Ronald S. Harland

Drug/Polymer Matrix Swelling and Dissolution

The swelling and dissolution behavior of pharmaceutical systems containing a drug and a polymer can be analyzed by a mathematical model which predicts the drug released and the gel layer thickness as a function of time. It is possible to approximate the values of several of the physicochemical parameters of this model in order to obtain an order-of-magnitude analysis of the tablet dissolution process. Selected experimental results of tablet dissolution and drug release are analyzed and conclusions are made about the importance of the drug and polymer content and solubility in the release behavior.

A model of dissolution-controlled, diffusional drug release from non-swellable polymeric microspheres

Abstract A new model was developed to account for the kinetics of drug release from porous, non-swellable polymeric microparticles in the case where both drug dissolution and diffusion mechanisms control the overall release process. The model incorporates a linear first-order dissolution term and the transient Fickian diffusion equation, and is solved for perfect sink and surface-dependent boundary conditions. Long-term limiting solutions indicate that after an initial time-dependent period of release, the release rate becomes independent of time. Numerical solutions are provided which indicate the effects of particle size, solute diffusion coefficient and solute dissolution rate on the release kinetics.

Solute diffusion in swollen membranes VII. Diffusion in semicrystalline networks

A model is developed to express the solute diffusion coefficient through semicrystalline polymeric networks. The crystallites create impermeable diffusional barriers around the amorphous regions. Solute diffusion is determined by applying a transport model to the amorphous phase and incorporating the crosslinked polymer structure characteristics. This model is tested with theophylline and vitamin B12 permeation experiments through semicrystalline poly(vinyl alcohol) membranes prepared by annealing of amorphous PVA membranes. The degree of crystallinity varies between 23.1 % and 40.5 % on a dry basis. The solute diffusion coefficients correlate well with various parameters of the model.

Hydrophilic/hydrophobic, block and graft copolymeric hydrogels: synthesis, characterization, and solute partition and penetration

Abstract A series of hydrophilic/hydrophobic copolymers has been synthesized and characterized for possible applications in drug delivery. Such systems were prepared by random, graft or block copolymerization of various monomers, followed by selective hydrolysis. The copolymer composition was investigated using NMR spectroscopy, whereas their molecular weight distribution was determined by gel permeation chromatography. Thermodynamic and physical properties, such as transition temperatures and degrees of swelling were measured to elucidate the effect of phase separation on the formed network structure. Microdomain formations, balance of chemical properties, and network characteristics affected the partitioning and transport of theophylline and myoglobin in these swollen networks. Finally, the non-linear network swelling, selective drug partitioning and control of drug permeation through and release from copolymer membranes were correlated to the presence of hydrophobic and hydrophilic microdomains in the copolymer networks for a selected number of copolymers studied.

Chemical Engineering at Purdue University

In the open fields of Indiana, roughly equidistant between Gary and Indianapolis and built on the then navigable Wabash river, lay in the middle 19th century a small town of 4,000 inhabitants, the town of Lafayette. A trade center for northwest Indiana, the town was inhabited mostly by German and Anglosaxon farmers and traders. As a result of the 1862 Morrill Act, the General Assembly of Indiana voted in 1865 to establish a land-grant university (1). The fierce competition between various towns continued for four years with Monroe, Marion and Tippecanoe counties becoming the three finalists. Finally, the balance tilted in favor of Lafayette, mainly because of the then generous contribution of

Unit Processes Against Unit Operations: The Educational Fights of the Thirties

150,000 by John Purdue,

Solute diffusion in swollen membranes

50,000 by the Tippecanoe County and 100 acres of land from local residents. Thus, in the fourth and final ballot in the Indiana House, Tippecanoe county received 52 votes, with 17 voting for Monroe and 8 for Marion county. In the Senate questions arose and the representatives of Bloomington (Monroe county) and Indianapolis (Marion county) “stigmatized as selfish vanity for Mr. Purdue to ask that the institution be named Purdue University (1).” On May 4, 1869 Purdue’s offer was accepted with 32 to 10 votes in the Senate and 76 to 19 in the House.

On the accurate experimental determination of drug diffusion coefficients in polymers

Chemical Engineering started as a discipline concerned with the education of engineers who would work in chemical plants. Yet, in the early days of the development of this field, industrial chemistry was the most “acceptable” method of education of students.