Janusz Kasperczyk

Microstructural analysis of poly[(l,l-lactide)-co-(glycolide)] by 1H and 13C n.m.r. spectroscopy

Abstract The 13C nuclear magnetic resonance (n.m.r.) spectra were found to provide a means for direct observation of the structures formed along the glycolide/lactide copolymer chain upon transesterification. Nevertheless 1H n.m.r. spectroscopy appeared to be more convenient and useful in the analysis of chain microstructure. The glycolide methylene group region of the proton spectra exhibits several signals which can be ascribed to longer sequences (as compared to those giving rise to 13C resonances) as well as to the sequences which can appear only as a result of the second mode of transesterification. The analysis revealed that the longest blocks were in the copolymers prepared with A1(acac)3 as the initiator and the shortest blocks were in the copolymers obtained with tin initiators. A decrease in temperature was found to reduce the extent of the second mode of transesterification.

Stereoselective polymerization of racemic DL-lactide in the presence of butyllithium and butylmagnesium. Structural investigations of the polymers

Abstract The use of butyllithium and butylmagnesium in the polymerization of racemic lactide leads to the formation of polylactide with a partially disyndiotactic structure. A coefficient of stereoselectivity p2 which describes the content of disyndiotactic structures appears to be higher for the lithium initiator; however an increase in the concentration of this initiator tends to enhance an intermolecular transesterification process thus leading to the formation of totally random structures in a polylactide chain. In contrast, in the case of butylmagnesium, an increase in the initiator concentration does not induce the intermolecular transesterification processes.

The application of microspheres from the copolymers of lactide and ϵ-caprolactone to the controlled release of steroids

Abstract The microspheres made of the copolymers of lactide and ϵ-caprolactone were used for the controlled release of progesterone and β-estradiol. The copolymers contained 83–94% of l or d,l -lactide. The influence of the microstructure of lactidyl blocks in the copolymer chains on the drug release rate was studied. More uniform release rate was observed in the case of the copolymer derived from d,l -lactide as composed to l -lactide. For the copolymer containing 83–94% of d,l -lactide units the progesterone and β-estradiol release rate in vitro was found to be practically constant within over 40 days. The in vivo studies performed on rats revealed that the period of constant release rate of β-estradiol can be prolonged to about 70 days. The microspheres made of the applied poly-( d,l -lactide-co-ϵ-caprolactone) are the convenient system for long time release of steroids.

HETCOR NMR study of poly(rac-lactide) and poly(meso-lactide)

Abstract The application of heteronuclear chemical shift correlation (HETCOR) NMR allowed us to correlate the homodecoupled methine proton with the methine carbon signals of poly( rac -lactide) and poly( meso -lactide), and made it possible to perform a detailed analysis of 1 H NMR spectra (homodecoupled) and to ascribe the signals to configurational pentads. The assumption made by Chisholm and coworkers [Chisholm et al., Chem. Comm. 1997, p. 1999] that the previous assignment of methine carbon signals in 13 C NMR spectra was incorrect appeared to be wrong.

Lipids, lipid peroxidation and 7-ketocholesterol in workers exposed to lead

The study population included healthy men and hypertensive employees of zinc and lead steelworks in the south of Poland. Workers exposed to lead (n=137) were divided into two groups: the first included employees with low exposure to lead (LL) with mean blood lead (PbB) 25-40 μg/dL and the second one with PbB over 40 μg/dL (HL group). The administration workers (n=35) were the control group. Evaluation of lipids and oxidative changes of cholesterol and lipids were estimated in blood samples. No significant changes in concentration of 7-ketocholesterol and blood lipids (cholesterol, HDL, LDL, triglycerides) were found. Lipid peroxidation (LP) was significantly higher in both exposed groups in plasma and in the HL group in erythrocytes when compared with control. There can be two independent sources of LP increase: the first is connected with the direct effect of lead’s ions on erythrocytes, the second is the prooxidative effect of delta-aminolevulinic acid. Hypertension in the HL group when compared with people with PbB below 40 μg/dL (OR 4.4, 95%CI 1.4-40 mg/dL was found more often. LP significantly increased by about 71% and concentration of 7-ketocholesterol by about 122% in hypertensives when compared with normotensives in the HL group.

