Biotin [KLH]

In this study, we fabricated sensors to detect Alzheimer's disease (AD) biomarkers - amyloid beta (1-42) (A beta(1-)(42)) based on localized surface plasmon resonance (LSPR). The sensors were consisted of ligand-exchanged gold nanoparticles (Au NPs) deposited on polyethylene terephthalate substrate using Langmuir-Blodgett (LB) technique. Monoclonal antibodies (anti-A beta(1-)(42)) were then immobilized as a conjugate form with biotin onto the LB films of ligand-exchanged Au NPs by the aid of streptavidin. The attachment of the biomarkers to the antibodies immobilized on the LB films was detected by measuring absorbance change of plasmonic response peak. The sensor structure was optimized by comparing the results for the Au NPs LB films with different size and film thickness. The optimized sensor was used to detect biomarker at different concentrations in the buffer solution and a diluted cerebrospinal fluid (CSF) solution. As results, the sensor was able to detect even a trace amount of A beta(1-)(42) as small as 1 pg/ml from the CSF. This prototype sensor has a great potential because it shows several advantages of facile and inexpensive fabrication, and early detection of the AD. (C) 2020 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

There is a growing need for cancerous exosome detection towards potential non-invasive cancer diagnosis. This study aims to develop a reliable colorimetric aptasensor for sensitive and specific detection of circulating cancer-derived exosomes. In this design, target exosomes were firstly captured by latex beads via aldimine condensation, followed by bio-recognition using a specific CD63 aptamer, which was conjugated to horseradish peroxidase (HRP) through biotin-streptavidin binding. Colorimetric detection was achieved in 10 min via enzymatic catalysis to produce dark coloured polydopamine (PDA) from colourless substrate dopamine (DA) in especially prepared H2O2 reaction solution. The sensitivity was enhanced by in situ deposition of PDA around exosome particles to strengthen the developed colorimetric signal, which could be directly observed by naked eye. Signal quantification was carried out by absorbance measurement. The colour intensity correlates to the CD63 amount and the limit of detection can be as low as 7.7 x 10(3) particle/mL, improved by 3-5 orders of magnitude from conventional Dot-blot methods. The aptasensor showed specificity to HER2 and integrin avp6 positive, cell culture-derived, breast and pancreatic cancer-derived exosomes, respectively, when the correct aptamer sequence was used. Overall, a sensitive and selective colorimetric aptasensor was successfully developed for detecting cancer-derived exosomes facilitated by HRP-accelerated DA polymerization and in situ PDA deposition. This versatile aptasensor holds great potential for future development of point-of-care detection kits for cancer diagnosis in a clinical setting.