Molecular Weight Measurements Research Articles

Measurement of solution properties and molecular weight of hydroxyethyl starches using multi-angle laser light scattering: An interlaboratory comparison

The solution properties of hydroxyethyl starch (HES) vary significantly owing to different measurement parameters adopted and sample structures. Here, a round-robin study was conducted to compare inter-laboratory measurements of solution properties, weight-average molecular weight (Mw), and molecular weight distribution of four HES candidates covering the low- and medium-molecular-weight range, and 50 commercially available HES 130/0.4 drug samples. Analysis was performed using size exclusion chromatography (SEC) combined with multi-angle laser light scattering (MALLS) and differential refractive index (dRI) detectors. The results indicate that HES molecules in the Mw range of 17,000–130,000, with varying degrees of substitution (between 0.4 and 0.8), yielded a refractive index increment (dn/dc) value of 0.145 ± 0.003 mL/g (solvent: acetic acid-sodium acetate buffer; wavelength: 658 nm) and that the second virial coefficient (A2) is correlated with Mw. The SEC-MALLS-dRI method for Mw determination of HES demonstrated good inter-laboratory reproducibility; however, the study findings suggest that column specifications should be added for HES quality standards. Comparing Mw results obtained using common and experimentally corrected dn/dc and A2 values revealed an influence of dn/dc and A2 on Mw, indicating that the Mw acceptance criteria of HES quality standards should be adjusted.

Sequential extraction, preliminary characterization and functional properties of sesame (Sesamum indicum L.) hull polysaccharides

To expand the applications of sesame hull waste produced from industrial processing, five cell wall polysaccharide fractions of sesame hulls were sequentially extracted with water (WSP), chelator (CSP), sodium carbonate (NSP), 1 mol/L potassium hydroxide (KS1), and 4 mol/L potassium hydroxide (KS4). The preliminary structural characteristics of the five polysaccharide fractions were investigated by analytical techniques, such as sugar composition analysis, UV–vis, FT-IR, molecular weight measurement, and HSQC. The results showed that CSP had the main chain of xylogalacturonans and the content of galacturonic acid reached 70.07 g/100 g. Both KS1 and KS4 had xyloglucans backbones. NSP had the lowest molecular weight and the best thermal stability, while KS4 had the highest molecular weight. Rheological measurement indicated KS4 had the highest viscosity. The antioxidant abilities of NSP and KS1 were stronger than the other three fractions. This study provides valuable new information about the structural and functional properties of cell wall polysaccharides from sesame hulls.

Synthesis, characterization of ‎2-amino-pyran ‎and derivatives evaluation of the bacterial, ‎antioxidant and anticancer activity

Using ethanol as a solvent, heterocyclic hexagonal rings for 2-amino-pyran derivatives (I33-I40) were produced by reacting a mole of chalcones derivatives with a mole of malononitrile. Physical properties such as melting point, colour, and molecular weight and spectroscopic measurements such as the infrared spectrum, [1H-NMR], [13C-NMR] spectrum were used to confirm the accuracy of the prepared compounds' compositions. The biological activity of various produced compounds was investigated in two species of pathogenic bacteria, one of which is Gram-positive, Staphylococcus aureus, and the other, Gram-negative, Escherichia coli. Chemical solutions for the two substances (I25, I32) with concentrations (0,01, 0.001, 0.0001) mg /ml were created using a solvent DMSO and Multer Hinton Agar growth medium. The antibiotic Ciprofloxacin was utilized as a control sample for the diffusion sensitivity test of the bacterial isolates used in the investigation. Using DPPH root and varied concentrations, the impact of chemical (I32) on the elimination of free radicals was also investigated. Breast cancer cells were taken from Baghdad's Medical City and used to test the efficiency of several produced chemicals against them.

