Journal of Analysis and Testing

Lipidomics is a subfield of metabolic phenotyping that focuses on high-throughput profiling and quantification of lipids. Essential roles of lipidomics in translational and clinical research have emerged, especially over the past decade. Most lipidomic pipelines have been developed using mass spectrometry (MS)-based methods. Because of the complexity of the data, generally, computational demands are much higher in untargeted lipidomic studies. In the current paper, we primarily discussed the recent advances in untargeted liquid chromatography–mass spectrometry-based lipidomics, covering various facets from analytical strategies to functional interpretations. The current practice of tandem MS-based lipid annotation in untargeted lipidomics studies was demonstrated. Notably, we highlighted the essential characteristics of machine learning models, together with a data partitioning strategy, to facilitate appropriate modeling and validation in metabolic phenotyping studies. Critical aspects of data sharing were briefly mentioned. Finally, certain recommendations were suggested toward more standardized and sustainable lipidomics analysis strategies as independent platforms, and as members of the omics family.

Many sensors for Cu2+ rely on the catalytic activity of Cu2+ to produce a color change, but these colorimetric sensors often suffer from poor selectivity and are susceptible to interference. In this work, we found that Cu2+-catalyzed TMB oxidation can be significantly improved with excessed nucleotides and nucleosides. Especially, with oversaturated guanosine 5′-monophosphate (GMP) to form a coordination nanozyme, the catalytic efficiency was greatly accelerated. It can be attributed to the specific binding between the electron-rich oxygen and nitrogen atoms of guanine with Cu2+. A sensitive and selective strategy for Cu2+ sensing was proposed. Owing to the presence of excessed GMP, it ensures robust activity and less susceptibility to interference. This allowed us to test the sensor in complex samples such as the seawater. This work strongly suggests that by supplying excessed ligands, far exceeding the binding stoichiometry, we may produce more robust sensing systems.

The controllable growth of metal nanoparticles on nanomaterials is becoming an effective strategy for developing nanocomposites with designated performance. Herein, a simple and mild strategy for the in situ growth of Pt–Pd bimetallic nanoparticles on covalent organic frameworks (COFs) to regulate the nanozyme activity was designed for colorimetric detection of hydrogen peroxide (H2O2) and glutathione (GSH). The COFs not only offer sufficient loading sites for the uniform dispersion of Pt–Pd bimetallic nanoparticles, but also increase the adsorption of substrate to promote the catalytic reaction. With the bimetallic synergistic effect of Pt–Pd nanoparticles, the prepared multifunctional nanozyme (Pt–Pd/COFs nanozyme) simultaneously exhibited superior peroxidase (POD)-like activity and oxidase (OXD)-like activity. Using the multifunctional nanozyme, a colorimetric sensing system was constructed for sensitive detection of H2O2 and GSH, with the wide linear ranges of 5–1000 µmol/L and 1–40 µmol/L, and the detection limits were 1.14 μmol/L and 0.43 μmol/L, respectively. It was successfully used for the detection of real samples in environmental water and serum, providing a simple method for disease diagnosis and environmental monitoring.

The G-quadruplexes undergo complex folding and conformation exchanges. G-quadruplex stability is substantially influenced by sequence, buffer and temperature. Mutational analysis together with nuclear magnetic resonance spectroscopy (NMR), X-ray crystallography and circular dichroism spectroscopy has been proved to be a powerful approach for G-quadruplex structural analysis. Herein, we used DNA sequence mutation and native polyacrylamide gel electrophoresis to investigate the topology and conformations of a G-quadruplex model molecule Pu18 found in the human c-MYC promoter. The guanines (G6, G9 or G18) which were not contributable to G-tetrad formation in c-MYC Pu18 sequence were mutated to thymine or adenine. We screened the buffer and temperature of gel electrophoresis for Pu18. Gel electrophoresis showed that two of the four conformers of c-MYC Pu18 in 100 mM K+ buffer were resolved, which was in accordance with the conformations as determined by the 1H NMR spectra in previous studies. This technique is expected as a general methodology for its easy operation and low cost to facilitate uncovering more yet unidentified G-quadruplex folds and functions, with the assistance of other analytical methods like NMR, X-ray crystallography and circular dichroism spectroscopy.

Electrogenerated chemiluminescence (ECL) has been extensively used in ultrasensitive electroanalysis because it can be generated electrochemically without using expensive optics and light sources. Visible ECL emission can be obtained with a reasonable quantum yield and stability. Blue ECL is rare and often suffers from stability and poor quantum efficiency. Blue ECL emission at 473 nm from organometallic halide perovskite nanocrystals (PNCs), CH3NH3PbCl1.08Br1.92, is reported here for the first time using tripropylamine (TPrA) as co-reactant. The blue ECL emission peak resembles its photoluminescence peak position. In addition to this blue emission peak, the ECL spectra of CH3NH3PbCl1.08Br1.92 PNCs also showed a broad ECL peak at 745 nm. Generation of the second ECL peak at 745 nm from CH3NH3PbCl1.08Br1.92 PNCs was can be explained by the existence of surface trap states on as-synthesized PNC due to incomplete surface passivation. Halide anion tunability of ECL emission from CH3NH3PbX3 (X: Cl, Br, I) PNCs is also demonstrated. The fluorescence microscopy image of single PNC and stability of selected single PNCs are presented in this with simultaneous acquisition of fluorescence spectra using 405-nm laser excitation. The photoluminescence (PL) decay was described by PL lifetime (τ) of 1.2 ns. The effect of the addition of surfactants (oleic acid and n-octylamine) on the fluorescence intensity and stability of CH3NH3PbCl1.08Br1.92 PNCs is also discussed.

Okadaic acid (OA), a small molecule substance derived from shellfish, is one of the most widely distributed marine toxins with acute symptoms of vomiting and diarrhea after accidental ingestion. For this, there is an urgently need for sensitive and reliable methods to detect OA in real shellfish samples. In this study, a simple aptasensor based on screen-printed carbon electrode (SPCE) with modification of chitosan (CS) and gold nanoparticles (AuNPs) was designed for electrochemical determination of OA, and the electrode surface was modified with AuNPs by potential-sweeping electrodeposition, which greatly improved the electrochemical response. The entire detection and characterization process were carried out by cyclic voltammetry (CV) with a linear correlation in the range of 0.01–100 ng/mL and a limit of detection (LOD) of 6.7 pg/mL. Furthermore, recovery rates of 92.3–116% were obtained demonstrating excellent accuracy through the recovery trial of mussel and scallop samples.

Trace ferric ion (Fe3+) detection has attracted increasing attention as an essential and indispensable role in many physiological and pathological research. The green-emitting carbon quantum dots (Green-CQDs) were obtained through a green and facile one-step hydrothermal method for the specific recognition and trace detection of Fe3+ in this paper. The optimal excitation and emission wavelengths of the CQDs were 395 nm and 490 nm, respectively. The stokes shift was up to 95 nm, which can effectively reduce the background fluorescence interference. In addition, it also exhibited good water solubility, stability, and high biocompatibility. The fluorescence intensity of Green-CQDs was linearly related to the concentration of Fe3+ (range of 0–80 μmol/L), and the detection limit was as low as 59 nmol/L. These good properties were favorable and successful for Fe3+ detection in tap water, human serum samples and living cells. In addition, a fluorescence visual test paper (FP@CQDs) was prepared utilizing filter paper as carrier, which can quickly identify Fe3+ in real time, and is suitable for the visualization analysis of Fe3+ in environment. As an efficient nanoprobe, the Green-CQDs held great promise and bright prospects in practical application in prevention and early clinical diagnosis of Fe3+-associated diseases.