Photoacoustic Imaging Probes Based on Tetrapyrroles and Related Compounds

Abstract

Photoacoustic imaging (PAI) is a rapidly evolving field in molecular imaging that enables imaging in the depths of ultrasound and with the sensitivity of optical modalities. PAI bases on the photoexcitation of a chromophore, which converts the absorbed light into thermal energy, causing an acoustic pressure wave that can be captured with ultrasound transducers, in generating an image. For in vivo imaging, chromophores strongly absorbing in the near-infrared range (NIR; > 680 nm) are required. As tetrapyrroles have a long history in biomedical applications, novel tetrapyrroles and inspired mimics have been pursued as potentially suitable contrast agents for PAI. The goal of this review is to summarize the current state of the art in PAI applications using tetrapyrroles and related macrocycles inspired by it, highlighting those compounds exhibiting strong NIR-absorption. Furthermore, we discuss the current developments of other absorbers for in vivo photoacoustic (PA) applications.

Probing the Interactions of Porphyrins with Macromolecules Using NMR Spectroscopy Techniques

“…Photodynamic diagnosis (PDD) measures the fluorescence of the PS enriched in tumor tissue or lesions [ 32 , 33 , 34 ]. Further imaging techniques make use of specific paramagnetic or radiolabeled metalloporphyrins as contrast agents for magnetic resonance imaging (MRI) [ 35 , 36 ], and positron emission tomography (PET) [ 37 , 38 ] or near-infrared (NIR)-absorbing porphyrins for photoacoustic imaging (PAI) [ 39 , 40 ] of tissue. Concomitant with the development of multimodal drugs, more recently, porphyrins are investigated as potential theranostics combining therapeutic and diagnostic functions [ 19 , 41 , 42 ].…”

Recent Advances of Polyaniline-Based Biomaterials for Phototherapeutic Treatments of Tumors and Bacterial Infections

“…Photoacoustic imaging (PAI) is a noninvasive and nonionizing biomedical imaging modality and based on the use of laser-generated ultrasound [ 71 ]. It possesses high optical contrast and spatial resolution, and is promising for diagnosis of disease.…”

Expanded porphyrins: functional photoacoustic imaging agents that operate in the NIR-II region

“…low pH, enzymes, and hydrogen peroxide (H 2 O 2 )). [7][8][9][10] However, most tetrapyrrolic PA systems are limited to the NIR region. 7,11 Absorption greater than 1000 nm, termed the second near-infrared region (NIR-II: 1000-1350 nm), allows for deeper tissue penetration and reduced light scattering than the NIR-I region (700−950 nm).…”