Driving Aspirational Process Mass Intensity Using Simple Structure-Based Prediction

An important metric for gauging the impact that a synthetic route has on chemical resources, cost, and sustainability is process mass intensity (PMI). Calculating the overall PMI or step-PMI for a given synthesis from a process description is more and more common across the pharmaceutical industry, especially in process chemistry departments. As with other pharmaceutical companies, our company has established a strong track record of delivering on our Corporate Sustainability goals, being recognized with eight EPA Green Chemistry Challenge Awards in the last 15 years, and we show how these routes help define aspirational PMI targets. While green chemistry principles help in optimizing PMI and developing more sustainable processes, a key challenge for the field is defining what a “good” PMI for a molecule looks like given its structure alone. An existing tool that chemists have at their disposal to predict PMI requires the synthetic route be provided or proposed (e.g., via retrosynthetic analysis) which then enables practitioners to compare predicted PMIs between routes. We have developed SMART-PMI (in-Silico MSD Aspirational Research Tool) to complement existing tools by predicting PMI from molecular structure alone. Using only a 2D chemical structure, we can generate a predicted SMART-PMI from a measure of molecular complexity and molecular weight. We show how these predictions correlate with historical PMI data from our company’s clinical and commercial portfolio of processes. From this SMART-PMI prediction, we have established target ranges which we termed “Successful”, “World Class”, and “Aspirational” PMI. The goal of this range is to set the floor for what is a “good” PMI for a given molecule and provide ambitious targets to drive innovative green chemistry. Using this model, chemists can develop synthetic strategies that make the biggest impact on PMI. As innovation in chemistry and processes leads to better and better PMIs, in turn, this data can drive ever more aggressive targets for the model. The potential of SMART-PMI, in combination with other existing PMI tools, to set industry-wide aspirational PMI targets is discussed.

Algorithm for estimating SARA fraction properties and its application in predicting the densities of heavy oils, bitumen and diluted bitumen with solvents

Using aromatic ring index (ARI) and the densities of saturates, aromatics, resins and asphaltenes (SARA) at any temperature, an algorithm was developed to iteratively estimate the molecular weights and specific gravities (60 °F) of the SARA fractions. The algorithm circumvents molecular weight measurements in reporting SARA fractions properties. Then, using the corresponding state principles the critical properties and acentric factor of the fractions were estimated using the correlations available in literature. Further, applying regular solution theory the densities of heavy oils, bitumen, and five diluted Athabasca bitumen with 5 solvents were predicted from Hankinson-Thomson and a compressed liquid density correlation. The average absolute deviation (AAD) in predicting the densities was found to be 1.33% for 1524 points with temperature range from 288 K to 463 K and pressure from 0.1 to 10 MPa. The method exhibits predictive ability and can be used satisfactorily for any heavy oil/bitumen/solvent system. In order to improve the accuracy of the calculated densities, a constant density translation method can also be applied to the bitumen/oil mixtures. When the translation method was used, the AAD of mixtures was improved to 0.69%. The proposed method was found to be better or comparable to other models in predicting densities.

Confronting the Challenge of Cellulose Molecular Weight Measurement: An Accurate, Rapid, and Universal Method with Ionic Liquid as an Additive.

Molecular weight parameters are the key fundamental information of polymer materials, but the accurate characterization of the molecular weight of cellulose is extremely difficult due to its strong hydrogen bonding network. Herein, we demonstrated two new methods to accurately and rapidly measure the molecular weight parameters of cellulose by using 1-butyl-3-methylimidazolium acetate (BmimAc) ionic liquid (IL) as an additive. Cellulose is rapidly dissolved in BmimAc/DMSO (1:1, w/w) at room temperature at first. Then, DMAc is added to dilute the solution, and finally, the molecular weight and molecular weight distribution of cellulose samples are measured by the gel permeation chromatography (GPC) method with BmimAc/DMSO/DMAc (1:1:18, w/w) as the mobile phase. Such a simple method is suitable to all kinds of cellulose samples and exhibits an extremely high analytical efficiency which is 50 times higher than the previous GPC methods. In addition, a viscosity method that is available for industrial application was proposed by using the BmimAc/DMSO/DMAc (1:1:8, w/w) system with low viscosity. The relationship between the intrinsic viscosity of the cellulose/BmimAc/DMSO/DMAc solution and the molecular weight of cellulose is well established and is applicable to cellulose samples of Mw = 4.5 × 104 to 1.8 × 106, which is the widest applicable range among the reported viscosity methods. Overall, two new methods based on the use of BmimAc as an additive have many advantages, such as wide applicable range, simple preparation process, mild dissolution condition, no degradation or aggregation of cellulose, high accuracy, fast detection, and low IL consumption, overcoming the existing problems in the traditional methods. It is expected to be used as a standard procedure to characterize the molecular weight of cellulose in academia and industries.

