Characterization of the molecular mass distribution of pullulans by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using 2,5-dihydroxybenzoic acid butylamine (DHBB) as liquid matrix

Pullulan in pharmaceutical and cosmeceutical formulations: A review

Pullulan, an α-glucan polysaccharide, is colorless, odorless, non-toxic, non-carcinogenic, highly biocompatible, edible and biodegradable in nature. The long chains of glucopyranose rings in pullulan structure are linked together by α-(1 → 4) and α-(1 → 6) glycosidic linkages. The occurrence of both glycosidic linkages in the pullulan structure contributes to its distinctive properties. The unique structure of pullulan makes it a potent candidate for both pharmaceutical and cosmeceutical applications. In pharmaceuticals, it can be used as a drug carrier and in various dosage formulations. It has been widely used in drug targeting, implants, ocular dosage forms, topical formulations, oral dosage forms, and oral liquid formulations, etc. Pullulan can be used as a potential carrier of active ingredients and their site-specific delivery to skin layers for cosmeceutical applications. It has been extensively used in cosmeceutical formulations like creams, shampoo, lotions, sunscreen, facial packs, etc. The current review highlights applications of pullulan in pharmaceutical and cosmeceutical applications.

Prolonged activity of exenatide: Detailed comparison of Site-specific linear polyglycerol- and poly(ethylene glycol)-conjugates

Exenatide is a small therapeutic peptide being currently used in clinic for the treatment of diabetes mellitus type II, however, displaying a short blood circulation time which makes two daily injections necessary. Covalent polymer modification of a protein is a well-known approach to overcome this limitation, resulting in steric shielding, an increased size and therefore a longer circulation half-life. In this study, we employed site-selective C-terminal polymer ligation of exenatide via copper-catalyzed azide-alkyne-cycloaddition (CuAAC) to yield 1:1-conjugates of either poly(ethylene glycol) (PEG) or linear polyglycerol (LPG) of different molecular weights. Our goal was to compare the impact of the two polymers on size, structure and activity of exenatide on the in vitro and in vivo level. Both polymers did not alter the secondary structure of exenatide and expectedly increased its hydrodynamic size, where the LPG-versions of exenatide showed slightly smaller values than their PEG-analogs of same molecular weight. Upon conjugation, GLP-1 receptor activation was diminished, however, still enabled maximum receptor response at slightly higher concentrations. Exenatide modified with a 40 kDa LPG (Ex-40-LPG) showed significant reduction of the blood glucose level in diabetic mice for up to 72 h, which was comparable to its PEG-analog, but 9-fold longer than native exenatide (8 h).

Ionic Liquid-Assisted Laser Desorption/Ionization-Mass Spectrometry: Matrices, Microextraction, and Separation

Ionic liquids (ILs) have advanced a variety of applications, including matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). ILs can be used as matrices and solvents for analyte extraction and separation prior to analysis using laser desorption/ionization-mass spectrometry (LDI-MS). Most ILs show high stability with negligible sublimation under vacuum, provide high ionization efficiency, can be used for qualitative and quantitative analyses with and without internal standards, show high reproducibility, form homogenous spots during sampling, and offer high solvation efficiency for a wide range of analytes. Ionic liquids can be used as solvents and pseudo-stationary phases for extraction and separation of a wide range of analytes, including proteins, peptides, lipids, carbohydrates, pathogenic bacteria, and small molecules. This review article summarizes the recent advances of ILs applications using MALDI-MS. The applications of ILs as matrices, solvents, and pseudo-stationary phases, are also reviewed.

