title: Label-free biosensing by surface plasmon resonance of nanoparticles on glass: optimization of nanoparticle size.
abstract: The unique optical properties of noble metal nanoparticles have been used to design a label-free biosensor in a chip format. In this paper, we demonstrate that the size of gold nanoparticles significantly affects the sensitivity of the biosensor. Gold nanoparticles with diameters in the range of 12-48 nm were synthesized in solution and sensor chips were fabricated by chemisorption of these nanoparticles on amine-functionalized glass. Sensors fabricated from 39-nm-diameter gold nanoparticles exhibited maximum sensitivity to the change of the bulk refractive index and the largest "analytical volume", defined as the region around the nanoparticle within which a change in refractive index causes a change in the optical properties of the immobilized nanoparticles. The detection limit for streptavidin-biotin binding of a sensor fabricated from 39-nm-diameter nanoparticles was 20-fold better than a previously reported sensor fabricated from 13-nm-diameter gold nanoparticles. We also discuss several other factors that could improve the performance of the next generation of these immobilized metal nanoparticle sensors.
authors.affiliation: Department of Biomedical Engineering, Box 90281, Duke University, Durham, North Carolina 27708-0281, USA.
authors.forename: Nidhi
authors.initials: N
authors.lastname: Nath
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Chilkoti
mesh_terms: D005898:Glass / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry*; D010316:Particle Size; D012031:Refractometry / Q000379:methods; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis; D020349:Surface Plasmon Resonance / Q000379:methods*
chemical_list: D006046:Gold