Effective photoinitiating systems using citric acid-derived chromophores as photosensitizers for 3D bio-printing applications

The growing interest in the use of naturally derived compounds, associated with the increasing focus on green chemistry principles in various fields of chemical technology, is also evident in the development of light-cured resins for 3D printing. Therefore, in this work, four fluorophores formed alongside carbon dots as one of the products of the reaction between citric acid and specific β-amines were comprehensively studied. These studies facilitated the detailed optical characterization of the compounds, which in turn led to a better understanding of the electron transfer mechanisms accompanying the initiation of photopolymerization processes. In addition, cyclic voltammetry and photostability studies enabled a preliminary assessment of the applicability of the fluorophores as photosensitizers of commercially available diphenyl iodonium salts (SpeedCure 938®). FT-IR analyses and supporting photorheology measurements made it possible to determine the kinetics of the photopolymerization process and demonstrate the influence of the water content (non-reactive agent) on its course. Finally, it was possible to develop resins for 3D printing with low viscosity for use in the stereolithography (SLA) method and high viscosity for use in the direct ink writing (DIW) method enriched with light-curing of the finished pattern.