Size and molecular weight determination of polysaccharides by means of nano electrospray gas-phase electrophoretic mobility molecular analysis (nES GEMMA)

Size, size distribution and molecular weight (MW) determination of nanoparticles and that are for example large polymers, are of great interest and pose an analytical challenge. In this context, nano electrospray gas-phase electrophoretic mobility molecular analysis (nES GEMMA) is a valuable tool with growing impact. Separation of single-charged analytes according to their electrophoretic mobility diameter (EMD) starting from single-digit EMDs up to several hundred nm diameters is possible. In case of spherical analytes, the EMD corresponds to the dry nanoparticle size. Additionally, the instrument is capable of number-based, single-particle detection following the recommendation of the European Commission for nanoparticle characterization (2011/696/EU). In case an EMD/MW correlation for a particular compound class (based on availability of well-defined standards) exists, a nanoparticle's MW can be determined from its EMD. In the present study, we focused on nES GEMMA of linear and branched, water-soluble polysaccharides forming nanoparticles and were able to obtain spectra for both analyte classes regarding single-charged species. Based on EMDs for corresponding analytes, an excellent EMD/MW correlation could be obtained in case of the branched natural polymer (dextran). This enables the determination of dextran MWs from nES GEMMA spectra despite high analyte polydispersity and in a size/MW range, where classical mass spectrometry is limited. EMD/MW correlations based on linear (pullulans, oat-ß-glucans) polymers were significantly different, possibly indicating challenges in the exact MW determination of these compounds by, for example, chromatographic and light scattering means. Despite these observations, nES GEMMA of linear, monosaccharide-based polymers enabled the determination of size and size-distribution of such dry bionanoparticles.

MALDI-TOF to compare polysaccharide profiles from commercial health supplements of different mushroom species

In this work MALDI-TOF mass spectroscopy was investigated to characterise the β-glucan profiles of several commercial health supplements, without any derivatisation or purification pre-treatment. The effect of two solvents (water and dimethyl sulfoxide) and two MALDI matrices (2,5-dihydroxybenzoic acid and 2',4',6'-trihydroxyacetophenone) was first evaluated on dextran standards. MALDI-TOF was found as a useful and quick technique to obtain structural information of diverse food supplements based on mushroom extracts. The MALDI polysaccharide profiles of 5 supplements from different mushroom species were qualitatively similar showing [Glucan+Na](+) cations with a peak-to-peak mass difference of 16 Da consistent with the repeating unit of the β-(1→3)-glucan. The profiles strongly depended on the sample solvent used, with m/z values around 5000-8000 for water and 2000 for dimethyl sulfoxide; differences between samples were revealed in the molecular weight of the aqueous preparation, with the highest values for Maitake and Cordyceps species.

Ionic liquids in bioanalysis

Ionic liquids (ILs) are entirely composed of ions and they possess fascinating properties, including low volatility, tunable viscosity, miscibility and electrolytic conductivity, which make them promising alternatives to traditional organic solvents used in sample preparation. The recent surge in the number of publications clearly indicates an increasing interest of the analytical and bioanalytical community toward these exciting and unique solvents. This article highlights the recent advances in the use of ILs as extraction solvents, as materials for separation and preconcentration in chromatographic techniques, and as matrices in mass spectrometric techniques for bioassays in biocomplex samples. We also briefly discuss the potential applications of ILs in biocatalysis.

Quantitative aspects in electrospray ionization ion trap and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of malto-oligosaccharides

Mass spectrometry is widely applied in carbohydrate analysis, but still quantitative evaluation of data is critical due to different ionization efficiencies of the constituents in a mixture. Different size and chemical structure of the analytes cause their uneven distribution in droplets (electrospray ionization, ESI) or matrix spots (matrix-assisted laser desorption/ionization, MALDI). In addition, instrumental parameters affect final ion yields. In order to study and optimize the latter, an equimolar mixture of malto-oligosaccharides (DP1-6) was analyzed using varying target masses for ESI as well as different matrices and laser power for MALDI. The sodium adducts and derivatives for positive ion mode (hydrazones with Girard's T Reagent, GT) and negative ion mode (reductively aminated with o-aminobenzoic acid, oABA) were studied. Negatively charged oABA-labeled malto-oligosaccharides turned out to be unsuitable for quantification of the malto-oligomeric composition. Best agreement was achieved when applying target masses in the range of the highest homolog in the mixture in electrospray ionization ion trap (ESI-IT) (1-2% deviation with GT label or as Na(+) adducts). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) gave best results when the laser power was adjusted significantly over the desorption/ionization threshold (1% deviation with GT label). Both parameters show significant influence on the determined oligomeric composition. Consequently, estimation and even quantitative determination of amounts of oligosaccharides in a mixture can be achieved when the analytes are labeled and the proper instrumental parameters are used.

