Matrix-assisted laser desorption/ionization mass spectrometry for quantitative determination of β-blocker drugs in one-drop of human serum sample

Protein-Adsorbed Magnetic-Nanoparticle-Mediated Assay for Rapid Detection of Bacterial Antibiotic Resistance

Antibiotic susceptibility tests have been used for years as a crucial diagnostic tool against antibiotic-resistant bacteria. However, due to a lack of biomarkers specific to resistant types, these approaches are often time-consuming, inaccurate, and inflexible in drug selections. Here, we present a novel susceptibility test method named protein-adsorbed nanoparticle-mediated matrix-assisted laser desorption-ionization mass spectrometry, or PANMS. Briefly, we adsorb five different proteins (β-casein, α-lactalbumin, human serum albumin, fibrinogen, and avidin) onto the surface of Fe₃O₄. Upon interaction with bacteria surface, proteins were displaced from the nanoparticle surface, the amounts of which were quantified by matrix-assisted laser desorption ionization mass spectrometry. We find that the protein displacement profile was different distinctive among different bacteria strains and, in particular, between wild-type and drug-resistant strains. More excitingly, we observe bacteria resistant to drugs of the same mechanisms share similar displacement profiles on a linear discriminant analysis (LDA) map. This suggests the possibility of using PANMS to identify the type of mechanism behind antibiotic resistance, which was confirmed in a blind test. Given that PANMS is free of drug incubation and the whole procedure takes less than 50 min, it holds great potential as a high-throughput, low-cost, and accurate drug susceptibility test in the clinic.

Retaining activity of enzymes after capture and extraction within a single-drop of biological fluid using immunoaffinity membranes

The purpose of this study was the measurement of enzyme activity within a single-drop of biological fluid after micropurification. Esterase and lactate dehydrogenase (LDH) retained their enzymatic activities after being captured by membrane-immobilized antibodies, which were prepared by non-denaturing two-dimensional electrophoresis, transferred to polyvinylidene difluoride and then stained by Ponceau S. The activities of both enzymes were also measured after being captured by antibodies and biotinylated antibodies bound to membrane-immobilized protein A or avidin, respectively. After esterase and LDH were captured from biological samples by membrane-immobilized protein A or avidin, their activities were semi-quantitatively measured on the surface of the membrane using fluorescence determination. More than 51% of enzyme activities were retained even after the enzymes were captured by biotinylated antibody bound to membrane-immobilized avidin and eluted by rinsing with 5μL of 1% Triton X-100, compared with the activities of the enzyme on the immunoaffinity membrane.

Ionic liquid matrix-based dispersive liquid-liquid microextraction for enhanced MALDI-MS analysis of phospholipids in soybean

Ionic liquid matrix (ILM) is found to be a very versatile substance for analysis of broad range of organic molecules in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) due to good solubility for a variety of analytes, formation of homogenous crystals and high vacuum stability of the matrix. In the present work, an ILM, cyno-4-hydroxycinnamic acid-butylamine (CHCAB) was employed in dispersive liquid-liquid microextraction (DLLME) as sample probe and matrix for extraction and ionization of phospholipids from food samples (soybean) prior to MALDI-MS analysis. With the employed technique, 8-125 fold improvement in signal intensity and limit of detection were achieved for the analysis of phospholipids. The best extraction efficiency of phospholipids in ILM-DLLME was obtained with 5min extraction time in presence 30mg/mL CHCAB and 1.2% NaCl using chloroform as an extracting solvent and methanol as a dispersing solvent. Further, the developed ILM-DLLME procedure has been successfully applied for the analysis of phospholipids in soybean samples in MALDI-MS.

Comparison of the Usefulness of SPE Cartridges for the Determination ofβ-Blockers andβ-Agonists (Basic Drugs) in Environmental Aqueous Samples

Even though the methodology used for the determination ofβ-blockers andβ-agonists in environmental samples is based mainly on solid-phase extraction (SPE) and gas chromatography or liquid chromatography with mass spectrometric detection, the available literature data on the applied SPE procedures is rather sparse. In this paper such comparison is presented. Moreover, the usefulness of the eight SPE cartridges for the determination of fiveβ-blockers (acebutolol, atenolol, metoprolol, nadolol, and propranolol) and twoβ-agonists (salbutamol and terbutaline) in environmental aqueous samples using GC techniques is tested. Among them, three (the trifunction sorbent Strata Screen C, the copolymers LiChrolut EN, and the functionalized copolymer Isolute ENV+) were used for the first time for this purpose. It was confirmed that polystyrene-divinylbenzene-N-vinylpyrrolidone copolymers (PS-DVB-VP, Strata-X, and Oasis HLB cartridges) have a better potential than a cation-exchange sorbent for the extraction of the target drugs from environmental water samples. However, it should be stressed out that the direct application of the tested SPE conditions for the analysis of real environmental water samples is not possible, and such parameters, like volume of loading sample, appropriate solvents for washing and elution steps, and so forth, must be optimized again in order to achieve satisfactory recovery values for the target compounds.

Quantitative mass spectrometry imaging of propranolol and olanzapine using tissue extinction calculation as normalization factor

In order to quantify small molecules at the early stage of drug discovery, we developed a quantitation approach based on mass spectrometry imaging (MSI) using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) without the use of a labeled compound. We describe a method intended to respond to the main challenges encountered in quantification through MALDI imaging dedicated to whole-body or single heterogeneous organ samples (brain, eye, liver). These include the high dependence of the detected signal on the matrix deposition, the MALDI ionization yield of specific target molecules, and lastly, the ion suppression effect on the tissue. To address these challenges, we based our approach on the use of a normalization factor called the TEC (Tissue Extinction Coefficient). This factor takes into account the ion suppression effect that is both tissue- and drug-specific. Through this protocol, the amount of drug per gram of tissue was determined, which in turn, was compared with other analytical techniques such as Liquid Chromatography-Mass spectrometry (LC-MS/MS).