Analysis of Recombinant Adenovirus Vectors by Ion Trap Charge Detection Mass Spectrometry: Accurate Molecular Weight Measurements beyond 150 MDa.

Adenovirus is one of the largest nonenveloped, double-stranded DNA viruses. It is widely used as a gene therapy vector and has recently received a lot of attention as a novel vaccine platform for SARS-CoV-2. Human adenovirus 5 (HAdV5) contains over 2500 protein molecules and has a 36 kbp genome. Adenovirus is well beyond the range of conventional mass spectrometry, and it was unclear how well such a large complex could be desolvated. Here, we report molecular weight (MW) distributions measured for HAdV5 and for 11 recombinant AdV vectors with genomes of varying lengths. The MW distributions were recorded using ion trap charge detection mass spectrometry (CDMS), a single-particle technique where m/z and charge are measured for individual ions. The results show that ions as large as 150 MDa can be effectively desolvated and accurate MW distributions obtained. The MW distribution for HAdV5 contains a narrow peak at 156.1 MDa, assigned to the infectious virus. A smaller peak at 129.6 MDa is attributed to incomplete particles that have not packaged a genome. The ions in the 129.6 MDa peak have a much lower average charge than those in the peak at 156.1 MDa. This is attributed to the empty particles missing some or all of the fibers that decorate the surface of the virion. The MW measured for the mature virus (156.1 MDa) is much larger than that predicted from sequence masses and copy numbers of the constituents (142.5 MDa). Measurements performed for recombinant AdV as a function of genome length show that for every 1 MDa increase in the genome MW, the MW of the mature virus increases by around 2.3 MDa. The additional 1.3 MDa is attributed to core proteins that are copackaged with the DNA. This observation suggests that the discrepancy between the measured and expected MWs for mature HAdV5 is due to an underestimate in the copy numbers of the core proteins.

Monitoring Molecular Weight Changes during Technical Lignin Depolymerization by Operando Attenuated Total Reflectance Infrared Spectroscopy and Chemometrics.

Technical lignins are increasingly available at industrial scale, offering opportunities for valorization, such as by (partial) depolymerization. Any downstream lignin application requires careful tailoring of structural properties, such as molecular weight or functional group density, properties that are difficult to control or predict given the structure variability and recalcitrance of technical lignins. Online insight into changes in molecular weight (M w), to gauge the extent of lignin depolymerization and repolymerization, would be highly desired to improve such control, but cannot be readily provided by the standard ex‐situ techniques, such as size exclusion chromatography (SEC). Herein, operando attenuated total reflectance infrared (ATR‐IR) spectroscopy combined with chemometrics provided temporal changes in M w during lignin depolymerization with high resolution. More specifically, ex‐situ SEC‐derived M w and polydispersity data of kraft lignin subjected to aqueous phase reforming conditions could be well correlated with ATR‐IR spectra of the reaction mixture as a function of time. The developed method showed excellent regression results and relative error, comparable to the standard SEC method. The method developed has the potential to be translated to other lignin depolymerization processes.

