1 research outputs found
Enhanced Release of Molecules upon Ultraviolet (UV) Light Irradiation from Photoresponsive Hydrogels Prepared from Bifunctional Azobenzene and Four-Arm Poly(ethylene glycol)
Advances
in biosensors and drug delivery are dependent on hydrogels that respond
to external stimuli. In this work, we describe the preparation and
characterization of photoresponsive hydrogels prepared by cross-linking
of di-NHS ester of azobenzoic acid and four-armed, amine-terminated
polyÂ(ethylene glycol). The porous structure and composition of the
hydrogels were confirmed by scanning electron microscopy (SEM) and
Fourier transform infrared (FTIR) spectroscopy. The reversible photoisomerization
of the azobenzene-containing hydrogel cross-linkers in the gels was
confirmed by absorption spectroscopy. Specifically, the photoisomerization
of the cross-linkers between their <i>trans</i> and <i>cis</i> configurations was observed by monitoring the absorbance
of the hydrogels at the two characteristic peaks of azobenzene (π–π*
at 330 nm and <i>n</i>–π* at 435 nm). The effect
of photoisomerization on the hydrogel structure was investigated by
microscopy. Ultraviolet (UV) irradiation-induced reduction in hydrogel
size was observed, which may be a result of the inherently smaller
footprint of the <i>cis</i> azobenzene conformation, as
well as dipole–dipole interactions between the polar <i>cis</i> azobenzene and the polymer network. The UV-triggered
reduction in hydrogel size was accompanied by enhanced release of
the near-infrared fluorescent dye Alexa Fluor 750 (AF<sub>750</sub>). Enhanced release of AF<sub>750</sub> was observed in samples irradiated
with UV versus dark control. Together, these data demonstrate the
potential of these systems as reversible photoresponsive biomaterials