한빛사 논문
Abstract
Cheryl A. Tajon†, Daeha Seo ‡§⊥, Jennifer Asmussen∥, Neil Shah∥, Young-wook Jun ‡*, and Charles S. Craik †*
† Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158, United States
‡ Department of Otolaryngology, University of California, San Francisco, California 94115, United States
§ Department of Chemistry, University of California, Berkeley, California 94720, United States
⊥ Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
∥ Department of Pharmaceutical Sciences
*Correspondence to Young-wook Jun, Charles S. Craik
Abstract
Caspases are proteases involved in cell death, where caspase-3 is the chief executioner that produces an irreversible cutting event in downstream protein substrates and whose activity is desired in the management of cancer. To determine such activity in clinically relevant samples with high signal-to-noise, plasmon rulers are ideal because they are sensitively affected by their interparticle separation without ambiguity from photobleaching or blinking effects. A plasmon ruler is a noble metal nanoparticle pair, tethered in close proximity to one another via a biomolecule, that acts through dipole-dipole interactions and results in the light scattering to increase exponentially. In contrast, a sharp decrease in intensity is observed when the pair is confronted by a large interparticle distance. To align the mechanism of protease activity with building a sensor that can report a binary signal in the presence or absence of caspase-3, we present a caspase-3 selective plasmon ruler (C3SPR) composed of a pair of Zn0.4Fe2.6O4@SiO2@Au core-hell nanoparticles connected by a caspase-3 cleavage sequence. The dielectric core (Zn0.4Fe2.6O4@SiO2)-shell (Au) geometry provided a brighter scattering intensity versus solid Au nanoparticles, and the magnetic core additionally acted as a purification handle during the plasmon ruler assembly. By monitoring the decrease in light scattering intensity per plasmon ruler, we detected caspase-3 activity at single molecule resolution across a broad dynamic range. This was observed to be as low as 100 fM of recombinant material or 10 ng of total protein from cellular lysate. By thorough analyses of single molecule trajectories, we show caspase-3 activation in a drug-treated chronic myeloid leukemia (K562) cancer system as early as 4 and 8 h with greater sensitivity (2- and 4-fold, respectively) than conventional reagents. This study provides future implications for monitoring caspase-3 as a biomarker and efficacy of drugs.
Keywords : caspase; gold nanoparticles; plasmon coupling; leukemia; single molecule
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