| Posted: May 19, 2006 |
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Attaching biomolecules to carbon nanotubes
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(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.
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Before their paper, titled "Protein immobilization on carbon nanotubes via a two-step process of diimide-activated amidation", published in issue 1, 2004 of Journal of Materials Chemistry not a lot of work was done on attaching proteins to CNTs. In the research that was done, proteins were either noncovalently bonded on CNTs or were attached through a harsh process, so the final connection is either very loose or the survival chance of attached protein is very small.
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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:
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"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."
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Schematic view of diimide-activated attachement process (Source: Rensselaer Polytechnic Institute)
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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.
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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."
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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.
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TEM Image of PAMAM-MWNT Heterostructure (Source: Rensselaer Polytechnic Institute)
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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.
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By Michael Berger, Copyright 2006 Nanowerk LLC. All rights reserved.
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