title: Highly sensitive detection of caspase-3 activities via a nonconjugated gold nanoparticle-quantum dot pair mediated by an inner-filter effect.
abstract: We describe here a simple fluorometric assay for the highly sensitive detection of caspase-3 activities on the basis of the inner-filter effect of gold nanoparticles (AuNPs) on CdTe quantum dots (QDs). The method takes advantage of the high molar absorptivity of the plasmon band of gold nanoparticles as well as the large absorption band shift from 520 to 680 nm upon nanoparticle aggregation. When labeled with a peptide possessing the caspase-3 cleavage sequence (DEVD), the monodispersed Au-Ps (peptide-modified AuNPs) exhibited a tendency to aggregate when exposed to caspase-3, which induced the absorption band transition from 520 to 680 nm and turned on the fluorescence of the CdTe QDs for caspase-3 sensing. Under optimum conditions, a high sensitivity towards caspase-3 was achieved with a detection limit as low as 18 pM, which was much lower than the corresponding assays based on absorbance or other approaches. Overall, we demonstrated a facile and sensitive approach for caspase-3 detection, and we expected that this method could be potentially generalized to design more fluorescent assays for sensing other bioactive entities.
authors.affiliation: College of Chemistry, Chemical Engineering and Materials Science, Soochow University , Suzhou 215123, China.
authors.forename: Jingwen
authors.initials: J
authors.lastname: Li
authors.forename: Xinming
authors.initials: X
authors.lastname: Li
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Shi
authors.forename: Xuewen
authors.initials: X
authors.lastname: He
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Nan
authors.initials: N
authors.lastname: Ma
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
mesh_terms: D000042:Absorption; D015374:Biosensing Techniques; D019187:Cadmium Compounds / Q000737:chemistry; D053148:Caspase 3 / Q000737:chemistry / Q000302:isolation & purification*; D006046:Gold / Q000737:chemistry*; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry*; D045663:Quantum Dots / Q000737:chemistry; D013691:Tellurium / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D006046:Gold; D053148:Caspase 3; D013691:Tellurium; C028337:cadmium telluride