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Biocompatibility studies of optical stimulation via 532nm-Laser pulses on human FibroblastsThis research has been funded by the European Research Council under the European Union's Seventh Framework Program (FP/2007 – 2013)/ERC Grant, LaserHearingAids: 311469
18 April 2018 (online)
The optical stimulation of vibratory biological structures within the hearing organ offers a promising technology for a new generation of auditory prostheses. For the clinical use of laser-based hearing systems, biocompatibility is an essential requirement.
In order to define the biocompatibility margins for the optoacoustic stimulation we irradiated “Normal Human Dermal Fibroblasts” (NHDF) in an in vitro-cell culture model. 532nm laser pulses were applied over a period of 2 minutes using our novel laser pulse amplitude modulation strategy. Following the irradiation, we assessed cell-viability (WST-1-Assay) and performed cytotoxicity testing (LDH-Assay) as well as fluorescence staining, in order to distinguish between necrotic, apoptotic and healthy cells. After the irradiation we performed further qPCR-analysis regarding the expression of 84 key player-genes for cytotoxicity and stress-response.
After irradiation with 199mW no significant cytotoxicity could be identified. However, after irradiation with 223mW cytotoxic effects due to laser-irradiation could be observed. Following the irradiation with a laser power of 199mW, being a level below the cytotoxic threshold, our qPCR-analysis revealed a significant up-regulation of the stress-responsive gene GADD45G.
Our in-vitro data suggest that the first biocompatibility margin for our stimulation parameters can be found between 200mW and 223mW. Further studies are necessary to define the optimal parameters for the optoacoustic stimulation taking into account the up-regulation of the stress-responsive gene GADD45G as well.