1,721,121 research outputs found
MECHANICAL AND COMPRESSION CHARACTERIZATION OF PELLETES PREPARED BY EXTRUSION-SPHERONIZATION
No full textPart 1 The first part concern the characterization of mechanical and compression properties of pellets prepared by extrusion-spheronization. Thirteen batches of pellets were prepared all in the same condition, using five materials (corn starch, α-lactose monohydrate, anhydrous dicalcium phosphate, peg 6000 and amidated pectin) plus microcrystalline cellulose as main binder, in fixed ratio, 75, 50 and 25% respect the cellulose amount. A further batch was prepared using only microcrystalline cellulose. A characterization program were carried out on the compression and mechanical properties of the starting materials, powder mixtures and pellets, the latter analysed either as single unit that during compression. Results showed as pellets compaction behaviour is strongly related to the properties of powder mixtures used for their preparation and it could be also derived from single components characteristics according with the ratio used. Diametrical compression tests and pellets images before and after such test enabled to link mixtures and pellets compaction behaviour, moreover these tests allowed to classify pellets as fragmenting and deforming. Despite the similar compaction mechanism mixtures and pellets behaved completely different in term of tablettability. A marked increase on surface area resulted crucial in order to obtain pellets tablets, as confirmed by the fragmenting batches results. All pellets classified as deforming seem suitable as core materials for the film coating application,in the preparation of multiparticulate controlled release tablets. They resist to the compaction process retaining their shape, so they represent good system in order the maintain the film integrity. All pellets classified as fragmenting pellets do not result useful as ''cushioning agents'' in multiparticulate controlled release tablets. Moreover the spheronization carried out on dense extrudate (as in this case) do not represent the best methodology for this purpose. Part 2 The second part, carried out at the school of pharmacy and chemistry, John Moore University (UK) under the supervision of Dr. M. Roberts, concerning the influence of hydro-ethanolic media on the aspirin release profiles from hypromellose matrices. Percent aspirin released increased with increasing levels of ethanol in the dissolution media, correlating with the drug's solubility, however,dose dumping of aspirin did not occur. An initial rapid release was observed in media comprising 40% ethanol. Release in these conditions was considered to be both erosion and diffusion-mediated, in contrast to the release in 0, 10, 20 and 30% ethanol media, where erosion-controlled release dominated. Image analysis of matrix swelling indicated a slower initial interaction between ethanol and hypromellose accounting for the initial rapid release. Cloud point studies suggested that ethanol retarded hydration of the polymer
Evaluation of dissolution kinetics of hydrophilic polymers by use of acoustic spectroscopy,
No full textThis paper seeks to demonstrate the feasibility of using a novel analytical technique, acoustic spectroscopy, to characterize the dissolution kinetics of hydrophilic polymers, in particular, three different model polysaccharides: lambda carrageenan, gellan gum, and xanthan gum. The influence of particle size and of analysis temperature (25 or 45 °C) was evaluated through the evolution over time of the microrheological acoustic parameters G′ and G′′. This new method was then compared with classical rheological analysis. To better compare acoustic spectroscopy and rheological analysis, the initial dissolution rate from the slope of the first part of the G′ or viscosity versus time curves was calculated. Both analytical techniques gave the same rank order of kinetics for the powder types and fractions examined; differences in absolute values were due to the fact that the two methods measured different parameters and had different stirring efficiencies. The rheological data obtained with both methods of analysis and their modelling confirmed that acoustic spectroscopy is an effective tool for monitoring and quantifying dissolution kinetics and hence affords a powerful technique for following over time a great number of physical changes occurring in a specific system
THE USE OF SOUND SPEED MEASUREMENTS IN THE EVALUATION OF POLYMERS MUCOADHESIVENESS
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HIGH RESOLUTION ULTRASONIC SPECTROSCOPY IN THE ANALYSIS OF POLOXAMERS BEHAVIOUR
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Modulation of the release kinetics of starch-based erodible matrix tablets by the use of a-amilase
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Colloidal soft matter as drug delivery system
No full textGrowing interest is being dedicated to soft matter because of its potential in
delivering any type of drugs. Since hydrophilic, lipophilic, small and big molecules can
be loaded into these colloidal systems and administered through the parenteral or
nonparenteral route, soft matter systems have been used to solve many biomedical and
pharmaceutical problems. In fact, they make possible to overcome difficulties in the
formulation and delivery of poorly water-soluble drug molecules, settle some stability
issues typical of biological drug molecules, design parenteral sustained release forms
and provide functionalized soft particles that are very effective in drug targeting. This
review deals with the important role that colloids play in the drug delivery and
targeting, with particular attention to the more currently used systems such as microemulsions,
organogels, liposomes, micelles, and dendrimers. Though significant progress
has been made in drug targeting, some challenges still remain. Further efforts will
be required to better understand the characteristics of targets and to discover new ones.
