Effect of Fibrillization pH on Gelation Viscoelasticity and Properties of Biofabricated Dense Collagen Matrices via Gel Aspiration–Ejection

This study systematically investigated how the pH of fibrillization (pH 4–11) influences collagen gelation kinetics, rheological properties, and the structural and mechanical characteristics of dense collagen matrices fabricated using the Gel Aspiration–Ejection (GAE) technique. Rheometry and turbidity assays revealed that increasing pH accelerated fibril crosslinking, elevating the storage modulus (G′) from 36 to 900 Pa. Only hydrogels formed between pH 6.5 and 10 were amenable to GAE densification, producing compact matrices with enhanced fibrillar alignment and density. NIH/3T3 fibroblast-seeded matrices showed >80% viability, confirming cell compatibility across the tested pH range. The results provide a framework for tuning collagen self-assembly and densification through pH modulation, improving control of hydrogel mechanical properties for tissue engineering.