Gold immunochromatographic strips for enhanced detection of Avian influenza and Newcastle disease viruses

• The technique enhances the detection sensitivity by inducing the clustering of gold particles on the nitrocellulose strip.
• The operating time is very short (about 15 min). Compared with commercial test strips, the method is 100-fold more sensitive.
• The method is simple, rapid, economic, sensitive, specific, and results in detection with the naked eye.
• The technique will be a powerful tool to carried out on-site because of its high sensitivity, specificity, and speed.

A new technique that uses gold immunochromatographic strips enhances the detection sensitivity by inducing the clustering of additional gold nanoparticles (AuNPs) around the immunogold particles immobilized on nitrocellulose strips. The additional AuNPs provide an intense signal that can be detected by the naked eye. The AuNPs were synthesized and conjugated to monoclonal antibodies using self-assembly. Other antibodies were immobilized in a defined detection zone on the nitrocellulose membrane. The detection principle is based on a “sandwich” immunoreaction, where gold-labeled antibodies serve as signal vehicles. To improve the sensitivity of the strips, we use a mixture of 1% HAuCl4 and 10 mmol L−1 NH2OH·HCl to “enlarge” the gold nanoparticles. The detecting limits of Avian influenza virus (AIV) and Newcastle disease virus (NDV) are significantly increased. Compared with commercial test strips, this method is 100-fold more sensitive. This method is easy to perform and can be carried out on-site in test laboratories.

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