Three-Dimensional Monitoring of RBC Sedimentation in External Magnetic Fields

Hematology Biophysics Life Sciences Physics Fluid Physics Medicine
red blood cells sedimentation magnetic fields digital holographic microscopy fluid dynamics biomedicine quantitative analysis

Study on Three-Dimensional Monitoring of Red Blood Cell Sedimentation under External Magnetic Fields: A Novel Scientific Perspective

Background and Research Objective

With the widespread use of electronic devices in modern society, humans are increasingly exposed to external magnetic fields (MFs) in their living environments. However, the potential influence of these fields on biological systems, particularly the behavior of red blood cells (RBCs) in the bloodstream, remains poorly understood. RBCs play a critical role in oxygen transport, and their unique size and shape enable them to smoothly pass through even the narrowest blood vessels, ensuring efficient oxygen delivery throughout the body. The erythrocyte sedimentation rate (ESR) is a widely used hematological diagnostic technique to assess markers of inflammation or other pathological conditions. However, ESR lacks the ability to precisely monitor the 3D dynamic behavior of blood flow processes.

It has been discovered that the hemoglobin in RBCs, due to its iron ion content, is sensitive to magnetic fields. Under high-intensity magnetic fields, significant effects on RBC motion and sedimentation behavior can occur, such as faster sedimentation rates and reduced blood viscosity. However, prolonged exposure to uncontrolled or indefinite magnetic fields can potentially harm biological functions. Therefore, investigating the effects of external magnetic fields on RBC behavior, as well as understanding the 3D dynamics of the sedimentation process, is not only of biophysical significance but also offers cutting-edge insights for medical diagnosis and treatment.

Authors and Paper Source

This paper was authored by Kowsar Gholampour and Ali-Reza Moradi, affiliated with the Department of Physics at the Institute for Advanced Studies in Basic Sciences (IASBS) in Zanjan, Iran, and the Nano Science School at the Institute for Research in Fundamental Sciences (IPM) in Tehran, Iran, respectively. The article was published in the February 1, 2025, issue of Biomedical Optics Express (Volume 16, Issue 2), showcasing innovative applications of Digital Holographic Microscopy (DHM) for the 3D monitoring of RBC sedimentation.

Research Process and Methodology

This paper describes an experimental study that uses DHM technology to investigate the effects of external magnetic fields of varying strengths on RBC sedimentation behavior, particularly on the microscopic sedimentation dynamics near container walls. The experimental design is well-constructed and follows these distinct phases:

  1. Sample Preparation
    Fresh human blood samples were provided by the Zanjan Blood Bank in Iran. Plasma and buffy coat (platelet and white blood cell layer) were separated by centrifugation at 3000 g for 10 minutes at 4 °C. The RBCs were then resuspended in a physiological NaCl solution (150 mM) and diluted to a hematocrit concentration of 0.5%. The final sample was maintained in a 37 °C water bath to minimize temperature fluctuations during the experiments.

  2. 3D Experimental Setup and Magnetic Field Generation
    The study employed an off-axis DHM system based on a Mach-Zehnder interferometric configuration, which was equipped with a magnetic field generator. The sample container was a 3.5 mL single-chamber quartz cuvette (10 mm × 10 mm cross-section) positioned between two coils generating magnetic fields of 8, 13, and 16 mT.

  3. Application of Digital Holographic Microscopy
    At the start of the experiment, the RBC suspension was carefully injected into the liquid surface via a syringe infusion system to allow free sedimentation. A camera recorded digital holograms at a frame rate of 25 fps, and the holograms underwent numerical processing, including spectrum analysis, phase reconstruction, numerical refocusing, and 3D tracking. Leveraging DHM’s numerical refocusing capability, the researchers obtained clear images of different depths within the sample without physical adjustments and precisely tracked the axial and spatial sedimentation trajectories and velocities of multiple cells.

  4. Theoretical Modeling and Numerical Calculations
    The study further combined experimental data with a theoretical model to describe the sedimentation dynamics of RBCs, accounting for the interplay between magnetic force (MF), gravitational force, drag force, and the proximity effect of container walls. Through mathematical equations (e.g., Stokes’ law and magnetic field gradient analysis), the researchers predicted key characteristics of sedimentation velocities under varying conditions.

Experimental Results and Analysis

The study revealed the following critical findings:

  1. Changes in 3D Sedimentation Trajectories
    Under different magnetic field strengths, RBC sedimentation trajectories showed distinct patterns. Without a magnetic field, RBC sedimentation paths were relatively curved. Under magnetic field strengths ranging from 8 mT to 16 mT, the paths became more vertical with significantly reduced deviations from a straight line, especially in regions closer to the container walls.

  2. Changes in Sedimentation Velocity
    Sedimentation velocities increased significantly with stronger magnetic fields. At 16 mT, RBCs near the wall sedimented 100 µm in under 0.1 seconds, compared to 0.6 seconds without a magnetic field. Additionally, velocity fluctuations decreased near the container wall but increased with stronger magnetic fields, and this increase was more pronounced for cells closer to the wall.

  3. Enhanced Wall Effect
    The study found that stronger magnetic fields caused RBCs to settle preferentially near the container wall. This was attributed to increasing magnetic field gradients near the wall, emphasizing the role of proximity effects in promoting cell behavior under magnetic conditions.

Conclusion and Significance

This study experimentally confirmed that external magnetic fields enhance RBC sedimentation, with effects becoming more pronounced near container walls. These enhancements were directly linked to hemoglobin’s magnetic susceptibility. Scientifically, the study validates theoretical models and provides a novel experimental framework for simulating the microscopic dynamics of blood flow in vessels. Practically, magnetic fields may potentially reduce blood viscosity, offering therapeutic benefits while also raising concerns about the health risks of prolonged exposure to magnetic fields generated by electronic devices.

Notably, the DHM technology utilized in this research demonstrated powerful spatial and temporal resolution capabilities, as well as 3D imaging advantages. It represents a unique methodological reference for investigating microfluidic phenomena and the dynamics of small-scale biological objects.

Future Prospects and Research Value

The authors emphasize the importance of further studying the long-term effects of magnetic fields from electronic devices on human health. For example, verifying the effects of clinical-level magnetic fields and examining the cumulative impacts of low-intensity everyday magnetic fields are pressing areas for future investigation. Moreover, the methodology developed in this study could be extended to other biomedical applications, such as studying the dynamic behavior of single or multiple blood cells, exploring transport phenomena in non-Newtonian fluids, and developing magnetic field-based diagnostic or therapeutic tools.

By combining theoretical and experimental approaches, this study provides a systematic framework for understanding the 3D dynamics of RBC behavior under external magnetic fields. It not only advances the frontiers of fluid dynamics and biomedicine but also offers scientific evidence to address the health challenges posed by electronic environments in modern society.