Application of AlDeSense to Stratify Ovarian Cancer Cells Based on Aldehyde Dehydrogenase 1A1 Activity

Relapse after cancer treatment is often attributed to the persistence of a subpopulation of tumor cells known as cancer stem cells (CSCs), which are ...

University of Illinois Urbana-Champaign

Hypoxia occurs when limited oxygen supply impairs physiological functions and is a pathological hallmark of many diseases including cancer and ischemia. Thus, detection of hypoxia can guide treatment planning and serve as a predictor of patient prognosis. Unfortunately, current methods suffer from invasiveness, poor resolution and low specificity. To address these limitations, we present Hypoxia Probe 1 (HyP-1), a hypoxia-responsive agent for photoacoustic imaging. This emerging modality converts safe, non-ionizing light to ultrasound waves, enabling acquisition of high-resolution 3D images in deep tissue. HyP-1 features an N-oxide trigger that is reduced in the absence of oxygen by heme proteins such as CYP450 enzymes. Reduction of HyP-1 produces a spectrally distinct product, facilitating identification via photoacoustic imaging. HyP-1 exhibits selectivity for hypoxic activation in vitro, in living cells, and in multiple disease models in vivo. HyP-1 is also compatible with NIR fluorescence imaging, establishing its versatility as a multimodal imaging agent.

A bioreducible N-oxide-based probe for photoacoustic imaging of hypoxia.

In this chapter, we motivate the need for photoactivatable NO donor molecules and give a brief survey of the existing chemical tools in the field. We then provide detailed protocols for the synthesis and validation of a near-infrared light-activated NO donor molecule, photoNOD-1, developed in our research group. With this tool, NO can be released in vivo in a radiation-dependent manner that can be monitored using photoacoustic imaging.

Near-infrared photoactivatable nitric oxide donors with photoacoustic readout.

Acoustic-based imaging modalities (e.g. ultrasonography and photoacoustic imaging) have emerged as powerful approaches to noninvasively visualize the interior of the body due to their biocompatibility and the ease of sound transmission in tissue. These technologies have recently been augmented with an array of chemical tools that enable the study and modulation of the tumor microenvironment at the molecular level. In addition, the application of ultrasound and ultrasound-responsive materials has been used for drug delivery with high spatiotemporal control. In this review, we highlight recent advances (in the last 2-3 years) in acoustic-based chemical tools and technologies suitable for furthering our understanding of molecular events in complex tumor microenvironments.

Acoustic-based chemical tools for profiling the tumor microenvironment.

 imaging is a powerful approach to study biological processes. Beyond cellular methods,  studies allow for biological stimuli (small molecules or proteins) to be studied in their native environment. This has the potential to aid in the discovery of new biology and guide the development of diagnostics and therapies for diseases. To ensure selectivity and an observable readout, the probe development field is shifting towards activity-based sensing (ABS) approaches and near-infrared (NIR) imaging modalities. This perspective will highlight recent  ABS applications that utilize NIR imaging platforms.

New directions of activity-based sensing for  NIR imaging.

In this chapter, we introduce a two-phase tuning approach for developing highly sensitive photoacoustic probes for imaging nitric oxide (NO) in the near-infrared (NIR)-II window. Due to the synthetically challenging nature of current NIR-II dye platforms, our two-phase tuning approach circumvents this issue by first allowing one to tune the reactivity using a synthetically accessible dye. We have used a physical organic workflow to understand the reaction kinetics and identify the most reactive sensing component. The selected reactive trigger is then introduced to phase two where it is appended to a range of well-established NIR-II dyes. This strategy is used to select the ideal photoacoustic probe for NIR-II imaging in vivo. Here, we have detailed procedures for synthesis, in vitro studies, and in vivo imaging.

Near-infrared II photoacoustic probes for nitric oxide sensing.

In this chapter, we describe a generalizable strategy to obtain a high PA output platform that is optimized for ratiometric imaging. Our approach entails conformationally restricting pendant aryl rings on the aza-BODIPY core to enhance orbital overlap which consequently increases the extinction coefficient. This strategy can potentially be applied to other dye platforms to enhance their signal intensity. We provide detailed protocols for the synthesis, in vitro characterization, and in vivo application.

A general strategy to optimize the performance of aza-BODIPY-based probes for enhanced photoacoustic properties.

The development of high-performance photoacoustic (PA) probes that can monitor disease biomarkers in deep tissue has the potential to replace invasive medical procedures such as a biopsy. However, such probes must be optimized for in vivo performance and exhibit an exceptional safety profile. In this study, we have developed PACu-1, a PA probe designed for biopsy-free assessment (BFA) of hepatic Cu via photoacoustic imaging. PACu-1 features a Cu(I)-responsive trigger appended to an aza-BODIPY dye platform that has been optimized for ratiometric sensing. Owing to its excellent performance, we were able to detect basal levels of Cu in healthy wild-type mice as well as elevated Cu in a Wilson's disease model and in a liver metastasis model. To showcase the potential impact of PACu-1 for BFA, we conducted two blind studies in which we were able to successfully identify Wilson's disease animals from healthy control mice in each instance.

Activity-based photoacoustic probe for biopsy-free assessment of copper in murine models of Wilson's disease and liver metastasis.

Companion diagnostics (CDx) are powerful tests that can provide physicians with crucial biomarker information that can improve treatment outcomes by matching therapies to patients. Here, we report a photoacoustic imaging-based CDx (PACDx) for the selective detection of elevated glutathione (GSH) in a lung cancer model. GSH is abundant in most cells, so we adopted a physical organic chemistry approach to precisely tune the reactivity to distinguish between normal and pathological states. To evaluate the efficacy of PACDx in vivo, we designed a blind study where photoacoustic imaging was used to identify mice bearing lung xenografts. We also employed PACDx in orthotopic lung cancer and liver metastasis models to image GSH. In addition, we designed a matching prodrug, PARx, that uses the same SAr chemistry to release a chemotherapeutic with an integrated PA readout. Studies demonstrate that PARx can inhibit tumour growth without off-target toxicity in a lung cancer xenograft model.

Photoacoustic imaging of elevated glutathione in models of lung cancer for companion diagnostic applications.

Photoacoustic (PA) imaging has emerged as a powerful technique for the high resolution visualization of biological processes within deep tissue. Through the development and application of exogenous targeted contrast agents and activatable probes that can respond to a given cancer biomarker, researchers can image molecular events  during cancer progression. This information can provide valuable details that can facilitate cancer diagnosis and therapy monitoring. In this tutorial review, we provide a step-by-step guide to select a cancer biomarker and subsequent approaches to design imaging agents for  use. We envision this information will be a useful summary to those in the field, new members to the community, and graduate students taking advanced imaging coursework. We also highlight notable examples from the recent literature, with emphasis on the molecular designs and their  PA imaging performance. To conclude, we provide our outlook and future perspective in this exciting field.

Jefferson Chan

Department of Chemistry,
Department of Biochemistry,
Beckman Institute for Advanced Science and Technology,
Cancer Center of Illinois

University of Illinois Urbana-Champaign

Application of AlDeSense to Stratify Ovarian Cancer Cells Based on Aldehyde Dehydrogenase 1A1 Activity

Jefferson Chan

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Chemistry,Department of Biochemistry,Beckman Institute for Advanced Science and Technology,Cancer Center of Illinois

University of Illinois Urbana-Champaign

Application of AlDeSense to Stratify Ovarian Cancer Cells Based on Aldehyde Dehydrogenase 1A1 Activity

Department of Chemistry,
Department of Biochemistry,
Beckman Institute for Advanced Science and Technology,
Cancer Center of Illinois