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Posted: May 19, 2006
Attaching biomolecules to carbon nanotubes
(Nanowerk Spotlight) Among the many potential biology-related applications proposed for carbon nanotubes (CNTs) are high-sensitivity biosensors and bio-fuel cells. In order to create the synergy between the biomolecules and CNTs required to realize these applications, biomolecules, such as proteins and DNAs, must be connected to the CNTs. A useful, simple and universal method to attach biomolecules onto carbon nanotubes with covalent bonding was developed by researchers at Rensselaer Polytechnic Institute.
The work done by the Rensselaer scientists provides a universal approach of forming bio-nano materials which have numerous applications. Kuiyang Jiang, first author of the paper, explained to Nanowerk the three core findings of their research:
"We developed an attachment process operated at room temperature and in buffer solution, which could greatly increases the survival possibility of attached proteins;
We developed a covalent process, which provides a robust connection between protein and carbon nanotubes; and
we developed a two-step attachment process, in which the interconnection of COOH and NH2 groups in/between different proteins are greatly inhibited. No protein aggregation means high protein efficiency in any applications."
Schematic view of diimide-activated attachement process (Source: Rensselaer Polytechnic Institute)
The covalently bonding of molecules to the CNTs was done in a two-step process, carried out at room temperature in buffer solutions and was accomplished in a short time, which maximizes the survival rate of biomolecules.
Jiang explains the two-step process: "carboxylic acid groups are first converted to active esters via diimide-activation, and then the active esters are reacted with the amine groups on proteins without the presence of diimide. This two-step process avoids intermolecular conjugation and guarantees the uniform attachment on carbon nanotubes."
Follow-up work to this initial research was done by attaching PAMAM dendrimer onto CNTs through a similar approach as the one described above. This approach provides a universal and efficient method to attach nano-entities with NH2 groups to carbon nanotubes at ambient conditions.
TEM Image of PAMAM-MWNT Heterostructure (Source: Rensselaer Polytechnic Institute)
This work, titled "Covalent Bonding of Nano-entities with NH2 Groups onto Multi-walled Carbon Nanotubes" was presented at the 2004 MRS Fall meeting in Boston.