Intracellular 3D Printing: Fabricating Microstructures Inside Living Cells

Scientists have successfully fabricated complex, solid microstructures inside living cells without compromising their viability. This technical achievement utilises intracellular 3D printing to deposit solid polymers directly into the cell's interior. The method bypasses previous physical limitations, where delivering micron-scale, free-standing objects into non-phagocytic cells—those that do not naturally engulf particles—was effectively impossible. By injecting a bio-compatible photoresist and curing it with laser precision, the study establishes a new modality for engineering cellular function that operates independently of genetic modification.

These results were observed under controlled laboratory conditions, so real-world performance may differ.

The mechanics of intracellular 3D printing

The core challenge in cellular engineering is accessing the cytosol without destroying the cell membrane. Traditional 3D printing operates on a macro or micro scale but lacks the finesse to build inside a sealed biological container. To resolve this, the research team employed two-photon polymerisation. This technique uses a femtosecond laser to solidify a liquid photoresist only at the precise focal point of the beam. Because the polymerisation is highly localised, it allows for submicron resolution.

The process is distinct. First, the photoresist is injected into the target cell. Next, the laser draws the desired shape. The team demonstrated this versatility by printing various structures, including a 10 μm elephant, to prove complex shape control. More functional outputs included barcodes for tagging and diffraction gratings for optical readout. Crucially, the cells remained alive during and after the fabrication process.

Strategic implications: The 'So What?'

The ability to manufacture solids inside a cell shifts the focus from biological manipulation to mechanical engineering. Current methods largely rely on genetic engineering to alter cell behaviour. This study suggests that physical structures could provide a parallel track for control. The printed structures are not merely passive debris; they interact with the cell biology.

Three specific applications emerge from this data:

• High-Fidelity Tracking: Printed barcodes allow for the individual tagging of cells. This enables precise monitoring of cell migration and identification within a population.
• Remote Sensing: The fabrication of microlasers and diffraction gratings suggests a future where cells can 'report' their internal status. These optical components establish a foundation for remote intracellular sensing.
• Bioelectronics and Biomechanics: The rigidity of the printed polymers allows for direct biomechanical manipulation or functioning as scaffolds for bioelectronic interfaces.

Future outlook

While this is a proof of concept currently limited to laboratory cell lines, the trajectory is clear. The technology creates a bridge between synthetic engineering and biological systems. By embedding functional devices directly into the cytoplasm, we may eventually steer cell behaviour through physical inputs rather than chemical or genetic ones. The data indicates that intracellular 3D printing is a viable platform for the next generation of cyto-engineering.