Real-time monitoring of aristolochic acid I reduction process using surface-enhanced Raman Spectroscopy with DFT simulation

Reversible polarity-switch of thin-layer chromatography by photo-induction with multi-regulation in spatial dimension

Generally, thin-layer chromatography always undertakes the indispensable role in rapid screening and identification of specific compounds. Stationary phase is the core part of thin-layer chromatography with fixed property, which leading to the limitations of separation mode of only regulating the composition of mobile phase. This work was an attempt to fabricate the unique photosensitive thin-layer chromatography to make up the above major drawback. 4-[3-(Triethoxysilyl)propoxy]azobenzene (azo-PTES) was synthesized as photosensitive modifier to fabricate the photosensitive stationary phase, and the transformation of cis-trans structure of azo-PTES proceeds along with polarity difference under 365 nm and 473 nm irradiation. Based on this, the proposed photosensitive thin-layer chromatography shows the reversible switch of polarity of stationary phase by photoinduction, followed by the deserved reversible separation behavior. Furthermore, multi-regulation in spatial dimension was achieved based on the high freedom of spatial regulation of photoinduction, which brings about the integration of stationary phase with different polarity, just by photoinduction. The concept of photosensitive thin-layer chromatography provides new idea for improving separation efficiency and developing multi-dimensional thin-layer chromatography on the one plate.

Development and Application of a Comprehensive Nontargeted Screening Strategy for Aristolochic Acid Analogues

Aristolochic acid analogs (AAAs) are naturally occurring carcinogenic and toxic compounds that pose a safety threat to pharmaceuticals and the environment. It is challenging to screen AAAs due to their lack of characteristic mass spectral fragmentation and their presence of structural diversity. A comprehensive nontargeted screening strategy was proposed by taking into account diverse factors and incorporating various self-developed techniques, and a Python3-based toolkit called AAAs_finder was developed for its implementation. The main procedures consist of virtual structure and ultraviolet and visible (UV) spectra database creation, exact mass and UV spectra-based suspect data extraction, tandem mass spectra (MS/MS) anthropomorphic interpretation, and multicondition retention time (RT) prediction-based candidate structures ranking. To initially assess screening feasibility, eight hypothetical unknown samples were subjected to nontargeted screening using the AAAs_finder toolkit and two other advanced tools. The results showed that the former successfully identified all, while the latter two only managed to identify two and three, respectively, indicating that our strategy was more feasible. After that, the strategy was carefully evaluated for false positives and false negatives, instrument dependence, reproducibility, and sensitivity. After the evaluation, the strategy was successfully applied to the screening of AAAs in real samples, such as herbal medicine, spiked soil, and water. Overall, this study proposed a nontargeted screening strategy and toolkit independent of characteristic mass spectral fragmentation and able to overcome challenges posed by structural diversity for the AAAs screening, which is also valuable for other classes of compounds.

Rapid and robust analysis of aristolochic acid I in Chinese medicinal herbal preparations by surface-enhanced Raman spectroscopy

The use of Chinese herbs containing aristolochic acid can induce the exchange of adenine and thymine in gene mutations and even cause liver cancer. To eliminate the harm of aristolochic acids (AAs) to humans, a rapid and robust method of AAs screening is a prerequisite. In this work, a facile and robust Surface-enhanced Raman spectroscopy (SERS) method was used for the qualitative and quantitative detection of AAs in Chinese medicinal herbal preparations based on the mandelic acid modified Ag nanoparticles SERS substrate. Qualitative and quantitative SERS detection of Aristolochic acid I (AAI) was achieved with a good linear relationship ranging from 0.2 - 120.0 μM and a limit of detection (LOD) of 0.06 μM. The proposed method demonstrates a refined strategy for sensitivity analysis of AAs with the advantages of easy operation, time-saving, high sensitivity, and molecular specificity, making it a preferred platform for the screening of AAI in regular inspections of herbal products and regulatory supervision of the supply chain.