In-depth knowledge of the physico-chemical structure and properties of the systems
used for targeting is fundamental for understanding the mechanism of interaction with
the biological substrate and the consequent drug release
Rheological evaluation of Silicon/Carbopol hydrophilic gel systems as a vehicle for delivery of water insolubile drugs
Full text linkThe present study analyzed the thickening properties of Carbopol 974 and 971 in a 50:50 mixture of water/SilsenseTM A-21, a new cationic silicon miscible in any proportion with water. Samples were prepared by simply dispersing different Carbopol amounts (0.5-4%) at room temperature or at 70°C without neutralizing. Temperature sweep and time sweep analysis did not reveal significant structural changes at increasing temperature in the samples prepared following the first procedure. On the other hand systems obtained at 70°C possessed higher elastic character particularly at polymer concentration higher than 2% (w/v). Analysis of the G′ and G′′ vs frequency curves by using different fitting equations (linear fitting, power law) gave information about the viscoelastic properties of the systems. The fitting of the frequency spectra and the calculation of the relaxation times from the master curves outlined the structural differences within the samples prepared with the two different procedures, confirming stronger gel-like behaviour for the samples prepared by the heating procedure. High preparation temperature promoted the polymer-solvent interactions, aiding the solvation of Carbopol. Heating facilitated polymer-solvent and polymer-polymer interaction, giving rise to a better organised structure typical of gel-like systems. Furthermore this preparation method provided good stability properties as shown by the stress sweeps tests performed during the three months of storage. The interpretation of the rheological results was supported by statistical analysis. A design methodology (screening and optimisation) was also applied in order evaluate the influence on dynamic rheological moduli of several parameters (polymer type and concentration, preparation method, temperature of the tests). This last method showed the relevance of the interaction of two main factors: polymer concentration and preparation procedure. Thus, statistical analysis confirmed that temperature increased the polymer-solvent interaction and improved the viscoelastic properties of the systems, particularly when Carbopols were present in considerable amounts
Application of the experimental design on the rheological characterisation of Carbopol-Silsense A-21 systems
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PEGylated polylactide (PLA) and poly (lactic-co-glycolic acid) (PLGA) copolymers for the design of drug delivery systems
No full textBackground: PEGylated polylactide (PLA) and poly (lactic-co-glycolic acid) (PLGA) copolymers are biodegradable polyesters, widely employed in the last decades for the design of drug delivery systems such as polymeric hydrogels and nanocarriers (e.g. micelles and nanoparticles). The coupling with polyethylene glycol (PEG) offers some advantages with the respect to PLA and PLGA, including a higher hydrophilicity and a prolonged retention time for nanoparticulate systems, as well as the possibility of preparing thermoresponsive hydrogels. A large variety of pharmacologically active-compounds (small molecules, natural compounds or biomolecules such as proteins, peptides, oligonucleotides) has been formulated and delivered through PEGylated PLA or PLGA copolymers. Due to the high number of papers recently published about the use of these biodegradable copolymers in drug delivery, PEGylated PLA or PLGA copolymers are being still attractive. Their potential applications have been also broadened by the developing of ligand-functionalized copolymers, enabling an “active drug targeting” for nanoparticulate systems. Area covered: The present review summarizes the recent advances in drug delivery systems based on PEGylated PLA or PLGA copolymers, focusing on self-assembled micelles and thermoresponsive hydrogels as well as nanoparticles. A particular consideration has been given to functionalized PEGylated PLA/PLGA nanoparticles for active drug delivery. Expert opinion: Further advances in the design of PEGylated PLA/PLGA delivery systems will be beneficial for an improved drug release and targeting in the light of novel personalised therapeutic strategies. © 2019, The Korean Society of Pharmaceutical Sciences and Technology
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