Quantitative and Reversible Lectin-Induced Association of Gold Nanoparticles Modified with α-Lactosyl-ω-mercapto-poly(ethylene glycol)

Gold nanoparticles (1−10 nm size range) were prepared with an appreciably narrow size distribution by in situ reduction of HAuCl4 in the presence of heterobifunctional poly(ethylene glycol) (PEG) derivatives containing both mercapto and acetal groups (α-acetal-ω-mercapto-PEG). The α-acetal-PEG layer...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2001-08, Vol.123 (34), p.8226-8230
Main Authors: Otsuka, Hidenori, Akiyama, Yoshitsugu, Nagasaki, Yukio, Kataoka, Kazunori
Format: Article
Language:English
Subjects:
Gold - chemistry
Lectins - chemistry
Particle Size
Polyethylene Glycols - chemistry
Surface Plasmon Resonance
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Summary:Gold nanoparticles (1−10 nm size range) were prepared with an appreciably narrow size distribution by in situ reduction of HAuCl4 in the presence of heterobifunctional poly(ethylene glycol) (PEG) derivatives containing both mercapto and acetal groups (α-acetal-ω-mercapto-PEG). The α-acetal-PEG layers formed on gold nanoparticles impart appreciable stability to the nanoparticles in aqueous solutions with elevated ionic strength and also in serum-containing medium. The PEG acetal terminal group was converted to aldehyde by gentle acid treatment, followed by the reaction with p-aminophenyl-β-d- lactopyranoside (Lac) in the presence of (CH3)2NHBH3. Lac-conjugated gold nanoparticles exhibited selective aggregation when exposed to Recinus communis agglutinin (RCA120), a bivalent lectin specifically recognizing the β-d-galactose residue, inducing significant changes in the absorption spectrum with concomitant visible color change from pinkish-red to purple. Aggregation of the Lac-functionalized gold nanoparticles by the RCA120 lectin was reversible, recovering the original dispersed phase and color by addition of excess galactose. Further, the degree of aggregation was proportional to lectin concentration, allowing the system to be utilized to quantitate lectin concentration with nearly the same sensitivity as ELISA. This simple, yet highly effective, derivatization of gold nanoparticles with heterobifunctional PEG provides a convenient method to construct various colloidal sensor systems currently applied in bioassays and biorecognition.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja010437m