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Biomedical subjects

M E Carlotti

Publications and source records attributed to M E Carlotti.

At least 19 recordsLinked to original sources
PubMed2004

Solid lipid micro-particles carrying insulin formed by solvent-in-water emulsion-diffusion technique.

The study aimed to produce solid lipid insulin-loaded micro-particles by the solvent-in-water emulsion-diffusion technique, using isobutyric acid as solvent phase, glyceryl monostearate or cetyl palmitate as lipid, soya lecithin and taurodeoxycholate as emulsifiers. Isobutyric acid, a partially water-miscible solvent with low toxicity, was used due to its high insulin-solubilization capacity. Solid lipid micro-particles of spherical shape were prepared by simple dilution of the emulsion with water. To increase the lipid load the process was conducted at 50 degrees C, and in order to reach sub-micron size, a high-shear homogeniser was used. Insulin encapsulation efficiency was about 80%. Analysis of microsphere content after processing showed that insulin did not undergo any chemical modification within the micro-particles. The in vitro release of insulin from the micro-particles was very low, and an initial burst effect of 20% of the dose was observed. After treatment of the solid lipid micro-particles with pepsin solution, an insulin loss of about 24% of the total englobed insulin was observed. The solid lipid micro-particles appear to have interesting possibilities as delivery systems for oral administration of insulin.

Animals↗
PubMed2002

Vitamin A and vitamin A palmitate stability over time and under UVA and UVB radiation.

Vitamin A and vitamin A palmitate photostability were tested in different media. Ethanol and octyl octanoate solutions of these two vitamins, as such and with the addition of sunscreens (3,4 methylbenzilidencanfora, butyl methoxy dibenzoylmethane and octyl methoxycinnamate) or beta-carotene and butylated hydroxy toluene, were analysed spectrophotometrically after UVB or UVA irradiation. An O/W fluid emulsion with 0.5% w/w of retinyl palmitate, with and without butylated hydroxy toluene, was prepared. The oil containing the vitamin was extracted with HCl and aluminium sulfate and analysed spectrophotometrically after UVB or UVA irradiation. The fluid emulsion containing retinyl palmitate with and without butylated hydroxy toluene was stored at different temperatures and analysed every week spectrophotometrically for a month. Of the sunscreens tested butyl methoxy dibenzoylmethane showed the strongest protective action towards vitamin A and vitamin A palmitate, whereas beta-carotene did not protect either vitamin. Butylated hydroxy toluene inhibited the photodegradation of both vitamins dissolved in octyl octanoate, suggesting that oxygen may be involved in their degradation. O/W emulsion promoted slightly the degradation of vitamin A ester. Butylated hydroxy toluene protected retinyl palmitate from degradation induced by light and heat.

Butylated Hydroxytoluene↗
PubMed1999

Investigation of the phase behaviour of systems containing lecithin and 2-acyl lysolecithin derivatives.

A series of modified phospholipids (m-PC) possessing different acyl chains in position 2, from butanoyl to hexadecanoyl, were prepared by partial synthesis from soybean lysolecithin. They were used with soybean lecithin to construct phase diagrams containing ethanol as cosolvent, water and medium chain triglycerides (MCT) or isopropyl myristate (IPM) as oils. The weight ratios lecithin:m-PC and surfactants:ethanol were kept constant at 1:1. The results indicate that the m-PCs have a strong effect on the microemulsion (L) and liquid crystalline (LC) domains in the water-rich/oil-poor part of the phase diagrams, although all diagrams correspond to a single lecithin:m-PC ratio. On decreasing the acyl chain length, and thus increasing the hydrophilicity of the surfactant, there was a corresponding increase in the L area, which moved towards the aqueous corner of the phase diagrams. The LC phase was detected only in the presence of the hexadecanoyl derivative for the systems containing MCT, and it was not detected only in the presence of the butanoyl derivative for the systems containing IPM. The use of a second hydrophilic surfactant to adjust the packing properties of the lecithin-alcohol systems, and/or to increase the fluidity of the surfactant film, increased the region of existence of the isotropic systems. This may be of importance in the formulation of drug delivery systems, especially those which are diluted by biological fluids upon administration.

