title: Genome-free viral capsids as carriers for positron emission tomography radiolabels.
abstract: OBJECTIVE
  We have developed a modular synthetic strategy to append imaging agents to a viral capsid.
  
  
  METHODS
  The hollow protein shell of bacteriophage MS2 (mtMS2) was labeled on its inside surface with [18F]fluorobenzaldehyde through a multistep bioconjugation strategy. An aldehyde functional group was first attached to interior tyrosine residues through a diazonium coupling reaction. The aldehyde was further elaborated to an alkoxyamine functional group, which was then condensed with n.c.a. [18F]fluorobenzaldehyde. Biodistribution of the radioactive MS2 conjugates was subsequently evaluated in Sprague-Dawley rats.
  
  
  RESULTS
  Relative to fluorobenzaldehyde, fluorine-18-labeled MS2 exhibited prolonged blood circulation time and a significantly altered excretion profile. It was also observed that additional small molecule cargo installed inside the capsids did not alter the biodistribution.
  
  
  CONCLUSIONS
  These studies provide further insight into the pharmacokinetic behavior of nanomaterials and serve as a platform for the future development of targeted imaging and therapeutic agents based on mtMS2.
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA.
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Hooker
authors.forename: James P
authors.initials: JP
authors.lastname: O'Neil
authors.forename: Dante W
authors.initials: DW
authors.lastname: Romanini
authors.forename: Scott E
authors.initials: SE
authors.lastname: Taylor
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Francis
mesh_terms: D000818:Animals; D001547:Benzaldehydes / Q000138:chemical synthesis / Q000737:chemistry; D002213:Capsid / Q000737:chemistry*; D036022:Capsid Proteins / Q000097:blood / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism / Q000493:pharmacokinetics; D003374:Coumarins / Q000737:chemistry; D004285:Dogs; D016503:Drug Delivery Systems; D005462:Fluorine Radioisotopes / Q000737:chemistry; D007553:Isotope Labeling; D017909:Levivirus / Q000737:chemistry; D015394:Molecular Structure; D008970:Molecular Weight; D010091:Oximes / Q000737:chemistry; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001547:Benzaldehydes; D036022:Capsid Proteins; D003374:Coumarins; D005462:Fluorine Radioisotopes; D010091:Oximes; D019275:Radiopharmaceuticals