The question: “I want to watch living cells for days without fluorescent stains or phototoxicity. Is a holographic microscope the right tool, and what are my UK options?”
Holographic microscopy — more precisely quantitative phase imaging (QPI) or digital holographic microscopy — has become a practical way to image transparent living cells without labels. Instead of staining, it measures how much the cell slows down light, turning phase shifts into quantitative images of cell mass, thickness and morphology.
How Quantitative Phase Imaging Works
- Phase shift: Light passing through a cell travels more slowly than light passing through the medium. This creates a tiny phase delay.
- Interference / hologram: A reference beam interferes with the object beam, encoding the phase information as intensity fringes.
- Reconstruction: Software recovers the phase map, giving a quantitative image of optical path length.
- Biological readouts: From the phase map you can derive cell dry mass, projected area, thickness, refractive index volume and growth rate.
A recent roadmap on digital holography-based QPI and a review of QPI advances in biomedicine describe the physics, computational reconstruction and clinical potential.
Publications and Resources
These references span QPI reviews, digital holography roadmaps, lensless imaging and live-cell applications.
Nguyen et al. (2022) — QPI advances in biomedicine
ACS Nano. Quantitative phase imaging: recent advances and expanding potential in biomedicine, from cell biology to clinical diagnostics.
View DOI
De Angelis et al. (2021) — Roadmap on digital holography QPI
Journal of Imaging. Roadmap on digital holography-based quantitative phase imaging, covering principles, computational reconstruction and applications.
View DOI
Nature Communications Biology (2023) — Label-free microscopy
Communications Biology. Viewing life without labels under optical microscopes, including QPI and holographic approaches for live-cell imaging.
View DOI
MDPI Sensors (2023) — MISHELF lensless microscopy
Sensors. Multi-Illumination Single-Holographic-Exposure Lensless Fresnel (MISHELF) microscopy: principles and biomedical applications.
View DOI
Photonics (2022) — Resolution enhancement for lensless DHM
Photonics. Resolution and contrast enhancement for lensless digital holographic microscopy and its application in biomedicine.
View DOI
HardwareX (2023) — Compact lensless holographic blood smear microscope
HardwareX. Robust and compact digital lensless holographic microscope for label-free blood smear imaging.
View DOI
Photonics (2023) — Fourier transform holography principles
Photonics. Fourier transform holography: a lensless imaging technique, its principles and applications.
View DOI
MDPI Sensors (2024) — Single-shot wide-FOV live-cell DHM
Sensors. Live cell imaging by single-shot common-path wide field-of-view reflective digital holographic microscope.
View DOI
Frequently Asked Questions
What is holographic microscopy used for in UK labs?
Holographic microscopy, also called digital holographic microscopy or quantitative phase imaging, is used to image living cells without fluorescence stains. It measures the optical path length shift introduced by the cell, producing quantitative maps of cell shape, dry mass, thickness and refractive index. UK labs use it for label-free proliferation, cell-cycle, migration and drug-response assays.
What is quantitative phase imaging (QPI)?
Quantitative phase imaging measures the phase delay of light passing through a transparent sample. Because biological cells alter the refractive index of the surrounding medium, QPI converts these tiny phase shifts into measurable images of cell mass and morphology without any dye or genetic label.
How does lens-free holographic microscopy differ from conventional QPI?
Conventional QPI typically uses microscope objectives and interferometric optics. Lens-free systems place the sample directly above an image sensor and reconstruct the wavefront from captured holograms, giving very large fields of view and compact hardware at the cost of somewhat lower resolution than objective-based systems.
Which holographic / QPI microscopes are available in the UK?
Commercial options include Nanolive (3D Cell Explorer, CX-A) for label-free 3D tomography; HoloMonitor by PHI AB (M4, M4 FL) for live-cell QPI assays; Phasefocus Livecyte for quantitative phase live-cell imaging and scratch-wound analysis; Tomocube HT-X1 for holotomography; and Ovizio BioSense for bioprocess QPM. Open-source lensless designs are also published.
Can holographic microscopy replace fluorescence imaging?
It can replace fluorescence for many morphological and kinetic readouts such as confluence, migration, growth and dry-mass changes. It cannot replace fluorescence when you need to localise a specific protein, see calcium transients, or measure a fluorescent reporter. Many labs use both: QPI for unstained long time-lapse and fluorescence for targeted validation.
What are the main advantages of label-free QPI over brightfield or phase contrast?
QPI is quantitative: it reports optical path length, dry mass and thickness in physical units, not just contrast. It is also gentler than fluorescence because no excitation light is needed, enabling days-long time-lapse without phototoxicity or photobleaching.