Diagnostic Radiology
College of Medicine
University of Kentucky
Phone:
(606) 257-5288 (W)
(606) 278-1093 (H)
Fax:
(606) 257-7585
E-Mail:
jay@pop.uky.edu
In our laboratory, we employ radioanalytical approaches to solve pharmaceutically related problems, and use pharmaceutical approaches to solve problems related to nuclear medicine and radiopharmaceuticals. Our current projects are:
1. Gamma Scintigraphy. This involves the labelling of pharmaceutical dosage forms with gamma-emitting radionuclides and monitoring their biodisposition with a gamma camera following administration to human volunteers.
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| A gamma camera is capable of acquiring images in a static or dynamic mode, and is interfaced with a computer for data storage and subsequent image analysis. The quantities of radioactivity administered to human subjects is 100-500 fold lower than those routinely administered to patients undergoing a diagnostic nuclear medicine procedure. All human scintigraphic studies are reviewed by the Institutional Review Board, the Radioactive Drug research Committee, and the Radiation Safety Committee. |
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| This frequently involves radiolabelling dosage forms using a neutron activation approach. A small amount of a carefully chosen stable isotope (e.g. samarium-152) is incorporated into the dosage form during its manufacture. This allows preparation of dosage forms under industrial scale conditions without exposing the formulator to ionizing radiation. The finished dosage form is then exposed to a neutron flux. |
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| The capture of neutrons by the stable isotope results in the formation of a radioactive isotope that will ultimately emit gamma rays that can be detected by the gamma camera. This procedure allows one to radiolabel dosage forms that cannot easily be labelled otherwise, e.g. polymer-coated controlled-release dosage forms. |
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| Here is an example of a coated dosge form that was designed to release the active ingredient in the large intestines for the topical treatment of colitis. This time-lapse scintiphoto shows the intact tablet leaving the stomach and moving across the duodenum. |
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| Four-to-five hours later, this dosage form has entered the ascending colon and has disintegrated releasing its contents demostrating that the dosage form performed as it was designed to. The segments of the ascending colon can be seen clearly. |
2. Protein Purification by Foam Fractionation. Foam fractionation is a separation process based on the selective adsorption of a surface active species to a gas-liquid interface. We are currently exploring the potential of foam fractionation as a low-cost, high-volume protein purification technique. Gamma scintigraphy is being employed to acquire data to be used in the development of a mathematical model that can be used to determine the effect of column parameters on protein separation and enrichment.
 | In this series of scintiphotos, Bovine Serum Albumin was radiolabelled with Indium-111 and foamed. The labelled BSA can be seen to rise up the column and into a collection vessel. The colors in the image are indicative of the BSA concentration which can be quantified at any level in the column. |
 | In these scintiphotos, the enzyme carbonic anhydrase was labelled with Indium-111 and added to a low-concentration BSA solution. Under conditions in which BSA will foam, it can be observed that the carbonic anhydrase only moves a short distance up the column and ultimately settles back into the originial feed solution. |
 | At higher BSA concentrations, much of the labelled carbonic anhydrase moves up the column. In this case, most of the liquid volume from the feed solution was recovered in the recovery vessel resulting in a low enrichment of BSA. The activity of carbonic anhydrse was only marginally affected by the foaming process. |
