Abstract
Light is a non-invasive tool that is widely used in a range of biomedical applications. Techniques such as photopolymerization, photodegradation, and photouncaging can be used to alter the chemical and physical properties of biomaterials in the presence of live cells. Long-wave UV light (315 nm–400 nm) is an easily accessible and commonly used energy source for triggering biomaterial changes. Although exposure to low doses of long-wave UV light is generally accepted as biocompatible, most studies employing this wavelength only establish cell viability, ignoring other possible (non-toxic) effects. Since light exposure of wavelengths longer than 315 nm may potentially induce changes in cell behavior, we examined changes in gene expression of human mesenchymal stem cells exposed to light under both 2D and 3D culture conditions, including two different hydrogel fabrication techniques, decoupling UV exposure and radical generation. While exposure to long-wave UV light did not induce significant changes in gene expression regardless of culture conditions, significant changes were observed due to scaffold fabrication chemistry and between cells plated in 2D versus encapsulated in 3D scaffolds. In order to facilitate others in searching for more specific changes between the many conditions, the full data set is available on Gene Expression Omnibus for querying.
Highlights
Light is a stimulus widely used in the presence of cells for biotechnology applications employing photo-chemistries
Using Principle Components Analysis (PCA), we obtain a global view of the data that suggests UV exposure does not play an important role in gene expression changes relative to other experimental conditions (Fig 2)
Culture method (2D vs. 3D) and polymerization method (3DC vs. 3DR) are the greatest determinants of gene expression, and exposure to UVA light has little to no effect on gene expression of human mesenchymal stem cells (hMSC), regardless of culture or polymerization method
Summary
Light is a stimulus widely used in the presence of cells for biotechnology applications employing photo-chemistries. A filtered light source emits a controlled wavelength and intensity of light to trigger an environmental change affecting in vitro cultured cells. It is generally accepted that the shorter the wavelength (higher energy), the less compatible light may be with living systems. Visible (400–700 nm) and infrared (700 nm to 1 mm) wavelengths typically do not interact with intracellular components, prolonged exposure may generate heat depending on the light source[1]. UV light can be divided into three categories: UVA (315–400 nm), UVB (280–315 nm) and UVC (100–280 nm). UVB and UVC light are capable of inducing direct DNA damage and are often used for sterilization[2,3,4,5], while UVA may induce
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