Ultra-Rapid and Specific Gelation of Collagen Molecules for Transparent and Tough Gels by Transition Metal Complexation

Collagen is one of the main components of tumor stromal tissues with a high elastic modulus, but there have been limitations when attempting to fabricate a tough collagen gel with cells like a cancer stroma. Here, we demonstrate the rapid and specific formation of collagen gels with high transparency and high elastic modulus by transition metal complexation within minutes. Transition metal ions such as K2PtCl4 exhibited rapid gelation due to the formation of a cross-linked network of the collagen triple-helix by Pt- O and/or Pt-N bonds. Interestingly, type I to IV collagens showed rapid gelation, while other extracellular matrices and DNA did not exhibit this phenomenon, suggesting the importance of intermolecular interaction in a rigid triple-helix structure. Live imaging of colon cancer organoids in three-dimensional culture indicated a collective migration property with modulating high elastic modulus, suggesting activation for metastasis progress. This technology that facilitates deep-live observation and mechanical stiffness adjustment will be useful as a new class of scaffolds. TeaserTransparent collagen gels with tunable mechanical properties allow deep-live observation of cells cultured in a tough environment like our bodies.