Characterization of and biomolecule immobilization on the biocompatible multi-walled carbon nanotubes generated by functionalization with polyamidoamine dendrimers.

Polyamidoamine (PAMAM) dendrimers were covalently tethered onto the surface of multi-walled carbon nanotubes (MWCNTs). The morphology and dispersive properties of the MWCNT-PAMAM hybrids were characterized and the peripheral functional groups were identified. Cytotoxicity to human osteosarcoma MG-63 cells, and protein and DNA immobilization ability of the hybrids were evaluated in detail. The dendrimers were present on the surface of MWCNTs in high density. The MWCNT-PAMAM hybrids exhibited good dispersibility and stability in aqueous solution. We showed that the hybrids are biocompatible, with no obvious cytotoxicity at concentration <25 microgmL(-1) over 24h. They possess excellent biomolecule-immobilization ability (bovine serum albumin and 5'-Fam-CAAggTCgTgTAAAggTCAg-3' were used as models). The functionalization of MWCNTs with PAMAM dendrimers improved the biomolecule-immobilization ability 70-fold and simultaneously decreased the cellular toxicity by about 30%. It is expected that the MWCNT-PAMAM hybrids will find promising applications in biosensors and biomolecule delivery systems in gene or protein therapy.