Ultrasensitive on-site colorimetric detection of Campylobacter in oyster with a portable biosensing platform based on hydroxamate/Fe-violurate chromogenic reaction and smartphone.

The contamination of Campylobacter in shellfish poses a health risk for its pathogenicity associated with campylobacteriosis. However, an efficient method to detect this risk is unavailable. Herein, we introduce a portable colorimetric biosensing platform that comprises three modules: an enrichment module 1, a binding and transduction module 2, and a smartphone-based module 3. Module 1 is an aptamer-modified 96-well plate for the specific capture of Campylobacter in a simple and high-throughput manner. Module 2 features a bifunctional biopolymer of L-glutamic acid γ-hydroxamate-alginate-Fe coordinating fusarinine C, which can bind the captured Campylobacter cells and transduce them into amplified color signals upon reaction with Fe-violurate complexes. Module 1 achieves a capture efficiency of 97.24 %, and the subsequent addition of module 2 renders colorimetric indication of Campylobacter ranging from 10 to 10 CFU/mL, achieving an actual limit of detection of 8 CFU/mL validated by Campylobacter single-cells. Moreover, the generated colors can be recognized and converted into cell densities by module 3 with ultrasensitivity. Notably, this biosensor-smartphone platform accomplishe reliable high-throughput colorimetric detection of Campylobacter in real samples with an accuracy of 80 %. This work showcases a proof of principle for efficient on-site detection of Campylobacter contamination regarding shellfish farming.