples using a SERS-based method. This method clearly possesses high sensitivity to clinically relevant interleukin concentrations in body fluids. The average relative standard deviation of this method is less than 8%, which is sufficient for analytical analysis and comparable to those of classical ELISA methods. This SERS immunoassay also exhibits high biological specificity for the detection of IL-8 antigens. The established SERS immunoassay offers a valuable platform for the ultrasensitive and highly specific detection of immune biomarkers in a clinical setting for medical diagnostics. Surface-enhanced Raman spectroscopy (SERS); Interleukin 8; Diatom biosilica; Immunoassay Introduction Interleukins are secreted proteins that are members of the cytokine family of immune system molecules that regulate immune cell activity. Interleukins are produced by immune system cells such as lymphocytes, macrophages, and monocytes [ 1 ]. They modulate inflammation and immunity by regulating the growth, mobility, and differentiation of lymphoid and other cells [ 2 ]. The analysis and quantitation of interleukins in body fluids is important as it allows us to broaden our understanding of their immunological functions. Cytokine levels in body fluids can provide information useful for disease diagnosis and staging, prognostication, and thus the selection of an appropriate disease therapy [ 3 ]. Several analytical procedures for quantifying interleukins in body fluids and tissue culture supernatants have been developed. Enzyme-linked immunosorbent assays (ELISA) are the most popular methods of quantitating secreted cytokines due to their high specificities and sensitivities [ 4, 5 ]. Intracellular staining, the ribonuclease protection assay (RPA) [ 6 ], the polymerase chain reaction (PCR) [ 7 ], and cytometric assays [ 8 ] have also been used in recent decades. However, each of these techniques has at least one significant limitation. For instance, problems with cytokine assays, including a lack of accuracy, have been reported; a number of factors have been shown to affect the validity and quality of measurements obtained with such assays [ 9–12 ]. Therefore, there is a need to develop a more sensitive, selective, stable, and durable method for analyzing these biomarkers. Recent advances in nanotechnology and instrumentation development have permitted the development of a highly sensitive and chemically specific technique for biomolecular system recognition that uses surface-enhanced Raman spectroscopy (SERS) [ 13 ]. The phenomenon of SERS can be explained as a combination of an electromagnetic mechanism (EM) and a chemical mechanism related to charge transfer between a substrate and an adsorbed molecule [ 14 ]. Theoretically, the electromagnetic enhancement can reach factors of 103 to 1011, whilst chemical enhancement factors of up to 103 have been calculated [ 15, 16 ]. This huge enhancement in Raman scattering—even single molecules can be observed—ensures that Raman spectroscopy is very effective for ultrasensitive bioanalysis [17]. Another interesting characteristic of SERS is the linear dependence of the SERS intensity on the power of the incident light, despite the nonlinear signal enhancement that is achieved with this technique. Thus, SERS could potentially be applied for the quantitative measurement of analytes with ultrah (...truncated)


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Agnieszka Kamińska, Myroslav Sprynskyy, Katarzyna Winkler, Tomasz Szymborski. Ultrasensitive SERS immunoassay based on diatom biosilica for detection of interleukins in blood plasma, Analytical and Bioanalytical Chemistry, 2017, pp. 1-11, DOI: 10.1007/s00216-017-0566-5