Peter M. Ihnat

Synthesis and Solution Properties of Deferoxamine Amides

The poor membrane permeability and oral bioavailability of the iron chelating agent deferoxamine (DFO) mesylate result from the low octanol/water partition coefficient and high aqueous solubility. With the ultimate aim to improve biomembrane permeability while retaining the iron-binding ability of DFO, a series of more lipophilic amides were prepared by reacting the terminal primary amino group with fatty and aromatic acid chlorides or anhydrides. Octanol/water partition coefficients and equilibrium solubilities of these analogs in solvents, chosen to delineate physicochemical interactions, were determined as a function of temperature. Solid-state properties were evaluated by calorimetry. All DFO amide derivatives had higher melting points, indicating that derivatives formed strong intermolecular interactions in the solid phase. Formamidation of the primary amine of deferoxamine resulted in a 200-fold increase in the octanol/water partition coefficient and reduced aqueous solubility at least 2000-fold compared with the parent molecule. The partition coefficient increased and aqueous solubility decreased 2-fold with the addition of each methylene group in the homologous series of aliphatic amides. Solubilities of the derivatives in water-saturated octanol and hexane showed irregular profiles as a function of increasing aliphatic chain length that were attributed to intermolecular packing in the solid state. The temperature dependence of the partition coefficients was interpreted to indicate that interfacial transfer of the deferoxamine amides was, in part, affected by an apparent diminished ability to form energetically favorable interactions in the water-saturated organic phase.

The Use of Field Emission Scanning Electron Microscopy to Assess Recombinant Adenovirus Stability

A field emission scanning electron microscopy (FESEM) method was developed to assess the stability of a recombinant adenovirus (rAd). This method was designed to simultaneously sort, count, and size the total number of rAd viral species observed within an image field. To test the method, a preparation of p53 transgene-expressing recombinant adenovirus (rAd/p53) was incubated at 37 degrees C and the viral particles were evaluated by number, structure, and degree of aggregation as a function of time. Transmission electron microscopy (TEM) was also used to obtain ultrastructural detail. In addition, the infectious activity of the incubated rAd/p53 samples was determined using flow cytometry. FESEM image-analysis revealed that incubation at 37 degrees C resulted in a time-dependent decrease in the total number of detectable single rAd/p53 virus particles and an increase in apparent aggregates composed of more than three adenovirus particles. There was also an observed decrease in both the diameter and perimeter of the single rAd/p53 viral particles. TEM further revealed the accumulation of damaged single particles with time at 37 degrees C. The results of this study demonstrate that FESEM, coupled with sophisticated image analysis, may be an important tool in quantifying the distribution of aggregated species and assessing the overall stability of rAd samples.

Use of an Automated Image Processing Program to Quantify Recombinant Adenovirus Particles

Electron microscopy has a pivotal role as an analytical tool in pharmaceutical research. However, digital image data have proven to be too large for efficient quantitative analysis. We describe here the development and application of an automated image processing (AIP) program that rapidly quantifies shape measurements of recombinant adenovirus (rAd) obtained from digitized field emission scanning electron microscope (FESEM) images. The program was written using the macro-recording features within Image-Pro Plus software. The macro program, which is linked to a Microsoft Excel spreadsheet, consists of a series of subroutines designed to automatically measure rAd vector objects from the FESEM images. The application and utility of this macro program has enabled us to rapidly and efficiently analyze very large data sets of rAd samples while minimizing operator time.