ABSTRACT
The development of versatile platforms to construct novel and sensitive immunosensors is nowadays an intense research field. Nanomaterials and polymers are often combined to fabricate new platforms to immobilize capture antibodies. Here we evaluate for the first time the co-electropolymerization of dopamine (DA) and L-3,4-dihydroxyphenylalanine (L-DOPA) on carbon nano-onion (CNO) modified electrodes as versatile platform to develop electrochemical immunosensors. Mixtures of DA and L-DOPA at different molar rations were co-electropolymerized on CNO-modified glassy carbon electrodes to form a poly(L-DOPA/DA) film. Immobilization of aminoferrocene was used to estimate the number of accessible carboxylic acid groups on the surface (11.3â¯nmol/cm2), a value comparable to three-dimensional matrices. This platform was applied to the electrochemical detection of IgA antibodies using both a HRP-based sandwich type assay and label-free detection based on [Fe(CN)6]3-/4- signal blocking. The sandwich and the label-free assays showed a wide linear response with LOD of 19 and 48â¯ng/mL, respectively, allowing the detection of serum IgA deficiency. Most remarkably, the incorporation of CNO layer led to a significant improvement (three-orders of magnitude) of the analytical performance of these immunosensors due to a combination of high surface area and increased electron transfer rates provided by the CNO layer.
Subject(s)
Biosensing Techniques/methods , Carbon/chemistry , Dopamine/chemistry , Immunoglobulin A/blood , Levodopa/chemistry , Antibodies, Immobilized/chemistry , Electrodes , Humans , Immunoassay/methods , Limit of Detection , Models, Molecular , Nanostructures/chemistry , Polymerization , Polymers/chemistryABSTRACT
Here, we report for the first time, an electrochemical immunoassay to detect IgM antibodies using lead sulfide quantum dots (PbS QDs) as electrochemical labels. In this sense, dendritic-like polydopamine particles loaded with PbS QDs were synthesized by the self-polymerization of dopamine in basic media in the presence of QDs (PbS@PDA) and further tagged with anti-IgM antibodies, dengue specific antigens, and streptavidin moieties. The analytical features of the sandwich immunoassay on ELISA microplate were carried out with the PbS@PDA-labeled anti-IgM as secondary antibody. The system was interrogated by acid dissolution of PbS@PDA, followed by differential pulse anodic stripping voltammetry in the presence of Bi(III) ions using carbon screen-printed electrodes. The results indicate that the voltammetric current increased with the increasing of the concentration of target IgM within a range of 0-0.5â¯mgâ¯mL-1. The limit of detection of this electrochemical immunoassay was evaluated to 130â¯ng. The measures of satisfactory recoveries from 88.5% to 114% of spiked samples indicate that such a method has good specificity and is applicable to the quantification of IgM antibodies in complex biological samples. No significant differences at the 0.05 significance level were encountered in the analysis of IgM samples between the electrochemical immunoassay and a Bradford assay.
Subject(s)
Electrochemical Techniques/methods , Immunoassay/methods , Immunoglobulin M/analysis , Indoles/chemistry , Lead/chemistry , Polymers/chemistry , Quantum Dots/chemistry , Sulfides/chemistry , Antigens/chemistry , Antigens/immunology , Biosensing Techniques , Bismuth/chemistry , Carbon/chemistry , Electrodes , Humans , Immunoglobulin M/chemistry , Immunoglobulin M/immunology , Limit of Detection , Nanoparticles/chemistry , Serum/chemistry , Streptavidin/chemistryABSTRACT
Multiwalled carbon nanotubes modified with 2-aminoethanethiol (MWNT-AET) were vertically self-assembled on gold electrodes with the assistance of chitosan and Tween. According to AFM and cyclic voltammetric determinations the best results were achieved using chitosan.