Synthesis and characterization of some binuclear alkylene dithiophosphate complexes of bis(acetylacetonato)aluminium(III)-di-(μ-isopropoxo)di-isopropoxoaluminium(III) and sol-gel synthesis of nanosized θ-alumina

Reactions of bis(acetylacetonato)aluminum(III)-di-(μ–isopropoxo)-di-isopropoxoaluminum(III) (A) with a variety of alkylenedithiophosphoric acids in different molar ratio yield products of the type [(CH3COCHCOCH3)2Al(μ-OPri)2Al{S(S)P(O-G-O)n(OPri)2-n] (1-9) {where G = C(CH3)2C(CH3)2, n=1[1], n=2[2]; -CH2CH(C2H5), n=1[3], n=2[4]; CH2CH(CH3), n=1[5], n=2[6];C(CH3)2CH2CH(CH3), n=1[7]; CH(CH3)CH(CH3) n=1[8], n=2[9]}. Progress of the reactions was monitored by estimating liberated 2-propanol in benzene-2-propanol azeotrope by oxidimetric method. All pale coloured viscous products were soluble in common organic solvents and were characterized by elemental analyses, FT-IR and NMR (1H and 13C{1H} NMR) spectral studies. Molecular weight measurements in refluxing anhydrous benzene indicated binuclear nature of the complexes. 27Al NMR spectra of two of the derivatives, (1) and (2), suggested the presence of aluminium(III) atoms in different coordination states. 31P NMR spectra of the representative derivatives (1) and (2) exhibited only a single peak at 95.71 and 90.59 ppm, respectively suggesting tetra-coordination around phosphorus atom and a bidentate mode of chelation of the dithio ligand. Sol-gel transformation of Al(OPri)3 and [(CH3COCHCOCH3)2Al(μ-OPri)2Al(OPri)2] (A) followed by sintering at ~850°C yield alumina (a) and (b), respectively. The powder X-ray diffraction patterns, SEM images and FT-IR spectral studies of (a) and (b) indicated formation of nano-crystallites of θ -Al2O3 [PDF # 110517] in both the cases. The energy band gaps of 4.78 eV and 5.01 eV for (a) and (b), respectively were obtained from the absorption spectra.

Chromatographic Molecular Weight Measurements for Heparin , Its Fragments and Fractions, and Other Glycosaminoglycans.

Glycosaminoglycan samples are usually polydisperse, consisting of molecules with differing length and differing sequence. Methods for measuring the molecular weight of heparin have been developed to assure the quality and consistency of heparin products for medicinal use, and these methods can be applied in other laboratory contexts. In the method described here, high-performance gel permeation chromatography is calibrated using appropriate heparin molecular weight markers or a single broad standard calibrant and used to characterize the molecular weight distribution of polydisperse samples or the peak molecular weight of monodisperse, or approximately monodisperse, heparin fractions. The same technology can be adapted for use with other glycosaminoglycans.

Syntheses, Magnetic, Spectral and Biological Studies on the Coordination Compounds of N-(2-Hydroxyphenyl)-C-(3′- Carboxy-2′-Hydroxyphenyl) Thiazolidin-4-One

A dry benzene solution of the Schiff base, N-(2-hydroxyphenyl)-3′-carboxy-2′- hydroxybenzylideneimine upon reacting with mercaptoacetic acid undergoes cyclization and forms N- (2-hydroxyphenyl)-C-(3′-carboxy-2′-hydroxyphenyl)thiazolidin-4-one, LH3 (I). A MeOH solution of I reacts with Ni(II) and UO2(VI) ions and forms the monomeric coordination compounds, [Ni(LH)(MeOH)3] and [UO2(LH)(MeOH)]. The coordination compounds have been characterized on the basis of elemental analyses, molar conductance, molecular weight, spectral (IR, reflectance) studies and magnetic susceptibility measurements. I behaves as a dibasic tridentate OOS donor ligand in these compounds. The compounds are non-electrolytes (M = 4.3-6.4 mho cm2 mol-1) in DMF. Octahedral structure for Ni(II) and UO2(VI) compounds are suggested. LH3 (I) and its complexes while testing with E.Coli. (Gram Negative) and S. Aureus (Gram positive) bacteria show antibacterial activities.