Copolymerization of glycolide andε-caprolactone, 2. Random copolymerization in the presence of tin octoate

The copolymerization of glycolide with e-caprolactone was performed in the presence of tin octoate at moderate temperatures (100 and 150°C). The influence of the conditions (comonomer ratio, temperature) on the chain microstructure of the obtained copolymers was examined. Transesterification was found to affect considerably the course of the process. The effect of copolymer composition and chain microstructure on thermal properties was also investigated. A phase separation of glycolidyl and caproyl microblocks was observed. The heat of melting of the crystalline phases was found to be dependent on the length of glycolidyl and caproyl microblocks.

New Conjugated Azomethines Containing Triphenylamine Core —Characterization and Properties

A novel polyazomethines bearing triphenylamine core and a proper model compound were synthesized and their spectroscopic (FTIR, 1 H NMR) and optical (UV-vis, photoluminescence) properties and also a molecular dynamic calculations were investigated. The polymers which were soluble in organic solvents (chloroform, dimethylacetamide, m-cresol) and formed transparent foils, emitted blue light and their photoluminescence band and intensity were solvent dependent. Additionally, the effects of blending the new polyazomethines with other polymers—PMMA, polyvinylophenol on UV-vis spectra were examined. Non-covalent ionic-type interactions between azomethines and methanesulfonic acid (MSA), m-cresol (MC) and p-chlorophenol (pClp) were also investigated. The structure formation of azomethines complexes are discussed on the basis of 1H NMR and FTIR. Photoluminescence and absorption properties of the azomethines compounds after doping with MSA, MC and pClp were tested.

Beta-carotene reduces oxidative stress, improves glutathione metabolism and modifies antioxidant defense systems in lead-exposed workers.

The aim of this study was to determine whether beta-carotene administration reduces oxidative stress and influences antioxidant, mainly glutathione-related, defense systems in workers chronically exposed to lead. The population consisted of two randomly divided groups of healthy male volunteers exposed to lead. Workers in the first group (reference group) were not administered any antioxidants, while workers in the second group (CAR group) were treated orally with 10mg of beta-carotene once a day for 12weeks. Biochemical analysis included measuring markers of lead-exposure and oxidative stress in addition to the levels and activities of selected antioxidants. After treatment, levels of malondialdehyde, lipid hydroperoxides and lipofuscin significantly decreased compared with the reference group. However, the level of glutathione significantly increased compared with the baseline. Treatment with beta-carotene also resulted in significantly decreased glutathione peroxidase activity compared with the reference group, while the activities of other glutathione-related enzymes and of superoxide dismutase were not significantly changed. However, the activities of glucose-6-phosphate dehydrogenase and catalase, as well as the level of alpha-tocopherol, were significantly higher after treatment compared with the baseline. Despite controversy over the antioxidant properties of beta-carotene in vivo, our findings showed reduced oxidative stress after beta-carotene supplementation in chronic lead poisoning.

Self-assembled filomicelles prepared from polylactide/poly(ethylene glycol) block copolymers for anticancer drug delivery.

Bioresorbable filomicelles present many advantageous as drug delivery systems e.g., long circulation time and high loading efficiency. The aim of this study was to develop polylactide/poly(ethylene glycol) (PLA/PEG) filomicelles for drug delivery applications. A series of PLA/PEG diblock copolymers were synthesized using non-toxic initiator, and characterized by means of NMR and GPC. Analysis of morphology of micelles determined by TEM revealed that apart from the weight fraction also the molar mass of PEG and the stereochemistry of PLA block must be considered for tailoring micellar structures. The CMC was found to be dependent on the length and structure of the hydrophobic block. It was observed that the drug loading properties could be improved by selection of appropriate copolymer and encapsulation method. Slower release of paclitaxel was observed for mPEG5000 initiated copolymers than mPEG2000 initiated copolymers. Moreover, the influence of the length of hydrophobic block and its stereoisomeric form on drug release rate was evidenced. Therefore, PLA/PEG filomicelles with good stability, high drug loading capacity and sustained drug release appear most attractive for drug delivery applications.

Synthesis of block copolymers of ε-caprolactone and lactide in the presence of lithium t-butoxide

SummaryHigh molecular mass copolymers with microphase separation can be obtained in block copolymerization of ε-caprolactone with L,L- and D,L-lactide carried out in the presence of lithium t-butoxide. A kind of solvent applied strongly affects the molecular mass and polydispersity index of obtained copolymers.