Spectrophotometric determination of LAP photoinitiator radicalization in ophthalmic applications

The incidence of lamellar corneal transplantations is increasing. While a
human donor cornea could potentially be used for up to two recipients, one
anterior and one posterior part, it does not change the disparity between
available donor grafts and patients needing corneal transplants.
Additionally, donor grafts carry the risk of graft rejection due to
foreign cellular material and disease transmission. We have investigated
acellular synthetic graft materials to eliminate these drawbacks using
hydrogel materials and the extrusion bioprinting process. To create these
materials with higher moduli, the photocrosslinking process has advantages
but needs an appropriate crosslinker material. We have shown that we can
determine the presence of the non-radicalized crosslinker Lithium Phenyl
(2,4,6-Trimethylbenzoyl) Phosphinate (LAP) with spectrophotometric
methods, using the crosslinker absorbance characteristics. To show
non-radicalized LAP, the measurement is done at 372 nm, and the measured
absorbance level depends on the LAP concentration. This allows for a
simple evaluation of crosslinked hydrogels to determine any remaining non
radicalized LAP and with that potential cytotoxic or other effects of this
crosslinking material and correct this situation if necessary.