A polypyrrole-mediated photothermal biosensor with a temperature and pressure dual readout for the detection of protein biomarkers.

Photothermal biosensors with advantages of speed and high sensitivity offer alternative and reliable solutions for real-time clinical diagnosis, food safety testing and environmental monitoring. Although metallic nanoparticles are usually used for photothermal biosensors, their poor photothermal stability and potential toxicity hinder clinical applications. Taking advantage of the low cytotoxicity and remarkable photothermal effect under the low laser power of polypyrrole-based organic nanoparticles, we developed a novel photothermal biosensor with a temperature and pressure dual readout. After the formation of immunoassay sandwich structures, polypyrrole as the photothermal agent is synthesized in situ with pyrrole, HCl and Fe3+ released from magnetic Fe2O3 particles modified with detection antibody. The heterocyclic rings from polypyrrole enable photothermal performance in the NIR region. The resulting increased heat and pressure in a sealed well are measured using a digital thermometer and a portable pressure meter, respectively. Taking C-reactive protein (CRP) as a model target, the proposed strategy allowed sensitive, selective and accurate analysis of biomarkers, and showed performance comparable to that of ELISA. Overall, the dual-mode photothermal biosensor holds great potential for simple and low-cost photothermal sensing of biomarkers for point-of-care testing (POCT).

In situ Raman enhancement strategy for highly sensitive and quantitative lateral flow assay.

As a paper-based analytical platform, lateral flow assay (LFA) gets benefit from the rapid analysis, low cost, high selectivity, good stability, and user-friendliness, and thus has been widely used in rapid screening or assisted diagnosis. Nevertheless, LFA still suffers from low detection sensitivity via the naked eye, limiting its applications to qualitative and semi-quantitative tests. To enhance the signal readout, various nanoparticle signal tags have been employed to replace traditional colloidal gold nanoparticles (AuNPs), such as fluorescent nanoparticles (FNPs), magnetic nanoparticles (MNPs), and Raman reporter-labeled nanoparticles. In particular, Raman reporter-labeled nanoparticles are extremely sensitive due to remarkable signal enhancement effect on metal surface. However, the application of LFA is still hampered by the poor stability of Raman reporter-labeled nanoparticles. Herein, we developed an in situ Raman enhancement strategy to create a surface-enhanced Raman scattering (SERS) signal on the AuNPs, shortened as "i-SERS," which not only preserves the original advantages of the colloidal gold strip (AuNPs-LFA), but also realizes highly sensitive and quantitative detection. We applied the i-SERS for procalcitonin (PCT) detection. The experimental process takes only 16 min, and the limit of detection (LOD) is 0.03 ng mL-1, far below the value using AuNPs-LFA. These results indicate that i-SERS assay was highly sensitive and suitable for the rapid detection of PCT.

Investing in Food Safety for Developing Countries: Opportunities and Challenges in Applying Whole-Genome Sequencing for Food Safety Management.

Whole-genome sequencing (WGS) has become a significant tool in investigating foodborne disease outbreaks and some countries have incorporated WGS into national food control systems. However, WGS poses technical challenges that deter developing countries from incorporating it into their food safety management system. A rapid scoping review was conducted, followed by a focus group session, to understand the current situation regarding the use of WGS for foodborne disease surveillance and food monitoring at the global level and identify key limiting factors for developing countries in adopting WGS for their food control systems. The results showed that some developed nations routinely use WGS in their food surveillance systems resulting in more precise understanding of the causes of outbreaks. In developing nations, knowledge of WGS exists in the academic/research sectors; however, there is limited understanding at the government level regarding the usefulness of WGS for food safety regulatory activities. Thus, incorporation of WGS is extremely limited in most developing nations. While some countries lack the capacity to collect and analyze the data generated from WGS, the most significant technical gap in most developing countries is in data interpretation using bioinformatics. The gaps in knowledge and capacities between developed and developing nations regarding use of WGS likely introduce an inequality in international food trade, and thus, relevant international organizations, as well as the countries that are already proficient in the use of WGS, have significant roles in assisting developing nations to be able to fully benefit from the technology and its applications in food safety management.

Lateral flow assay with pressure meter readout for rapid point-of-care detection of disease-associated protein.

Paper-based assays such as lateral flow assays are good candidates for portable diagnostics owing to their user-friendly format and low cost. In terms of analytical detection, lateral flow assays usually require dedicated instruments to obtain quantitative results. Here we demonstrate a lateral flow assay with handheld pressure meter readout for the rapid detection of disease-related protein with high sensitivity and selectivity. Based on the pressure change produced by the catalytic reaction of Pt nanoparticles related to the concentration of the target, a quantitative reaction platform was established. During the lateral flow assay, the Pt nanoparticles are aggregated in the test line to form a gray band by biomolecular recognition and finally convert the recognition signal into highly sensitive pressure readout for quantitative analysis. Without sophisticated instrumentation and complicated operations, the whole detection process can be completed within 20 minutes. The limit of detection for myoglobin (2.9 ng mL-1 in diluted serum samples) meets the requirements of clinical monitoring. With the advantages of low cost, ease of operation, high sensitivity and selectivity, the method represents a versatile platform for point-of-care testing of disease biomarkers.

Effect of Addition of Allium hookeri on the Quality of Fermented Sausage with Meat from Sulfur Fed Pigs during Ripening.

The effect of the addition of Allium hookeri on the quality of fermented sausage made with meat from sulfur fed pigs was examined, throughout a 60 d ripening period. There were two treatments in animal management: normal feed fed pigs, and sulfur fed pigs given 0.3% sulfur mixed normal feed. Fermented sausage manufactured with meat from normal feed fed pigs, and with meat from sulfur fed pigs, and 1% A. hookeri-containing fermented sausage processed with meat from sulfur fed pigs, were determined at 1 d, 15 d, 30 d, and 60 d. The meat qualities in fermented sausage were measured by DPPH radical scavenging activity (DPPH), ABTS(+) radical scavenging activity (ABTS(+)), total phenolic acids, and total flavonoid contents. Fermented sausage made from pigs that had been fed with 0.3% sulfur was protected from oxidation by reduced free radical, as shown by the significant increase in DPPH and ABTS(+) values, compared with fermented sausage made from normal feed fed pigs (p<0.05). A. hookeri-added fermented sausage with sulfur fed pork was shown to increase the values in DPPH, ABTS(+), total phenolic acid, and total flavonoid contents, by comparison with both the control sausage, and sausage with sulfur fed pork, at 60 d. These results suggest that A. hookeri in meat from sulfur fed pigs could be a source of natural addition, to increase quality in the food industry.