Biomedical subjects

A Gèze

Publications and source records attributed to A Gèze.

4 recordsLinked to original sources

PubMed2004

Long-term shelf stability of amphiphilic beta-cyclodextrin nanosphere suspensions monitored by dynamic light scattering and cryo-transmission electron microscopy.

Amphiphilic beta-cyclodextrins (betaCDa) were synthesized by statistically grafting hexanoyl carbon chains on the secondary hydroxyl functions of the betaCD glucopyranosyl units. The obtained derivative was used to prepare submicronic colloidal nanosphere suspensions using a nano-precipitation method. The fresh suspensions contained particles with a diameter ranging from 60-100 nm. Taking into account that the physical stability of colloidal systems remains one of the major problems which can restrict their use in pharmaceutical particulate carrier formulations, the long-term stability of the aqueous nano-dispersions was investigated. Two complementary characterization methods, namely dynamic light scattering and cryo-transmission electron microscopy, were used to control the size distribution and morphology of the nanospheres during storage. The zeta potential was measured as well. An unexpected good physical stability of the suspensions after 3 year storage at room temperature was observed. This behaviour appears to be related to the small size and structural organization of the nanoparticles. The mean diameters determined from light scattering experiments are consistent with those measured from electron micrographs. The slight difference between the values obtained by both methods is discussed.

Chemical Precipitation↗

PubMed2001

[Effect of cyclodextrins on fungal degradation of fluorene].

The purpose of this study was to improve the bioavailability of fluorene (PAH) by the use of complexing agents, cyclodextrins. The biodegradation tests were performed in liquid medium batches; fluorene was quantified by HPLC. Experimental results showed the enhancement of fluorene degradation by Penicillium italicum and Phanerochaete chrysosporium in the presence of branched cyclodextrins.

Biological Availability↗

PubMed1999

Development of 5-iodo-2'-deoxyuridine milling process to reduce initial burst release from PLGA microparticles.

The aim of this study was to prepare 5-iodo-2'-deoxyuridine (IdUrd) loaded poly(d,l-lactide-co-glycolide) (PLGA) microspheres with a reduced initial burst in the in vitro release profile, by modifying the drug grinding conditions. IdUrd particle size reduction has been performed using spray-drying or ball milling. Spray-drying significantly reduced drug particle size with a change of the initial crystalline form to an amorphous one and led to a high initial burst. Conversely, ball milling did not affect the initial IdUrd crystallinity. Therefore, the grinding process was optimized to emphasize the initial burst reduction. A first step allowed us to set qualitative parameters such as ball number (7) and cooling with liquid nitrogen to obtain a mean size reduction and a narrow distribution. In a second step, three parameters including milling speed, drug amount and time were studied by a response surface analysis. The interrelationship between drug amount and milling speed was the most significant factor. To reduce particle size it should be necessary to use a moderate speed associated with a sufficient drug amount (400-500 mg). IdUrd release from microparticles prepared by the o/w emulsion/extraction solvent evaporation process with the lowest crystalline particle size (15.3 microns) was studied. Burst effect could be reduced significantly. Concerning the first phase of drug release, the burst was 8.7% for 15.3 microns compared to 19% for 19.5 microns milled drug particles.

Chemistry, Pharmaceutical↗

PubMedDate not supplied

PLGA microsphere bioburden evaluation for radiosterilization dose selection.

The aim of this study was to determine the bioburden of PLGA microspheres produced by the solvent emulsion/extraction process as a means of determining an appropriate gamma-irradiation dose for sterilization. Bioburden was evaluated on the basis of ISO specifications. The analysis of initial microbial contamination was performed on blank microspheres, prepared by a non-aseptic laboratory scale process. A mean bioburden of 36.04 CFU (colony forming units)/110 mg microspheres was determined. Most of the detected germs originated from human commensal flora. According to the ISO dose-selection method, a gamma-irradiation dose of 19.6 kGy was found sufficient to ensure a sterility level of 10(-6). The effect of the selected irradiation dose on both the molecular weight of the polymer and the kinetics of 5-fluorouracil drug release from the microspheres was compared to the European Pharmacopeia recommended irradiation dose (25 kGy). This 20% reduced dose showed a lower extent of molecular weight reduction of PLGA and a better control of 5-FU release from microparticles. This can be related to reduce polymer radiation damage.

Fluorouracil↗