2.2.7 Stability (enzymatic, pH 5 and PBS)
To study stability of our gelatin hydrogel containing PDA-PAR30 NPs (Gel-PDA-PAR30 1:1) non-dilute we used three different testing configurations: i) stability in physiological pH, ii) in acidic condition and iii) in the presence of enzyme (collagenase).
For the experiment at physiological pH, we used PBS solution. Hydrogel samples were placed in 24 wells-plate with 1 mL of PBS 1X from Dutscher, at +37°C. Measurements were carried out after vacuum-drying step for 4 hours then we weighed samples. Finally, we put them in a new PBS solution and put them back at +37°C until next measurement. We performed these measurements at different time point: initial measurement (before stability experiment) then at days 1, 4, 7 and 15.
For the experiment in acidic condition (pH=5), protocol was the same as the previous one with the same follow-up at different time point. We used a citrate-phosphate buffer (0.15M, pH = 5).
To test enzymatic stability, we used collagenase (Sigma-Aldrich) solution at 0.1% w/v. Measurements were performed using the same protocol but with different time points. Measurements were realized at t0, 30 minutes, 1 hour and 2 hours. All samples were washed three times with PBS 1X in order to remove collagenase enzyme, dried with paper and stock until next day to perform vacuum-drying and weigh. All results were compared to gelatin hydrogel without NPs condition. All samples were performed in triplicates.