Gold nanoparticles with helical surface structure transformed from chiral molecules for SERS-active substrates preparation

Helical au nanostructure for SERS detection of hazardous molecular and chiral enantiomers

In recent years, incidents of pesticide pollution and abuse of feed additives have occurred frequently, which pose a great threat to human health. Raman spectroscopy has become an important method in the field of food safety due to its rapidity, simplicity and sensitivity. It is important to obtain complex structure to promote surface-enhanced Raman scattering (SERS) effect. In this study, gold helical nanoparticles with rich surface structure were synthesized using cysteine as induce agent. Notably, the complex helical structure and tip led to an excellent electromagnetic enhancement property. The helical structure showed ultra-sensitive detection of hazardous molecular, such as thiram and ractopamine. Interestingly, the D/L-Au structure had significant chiral optical activity and could be used as an unlabeled SERS platform for enantiomer identification. This study provided an effective strategy for the detection of pesticides and feed additives, which could be applied in other aspects of food safety in the future.

Self-assembled C-Ag hybrid nanoparticle on nanoporous GaN enabled ultra-high enhancement factor SERS sensor for sensitive thiram detection

Considering pesticide residues cause significant harm to public health and the environment, developing a simple, sensitive, and reliable approach to pesticide residue detection to address this issue is necessary. In this study, an ultrasensitive and reliable surface-enhanced Raman scattering (SERS) sensor was developed using cetylpyridinium chloride as a protecting and reducing agent for the in situ synthesis and self-assembly of C-Ag nanoparticles on nanoporous GaN for the quantitative detection of thiram. A systematic investigation of the performance of the SERS sensor revealed that the SERS sensor delivered a limit of detection (LOD) of 10-14 M and an enhancement factor of up to 1.80 × 1011 with reasonable uniformity and reproducibility, with the stability of the SERS sensor demonstrated via long-term storage for up to 22 weeks in air. The enhancement mechanism of the SERS sensor was verified using a finite-difference time-domain simulation. The SERS sensor successfully detected thiram in real samples with an LOD of 10-10 M. Hence, this study provides an effective platform for monitoring food safety and the environment.

SERS-based pH-Dependent detection of sulfites in wine by hydrogel nanocomposites

Sulfur dioxide (SO2) and sulfites are well-known additives in winemaking due to their preservative properties. Although they can prevent oxidation and inhibit microbial growth, they pose health risks and require limitations on their use. Consequently, the total level of SO2 is regulated and several quantification strategies have been proposed. The approved detection methods require the extraction of SO2 by heating and/or acid treatment. Then, iodine or acid/base titrations are conducted for the detection of liberated SO2. Although these methods can provide sensitive detection of SO2, they are complex, time-consuming, and require sample preparation steps and skilled operators. Thus, to overcome these disadvantages, an easy-to-use method, involving simple sample preparation steps, and offering high sensitivity and selectivity, is desirable. Herein, we introduce a SERS-based strategy for SO2 detection in liquids using hydrogel nanocomposites. The hydrogels are prepared by poly(ethylene glycol) diacrylate (PEGDA) in the presence of gold nanoparticles (AuNPs), acting as the SERS substrate. The use of hydrogels ensures a homogenous signal distribution and an efficient collection of SO2, and drying the hydrogels enhances and stabilizes the obtained SO2 signal. The detection strategy is based on the pH-dependent dissociation of SO2. By adjusting the pH value of wine to 10 through simple dilutions, SO2 can be directly detected in wine, down to 0.4 ppm, well below the regulatory limits. The proposed method allows for sensitive, direct, cost-effective detection of SO2 by eliminating the loss of the gaseous form of the sample and avoids titration-based detection methods.

Fabrication of a Novel Au Star@AgAu Yolk-Shell Nanostructure for Ovarian Cancer Early Diagnosis and Targeted Therapy

Purpose

A novel CYPA-targeted, SiO₂ encapsulated Au star@AgAu yolk-shell nanostructure (YSNS) was synthesized and used for ovarian cancer early diagnosis and therapy.

Methods

Diverse spectroscopic and microscopic methods were utilized to investigate the pattern of the yolk-shell nanostructure. In addition, in vitro and in vivo experiments were carried out.

Results

It can be found that the ratio of HAuCl₄ and AgNO₃ played a critical role in the constitution of the yolk-shell nanostructure. The as-prepared yolk-shell nanostructure showed excellent SERS performance, which could be utilized as SERS substrate for specific sensitivity analysis of ovarian cancer markers cyclophilin A (CYPA) with detectable limit of 7.76*10^-10 μg/mL. In addition, the as-prepared yolk-shell nanostructure possessed outstanding photothermal performance, which could be used as photothermal agent for ovarian cancer therapy. Experiments in vitro and in vivo proved that the as-prepared yolk-shell nanostructures are ideal candidate for early diagnosis and therapy for ovarian cancer in one platform.

Conclusion

This work holds promise to offer a new method for the detection and therapy of ovarian cancer in the early stage.

A capillary-driven LoC-SERS device integrated with catalytic hairpin assembly amplification technology for NSCLC-related biomarkers detection

A capillary-driven LoC-SERS device is fabricated for the ultrasensitive detection of NSCLC-related protein biomarkers with catalytic hairpin assembly as the signal amplification strategy.