title: PSA fluoroimmunoassays using anti-PSA ScFv and quantum-dot conjugates.
abstract: OBJECTIVE
  The conjugates of monoclonal antibodies and luminescent nanoparticles (quantum dots [Qdots]) have a large number of potential applications in both fluoroimmunoassays and biological imaging; however, conjugating full-length antibody monoclonal antibodies directly to Qdots or other inorganic nanoparticles often results in the irreversible formation of oligomeric monoclonal antibody-nanoparticle complexes, which leads to dramatically reduced binding activities. This study demonstrated that the use of single-chain antibody fragments (scFvs) appears to have a number of advantages, in terms of solubility, activity, ease of preparation and ease of structure-based genetic engineering.
  
  
  METHODS
  Two antiprostate-specific antigen scFvs mutants--one with an 11-residue c-myc (referred as scFvB80-M1) and the other with a lysine-enriched His 6-tagging peptide attached to their C-termini (referred as scFvB80-M2)--were prepared. These two scFv mutants were conjugated directly with CdSe/ZnS Qdots and their binding activities were measured and compared.
  
  
  CONCLUSIONS
  Both scFv mutants can be conjugated covalently with CdSe/ZnS Qdots; however, the resulting conjugates exhibit significantly different affinities in the prostate-specific antigen fluoroimmunoassays--the binding activity of scFvB80-M2/Qdots is equivalent of that of free scFvB80 and four times of that of scFvB80-M1/Qdots.
  
  
  CONCLUSIONS
  This study demonstrates that binding activity of scFv/Qdot conjugates can be improved through structure-based genetic engineering of the scFv.
authors.affiliation: Mesolight LLC, BioVentures/UAMS, Little Rock, AR 72205, USA. yjwang@mesolight.com
authors.forename: Yunjun
authors.initials: Y
authors.lastname: Wang
authors.forename: Amy M
authors.initials: AM
authors.lastname: Dossey
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Froude
authors.forename: Shannon
authors.initials: S
authors.lastname: Lubitz
authors.forename: Dan
authors.initials: D
authors.lastname: Tzur
authors.forename: Valentyna
authors.initials: V
authors.lastname: Semenchenko
authors.forename: David S
authors.initials: DS
authors.lastname: Wishart
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D015200:Fluoroimmunoassay / Q000379:methods; D006801:Humans; D007128:Immunoglobulin Fragments / Q000737:chemistry* / Q000276:immunology; D036103:Nanotechnology / Q000379:methods*; D017430:Prostate-Specific Antigen / Q000276:immunology*; D045663:Quantum Dots
chemical_list: D007128:Immunoglobulin Fragments; D017430:Prostate-Specific Antigen