Cryogenic sintering decellularized tissue particles creates porous scaffolds that support long-term alternative macrophage infiltration in large traumatic injuries.

Decellularized extracellular matrix (ECM) biomaterials are widely utilized in soft tissue reconstruction, triggering a Type 2 inflammatory response that promotes repair. However, it remains challenging to manipulate the geometry and porosity of native ECM forms, like sheets and particulates, without chemically altering composition. We describe a controlled freeze-drying method to cryogenically sinter ECM particles into large, mechanically stable, porous 3D ECM scaffolds without altering matrix composition. Modulating small intestinal submucosa (SIS) ECM particle concentration (50 to 200 mg/mL) and freezing rate (-30 °C to -196 °C) during sintering enabled control over 3D porosity (934-3476 μm2 pore area). Moderate ECM concentrations (100 mg/mL) and slow freezing rates (-80 °C) created scaffolds with the largest pores and high mechanical stability under large strain (storage modulus 4036 ± 172 Pa). In vivo, scaffolds bridged volumetric muscle and fat pad deficits, with fabrication conditions affecting degradation and immune response between 1 and 18 weeks. Rapid CD206+ macrophage infiltration occurred, particularly in 100 mg/mL -80 °C scaffolds (4752 ± 1773 macrophages/mm2). All ECM forms induced interleukin-4 (Il4) expression during the first 2 weeks (over 10-fold vs untreated), though expression in 100 mg/mL -80 °C scaffolds persisted substantially longer (8 weeks) than non-sintered particles. Small-pored 100 mg/mL -196 °C scaffolds degraded faster and remodeled into adipose tissue after 8 to 18 weeks. This study shows that ECM particulate can be processed into mechanically robust 3D scaffolds with controllable porosity and degradation without altering biochemical composition, influencing Type 2 immune activation and tissue remodeling after volumetric injury.