scholarly journals Enhanced Degradation of Lactide-co-Glycolide Polymer with Basic Nucleophilic Drugs

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Susan D’Souza ◽  
Jabar A. Faraj ◽  
Rossella Dorati ◽  
Patrick P. DeLuca
Keyword(s):  
Molecular Weight ◽  
Weight Reduction ◽  
Polymer Degradation ◽  
Plga Microspheres ◽  
Excellent Correlation ◽  
Polymer Molecular Weight ◽  
First Order Kinetics ◽  
Polymeric Microsphere ◽  
Evaporation Technique ◽  
Series Of Experiments

The purpose of this study was to examine the degradative effect of weakly basic nucleophilic drugs on a lactide-co-glycolide (PLGA) polymer in a microsphere formulation. Biodegradable PLGA microspheres of two second-generation atypical antipsychotics, Risperidone and Olanzapine, were manufactured using a solvent extraction/evaporation technique. The effect of drug content, buffer pH and temperature on polymer molecular weight and degradation, were examined via a series of experiments and compared against a control (Placebo PLGA microspheres). In comparison to Placebo microspheres, significant polymer molecular weight reduction was observed upon encapsulation of varying levels of either Risperidone or Olanzapine. There was excellent correlation between the extent of molecular weight reduction during manufacture and the amount of encapsulated drug in the microspheres. Subsequent studies on polymer degradation showed: the following (a) the Placebo and Olanzapine microspheres followed pseudo first order kinetics, (b) Risperidone microspheres exhibited biphasic degradation profiles, and (c) polymer degradation was dependent on temperature, not pH. The findings of these studies show that encapsulation of weakly basic nucleophile type drugs into PLGA can accelerate the biodegradation of the PLGA and have major implications on the design of polymeric microsphere drug delivery systems.

Crystallization of Isotactic Poly(propylene) in Solution as Followed by Slow Calorimetry

1995 ◽  
Vol 60 (11) ◽  
pp. 1905-1924 ◽  
Author(s):  
Hong Phuong-Nguyen ◽  
Geneviève Delmas
Keyword(s):  
Molecular Weight ◽  
Crystal Growth ◽  
High Temperature ◽  
Heat Of Fusion ◽  
Complete Dissolution ◽  
Polymer Molecular Weight ◽  
Solvent Quality ◽  
Temperature Ramp ◽  
Poly Propylene

Dissolution, crystallization and second dissolution traces of isotactic poly(propylene) have been obtained in a slow temperature ramp (3 K h-1) with the C80 Setaram calorimeter. Traces of phase-change, in presence of solvent, are comparable to traces without solvent. The change of enthalpy on heating or cooling, ∆Htotal, over the 40-170 °C temperature range, is the sum of two contributions, ∆HDSC and ∆Hnetwork. The change ∆HDSC is the usual heat obtained in a fast temperature ramp and ∆Hnetwork is associated with a physical network whose disordering is slow and subject to superheating due to strain. When dissolution is complete, ∆Htotal is equal to ∆H0, the heat of fusion of perfect crystals. The values of ∆Htota for nascent and recrystallized samples are compared. Dissolution is the tool to evaluate the quality of the crystals. The repartition of ∆Htotal, into the two endotherms, reflects the quality of crystals. The crystals grown more rapidly have a higher fraction of network crystals which are stable at high T in the solvents. A complete dissolution, i.e. a high temperature (170 °C or more) is necessary to obtain good crystals. The effect of concentration, polymer molecular weight and solvent quality on crystal growth is analyzed.

The Reactions of Substituted Germyl- and Silylhydrazines with BX3 and CY2 Acceptor Species

1972 ◽  
Vol 50 (4) ◽  
pp. 562-566 ◽  
Author(s):  
L. K. Peterson ◽  
K. I. Thé
Keyword(s):  
Molecular Weight ◽  
Nitrogen Atom ◽  
Low Temperatures ◽  
Adduct Formation ◽  
Steric Effects ◽  
Reaction Products ◽  
Hydrazine Derivatives ◽  
Basic Catalysts ◽  
Series Of Experiments ◽  
Electronic And Steric Effects

Boron trimethyl reacts with each of the organometalloid-hydrazine derivatives Me2NN(R)GeMe3 (R = H, Me, SiMe3) except Me2NN(SiMe3)GeMe3, and with Me2NNHSiMe3, forming 1:1 adducts. With Me2NN(SiMe3)GeMe3 and BMe3, no adduct was formed even at low temperatures. On the basis of p.m.r. spectra, the metalloid-substituted nitrogen atom rather than the terminal nitrogen, is indicated as the basic center at which adduct formation occurs. With BF3, the Si—N and Ge—N bonds of the hydrazine derivatives were cleaved, again indicating attack at the central nitrogen atom. In a series of experiments involving CY2 (Y = O, S) and Me2NN(R)MMe3 (R = H, Me, SiMe3; M = Si, Ge), reaction occurred readily for R = H, but less readily for R = Me and for the compound Me2NN(GeMe3)2, while no reaction was observed for the compounds Me2NN(SiMe3)2 and Me2NN(SiMe3)GeMe3, even when heat or basic catalysts were employed. Reaction products, carbamate and thiocarbamate derivatives, Me2NN(R)C(Y)YMMe3, were characterized on the basis molecular weight, i.r., p.m.r., and mass spectroscopy, and m.p. data. Ease of formation is discussed in terms of electronic and steric effects.

scholarly journals The Influence of Polymer Molecular Weight in Lamellar Gels Based on PEG-Lipids

1998 ◽  
Vol 75 (1) ◽  
pp. 272-293 ◽  
Author(s):  
Heidi E. Warriner ◽  
S.L. Keller ◽  
Stefan H.J. Idziak ◽  
Nelle L. Slack ◽  
Patrick Davidson ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Polymer Molecular Weight

Effects of drug and polymer molecular weight on drug release from PLGA-mPEG microspheres

2014 ◽  
Vol 132 (6) ◽  
pp. n/a-n/a ◽  
Author(s):  
Shuibin Feng ◽  
Lei Nie ◽  
Peng Zou ◽  
Jinping Suo
Keyword(s):  
Molecular Weight ◽  
Drug Release ◽  
Polymer Molecular Weight

Optimisation of diketopyrrolopyrrole:fullerene solar cell performance through control of polymer molecular weight and thermal annealing

2014 ◽  
Vol 2 (45) ◽  
pp. 19282-19289 ◽  
Author(s):  
Zhenggang Huang ◽  
Elisa Collado Fregoso ◽  
Stoichko Dimitrov ◽  
Pabitra Shakya Tuladhar ◽  
Ying Woan Soon ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Solar Cells ◽  
Solar Cell ◽  
Thermal Annealing ◽  
Bulk Heterojunction ◽  
Cell Performance ◽  
Polymer Molecular Weight ◽  
Solar Cell Performance ◽  
Heterojunction Solar Cells ◽  
Bulk Heterojunction Solar Cells

The performance of bulk heterojunction solar cells based on a novel donor polymer DPP-TT-T was optimised by tuning molecular weight and thermal annealing.

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