Tacticity-Induced Changes in the Micellization and Degradation Properties of Poly(lactic acid)-block-poly(ethylene glycol) Copolymers

Poly(lactic acid)-block-poly(ethylene glycol) copolymers (PLA-b-PEG) featuring varying tacticities (atactic, heterotactic, isotactic) in the PLA block were synthesized and investigated for their micellar stability, degradation, and thermal properties. Utilizing tin(II) bis(2-ethylhexanoate), aluminum salan, and aluminum salen catalysts, the copolymers were synthesized through the ring-opening polymerization of d-, l-, rac-, or a blend of l- and rac-lactide using monomethoxy-poly(ethylene glycol) as a macroinitiator. The critical micelle concentration, which reflects the micellar stability, was probed using a fluorescence spectroscopic method with pyrene as the probe. The copolymers were degraded in a methanolic solution of 1,5,7-triaza-bicyclo[4.4.0]dec-5-ene and the degradation was measured by H-1 NMR spectroscopic and gel permeation chromatographic analyses. Differential scanning calorimetry and thermogravimetric analysis provided information on the thermal properties of the copolymers. Atactic and heterotactic microstructures in the PLA block resulted in lower micellar stability, as well as faster degradation and shorter erosion time compared to polymers with high isotactic enchainment (P-m). By modification of the P-m, micellar stability, degradation, and erosion rates of the copolymers can be tuned to specific biomedical applications. Interestingly, while tin(II) bis(2-ethylhexanoate) and aluminum salan-catalyzed PLA-b-PEG copolymers exhibited similar micellization behavior, the aluminum salen-catalyzed PLA-b-PEG exhibited unique behavior at high micelle concentration in the presence of the pyrene probe. This unique behavior can be attributed to the disintegration of the micelles through the interactions of long isotactic stereoblock segments

Aluminium salophen and salen initiators in the ring-opening polymerisation of <em>rac</em>-lactide and <em>rac</em>-β-butyrolactone: Electronic effects on stereoselectivity and polymerisation rates

Three aluminium salophen and two aluminium salen complexes were synthesised, characterised and screened in the ring-opening polymerisation (ROP) of rac-lactide and rac-β-butyrolactone. The focus was on controlling the apparent polymerisation rate (k p) and stereoselectivity of poly(lactic acid) and poly(3-hydroxybutyrate) by modulating the electron density at the aluminium centre or by switching from an alkyl backbone (salen complex) to an aryl backbone (salophen complex). The salen complexes generally showed higher k p as well as isoselectivity compared to the salophen complexes. For instance, salophen and salen complexes biased the microstructure of poly(3-hydroxybutyrate) towards syndiotacticity and isotacticity, respectively. Electron-withdrawing or electron-donating backbones on a salophen complex tuned k p, with electron-donating backbones offering faster k p

Physicochemical Characterization, Molecular Docking, and In Vitro Dissolution of GlimepirideCaptisol Inclusion Complexes

This present study investigated the effect of Captisol, a chemically modified cyclodextrin, on the in vitro dissolution of glimepiride. We prepared glimepirideCaptisol complexes of different mass ratios (1:1, 1:2, and 1:3 w/w) by a physical mixing or freeze-drying technique, and found that complexation with Captisol enhanced the water solubility of glimepiride. Molecular docking and dynamic simulation predicted complex formation; at the same time, Fourier transform infrared spectroscopy, differential scanning calorimetry, powder X-ray diffractometry, and scanning electron microscope indicated molecular interactions that support complexation. We also found that an inclusion complex was better than a physical mixture in enhancing the complexation of glimepiride with Captisol and enhancing water solubility. Phase solubility study of the glimepirideCaptisol complex showed an AL-type profile, implying the formation of a 1:1 inclusion complex. The study also revealed that pH influenced the stability of the complex because the stability constant of the glimepirideCaptisol complex was higher in distilled water of pH 6.0 than in phosphate buffer of pH 7.2

Electrospinning over Solvent Casting: Tuning of Mechanical Properties of Membranes

We put forth our opinion regarding the enhanced plasticity and modulation of mechanical properties of polymeric films obtained through electrospinning process in this article. In majority of the pharmaceutical, biomedical, and packaging applications, it is desirable that polymer based matrices should be soft, flexible, and have a moderate toughness. In order to convert inflexible and brittle polymers, adjuvants in the form of plasticizers are added to improve the flexibility and smoothness of solvent casted polymer films. However, many of these plasticizers are under scrutiny for their toxic effects and environmental hazards. In addition, plasticizers also increase the cost of end products. This has motivated the scientific community to investigate alternate approaches. The changes imparted in membrane casted by electrospinning were tried to be proved by SEM, Mechanical property study, DSC and XRD studies. We have showed dramatic improvement in flexibility of poly(ε-caprolactone) based nanofiber matrix prepared by electrospinning method whereas solvent casting method without any plasticizer produced very brittle, inflexible film of PCL. Modulation capacity of mechanical properties is also recorded. We tried to support our opinion by citing several similar findings available in the open literature. The electrospinning method helps in plasticization and in tuning mechanical properties

Physico-chemical characteristics of well waters in four urban centers in Southern Nigeria

