ABSTRACT
Surface Enhanced Raman Scattering (SERS) supported by gold nanoparticles (AuNPs) was applied to detect and quantify residues of pyrimethanil on pome fruits, a widely used fungicide in horticultural species. Spheroidal AuNPs with different size were fabricated and compared in this study. The analytical procedure was set up on a silicon dioxide flat substrate to standardize SERS methodology. A Raman mapping strategy was exploited to increase signal reproducibility and to minimize bias due to different local surface morphologies. Univariate and multivariate regressions were compared for calibration. Multivariate PLS approach demonstrated acceptable repeatability and method stability (RMSECVâ¯=â¯4.79â¯ppm; RMSEPâ¯=â¯4.31â¯ppm) in the range 0-40â¯mgâ¯kg-1, providing higher accuracy and intra-day repeatability with a mean percentage error of 18.7% and 32.8% for PLS and univariate calibration, respectively. The method here proposed can be reliably applied for PMT detection on pome fruits within the European law limits.
Subject(s)
Fruit/chemistry , Pyrimidines/analysis , Spectrum Analysis, Raman/methods , Calibration , Food Analysis/methods , Food Contamination/analysis , Fungicides, Industrial/analysis , Gold/chemistry , Malus/chemistry , Metal Nanoparticles/chemistry , Multivariate Analysis , Reproducibility of Results , Sensitivity and Specificity , Silicon Dioxide/chemistry , Spectrum Analysis, Raman/instrumentation , Spectrum Analysis, Raman/standardsABSTRACT
A porous silicon biosensor based on P450 enzyme for arachidonic acid detection was developed. A new transduction method is presented with a simultaneous measurement of refractive index and fluorescence intensity changes when the analyte is binding to an enzyme on the porous silicon surface. A fluorophore bound to a cysteine residue in an allosteric position of the haem domain (BMP) of cytochrome P450 BM3 enhances its fluorescence intensity upon interaction with its substrate arachidonic acid, involved in diseases such as Alzheimer's, liver cancer and cellular inflammation processes. BMP has been anchored on porous silicon surface and the new transduction method has been successfully exploited to develop a biosensor for arachidonic acid, reaching a detection limit of 10 µM arachidonic acid in a dynamic range of 10-200 µM. Moreover, the change of the refractive index has been also monitored at the same time, displaying a higher detection limit of 30 µM. Preliminary test were also conducted in plasma proving the high specificity and selectivity of the sensor even in presence of interferents in the range of 50-100 µM. Here we suggest these two detection systems could be used simultaneously to increase the accuracy and the dynamic range of the sensor avoiding a false positive response.
