4.3. Differential Scanning Calorimetry (DSC) The thermal behavior of the blend films was performed with a thermal analysis selleck inhibitor instrument (DSC1 STAR System, Mettler Toledo, Switzerland) at a heating rate of 10��C/min and nitrogen gas flow rate at 50mL/min.2.4.4. Mechanical Properties Mechanical properties were used to determine the performance of materials expected to undergo stresses during utilization. The tensile strength and percent elongation at the breakage of the blend films were determined at dry state. Samples were cut into rectangular (10mm �� 30mm) pieces, and average thickness of four different locations was measured with a micrometer. The tensile properties of the blend films were examined with a tensometer (Instron 8872, Instron Ltd., UK) at constant rate (15mm/min).2.4.5.
Swelling Property Water absorption property of the CS/SF blend films was determined by immersion in PBS (pH 7.4) at 37��C for 24h. The wet weight (Ws, swollen weight) and dry weight (Wd, dried at 65��C overnight) were measured. Then, the swelling index was calculated as shown in (1).Swelling??index??=(Ws?Wd)??��100Wd.(1)2.4.6. In Vitro Enzymatic Degradation Degradation of the CS/SF blend films was determined as percentage of weight remained after incubation in lysozyme solution. According to Nwe et al. [27], samples with known dry weight (Wo) were immersed in PBS pH 7.4 containing 10��g/mL lysozyme at 37��C for 4 weeks and refreshed weekly. At various time points (1, 2, 3, and 4 weeks), the samples were removed and dried at 65��C overnight.
The dried samples were weighed and determined as dry weight after degradation (Wt) and the percentage of the remaining weight was calculated as shown in (2).%??Weight??remained??=??(WtWo)??��??100.(2)2.5. Biocompatibility of Fibroblast Cells and CS/SF Blend Films2.5.1. Indirect Cytotoxicity Test Before culture, the CS/SF blend films were sterilized with 75% ethanol and immersed in fresh culture medium for 24h. Biocompatibility was tested with human dermal fibroblasts (HDF; PromoCell, Germany), for which the 7�C11 passages of HDF cells were used.The cytotoxicity test of the CS/SF blend films was adapted from the ISO10993-5 [28], an international standard method for testing medical devices. The cell viability was determined after being incubated with the extraction medium from the prepared film.
The extraction medium was obtained by incubating the sterile CS/SF blend films at 37��C in fresh culture medium at extraction Batimastat ratio of 10mg/mL. After 24h, the extraction medium was diluted to final concentration of 0.5, 1, and 2.5mg/mL. The fibroblast cells were seeded in 96-well plate at a density of 1��104cells/well and incubated in culture medium for 24h, then replaced with various concentrations of extraction medium, and cultured for further 5 days without any change of medium.