Fast on-Site Visual Detection of Active Ricin Using a Combination of Highly Efficient Dual-Recognition Affinity Magnetic Enrichment and a Specific Gold Nanoparticle Probe.

Ricin, a highly toxic protein, is a controlled substance by both the Chemical Weapons Convention (CWC) and the Biological Weapons Convention (BWC). Therefore, fast precaution of potential ricin toxin plays an important role in national security and public safety. Herein, a simple, sensitive, and accurate visual detection of active ricin in complex samples is presented by combining magnetic affinity enrichment with a specific gold nanoparticle (AuNP) probe. In the first step, a dual-recognition magnetic absorbent was fabricated by simultaneously incorporating two different affinity ligands (concanavalin A and galactosamine) on low-foul polymer brushes grafted magnetic beads, which showed remarkable multivalent synergy binding capacity for ricin even under complex interfering environments. Subsequently, a homoadenine-constituted oligodeoxynucleotide named poly(21dA) was conjugated to AuNPs (the poly(21dA)-AuNPs), which served as a specific depurination substrate of active ricin. Coralyne can trigger the intact poly(21dA)-AuNPs aggregate by forming a non-Watson-Crick homoadenine/coralyne complex, but the poly(21dA)-AuNPs after reacting with active ricin failed to form this complex due to the loss of adenines. Based on these facts, active ricin can be detected as low as 12.5 ng mL-1 with the naked eyes. This detection strategy could be well-applied in various ricin-spiked complex matrices. The features such as ready operation, facile readout, and easy accessibility make the assay a better choice for fast on-site active ricin detection.