Sr8plus dissolution test station

The pH-dependent release of drug from the developed hydrogels and commercial product Cataflam (25 mg, Novartis, Basel, Switzerland) was investigated in three various buffer solutions of pH 1.2, 4.6, and 7.4, respectively. Previously, Cataflam and weighed drug-loaded formulations of hydrogel were immersed in 900 mL respective buffer solutions while using a USP dissolution apparatus type II (Sr8plus Dissolution Test Station, Hanson Research, Chatsworth, CA, USA) at 37 ± 0.5 °C. Aliquots of 5 mL were withdrawn periodically and replenished with same fresh buffer solution of the same concentration to maintain the sink conditions. Collected samples were filtered, diluted, and then analyzed on UV–Vis spectrophotometer (U-5100, 3J2-0014, Tokyo, Japan) in triplicate at λ_max 260 nm [35 (link)].

Agilent Technologies 1200 liquid chromatograph was equipped with quaternary pump (type G1311A), diode array detector (DAD type G1315B), degasser (type G1322A), oven column compartment (type G1316A), and Agilent ChemStation 32 software (Rev. B.03.02) (all from Agilent Technologies, Santa Clara, CA, USA). The used chromatographic column was a Thermoscientific ODS Hypersyl TM (250 × 4.6 mm, 5 μm), Lithuania. Other instruments used were pH-meter, inoLAB pH 7110 (Xylem Analytics Germany GmbH, Weilheim, Germany), water bath Biobase (model SY-1L4H, Biobase Biodustry, Shandong, Co., Ltd., Jinan, China), ultrasonic bath Biobase (model UC-40A, Biobase Biodustry, Shandong, Co., Ltd., Jinan, China), analytical balance PIONEER^® Analytical OHAUS PX124M (Ohaus Corporation, Parsippany, NJ, USA), dissolution apparatus SR 8 Plus Dissolution Test Station (model 73-100-104, Hanson Research, Chatsworth, CA, USA), microliter™ Syringes, 20 μL Hamilton Bonaduz AG (CH-7402 Bonaduz, Switzerland), Transferpette^® Dig. 100–1000 μL (article 704180, Brand GMBH + CO KG, Wertheim, Germany) and Rotilabo^®-Mikroliterpipette 0.5–5.0 mL (article TA 26.1, Carl Roth GmbH, Karlsruhe, Germany).

Dissolution apparatus II (USP dissolution (Sr8plus Dissolution Test Station, Hanson Research, Chatsworth, CA, USA)) and UV–V is spectrophotometer (U-5100, 3J2-0014, Tokyo, Japan) [25 (link)] was employed for evaluation of in vitro drug release from commercial available product Pentasa (500 mg, Ferring Pharmaceutical limited, Vanlose, Denmark) and fabricated CS/β-CDcPAa hydrogel at both acidic and basic medium (pH 1.2 and 7.4), respectively. The Pentasa and loaded hydrogel discs were immersed separately in a 900 mL dissolution medium of both pH 1.2 and 7.4 at 37 ± 0.5 °C and 50 rpm. A 5 mL sample was taken at a specified period of time and fresh medium of the same quantity was added back to maintain the sink condition. The UV analysis of all collected samples was performed at ʎmax 218 nm in a triplicate.

The dissolution tests were performed using a Hanson SR-8 Plus™ Dissolution Test Station (Hanson Research, Los Angeles, CA, USA) with the paddle (USP 30 dissolution apparatus II) method at a rotation speed of 50 rpm, in 37 ± 0.2 °C medium of 500 mL volume. At predetermined time-points, 5 mL of samples were withdrawn and filtered through 10 µm pore size membrane full-flow filters from the media by Hanson^® AutoPlus Multifill collector (Hanson Research, Los Angeles, CA, USA). After every sampling, media replacement was accomplished with 5 mL of fresh buffer solution. The dissolution tests were performed in triplicates in the instance of every samples.

Dissolution study was carried out for prepared hydrogels at three different pH values, i.e., pH 1.2, 4.6, and 7.4. This experiment was performed by immersing the weighed loaded hydrogel discs in 900 mL buffer solution of the respective pH value while using USP dissolution apparatus type II (USP dissolution (Sr8plus Dissolution Test Station, Hanson Research, Chatsworth, CA, USA)) at 37 ± 0.5 °C and 50 rpm. A sample of 5 mL was taken after a specific interval of time and fresh buffer solution of the same concentration was added back to maintain the sink condition constant. The samples were analyzed on UV–Vis spectrophotometer (U-5100,3J2-0014, Tokyo, Japan) in a triplicate at λ_max 222 nm [66 (link)].

The in vitro dissolution study was performed according to the procedure of a previous work [57 (link)]. The release of AG from the physical mixture and SDs were evaluated using the paddle method (SR8 PLUS dissolution test station, Hanson Research, Chatsworth, CA, USA). The 0.1 N hydrochloric acid solution (pH 1.2, 900 mL) was used as the dissolution medium, which was maintained at 37 ± 0.5 °C with a stir speed of 100 revolutions per minute (rpm). The sample (1 mL) was collected at 0, 5, 10, 15, 30, 45, 60, 90, 120, 150, and 180 min, and the dissolution fluid was maintained by supplying an equal volume of fresh 0.1 N HCl solution after each withdrawal. The samples were centrifuged at 25 °C (10000 rpm for 10 min), and the supernatant was transferred to the autosampler vials for HPLC analysis. Parameters, such as Q_5min, Q_120min, D.E., and t_70%, were used for evaluating the dissolution performance of the various formulations.