Vitamin B12 Bioconjugates as Therapeutics

The ability of vitamins such as vitamin B12 to act as drug carriers for transporting orally administered pharmaceuticals to cells has been recognized for some time. Only small, neutral, water-soluble molecules can pass across biological membranes to any degree by passive diffusion. Due to the large size of vitamins, these important biomolecules are therefore typically associated with active transport mechanisms for absorption and cellular uptake. This is especially important for vitamin B12, given the very small amounts that are present in most foods. Utilizing vitamin B12 bioconjugates for the transportation of drugs has been shown to have applications in the uptake of both peptides and proteins administered orally. Cobalamin-diethylene-triaminepentaacetate (DTPA)-metal conjugates have been identified as potential diagnostic imaging agents for tumors (111In, 99Tc) and MRI (57Gd) contrast-enhancing agents. Fluorescent B12 conjugates also show much promise in diagnostic imaging. Importantly, the chloroambucil-cobalamin bioconjugate has shown considerable potential for the treatment of leukemia.

C&EN CoverRight: C&E News Science & Technology Concentrate, June 30, 2008, featuring our work on vitamin B12 bioconjugates.

We prepared the first vitamin B12 bioconjugates which could potentially be active, orally administered pharmaceuticals for the treatment of diabetes. This work was featured in C&E News (Science & Technology Concentrate, June 30, 2008). We have more recently become interested in preparing fluorescent B12 derivatives, in collaboration with Assoc. Professor Soumitra Basu at Kent State University, OH, USA.

Schlenk-cuvette used for UV-visible photo spectrometric measurements of air and moisture sensitive compounds in our laboratories.