Cary 50 probe uv spectrophotometer

The drug-loaded samples were immersed in 250 mL ethanol in a sealed beaker during constant stirring at 500 rpm. After 72 h the amounts of diclofenac sodium and indomethacin were evaluated using UV spectrometry (Varian, Cary 50 Probe UV spectrophotometer, Agilent Technologies) at 284 nm and 245 nm, respectively. The calibration curve determined the mass of the drug ( $m_d$ ). The drug content (DC) was calculated from Equation (2): $$DC \left[\%\right]=\frac{m_d}{m_s}\times 100\%$$
where $m_d$ is the mass of the drug (mg), determined spectrophotometrically from the calibration curve, and $m_s$ is the initial mass of the weighted aerogel sample. Each test was made in triplicate, and the average values were calculated with standard deviations.
Entrapment efficiency represents the ratio between the amount of the incorporated drug detected in the aerogel and the initial amount of the added drug. The entrapment efficiency was calculated with Equation (3): $$EE \left[\%\right]=\frac{m_d}{m_i}\times 100\%$$
where $m_d$ is the mass of the drug (mg), determined spectrophotometrically from the calibration curve, and $m_i$ is the initial amount of the drug (mg) that was added to a sol-gel solution before the gelation step. The test was performed in triplicate.

In-vitro dissolution tests for pectin aerogels and chitosan-coated pectin aerogels loaded with curcumin were performed using two dissolution media, SGF at pH = 1.2 and SIF at pH = 6.8, as described above. Aerogel samples were firstly placed in SGF for 2 h and immediately transferred to SIF for an additional 22 h.
In-vitro dissolution tests were performed following USP standards [23 ]. The experiments were carried out at 37 ± 0.5 °C on the Farmatester 3, USP II apparatus (Dema, Ilirska Bistrica, Slovenia). The volume of the dissolution medium was 900 mL, while the speed of rotation was set at 50 rpm. Aliquots of 2 mL for each sample were withdrawn at predetermined time periods and afterwards 2 mL of fresh dissolution medium was added to maintain a constant volume. Samples were subjected to a curcumin assay by a Cary 50 Probe UV spectrophotometer (Agilent Technologies, Santa Clara, CA, USA) at 429 nm. The concentration of curcumin was calculated using the calibration curves in SGF and SIF. All tests were performed in triplicate.