Rapid and Sensitive Nano-Immunosensors for Botulinum

Abstract

Botulinum\nis a deadly bacterial toxin that causes neuroparalytic\ndisease. However, appropriate tools to detect trace toxic proteins\nare scarce. This study presents a bead-based diffusometric technique\nfor the rapid, simple, and quantitative detection of biological toxins.\nFunctionalized particles called nano-immunosensors were fabricated\nby forming sandwiched immunocomplexes comprising Au nanoparticles\n(AuNPs), toxic proteins, and antibodies on fluorescent probe particles.\nParticle diffusivity tended to decline with increasing concentration\nof the target proteins. Calibration curves of purified botulinum toxins\n(0.01–500 ng/mL) were obtained from whole milk and bovine serum,\nand results suggested that measurement was independent of the background\nmatrix. The activity of botulinum toxin was evaluated by coating synaptosomal-associated\nprotein 25 (SNAP-25) on fluorescent probe particles. AuNP-conjugated\nantibodies attached to the probe particles when SNAP-25 proteins were\ncleaved by active botulinum. Thus, toxicity could be detected from\nslight changes in diffusivity. A short measurement time of 2 min and\na limit of detection of 10 pg/mL were achieved. The nano-immunosensors\ndemonstrated rapid biosensing capability and met the demands of onsite\nscreening for food safety, medical instrument hygiene, and cosmetic\nsurgery products.