3. Intrapulmonary Drug Delivery in Fluorocarbon Solvents.
Liquid ventilation is a ventilatory support technique in which a chemically inert high molecular weight liquid perfluorocarbon (such as perflubron) is saturated with oxygen and is instilled directly into the tracheobronchial tree. Being twice as dense as water and having a surface tension only about 25% of water, the perfluorocarbon spreads rapidly through every airway of the lung, displacing most of the edema fluid present. The perfluorocarbon provides the supply of oxygen and the sink for respired carbon dioxide necessary to support life. The fact that the liquid perfluorocarbon rapidly spread to all portions of the lung presents a unique advantage for the local delivery of drugs directly to the airways and alveoli. In the case of respiratory distress, the delivery of vasodilators, anti-inflammatory agents and antibiotics could become clinically useful. It is our hypothesis that therapeutic agents can be directly administered to the lung airways and alveoli in a manner independent of intrapulmonary vascular shunting. This can be accomplished by dissolving or dispersing these agents in fluorocarbon solvents by forming inverse micelles with the aid of specifically designed co-surfactants. Dr. Paul Bummer is the principal investigator on this project. This work is being carried out by a graduate student Tom Williams and an undergraduate student Danette Conley, and is being generously supported by our colleague at Pharmacia & Upjohn, Dr. Dennis Stalker.
4. X-Ray Fluorescence
X-ray fluorescence (XRF) is an emission spectroscopic technique which can be used for both quantitative and qualitative elemental analysis. In XRF, the atoms in a sample are excited to emit their characteristic x-rays by exposing the sample to a source of low energy ionizing radiation. The energy of the emitted x-ray identifies the element and the number of x-rays of a given energy is a measure of the concentration of that element in the sample matrix. We have employed radioisotope-induced XRF as a simple, noninvasive technique for monitoring percutaneous absorption in vivo of topically applied compounds.
 | For measuring the percutaneous absorption of iodine-containing compounds by XRF, we employ a shielded annular Americium-241 source. The 60 keV photons emitted by this source interacts with a samarium foil producing secondary x-rays which then induce iodine x-rays in the applied compound. These iodine x-rays are quantified by a solid state detector which is interfaced with a photomultiplier tube and a multichannel analyzer. |
 | The use of secondary x-rays results in a low absorbed radiation dose to the site of administration, permitting its use in human volunteers. Unlike in vivo transdermal absorption measurements that involve the administration of radiolabelled compounds, the XRF technique does not result in systemic radiation exposure. |
5. Scintillation Proximity Assay.
Radioimmunoassay is a competitive binding assay in which a radiolabelled antigen competes with an unlabelled antigen for a limited number of binding sites on antibodies. By binding these antibodies onto the pore surface of a membrane in which fluors have been entrapped within the membrane matrix, only those labelled antigens bound to the membrane are in close enough proximity to the fluors to induce scintillations. Thus, the step involving the separation of bound and unbound radio-antigen can be eliminated. This scintillation proximity approach has been applied to a one-step radioimmunoassay utilizing microporous polymeric membranes. The results of this work were recognized by the Society of Nuclear Medicine by the presentation of the Berson-Yalow Award. We have also applied the scintillation proximity approach to the assay of radioactive carbon dioxide using a sol-gel matrix. SPA projects were carried by graduate students Robert K> Mansfield who is currently at Allergan, Inc., and Lisa J. Ulrich who is currently at the University of Florida, and with the collaboration of Dr. Dibakar Bhattacharyya of the University of Kentucky Department of Chemical and Materials Engineering.
C.D. Mattingly, R.K. Mansfield, D. Bhattacharyya and M. Jay, Membrane-based scintillation proximity assays. I. Detection and quantification of 14CO2. J. Membrane Sci., 98:275-280 (1995).
J.A. Hughes and M. Jay, Preparation of [11C]-formaldehye using a hollow fiber membrane bioreactor. Nucl. Med. Biol., 22:105-109 (1995).
D.S. MacLean, J.D. Robertson, M. Jay, and D.J. Stalker, Noninvasive measurement of protein release from subcutaneous depo formulations in vivo using x-ray fluorescence. J. Controlled Release. 34:167-173 (1995).
R.K. Mansfield, D. Bhattacharyya, N.G. Hartman and M. Jay. Scintillation proximity radioimmunoassay with microporous membranes. Appl. Radiat. Isotop. 47:323-328 (1996).
R.K. Mansfield and M. Jay, Porous polymeric membranes for one-step radioimmunoassay. J. Nuclear Med. 34:126P (1993) (Berson-Yalow Award).