Ta xtplus texture analyser

TA.XT.Plus Texture Analyser (Stable Microsystems, Godalming, UK) equipped with a 5 kg load cell, cylinder probe and the mucoadhesion measuring system A/MUC was applied for examination of mucoadhesive properties. The mucoadhesion of chitosan and βGP/chitosan microparticles were evaluated on porcine vaginal mucosa, which was attached to the upper probe with α-cyanoacrylate glue and lowered on the surface of microparticles with a constant speed of 0.5 mm/s [61 (link)]. Each formulation of microparticles (100 mg) was located on the platform below the texture analyser probe and moisturized with 100 μL of acetate buffer pH 4.5. The tests were conducted at 37 °C ± 0.5 °C. An acquisition rate of 200 points/s and a trigger force of 0.003 N were chosen for all measurements. After keeping contact for 100 s under an initial contact force 0.5 N, the factors were determined during preliminary studies, and the two surfaces were detached at a constant speed (0.1 mm/s). The maximum detachment force F_max (N) as a function of displacement was recorded directly from Texture Exponent 32 software (version 5.0, Stable Microsystems, Godalming, UK), whereas the work of mucoadhesion W_ad (expressed in μJ), was calculated from the area under the force vs. distance curve. Cellulose paper was used as a negative control.

The mechanical properties (strength (ST) and Young’s modulus (MY)) were evaluated via the puncture test, according to the methodology described by (García-Argueta et al., 2013) [11 (link)], with some modifications (Figure 4). Briefly, a texturometer (TA.XT Plus Texture Analyser: Stable Micro Systems, Godalming, UK), with a p.0.255 ¼” stainless-steel spherical test probe, a test speed of 1.0 mm/s and a penetration distance of 30.0 mm, was employed to obtain the force–deformation curve (Figure 5). From these curves, the strength and Young’s modulus were calculated. The strength was considered the maximum force prior to the fracturing of the CEF. Young’s modulus (YM) was considered the slope of the linear proportion (6.25 mm up to 50% of the penetration distance of the probe) of the force–deformation curves. The measurements were repeated seven times for each composite edible film. All parameters were determined through the Exponent 6.1.20.0 (Stable Micro Systems, UK).

The disease index (DI) was determined based on the infected area. The DI score of fruit without infection, with an infected area of <10%, 11–20%, 21–35%, or 36–50%, were designated with scores 0, 1, 2, 3, or 4, respectively. The firmness of the fruit was determined by penetration tests using a TA.XTplus Texture Analyser equipped with a flat-end 6 mm probe (Stable Micro Systems, Surrey, UK). Penetration distance and speed were set at 12 mm and 20 mm s⁻¹, respectively. The total soluble solids of the pulps were determined by a PAL-1 digital refractometer (ATAGO Co., Ltd., Tokyo, Japan). To determine the titratable acids, 5 g of pulps was diluted with 75 g ultrapure water, and automated titration was conducted using a Titrando 905 equipped with Robotic Titrosampler (Metrohem, Herisau, Switzerland). Sodium hydroxide was used as the titrant, and the titration was terminated at a pH of 8.4. The volumes of titrant used were recorded and calculated to citric acid equivalents.

The forces that 20 volunteers applied using their thumbs were measured using a TA.XTPlus Texture Analyser (Stable Micro Systems, Surrey, UK). The selected volunteers were 10 males and 10 females aged between 20 and 35 years. The volunteers were asked to apply the same force they would use to push an elevator button or to press a stamp onto an envelope, using their right thumb and a 30 s application period, as shown in Fig. 1B. The Texture Analyser was used in tension mode to register the force curves. Three different parameters were determined from these curves: the maximum, minimum and average forces applied during this time interval (Fig. 1C).

The adhesion of the non-crosslinked and thermally crosslinked carriers to artificial skin (VitroSkin^® N-19, IMS Inc., Cape Coral, FL, USA) was tested with TA.XTplus Texture Analyser (Stable Micro Systems, Surrey, UK) equipped with a mucoadhesion rig and a cylinder delrin^® probe (⌀ = 10 mm) at ambient conditions. A method developed by Tamm et al. [42 (link)] was used in a slightly modified format. Shortly, circular samples (⌀ = 11 mm) of the carriers were prepared and attached to the probe with an adhesive double-sided tape (Scotch™, 3M, Livonia, MI, USA). Simulated wound fluid (200 µL/sample) was pipetted on the artificial skin before the measurement. The simulated wound fluid contained 2% bovine serum albumin (Sigma-Aldrich, St Louis, MO, USA), 0.02 M CaCl₂·2H₂O (Merck, Darmstadt, Germany), 0.4 M NaCl (Sigma-Aldrich, St Louis, MO, USA), 0.08 M tris(hydroxymethyl)-aminomethane (Merck, Darmstadt, Germany) and purified water [43 (link)]. The testing conditions were set as follows: pre-test speed 0.5 mm/s, test speed 0.5 mm/s, post-test speed 5 mm/s, applied force 1 N, return distance 100 mm, contact time 60 s, and trigger force 0.05 N. Scotch™ adhesive double-sided tape and commercial wound dressing Aquacel™ (ConvaTec Inc., Reading, UK) were used as references.

This test was done using an expanded method of one proposed in a previous work [32 (link)] to evaluate the mechanical properties of the freeze-dried bigels, which will determine their suitability for vaginal administration [49 (link)]. A TA.XTplus Texture Analyser (Stable Micro Systems, Surrey, UK) was used with a 5 kg load cell and a cylinder probe with a diameter of 20 mm. Half a lyophilizate was fixed to the texture analyser table with double-sided tape. The probe was placed at an initial height of 20 mm above the table. In a compression and cyclical mode, the probe descended at 1 mm/s and, after reaching a trigger force of 0.49 N, pressed into the dosage form to a depth of 1mm at 1 mm/s. The probe then returned to the starting height at the same speed. The force applied by the probe vs. time was measured. The maximum force in the first compression cycle was taken as an indicator of the hardness of the formulation and the deformability was determined from the maximum forces in the various cycles. This assay was done in triplicate for each batch. The hardness data were statistically analysed using Student’s t-test (considering p < 0.05 as significant).

The mucoadhesion force and work were assessed ex vivo using the TA.XTplus Texture Analyser (Stable Micro Systems) to check whether the formulations show sufficient mucoadhesion capacity to adhere to the vaginal mucosa at the time of administration, using a modification of a previously described method [17 (link)]. A 2 × 2 cm fragment of excised bovine vaginal mucosa (obtained from a local slaughterhouse) was fixed to the bottom of a Petri dish and hydrated with 5 mL of SVF. The LbL film was fixed to a 1 cm-diameter cylindrical probe, with the chitosan derivative layer facing the vaginal mucosa, as expected at the time of administration. The preparation was moved at a speed of 1 mm/s until it came into contact with the vaginal mucosa, applying a contact force of 500 g for 30 s. The probe was then separated from the sample at a speed of 1 mm/s up to the starting height of the test. The maximum force required to separate the film from the vaginal mucosa (detachment force) was recorded as the mucosal adhesiveness. The area under the curve between the force-distance profiles (detachment work) was determined, which is considered to be the mucosal stickiness. Each batch was evaluated in triplicate.