Title : Bioprinted cell gradients to analyze nanoparticle uptake variability
Abstract:
Physical and chemical gradients in the human body are crucial for tissue development, function, and pathology. Replicating these gradients in in-vitro designs is essential to tissue engineering and disease research.
The aim of this study is to design cell gradients using a bioprinting approach for investigating how different cell densities affect the interactions with nanoparticle-based drug delivery systems.
A cell gradient system using a 3D bioprinter (3DDiscovery, RegenHu) was produced by "drop-on-demand" (DoD) technology using lung epithelial cells (A549). After two days in culture, these cells were exposed to fluorescent silica nanoparticles (SiO2-NPs, 20 mg/ml, 119±10 nm in diameter) for different time points. The level of NP uptake, cell dimensions, i.e., surface and volume, and cell density were assessed at 6h, 24h, and 48h using confocal laser scanning microscopy (cLSM) and subsequent data analysis with Imaris software.
Live/dead cell imaging confirmed that lung epithelial cells remained viable across the gradients. The gradients maintained a stable correlation between cell number and spatial distribution during the observation time with ongoing cell division. Results indicated a 1.5- to 2-fold increase in SiO2 NP uptake by cells grown at low density relative to those at high density across all time points. Additionally, our study showed both cell surface area and cell volume varying proportionally with NP uptake, indicating that cell surface and volume significantly influence the behavior of cells in relation to NP endocytosis. These results have shown that lung epithelial cell gradients can be reproducibly fabricated by 3D bioprinting technology. Moreover, cell density significantly impacts NP uptake, emphasizing the significance of accounting for varying cell densities at the intended site of nanoparticle delivery. This consideration is crucial when evaluating the efficacy of nanoparticle-based therapies in pathological conditions such as in tumor microenvironments, during infections, and in cases of chronic inflammation.
Audience Take Away Notes:
- Standard cell seeding methods (e.g., pipetting) do not allow the precise control of cells’ density and distribution in a plastic well or cell culture inserts
- The design of bioprinted cell gradients provides the opportunity of replicating the microenvironment in situ with applications in tissue engineering and nanomedicine
- Exploiting the benefits of precise cell arrangement in biological research setups will support the design of physiologically relevant tissue systems, thus producing more translatable results
