**3.3 Swelling behaviour**

The swelling degree (SD) was determined gravimetrically as follows: Both the hydrogel beads were immersed in phosphate buffered saline (PBS, pH 7.4) at 37°

C. The swelled samples were taken from the PBS at selected time intervals of 1, 2, 3, 4, and 10 up to 24 h, wiped with tissue paper, weighed and placed again in PBS. The SD, in percentage, was calculated using Eq. (1)

$$\text{SD} = \frac{\text{Ws} - \text{Wd}}{\text{Wd}} \ast \text{100 (\%)}\tag{1}$$

where Ws and Wd are the weights of swollen and dry beads, respectively.

#### **3.4 Release study of curcumin**

The cumulative release of curcumin from hydrogel beads was carried out through incubating samples while shaking at 100 rpm in 20 ml of buffer solution (PBS) at pH 7.4 (1, 2, 3, 4, 10 up to 24 h incubation) at 37°C. After incubation, 3 ml sample was taken out from the buffer solution and analysed by UV-Vis spectrophotometer (Lambda 25-PerkinElmer UV-vis spectrophotometer) at max of 430 nm. The withdrawn volume of the sample was replaced with equal volume of fresh buffer solution to keep the volume of release fluid constant. The percentage drug release was calculated by using the following formula,

$$\begin{array}{c} \text{Percentage drug release} = \{ \text{Amount of drug released} \} \\ \text{Amount of drug loaded} \times 100 \end{array} \tag{2}$$
