An active DNA-based nanoprobe for photoacoustic pH imaging

Recent advances in DNA-based probes for photoacoustic imaging

Photoacoustic imaging(PAI) is a widely developing imaging modality that has seen tremendous evolvement in the last decade. PAI has gained the upper hand in the imaging field as it takes advantage of optical absorption and ultrasound detection that imparts higher resolution, rich contrast and elevated penetration depth. Unlike other imaging techniques, PAI does not use ionising radiation and is a better, cost-effective and healthier alternative to other imaging techniques. It offers greater specificity than conventional ultrasound imaging with the ability to detect haemoglobin, lipids, water and other light-absorbing chromophores. These properties of PAI have led to its extended applications in the biomedical field in the treatment of diseases such as cancer. This paper reviews how DNA probes have been used in PAI, the various techniques by which it has been modified, and their role in the process. We also focus on different nanocomposites containing DNA having PAI and photothermal therapy(PTT) properties for detection, diagnosis and therapy, its constituents and the role of DNA in it.

Biomedical Photoacoustic Imaging for Molecular Detection and Disease Diagnosis: "Always-On" and "Turn-On" Probes

Photoacoustic (PA) imaging is a nonionizing, noninvasive imaging technique that combines optical and ultrasonic imaging modalities to provide images with excellent contrast, spatial resolution, and penetration depth. Exogenous PA contrast agents are created to increase the sensitivity and specificity of PA imaging and to offer diagnostic information for illnesses. The existing PA contrast agents are categorized into two groups in this review: "always-on" and "turn-on," based on their ability to be triggered by target molecules. The present state of these probes, their merits and limitations, and their future development, is explored.

pH-Activatable Cyanine Dyes for Selective Tumor Imaging Using Near-Infrared Fluorescence and Photoacoustic Modalities

Photoacoustic (PA) imaging is an emerging molecular imaging modality that complements fluorescence imaging and enables high resolution within deep tissue. Fluorescence/PA multimodality imaging would be a powerful technique to extract more comprehensive information from targets than traditional single-modality imaging. In this paper, we developed a new pH-activatable sensor, CypHRGD, which is applicable to both fluorescence and PA detection. CypHRGD was derived from our previous near-infrared pH-sensing platform, in which substitution with a bulky phenyl group and functionalization with a cRGD peptide remarkably improved the sensor's biocompatibility with attenuated dye aggregation. The multimodality imaging applications of CypHRGD were demonstrated in cultured cells and cancer-xenografted mice with rapid kinetics and high sensitivity and specificity, which relies on cRGD-facilitated tumor targeting, probe accumulation and subsequent activation in the acidic organelles after endocytosis.

DNA-Based Nanocarriers to Enhance the Optoacoustic Contrast of Tumors In Vivo

Optoacoustic tomography (OT) enables non-invasive deep tissue imaging of optical contrast at high spatio-temporal resolution. The applications of OT in cancer imaging often rely on the use of molecular imaging contrast agents based on near-infrared (NIR) dyes to enhance contrast at the tumor site. While these agents afford excellent biocompatibility and minimal toxicity, they present limited optoacoustic signal generation capability and rapid renal clearance, which can impede their tumor imaging efficacy. In this work, a synthetic strategy to overcome these limitations utilizing biodegradable DNA-based nanocarrier (DNA-NC) platforms is introduced. DNA-NCs enable the incorporation of NIR dyes (in this case, IRDye 800CW) at precise positions to enable fluorescence quenching and maximize optoacoustic signal generation. Furthermore, these DNA-NCs show a prolonged blood circulation compared to the native fluorophores, facilitating tumor accumulation by the enhanced permeability and retention (EPR) effect. In vivo imaging of tumor xenografts in mice following intravenous administration of DNA-NCs reveals enhanced OT signals at 24 h when compared to free fluorophores, indicating promise for this method to enhance the optoacoustic signal generation capability and tumor uptake of clinically relevant NIR dyes.