PSA fluoroimmunoassays using anti-PSA ScFv and quantum-dot conjugates.
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.
Wang
Yunjun
Y
Mesolight LLC, BioVentures/UAMS, Little Rock, AR 72205, USA. yjwang@mesolight.com
Dossey
Amy M
AM
Froude
Jeffrey W
JW
Lubitz
Shannon
S
Tzur
Dan
D
Semenchenko
Valentyna
V
Wishart
David S
DS
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
D007128:Immunoglobulin Fragments; D017430:Prostate-Specific Antigen