Functionalized gold nanoparticle-enhanced competitive assay for sensitive small-molecule metabolite detection using surface plasmon resonance

Abstract

The development of sensing systems for the measurement of small molecules is an active area of research. A sensor based approach for the measurement of metabolites can potentially provide the simplicity and portability required for widespread use. Rapid detection and quantitation of small-molecule metabolites can potentially emerge as an effective way to link the metabolite profile to the disease state. Surface plasmon resonance (SPR) combined with molecular recognition elements to deliver high specificity is a sensing platform that has been widely applied for a large range of biomolecules. However, direct detection of small molecules with SPR challenges the refractive index based detection mechanism. The work described here combines a periplasmic binding protein for recognition with target modified gold nanoparticles (AuNPs) in a competitive assay format for folic acid (FA) detection. Specifically, a SPR imaging substrate containing immobilized folate binding protein (FBP) is used to measure the adsorption of FA conjugated AuNPs. The immobilization of the FBP and the binding of the FA conjugated AuNPs are characterized and optimized. It is shown that free FA in solution can be quantitatively measured by competition for the surface binding sites with the functionalized AuNPs. We demonstrate that the dynamic range can be lowered from micromolar to nanomolar by simply decreasing the concentration of FA conjugated AuNPs, thus lowering the limit of detection to 2.9 nM. This type of competitive assay can be applied to a range of small molecules, which paves the way for future multiplexed analysis of metabolites using SPR.

Recent Progress in Surface Plasmon Resonance Biosensors (2016 to Mid-2018)

“…The papers pertaining to stages (i) and (ii) represent incomplete analytical procedures. Technical solutions applied in these biosensors are shown in Table 1 [3,4,5,6,7,8,9,10,11,12,13]. These papers represent high innovative potential in terms of biosensor construction, which may result in fully developed procedures in the future.…”

Femtomolar and selective dopamine detection by a gold nanoparticle enhanced surface plasmon resonance aptasensor

“…For example, Corn et al reported the employment of nucleic acid functionalized nanoparticle-enhanced SPR imaging to measure protein and DNA targets down to the 25 fM based on oligonucleotide and aptamer microarrays [31]. We reported a small-molecule functionalized gold nanoparticle enhanced competitive assay to detect and quantitate folic acid in the nM range with a detection limit of 2.9 nM [32]. Zhou et al reported the use of gold nanoparticles-aptamer conjugates as a competitive reagent to detect adenosine down to 0.1 nM [33].…”

Correlation between composition and activity of gold nanoparticle conjugates with streptococcal protein G

“…Conjugates of gold nanoparticles (GNPs) with proteins are widely used in various fields of analytical chemistry and biochemistry [1][2][3]. In particular, GNP conjugates with immunoglobulin-binding proteins are commonly applied as detecting analytical reagents [4][5][6][7].…”