2.4.3. Thermal Analysis

The thermal behavior of the drug loaded RDS and pure isoniazid (reference) was characterized using a differential scanning calorimetry (DSC) machine equipped with a 50-position automatic sampler (Q2000 Differential Scanning Calorimeter TA Instruments, New Castle, DE, USA). Separate aluminum crucibles containing about 9 mg of each sample were analyzed under an inert nitrogen flow of 25 mL/minute and heating rate of 10 ◦C.min−<sup>1</sup> while an empty crucible subjected to the same testing condition served as the reference. All measurements were performed in triplicate per sample under three heating cycles at a temperature range of 0–220 ◦C.

### 2.4.4. Determination of Crystallinity

The crystalline nature of the RDS formulation and pure isoniazid were evaluated under ambient conditions (25 ± 2 ◦C) using an X-ray diffractometer equipped with the X'Pert PRO data collector software (PANalytical Inc. MA, USA). Each sample (about 3 mg) analysis was performed at a voltage and current of 45 kV and 40 mA, respectively, and a 2θ range of 5 to 90◦ using a continuous scan mode with a scan step size of 0.03.