Multifunctional Au nano-bridged nanogap probes as ICP-MS/SERS dual-signal tags and signal amplifiers for bacteria discriminating, quantitative detecting and photothermal bactericidal activity

Ultra-sensitive detection of pathogenic bacteria is of great significance in the early stage of bacterial infections and treatment. In this work, we report a novel strategy using multifunctional Au nano-bridged nanogap nanoparticles (Au NNPs)-based sandwich nanocomposites, that made of Concanavalin A-conjugated Fe₃O₄@SiO₂ NPs (ConA-Fe₃O₄@SiO₂ NPs)/bacteria/aptamer-modified Au NNPs (apt-Au NNPs), for bacteria discrimination and quantitative detection by surface-enhanced Raman scattering (SERS) and inductively coupled plasma mass spectrometry (ICP-MS), and subsequently photothermal antibacterial assay. The sandwich nanocomposite consists of ConA-Fe₃O₄@SiO₂ NPs to magnetically enrich and photothermal killing bacteria, and dual-signal tags of apt-Au NNPs for both SERS sensing and ICP-MS quantification. This strategy can specifically distinguish different kinds of pathogenic bacteria, and provided a good linear relationship of Staphylococcus aureus (S. aureus) in the range from 50 to 10⁴ CFU/mL with a detection limit of 11 CFU/mL, as well as realized ultralow amounts of bacterial detection in serum sample with high accuracy. Based on the quantitative detection, high antibacterial efficiency was monitored by ICP-MS. Overall, the established method combines bacteria discrimination, quantitative detection, and photothermal elimination with a simple and rapid process, which provides a novel way for the early diagnosis and treatment of bacterial infection.

Multifunctional biosensor constructed by Ag-coating magnetic-assisted unique urchin core porous shell structure for dual SERS enhancement, enrichment, and quantitative detection of multi-components inflammatory markers

The simultaneous, precise, and quantitative detection of multi-components inflammatory markers (IMs) in sepsis serum by surface-enhanced Raman scattering (SERS) remains a challenging problem. A novel, multifunctional biosensor with dual enrichment and enhancement was designed for the ultrasensitive and quantitative analysis of multi-components IMs. The biosensor contains SERS tags-unique urchin core/porous shell (CPS) structure modified with Raman reporters (RaRs), magnetic assist-Ag coated Fe₃O₄ magnetic nanoparticles (Ag MNPs) modified with internal standard (IS), and then aptamer (Apt) modification to form the sandwich structure (Ag MNPs/IMs/CPS). This multifunctional sensor used for IM_S detection has the following innovations: The intensity ratio I_RaRs/I_IS with Lg C_IMs present a good and wide linear relationship to achieve the simultaneous, precise, and quantitative detection of IM_S in serum; The detection results display ultrasensitivity, and the limit of detection (LOD) for CRP, IL-6, and PCT is 100 fg/mL, 0.1 fg/mL, and 1.0 fg/mL, which is lower than other detection techniques; The calculated data of clinical blood samples of sepsis by this SERS method is consistent with the hospital results, and can provide more compositional data of IMs. Thus, this combined approach developed a sensing platform for rapid screening, accurate evaluation, early warning, and diagnosis of sepsis.

The rapid SERS detection of succinylcholine chloride in human plasma is based on the high affinity between quaternary ammonium salt structures

Succinylcholine chloride (SCC) is a common poison that threatens human life. At present, there is a lack of research on its on-site rapid detection methods. In this work, the use of gold nanorods as an enhanced substrate based on the high affinity between the quaternary ammonium salt structure can achieve rapid SERS detection of SCC in plasma. The long alkane chain structure of cetyltrimethylammonium bromide (CTAB) and the quaternary ammonium salt structure of SCC have a high molecular affinity, so that the target molecule can show a strong and obvious characteristic signal of SERS. Combined with a simple pretreatment method, acetonitrile is used as a protein precipitation agent to effectively remove matrix interference. The constructed SERS substrate can achieve the sensitive detection of 2 × 10^-8 M level of SCC in plasma samples and has high detection reproducibility. The entire pre-processing and testing process can be completed within 7 min, which can be used as an important technical basis for the preliminary identification of on-site SCC-related drug cases. The research results provide an effective solution for the establishment of SCC analysis strategies in complex matrices, and can provide new ideas for solving the problems of difficult identification of common poisons in the field and the lack of rapid detection methods on site.