Rapid activation of diazirine biomaterials with the blue light photocatalyst

• Main Authors: Djordjevic, Ivan, Wicaksono, Gautama, Šolić, Ivan, Singh, Juhi, Kaku, Tanvi Sushil, Lim, Sierin, Ang, Elwin Wei Jian, Blancafort, Lluís, Steele, Terry W. J.
• Other Authors: School of Materials Science and Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Materials::Biomaterials; Polycaprolactone; Diazirine; Visible Light; Cross-linking; Photocatalysis
• Online Access: https://hdl.handle.net/10356/152662
• Institution: Nanyang Technological University

Carbene-based macromolecules are an emerging new stimuli-sensitive class of biomaterials that avoid the impediments of free radical polymerization but maintain a rapid liquid-to-biorubber transition. Activation of diazirine-grafted polycaprolactone polyol (CaproGlu) is limited to UVA wavelengths that have tissue exposure constraints and limited light intensities. For the first time, UVA is circumvented with visible light-emitting diodes at 445 nm (blue) to rapidly activate diazirine-to-carbene covalent cross-linking. Iridium photocatalysts serve to initiate diazirine, despite having little to no absorption at 445 nm. CaproGlu's liquid organic matrix dissolves the photocatalyst with no solvents required, creating a light transparent matrix. Considerable differences in cross-linking chemistry are observed in UVA vs visible/photocatalyst formulations. Empirical analysis and theoretical calculations reveal a more efficient conversion of diazirine directly to carbene with no diazoalkane intermediate detected. Photorheometry results demonstrate a correlation between shear moduli, joules light dose, and the lower limits of photocatalyst concentration required for the liquid-to-biorubber transition. Adhesion strength on ex vivo hydrated tissues exceeds that of cyanoacrylates, with a fixation strength of up to 20 kg·f·cm2. Preliminary toxicity assessment on leachates and materials directly in contact with mammalian fibroblast cells displays no signs of fibroblast cytotoxicity.