Photosensitive microgels containing azobenzene surfactants of different charges

Abstract

We report on light sensitive microgel particles that can change their volume reversibly in response to illumination with light of different wavelengths. To make the anionic microgels photosensitive we add surfactants with a positively charged polyamine head group and an azobenzene containing tail. Upon illumination, azobenzene undergoes a reversible photo-isomerization reaction from a trans- to a cis-state accompanied by a change in the hydrophobicity of the surfactant. Depending on the isomerization state, the surfactant molecules are either accommodated within the microgel (trans-state) resulting in its shrinkage or desorbed back into water (cis-isomer) letting the microgel swell. We have studied three surfactants differing in the number of amino groups, so that the number of charges of the surfactant head varies between 1 and 3. We have found experimentally and theoretically that the surfactant concentration needed for microgel compaction increases with decreasing number of charges of the head group. Utilization of polyamine azobenzene containing surfactants for the light triggered remote control of the microgel size opens up a possibility for applications of light responsive microgels as drug carriers in biology and medicine.

Photosensitive nanocarriers for specific delivery of cargo into cells

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Functional Microgels: Recent Advances in Their Biomedical Applications

“…The influence of this stimulus can be simply tuned without any contact by changing the wavelength, polarization direction and intensity . Taking advantage of this, a wide variety of chromophores including spiropyrans, o ‐nitrobenzyl derivatives, and azobenzene have been utilized to develop light‐sensitive polymers . Recently, increasing attempts have been made to synthesize microgel systems with chromophores included in their network to explore the potential of light stimulus for drug delivery applications …”

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