Vitamin B 12 (cyanocobalamin) is a vital nutrient characterized by very low bioavailability. Owing to their extremely high proliferation rates, tumor cells show increased demand for nutrients in comparison with healthy ones, including the greater uptake of vitamin B 12 . This avidity for cyanocobalamin can thus be exploited for the site-specific delivery of drugs directly into tumor cells by conjugation of vitamin B 12 (carrier)

Glucose is a key source of energy and an essential nutrient for cell growth. Rapidly dividing cancer cells are well-known to require more nutrients and energy than normal ones to sustain their higher proliferation rates, and glucose is no exception. Therefore, the biomolecules involved in the promotion/regulation of the glycolytic flux may be regarded as potential targets for tackling tumor progression. Among all, glucose transporters (GLUTs), devoted to the recognition and cellular internalization of glucose, are largely overexpressed in tumors, thus indicating glycolysis as the major anaerobic glucose metabolism. Accordingly, such increased demand of glucose by fast-proliferating cancer cells makes it very attractive to selectively target tumor sites. In particular, tailored glucose-like substrates can be conjugated to chemotherapeutics (including metal-containing anticancer agents) so as to attain the site-specific delivery of drugs into the affected tissues. Progress in the development of metal-based glycoconjugates are here summarized and discussed.

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