This study describes the first instance of the use of two differently sized Au nanoparticles (Au NPs), acting separately as donor and acceptor, in homogeneous photoluminescence quenching assays developed for the analysis of
proteins. Introduction of a
breast cancer marker
protein,
platelet-derived growth factor AA (
PDGF AA), to a
solution of
11-mercaptoundecanoic acid-protected, 2.0-nm photoluminescent Au nanodots (L(AuND)) led to the preparation of
PDGF AA-L(AuND) as the donor.
Thiol-derivative PDGF binding aptamers (
Apt) and 13-nm spherical Au NPs were used to synthesize the
Apt-Q(AuNP) acceptor. The photoluminescence of
PDGF AA-L(AuND) at 520 nm decreased when photoluminescence quenching occurred between
Apt-Q(AuNP) and
PDGF AA-L(AuND). We used the
PDGF AA-L(AuND)/
Apt-Q(AuNP)-based molecular light switching system to analyze PDGFs and
PDGF alpha-receptor in separate homogeneous solutions. In the presence of PDGFs, the interaction between
Apt-Q(AuNP) and
PDGF AA-L(AuND) decreased as a result of competitive reactions between the PDGFs and
Apt-Q(AuNP). Similarly, the interaction between
Apt-Q(AuNP) and
PDGF AA-L(AuND) reduced as a result of competitive reactions between
PDGF alpha-receptor and
PDGF AA-L(AuND). The limits of detection (LODs) for
PDGF AA and
PDGF alpha-receptor were 80 pM and 0.25 nM, respectively, resulting from a low background photoluminescence signal. When using the
Apt-Q(AuNP) as selectors for (a) the enrichment of
PDGF AA and (b) the removal of matrixes possessing intense background fluorescence from cell media and urine samples, the LOD for
PDGF AA decreased to 10 pM. Unlike
quantum dots, the L(AuND) provide the advantages of biocompatibility, ease of bioconjugation, and minimal toxicity.