Influence of the Debye length on the interaction of a small molecule-modified Au nanoparticle with a surface-bound bioreceptor.
We report that a shorter Debye length and, as a consequence, decreased colloidal stability are required for the molecular interaction of folic acid-modified Au nanoparticles (Au NPs) to occur on a surface-bound receptor, human dihydrofolate reductase (hDHFR). The interaction measured using surface plasmon resonance (SPR) sensing was optimal in a phosphate buffer at pH 6 and ionic strength exceeding 300 mM. Under these conditions, the aggregation constant of the Au NPs was approximately 10(4) M(-1) s(-1) and the Debye length was below 1 nm, on the same length scale as the size of the folate anion (approximately 0.8 nm). Longer Debye lengths led to poorer SPR responses, revealing a reduced affinity of the folic acid-modified Au NPs for hDHFR. While high colloidal stability of Au NPs is desired in most applications, these conditions may hinder molecular interactions due to Debye lengths exceeding the size of the ligand and thus preventing close interactions with the surface-bound molecular receptor.
Département de chimie, Université de Montreal, C.P. 6128 Succ. Centre-Ville, Montreal, Qc, CanadaH3C 3J7. jf.masson@umontreal.ca.
Natalia
N
Bukar
Sandy Shuo
SS
Zhao
David M
DM
Charbonneau
Joelle N
JN
Pelletier
Jean-Francois
JF
Masson
D001665:Binding Sites; D015374:Biosensing Techniques; D005492:Folic Acid / Q000737:chemistry / Q000378:metabolism; D006046:Gold / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D008727:Methotrexate / Q000032:analysis / Q000378:metabolism; D009994:Osmolar Concentration; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020349:Surface Plasmon Resonance; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry* / Q000378:metabolism
D006046:Gold; D005492:Folic Acid; D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate