[Zurück]

S. Benedikt, K. Dietliker, H. Grützmacher, M. Markovic, N. Moszner, A. Ovsianikov, R. Liska:
"Characterization and Comparison of Next Generation Water-Soluble Photoinitiators";
Poster: International Conference on Biofabrication 2015, Utrecht, Netherlands; 07.11.2015 - 09.11.2015.

Aim: Cell encapsulation plays a central role in many biofabrication methods. Photopolymerizable hydrogels provide additional advantage of temporal and spatial control of encapsulation process. Such characteristics of a photoinitiator (PI) as its water-solubility, cytocompatibility, spectral sensitivity and initiation efficiency, are vital to its performance and suitability for a particular application. The aim of this study was to identify, characterize and compare a new generation of water-soluble, highly reactive and biocompatible visible light photoinitiators (PIs).
Methods: The monomer 4-acryloylmorpholine (NAM) and the PI / coinitiator Quantacure BPQ (Q-BPQ), methyldiethanolamine (MDEA), Irgacure 2959 (I2959) and APi-180 are commercially available (TCI, Aldrich, 3B Scientific, Ciba and Shenzhen UV-ChemTech respectively) and were used in the highest purities available. Na-TPO and Li-TPO were synthesized according to literature. Na-BAPO and Li-BAPO were received from BASF, where both were synthesized according to published procedures. Absorption properties, solubility, storage stability, cytotoxicity, reactivity and efficiency in double bond conversion (DBC) of these compounds were evaluated.
Results: The solubility is one of the most important characteristics of a PI for use in water based formulations. While the state of the art PI I2959, and its modified version APi-180, suffer from very low solubility, they are substantially outperformed by the new generation MAPO and BAPO PIs. All compounds showed adequate storage stability in neutral, basic and acidic solvents. Viability of cells exposed to different concentrations of PIs was shown to be in a similar range as I2959, widely used for cell encapsulation. However, absorption characteristics and reactivity of novel PIs around 320-500 nm are superior. This difference in efficiency would potentially allow to use lower PI concentrations for cell encapsulation experiments.
Conclusions: In this contribution, we have shown that the MAPO and BAPO salts as next generation water-borne photoinitiators not only show storage stability and biocompatibility in the same range as state of the art photoinitiators, but outperform them by a large margin in solubility and reactivity. Furthermore, it is possible to use the MAPO and BAPO salts as visible light initiators, which is a considerable advantage for applications involving living cells. A practical example of encapsulation of MC3T3 preosteblast cells using I2959 and Li-TPO with 365nm source confirms these conclusions.