News
July 28, 2022

Mimicking brain tissue with 3D printing
opens up a new path in cancer proton therapy

3D biocompatible scaffolds cultured with glioblastoma cells are exposed to proton beams to assess their response to irradiation
3D biocompatible scaffolds cultured with glioblastoma cells are exposed to proton beams to assess their response to irradiation. Compared to 2D cell monolayers, 3D brain cancer cell networks exhibit a lower amount of DNA damage. The scaffolds are 3D-printed by Nanoscribe’s Two-Photon Polymerization technology. Image: See citation below this piece of news.

In vitro models offer a platform to assess cancer cells response to drugs and radiation. However, standard 2D monolayer cell cultures have their limitations, as they are not able to mimic in vivo 3D environments naturally occurring in the body. In the search for more realistic models, scientists at the Delft University of Technology develop 3D engineered cellular microenvironments by using Nanoscribe’s 3D printers. For the first time, 3D-printed scaffolds with cultured glioblastoma cells are investigated in the context of proton beam radiation experiments to study their response to irradiation. Impressively, the results show a significant lower DNA damage in 3D-engineered cell cultures as compared to 2D cell monolayers.

Cancer is one of the main causes of death worldwide with almost 10 million deaths occurred in 2020 [1]. Glioblastoma is a devastating cancer of the brain whose cancer cell proliferation is very fast and aggressive. To study, treat and destroy brain tumor cells, researchers are investigating proton beam radiation which has proven to be a more effective and minimal invasive technique than x-ray radiotherapy in different cancer types. However, the costs of proton beam therapy are high, which makes the testing in animals and humans also very costly and almost inaccessible. The higher costs in proton radiotherapy also lead to a lack of clinical studies to understand the effects of protons on glioblastoma at the cellular level.

Biomimetic cellular scaffolds by 3D printing

Scientists at the Delft University of Technology led by Professor Angelo Accardo tackle the challenge with a promising novel approach to study in vitro glioblastoma cell cultures under proton beam radiation, featuring the cover of ACS Applied Materials & Interfaces. They develop in vitro cell cultures made of 3D engineered cellular microenvironments. For this purpose, they use Two-Photon Polymerization (2PP) to fabricate biomimetic 3D scaffolds that mimic the geometry of brain blood vessels. The biomimetic geometry affects the glioblastoma cells and their colonization mechanics. In these experiments, the 3D cell culture is scaffold-based and thus cells can grow in a controlled manner guided by a scaffold geometry in 3D. The very confined photopolymerization by 2PP occurring only in the tight laser focus allows to 3D-print finest features in the submicrometer range. Moreover, this additive manufacturing technology exploits the full 3D design freedom at the micrometer scale and is relevant for mimicking 3D cellular microenvironments with the highest precision.

In this project, cellular scaffolds with only 150 micrometers height are 3D-printed. The scaffolds include an octagonal base and a top octagonal layer similar to the bottom one in a smaller size, forming octagonal truncated pyramids. Confocal microscopy benefits from the truncated pyramids that allow analyzing a quantitatively large amount of cells, while SEM images show more details on the cell morphologies associated with the geometry of the scaffolds. In the 3D microenvironment, the cells often adopt a more spherical form than on 2D pedestals. The pyramids include horizontal and inclined beams, with diameters of 10 and 6 µm, that meet pretty well the cellular scale. The beams provide regions for cell adhesion and mechanical stability to avoid the scaffold to collapse under cellular mechanical stimulation. The 3D cellular culture is characterized by the cytoskeleton that is extended from the cells in the directions of the beams of the scaffold. While on 2D pedestals the cells form unrealistic cellular flat monolayers, the cells on the 3D microenvironments colonize the inner core of the scaffolds as well as the outer framework of the architecture.

Dedicated biomaterial for cell culture, growth, adhesion and microscopy

The scaffolds are made of Nanoscribe’s IP-Visio photoresin, which is a non-cytotoxic material according to ISO-10993-5. This biomaterial is beneficial for cell biocompatibility, growth and adhesion of glioblastoma cells. Furthermore, IP-Visio has a negligible autofluorescence that does not interfere with cell staining when used for cell microscopy. Thus, IP-Visio is suitable for immunofluorescence imaging of cell biomarkers. For the use of IP-Visio in this particular cell application, there was no need for additional biofunctionalization or biochemical coating, as the material promoted the required cell adhesion on the structures.

