Development of cobalt oxyhydroxide-aptamer-based upconversion sensing nano-system for the rapid detection of Staphylococcus aureus.

Staphylococcus aureus (S. aureus) is a common pathogen that is dangerous to humans' health. Herein, a novel upconversion fluorescent biosensor based on fluorescence resonance energy transfer from aptamer-labeled upconversion nanoparticles (UCNPs-apt) as donor and cobalt oxyhydroxide (CoOOH) nanosheets as acceptor was designed to detect S. aureus in complex matrices. The principle of the work relies on fluorescence resonance energy transfer as UCNPs-apt can self-assemble on CoOOH nanosheet surfaces by van der Waals forces to effectively quench the fluorescence. When S. aureus was added, the aptamer was able to preferentially capture the target, resulting in the dissociation of donor and acceptor and the recovery of fluorescence. The structure and morphology of the nanostructures were assigned in detail by a series of characterizations, and the energy transfer mechanism was evaluated by time-resolved lifetime measurements. Under the optimal conditions, a linear calibration plot was obtained in a concentration range of 45-4.5 × 106 CFU/mL with a limit of detection of 15 CFU/mL. In addition, the proposed biosensor was used for S. aureus detection in real samples (e.g., pork, beef), and the detection result showed no significant difference (p > 0.05) compared with the conventional plate count approach. Hence, the fabricated biosensor holds a potential application for S. aureus in food analysis and public health.

Upconversion Nanoprobes Based on a Horseradish Peroxidase-Regulated Dual-Mode Strategy for the Ultrasensitive Detection of Staphylococcus aureus in Meat.

Staphylococcus aureus (S. aureus) is one of the foodborne pathogens that can cause infectious diseases and food poisoning. Herein, colorimetric and fluorescent dual-mode nanoprobes were developed for ultrasensitive detection of S. aureus to immediately respond to public health emergencies, reduce false positives, and improve measurement accuracy and persuasiveness. The nanoprobe consists of aptamer-labeled magnetic nanoparticles (apt-MNPs) as the capture signal probe and horseradish peroxidase and complementary DNA-functionalized upconversion nanoparticles (HRP-UCNPs-cDNA) as the chromogenic signal probe. In the absence of S. aureus, the probe forms an immune complex through base complementation with an observable signal. When S. aureus is introduced to this system, it preferentially binds to the apt-MNPs, releasing HRP-UCNPs-cDNA from the apt-MNPs and restoring the chromogenic probe signal. Under optimum conditions, an ultrasensitive assay of S. aureus was obtained, with limits of detection of 22 CFU mL-1 for fluorescence and 20 CFU mL-1 for colorimetry in a linear range of 56-5.6 × 106 CFU mL-1. Additionally, the standard plate counting method confirmed the reliability and accuracy of the established nanoprobe with an insignificant difference. Hence, the developed dual-mode platform has extensive application prospects for speedy and specific determination of S. aureus in meat.

Upconversion nanoparticles-based FRET system for sensitive detection of Staphylococcus aureus.

Staphylococcus aureus (S. aureus) is a pathogenic bacterium that seriously endangers food safety. Herein, a rapid, sensitive and specific aptasensor based on upconversion fluorescence resonance energy transfer (FRET) was developed for S. aureus detection in food. Aptamer-functionalized gold nanoparticles (AuNPs-aptamers) were bonded to cDNA-modified upconversion nanoparticles (UCNPs-cDNA) by complementary pairing, resulting in fluorescence quenching. After adding S. aureus into the system, the aptamers preferentially combined with S. aureus, dissociated UCNPs-cDNA from AuNPs-aptamers, and the fluorescence was recovered. Under optimized conditions, there was a significant linear correlation between fluorescence intensity and S. aureus concentration over the range 47-4.7 × 107 CFU/mL (R2 = 0.9904) with a detection limit of 10.7 CFU/mL. Furthermore, the precision and accuracy of the developed biosensor were validated using standard plate count method, yielding no significant differences. The proposed method has potential application for rapid and sensitive quantification of S. aureus in food.

[Comparative analysis of deterioration products in bio-waste oil and vegetable oils].

OBJECTIVE: To analyze the difference of deterioration products in bio-waste oil and vegetable oils. METHODS: The changes of species and abundance of deterioration products were analyzed through observing the differences in Raman spectra during the process of deterioration and refining. RESULTS: The deterioration contents produced during heating, cooking, frying and wasting, instead of storage, were significantly more abundant than normal contents. Through the refining process, the deterioration products abundance was reduced in vegetable oils while increased in bio-waste oils. CONCLUSION: Due to the distinct deteriorating processes, the species and abundance of deterioration products are remarkably different in bio-waste oil and vegetable oils. The deterioration products in vegetable oils would be mostly removed, but those in bio-waste oils are concentrated instead of eliminated during the refining procedure.

An approach to evaluate the reliability of hybridization-based and sequencing-based gene expression profiling technologies.

Hybridization-based and sequencing-based technologies have found a widespread application in gene expression profiling analysis but much ambiguity exists regarding their reliability. This study developed a framework based on three parameters: detection ability, repeatability, and accuracy to evaluate the reliability of gene expression profiling technologies. The fraction of coverage of detected transcript category, the degree of variance for the number of differentially expressed genes (DEGs), the consistency of DEG category, and suspected false discovery rate (sFDR) were first introduced as statistical indices. In order to validate the availability of these indices, based on the same RNA extract, the analysis was performed by comparing gene expression differences between wild-type and transgenic rice using deep sequencing and microarray. The results suggested that the parameters were available and showed advances in the determination of gene expression differences. Based on relative self-comparison design, suspected false positive genes were easily identified from all DEGs detected, which was difficult for quantitative real-time polymerase chain reaction (qRT-PCR) validation when the count of DEGs was enormous. In addition, sFDRs had advantages in the accuracy evaluation for previous datasets.

Edible safety requirements and assessment standards for agricultural genetically modified organisms.

This paper describes the background, principles, concepts and methods of framing the technical regulation for edible safety requirement and assessment of agricultural genetically modified organisms (agri-GMOs) for Shenzhen Special Economic Zone in the People's Republic of China. It provides a set of systematic criteria for edible safety requirements and the assessment process for agri-GMOs. First, focusing on the degree of risk and impact of different agri-GMOs, we developed hazard grades for toxicity, allergenicity, anti-nutrition effects, and unintended effects and standards for the impact type of genetic manipulation. Second, for assessing edible safety, we developed indexes and standards for different hazard grades of recipient organisms, for the influence of types of genetic manipulation and hazard grades of agri-GMOs. To evaluate the applicability of these criteria and their congruency with other safety assessment systems for GMOs applied by related organizations all over the world, we selected some agri-GMOs (soybean, maize, potato, capsicum and yeast) as cases to put through our new assessment system, and compared our results with the previous assessments. It turned out that the result of each of the cases was congruent with the original assessment.