The Impact of Nanotopography on Cellular Metabolic Activities: Multimodal Imaging Reveals New Insights

Academic Background

In the field of biomedicine, the interaction between cells and material surfaces is crucial for studying cell behavior, tissue engineering, and regenerative medicine. Nanoscale surface topography (nanotopography) has been shown to significantly influence cell morphology, adhesion, proliferation, and differentiation. However, how nanotopography regulates cellular metabolic activities through mechanical and geometric microenvironments remains incompletely understood. Cellular metabolism is central to cell function, involving energy production, biomolecule synthesis, and redox balance, among other processes. Understanding the impact of nanotopography on cellular metabolism not only helps reveal the mechanisms of cell-material interactions but also provides new insights for designing advanced cell culture platforms and optimizing cell-based therapeutic strategies.

This study aims to uncover the regulatory mechanisms of nanotopography on cellular metabolic activities using multimodal optical imaging techniques. Specifically, the research team employed nanopillar arrays as a model system to investigate the dynamic effects of nanotopography on cellular metabolism, including key processes such as oxidative stress, protein and lipid synthesis, and lipid unsaturation.

Source of the Paper

This paper was co-authored by Zhi Li, Einollah Sarikhani, Sirasit Prayotamornkul, Dhivya Pushpa Meganathan, Zeinab Jahed, and Lingyan Shi from the Department of Bioengineering and the Department of Chemical and Nano Engineering at the University of California San Diego. The study was published on November 18, 2024, in the journal Chemical & Biomedical Imaging, titled “Multimodal Imaging Unveils the Impact of Nanotopography on Cellular Metabolic Activities.”

Research Process and Results

1. Fabrication and Characterization of Nanopillar Arrays

The study began with the fabrication of nanopillar arrays with different geometric parameters on quartz wafers using techniques such as photolithography, chromium deposition, lift-off, and deep reactive ion etching (DRIE). Three configurations were prepared: diameter 1 µm, pitch 2.5 µm (D1P2.5); diameter 1 µm, pitch 3.5 µm (D1P3.5); and diameter 2 µm, pitch 4.5 µm (D2P4.5). The precise architecture of the nanopillars was confirmed using scanning electron microscopy (SEM).

2. Cell Culture and Multimodal Imaging

Hela cells were used as the model cell line and seeded on both nanopillar arrays and flat surfaces. To study the dynamic changes in cellular metabolism, the research team developed a multimodal optical imaging platform combining two-photon fluorescence (TPF) microscopy and stimulated Raman scattering (SRS) microscopy. TPF was used to image reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) within cells, while SRS was employed to visualize the metabolic dynamics of lipids and proteins.

3. Changes in Cell and Nuclear Morphology

Through fluorescence microscopy and morphological analysis, the study found that nanopillar arrays significantly influenced cell and nuclear morphology. Compared to flat surfaces, cells on nanopillars exhibited smaller cell areas and lower circularity, indicating greater cell deformation. Additionally, cells on nanopillars had smaller nuclear areas but higher nuclear circularity, suggesting that nuclei maintained a more regular shape despite the physical constraints imposed by the nanopillars.

4. Alterations in Cellular Metabolic Activities

Using multimodal imaging, the research team quantified the metabolic activities of cells on nanopillar and flat surfaces. The results showed that cells on nanopillars exhibited lower oxidative stress levels, reduced rates of protein and lipid synthesis, and decreased lipid unsaturation. These changes indicate that nanopillars regulate cellular metabolic pathways through mechanical signaling, affecting energy metabolism and biomolecule synthesis.

5. Multivariate Analysis and Metabolic Profiles

Further multivariate analysis (e.g., UMAP and hierarchical clustering) revealed the significant impact of nanopillar geometric parameters on cellular metabolism. Notably, changes in nanopillar pitch had a more pronounced effect on cellular metabolism than changes in diameter. The study also identified distinct metabolic profiles between cells on nanopillars and flat surfaces, highlighting the ability of nanotopography to modulate cellular metabolic states through mechanical cues.

Conclusions and Significance

This study demonstrates that nanotopography not only alters cell and nuclear morphology but also significantly regulates cellular metabolic activities. Specifically, nanopillars reduce oxidative stress levels, decrease protein and lipid synthesis, and lower lipid unsaturation through mechanical signaling. These findings provide a theoretical foundation for designing advanced cell culture platforms and optimizing cell-based therapeutic strategies. For example, in drug delivery systems, understanding cell-nanostructure interactions can aid in designing more effective nanocarriers to enhance drug uptake and efficacy. In regenerative medicine, scaffolds with specific nanotopographies can guide tissue formation by modulating cellular metabolism, thereby improving the success of tissue engineering approaches.

Research Highlights

1. Innovative Application of Multimodal Imaging: The research team developed a multimodal imaging platform combining TPF and SRS, enabling direct visualization and quantification of cellular metabolic activities at the subcellular level.
2. Significant Impact of Nanotopography on Cellular Metabolism: The study revealed that nanopillars significantly regulate key metabolic processes such as oxidative stress, protein and lipid synthesis through mechanical signaling.
3. Importance of Geometric Parameters: The research highlighted that nanopillar pitch has a more significant impact on cellular metabolism than diameter, offering new insights for designing functional nanomaterials.

Additional Valuable Information

The study also found that changes in nuclear morphology on nanopillars may be linked to alterations in chromatin organization and gene expression, providing a new direction for further research into the regulatory mechanisms of nanotopography on cell fate. Additionally, the research team developed a Python-based data analysis pipeline for processing multimodal imaging data, offering valuable tools and methods for future related studies.

This research not only uncovers the regulatory mechanisms of nanotopography on cellular metabolism but also provides new ideas and methods for various applications in the biomedical field.