Anti-aquaporin-4 immunoglobulin G colorimetric detection by silver nanoparticles.

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory and autoimmune disease whose biomarker is the anti-AQP4-IgG autoantibody that binds to aquaporin-4 (AQP4) protein. We introduced a nanosensor with a sensitivity of 84.6%, higher than the CBA's 76.5%. Using silver nanoparticles (AgNPs), we detected not only seropositive but also some false-negative patients previously classified with CBA. It consisted of AgNPs coated with one of a panel of 5 AQP4 epitopes. The ability in detecting the anti-AQP4-IgG in NMOSD patients depended on the epitope and synergy could be obtained by combining different epitopes. We demonstrated that NMOSD patients could easily be distinguished from healthy subjects and patients with multiple sclerosis. Using the most sensitive AQP461-70 peptide, we established a calibration curve to estimate the concentration of anti-AQP4-IgG in seropositive NMOSD patients. The ability to enhance the accuracy of the diagnosis may improve the prognosis of 10-27% of anti-AQP4-IgG seronegative patients worldwide.

Layer-by-layer self-assembled chitosan/poly(thiophene-3-acetic acid) and organophosphorus hydrolase multilayers.

The aim of this study is to immobilize an enzyme, namely, organophosphorus hydrolase (OPH), and to detect the presence of paraoxon, which is an organophosphorus compound, using the layer-by-layer (LbL) deposition technique. To lift the OPH from the solid substrate, a pair of polyelectrolytes (positively charged chitosan (CS) and negatively charged poly(thiophene-3-acetic acid) (PTAA)) were combined. These species were made charged by altering the pH of the solutions. LbL involved alternate adsorption of the oppositely charged polyions from dilute aqueous solutions onto a hydrophilic quartz slide. This polyion cushion was held together by the electrostatic attraction between CS and PTAA. The growing process was monitored by fluorescence spectroscopy. OPH was then adsorbed onto the five-bilayer CS/PTAA system. This five-bilayer macromolecular structure compared to the solid substrate rendered stability to the enzyme by giving functional integrity in addition to the ability to react with paraoxon solutions. The ultimate goal is to use such a system to detect the presence of organophosphorus compounds with speed and sensitivity using the absorption and fluorescence detection methodologies.