Fatigue-Resistant Cryogel as Suturable Autogenous Connective Tissue Graft Substitute

Objectives: Autograft is gold standard material for periodontal plastic surgeries, however it has shortcomings of second surgical sites and limited donor tissues. Therefore，aim of this study is to fabricate biocompatible and biodegradable super-macroporous scaffolds with tissue-like elasticity.
Methods: Methacryloylated serum albumin (AlbMA) and gelatin (GelMA) were synthesized. The precursors contained 0.3% Ammonium persulfate (APS), 0.1% N,N,N',N'-Tetramethylethylenediamine (TEMED), and 3% protein with different AlbMA/GelMA ratios (A3G0, A2G1, A1.5G1.5, A1G2, and A0G3). After 48h-incubation at -20°C, AlbMA-GelMA cryogels were obtained. The pore structures, porosity, swelling, and enzymatic degradation were characterized. Mechanical properties were investigated by cyclic compression (cycle=100, strain=95%) and oscillatory-frequency tests, which simulated intraoral dynamic environments. Handling performances (trimming, piercing and suturing) were evaluated. L929 cells were cultured in 3D for 5 days, and their adhesion, morphology，proliferation, and invasion were studied.
Results: With a higher proportion of AlbMA, cryogels exhibited increasingly higher porosity (89.56% for A3G0 while 66.67% for A0G3) and lower degradation rate (around 27h for A3G0 while 7h for A0G3). A1.5G1.5 displayed the lowest swelling ratio (1935%) and the smallest pore size (29.39±5.29μm) whereas those of A3G0 (3433%, 57.63±21.97μm), A2G1 (3452%, 65.39±18.25μm), A1G2 (2444%, 56.42±10.68μm), and A0G3 (2125%, 59.89±10.68μm) were significantly higher. Cyclic compressional and rheological test showed superb fatigue-resistant properties for A3G0 and A2G1 whereas others were broken under axial/nonaxial forces and repeated cycles. All samples exhibited satisfactory manipulating performances and excellent cytocompatibility. A3G0 had the least number of adhered cells after 1-day culture. A3G0 and A2G1 had the deepest cell invasion depth (25μm) after 5-day culture.
Conclusions: Tunable AlbMA-GelMA scaffolds were successfully fabricated. Among all groups, A2G1 integrated novel physicochemical properties (higher porosity, higher fluid absorption, and super-elasticity) and biological performances, which indicates A2G1 has promising potential as an intraoral biomaterial as it keeps inner structures from collapsing when endures dynamic forces.