We used 40 ± 5 nm gold nanoparticles (GNPs) as colorimetric sensor to visually detect swine-specific conserved sequence and nucleotide mismatch in PCR-amplified and non-amplified mitochondrial DNA mixtures to authenticate species. Colloidal GNPs changed color from pinkish-red to gray-purple in 2 mM PBS. Visually observed results were clearly reflected by the dramatic reduction of surface plasmon resonance peak at 530 nm and the appearance of new features in the 620-800 nm regions in their absorption spectra. The particles were stabilized against salt-induced aggregation upon the adsorption of single-stranded DNA. The PCR products, without any additional processing, were hybridized with a 17-base probe prior to exposure to GNPs. At a critical annealing temperature (55 °C) that differentiated matched and mismatched base pairing, the probe was hybridized to pig PCR product and dehybridized from the deer product. The dehybridized probe stuck to GNPs to prevent them from salt-induced aggregation and retained their characteristic red color. Hybridization of a 27-nucleotide probe to swine mitochondrial DNA identified them in pork-venison, pork-shad and venison-shad binary admixtures, eliminating the need of PCR amplification. Thus the assay was applied to authenticate species both in PCR-amplified and non-amplified heterogeneous biological samples. The results were determined visually and validated by absorption spectroscopy. The entire assay (hybridization plus visual detection) was performed in less than 10 min. The LOD (for genomic DNA) of the assay was 6 µg ml(-1) swine DNA in mixed meat samples. We believe the assay can be applied for species assignment in food analysis, mismatch detection in genetic screening and homology studies between closely related species.
Contamination of marine fish with the widespread distribution of anthropogenic particles (APs) becomes increasingly severe, however, related research on the assessment of the occurrence of APs in the edible tissue of commercial fish is scarce. The objective of this study was to evaluate the features of APs pollution based on seven species of commercial marine fish (n = 12 per species) and investigate the accumulation of APs in different tissues of fish namely gill and gastrointestinal tract (GIT), and muscle. The results show that a total of 62 APs were detected in 33 out of 84 (39.3%) fresh fish samples using a micro-Raman spectrometer which in particular is characterized by a blue color, shape-like fiber, and size smaller than 0.5 mm. Among them, 47 (75.8%) particles were identified as pigments such as indigo, chrome yellow-orange, disperse yellow, and pigment black. The other 11 (17.7%) particles were plastic including polypropylene (PP), polyethylene terephthalate (PET), and polyacrylonitrile (PAN). And the rest 4 (6.5%) particles were anthropogenic cellulose fibers. Muscle tissue from six species of fish was detected to contain a total of 15 APs. Based on the total mean of APs found in fish muscle (0.018 AP items/g tissue) and on the consumption of fish in Malaysia (59 kg/capita/year), the estimated human intake of APs through fish consumption was 1062 AP items/year/capita. Considering that food consumption is an important route of human exposure to APs, it is suggested to add APs testing into the guidelines of food safety management systems and adopt mitigation measures to reduce the APs pollution in food.