Ionic liquid-assisted electrospray ionization of polysaccharides

In this work, we give the report of significant detection sensitivity improvement of electrospray ionization (ESI) mass spectra of polysaccharides by adding various ionic liquid compounds into samples. Mass spectra obtained were greatly simplified and appeared to be similar to spectra from matrix-assisted laser desorption/ionization due to the narrow charge number distribution. Mass spectra of polysaccharides with the attachment of either anion or cation of ionic liquid compounds were observed. No protonated or deprotonated polysaccharide ions were detected when ionic liquid compounds were added into samples. Little alkali-attached polysaccharide ions were observed. Ionic liquid-assisted ESI (ILA-ESI) mass spectrometry has significantly improved the detection sensitivity of large neutral polysaccharide compounds.

Recent advances in the use of encapsulated cells for effective delivery of therapeutics

Cell encapsulation can be defined as a living cell approach for the long-term delivery of therapeutic products. It consists of the immobilization of therapeutically active cells within a general polymer matrix that permits the ingress of nutrients and oxygen and the egress of therapeutic protein products but impedes the immune contact of the enclosed cells. In recent decades many attempts have evaluated the potential of this technology to release therapeutic agents for the treatment of different pathologies and disorders. At present, cell encapsulation may be used as a technological platform to improve knowledge and clinical use of stem cells. This review describes the main issues related to this cell-based approach and summarizes some of the most interesting therapeutic applications.

Ionic matrix for matrix-enhanced surface-assisted laser desorption ionization mass spectrometry imaging (ME-SALDI-MSI)

Matrix-enhanced surface-assisted laser desorption ionization mass spectrometry imaging (ME-SALDI MSI) has been previously demonstrated as a viable approach to improving MS imaging sensitivity. We describe here the employment of ionic matrices to replace conventional MALDI matrices as the coating layer with the aims of reducing analyte redistribution during sample preparation and improving matrix vacuum stability during imaging. In this study, CHCA/ANI (alpha-cyano-4-hydroxycinnamic acid/aniline) was deposited atop tissue samples through sublimation to eliminate redistribution of analytes of interest on the tissue surface. The resulting film was visually homogeneous under an optical microscope. Excellent vacuum stability of the ionic matrix was quantitatively compared with the conventional matrix. The subsequently improved ionization efficiency of the analytes over traditional MALDI was demonstrated. The benefits of using the ionic matrix in MS imaging were apparent in the analysis of garlic tissue sections in the ME-SALDI MSI mode.

Use of a novel ionic liquid matrix for MALDI-MS analysis of glycopeptides and glycans out of total tryptic digests

In this study, we investigated a novel ionic liquid matrix (ILM), namely, the 1,1,3,3-tetramethylguanidinium salt of 2,4,6-trihydroxyacetophenone (THAP). This matrix[1,1,3,3-tetramethylguanidinium 2,4,6-trihydroxyacetophenone (GTHAP)] turned out to be well suited for the matrix-assisted laser desorption/ionization mass spectrometric analysis of glycopeptides and glycans, and overcame the well-known ionization suppression of carbohydrate structures in the presence of peptides. The matrix was evaluated by two different series of experiments, in each case in comparison with the crystalline THAP matrix. In the first set of experiments, mass spectra were taken from unseparated tryptic digests of three glycoproteins taken as model compounds. Even glycopeptides containing short peptide backbones and large carbohydrate moieties gave high signal intensities when using the ILM though they did not appear in the THAP spectra. In the second set of experiments, the total tryptic digests were treated with endoglycosidase PNGase F to cleave off the N-linked glycans. When using the GTHAP matrix, it was possible to detect the glycans with high intensities in the presence of the tryptic peptides, whereas glycan ionization was completely suppressed when measured with the solid matrix THAP. The extent of metastable decay of glycopeptides was reduced when using the ILM. Altogether, GTHAP proved as a useful ILM particularly being superior to solid matrices in the context of glycosylation analysis.