2.5.1. Swelling Test

Samples of M1, M2, M3, M4, and CNp-M4 membranes were cut to a size of 1 × 1 cm and weighed on pre-weighed aluminum trays. The samples were divided into five blocks, corresponding to di fferent times as follows: 5, 10, 20, 30, and 60 min. The membranes on the trays were placed on a flat surface, and 750 μL of PBS 1X pH 7.4 was added to each sample.

Once the established time had elapsed, the trays were turned vertically for 2 min on absorbent paper, allowing the draining and absorbption of the excess of PBS. After that time, the membranes in the trays were weighed again [18]. The assessment was performed in triplicate for each of the di fferent times.

The swelling percentage (%S) was calculated using the following formula [19]:

$$\% \text{S} = \frac{\text{M}\_{\text{s}} - \text{M}\_{\text{d}}}{\text{M}\_{\text{d}}} \times 100 \tag{3}$$

where Ms and Md are the weight of the swollen membrane and dried membrane, respectively.

## 2.5.2. Mechanical Test

Tensile strength (TS) and the elongation at a break (%E) of M1, M2, M3, M4, and CNp-M4 were determined using a Sintech 1 2 testing machine (MTS, USA), which was equipped with a 100-N load cell at a crosshead speed of 2.4 mm s<sup>−</sup>1. Three samples of each formulation were cut into a dumbbell shape with a width of 10 mm and an e ffective length of 40 mm between the clamps at the beginning of the measurement. The thickness of each sample was measured using a Vernier at five di fferent points before testing, and the average of these was employed for TS calculation. The load (Lb) and displacement (mm) of each film were recorded during the stretching. TS and %E were calculated by Equations (4) and (5), as published by Karki et al. [17]:

$$\text{TS} = \frac{\text{F}}{\text{A}}\tag{4}$$

$$\% \text{E} = \frac{\text{D}}{\text{L}} \times 100\tag{5}$$

where TS is reported in MPa, F is the maximum load (N) required to break the film, and A is the initial cross-sectional area in mm2. In Equation (5), D is the displacement of the film elongation at the rupture and L is the initial length.

### 2.5.3. Thermogravimetric Analysis (TGA)

The thermal stability of the membranes (M4, CNp-M4), CNp, and curcumin was evaluated through TGA, employing a Hi-Res TGA 2950 Thermogravimetric Analyzer (Modulated TA Instruments, New Castle, DE, USA). In brief, 5 mg of each sample was analyzed starting at room temperature and increasing to 500 ◦C at a heating rate of 10 ◦C/min under a nitrogen atmosphere.

### 2.5.4. Di fferential Scanning Calorimetry (DSC)

The thermal properties of the membranes (M4, CNp-M4), CNp, and curcumin were determined with the DSC 2910 (Modulated TA Instruments, DE, USA). Lyophilized samples were placed in hermetic aluminum cells and evaluated starting at room temperature and increasing to 250 ◦C at a heating rate of 10 ◦C/min under a nitrogen atmosphere.
