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Tissue Engineering

Tissue Engineering - Poster Session D

Poster K19 - Optimizing Wound Healing Protocols using the Einstein Dosimetry for Photobiomodulation Therapy

Friday, October 25, 2024
3:30 PM - 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Skin healing primarily involves epithelial cell migration leading to wound closure. The ability to accelerate healing shortens recovery periods, reduces complications, and improves functional recovery. The use of low-dose light therapy, termed Photobiomodulation (PBM) has been noted to improve wound healing in several studies. Traditional PBM dosing involves fluence (J/cm2), irradiance (mW/cm2), and treatment duration (sec). However, it does not account for the wavelength-specific energy. Due to the Arndt-Schultz dose effect, this may result in suboptimal responses and reduced effectiveness. Although the low levels of light used in PBM are expected to cause no harm, it is becoming increasingly evident that conventional PBM practices routinely exceed these dose thresholds and could be negating their benefits. For improved dose accuracy, we propose including the wavelength-specific photon energy termed Photonic Fluence and harmonization reference standard termed Einstein. This study aims to optimize the clinical PBM protocol using the in vitro keratinocytes normal wound scratch healing model. Further, we have been exploring the generation of various compromised wound conditions such as hyperglycemia (Diabetic), Hypoxia, low Serum (stress), Infections, Burns, Cryoinjury, and laser wounds.

Materials and

Methods:  We obtain Einstein dosing by dividing the specific photon fluence by 4.5 to get harmonized universal dosing, regardless of wavelength. For instance, an 810 nm laser operating at 3 J/cm³ (fluence) and 1.5 eV (individual photon energy) yields 4.5 p.J/cm² (photon fluence), or one 1 Einstein (Figure1). Human keratinocytes were grown in confluent monolayers, and a wound scratch assay was performed. Various PBM wavelengths, namely, 450 nm, 490 nm, 560 nm, 660 nm, 810 nm, 940, and 1064 nm at discrete doses, were used. Besides standard PBM dosimetry (irradiance x time), dose equivalents were calculated using photonic fluences and Einstein to account for individual wavelength photon energy (eV) precisely. Wound area at the beginning (T0), 3 hours (T3), 6 hours (T6). and 9 hours (T9) were digitally documented and quantitated using NIH Image J. To assess individual PBM mechanisms, pre-incubation with Sodium Azide (ATP), N-Acetyl Cysteine (ROS), SB431542 (Alk5 Inhibitor), or recombinant TGF-β1 was performed. The compromised wound types are currently being investigated. Wound cross-sectional area was assessed using ANOVA among experimental groups compared to controls.

Results, Conclusions, and Discussions: Treatments with 810 nm (1 Einstein, positive control) demonstrated clear improvements (n = 3, p < 0.05) over untreated control wounds. Our results indicate that the adjusted (Einstein) dose for 450 nm (Blue-Violet) and 560 nm (Yellow-Green) wavelengths significantly improved (n = 3, p < 0.05) wound closure compared to their unadjusted and untreated group (Figure 2). Other wavelengths showed moderate to mild changes that were not statistically significant. Mechanistic studies examining the effect of specific PBM signaling pathways implicated in the therapeutic responses namely, ATP, ROS, and TGF-β1 using both gain-of-function (agonists) or loss of function (inhibition) approaches have been successfully conducted. The seven compromised wound models were successfully standardized (n = 3, p < 0.05). Ongoing tests are evaluating PBM responses for each wound type.

Our results suggest that utilizing the appropriate wavelength-adjusted PBM treatments can optimally promote keratinocyte migration for wound closures. Investigating PBM response in compromised wound conditions could provide insights into specific wound management approaches. Further mechanistic insights into these precise cell-specific, dose-responsive biological responses hold much promise for the clinical translation of PBM. The precise, low-cost, sustainable, non-invasive approach PBM offers appears to be poised to significantly impact healthcare, reassuring us of the practicality and affordability of this therapy.

Acknowledgements (Optional):