Facile approach to the solid support photografting coating of citric acid as a novel biomimetic iron chelator film

Herein, the facile photografting coating method was used to develop a novel metal biochelator film by covalent immobilization of citric acid (CA) onto polypropylene (PP) surface. First, PP film underwent a surface modification by UV-grafting of glycidyl methacrylate (GMA) in the presence of benzophenone (BP). The concentrations of GMA (bifunctional monomer) and BP (photoinitiator) were appropriately optimized to achieve the breath-figure-array structure and brush-like grafting configuration with a high availability of the reactive oxirane ring. Subsequently, CA was immobilized onto the PP-g-GMA surface via the ring-opening reaction to obtain the biochelator film (PP-g-GMA-g-CA). Fourier-transform infrared spectroscopy and solid state ¹³C nuclear magnetic resonance spectroscopy elucidated the chemical structure and grafting mechanism of grafted samples. X-ray photoelectron spectroscopy was used to detect the chemical composition of the surface of the grafted samples, by which the grafting density was relatively estimated. In addition, the uniformity of the grafting pattern and morphology of the grafting unit were observed using scanning electron microscopy and atomic force microscopy. Furthermore, the carboxylic acid density of the biochelator film (PP-g-GMA-g-CA) was quantified using a toluidine blue O assay, in which approximately 327 ± 58 nM carboxylic acid was detected per each film. The metal chelating activity of the film was also investigated using the colorimetric ferrozine assay, by which PP-g-GMA-g-CA film chelated approximately 215 ± 11 nM of Fe³⁺. Therefore, this newly developed system can be used as a versatile metal biochelator in a wide range of biomedical, cosmetic, and packaging applications.¹