Closed Crystalline Tubes as a Container System

Hollow crystalline glucose anhydrate needles are produced based on a technique to produce hollow crystal needles by phase transformation of solvate crystals into non-solvates. The fascinating characteristic of the glucose anhydrate needles is the possibility of closing them by a simple drying process. This creates great potential for future applications as a container system, e.g., for pharmaceutical substances. The hollowness of the needles has already been proven, but the filling of the needles has not been investigated. Due to the lack of a direct method to demonstrate the possibility of filling the needles, two indirect methods are presented to demonstrate a successful technique to enclose substances in these needles. On the one hand, the filling is proven by fluorescence microscopy of glucose anhydrate needles with enclosed rhodamine 6G. Here it is possible to visualize the fluorescence dye by observation of the broken needles. On the other hand, the concentration of included ibuprofen is examined by the means of UV spectroscopic measurements. A significant concentration of the enclosed drug is detected following the extraction out of the needle interior.