A mixed alkanethiol based immunosensor for surface plasmon field-enhanced fluorescence spectroscopy in serum

Abstract

This paper describes a simple and sensitive immuno-based biosensor for interference-reduced detection of C-reactive protein (CRP) in serum. The detection was performed by using a non-competitive sandwich immunoassay in combination with surface plasmon field-enhanced fluorescence spectroscopy (SPFS). CRP is an important marker for the diagnosis of inflammatory processes and cardiovascular diseases (CVD). It is nowadays detected by high-sensitivity enzyme-linked immunosorbent assays (ELISA) in blood serum. CRP was used as a model analyte in this work because it is well-characterized. However, interfering effects of matrix components affect the limit of detection (LOD) and quantification (LOQ) in general. Therefore, the availability of fast, sensitive and robust analytical methods is of major interest. A number of biosensor approaches have been described already, but only a few have demonstrated their usefulness in authentic samples such as serum. Thus our aim was to develop a simple and sensitive immunoassay-based biosensor for an interference-reduced detection of CRP in serum with surface plasmon enhanced fluorescence spectroscopy (SPFS). LODs and LOQs were experimentally determined both for CRP spiked buffer and serum. SPFS in combination with our biosensor allows sensitive analysis of CRP, achieving in buffer a LOD of 0.016 μg mL(-1) and a LOQ of 0.049 μg mL(-1). In serum the accomplished LOD was 0.026 μg mL(-1) and the LOQ was found to be 0.08 μg mL(-1). These low LODs and LOQs demonstrate the applicability of the designed biosensor for qualitative and semi-quantitative analysis of trace amounts of substances in very small sample volumes of body fluids.

Plasmon-Enhanced Fluorescence Biosensors: a Review

“…The limit of detection of f-PSA in PBS buffer and diluted female serum was 0.4 pg/ml (12 fM) and 1.8 pg/ml (52 fM), respectively, and the analysis required 2 h. Another cancer biomarker—C-reactive protein—was detected by SPFS with sandwich immunoassay. The limit of detection of 26 ng/ml (248 pM) in human serum diluted 1:20 was reported for 30 min of analysis time [ 112 ]. PEF detection of pancreatic cancer biomarker—UL16-binding protein 2—was implemented to microtiter plate arrays by using a sandwich immunoassay [ 113 ].…”

Detection of C-reactive protein using nanoparticle-enhanced surface plasmon resonance using an aptamer-antibody sandwich assay

“…6 The most commonly used CRP diagnostic methods are the antibody-based assays. [7][8][9] Currently, some aptamer-based methods have been developed for CRP detection, such as electrochemiluminescence, 10,11 fluorescence, 12,13 chemiluminescence, 14 surface plasmon resonance 15,16 and isotachophoresis. 17 Aptamers, which were obtained by using an in vitro process named systematic evolution of ligands by exponential enrichment (SELEX), [18][19][20] are potential candidates to replace antibodies in therapeutic diagnostics and drug development.…”

Parametric optimization of visible wavelength gold lattice geometries for improved plasmon-enhanced fluorescence spectroscopy

“…The centerpiece of plasmon-enhanced biosensing is to boost and control the spontaneous emission rate of fluorophore(s) utilized in the detection of specific pathogens (e.g., Aspergillus fumigatus, Burkholderia mallei, Burkholderia pseudomallei, cancer biomarkers, toxins, viruses, etc.) via the combination of fluorescent probes with noble metal nanostructures [158][159][160][161][162][163][164][165][166][167][168][169][170][171][172][173][174].…”

“…This plasmonic field is controllable via selective clustering, functionalization, and sizing of the gold NPs with a plethora of biomedical applications such as bio-imaging, environmental monitoring, genomics, and faster medical diagnoses [11,[158][159][160][161][162][163][164][165][166][167][168][169][170][171][172][173][174]. The obtainable fluorescence emission in the presence of these gold NPs can be up to hundreds of times greater than that in the absence of gold NPs and is directly related to an overlap between the plasmonic resonance of gold NPs and the fluorescence emission wavelength [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

“…The fundamental principle governing optical transduction involves taking energy from one form and transferring it into another, quantifying that energy change/input, and measuring the optical response [21,[120][121]. This methodology can be specifically tailored for plasmonic affinity biosensors incorporating infrared (IR) or ultraviolet (UV) electromagnetic (EM) energy with analyte-bioreceptor interactions [7,9,40,99,[156][157][158][159][160][161][162][163][164][165][166][167][168][169][170][171][172][173][174]. Optical transduction techniques either directly, or indirectly, probe analyte(s) of interest using a photodetector to quantify the optical response typically performed by comparing some optical characteristic of the reflected radiation from the sample to that of the source beam (e.g., amplitude, and/or phase information) [21,[23][24][25][26][27][28][29].…”