title: Conjugation of insulin onto the sidewalls of single-walled carbon nanotubes through functionalization and diimide-activated amidation.
abstract: OBJECTIVE
  The high aspect ratio of carbon nanotubes (CNTs) allows the attachment of compounds that enhance the functionality of the drug vehicle. Considering this, use of CNTs as a multifunctional insulin carrier may be an interesting prospect to explore.
  
  
  METHODS
  The carboxylic acid groups were functionalized on the sidewalls of single-walled CNTs (SWCNTs) followed by diimidation to form amide bonds with the amine groups of the insulin.
  
  
  RESULTS
  Scanning transmission electron microscopy and transmission electron microscopy establish clear conjugation of insulin onto the surface of nanotube sidewalls. The incorporation of insulin further increased the solubility of SWCNTs in biological solution for the tested period of 5 months. Bicinchoninic acid assay confirms that 0.42 mg of insulin could be attached to every 1 mg of carboxylated SWCNTs.
  
  
  CONCLUSIONS
  With the successful conjugation of insulin to SWCNTs, it opens up the potential use of SWCNTs as an insulin carrier which in need of further biological studies.
authors.affiliation: Manufacturing and Industrial Processes Research Division, Faculty of Engineering, University of Nottingham Malaysia Campus, Semenyih, Selangor, Malaysia.
authors.forename: Chee Meng
authors.initials: CM
authors.lastname: Ng
authors.affiliation: Faculty of Science, School of Biosciences, University of Nottingham Malaysia Campus, Semenyih, Selangor, Malaysia.
authors.forename: Hwei-San
authors.initials: HS
authors.lastname: Loh
authors.affiliation: Manufacturing and Industrial Processes Research Division, Faculty of Engineering, University of Nottingham Malaysia Campus, Semenyih, Selangor, Malaysia.
authors.forename: Kasturi
authors.initials: K
authors.lastname: Muthoosamy
authors.affiliation: Faculty of Science and Defence Technology, National Defence University of Malaysia, Kuala Lumpur, Malaysia.
authors.forename: Nanthini
authors.initials: N
authors.lastname: Sridewi
authors.affiliation: Manufacturing and Industrial Processes Research Division, Faculty of Engineering, University of Nottingham Malaysia Campus, Semenyih, Selangor, Malaysia.
authors.forename: Sivakumar
authors.initials: S
authors.lastname: Manickam
mesh_terms: D000577:Amides / Q000737:chemistry*; D001681:Biological Assay; D002138:Calibration; D006801:Humans; D007094:Imides / Q000737:chemistry*; D007328:Insulin / Q000737:chemistry*; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D012995:Solubility
chemical_list: D000577:Amides; D007094:Imides; D007328:Insulin; D037742:Nanotubes, Carbon
keywords: CNT; SWCNT; carboxylation; diimidation; drug carrier; increased solubility