# A Water‐Soluble PVA Macrothiol Enables Two‐Photon Microfabrication of Cell‐Interactive Hydrogel Structures at 400 mm s−1

## TL;DR

A new water-soluble material allows fast and precise 3D printing of cell-friendly hydrogel structures using laser technology.

## Contribution

A PVA-based macromolecular thiol enables efficient two-photon polymerization at low polymer concentrations and high speeds.

## Key findings

- PVASH-based hydrogels show reduced swelling and improved mechanical properties compared to traditional crosslinkers.
- Hydrogel structures were printed at 400 mm s−1 with sub-micron precision at 3% polymer concentration.
- Biofunctionalized scaffolds supported cell infiltration, adhesion, and osteogenic differentiation.

## Abstract

Two‐photon polymerization (2PP) has garnered increasing attention for engineering hydrogels with tailored architectures and controlled cellular responses. However, current 2PP strategies typically rely on (meth)acrylated proteins and inefficient chain‐growth crosslinking mechanisms. Although thiol‐ene photo‐click reactions can enhance 2PP efficiency, commercial water‐soluble thiol crosslinkers (e.g., DTT—dithiothreitol) tend to form intramolecular loops and introduce structural defects due to their short molecular length. As a result, high polymer concentrations (often up to 20%–50%) are required to achieve satisfactory print fidelity. Here, we develop a series of water‐soluble, polyvinyl alcohol macromolecular thiol (PVASH, bearing 10–35 thiol groups) for fast high‐fidelity hydrogel microfabrication via 2PP. A two‐step synthesis yields PVASH with tunable degrees of substitution and excellent water‐solubility. Compared to DTT and polyethylene glycol di‐thiol, PVASH‐based hydrogels exhibit reduced swelling, enhanced mechanical properties, and significantly improved printing fidelity. Notably, several complex hydrogel structures are fabricated at laser power as low as 20 mW and high scanning speeds of up to 400 mm s−1, achieving sub‐micron feature size at 3% polymer concentration. After biofunctionalization with RGD motifs, the micro‐scaffolds support cell infiltration, adhesion, proliferation, and osteogenic differentiation. Altogether, this work reports a new strategy for 2PP microfabrication of cell‐interactive hydrogel structures with unprecedented printing efficiency and precision.

A PVA‐based macromolecular thiol‐ene formulation enables efficient two‐photon polymerization at extremely low polymer concentrations and high writing speeds of 400 mm s−1 (20×), allowing high‐fidelity laser writing of cell‐interactive hydrogel structures on demand.