Exploring the Safety and Efficacy of Organic Light-Emitting Diode in Skin Rejuvenation and Wound Healing

Abstract

Purpose: Photobiomodulation (PBM), encompassing low-energy laser treatment and light-emitting diode (LED) phototherapy, has demonstrated positive impacts on skin rejuvenation and wound healing. Organic light-emitting diodes (OLEDs) present a promising advancement as wearable light sources for PBM. However, the biological and biochemical substantiation of their skin rejuvenation and wound healing effects remains limited. This study aimed to ascertain the safety and efficacy of OLEDs as a next-generation PBM modality through comprehensive in vitro and in vivo investigations.

Materials and methods: Cell viability assays and human ex vivo skin analyses were performed after exposure to OLED and LED irradiation to examine their safety. Subsequent evaluations examined expression levels and wound healing effects in human dermal fibroblasts (HDFs) using quantitative reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, and wound healing assays post-irradiation. Additionally, an in vivo study was conducted using a ultra violet (UV)-irradiated animal skin model to explore the impact of OLED exposure on dermal collagen density and wrinkles, employing skin replica and tissue staining techniques.

Results: OLED irradiation had no significant morphological effects on human skin tissue, but caused a considerably higher expression of collagen than the control and LED-treated groups. Moreover, OLED irradiation reduced the expression levels of matrix metalloproteinases (MMPs) more effectively than did LED on HDFs. OLED irradiation group in HDFs had significantly higher expression levels of growth factors compared to the control group, but similar to those in the LED irradiation group. In addition, OLED irradiation on photo-aged animal skin model resulted in increased collagen fiber density in the dermis while reducing ultra violet radiation-mediated skin wrinkles and roughness, as shown in the skin replica.

Conclusion: This study established comparable effectiveness between OLED and LED irradiation in upregulating collagen and growth factor expression levels while downregulating MMP levels in vitro. In the UV-irradiated animal skin model, OLED exposure post UV radiation correlated with reduced skin wrinkles and augmented dermal collagen density. Accelerated wound recovery and demonstrated safety further underscore OLEDs' potential as a future PBM modality alongside LEDs, offering promise in the realms of skin rejuvenation and wound healing.

Keywords: Organic light-emitting diode; light-emitting diode; photobiomodulation; skin rejuvenation; wound healing.

Fig. 1. Safety assessment of OLED and LED light irradiation of human skin cells and human skin tissue. Safety assessments of OLED and LED light irradiation on human skin cells were performed by confirmation of cell viability (A and B). Except for the 9 J/cm² OLED light irradiation after 48 h of incubation on HDF cells and 9 J/cm² LED light irradiation after 24 h of incubation on KC cells, all results of light irradiation had a positive effect. There were no histological variations in the human skin tissue after OLED or LED light irradiation (C). ^*p<0.05, independent samples t-test. Scale bar: 200 µm. HDF, human dermal fibroblast; H&E, hematoxylin and eosin; KC, keratinocyte; LED, light-emitting diode; M-T, Masson’s trichrome; OLED, organic light-emitting diode.

Fig. 2. Comparison of concentrations of PIP1 α1 and MMP1 and mRNA expression levels of COL1A1, MMP1, and MMP3 after OLED and LED light irradiation. The 6 J/cm² OLED light irradiation significantly induced COL1A1 mRNA expression (A) and PIP1 α1 production (D). The 6 J/cm² LED light irradiation significantly induced MMP1 (B) and MMP3 (C) mRNA expression and MMP1 production (E), whereas the 6 J/cm² OLED light irradiation significantly reduced MMP3 mRNA expression and MMP1 production. ^*p<0.05, ^**p<0.01, ^***p<0.005, independent samples t-test. PIP1 α1, pro-collagen I α1; MMP, matrix metalloproteinase; OLED, organic light-emitting diode; LED, light-emitting diode; HDF, human dermal fibroblast.

Fig. 3. Wound recovery effect of OLED and LED light irradiation on the HDF cells. In comparison with the control group, wound recovery was induced via 6 J/cm² OLED or LED light irradiation on HDF cells (A and B). ^*p<0.05, ^***p<0.005, independent samples t-test. Scale bar: 200 µm. OLED, organic light-emitting diode; LED, light-emitting diode; HDF, human dermal fibroblast.

Fig. 4. Relative mRNA expression levels confirm growth factor gene expressions, such as VEGFα, FGF2, and FGF7, in the HDF cells via quantitative reverse transcription polymerase chain reaction. The VEGFα and FGF2 mRNA expressions were significantly induced by 6 J/cm² OLED or LED light irradiation on HDF cells (A and B). The 6 J/cm² OLED light irradiation induced more FGF7 mRNA expression than 6 J/cm² LED light irradiation (C). ^***p<0.005, independent samples t-test. HDF, human dermal fibroblast; LED, light-emitting diode; OLED, organic light-emitting diode.

Fig. 5. Improvement effects of OLED irradiation regarding the collagen fiber density (A and B) and the skin surface roughness (C and D) on the mice’s skin. The OLED irradiation on photo-aged mouse skin affected the improvement of collagen fiber density and the reduction of skin roughness depending on the energy of OLED irradiation. ^*p<0.05, ^**p<0.01, ^***p<0.005, independent samples t-test compared with the control group. Scale bar indicates 50 µm. Control, non-treatment; UVB, only UVB irradiation; 6 J/cm² OLED group, 6 J/cm² OLED treatment after UVB irradiation; 10 J/cm² OLED group, 10 J J/cm² OLED treatment after UVB irradiation; OLED, organic light-emitting diode; M-T, Masson’s trichromel; UVB, ultraviolet B.