*2.3. Analysis of the Prepared Liposomes*

The DEX vesicles were analyzed for size distribution and Zeta-potential profile with a Malvern Zetasizer Nano ZS ZEN-3500 device (Worcestershire, UK). The Zetasizer evaluation of sizes was performed on unit samples and on 1:10 dilution for the Zeta potential.

The liposome shapes were examined in differential interference contrast (DIC) optical microscopy, and size distribution was assessed by the visual comparison of micrographs with a standard scale measurement, using a Nikon Eclipse Ti-E Inverted Microscope equipped with an NIS Elements Basic Research imaging software (NIS E-Br).

The pH values of the obtained solutions were measured using a Sartorius Professional PP-50 pH Meter.

The in vitro release kinetics of DEX from nano-DEX, from DEX solution, was investigated over 12 h using the regular dialysis method. This technique is based on physical separation of the samples, offering the possibility of determining the drug molar concen-

tration at periodic moments of time. Ten milliliters of the tested solutions were placed into a cellulose acetate dialysis bag (MW cut off 12–14 KDa, Sigma Aldrich Chemical Co., Schnelldorf, Germany), representing the inner dissolution compartment. Then, the bag was introduced into a large glass with 200 mL of the release medium (consisting of phosphate buffered saline, pH 7.4, Sigma Aldrich Chemical Co., Schnelldorf, Germany), under continuous magnetic stirring of 100 rpm at 37 ± 0.5 ◦C.

The molar concentration of DEX was determined using a UV–Vis spectrophotometer (Hewlett Packard 8453, equipped with an HP Chem-Station software for assessing the absorbance between 259 and 281.6 nm), by extracting 2 mL of the release medium at certain intervals of time: 15, 30, 45, 60, 90, and 120 min, 3, 4, 6, 8, 10, and 12 h, respectively. After each determination, the same volume of medium was replaced in the dissolution compartment.

The dissolution profile of DEX released from nano-DEX was compared with those assessed for DEX solution (1 mg/mL), identical to that existent in 10 mL nano-DEX, using the same UV–VIS method.
