Fabrication and verification of conjugated AuNP-antibody nanoprobe for sensitivity improvement in electrochemical biosensors

Abstract This study was designed to obtain covalently coupled conjugates as means for achieving higher stability and better coverage of the AuNPs by antibodies on the particle surface suitable for sensor performance enhancement. Starting by using a modified protocol, colloid gold solution, with mean AuNP core size of ~6 nm was synthesized. The protocol used for conjugation of AuNPs to osteocalcin antibody in this study relies on covalent and electrostatic attractions between constituents. Varieties of conjugates with varying combinations of crosslinkers and different concentrations were successfully synthesized. The obtained products were characterized and their properties were studied to determine the best candidate in sense of antibody - antigen reactivity. Using AuNP-GSH-NHS-Ab combination (1:1:1), the tertiary structure of the protein was maintained and thus the antibody remained functional in the future steps. This one-pot method provided a simple method for covalently coupling antibodies on the particle surface while keeping their functionality intact. The AuNP content of the solution also accelerated electron transfer rate and thus amplifies the detection signal. With the developed and discussed technique herein, a simple solution is modeled to be used for measuring serum levels of biomarkers in single and/or multiplexed sensor systems

Effects of oxatomide and derivatives on high affinity IgE receptor-activated signal transduction pathways in rat basophilic leukemia cells: Role of protein tyrosine hyperphosphorylation and inhibition of extracellular calcium influx

The antiallergic drug oxatomide and analogs inhibit mediator release from a rat basophilic leukemia (RBL-2H3) cell line, which is frequently used as a mast cell model. By investigating a series of derivatives of oxatomide with different inhibiting activities on exocytosis, we aimed to evaluate the role of their effects on the early steps of the signal transduction cascade in the inhibition of exocytosis. The active compounds induced hyperphosphorylation of tyrosine residues both in stimulated as well as in resting cells. Furthermore, some elevation of the inositol 1,4,5-trisphosphate (IP3) formation upon antigen activation was observed for the active derivatives. Ca2+ fluxes were also studied. The inhibition of the antigen-induced Ca-45(2+) influx correlated with the effects of the drugs on exocytosis. Furthermore, the inhibitory activity on antigen- and thapsigargin-mediated exocytosis correlated well. Adherence of the cells to fibronectin, stimulating cellular integrin receptors, was synergistic to antigen activation of the RBL cells. However, oxatomide did lack any effect on integrin-mediated processes, as the IC50 value for exocytosis was identical for fibronectin-adhered cells and standard cultured cells. We conclude that oxatomide and its analogs inhibit exocytosis, mainly by inhibiting Ca2+ influx over score operated Ca2+ (SOC) channels. The drugs have a direct effect on the store operated Ca2+ channels or affect the direct regulation of these channels. (C) 1998 Elsevier Science Inc