Advances in Application of Azobenzene as a Trigger in Biomedicine: Molecular Design and Spontaneous Assembly

Abstract

Azobenzene is a well‐known derivative of stimulus‐responsive molecular switches and has shown superior performance as a functional material in biomedical applications. The results of multiple studies have led to the development of light/hypoxia‐responsive azobenzene for biomedical use. In recent years, long‐wavelength‐responsive azobenzene has been developed. Matching the longer wavelength absorption and hypoxia‐response characteristics of the azobenzene switch unit to the bio‐optical window results in a large and effective stimulus response. In addition, azobenzene has been used as a hypoxia‐sensitive connector via biological cleavage under appropriate stimulus conditions. This has resulted in on/off state switching of properties such as pharmacology and fluorescence activity. Herein, recent advances in the design and fabrication of azobenzene as a trigger in biomedicine are summarized.

Hydrazone Photoswitches for Structural Modulation of Short Peptides

“…[12][13][14][15][16][17][18] Azobenzenes have been particularly highlighted as the most prominent player in the relevant fields due to their several advantages such as easy synthesis, chemical tunability, moderate to high quantum yield, and high photochemical conversion. [19] However, they are prone to be reduced by glutathione, [20] a reducing agent abundant in a cellular environment, and many of them have short thermal half-lives of the metastable cis-isomers. [21] Consequently the long-term use of azobenzenes for biological applications is inherently limited, and chemical modification for fine-tuning of switching properties is often required.…”

Bridging D–A type photosensitizers with the azo group to boost intersystem crossing for efficient photodynamic therapy

“…Since azo-bridging of two molecules of TPA-Th(+) generated an azobenzene structure, the resulting Azo-TPA-Th(+) could respond to UV irradiation by experiencing trans-to-cis isomerization. [46][47][48] According to the theoretical calculations, cis-Azo-TPA-Th(+) should be potentially efficient in fluorescence emission rather than ROS generation. To verify our hypothesis, we studied the photophysical properties of Azo-TPA-Th(+) in phosphate buffered saline (PBS) before and after UV irradiation.…”

Stimuli-responsive cyclodextrin-based supramolecular assemblies as drug carriers

“…[112][113][114][115][116][117][118][119][120][121] Azo is a well-known photoswitch that experiences trans-to-cis and cis-to-trans isomerization upon UV irradiation and visible light irradiation, respectively. [123][124][125] A unique feature of Azo is its photo-responsive inclusion complex formation with CDs. The linear, nonpolar trans-isomer of Azo forms a stable complex with CDs, whereas the polar cis-isomer indicates an extremely weak, if not negligible, interaction with CDs.…”