Factors influencing activation and delivery of DNA-binding agents from an alginate carrier system

Methods for delivery of genes and agents which bind to nucleic acids, and thereby modify the expression of genes, are areas of intensive research. The focus of the present study is the initial development and characterization of an enteric delivery system for DNA-binding drugs. Several fluorescent probes were screened as to their suitability for analysis of DNA in alginate beads. A UV transilluminator was used to identify SYBR I and SYBR II as two functional fluorescent probes for DNA within intact alginate beads. A methyl green-DNA complex was found to be useful for monitoring the dissolution of alginate beads and release of an intact drug-DNA carrier system. After dissolution of alginate beads containing DNA, addition of DNase I to the dissolution fluid resulted in the complete hydrolysis of DNA. This is a necessary condition for the release of a DNA binding drug from the DNA carrier system in that hydrolysis of the carrier by enteric nucleases must occur in the presence of alginate. Once released from a DNA carrier, protein binding plays an important role in the disposition of these agents. A phosphorothioate oligonucleotide complexed to a methidium-spermine affinity gel was used as a tool to study oligonucleotide binding proteins . Bovine serum albumin was used as a prototype binding protein and was found to elute as a single peak from the oligonucleotide affinity column. Elution was accomplished with a sodium chloride gradient. This approach may be useful for characterization of other oligonucleotide binding proteins.