Quantitative phase imaging of adherent mammalian cells: a comparative study

Studying mammalian cells over extended periods requires non-invasive methods that avoid damage from staining or prolonged exposure. Traditional imaging techniques often rely on dyes or fluorescent markers, which can alter cell behavior. Prior research has shown that optical methods can capture cell mass and morphology without chemical intervention. However, the accuracy and consistency of these methods remain unclear. This uncertainty drives the need to compare different quantitative phase imaging approaches. Researchers have long sought reliable metrics for cell growth and health. But few studies have directly compared the precision of these imaging tools. A gap exists in understanding how optical volume density measurements vary across platforms. This gap motivated the current investigation into three distinct imaging techniques.

The goal of this research is to evaluate and compare three quantitative phase imaging methods for their suitability in monitoring adherent mammalian cells. The study aims to determine how each technique measures optical volume density and whether these measurements align across platforms. Researchers wanted to assess the precision of each method in capturing cell dry mass. The motivation stems from the need for a reliable, non-invasive imaging approach in cell culture studies. By comparing digital holographic microscopy, lens-free microscopy, and quadriwave lateral sheering interferometry, the team sought to identify strengths and limitations. The focus is on long-term cell monitoring without staining or photo-toxic effects. The study also aimed to quantify the relationship between optical volume density and cell dry mass. This work addresses a specific need in biomedical imaging for consistent, high-resolution cell analysis.

The research team used three distinct imaging techniques to measure cell dry mass in adherent mammalian cultures. Digital holographic microscopy captured interference patterns to calculate optical path differences. Lens-free microscopy relied on in-line holography to reconstruct cell morphology. Quadriwave lateral sheering interferometry used a four-beam interference setup for phase imaging. Each method was tested on the same cell samples to ensure consistent comparisons. The optical volume density values were extracted from each platform's output. Researchers calculated the linear relationship between measurements from the three techniques. They also assessed the precision of each instrument's measurements. The study focused on adherent cells to ensure uniformity in sample preparation.

The study found a linear relationship between optical volume density measurements from the three imaging techniques. Digital holographic microscopy showed a strong correlation with lens-free microscopy results. Quadriwave lateral sheering interferometry measurements aligned closely with the other two methods. The optical volume density values were consistent across platforms, suggesting a shared underlying metric. Researchers estimated the precision of each technique's measurements. Digital holographic microscopy had a precision of ±0.05 refractive index units. Lens-free microscopy achieved a precision of ±0.07 refractive index units. Quadriwave lateral sheering interferometry demonstrated a precision of ±0.04 refractive index units.

The authors report that the three quantitative phase imaging methods produce comparable optical volume density measurements. The linear relationship between techniques suggests a common basis for measuring cell dry mass. The precision estimates indicate that each method can reliably track cell growth over time. These findings support the use of quantitative phase imaging for long-term cell monitoring. The study confirms that optical volume density is a valid metric for cell dry mass. The results suggest that any of the three techniques could be used for consistent cell analysis. The authors emphasize that the non-invasive nature of these methods is a key advantage. They conclude that further work is needed to validate these findings in different cell types.