Viscometer

The viscosity of the prepared testosterone formulations were calculated using a Brookfield Viscometer (Brookfield Model RVDV-II Middleboro, USA) by use of spindle no 52. The spindle speed rate was amplified in ascending (0.01–0.1 rpm) to descending speed order (0.1–0.01 rpm). The viscosity was measured from the Viscometer display.

The viscosity of the gel formulation was measured with a Brookfield viscometer (Brookfield, USA; Capcalc Version 2.2) using 1x model and cone number 01, with an angular velocity of 5 rpm at 25 °C. An average of five readings was used to calculate viscosity.

The ibuprofen nanosuspension was prepared using a combination of a eutectic emulsion evaporation method and ultrasonication. Approximately 60 g of ibuprofen eutectic emulsion was diluted with 240 mL of the dilution medium (30 g of glucose and water qs to 240 mL) and continuously evaporated under a fume hood on a hot plate stirrer at 45°C for 2 days. Finally, the volume of suspension was adjusted to 55 mL and then sonicated with a probe ultrasonicator with probe model CV18. Each formula was sonicated at an amplitude level of 50% with a 30-second on and 2-second off pulse for 30 minutes in an ice bath. Approximately 300 mg of xanthan gum was dispersed in the nanosuspension as a viscosity inducer and stabilizer, and 60 mg of sodium benzoate, a preservative, was added with continuous stirring using a magnetic stirrer overnight. The volume of nanosuspension was adjusted to 60 mL with the addition of water and mixed using a homogenizer. This product was assigned to be a formulated ibuprofen nanosuspension (fNS). The final formulation of fNS is shown in Table 1. The fNS and commercial ibuprofen suspension (Nurofen) were investigated for viscosity and rheology using a Brookfield viscometer. The particle size and the zeta potential were measured using the Zeta-sizer as described earlier.

The viscosity of true nanoemulsions was determined without any dilution using Brookfield Viscometer. The sample (1 g) was taken in a beaker and allowed to equilibrate for 5 min before measuring the dial reading using a spindle 40 and the measurement was started by operating the Viscometer at 0.6 rpm, the speed was gradually increased and the measurement was recorded when the torque reached 10%. The speed was gradually increased at a constant rate for all tested samples until the torque reached 90%, with 30 s between each successive speed at 0.5, 1, 2.5 and 5 rpm respectively. At each speed, the corresponding dial reading on the Viscometer was noted.[10 ] The electrical conductivity of nanoemulsion was determined using conductivity meter (EC Testr 11+, USA) at 25°C. The experiment was conducted in triplicate.