Chemistry, Pharmaceutical↗
PubMed1999

On the stability of ascorbic acid in emulsified systems for topical and cosmetic use.

Several O/W microemulsions, O/W and W/O emulsions and a W/O/W multiple emulsion were prepared using non-ionic, non-ethoxylated, skin compatible emulsifiers. Ascorbic acid (vitamin C) was added to the emulsified systems and its stability against oxidation was studied at 45.0 degrees C in aerobic conditions and compared with that in aqueous solutions at different pH values. All emulsified systems provided protection to ascorbic acid, as its degradation rate, which increased with increasing pH, was slower in emulsified systems than in aqueous solutions. The highest protection of ascorbic acid was when it was dissolved in the inner aqueous phase of the W/O/W multiple emulsion, both at 45 and at 20 degrees C for long storage. A pseudo first-order mechanism was hypothesised for ascorbic acid degradation in the experimental conditions for as long as abundant dissolved oxygen was present.

Administration, Topical↗
PubMed1994

Inhibition of lipoperoxidation of linoleic acid by five antioxidants of different lipophilicity.

The efficacy of oxidation inhibition of five natural and synthetic antioxidants (BHT, BHA, nordihydroguaiaretic acid (NDGA), quercetin and rutin) was studied in O/W emulsions. Linoleic acid was used as a reference molecule; the reaction was initiated by an azo-compound. The kAH characterizing the reaction of the antioxidant with the peroxyl radical decreases in the following order: kAH(BHA) > kAH(BHT) > kAH(NDGA) > kAH(quercetin) > kAH(rutin).

Antioxidants↗
PubMed1992

Timolol in lipospheres.

Lipospheres carrying timolol (1) were obtained from microemulsions. They had lecithin, palmitic and decanoic acids as the main constituents. The sizes were between 300 and 400 nm and the amount of 1 incorporated varied from 2.7 to 4.8% according to the microemulsion used. Compound 1 was present in the lipospheres mainly as ion pairs in order to increase its lipophilicity. The difference found in the incorporation was principally due to the different lipophilicity of the ion pairs of 1.

Chemistry, Pharmaceutical↗
PubMed1984

Behavior of ATP toward phenothiazine drugs.

The tricyclic amines promazine, promethazine, chlorpromazine, triflupromazine, and trifluperazine form solid ion pairs with ATP in a 1:2 molar ratio. There is a good correlation between the measured Ksp and the apparent diffusion constants of the ion pairs with the critical micelle concentration (CMC) of the corresponding phenothiazines. Solid ion pairs are solubilized by phenothiazine micelles; the binding constants of ATP to drug micelles are calculated from solubility data at 25 degrees C and can be related to the CMC of the phenothiazines.

Adenosine Triphosphate↗
PubMed1983

Binding of Phenothiazines to bovine hemoglobin.

Phenothiazines with bovine hemoglobin give solid complexes in phosphate buffer; this is due to the presence of ion-pairs between phenothiazines and phosphates. Using diluted solutions the number of sites available on each protein molecule and the intrinsic binding constants are determinated; the number of sites, in solutions and in solid complexes, is about the same for each drug, but different for the various phenothiazines.

Animals↗
PubMed1982

Behaviour of hematoporphyrin and protoporphyrin with antidepressant drugs.

Complexation between oppositely charged antidepressant drugs and porphyrin derivatives was investigated by NMR spectroscopy. The solid complexes obtained are soluble in antidepressant aggregates and a good fit was found between the values of CMC of the drugs and the values of the binding constants of porphyrins with antidepressant micelles.

Antidepressive Agents↗
PubMed1979

Kinetics of dopamine oxidation by dialkylaminoalkylphenothiazine cation radicals.

The kinetics of dopamine oxidatinon dialkylaminoalkylphenothiazine cation radicals (with two- or three-carbon side chains) were investigated. The two-carbon side-chain derivatives have reaction rates higher than the three-carbon ones. For chlorpromazine and promazine, extrapolation of pH 1-6 data shows that reaction rates become very fast at physiological pH.

Chemical Phenomena↗