Sensitive and Selective Plasmon Ruler Nanosensors for Monitoring the Apoptotic Drug Response in Leukemia

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–shell 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.

Strategies for enhancing the sensitivity of plasmonic nanosensors

“…The enzyme-guided signal amplification has also been used to monitor the activity of an enzyme. For instance, a plasmon ruler was reported for the sensitive and selective determination of the activity of caspase-3 [203]. A pair of Zn 0.4 Fe 2.6 O 4 @SiO 2 @Au core-shell nanoparticles was connected by a caspase-3 cleavage sequence.…”

A Programmed Nanoparticle with Self-Adapting for Accurate Cancer Cell Eradication and Therapeutic Self-Reporting

“…The fluorescence of Dabcyl-KFFFDEVDK-FAM is turn-off due to the fluorescence resonance energy transfer (FRET) effect and can be turn-on upon reaction with caspase-3, an important downstream protease in apoptosis 31. The hydrophobic block PLGA composes the inner core of GAI@CP and encapsulates CPT and FRET-Pep.…”

Inorganic nanoparticles for biomedicine: where materials scientists meet medical research

“…Craik et al developed a sensing device for caspase-3, a biomolecule of high relevance in myeloid leukemia [37]. The working concept of the sensor relies on producing dimers of Au nanoparticles that are linked by a caspase-3 cleavage sequence, that is, a peptide sequence that selectively reacts with caspase-3.…”

“…Rather than relying on hotspots (such as reported in [37,38]), their method focused on the spectral shift that occurs when a Raman tag (covalently bound to a receptor) binds a peptide ligand (Fig. 4).…”

“…In the absence of caspase-3, plasmon coupling (blue color) occurs due to the short interparticle distance. When caspase-3 is present, the linker is cleaved resulting in a plasmon signal for isolated nanoparticles (red color) [37]. Copyright 2014, American Chemical Society.…”