Chemical Strategy to Stepwise Amplification of Signals in Surface Plasmon Resonance Imaging Detection of Saccharides and Glycoconjugates

Abstract

A stepwise strategy was proposed to controllably amplify surface plasmon resonance imaging (SPRi) signals and used to establish a method for sensitive detection of small saccharides and large glycoconjugates. The key is to enlarge the target analytes step by step through a cyclic recognition reaction of concanavalin A (ConA) with dextran, which can easily be integrated into SPRi detection. The reaction is theoretically expected to proceed with infinite cycles by addition of ConA and dextran one after another, and in practice, it allows for performing signal amplification for up to 20 steps, which nearly reaches the limit of the propagation depth of surface plasmon waves. Because of the nonspecific adsorption effect, the maximum signals of small sugars were measured at steps 5-7 by the use of small molecules like ethanol amine to block the nonspecific adsorption. The real applicability of the method was validated by SPRi determination of either immobilized saccharides and glycoproteins or captured carcinoembryonic antigen (CEA) from patient samples with a limit of detection down to 2.5 μM glucose or 50 pg/mL of CEA. A wide extendibility of the method was confirmed by detecting other ConA-recognizable analytes like human IgG, ovalbumin, α-fetoprotein, and analytes convertible to ConA- or dextran-recognizable forms. Notably, other cyclic reactions specific to saccharides or other analytes are in theory exploitable, which will further widen the applicability of the method and strategy.

Gold Nanoparticles Used as Protein Scavengers Enhance Surface Plasmon Resonance Signal

“…Two sets of lectin-antibody were used to evaluate the methodologies: peanut agglutinin (PNA)-antibody anti-PNA and concanavalin A (ConA)-antibody anti-ConA. Due to the expanded range of applications of lectins in the life sciences, biosensors for lectins’ detection have been the focus of several research works [ 30 , 31 , 32 ]. The first method studied here was the covalent linking of PNA and ConA on gold NPs before the proteins were injected on the SPR system ( Figure 2 ).…”

Carbohydrate microarrays fabricated on poly(2-methylacrylic acid)-based substrates for analysis of carbohydrate–protein interactions

“…The carboxyl groups of the pMAA polymer on the glass substrates were then reacted with a frequently-used EDC/NHS reagent system to obtain an NHS-activated surface for subsequent immobilization of the amino-modified carbohydrates. 21,22 The commercially available amino-modified monosaccharides (a-Man, b-Glc, and b-Gal) were separately spotted on the pMAAmodified glass substrates with and without NHS activation to form carbohydrate microarrays. The obtained carbohydrate microarrays were then incubated with an a-mannose/a-glucose specific lectin, ConA-FITC.…”

Surface Plasmon Resonance: Material and Interface Design for Universal Accessibility

“…33 Advances in surface chemistries for ultrasensitive detection of nucleic acids and proteins were reviewed by Fasoli and Corn, with emphases placed on nucleic acid enzymes and nanoparticles for effective signal amplication. 34 Since these reviews were published, SPRi has been further applied toward the detection of ABH antigen, 35 matrix metalloproteinase-1, 36 and EGFR expression, 37 in addition to various cancer protein, 38 saccharide, 39 virus, 40 RNA, 41 and mRNA 42 targets. Newly developed printing protocols, including microwell 43 and trehalose-assisted 44 methods, have also been demonstrated for SPRi, which are certain to enhance both sample handling and characterization of target molecules that require stringent hosting environments.…”