In the present work, porous gelatin scaffolds were prepared by cryogenic treatment of a chemically cross-linked gelatin hydrogel, followed by removal of the ice crystals formed through lyophilization. This technique often leads to porous gels with a less porous skin. A simple method has been developed to solve this problem. The present study demonstrates that the hydrogel pore size decreased with an increasing gelatin concentration and with an increasing cooling rate of the gelatin hydrogel. Variation of the cryogenic parameters applied also enabled us to develop scaffolds with different pore morphologies (spherical versus transversal channel-like pores). In our opinion, this is the first paper in which temperature gradients during controlled cryogenic treatment were applied to induce a pore size gradient in gelatin hydrogels. With a newly designed cryo-unit, temperature gradients of 10 and 30 degrees C were implemented during the freezing step, resulting in scaffolds with average pore diameters of, respectively, +/-116 and +/-330 microm. In both cases, the porosity and pore size decreased gradually through the scaffolds. Pore size and structure analysis of the matrices was accomplished through a combination of microcomputed tomography using different software packages (microCTanalySIS and Octopus), scanning electron microscopy analysis, and helium pycnometry.

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Abstract. The objective of this study was to assess the quality of antihypertensive drugs and to investigate the influence of tropical storage conditions. Drug content and in vitro dissolution tests were performed on 10 test formulations (from Rwanda) and 6 reference formulations (from Belgium or France) after purchase and after 6-month storage under long-term (25 ± 2°C and 60 ± 5% relative humidity [RH]) and accelerated (40 ± 2°C and 75 ± 5% RH) testing conditions. Twenty percent of test formulations were of substandard content at the time of purchase. After 6 months at accelerated testing conditions, 7 of 10 test formulations were substandard in content and 8 were substandard for the combined criteria of drug content and dissolution, whereas no reference drug became substandard. This study shows that, apart from some drugs being already substandard from purchase, accelerated testing conditions (simulating tropical climate) have deleterious effects on the majority of antihypertensive drug formulations found in the Rwandan market.

The technique described in this research work is suitable for the production of porous pellets. Drug loading via immersion the pellets in a drug solution and supercritical fluid impregnation resulted in a drug deposition in the entire pellet in contrast to fluid bed layering where drugs were only deposed on the pellet surface.