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Education:

• Ph.D. Pharmaceutics

Overview

Melgardt received his B.Pharm. degree (1986), M.Sc. (1988) and Ph.D. (1993) degrees in pharmaceutics, and Diploma in Tertiary Education (D.T.E., 1996) from the North-West University in Potchefstroom, South Africa. After serving on the faculties of North-West University and the University of Louisiana at Monroe and a sabbatical year at the University of Iowa, he joined the Wisconsin faculty in 2005.

His research focuses on determining the pharmaceutical science involved in developing an understanding of the pharmaceutics, engineering, and materials sciences principles underlying drug delivery technologies and applying these principles to the design, development, and manufacture of improved of drug delivery systems. Within this program, there are two projects. The first project is directed towards the measurement, manipulation, and optimization of the physicochemical properties of drugs and excipients, both in the pure state and in drug delivery systems. Research is aimed at yielding a total profile of any solid in question, whether it is an active drug, an excipient, or blend of these because we found that the development of this profile is a requirement for the successful design and ultimate manufacture of better pharmaceutical dosage forms. Based on information obtained from studies performed in the first project, research proceed by studying and manipulating formulation factors that depends on the solid state properties of drugs. This is done to optimize drug delivery by changing the macro, micro, and nano-particulate properties of drugs and excipients, for example drugs used in the treatment of communicable diseases (rifampicin, niclosamide, chloramphenicol palmitate, triclosan, etc.) and cardiovascular disorders (nifedipine, furosemide, etc.). Formulation changes include using complexes between drugs and cyclodextrins, calixarenes, dendrimers, or encapsulation of the drug in micro and nano sized matrixes. These matrixes are either naturally occurring compounds, such as halloysites and zeolites, or formed by nano-assembly of shells around drug particles. Nano-assembly involves the layer-by-layer self-assembly of shells performed by alternate electrostatic adsorption of oppositely charged polyelectrolytes. Novel micro-particulate systems for controlled drug release, or that can be used as carrier particles for loading drugs during simple powder mixing or solvent deposit processes, are also prepared using spherical agglomeration and solvent evaporation techniques.

Lab News:
Mel de Villiers has been selected to serve on the Editorial Board of Current Drug Discovery Technologies. He has also been appointed as an Associate Editor for the Journal of Biomedical Nanotechnology. Research from his lab describing the effect of polyamidoamine dendrimers on the cytotoxicity of paclitaxel in prostate cancer cells was also featured on the cover page of the March 2008 edition of this journal.

Highlighted Publications:

• AI, H., JONES, S.A., DE VILLIERS, M.M. & LVOV, Y.M. 2003. Nano-encapsulation of furosemide microcrystals for controlled drug release. Journal of controlled release, 86:59-68.
• CAIRA, M.R., ROBBERTSE, Y., BERGH, J.J., SONG, M. & DE VILLIERS, M.M. 2003. Structural characterization, physicochemical properties, and thermal stability of three crystal forms of nifedipine. Journal of pharmaceutical sciences, 92(12):2519-2533.
• DE VILLIERS, M.M., VAN EEDEN, C.M., LIEBENBERG, W., SONG, M., KOLLING, W.M. & CAIRA, M.R. 2004. Structural characterization, physicochemical properties, suspension stability and adsorption properties of four amitraz crystal forms. Journal of agricultural and food chemistry, 53(24):7374-7381.
• DEVARAKONDA, B., HILL, R.A. & DE VILLIERS, M.M. 2004. The effect of PAMAM dendrimer generation size and surface functional group on the aqueous solubility of nifedipine. International journal of pharmaceutics, 284(1-2):133-140.
• YANG, W. & DE VILLIERS, M.M. 2004. The solubilization of the poorly water-soluble drug nifedipine by water-soluble 4-sulphonic calix[n]arenes. European journal of pharmaceutics and biopharmaceutics, 58(3):629-636.
• PARGAONKAR, N., LVOV, Y.M., LI, N., STEENEKAMP, J.H. & DE VILLIERS, M.M. 2005. Controlled release of dexamethasone from microcapsules produced by polyelectrolyte layer-by-layer nanoassembly. Pharmaceutical research, 22(5):826-835.
• ZAHR, A.S., DE VILLIERS, M.M. & PISHKO, M.V. 2005. Encapsulation of drug nanoparticles in self-assembled macromolecular nanoshells. Langmuir, 21(1): 403-410.
• KRISHNA, G., LU, Z., DE VILLIERS, M.M. & LVOV, Y.M. 2006. Composite phospholipid - calcium carbonate microparticles: influence of anionic phospholipids on the crystallization of calcium carbonate. The Journal of Physical Chemistry B., 10(6): 2471-2474.
• LI, N., KOMMIREDDY, D.S., LVOV, Y., LIEBENBERG, W., TIEDT, L.R. & DE VILLIERS, M.M. 2006. Nanoparticle multilayers: surface modification of photosensitive drug microparticles for increased stability and in vitro bioavailability. Journal of nanoscience and nanotechnology, 6(9-10): 3252-3260.
• WU, T., SUN, Y., LI, N., DE VILLIERS, M.M. & YU, L. 2007. Inhibiting surface crystallization of amorphous indomethacin by nanocoating. Langmuir, 23(9): 5148-5153.