Multifunctional Gold Nanoclusters-Based Nanosurface Energy Transfer Probe for Real-Time Monitoring of Cell Apoptosis and Self-Evaluating of Pro-Apoptotic Theranostics

Abstract

Bioimaging probes for accurately monitoring apoptosis process have extensive significance for cell biological studies and clinical investigations. Herein, novel multifunctional peptide-tailored gold nanoclusters (AuNCs) have been developed for real-time imaging of caspase-indicated cell apoptosis. The AuNCs nanoprobe was facilely prepared by a one-step peptide-mediated biomineralization with the dye (TRAMA)-tagged peptides specific to caspase 3 as both template agents and the signal switch. Unlike conventional FRET-based fluorescent probes of caspase activity, these nanoprobes relied on the unique quenching effect of AuNCs through the nanosurface energy transfer (NSET) from dye to AuNCs. Intracellular caspase 3 activation cleaved the substrate peptide and released the dye from AuNCs, leading to a significant fluorescence lighting-up for sensitive and continuous analysis of caspase 3 activity in live cells, with a high signal-background ratio, wide linear range (32 pM-10 nM), and ultralow detection limit (12 pM). Moreover, this versatile AuNCs nanoprobe can serve as a theranostic platform via codisplaying pro-apoptotic and detecting peptides, which allows in situ activation and real-time monitoring of apoptosis in cancer cells. These results indicate that the AuNCs nanoprobe provides a smart molecular imaging and therapeutic agent targeted to cell apoptosis, which has great potential for apoptosis-related diagnosis and precision chemotherapy.

Monitoring Proteolytic Activity in Real Time: A New World of Opportunities for Biosensors

“…As shown in several reported works [37,38], gold nanoparticles are valuable optical labels in the field of proteolytic sensors. However, most of the strategies used to conjugate gold nanoparticles and peptides rely on the establishment of sulfur-gold bonds, which can be compromised by interference from other thiol-containing molecules that may be present in the medium.…”

An endogenous stimulus detonated nanocluster-bomb for contrast-enhanced cancer imaging and combination therapy

“…31,32 Based on this nding, AuNCs were synthesized to serve as an acceptor rather than a donor to design a nanosensor for stimuliresponsive contrast-enhanced imaging (the ratio of signal/noise was up to 20 in vitro) of caspase 3 activity in live cells. 24 The results displayed new potential of AuNCs which served as an activable reporter. More importantly, as for a nanocarrier, a simple synthetic route and multiple bio-ligands are available for AuNC synthesis, 33,34 such as SH-containing peptides, 35,36 proteins 37 and polymers.…”

“…Gold nanoclusters (AuNCs), known for their ultrasmall size and biocompatible properties, may offer an elegant solution to the need for simultaneously achieving stimuli-responsive contrast-enhanced imaging as a reporter, and maximizing the therapeutic efficacy and minimizing the side effect and toxicity as a nanovector. 17,23,24 As for a reporter, in the past few years, gold nanoclusters were mostly utilized for biosensing 25 and State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory for Bio-Nanotechnology and Molecule Engineering of Hunan Province, Changsha 410082, China. E-mail: xiaoxiaohe@hnu.edu.cn; kmwang@hnu.edu.cn bioimaging, 26 relying on their uorescence emission properties.…”

Quantum dots‐based fluorescence resonance energy transfer biosensor for monitoring cell apoptosis

“…Among these, caspase‐3 is especially important in this family, because it takes part in both intrinsic and extrinsic apoptotic pathways. It can typically recognize the 4‐amino acid peptide sequence Asp‐Glu‐Val‐Asp (DEVD) and cleaves its substrate at the C‐terminal Asp residue …”

“…It can typically recognize the 4-amino acid peptide sequence Asp-Glu-Val-Asp (DEVD) and cleaves its substrate at the C-terminal Asp residue. [17] With the development of fluorescence-based techniques, much attention has focused on fluorescence resonance energy transfer (FRET)-based biosensors. [7,18] In the FRET-based system, quantum dots (QDs) are becoming an effective energy donor due to their intrinsic optical properties, including high quantum yield, size-dependent photoluminescence with broad excitation spectra and sharp emission spectra, high photostability and excellent chemical stability.…”