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Biomedical subjects

I Orienti

Publications and source records attributed to I Orienti.

At least 19 recordsLinked to original sources
PubMed1999

Complexation of ursodeoxycholic acid with beta-cyclodextrin-choline dichloride coprecipitate.

The inclusion complexes of ursodeoxycholic acid (UDCA) with beta-cyclodextrin (betaCD) coprecipitated with choline dichloride (CDC) or beta-cyclodextrin were investigated to evaluate the effect of the presence of choline for UDCA inclusion in betaCD. The inclusion complexes were investigated in solution by phase solubility diagrams and 1H NMR spectrometry and in solid state (kneading, freeze-drying, sealed heating and spray-drying) by DSC, SEM, HSM, XRD and IR spectroscopy. Stability constants were determined at pH 5.5 and 7.0 to simulate the environmental pH of the first intestinal tract and at different temperatures (25, 30 and 37 degrees C) to obtain the thermodynamic parameters of inclusion. Both betaCD-CDC and betaCD increased the water solubility of UDCA particularly betaCD-CDC. All complexes showed a high dissolution rate particularly the spray-dried complexes obtained in the presence of betaCD-CDC.

Calorimetry, Differential Scanning↗
PubMed1998

Controlled insulin release from chitosan microparticles.

This study deals with the production of chitosan microparticles containing insulin by interfacial crosslinkage of chitosan solubilized in the aqueous phase of a water/oil dispersion in the presence of ascorbyl palmitate. The use of ascorbyl palmitate as interfacial crosslinker is based on its amphiphilic properties allowing its disposition at the water/oil interface of the preparative dispersion, thus permitting covalent bond formation with the amino groups of chitosan when its oxidation to dehydroascorbyl palmitate takes place during microparticle preparation. This preparation method produced microparticles characterized by high loading levels of insulin, completely releasing the drug in about 80 h at an almost constant release rate as determined by spectrophotometric and spectrofluorimetric methods. In contrast, the replacement of ascorbyl palmitate by dehydroascorbyl palmitate provided microparticles incompletely releasing the incorporated drug and characterized by a non-constant release rate over time due to the higher lipophilicity of dehydroascorbyl palmitate which hinders its disposition at the water/oil interface and thus decreases the crosslinking efficiency and increases the lipophilicity of the microparticle surface. The efficiency of the spectrofluorimetric and spectrophotometric methods used for determination of the stability and release of the insulin from the chitosan microparticles is also discussed.

Ascorbic Acid↗
PubMed1998

Substituted poly(methyl vinyl ether-alt-maleic anhydride) for the release control and targeting of methotrexate.

Poly(methyl vinyl ether-alt-maleic anhydride) substituted with cholamine (CA), aminoethylcholamine (AECA), or aminooctylcholamine (AOCA) at different substitution degrees, were used for methotrexate (MTX) complexation. The solid complexes, isolated by precipitation from the preparative mixture, showed lower fractional releases at pH 7.4 than at 5.5. This was ascribed to the establishment of ionic interactions between the ionized carboxyls of both the polymer and the drug and the quaternary ammonium groups of the substituents (CA, AECA, AOCA) inducing polymer self-aggregation and thus complex stabilization. The fractional release in pH 7.4 decreases with the increase in the substitution degree until a minimum characteristic for each substituent analyzed is reached and then rises with the increase in substitution degree. The minimum release at pH 7.4 was observed in the presence of AECA at the degree of substitution corresponding to 0.35 mole of substituent per mole of dimer (methyl vinyl ethermaleic anhydride). None of the substituted polymers studied had any haemolytic effect, indicating good biocompatibility.

Animals↗
PubMed1991

Release of ketoprofen from dermal bases in presence of cyclodextrins: effect of the affinity constant determined in semisolid vehicles.

We describe a method to determine the affinity constant values between Ketoprofen and beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin in semisolid vehicles. The method is based on the diffusion of the drug, released from semisolid vehicles, through a lipidic non porous membrane. The affinity constants of Ketoprofen towards cyclodextrins as determined in semisolid media better represent the release of the drug from dermal bases than the corresponding values in aqueous systems.

Chemical Phenomena↗
PubMed1991

Chemical properties-dissolution relationship. IV. Behaviour in solution of the diclofenac/N-(2-hydroxyethyl) pyrrolidine salt (DHEP).

The behaviour in solution of the salt formed between diclofenac and N-(2-hydroxyethyl) pyrrolidine (DHEP) was examined. This salt is more soluble and dissolves more rapidly than sodium diclofenac and tends to give rise to supersaturated solutions, that only slowly evolve to equilibrium. Above 35 mM of DHEP, the solutions show unexpected solubilization ability towards sparingly soluble materials. The faster plasma level found, when DHEP is administered per os, can be associated to this weak detergency. These properties make DHEP a suitable pharmaceutical form to prepare extemporary solutions for short term analgesic therapy.

Diclofenac↗
PubMed1991

Diffusion of naproxen in presence of beta-cyclodextrin across a silicone rubber membrane.

