S. Avramiotis

Trypsin In Lecithin Based w/o Microemulsions. Fluorescence and Enzyme Activity Studies

Lecithin based microemulsions were used as model systems for enzymic studies. The phase behavior of the system: purified soya bean lecithin/propan-1-ol/isooctane/water was examined. It was found that the ability of the system to solubilize water was strongly affected by the lecithin and alcohol concentrations. Trypsin was entrapped in lecithin microemulsion systems of different composition and tested for proteolytic activity on the hydrolysis of lysine-p-nitroanilide (LNA). The kinetic constants were determined and in most cases the ratio kcat/Km was higher than that observed in aqueous solution. The optimum enzyme activity was found at pH 9 for the system formulated with 5% w/w lecithin in isooctane, while increasing wo, where wo = [H2o]/[Lecithin], the enzyme activity followed a bell-shaped pattern with a maximum at wo= 20. The stability of trypsin in microemulsions was higher in the low water containing systems. Using the fluorescence quenching technique it was found that the system compartmentalizatio...

EPR STUDIES OF PROTEOLYTIC ENZYMES IN MICROEMULSIONS

Abstract EPR spectra of spin-labelled α-chymotrypsin and trypsin were recorded in both lecithin and AOT microemulsion systems. The active site serine residue of α-chymotrypsin and trypsin has been spin-labelled by 3-(4-nitrophenoxy carbonyl)–PROXYL. The mobility of the spin-labelled enzymes was affected by the wo values in both microemulsion systems. When spin-labelled trypsin was solubilized in the lecithin systems, the mobility increased as wo (wo=[H2O]/[AOT]) was increased, whereas when spin-labelled α-chymotrypsin was solubilized in the same system the opposite effect was observed. The deacylation rates of spin-labelled trypsin and α-chymotrypsin were determined in both microemulsion systems.

Tacrolimus loaded biocompatible lecithin-based microemulsions with improved skin penetration: Structure characterization and in vitro/in vivo performances

In order to improve skin penetration of tacrolimus we aimed to develop potentially non-irritant, lecithin-based microemulsions containing ethanol, isopropanol and/or propylene glycol as cosurfactants, varying caprylic/capric triglycerides and propylene glycol monocaprylate as oil phase. The influence of excipients on the size of microemulsion region in pseudo-ternary phase diagrams and their ability to form different types of microemulsions was evaluated. The comprehensive physicochemical characterization of microemulsions and the evaluation of their structure was performed, while the localization of tacrolimus in microemulsions was further investigated using electron paramagnetic resonance spectroscopy. Moreover, stability studies proved no change in tacrolimus content during one year of storage at room temperature. In addition, in vivo skin performance indicated no skin irritation potential of blank microemulsions, whereas in vitro release testing using Franz diffusion cells showed superior release rate of tacrolimus from microemulsions (0.98±0.10 and 0.92±0.11μg/cm2/h for two bicontinuous and 1.00±0.24μg/cm2/h for oil-in-water microemulsion) compared to referent Protopic ointment (0.15±0.08μg/cm2/h). Furthermore, ex vivo penetration assessed through porcine ear skin using tape stripping, confirmed superiority of two microemulsions related to the reference, implying developed microemulsions as promising carriers for dermal delivery of tacrolimus.

The effect of proteolytic enzymes on hair follicles of transgenic mice expressing the lac Z-protein in cells of the bulge region

To study the effects of proteolytic enzymes on mice hair follicles, particularly on cells of the bulge area regarded as follicle stem cells.