Biomaterials, Drug Delivery and Bionanotechnology—The Research that Paved the Way: Professor Nicholas Peppas’ Research Over the Years

Abstract

Professor Nicholas A. Peppas was born in Athens, Greece in 1948. He graduated from the National Technical University Athens with a degree (Dipl. Eng.) in Chemical Engineering. He then moved to the Massachusetts Institute of Technology where he completed a doctoral degree (Sc.D.) in Chemical Engineering in 2 years. His graduate work was performed in the laboratory of Professor E.W. Merrill. He continued as a Postdoctoral Associate working with Professors C.K. Colton, K.A. Smith and R. Lees in the Arteriosclerosis Center of MIT, before he was appointed as an Assistant Professor of Chemical Engineering at Purdue University in 1976. He was promoted to Associate Professor in 1978 and Professor in 1982. From 1993 to 2002 he was the Showalter Distinguished Professor of Chemical and Biomedical Engineering at Purdue University. As of 2003, he is the Fletcher Stuckey Pratt Chair in Engineering with appointments in the Departments of Chemical Engineering, Biomedical Engineering and the College of Pharmacy at the University of Texas at Austin. Professor Peppas has received honorary doctorates from the Universities of Ghent, Parma and Athens. He is the author of 1100 publications, 38 patents, and 33 books, and is one of the most cited pharmaceutical scientists. He is a HighlyCited ® scientist in the Pharmacology and Engineering fields. He is a member of the Institute of Medicine (IOM) of the National Academy of Sciences, the National Academy of Engineering (NAE), the National Academy of France (Pharmacy) and the Academy of Medicine, Engineering and Science of Texas (TAMEST). The Peppas laboratory has made groundbreaking contributions to the advancement of polymer science. Specifically, polymerization reactions were a topic of research in the early years. Polymer network formation was investigated and kinetic analyses of polymerization and crosslinking reactions were performed. Polymer physics and transport phenomena in glassy polymers were studied, and the findings were applied to, among other fields, drug delivery applications. This was one of the first significant contributions to develop quantitative models that could be applied to the pharmaceutical sciences. Towards that goal, fundamental polymer research examined the laws that govern solute and penetrant diffusion through a polymer medium. Models were developed to express experimentally observed phenomena in polymer swelling, penetrant sorption and solute release. Prediction of the matrix dissolution based on physical and mathematical models was one step further towards controlled drug release. Furthermore, the interactions of polymers and biological tissues were studied and gave valuable new information on the bioadhesive properties of materials. Hydrogels are a class of crosslinked polymers that the Peppas laboratory contributed greatly to, both on the fundamental aspects of their preparation and characterization as well as their application as biomaterials. Due to their hydrophilic and biocompatible nature, hydrogels are now widely used by biomedical and pharmaceutical scientists. Dr. Peppas’ studies on the synthesis and characterization of poly(vinyl alcohol) hydrogels resulted among others in the highly cited Peppas–Merrill equation (1974), which can be used to calculate the number average molecular weight between crosslinks. Having identified the potential of hydrogels as drug delivery vehicles, parameters that optimize the release process were systematically determined, as for example the hydrogel mesh size. Hydrogels that swell in response to changes in the environment, such as pH or glucose concentration, have been another exciting topic of research in the Peppas laboratory. These intelligent hydrogels can be used as drug carriers which will release their load in a controlled manner upon even small changes in the