Development of scaffold-free micro-tissues to accelerate soft and hard tissue regeneration via delaying cellular senescence and regulating inflammation

Stem cell therapies are highly attractive due to their potential to repair the injured or diseased tissue and restore function. However, the most commonly used in clinical applications were digested cells (DCs), harvested using trypsin or dispase. And scaffold-based tissue engineering techniques are too complex to achieve clinical transformation. In this work, a novel approach to fabricate scaffold-free micro-tissues (MTs) with high homogeneity and quality on a large scale is reported. The MTs prepared in this way do not require scaffolds and could retain their cell-to-cell interactions and extracellular matrix (ECM). Firstly, temperature-sensitive polymer poly(N-isopropyl acrylamide) (PNIPAM) was adopted as a base coating for the surface of glass slides to facilitate the MTs detachment when the temperature changes from 37 °C to 4 °C. Then polydopamine (PD) was imprinted onto the substrates via microcontact printing (μCP) to fabricate micropatterned substrates. After that, negatively charged heparin was grafted onto the surface of PD patterns to create anti-adhesion networks. Given the rational design and all the components` virtues, we could prepare MTs on a large scale for soft and hard tissue repair with high performance. Compared to the enzyme-treated DCs, the MTs could accelerate soft and hard tissue regeneration via delaying cellular senescence and regulating inflammation.