a novel colorimetric detection of s. typhimurium based on fe3o4 magnetic nanoparticles and gold nanoparticles

Salmonella typhimurium is one of the most common causes of food-associated disease. a colorimetric nanosensor was developed to detect s. typhimurium which was based on the gold nanoparticles’ (gnps) color change effect. fe3o4 magnetic nanoparticles (mnps) and gnps were synthesized separately. two complementary sequences of the s. typhimurium target dna were combined to fe3o4 mnps and gnps to fabricate capture probes and signal probes. fe3o4 mnps could achieve the rapid separation and enrichment of target dna. with the addition of s. typhimurium target dna sequences, the sandwich-like structures were formed via the dna hybridization recognition effect. the original good dispersion of gnps was broken. gnps showed different degrees of aggregation with different amount of s. typhimurium target dna. the color changed from red, purple to blue which could be characterized by uv-vis spectrophotometer. the absorbance spectra of gnps red shifted constantly with the intensity ratio of a700/a521 changed regularly. there was a linear correlation between the ratio of a700/a521 and the amount of s. typhimurium target dna. thus, this was calculated for the basis of quantitative detection of s. typhimurium. this method is simple and rapid with high sensitivity and specificity which could be used to detect actual samples.