AMA (0.5, 1, 2, or 3 mol equiv with respect to the moles of repeating unit of HA, i.e., 0.039 g (0.25 mmol), 0.077 g (0.5 mmol), 0.154 g (1 mmol), or 0.231 g (1.5 mmol), respectively) was then added while maintaining the pH between 8 and 9 (by adding 0.5 M NaOH) for 4 h.