Moreover, IP-Visio’s Young’s modulus measured on 2D pedestals is 1.31 GPa, almost 50 times lower than the Young’s modulus of conventional soda-lime glass substrates (E ≈ 70 GPa) that are typically used for cell cultures. Although it is still far from the Young’s modulus of the brain extracellular matrix, IP-Visio provides a rather soft environment that stimulates cell-cell and cell-scaffold interactions and very clearly different cellular morphologies on 2D and 3D microenvironments. Thus, the combination of Nanoscribe’s Two-Photon Polymerization and IP-Visio paves the path to engineer intricate biomimetic environments made of a cell-friendly biomaterial that can provide mechanical, biochemical and geometric stimuli to cells.

Exploring cancer cell behavior in proton therapy

Using the capabilities of high-precision 3D printing and a suitable biomaterial, 3D-engineered scaffolds are fabricated and used as glioblastoma microenvironments. After sterilization of the scaffolds, glioblastoma cells are cultured on the scaffolds for 5 days. The same procedure is repeated for 2D pedestals for comparison purposes. After this time, the cells-colonized scaffolds undergo exposure to proton beam radiation. Upon proton irradiation, confocal microscopy was used to analyze the cells on the 2D pedestals and 3D microenvironments before and after proton radiation. In the confocal images, a fluorescent biomarker (Gamma H2A.X) revealed the formation of a higher number of DNA damage foci in cells on 2D pedestals compared to 3D microenvironments. The number of foci is related to the DNA damage in a cell, confirming a lower DNA damage of glioblastoma cells in 3D cell cultures than in 2D cell monolayers, which correlates with the response of glioblastoma cells in vivo.

GIF of the design and 3D-print of the microscopic scaffold fabricated by Nanoscribe’s Two-Photon Polymerization.
Design and 3D-print of the microscopic scaffold fabricated by Nanoscribe’s Two-Photon Polymerization. Image: See citation below this piece of news.
SEM image of a glioblastoma 3D cellular network on 3D-printed scaffolds
SEM image of a glioblastoma 3D cellular network on 3D-printed scaffolds. Image: TU Delft.
Confocal images depict the 3D glioblastoma cell culture (left) colonizing the entire structure and the 2D flat cellular monolayer (right).
Confocal images depict the 3D glioblastoma cell culture (left) colonizing the entire structure and the 2D flat cellular monolayer (right). Image: See citation below this piece of news.
The fluorescent biomarker Gamma H2a.X (green) reveals more foci in the cells (nuclei in blue) on 2D pedestals (upper images) than in 3D scaffolds (lower images), confirming a lower DNA damage in 3D cell cultures than in 2D monolayers.
The fluorescent biomarker Gamma H2a.X reveals more foci (in green) in the cell nuclei (in blue) on 2D pedestals (upper images) than in 3D scaffolds (lower images), confirming a lower DNA damage in 3D cell cultures than in 2D monolayers. Images show cell cultures prior (control) and after radiation at different dose (2 Gy, 8 Gy). Image: See citation below this piece of news. The image was brightened.

These findings could be related to a difference in the radioresistance of glioblastoma cells or in the repair kinetics between 2D cell monolayers and 3D cell networks. The novel 3D microenvironments are a promising benchmark tool that can serve to study the effects of proton beam therapy on glioblastoma cells and other types of cancer cells.

 

Are you interested to read the scientific publication about 3D-engineered cancer cell microenvironments? Find the open-access publication here: Evaluation of Proton-Induced DNA Damage in 3D-Engineered Glioblastoma Microenvironments

This and further scientific publications on more than a thousand research projects from Nanoscribe customers and system users can be found in a powerful database with a keyword search in the Premium Resources section. Register for free to see for yourself the potential of Nanoscribe’s 3D Microfabrication technology for innovative applications and fundamental innovations in many areas, and to evaluate its suitability for your project.

 

[1] Global Cancer Statistics 2020

Image source: CC by 4.0 Qais Akolawala et al., ACS Appl. Mater. Interfaces 2022, 14, 18, 20778–20789, doi: 10.1021/acsami.2c03706. The images were adapted for the required formats.

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