Advances in Imaging Techniques and Genetically Encoded Probes for Photoacoustic Imaging

Abstract

Photoacoustic (PA) imaging is a rapidly emerging biomedical imaging modality that is capable of visualizing cellular and molecular functions with high detection sensitivity and spatial resolution in deep tissue. Great efforts and progress have been made on the development of various PA imaging technologies with improved resolution and sensitivity over the past two decades. Various PA probes with high contrast have also been extensively developed, with many important biomedical applications. In comparison with chemical dyes and nanoparticles, genetically encoded probes offer easier labeling of defined cells within tissues or proteins of interest within a cell, have higher stability in vivo, and eliminate the need for delivery of exogenous substances. Genetically encoded probes have thus attracted increasing attention from researchers in engineering and biomedicine. In this review, we aim to provide an overview of the existing PA imaging technologies and genetically encoded PA probes, and describe further improvements in PA imaging techniques and the near-infrared photochromic protein BphP1, the most sensitive genetically encoded probe thus far, as well as the potential biomedical applications of BphP1-based PA imaging in vivo.

Challenging a preconception: Optoacoustic spectrum differs from the absorption spectrum of proteins and dyes for molecular imaging

“…Characterization of GFP-type chromophore bearing proteins Genetically encode labels are a prerequisite for longitudinal imaging and one of the reasons for fluorescence imaging becoming a standard tool in life sciences. GFP-like labels are prominent in fluorescence imaging and, despite their mostly visible absorbance profiles, have also been studied and employed as OA labels 6,12,[52][53][54] . However, biliverdin bearing chromoproteins like Bacteriophytochromes (BphPs) or Phycobiliproteins (Pbp) are advantageous due to their near-infrared absorbance (NIR) and have already been employed prominently in OA imaging 10,11,[54][55][56][57] .…”

Breakthroughs in modern cancer therapy and elusive cardiotoxicity: Critical research‐practice gaps, challenges, and insights

“…Medical diagnosis and therapeutic options benefit greatly from imaging technologies that combine molecular and microscopic parameters with clinical observations; such a combination is provided by photoacoustic imaging (also known as optoacoustic imaging) . Photoacoustic imaging is a label‐free, non‐ionizing, noninvasive, high‐resolution optical imaging modality that uses optical absorption contrast and ultrasonic resolution . This technology has a high scalability and allows imaging of biological structures, ranging from molecules, organelles, cells, and tissues to entire organs and even entire small animal bodies .…”

“…[272][273][274][275][276] Photoacoustic imaging is a label-free, non-ionizing, noninvasive, high-resolution optical imaging modality that uses optical absorption contrast and ultrasonic resolution. [277][278][279][280][281][282] This technology has a high scalability and allows imaging of biological structures, ranging from molecules, organelles, cells, and tissues to entire organs and even entire small animal bodies. 273,275,280,[283][284][285][286] The anatomical, functional, metabolic, and histologic properties of tissues or organs can be solely revealed by endogenous contrast (e.g., hemoglobin, lipids, melanin, and collagen), while exogenous contrast agents are only used to further increase the imaging contrast and specificity.…”

“…273,275,280,[283][284][285][286] The anatomical, functional, metabolic, and histologic properties of tissues or organs can be solely revealed by endogenous contrast (e.g., hemoglobin, lipids, melanin, and collagen), while exogenous contrast agents are only used to further increase the imaging contrast and specificity. 273,283 Various exogenous probes with high contrast have also been extensively developed, including inorganic and organic dyes, 274 magneto-optical and photochromic probes, 283 nanoparticles, 282,287 and genetically encoded probes, 281 to achieve improved resolution and sensitivity while providing multi-parametric photoacoustic imaging. 283 This imaging modality has proven its clinical and preclinical value in functional, structural, and molecular aspects of diseases and has been used for physiologically and pathologically imaging various organs and tissues, including breast cancer, [288][289][290][291][292] neural tissues, 277,287,[293][294][295] fingers, 296 sentinel lymph nodes, 277,292,297 the cardiovascular system, [298][299][300][301][302] the prostate, 303,304 skin, 305 cancer therapy, 273,274,…”

Light-Mediated Deep-Tissue Theranostics

“…Huang et al summarized developments in PAI, which affords good contrast, high resolution, and deep tissue penetration 11. Meanwhile, Chu et al reviewed progress on developing genetically encoded probes for PAI, with an emphasis on BphP1-based tags 12. Compared with molecule or nanoparticle based PAT probes, genetically encoded ones afford advantages including facile labeling of cells and protein targets and good in vivo stability.…”