LASER DESORPTION/ABLATION POSTIONIZATION MASS SPECTROMETRY: RECENT PROGRESS IN BIOANALYTICAL APPLICATIONS.

Lasers have long been used in the field of mass spectrometric analysis for characterization of condensed matter. However, emission of neutrals upon laser irradiation surpasses the number of ions. Typically, only one in about one million analytes ejected by laser desorption/ablation is ionized, which has fueled the quest for postionization methods enabling ionization of desorbed neutrals to enhance mass spectrometric detection schemes. The development of postionization techniques can be an endeavor that integrates multiple disciplines involving photon energy transfer, electrochemistry, gas discharge, etc. The combination of lasers of different parameters and diverse ion sources has made laser desorption/ablation postionization (LD/API) a growing and lively research community, including two-step laser mass spectrometry, laser ablation atmospheric pressure photoionization mass spectrometry, and those coupled to ambient mass spectrometry. These hyphenated techniques have shown potentials in bioanalytical applications, with major inroads to be made in simultaneous location and quantification of pharmaceuticals, toxins, and metabolites in complex biomatrixes. This review is intended to provide a timely comprehensive view of the broadening bioanalytical applications of disparate LD/API techniques. We also have attempted to discuss these applications according to the classifications based on the postionization methods and to encapsulate the latest achievements in the field of LD/API by highlighting some of the very best reports in the 21st century. © 2020 John Wiley & Sons Ltd.

Development of laser ablation dielectric barrier discharge optical emission spectrometry (LA-DBD-OES) for direct determination of sulphur and chloride in the condensed phase and its application in pharmaceutical analysis.

An infrared laser (808 nm) has been coupled with dielectric barrier discharge (DBD) for optical emission spectrometric determination of S and Cl in organic compounds. The use of a continuous wave IR laser with an output power of 1-2 W allows volatilization of analytes from condensed surfaces. Analytes thermally delivered to the gas phase are excited and atomized by the DBD plasma triggered by an alternating voltage of 10 kV at 25 kHz under atmospheric pressure. Direct analysis of S- and Cl-containing organics in manufactured tablets by measuring the S and Cl emissions resulted in a dynamic range of 0.5%-20% with linearities (R2) above 0.93 and limits of detection (LODs) in the µg g-1 range. The detection precision was examined by measuring inter-day and intra-day reproducibilities, leading to relative standard deviations (RSDs) ranging from 4.6% to 15.0%. The feasibility of LA-DBD-OES was further demonstrated with commercial pharmaceutical tablets of sulfadiazine (SDZ) and chloramphenicol (CAP). There is the potential for probing the tablet uniformity by monitoring the elemental emissions of S and Cl. Quantitative results of the commercial tablets were consistent with the indication amounts and were verified by HPLC measurements. All these results suggest the proposed methodology as a promising tool for online analysis of solids and pharmaceutical tablets with minimal sample treatments and rapid detection response.

Enolate-mediated 1,3-dipolar cycloaddition reaction of ß-functionalized ketones with nitrile oxides: direct access to 3,4,5-trisubstituted isoxazoles.

TMG-catalyzed [3 + 2] organocatalytic 1,3-dipolar cycloaddition reactions of ß-functionalized ketones with nitrile oxides have been developed. This strategy could generate 3,4,5-trisubstituted isoxazoles in high yields and regioselectivities.

Enolate-mediated 1,3-dipolar cycloaddition reactions of allyl ketones with nitrile oxides: direct access to 3,5-disubstituted isoxazolines.

TMG-promoted [3 + 2] organocatalytic 1,3-dipolar cycloaddition reactions of allyl ketones with in situ generated nitrile oxides have been developed. This strategy could generate 3,5-disubstituted isoxazolines in high yields and regioselectivities.

Neuroprotective effect of chondroitin sulfate on SH­SY5Y cells overexpressing wild­type or A53T mutant α­synuclein.

