1,721,093 research outputs found
Effect of Hydration on Physicochemical Properties of End-Capped PLGA
Full text linkThe objective of this study was to assess the physicochemical effects of hydrating a hydrophobic end-capped poly(lactide-coglycolide)(PLGA)polymerintheliquidandvaporstate.PLGARG503polymerwasincubatedat37∘Cin0.5%polyvinylalcohol (PVA)solutionandat90%RH.Sampleswerewithdrawnatpredeterminedintervalsandchangestopolymerpropertieslikeglass transition temperature (Tg), moisture uptake, molecular weight change, and % acid number were determined using differential scanningcalorimetry,KarlFishertitrimetry,gelpermeationchromatography,andacidbasetitrimetry,respectively.Studyresults showed that Tg was depressed instantaneously upon hydration, indicating that bulk water acted as a plasticizer of hydrophobic end-cappedPLGA.Tg valuesdecreasedtolevelsbelowtheincubationtemperaturewhenhydratedin0.5%PVAsolutionbutnotin 90%RH.ThedropinTg exhibitedalinearrelationship(2 > 0.99)totheamountofwateruptakebythepolymer;highermoisture uptakewasnotedwithliquidwater.RemovalofmoisturefromthepolymermatrixresultedinrecoveryofTg,onlyuptoaperiod of14days.Presenceofwaterinliquidorvaporformcausedareductioninmolecularweightofthepolymerandacorresponding increasein%acidnumberoverthedurationofthestudy
Microencapsulation of a hydrophilic model molecule through vibration nozzle and emulsion phase inversion technologies
No full textIntroduction: The goal of the present work was to evaluate and discuss vibration nozzle microencapsulation (VNM) technology combined to lyophilization, for the microencapsulation of a hydrophilic model molecule into a hydrophilic polymer. Materials and methods: Fluorescein-loaded alginate microparticles prepared by VNM and emulsion phase inversion microencapsulation (EPIM) were lyophilized. Morphology, particle size distribution, lyophilized microspheres stability upon rehydration, drug loading and in vitro release were evaluated. Results and discussion: Well-formed microspheres were obtained by the VNM technique, with higher yields of production (93.3-100%) and smaller particle size (d50138.10-158.00) than the EPIM microspheres. Rehydration upon lyophilization occurred in 30 min maintaining microsphere physical integrity. Fluorescein release was always faster from the microspheres obtained by VNM (364 h) than from those obtained by EPIM (504 h).
Conclusion:
The results suggest that VNM is a simple, easy to be scaled-up process suitable for the microencapsulation hydrophilic drugs
Enhanced Degradation of Lactide-co-Glycolide Polymer with Basic Nucleophilic Drugs
No full textThe 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 system
Polymer Scaffolds for Bone Tissue Regeneration
No full textThe term “tissue engineering” refers to methods and techniques used to improve the regeneration of human cells and tissues, including the manipulation of natural and synthetic materials which provide both the structural integrity and the biochemical information to young cells when they are growing into a specific kind of tissue.
This chapter deals with the application of tissue engineering to bone tissue regeneration and is focused to the polymer structures studied and used as temporary templates to promote bone reconstruction. After a brief introduction about the general principle of regenerative medicine, the scaffold design criteria and their applications, atten-tion will be focused to scaffold for bones. A scaffold classification is reported based on the type of constituent polymers and a detailed discussion is provided about these materials highlighting advantages and drawbacks for each of them. Moreover, polymer scaffold prepa-ration and characterization techniques are described and discussed with some examples. Finally clinical aspects and criticisms are also presented to show the state of art of the topic
Effect of porogen on the physico-chemical properties and degradation performance of PLGA scaffolds
No full textThe aim of the study was to examine the relationship between the structural features of PLGA 3-D
scaffolds and their degradation performances. PLGA 3-D scaffolds were fabricated by solvent casting and
particulate leaching using salt and sucrose particles as porogen and they were characterized in terms of
structure, physico-chemical and mechanical properties. The in vitro degradation study was performed at
37 C in PBS for 28 days and it included the determination of Mw, Mn, PI, water uptake, mass loss and pH
changes of the degradation buffer. It was found that the preparation method scaffolds, in particular the
choice of the porogen type and was responsible for the three-dimensional structure (pore size, porosity,
apparent density and, mechanical properties) of the scaffold and for physico-chemical PLGA polymer
modifications (polymer degradation reactions, polymer chain rearrangement, Tg changes). Scaffolds with
high porosity (83.8e89.4%) and an interconnected network were obtained
Effect of water on the physical and chemical properties of end-capped poly(d,l-lactide-co-glycolide)
Full text linkA Short Term Quality Control Tool for Biodegradable Microspheres
No full textAccelerated in vitro release testing methodology has been developed as an indicator of product performance to be used as a discriminatory quality control (QC) technique for the release of clinical and commercial batches of biodegradable microspheres. While product performance of biodegradable microspheres can be verified by in vivo and/or in vitro experiments, such evaluation can be particularly challenging because of slow polymer degradation, resulting in extended study times, labor, and expense. Three batches of Leuprolide poly(lactic-co-glycolic acid) (PLGA) microspheres having varying morphology (process variants having different particle size and specific surface area) were manufactured by the solvent extraction/evaporation technique. Tests involving in vitro release, polymer degradation and hydration of the microspheres were performed on the three batches at 55°C. In vitro peptide release at 55°C was analyzed using a previously derived modification of the Weibull function termed the modified Weibull equation (MWE). Experimental observations and data analysis confirm excellent reproducibility studies within and between batches of the microsphere formulations demonstrating the predictability of the accelerated experiments at 55°C. The accelerated test method was also successfully able to distinguish the in vitro product performance between the three batches having varying morphology (process variants), indicating that it is a suitable QC tool to discriminate product or process variants in clinical or commercial batches of microspheres. Additionally, data analysis utilized the MWE to further quantify the differences obtained from the accelerated in vitro product performance test between process variants, thereby enhancing the discriminatory power of the accelerated methodology at 55°C. © 2014 American Association of Pharmaceutical Scientists
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