Role of the deposition temperature on the self-assembly of the non-planar molecule benzene-1,3,5-triphosphonic acid (BTP) at the liquid-solid interface.

Benzene-1,3,5-triphosphonic acid (BTP) contains three non-planar phosphonic acid groups which enable three-dimensional hydrogen bonding. Because of these versatile 3D functional groups, BTP is an interesting intermediate to design both 2D and 3D supramolecular hydrogen-bonded architectures and organic-inorganic hybrid frameworks. However, the adsorption of BTP has surprisingly not been the subject of scanning tunneling microscopy (STM) investigations so far. Here a STM study of the adsorption pattern of BTP as obtained from deposition out of a solution in undecanol on an interface to highly-oriented pyrolytic graphite (HOPG) is presented. Furthermore, the influence of the substrate temperature during the deposition from solution on the self-assembly is investigated. High-resolution STM images reveal that the BTB molecules usually form various structures by co-adsorption with undecanol and that the BTP molecules as parts of self-assembled aggregates adsorb with their benzene ring planes tilted with respect to the substrate plane. The specific supramolecular pattern and the 2D packing density of BTP can be precisely tuned by adjusting the initial substrate temperature during deposition. The experimental results are compared to corresponding model structures obtained from semi-empirical simulations and explained by the influence of temperature on the concentration at the solution-solid interface and the kinetics of the self-assembly process. Based on these results, the control of the deposition substrate temperature has been proven to be a versatile tool to control the polymorphism of molecular patterns deposited out of solutions.

3D screen printing - An innovative technology for large-scale manufacturing of pharmaceutical dosage forms.

Three-dimensional (3D) screen printing was used to fabricate oral dosage forms of different geometry and size. The paste required as starting material for the 3D screen printing process was designed for delayed release and contained the model drug paracetamol (acetaminophen). A prototype screen printing unit was used to fabricate different tablets in a single production process. The resulting tablets were produced with three different sizes and designed geometries (disk, donut, cuboid, oval and grid). Investigation of size and mass of the individual tablets demonstrated high uniformity within the various groups of tablets. Further characterization of their physical properties, such as breaking force and friability, yielded results comparing favorably to conventionally produced tablets. Finally, drug release tests in artificial gastric media showed paracetamol release to depend on the surface-area-to-volume ratio. In conclusion, the study shows the potential of 3D screen printing to fabricate more complex oral dosage forms in the setting of mass production with high reproducibility.