Contamination of food by bacteria is very common and seafood, particularly bivalves, may be affected by several infectious diseases having a direct impact in human health. The transmission of pathogens among bivalves is direct and the areas of high production are often affected by faecal contamination. Thus, the accumulation of pathogenic bacteria in these filtering organisms may favor the increase of the bacterial contamination, bringing serious issues for consumer’s health. Colorimetric biosensing, based on color conversion for the detection of target analytes, emerged as a very promising possibility in biosensing development. In this field, the enzyme-like activity of some NPs has gained significant interest since the ability of these NPs to catalyze the oxidation of certain substrates, generating a color change, is a very promising route for colorimetric biosensors development.
In this work, a colorimetric nanosensor of silica-based coated superparamagnetic iron oxide nanoparticles (SPIONs) was developed.
SPIONs were synthesized through a co-precipitation method run in air at room temperature. The amino-silica coating was achieved following the Stöber protocol. Several types of nanostructures were developed, and the catalytic activity of the synthesized nanostructures was evaluated. Also, their performance as biosensors for bacteria detection was analyzed by testing different parameters through colorimetric in vitro assays.
The obtained preliminary results are promising. The catalytic activity of the NPs was verified by an increase on the color intensity observed at naked eye and confirmed through the measured absorbance values. When in presence of bacteria, a decrease on the color intensity also corroborated with the absorbance values, was observed. Thus, these preliminary results allow us to conclude that this colorimetric nano biosensor can be a valuable tool for a low-cost, easy and rapid monitoring of the presence of bacteria in bivalves.