59 research outputs found
Factorial analysis of the influence of dissolution medium on drug release from carrageenan-diltiazem complexes
This research studied the influence of buffer composition, pH, and ionic strength on the release of diltiazem hydrochloride from a complex of the drug with lambda carrageenan. Two viscosity grades of carrageenan were also compared. A factorial analysis was used to evaluate the influence of individual variables and their interactions. Both the complex solubility, measured as the drug concentration in equilibrium with the solid complex, and the drug release rate from constant surface area were considered. The increase of ionic strength significantly increased complex solubility in all the buffer systems. A significant effect of polymer grade on complex solubility was evidenced only in phosphate buffer with a pH of 6.8, indicating lower solubility of the complex when higher polymer molecular weight was involved. In most cases, drug release rate decreased when high polymer grade was involved in the complex. Ionic strength did not always have a significant effect on drug release rate and was quantitatively less important than for solubility lonic strength especially affected the drug release profiles. At higher ionic strength drug release was no longer constant, but decreased with time, probably because of lower polymer solubility
Factorial analysis of the influence of dissolution medium on drug release from carrageenan-diltiazem complexes
Reversed-phase high-performance liquid chromatographic separation and partial structural characterization of chloroplast glyceraldehyde-3-p dehydrogenase
Design of novel biodegradable multi-channel systems for the treatment of peripheral nerve injuries
Electrospun pullulan-chitosan-hydroxyapatite nanofibers: random and aligned scaffolds in soft musculoskeletal tissues
On the employment of lambda carrageenan in a matrix system. III. Optimization of a lambda carrageenan-HPMC hydrophilic matrix
The lambda carrageenan/HPMC ratio in matrix tablets has been optimized in order to obtain pH-independent release profiles of chlorpheniramine maleate, a freely soluble drug. Release profiles in acidic (pH 1.2) and neutral (pH 6.8) media were fitted according to the Weibull and the power law models. Model independent parameters (t(50%) and the percentage of drug released after 2 h) were also calculated. The Weibull parameters were found suitable to describe the dependence of the release profiles on matrix composition. Preparation and testing of the optimized formulation showed linear and pH-independent release profiles lasting about 24 h, in good accordance with the values predicted by the optimization procedure. (C) 1998 Elsevier Science B.V
Development of flexible and mechanical strain resistant membrane as promising guide conduits for nerve repair
Complexation between the Antioxidant Pterostilbene and Derivatized Cyclodextrins in the Solid State and in Aqueous Solution
Inadequate aqueous solubilities of bioactive compounds hinder their ability to be developed for medicinal applications. The potent antioxidant pterostilbene (PTB) is a case in point. The aim of this study was to use a series of modified water-soluble cyclodextrins (CDs), namely, hydroxypropyl beta-CD (HP beta CD), dimethylated beta-CD (DIMEB), randomly methylated beta-CD (RAMEB), and sulfobutyl ether beta-CD sodium salt (SBECD) to prepare inclusion complexes of PTB via various solid, semi-solid, and solution-based treatments. Putative CD-PTB products generated by solid-state co-grinding, kneading, irradiation with microwaves, and the evaporative treatment of CD-PTB solutions were considered to have potential for future applications. Primary analytical methods for examining CD-PTB products included differential scanning calorimetry and Fourier transform infrared spectroscopy to detect the occurrence of binary complex formation. Phase solubility analysis was used to probe CD-PTB complexation in an aqueous solution. Complexation was evident in both the solid-state and in solution. Complex association constants (K-1:1) in an aqueous solution spanned the approximate range of 15,000 to 55,000 M-1; the values increased with the CDs in the order HP beta CD < DIMEB < RAMEB < SBECD. Significant PTB solubility enhancement factors were recorded at 100 mM CD concentrations, the most accurately determined values being in the range 700-fold to 1250-fold
Coated electrospun alginate-containing fibers as novel delivery systems for regenerative purposes
Barbara Vigani,1 Silvia Rossi,1 Giuseppina Sandri,1 Maria Cristina Bonferoni,1 Giulia Milanesi,1 Giovanna Bruni,2 Franca Ferrari1 1Department of Drug Sciences, University of Pavia, Pavia, Italy; 2Department of Chemistry, University of Pavia, Pavia, Italy Aim: The aim of the present work was to develop biodegradable alginate (ALG)-containing fibrous membranes intended for tissue repair, acting as both drug delivery systems and cell growth guidance. Methods: Membranes were prepared by electrospinning. Since ALG can be electrospun only when blended with other spinnable polymers, dextran (DEX) and polyethylene oxide (PEO) were investigated as process adjuvants. ALG/DEX mixtures, characterized by different rheological and conductivity properties, were prepared in phosphate buffer or deionized water; surfactants were added to modulate polymer solution surface tension. The Design of Experiments (DoE) approach (full factorial design) was used to investigate the role of polymer solution features (rheological properties, surface tension, and conductivity) on electrospun fiber morphology. A high viscosity at 1,000 s-1 (1.3–1.9 Pa.s) or a high pseudoplasticity index (≥1.7), combined with a low surface tension (30–32 mN/m) and a low conductivity (800–1,000 µS/cm), was responsible for the production of ALG/DEX homogeneous fibers. Such ranges were successfully employed for the preparation of ALG-containing fibers, using PEO, instead of DEX, as process adjuvant. ALG/DEX and ALG/PEO fibers were subsequently subjected to cross-linking/coating processes to make them slowly biodegradable in aqueous medium. In particular, ALG/PEO fibers were cross-linked and coated with CaCl2/chitosan solutions in water/ethanol mixtures. Due to DEX high content, ALG/DEX fibers were soaked in a polylactide-co-glycolide (PLGA) solution in ethyl acetate. Results: Both cross-linking and coating processes made fibers insoluble in physiological medium and produced an increase in their mechanical resistance, assessed by means of a tensile test. PLGA-coated ALG/DEX and chitosan-coated ALG/PEO fibers were biocompatible and able to support fibroblast adhesion. Conclusion: The DoE approach allowed to draw up guidelines useful for the preparation of homogeneous fibers, starting from mixtures of ALG and non-ionic polymers. Such fibers, upon coating, resulted to be good cell substrates, allowing cell adhesion and growth. Keywords: DoE approach, ALG-based fibers, rheological properties, conductivity, surface tension, chitosan, PLG
Spermidine-crosslinked gellan gum nanofibers for the treatment of nervous tissue injuries
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