An ensemble of thirty physico-chemical characteristics was used to assess the quality of well waters in four urban centers in southern Nigeria: Lagos, Benin City, Warri, and Ekpoma. The characteristics investigated include pH; color; turbidity; salinity; electrical conductivity, EC; total dissolved solids, TDS; total suspended solids, TSS; dissolved oxygen, DO; total hydrocarbon, THC; biochemical oxygen demand, BOD; chemical oxygen demand, COD; and nitrate, nitrite, ammonia, sulfate, and phosphate concentrations. Also monitored were the concentrations of sodium, calcium, potassium, magnesium, chloride, bicarbonate, iron, lead, copper, manganese, zinc, chromium, nickel, and cadmium. The results obtained were compared with World Health Organization, WHO, and Nigerian Federal Ministry of Environment, FME, drinking water standards. The results show that with the well water obtained from Lagos, turbidity, 11.80 NTU; pH, 5.68; EC, 1065.55 μS/cm; TDS, 539.00 mg/L; concentrations of iron, 1.83 mg/L; manganese, 0.14 mg/L; and lead, 1.35 mg/L did not meet the WHO standards. In Warri, pH, 5.19; concentrations of lead, 1.35 mg/L; and chromium, 0.10 mg/L in the well water were above the WHO desirable limits. The results also indicated that the well water from Benin City contained concentrations of chromium, 0.18 mg/L; and lead, 0.20 mg/L that exceeded the recommended WHO limits. In Ekpoma, the pH, 6.00; concentrations of chromium, 0.15 mg/L; and lead, 0.44 mg/L were higher than the desirable limits of WHO. Generally, the assessments revealed that the waters were good and fit for drinking and other domestic application without serious threat to public health

Some aspects of palm oil bleaching with activated plantain peel ash

The present study seeks to investigate the bleaching of palm oil with activated plantain peel ash (APPA). Concentrations of P-carotene, iron, copper, lead, and phosphorus in the crude (unbleached) and bleached palm oil were evaluated. The peroxide value, anisidine value, acidity and colour of the oils were also determined. The objectives were to assess the bleaching performance of the APPA, compare the performance of APPA with that of a commercial natural earth (Pure-Flo Neutral B-80) and investigate the effects of particle size of APPA and APPA/oil ratio on the bleaching performance of APPA. The results indicated that APPA significantly decreased all the investigated characteristics apart from acidity. Results also indicated that Pure-Flo Neutral B-80 slightly performed better than APPA under the same experimental conditions

Towards the reduction of matrix effects in inductively coupled plasma mass spectrometry without compromising detection limits: The use of argon-nitrogen mixed-gas plasma

The multivariate optimization of a mixed-gas plasma was conducted in an attempt to find conditions minimizing matrix effects without sacrificing the detection limits that are observed with an all argon plasma optimized for maximum sensitivity in inductively coupled plasma mass spectrometry. Compared to the latter, where 49.1 +/- 7.1% (n = 17) analyte signal suppression resulted in the presence of 0.1 M Na, 3.8 +/- 3.2% suppression (and 2.8 +/- 2.1% enhancement in some cases) was observed in the optimized mixed-gas plasma with 0.13% v/v N-2 in the plasma gas and 0.11% in the central channel as a sheath gas around the nebulizer gas flow. Furthermore, improved detection limits were observed for Al, Co, Pd, and V with the optimized mixed-gas plasma compared to an argon plasma at maximum sensitivity. The robustness of this mixed-gas plasma was further demonstrated through the accurate determination of U and Mo in NASS-5 seawater certified reference material using a simple external calibration, without matrix-matching or internal standardization. Indeed, the result obtained for Mo (9.1 +/- 1.9 mu g/L) was within the 95% confidence interval of the certified value of 9.6 +/- 1.0 mu g/L, while that obtained for U (3.0 +/- 0.2 mu g/L) was close to the information value of 2.6 mu g/L Spatial profiling results suggest better energy transfer between the toroidal zone and the central channel in the mixed-gas plasma. (C) 2010 Elsevier B.V. All rights reserved

PHENOLIC CONTENT AND ANTIMICROBIAL POTENTIALS OF XYLOPIA AETHIOPICA AND MYRISTICA ARGENTEA

The Folin-Ciocalteu method was used to quantify the total phenolics in the aqueous extract of two spices, Xylopia aethiopica and Myristica argentea. A modified agar streak dilution method was used to assess the susceptibility of Escherichia coli and Staphylococcus aureus to the aqueous extracts of the spices. The results showed that high levels of phenolics were present in the extracts. The extracts also showed high-modest antimicrobial activity against the tested bacteria

Matrix effects in inductively coupled plasma mass spectrometry: A review

Fundamental research on non-spectroscopic interferences, also known as matrix effects, in inductively coupled plasma (ICP) mass spectrometry with sample introduction using nebulization is critically and exclusively examined in this review, starting with fundamental processes that may be a source of matrix effects during sample introduction, ion generation in the ICP, ion extraction through the interface, and ion transport through the ion optics to the detector. Various methods for attenuating matrix effects are then reviewed and illustrated with some examples. Instead of exhaustively reviewing the literature, representative references are used to comprehensively describe the main issues, several of which are also common to ICP optical emission spectrometry. (C) 2011 Elsevier B.V. All rights reserved

Studies of corrosion tendency of drinking water in the distribution system at the University of Benin

Ensemble of corrosion indices was combined to study the corrosion tendency of the drinking water supply at the University of Benin, Nigeria. The experimental results were analysed in terms of three corrosion indices-Langelier Index, Ryznar Index and Larson–Skold Index. According to the evaluation, the Langelier Index ranged from −5.569 to −3.684, Ryznar Index was between 13.340 and 16.418 while the Larson–Skold Index was between 1.191 and 31.750. Results indicated that the water may be corrosive. A regression of these indices on iron concentration (ppm) showed that Langelier Index, Ryznar Index and Larson–Skold Index have R 2 of 0.5868, 0.6577 and 0.7063, respectively. The positive correlation between iron levels and the corrosion indices suggested that iron levels were directly related to increase in corrosion tendency