Tissue Breathing: Taiwanese Scientists Create Ultra-Porous Ink for Organ Printing

New Self-Assembling Chitosan Hydrogels: Stable 3D Printing at Record-Low Concentration

Scientists at the National Taiwan University have developed a dynamic hydrogel based on two chitosan derivatives — with gallol and boronic acid groups. The material forms a double self-assembling network that allows for the reliable printing of complex 3D structures at a concentration of only 2 wt% — several times lower than most existing bio-inks.

Researchers led by Professor Shan-hui Hsu synthesized two modified chitosans: CG (with gallol groups) and CB (with boronic acid). When mixed, they form dynamic borate ester bonds that complement the physical self-assembly of each component in the solution.

Rheological measurements and small-angle X-ray scattering showed that CG and CB individually form rod-like clusters. Their combination in the CGB hydrogel creates a compact fractal network with enhanced short-range order. This simultaneously provides shear-thinning (thinning under shear), rapid self-healing, and sufficient mechanical strength for printing without collapse.

The hydrogel exhibits sensitivity to glucose: boronate bonds reversibly break in the presence of sugar, paving the way for "smart" constructs that react to biomarkers. At the same time, the material remains entirely chitosan-based — a natural polysaccharide with proven biocompatibility, biodegradability, and antimicrobial properties.

Why this matters for people. Traditional hydrogels for bioprinting often require high polymer concentrations (5–20 wt%), which impairs the diffusion of nutrients and oxygen to cells within the construct. The new CGB hydrogel works at 2 wt%, maintaining high water content and porosity close to that of real tissue. This simplifies the creation of complex organ models, vascular networks, skin equivalents, and implants.

Potential applications:

• regenerative medicine and tissue engineering;
• glucose-controlled drug delivery (relevant for diabetes);
• laboratory tissue models for drug testing;
• "smart" wound dressings that react to inflammation.

Limitations. So far, the work demonstrates in vitro printing. Long-term stability in a living organism, the effect on cells (cytotoxicity, proliferation), and the scalability of printing large constructs require further research. Glucose sensitivity is useful but may require precise tuning for specific applications.

What's next. The authors plan to test the CGB hydrogel as a bio-ink with living cells and study its behavior under simulated physiological conditions. The next step is optimizing the composition to increase strength and adding other functional groups.

Chitosan-based hydrogels have long attracted attention due to the availability of raw materials and safety. The new double dynamic network solves a key problem in 3D bioprinting — the balance between fluidity during extrusion and stability after printing. If the technology scales, it could significantly accelerate the transition from laboratory prototypes to real medical devices.