Compressive modulus at 30% strain = Compressive stress (MPa)/0.3

Under the wet condition, the compressive properties of each scaffold were measured in DMEM to mimic the physiological environment [28]. The scaffolds were preconditioned by soaking in the DMEM containing 10% FBS for 24 h at 37 ◦C. Then, scaffolds were placed in a Petri dish containing fresh media and compressed using a similar setup as above-mentioned. Each reported value was averaged from six independent measurements.

#### *2.5. Evaluation of Protein Absorption on Scaffolds*

The protein absorption onto porous scaffolds was determined following a previously published protocol with some modifications [29]. The scaffold sample was cut into equal sizes (10 mm diameter and 3 mm height) and sterilized by soaking in 70% ethanol for 1 h, followed by air drying in a laminar hood. Scaffolds were incubated in 1 mL of DMEM containing 10% FBS for 24 h at 37 ◦C in a humid atmosphere containing 5% CO2. Bradford protein assays were performed to determine the residual FBS proteins left in DMEM by using bovine serum albumin (BSA) as a standard [30]. Then, 1 mL of Bradford reagent was added to 100 μL of DMEM solution and incubated for 20 min in the dark. The absorption at 595 nm was measured. The amount of FBS proteins absorbed onto the scaffold could be determined indirectly by subtracting the initial amount of proteins present in DMEM with the residual proteins left in the DMEM solution after removing the scaffold. The absorbed proteins could be reported as % (*w*/*w*) proteins absorbed per scaffold.

### *2.6. Cell Culture*

The human gingival fibroblasts (HGFs) and periodontal ligament stem cells (PDLSCs) were originally obtained from American Type Culture Collection (ATCC®). The cells were cultured in DMEM supplemented with 10% (*v*/*v*) FBS, 100 units/mL penicillin, and 100 μg/mL streptomycin in an environment of 95% air and 5% CO2 at 37 ◦C.

#### *2.7. In Vitro Cell Proliferation Study*

The scaffold samples were sterilized with 70% ethanol followed by UV exposure. Each scaffold was then transferred to 48-well plates and washed with phosphate buffered saline (PBS). Prior to seeding the cells, the scaffolds were soaked with 1 mL of fresh cell culture media containing 10% FBS for 3 h at ambient temperature to precondition the scaffolds, as previously described [31]. Thereafter, the preconditioning media were removed and the cells were seeded at a density of 5 × 104 cells/well. Cell cultivations on the scaffolds were carried out over 8 days for the HGF cells and 21 days for the PDLSCs cells, respectively. The cell proliferations were evaluated using the MTT colorimetric assay. For each time point, the scaffolds with cultured cells were washed twice with PBS and transferred into a new clean well. Then, 0.5 mL of MTT solution (1 mg/mL) was added to each well, followed by incubation at 37 ◦C for 4 h. The excess MTT solution was then removed and formazan crystals that formed in the living cells were dissolved by adding 0.5 mL isopropanol. The liquid solution measured the absorbance at 570 nm using an Epoch microplate spectrophotometer (BioTek Instruments, Inc., Winooski, VT, USA). To visualize nuclear and cytoskeletal morphologies, both the HGF and PDLSC cells were fixed with 2% paraformaldehyde and permeabilized with 0.1% Triton X-100. After washing with PBS, the nuclei were stained with Hoechst 33342 (Invitrogen Corporation, Carlsbad, CA, USA) and the actin filaments were labeled with Alexa Fluor 568 phalloidin solution (Invitrogen Corporation, Carlsbad, CA, USA). The images were collected with a confocal laser scanning microscope (FV10i-DOC; Olympus, Tokyo, Japan).
