To protect against nuclease digestion, or single-strand binding protein interactions, oligonucleotides for targeted delivery into intracellular systems must be stable. To accomplish this, we have developed single-walled carbon nanotubes as a carrier for single-stranded DNA probe delivery. This has resulted in superior biostability for intracellular application and, hence, has achieved the desired protective attributes, which are particularly important when DNA probes are used for intracellular measurements. Specifically, when bound to single-walled carbon nanotubes, DNA probes are protected from enzymatic cleavage and interference from nucleic acid binding proteins. Moreover, and equally important, our study shows that a single-walled carbon nanotube-modified DNA probe, which targets a specific mRNA inside living cells, has increased self-delivery capability and intracellular biostability when compared to free DNA probes. Therefore, this new conjugate provides significant advantages for basic genomic studies in which DNA probes are used to monitor intracellular levels of molecules.