Rethinking the cell as a physical and programmable space
Cells have long been engineered through biochemical and genetic approaches. Gene editing, synthetic biology, and molecular modulation have enabled unprecedented control over cellular functions. However, these strategies operate primarily through biochemical pathways. As a result, they leave the physical architecture of the cell largely untouched.
Recently, a major advance in physical intracellular engineering has challenged this paradigm. It demonstrates the feasibility of fabricating functional microstructures directly inside living cells using two-photon 3D printing.
Importantly, this approach reframes the cell not only as a biochemical system. It also defines the cell as a three-dimensional physical environment that can be sculpted with submicron precision. As a result, it introduces a new layer of control, complementary to genetic and chemical tools, through which engineered internal structures can influence cellular behavior.
Two-photon polymerization inside living cells
The technology relies on two-photon absorption, a nonlinear optical process in which polymerization occurs only at the precise focal point of an ultrafast laser. Because the reaction is spatially confined, it allows high-resolution 3D printing while minimizing phototoxicity to surrounding cellular components.
In this work, photosensitive precursor materials are introduced into living cells. When the laser is focused inside the cytoplasm, localized polymerization occurs, enabling the formation of stable micro- and submicron-scale structures entirely within the intracellular space. Importantly, cells remain viable after fabrication, preserving membrane integrity and core biological functions.
This level of spatial control is fundamentally different from surface patterning or extracellular scaffolding. It enables the direct integration of artificial structures within the native cellular architecture, opening a new field at the interface of photonics, materials science, and cell biology.
Functional microstructures and intracellular mechanics
The technology relies on two-photon absorption, a nonlinear optical process in which polymerization occurs only at the precise focal point of an ultrafast laser. Because this reaction remains spatially confined, the process enables high-resolution 3D printing while minimizing phototoxicity to surrounding cellular components.
In this process, researchers introduce photosensitive precursor materials into living cells. When the laser is focused inside the cytoplasm, localized polymerization occurs. Consequently, the method enables the formation of stable micro- and submicron-scale structures entirely within the intracellular space. Importantly, cells remain viable after fabrication, preserving membrane integrity and core biological functions.
Importantly, this level of spatial control is fundamentally different from surface patterning or extracellular scaffolding. As a result, it enables the direct integration of artificial structures within the native cellular architecture, opening a new field at the interface of photonics, materials science, and cell biology.
Beyond genetics: toward hybrid biological–physical cells
One of the most disruptive aspects of this work is its conceptual shift. Instead of modifying gene expression or signaling cascades, this technology introduces engineered physical components as active elements of cellular regulation. Cells become hybrid systems, combining biological processes with fabricated micro-architectures.
Potential applications extend far beyond fundamental research. Intracellular microstructures could serve as:
- techanical supports or constraints to guide cell shape and polarity,
- optical or sensing elements embedded within cells,
- physical regulators of intracellular transport or force distribution.
This vision resonates with emerging efforts to build programmable living systems, where control is distributed across genetic, biochemical, and physical dimensions.
Implications for advanced 3D cell models and bioengineering
While the technique is currently applied at the single-cell level, its implications extend to advanced 3D cell culture systems. As 3D models become more physiologically relevant, understanding and controlling intracellular organization becomes increasingly critical.
Physical intracellular engineering introduces a new toolset for dissecting cellular behavior in complex environments. Combined with controlled 3D culture platforms, it may enable unprecedented resolution in linking intracellular mechanics to tissue-level organization.
In the long term, this convergence of intracellular fabrication, 3D cell culture, and biophysical control could redefine how cells are studied, engineered, and ultimately harnessed for biomedical and biomanufacturing applications.
A foundational step toward intracellular fabrication
Two-photon 3D printing inside living cells represents a foundational advance rather than a mature technology. Challenges remain in scalability, material diversity, and integration into high-throughput workflows. Yet its significance lies in opening a previously inaccessible design space.
By demonstrating that living cells can host fabricated microstructures without losing viability, this work establishes a new frontier: cells as sites of fabrication, not just objects of manipulation. It marks a shift toward a future where cellular function can be shaped not only by genes and molecules, but by engineered physical architectures at the subcellular scale.