The diffusion of Naproxen through a silicone rubber membrane has been studied for four different release systems: solution and suspension both of Naproxen and Naproxen beta-cyclodextrin coprecipitates. Differences in transport between the two forms indicate the existence of an interaction between the acid and beta-cyclodextrin in solution. Independence of the transport on pH in the case of the coprecipitate indicates rapid liberation of Naproxen from the complex prior to entering the membrane. Increase in the cumulative amount diffused for the suspension of Naproxen with increasing pH was interpreted as due to an increase in its solubility with increasing pH.

Cyclodextrins↗
PubMed1991

Controlled release of hydrocortisone acetate from dermal bases.

The effect of the complexation with beta-cyclodextrin, hydroxypropyl beta-cyclodextrin and polyvinylpyrrolidone on the diffusion kinetics of hydrocortisone acetate through a non porous lipidic membrane was analyzed starting from different dermal bases: a Carbopol gel and lanovaseline. A constant diffusive gradient was achieved; this suggests that the complexation equilibrium controls the diffusable form, according to its stability constant. The following sequence was observed for the cumulative amount diffused: hydrocortisone acetate greater than hydrocortisone acetate/polyvinylpyrrolidone greater than hydrocortisone acetate/hydroxypropyl beta-cyclodextrin greater than hydrocortisone acetate/beta-cyclodextrin. Such behaviour was analyzed in terms of the main physical chemical parameters of the systems examined.

Acrylic Resins↗
PubMed1989

Availability of NSAIDH beta-cyclodextrin inclusion complexes.

The diffusion of a series of non steroidal antiinflammatory drugs through a silicone rubber membrane has been studied from suspensions both of the free and beta-cyclodextrin complexes forms at different pH values of the medium. Higher diffusion rates of the complexed forms as compared with the free ones and a rate-limiting effect of the apparent stability constant in the diffusion of the complexes were observed.

Administration, Topical↗
PubMed1989

Diffusion of ketoprofen from coprecipitates through a non porous lipidic membrane.

The effect of inclusion with beta-cyclodextrin or hydroxypropyl beta-cyclodextrin on the diffusion kinetics of Ketoprofen through a non porous lipidic membrane was analyzed starting from different dermal bases: a Carbopol gel, o/w emulsion and a fatty ointment. A constant diffusive gradient was achieved with the included forms at each concentration of the active principle in the vehicle. This suggests that the complex controls the diffusable form, according to its stability constant. The following sequence was observed for the diffusion rate: Carbopol gel greater than o/w emulsion greater than fatty ointment appears to depend mainly on the membrane/vehicle partition coefficient.

Chemical Phenomena↗
PubMed1986

Dissolution and partition thermodynamic functions of some nonsteroidal anti-inflammatory drugs.

Solubility values of a selected group of nonsteroidal anti-inflammatory drugs have been determined in water and 1-octanol as a function of temperature. Thermodynamic functions of dissolution and partition have been calculated and discussed with respect to various physical parameters of each solute and the two solvents. The calculated solubility values show good agreement with the experimental values. The analysis of the experimental solubility values of these compounds in terms of solid-state contribution and solute-solvent interaction suggests the different importance of these parameters in promoting solubility of solid nonelectrolytes.

Anti-Inflammatory Agents↗
PubMedDate not supplied

Indomethacin loaded chitosan microspheres. Correlation between the erosion process and release kinetics.

The preparation of chitosan microspheres covalently linked with citric acid and loaded with indomethacin is described. The release kinetics correlated with the concentration of chitosan in the microsphere preparative mixture and the pH of the release medium. Deviations from Fickian to zero order kinetics were observed at higher concentrations of chitosan and at pH 7.4. The variations induced by these parameters on drug diffusion and solubility in the matrix undergoing erosion were analyzed.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMedDate not supplied

Chitosan microcapsules as controlled release systems for insulin.

This study analyses the use of chitosan for the production of surface crosslinked microparticulate systems containing insulin. The microcapsules were prepared by an innovative technique based on interfacial crosslinkage of different amounts of chitosan solubilized in the inner phase of a water/oil emulsion by means of ascorbyl palmitate. The correlation between the main formulation parameters and the functional properties of the microcapsules were analysed. Insulin is incorporated with high efficiency. The peptide release is constant for appreciable periods of time. The content of chitosan modulates the main physico-chemical properties of the matrix.

Biocompatible Materials↗
PubMedDate not supplied

Influence of physico-chemical parameters on the release kinetics of ketoprofen from Poly(HEMA) crosslinked microspheres.

This report analyses the release of Ketoprofen from Poly(HEMA) microspheres crosslinked with EGDMA at different crosslinking ratios and loaded by soaking in saturated solutions of the drug. Release appears to be influenced by the dissolution of Ketoprofen in the hydrogel and it is strictly correlated with the diffusibility of the drug in the gelled matrix. The release rate of the drug in the hydrogel rises with the increase in the diffusional conductance and the release kinetics approaches zero order particularly at the higher values of the diffusional conductance.

Cross-Linking Reagents↗