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. Author manuscript; available in PMC: 2021 Sep 1.
Published in final edited form as: Anal Bioanal Chem. 2020 Jul 3;412(24):6211–6220. doi: 10.1007/s00216-020-02792-5

Fig. 2.

Fig. 2

Optimization of ninhydrin assay conditions for use with functionalized gelatin in 96-well plate format. (a) Calibration curves (absorbance versus gelatin concentration) under varied ninhydrin concentrations; legend shows the final ninhydrin concentration in the reaction solution. Temperature 70 °C. (b) Calibration curves at varied reaction temperature. 2.2 mg/mL ninhydrin. (c) Expanded calibration curve, fit with a sigmoidal curve or fit in part with a linear regression. Temperature 70 °C; 2.2 mg/mL ninhydrin. (d) Determination of degree of functionalization for a representative sample of functionalized gelatin (red square). In this example, GelMA prepared at 10 mg/mL exhibited an apparent concentration of 7.3 mg/mL (DoF 27 %).