The light Dwarf: Chemiluminescent Poly(2-oxazoline) as a reactive oxygen Species-triggered material for bioimaging and drug delivery

Luminol (3-aminophthalylhydrazide) is a known example of a chemiluminescent material. In the presence of reactive oxygen species (ROS, hydrogen peroxide), luminol transforms to amino phthalic acid with an emission of blue light (λ_max ≈ 425 nm). The high sensitivity of this reaction determines the effectiveness of the luminol chemiluminescence in bioimaging for the detection of reactive oxygen species. Here we report on the first chemiluminescent poly(2-oxazoline)s, bearing luminol units. Using the post-polymerization modification strategy based on the direct grafting of the luminol via imine formation with subsequent reduction, we created a library of block-copolymers with a variable luminol content. Chemiluminescence emission studies confirm the high sensitivity of the obtained copolymers to the reactive oxygen species (H₂O₂) in aqueous solution, comparable to free luminol. Solution behaviour studies revealed the tendency of the obtained copolymers to form nanoparticles, which was confirmed by a combination of dynamic light scattering and transmission electron microscopy. Apart from expected sensitivity to ROS, the obtained copolymers show pH-responsive behaviour, which was also confirmed by DLS. Finally, all chemiluminescent poly(2-oxazolne)s demonstrated ability to encapsulate hydrophobic drugs, forming colloidally stable solutions. The obtained results highlight the potential of the obtained luminol-containing polymers for biomedicine.