Protein and glycan molecular weight determination of highly glycosylated HIV-1 envelope trimers by HPSEC-MALS

High Performance Size-Exclusion Chromatography coupled with Multi-Angle Light Scattering detection (HPSEC-MALS) is an important tool to provide a reliable molecular weight measurement for a large complex biomolecule. A recent HIV-1 soluble envelope trimer vaccine candidate, BG505 DS-SOSIP.664, is among the most glycosylated proteins to enter a clinical trial to date, and determination of its protein and glycan molecular weight is one of the key attributes in pre-clinical characterization. However, protein and glycans possess disparate dndcvalues making molecular weight measurement inaccurate in conventional SEC-MALS. To overcome these challenges, a simple mathematically guided experiment was explored, and a composite dndcvalue was established by utilizing protein and glycan mass contributions for the HIV-1 envelope trimer. This establishment was further verified by an orthogonal mass spectrometry analysis. This innovative, simple, and quick analytical approach can be applied broadly to measuring the molecular weight of various composite molecular structures, such as complex glycoconjugates.

Synthesis, spectral and sol-gel behavior of mixed ligand complexes of titanium(IV) with oxygen, nitrogen and sulfur donor ligands

A new route to synthesize nano-sized Ti(IV) mixed ligand complexes have been investigated by the reaction of titanium(IV) chloride with ammonium salts of dithiophosphate and 3(2'-hydroxyphenyl)-5-(4-substituted phenyl) pyrazolines. The resultant complex is then treated with H2S gas to get sulfur bridged dimer of Ti(IV) complex, a precursor of TiS2. The morphology of the complexes was studied by employing XRD which shows that all the complexes are amorphous solid. Molecular weight measurements, elemental analysis in conjugation with spectroscopic (IR, 1H NMR, 13C NMR and 31P NMR) studies revealed the dimeric nature of the complexes in which pyrazoline and dithiophosphate are bidentate. Scanning electron microscopic image and XRD indicate that the particles are in the nano range (50 nm). Putting all the facts together, coordination number six is proposed for titanium with octahedral geometry.
 
 KEY WORDS: Titanium(IV), Dithiophosphate, Pyrazoline, Nano-sized, Sol-gel, Mixed ligand complexes
 
 Bull. Chem. Soc. Ethiop. 2021, 35(1), 61-76.
 DOI: https://dx.doi.org/10.4314/bcse.v35i1.5

Purification, characterization and biological activities of exopolysaccharides from Lactobacillus rhamnosus ZFM231 isolated from milk

Exopolysaccharides (EPS) produced by Lactobacillus rhamnosus ZFM231 isolated from milk were purified by DEAE Cellulose-52 and Sephadex G-100 chromatography in sequence, obtaining four purified fractions EPS-1, EPS-2, EPS-3 and EPS-4. Among them, EPS-1 was a neutral polysaccharide and the others were acidic polysaccharides. The four factions were characterized by chemical composition analysis, molecular weight measurement, and UV, IR, 1H and 13C NMR spectra analysis. The antioxidant activity assays indicated that the purified fractions possessed appreciable ferric iron reducing power, free radical (DPPH, hydroxyl and superoxide anion radicals) scavenging ability and ferrous iron chelating ability. These purified exopolysaccharides were also found to possess marked hypolipidemic activity in vitro. The results showed that they were able to effectively inhibit lipase activity, and possessed remarkable activity in reducing cholesterol and triglyceride levels in the HepG2 cell models. Therefore, Lactobacillus rhamnosus ZFM231 and EPS produced by this probiotic strain may find application in food and pharmaceutical industries.

