Photo-controlled release of metal ions using triazoline-containing amphiphilic copolymers

Abstract

Photo-controlled release that shows a quick response and high spatial/temporal accuracy has become attractive given its potential applications for biomedicines. A few metal complexes are known for their uses in detoxification, sterilization, and diagnosis and treatment of diseases, but, the encapsulation and controlled release of those metal ions using polymer micelles are challenging. We report an interesting photo-controlled release of metal ions via photo-responsive triazoline-containing amphiphilic polymers. Amphiphilic random copolymers of glycidyl methacrylate and oligo(ethylene oxide) methyl ether methacrylate were prepared through free radical copolymerization. The glycidyl pendants were converted to azide, followed by a 1,3-dipolar cycloaddition reaction to form triazoline with norbornene. The resulting random copolymers containing triazoline formed micelles with a critical micellar concentration (CMC) of 7.68 × 10⁻³ mg mL⁻¹. The triazoline moieties could coordinate to transition metal ions, e.g. Co²⁺, and thus encapsulate the metal ions to the core of micelles. Photo-induced denitrogenation of triazoline was able to disrupt the coordination of Co²⁺ and triazoline, therefore leading to the release of Co²⁺. Solution viscosity, UV-vis/NMR spectroscopy and TEM were used to show that the coordination and release of Co²⁺ ions were successful upon exposure to light. The photo-controlled release profile was found to be linearly dependent on the irradiation time, which is potentially useful for the delivery of essential ions in vivo.