Developing and analyzing photo-crosslinkable cinnamoyl-modified pullulan hydrogels for drug delivery applications

A hydrogel created by modifying pullulan with cinnamoyl groups (Pul-CM) through an esterification process was developed as an effective vehicle for delivering the well-known drug model, caffeine. Initially, pullulan biopolymer was expanded, followed by the addition of cinnamoyl groups using cinnamoyl chloride. These modifications were confirmed through various spectroscopic and instrumental techniques, verifying their proposed chemical structures. The newly created Pul-CM hydrogel demonstrated the ability to crosslink without initiators when exposed to UV light for sufficient durations. This crosslinking is attributed to the creation of cyclobutane rings that link the pullulan chains via a [2 pi+2 pi] cyclization process facilitated by the cinnamoyl groups' -CH=CH- bonds. The progress of Pul-CM crosslinking was tracked by the reduction in the UV spectral peak associated with the cinnamate groups, followed by an examination of the gel's efficiency and its swelling behavior under UV light. Furthermore, these hydrogel derivatives show significant promise as drug delivery systems, offering adjustable drug release rates by altering the hydrogel's crosslinking level through either cinnamoyl modification or the duration of UV light exposure.