Pattern analysis of 532- and 1,064-nm picosecond-domain laser-induced immediate tissue reactions in ex vivo pigmented micropig skin

Hee Chul Lee,Jumi Hong,Sung Bin Cho,Jinyoung Park,Hye Jin Chung,James Childs

doi:10.1038/s41598-019-41021-7

Abstract

Optical pulses from picosecond lasers can be delivered to the skin as single, flat-top beams or fractionated beams using a beam splitter or microlens array (MLA). In this study, picosecond neodymium:yttrium aluminum garnet laser treatment using a single flat-top beam and an MLA-type beam at the wavelengths of 532 nm and 1,064 nm were delivered on ex vivo genotype-regulated, pigmented micropig skin. Skin specimens were obtained immediately after treatment and microscopically analyzed. Single flat-top beam treatment at a wavelength of 532 nm and a fluence of 0.05-J/cm2 reduced melanin pigments in epidermal keratinocytes and melanocytes, compared to untreated controls. Additionally, 0.1 J/cm2- and 1.3 J/cm2-fluenced laser treatment at 532 nm elicited noticeable vacuolation of keratinocytes and melanocytes within all epidermal layers. Single flat-top beam picosecond laser treatment at a wavelength of 1,064 nm and a fluence of 0.18 J/cm2 also reduced melanin pigments in keratinocytes and melanocytes. Treatment at 1,064-nm and fluences of 1.4 J/cm2 and 2.8 J/cm2 generated increasing degrees of vacuolated keratinocytes and melanocytes. Meanwhile, 532- and 1,064-nm MLA-type, picosecond laser treatment elicited fractionated zones of laser-induced micro-vacuolization in the epidermis and dermis. Therein, the sizes and degrees of tissue reactions differed according to wavelength, fluence, and distance between the microlens and skin.

Highlights

Optical pulses from picosecond lasers can be delivered to the skin as single, flat-top beams or fractionated beams using a beam splitter or microlens array (MLA)
A previous multiphoton microscopy study provided laser scanning microscopic images of in vivo human skin treated by 532-nm and 1,064-nm picosecond neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers using a holographic diffractive beam splitter, and suggested pigment chromophores as the main absorber for initiating the generation of laser-induced tissue breakdown[4]. In this observational descriptive study, we evaluated the patterns of immediate tissue reactions induced by 532- and 1,064-nm picosecond laser treatment in ex vivo genotype-regulated, pigmented micropig skin
The untreated ex vivo pigmented micropig skin in our study exhibited the characteristic layers of the epidermis, including the stratum corneum in a basket-weave pattern, the stratum spinosum with pigmented, polyhedral keratinocytes, the stratum basalis with darkly and homogeneously pigmented keratinocytes and melanocytes, and an intact basement membrane (BM) (Fig. 1a)

Summary

Introduction

Optical pulses from picosecond lasers can be delivered to the skin as single, flat-top beams or fractionated beams using a beam splitter or microlens array (MLA). A previous multiphoton microscopy study provided laser scanning microscopic images of in vivo human skin treated by 532-nm and 1,064-nm picosecond neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers using a holographic diffractive beam splitter, and suggested pigment chromophores as the main absorber for initiating the generation of laser-induced tissue breakdown[4]. In this observational descriptive study, we evaluated the patterns of immediate tissue reactions induced by 532- and 1,064-nm picosecond laser treatment in ex vivo genotype-regulated, pigmented micropig skin. We compared the patterns of tissue reactions between nanosecond and picosecond Nd:YAG lasers using a single flat-top beam

Methods

Results

Conclusion