Search

Salmonella is a type of serious foodborne pathogenic bacterium that threatens the food safety worldwide. In this study, a fluorescence probe-based recombinase polymerase amplification analytical method (exo RPA) was developed for the sensitive and specific detection of Salmonella enterica (S. enterica). The primers and probe for this method were designed based on the iroB gene of the bacterium. The exo RPA reaction could detect as low as 102 copies of template DNA per reaction or 2.2 × 103 CFU/mL of S. enterica, and SPSS probit regression analysis indicated the limit of detection (LOD) at 95% probability of the exo RPA assay was 2.0 × 103 CFU/mL. Moreover, the exo RPA assay could successfully differentiate S. enterica from all the tested non-Salmonella strains. Importantly, this method is highly reliable; the DNA from other bacteria or food complex matrices has no obvious effect on the S. enterica exo RPA. Besides, positive signal could be obtained from the chicken or egg sample inoculated with 2.2 × 101 CFU/mL of S. enterica after 4- to 6-h enrichment at 36 °C. Therefore, this study describes a rapid test method for S. enterica, which is expected to be beneficial for monitoring trace S. enterica in real food products.

Triamcinolone acetonide (TCA) abuse in cosmetics is a common phenomenon. A rapid lateral flow immunochromatographic assay (ICA) was developed for the quantitative detection of TCA using a probe based on upconversion luminescence nanoparticles. Lanthanide-doped upconversion nanoparticles (UCNPs) were synthesized in a system comprising water and ethylene glycol, and a silicon dioxide layer was covered at the carboxyl site. A binding site protection strategy was used to decrease the background signal of UCNPs-ICA. Using dexamethasone derivative as a coating antigen, the optimal UCNPs–ICA exhibits good dynamic linear detection for TCA in the range 1.0–100 ng mL−1 with a median inhibitory concentration of 9.8 ng mL−1. The detection limits for TCA in a cosmetic sample are 20 μg kg−1. The pretreatment of samples only needs dilution with water, suggesting the assay can quantitate TCA on-site using a portable upconversion luminescence reader with a cumulative analysis time of only 10 min.

Dexamethasone has been illegally used as a growth-promoting agent to obtain an economic benefit from increased muscle development. An immunochromatographic assay was developed for the quantitative detection of dexamethasone using a probe based on upconversion luminescence nanoparticles. Lanthanide-doped upconversion nanoparticles were synthesized in a system comprising water and ethylene glycol. Various parameters, including the immunoreaction time, the structure of the coating hapten, and the type and concentration of surfactant, were optimized. Based on the optimal conditions, the assay exhibits good dynamic linear detection in the range of 0.05–5 ng/mL with an IC50 of 0.58 ng/mL. The detection limits for dexamethasone in tissue are 0.3 μg/kg. The assay worked well using a 30% methanol extraction solution, giving an average recovery of 84.5%. The assay strip can quantitate on-site using a portable upconversion luminescence reader with a cumulative analysis time of only 10 min, and its fluorescence decay after 6 months is < 25%.

Affine equivalent classes of Boolean functions have many applications in modern cryptography and circuit design. Previous publications have shown that affine equivalence on the entire space of Boolean functions can be computed up to 10 variables, but not on the quotient Boolean function space modulo functions of different degrees. Computing the number of equivalent classes of cosets of Reed-Muller code $\mathcal{R}(1,n)$ is equivalent to classifying Boolean functions modulo linear functions, which can be computed only when $n\leq 7$. Based on the linear representation of the affine group $\mathcal{AGL}(n,2)$ on $\mathcal{R}(s,n)/\mathcal{R}(k,n)$, we obtain a useful counting formula to compute the number of equivalent classes. Instead of computing the conjugate classes and representatives directly in $\mathcal{AGL}(n,2)$, we reduce the computation complexity by introducing an isomorphic permutation group $P_n$ and performing the computation in $P_n$. With the proposed algorithm, the number of equivalent classes of cosets of $R(1,n)$ can be computed up to 10 variables. Furthermore, the number of equivalent classes on $\mathcal{R}(s,n)/\mathcal{R}(k,n)$ can also be computed when $-1\leq k< s\leq n\leq 10$, which is a major improvement and advancement comparing to previous methods., 9 pages, 10 tables, 1 figure

Rhodamine B was forbidden in food by law because of its carcinogenic properties to humans. However, due to its low cost, it was often used to dope chili oil by some counterfeiters to improve its natural color. However, it was difficult to quantify rhodamine B in chili oil due to its complex substrates and high viscosity. In this study, deep eutectic solvents, comprised of choline chloride and ethylene glycol, were first used as an extraction medium to separate rhodamine B from chili oil.