Combinations of photoinitiator and UV absorber for cell-based digital light processing (DLP) bioprinting

Abstract

Digital light processing (DLP) bioprinting, which provides predominant speed, resolution, and adaptability for fabricating complex cell-laden three-dimensional (3D) structures, requires a combination of photoinitiator (PI) and UV absorber (UA) that plays critical roles during the photo-polymerization of bioinks. However, the PI and UA combination has not been highlighted for cell-based DLP bioprinting. In this study, the most used PIs and UAs in cell-based bioprinting were compared to optimize a combination that can ensure the maximum DLP printability, while maintaining the cellular activities during the process. The crosslinking time and printability of PIs were assessed, which are critical in minimizing the cell damage by the UV exposure during the fabrication process. On the other hand, the UAs were evaluated based on their ability to prevent the over-curing of layers beyond the focal layer and the scattering of light, which are required for the desirable crosslinking of a hydrogel and high resolution (25–50 µms) to create a complex 3D cell-laden construct. Lastly, the cytotoxicity of PIs and UAs was assessed by measuring the cellular activity of 2D cultured and 3D bioprinted cells. The optimized PI and UA combination provided high initial cell viability (>90%) for up to 14 days in culture and could fabricate complex 3D structures like a perfusable heart-shaped construct with open vesicles and atriums. This combination can provide a potential starting condition when preparing the bioink for the cell-based DLP bioprinting in tissue engineering applications.

Next Evolution in Organ‐Scale Biofabrication: Bioresin Design for Rapid High‐Resolution Vat Polymerization

“…[12] Ponceau 4R (red food dye) was studied by Lim et al [44] demonstrated that addition of 1 wt% of the absorber was suitable for a poly(vinyl alcohol)-methacrylate (PVA-MA) resin, allowing improved control over print resolution. Other widely used photoabsorbers are 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (HMBS) [172,175,176] and TINUVIN 234. [174] HMBS is an attractive photoabsorber used in biomedical applications as it is an FDA approved chemical used in sunscreen and cosmetic products.…”

In vitro models for head and neck cancer: Current status and future perspective

“…Digital light processing bioprinting technology has enhanced the resolution (~10 times) of bioprinted PDOs, which has been one notable barrier with nozzle extrusion ( 159 – 162 ). In addition, digital light processing bioprinting offers a shear stress–free advantage over extrusion bioprinting by reducing potential cell damage during organotypic assembly ( 66 , 158 , 162 ). This shear stress–free printing method achieves a cell viability of ≥90% within the 3D-printed construct, whereas that of extrusion bioprinting is 40%–80% ( 66 ).…”

Improving Printability of Digital-Light-Processing 3D Bioprinting via Photoabsorber Pigment Adjustment

“…When a photoinitiator is exposed to the light energy of a reactive wavelength, it generates free radicals that initiate photopolymerization with the polymer in the bioink [ 16 , 17 ]. However, LAP is suited for the absorption of UV and blue-light wavelengths (350–400 nm); the UV absorption range has been known to negatively affect cell behavior and generate excessive heat [ 18 , 19 ]. In addition, the relatively wide absorption wavelengths of bioinks are often incompatible with the wavelength band of the commercially available printer projection light; this may affect printability.…”

“…Conversely, excessive light exposure energy causes light to penetrate beyond the focal layer, resulting in over-crosslinking, which leads to an undesired shape. Recently, a multi-hollow channel test was employed to assess over-crosslinking in DLP bioprinting [ 19 ]. However, to calculate the optimal amount of exposure energy in this method, a trial-and-error process, comprising the modification of light exposure energy for different condition values, is essential.…”