Accumulation of α­synuclein (α­SYN) is a common pathology for Parkinson's disease (PD). There is abundant evidence that the toxic­gain­of­function of α­SYN's is associated with aggregation and consequent effects. To assess the potential of chondroitin sulfate (CS) in this regard, the present study investigated its neuroprotective on SH­SY5Y cells overexpressing wild­type (WT) or A53T mutant α­SYN. Cell viability was measured by MTT assay. Apoptosis, reactive oxygen species (ROS) and mitochondrial membrane potential were detected by flow cytometry. The protein expression levels of total α­SYN, phosphorylated Ser129 α­SYN, B­cell lymphoma 2 (Bcl­2), Bcl­2­associated X protein (Bax) and cytochrome­c (Cyt­c ) were analyzed by western blotting. It was observed that CS reduced the expression levels of total α­SYN and phosphorylated Ser129 α­SYN, prevented cell loss and inhibited apoptosis. The subsequent mechanism study indicated that CS inhibited ROS overproduction. CS also significantly attenuated WT and A53T mutant α­SYN­induced dysfunction, including decrease of mitochondrial membrane potential, decrease of Bcl­2 expression, and increase of Bax expression, release of Cyt­c from the mitochondria and activation of caspase­3 and caspase­9, which demonstrated that CS suppressed α­SYN­induced apoptosis possibly through mitochondria protection. These results suggested that CS protects SH­SY5Y cells overexpressing WT or A53T mutant α­SYN by inhibiting the expression and phosphorylation of α­SYN, and ROS overproduction and mitochondrial apoptosis. These results implicate CS as a potential therapeutic agent for the treatment of PD.

Sorafenib-based combined molecule targeting in treatment of hepatocellular carcinoma.

Sorafenib is the only and standard systematic chemotherapy drug for treatment of advanced hepatocellular carcinoma (HCC) at the current stage. Although sorafenib showed survival benefits in large randomized phase III studies, its clinical benefits remain modest and most often consist of temporary tumor stabilization, indicating that more effective first-line treatment regimens or second-line salvage therapies are required. The molecular pathogenesis of HCC is very complex, involving hyperactivated signal transduction pathways such as RAS/RAF/MEK/ERK and PI3K/AKT/mTOR and aberrant expression of molecules such as receptor tyrosine kinases and histone deacetylases. Simultaneous or sequential abrogation of these critical pathways or the functions of these key molecules involved in angiogenesis, proliferation, and apoptosis may yield major improvements in the management of HCC. In this review, we summarize the emerging sorafenib-based combined molecule targeting for HCC treatment and analyze the rationales of these combinations.

Effects of ghrelin on gastric distension sensitive neurons and gastric motility in the lateral septum and arcuate nucleus regulation.

BACKGROUND: Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor (GHS-R) and a peptide hormone that promotes food intake and gastric motility. Our aims are to explore the effects of ghrelin on gastric distension (GD) sensitive neurons in the lateral septum, and the possible regulation of gastric motility by ghrelin through the hypothalamic arcuate nucleus (ARC). METHODS: Single-unit discharges were recorded, extracellularly, and the gastric motility was monitored by the administration of ghrelin in the lateral septum. The projection of nerve fiber and expression of ghrelin were observed by retrograde tracer and fluo-immunohistochemistry staining. The expression of GHS-R and ghrelin was determined by real-time polymerase chain reaction and western blotting analysis. RESULTS: There were GD neurons in the lateral septum. The administration of ghrelin could excite both GD-excitatory (GD-E) and GD-inhibitory (GD-I) neurons in the lateral septum. Gastric motility was significantly enhanced by the administration of ghrelin in the lateral septum in a dose-dependent manner. Pretreatment with [D-Lys-3]-GHRP-6, however, could completely abolish the ghrelin-induced effects. Electrical stimulation of the ARC could significantly excite the response of GD neurons to ghrelin, increase ghrelin protein expression in the lateral septum and promote gastric motility. Nevertheless, these effects could be mitigated by pretreatment of [D-Lys-3]-GHRP-6. Electrical lesion of the lateral septum resulted in decreased gastric motility. The GHS-R and Ghrelin/FG-double labeled neurons were observed in the lateral septum and ARC, respectively. CONCLUSIONS: It is suggested that the lateral septum may receive afferent information from the gastrointestinal tract and promote gastric motility. Ghrelin plays an important role in promoting gastric motility in the lateral septum. The ARC may be involved in the regulation of the lateral septum's influence on gastric motility.