As documented in previous work, a mixture of PA-YIGSR and PA-KKKKK at a 9:1 molar ratio was reacted with NO gas to generate PA-YK-NO.11 (link) In order to make NO-releasing PA nanomatrices, 120 μL of a 0.1% wt stock PA-YK-NO solution (pH 7.4) was prepared and dispensed into 48-well tissue culture plates (BD Biosciences, San Jose, CA, USA) with serial dilutions to make different PA-YK-NOs, ie, 130 μmol PA-YK-NO, 65 μmol PA-YK-NO, 32.5 μmol PA-YK-NO, and 16.25 μmol PA-YK-NO.