Integrated geophysical investigations at Šapinuva, a Hittite city in central Anatolia, Turkey

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HYSTERESIS OF CONTACT ANGLE. DYNAMIC WETTABILITY STUDIES OF COLLAGEN AND DOXYCYCLINE POROUS MATRICES CROSSLINKED WITH TANNIC ACID

Collagen porous matrices are promising delivery systems which offer the possibility to obtain a local optimized drug release. One important prerequisite in understanding the drug dissolution profile is an adequate monitoring of the porous collagen matrices surface properties and surface wettability degree. In this study we have considered direct measurements of the contact angle and hysteresis of contact angle (dynamic contact angle) for some collagen matrices with doxycycline, cross-linked with tannic acid, in order to better describe the wettability properties of these drug release systems. The matrices were obtained by freeze-drying of collagen gels (the release support) which have embedded doxycycline as model drug. These systems were prepared at pH=3.8, and crosslinked with different concentrations of tannic acid (4%, 5%, 10%, respectively 20%). We also took into account in the study an uncrosslinked matrix (without tannic acid) as control sample. A KSV Instrument CAM 101 equipped with a digital camera and the pendant drop method were used for contact angle and surface properties experiments. The liquid (water) is imbibed into the porous matrices producing the contact angle decrease in time. The Young-Laplace equation was applied and the contact angle hysteresis was evaluated (difference between the maximum and the minimum contact angle values) to characterize the surface wettability and hydrophobicity