Fabrication and implementation of a biosensor for health evaluation in raw milk

The use of veterinary drugs, including antibiotics, leads to their aggregation in livestock products such as meat, milk, and eggs. Therefore, rapid, accurate and economy detection of antibiotics for monitoring of food security is necessary. In the current research, a biosensor based on pencil graphite electrode modified with grapheme and gold nanoparticles for detection of β-lactam antibiotic in milk samples was fabricated. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques for evaluation of surface electrode changes were applied. Under optimal conditions, using the EIS method specified that in the ranges of 1×10-15 to 1×10-5 M, The relationship between charge transfer resistance and the logarithm of antibiotic concentration was linear and the regression equation was y=119x+2600 (R²=0.977). The current peaks in three measures were achieved as 18, 19.5 and 19 µA. calculation of relative standard deviation (RSD=3.31%) that indicated an acceptable repeatability for biosensor. For investigating of reproducibility, RDS for current peaks was 8.94% that showed a good reproducibility for biosensor. The selectivity of a biosensor in the presence of three antibiotics including streptomycin, tetracycline, and sulfadiazine was checked. Data of charge transfer resistance was indicated that biosensor has non-significant the response towards the other antibiotics. The results showed that biosensor response decreased by 6% after 18 days compared with the first day, which indicates good stability for biosensor. The percentage recovery range for milk samples at concentrations of 1 × 10-9 and 1× 10-11 M for two samples of cow and sheep milk was obtained as 92.3 to 104% in three replications, which indicates an acceptable recovery range for proposed biosensor.