A compound of the formula A-B-C, is provided, wherein: A is a first nucleic acid that specifically binds to an extracellular surface protein expressed by a cell of interest, B is an alkyl linker； and C is a second nucleic acid that hybridizes to a complementary nucleic acid. In some embodiments, the first nucleic acid is an aptamer. In some embodiments, the nucleic acid comprises an active compound, particularly cytotoxic nucleotides such as poly-FdUMP. Compositions and methods of using such compounds for treating and/or detecting cancer are also described.
