Nanoparticle‐Based Activatable Probes for Bioimaging

Abstract

Molecular imaging can provide functional and molecular information at the cellular or subcellular level in vivo in a noninvasive manner. Activatable nanoprobes that can react to the surrounding physiological environment or biomarkers are appealing agents to improve the efficacy, specificity, and sensitivity of molecular imaging. The physiological parameters, including redox status, pH, presence of enzymes, and hypoxia, can be designed as the stimuli of the activatable probes. However, the success rate of imaging nanoprobes for clinical translation is low. Herein, the recent advances in nanoparticle‐based activatable imaging probes are critically reviewed. In addition, the challenges for clinical translation of these nanoprobes are also discussed in this review.

Activatable Probes for Ratiometric Imaging of Endogenous Biomarkers In Vivo

“…However, these probes show poor signal specificity and sensitivity with a low signal-to-background ratio (SBR). , In the second stage, activatable probes with biomarker-responsive mechanisms were developed to improve the sensitivity and specificity of the imaging. These probes were initially “off”, and their signal was activated only by the biomarkers of interest in the pathological microenvironment (Figure b). − The activatable probes offer a higher SBR as well as a lower limit of detection compared to the “always on” probes. They allow semi-quantification of biomarkers in real time in vivo . − The biggest challenge of conventional probes located in the above two stages is their absolute intensity-dependent signal readout.…”

Luminescence Nanoprobes for Drug Screening, Pharmaceutical Analysis, and Therapeutic Evaluations

“…[6,7] The high specific surface area affords great surface functionality, which can be used to tune nanoprobes for in vitro and in vivo tissue or cell targeting, sensing, and imaging. [8,9] As well documented, NPs with appropriate biophysicochemical properties, such as size, morphology, and surface chemistry, can efficiently accumulate in specific tissues and/or diseases sites, cells, and subcellular organelles. These outstanding features have enabled luminescence nanoprobes to monitor specific biological processes, study targeting capability of nanomedicines, determine interactions between drugs and targets, discover novel therapeutic targets, perform pharmacological effect-based drug screening, and evaluate drug efficacies.…”