Styrene intermolecular associating incorporated-polyacrylamide flooding of crude oil in carbonate coated micromodel system at high temperature, high salinity condition: Rheology, wettability alteration, recovery mechanisms

Polymer flooding is one of the most well-known research interests in the enhanced oil recovery (EOR) due to the excess oil production and limited petroleum reserve. Commercial polymers such as polyacrylamide (PAM) and its hydrolyzed form (HPAM) can be easily degraded at high temperature, high salinity, and high shear rate in attempt to the EOR purposes for the harsh reservoir conditions. In this work, a hydrophobically modified copolymer consisting of acrylamide and styrene (HSPAM) was produced via inverse emulsion polymerization as a wettability modifier and viscosifying agent, applicable under harsh reservoir conditions to direct insights into the synergic oil recovery pore scale mechanisms and overcoming the aforementioned challenges through the EOR process. In the first part of this study, a set of analytical techniques including FTIR, NMR, TGA, and molecular weight measurement was carried out, confirming successfully incorporation of styrene monomer in water-soluble skeleton and higher thermal resistivity of HSPAM compared with HPAM. By analyzing the rheological behavior of HSPAM under harsh reservoir conditions, it was found that the viscosity of HSPAM aqueous solution was increasingly influenced by the total dissolved solids, even up to 40,572 mg/L. In the second part, stability tests, contact angle (CA), interfacial tension (IFT), and carbonate coated glass micromodel flooding experiments were conducted by deionized water (DIW), seawater (SW) and formation brine (FB) in the absence and presence of HSPAM and HPAM. HSPAM illustrated a great stability in seawater and formation brine in comparison with HPAM after 120 days at 80 °C. The presence of HSPAM in seawater resulted in a more water-wet state up to 42° compared to HPAM by contact angle of 31° after 72 h. Findings provided synergic oil recovery mechanisms approved by emulsification and coalition phenomena to show a better wettability alteration and IFT reduction for HSPAM in spite of HPAM alongside drastically improving the brine-based flooding performance, yielding an ultimate recovery of about 82% original oil in place (OOIP).

Separation and characterization of refractory colored dissolved effluent organic matter in a full-scale industrial park wastewater treatment plant.

Colored dissolved organic matter (DOM) is a significant indicator of refractory DOM in wastewaters, and fluorescent DOM is an essential part indicating colorants. However, little is known about the composition and contribution of colored DOM to wastewater. This study provided some insights on the persistent yellowish color in biological effluent through use of a multi-characterization approach, and evaluated the effect of two advanced treatments (O3 and granular active carbon (GAC)) in a full-scale wastewater treatment plant. The multi-characterization technique incorporated resin fractionation, excitation-emission matrix spectroscopy (EEM) combined with fluorescence regional integration (FRI), size-exclusion chromatography (SEC), and X-ray photoelectron spectroscopy (XPS) analysis. The fractionation results showed that hydrophobic acid (HPOA) and hydrophilic (HPI) substances are abundant in colorants, and HPI-type colorants are comparatively resistant or unable to be removed through GAC and O3 individually. FRI-based EEMs showed that F3 (fulvic acid-like organics) and F5 (humic acid-like organics) mainly account for the yellowish color, and their combined fractions of total colorants are 50%, 31%, and 48% in biological, biological + O3, and biological + GAC effluents, respectively. SEC for measurement of the apparent molecular weight revealed that these colorants may have molecular weights in the range 2-5 kDa. The XPS analysis indicated that these colorants possess ether or hydroxyl and nitro (C-O/C-N) chromophoric groups with conjugated aromatic structures. For C-O/C-N, O3 showed good removal efficiency overall. GAC showed exceptionally high efficiency for HPOA but very low efficacy toward HPI-type colorants in terms of C-O/C-N chromophoric functional group removal.

