Cyanine Conjugate‐Based Biomedical Imaging Probes

Abstract

Cyanine is a class of fluorescent dye with meritorious fluorescence properties and has motivated numerous researchers to explore its imaging capabilities by miscellaneous structural modification and functionalization strategies. The covalent conjugation with other functional molecules represents a distinctive design strategy and has shown immense potential in both basic and clinical research. This review article summarizes recent achievements in cyanine conjugate-based probes for biomedical imaging. Particular attention is paid to the conjugation with targeting warheads and other contrast agents for targeted fluorescence imaging and multimodal imaging, respectively. Additionally, their clinical potential in cancer diagnostics is highlighted and some concurrent impediments for clinical translation are discussed.

Recent Advances in Cyanine-Based Phototherapy Agents

“…Cyanine core is among the most investigated fluorophores due to its favorable optical properties such as high molar absorptivity, narrow absorption/emission bands, reasonable fluorescence quantum yield, and most importantly, tunable fluorescence profile from the UV–vis to NIR range ( Delaey et al, 2000 ; Mishra et al, 2000 ; Kulbacka et al, 2011 ; Bhattarai and Dai, 2017 ; Li Y. et al, 2020 ; Li et al, 2021 ). Additionally, the excellent biocompatibility and low toxicity make them a great candidate for biological studies spanning from imaging to therapy.…”

Probing tricarbocyanine dyes for targeted delivery of anthracyclines

“…18 Abovementioned properties of tricarbocyanines were utilized for the development of fluorescent and theranostic conjugates. 2,14 Сarbocyanine dyes were applied as delivery vectors in covalent conjugates with various anticancer agents and in some cases were shown to increase their cytotoxicity. 2,14,19 For example, conjugate of non-toxic cytoprotective agent troxipide with dye MHI-148 showed nanomolar cytotoxic activity (EC50 267 nM) on three glioblastoma cell lines.…”

“…2,14 Сarbocyanine dyes were applied as delivery vectors in covalent conjugates with various anticancer agents and in some cases were shown to increase their cytotoxicity. 2,14,19 For example, conjugate of non-toxic cytoprotective agent troxipide with dye MHI-148 showed nanomolar cytotoxic activity (EC50 267 nM) on three glioblastoma cell lines. 20 The same dye linked with the renin angiotensin system (Ras) inhibitor S-trans-trans farnesylthiosalicylic acid (FTS) significantly improved specific aggregation of this acid in pancreatic tumor cells.…”

“…Their fluorescent maxima are located in the near infrared (NIR) range (700-1000 nm, NIR-I window), where biological tissues are transparent, 1 thus making them suitable for bioimaging. 2,3 Moreover, most common photodetectors have sensitivity up to 900 nm, 4 thus making NIR-I dyes convenient for widely used bioimaging equipment. The unique photophysical properties of these dyes make them attractive as photosensitizers for photodynamic/photothermal therapy, [5][6][7] including nanoparticle conjugates.…”

Recent Progress in Small Spirocyclic, Xanthene-Based Fluorescent Probes

“…Since then, fluorescein and its plethora of congeners manifested in a new and versatile branch of research [2]. Nowadays there are many different classes of fluorophores, ranging from large fluorescent proteins (i.e., green fluorescent protein (GFP), yellow fluorescent protein (YFP)) [3][4][5] over small fluorescent molecules (i.e., coumarins [6,7], naphtalimides [8][9][10], BODIPYs [11][12][13][14], cyanines [15,16] or fluoresceins/rhodamines [17][18][19][20]) to fluorescent quantum dots [21,22]. Three main classes exist: fluorescein (contains two phenol groups), rhodamine (contains two aniline groups), and rhodol (contains one phenol group and one aniline group) [23].…”