Vacuum evaporation of pharmaceuticalmolecules for the creation of medicallyactive nanostructures with enhancedactivities
Nanostructuring of pharmaceutical active film systems offers many promising applications like precise control of dissolution and release kinetics, enhanced activities, flexibility in terms of surface coatings, integration into implants, designing appropriate scaffolds or even integrating them into microelectronic chips etc. for different desired applications. In general such kind of structuring is difficult to achieve by wet chemistry due to unintentional mixing of chemical solvents used during drug formulation. One of the aims of this dissertation was primarily addressing vacuum evaporation as a solvent free method to effect improvements in drug solubility and drug efficiency to better administration and finally enhance patient survival.. Thermal evaporation of pharmaceutical molecules can be utilized where drugs as powders or crystalline materials are directly formulated into desired nano or micro structures and shapes on preferred substrates. Thermal evaporation is based on the principle of physical vapor deposition. Drugs as well as the drug carrier materials were heated up in a crucible to their melting temperature. The whole procedure was carried out in a vacuum chamber. High-vacuum (10-5-10-7 mbar) guaranteed a long mean free path of the evaporated particles on their way to the substrate as well as the avoidance of contaminations. In the framework of the thesis., the performed deposition experiments of more than 30 pharmaceuticals and their structural analyses suggest that by thermal evaporation technique most of pharmaceutical substances (>80%) can be micro-nanostructured in different desired complex forms. The observed features of enhanced solubility and biological activities, controlled release kinetics of synthesized drugs seem to be a very powerful alternative for the traditional physical structuring of pharmaceutical drug molecules. The most important aspects of thermal evaporation technique are: solvent-free, precise control of size, possibility of fabricating multilayer/hybrid, and free choice of substrates. Another promising possibility could be to selectively coat the integrated silicon chips to design a pharmaceutical field effect transistor (PFET) for different applications ranging from new generations of organic electronic devices to biomedical engineering. In a layer by layer geometry, they can be used as increasing the activity of drug, control the drug release and combination therapy.