Synthesis and characterization of polyaniline composites with silica gel, styrene-divinyl benzene resin beads, calcium alginate and tetraethoxy silane substrates

Initially, Polyaniline (PAni) was synthesized in the powder form by chemical oxidative polymerization of aniline with ammonium persulphate in HCl medium. Further, composites of PAni with beads of silica gel, styrene-divinyl benzene resin beads and calcium alginate were prepared by in-situ chemical polymerization of aniline. Pre-formed base-PAni and tetraethoxysilane were used as precursors for the synthesis of PAni-siloxane composite disks. Ion exchange capacity of PAni powder was found to be 3.25 ± 0.084 meq g−1. PAni powder and its composites were characterized by elemental analysis, UV–visible and FTIR spectroscopy, TG-DSC, SEM, molecular weight and ion exchange capacity measurements. All the composites, except the alginate, were found to be thermally more stable than the powder form of PAni. The composite beads can be applied for future studies in the column mode of operations. Preliminary evaluation of the PAni-siloxane disc for arsenic sorption from aqueous solutions showed promising results. These disks are easy to handle, durable and the sorbed species can be directly quantified, i.e., without post-sorption processing, by energy dispersive X-ray fluorescence spectrometry.

Artificial Weathering Mechanisms of Uncoated Structural Polyethylene Terephthalate Fabrics with Focus on Tensile Strength Degradation.

In the past five decades, reinforced coated textile membranes have been used increasingly as building materials, which are environmentally exposed. Thus, their weathering degradation over the service life must be taken into account in design, fabrication, and construction. Regarding such structural membranes, PVC (polyvinylchloride)-coated PET (polyethylene terephthalate) fabric is one of the most common commercially available types. This paper focuses on the backbone of it, i.e., the woven PET fabric. Herein, weathering of uncoated PET, as the load-bearing component of the composite PET-PVC, was studied. This study assessed the uniaxial tensile strength degradation mechanisms of uncoated PET fabric during artificial accelerated weathering tests. For this purpose, exploratory data analysis was carried out to analyze the chemical and physical changes which were traced by Fourier transform infrared spectroscopy and molecular weight measurements. Finally, with the help of degradation mechanisms determined from the aforementioned evaluations, a degradation pathway network model was constructed. With that, the relationship between applied stress, mechanistic variables, structural changes, and performance level responses (tensile strength degradation) was assessed.

Monoorganosilicon(IV) Complexes of 2-Aminocyclopentene-1-carbodithioic Acid and its N-/S-Alkyl Derivatives: Synthesis and Characterization

2-Aminocyclopentene-1-carbodithioic acid (ACDA) and its N-/S-alkyl derivatives of methylsilicon(IV) chloride have been synthesized by the reactions of MeSiCl3 with sodium salt of ACDA and its N-/S-alkyl derivatives in 1:1 and 1:2 molar ratios. All these complexes have been characterized by elemental analysis, molecular weight measurements and spectroscopic (IR, 1H and 13C NMR) studies. The central silicon atom is coordinated to two sulphur atoms or one sulphur atom and one nitrogen atom of the ligand moiety in all of these derivatives, resulting in five and six coordination.

Влияние антибактериальных лекарственных средств на скорость гидролитической деградации алифатических полиэфиров

Supercritical fluid encapsulation of gentamicin, levofloxacin and tetracycline into bioresorbable polylacto-co-glycolic acid (PLGA) scaffolds at 20 wt. % was performed by PLGA plasticization in supercritical carbon dioxide with its subsequent foaming. The effect of incorporated antibiotics on the rate of PLGA hydrolytic degradation, determined by weekly measurements of the polymer molecular weight and gravitational masses decrease during 6 weeks scaffolds incubation in a phosphate-buffered saline (PBS) solution, has been studied. Measurements of pH of PBS containing scaffolds were carried out accordingly. The rate constants of PLGA hydrolysis for different scaffolds comprising various drugs were determined. It was shown that tetracycline significantly reduces the rate of PLGA degradation compared to the rate of control (pure polymer) scaffolds degradation. At the same time, the presence of gentamicin and levofloxacin in the scaffolds had no visible effect on their degradation. These results enhancing the predicting potential for considered antibiotics release kinetics from bioresorbable polymer carriers into bioactive media, what is necessary for the development of highly efficient sustained-release dosage forms.