(90b) Smart Drug Delivery Systems That Learn from Nature

Since nitroglycerine transdermal patches were introduced on the United States market in 1982 for the treatment of angina pectoris, controlled drug release systems have been widely used to treat a variety of diseases. The system design is in the form of pills, capsules, transdermal patches, implanted drug delivery systems, intravitreal inserts, subcutaneous implants, and injectables. These preparations take the forms of particles endowed with controlled release (CR) functions, films formed after evenly mixing drug powders into polymer bases, or implantable rods or disks that are made by the advanced processing of particles. When the transdermal therapeutic systems started to use clinically about a quarter century ago, the purpose of CR technology was the constant-rate, long-term release of active agents. In other words, a major objective of CR technologies was to develop dosage forms which, with one dose, release active agents at a constant rate effective over a long period of time. There were two major underlying reasons. First, the optimum tissues concentration and release characteristics of drug molecules were not fully understood for treating diseases, and second, owing to the large individual differences in pharmacokinetics (ADME: absorption, distribution, metabolism, and elimination) within the body, the accurate control of concentrations in blood and tissue did not make sense. Of course even today, although long-term constant-release systems are effective in gaining patient compliance and treating many diseases, timed or pulsatile drug release systems are increasingly necessary. Attention is focused especially on pulsatile delivery that can cope with the time dependent state of a disease and undesired side effects, prevent drug tolerance, and set dose intermissions. The active agents in pharmaceuticals are bioinformation molecules that control bodily functions by acting as signal or false-signal molecules. Generally these are produced in the body and are released for the maximum effect and without waste. Recently research has started to learn about not only drugs (bioinformation molecules) like these, but also how plants and insects economically and effectively use their bioinformation molecules. Knowledge turned up in this research is then used in CR and drug delivery technologies. This science is called biomimicry, and considered as a valuable new scientific field in the 21st, or biotech, century. [1] For example, the chemical reactions, and the processes of release and movement of informational molecules within organisms, are the most efficient functions achieved by organisms through the long course of evolution. Biomimicry, or the imitation of these biological functions, will likely play an essential role in developing sustainable CR technologies. However, it is certainly not easy to correctly understand the ingenious functions of organisms and exactly mimic them. Hence at this stage of research the main purpose of biomimicry would be to develop novel CR and drug delivery systems with the inspiration gained in the course of learning from nature.[2] For that reason this paper explores CR processes for bioinformation molecules as related to drug delivery and the biomimicry concept. I examine biomimicry in CR technologies in relation to three items: (1) mimicking elements, (2) mimicking mechanisms, and (3) utilizing mechanisms. Mimicking elements means controlling drug release and delivery by using the active agents produced when necessary in the body, which has been the main stream of pharmaceutical research and development to data. Mimicking mechanisms means understanding the mechanisms that use bioinformation molecules, and using them in drug delivery technologies, thus making them similar to what nature does. Utilizing mechanisms, on the other hand, means using biological functions as is to develop highly economical CR technologies. This paper shows how biomimicry, or learning from nature, plays an important role in developing novel drug delivery systems than can time-control release and delivery rates. Further, examples are used to explain in general the three approaches for developing the DDS's that learn from nature. The time-controlled release of bioinformation molecules is an efficient and economical process acquired by organisms over the long course of evolution, and organisms take ingenious advantage of both their internal and external environmental conditions, which change from moment to moment. When we learn from living functions and develop new DDS, we must keep in mind not only the functions of individual organisms, but also the roles of organisms as systems and the ?natural systems? that comprise organisms and their surrounding environments. Living creatures make smart use of natural systems to achieve their efficient and economical release and delivery systems for bioinformation molecule. Accordingly, only when we study biomimicry by taking natural systems into account can we minimize the risk inherent in mimicking only certain facets of intricate natural functions.