Thermo scientific sl 16r centrifuge

A purification process was used for loaded-PNP. Dialysis and centrifugation were investigated to eliminate any residual of surfactant and/or unloaded fluorescent molecules. The NPs suspensions were studied in terms of mean size, PDI and surface charge, before and after the purification phases, to evaluate variations due to the purification processes.
For centrifugation process we used Thermo-scientific SL 16R Centrifuge (Thermo Scientific Inc., Waltham, MA, USA) at 12,000 rpm for 1 h at 8 °C. The obtained supernatants were collected for HPLC analysis, pellet was resuspended in water and characterized through PCS analysis.
For dialysis process we used membranes (Mwco 3000 Da, diameter 11.5 mm; Spectra/Por^®) previously hydrated. The colloidal suspensions inserted in dialysis membranes were immersed in 500 mL of distilled water. The frequencies of water changes per hour in dialysis (sample PNPs and loaded-PNP) were 3/3 L/h (3 L in 3 h). At the end of the procedure the samples were collected and characterized through PCS analysis.
Further centrifugation process was carried out for collected dialyzed samples to evaluate the encapsulation efficiency (EE%) and RhB release profile. For this aim the dialyzed samples were centrifuged at 12,000 rpm for 1 h at 8 °C, the obtained supernatant and pellet were analysed by UV.

The obtained system was purified by centrifugation with a Thermo Scientific SL 16R Centrifuge (Thermo Scientific Inc., Waltham, MA, USA) at 12,000× g for 1 h and at 8 °C. The obtained supernatant was collected and the pellet was resuspended in water and centrifuged again at 10,000× g for 30 min at 2 °C. After this washing, NPs were finally resuspended in water.

The amount of free Cur in the PNP was calculated to determine the entrapment efficiency (EE%). PNP were centrifugated at 12,000 rpm for 1 h at 8 °C using a Thermo Scientific SL16R centrifuge (ThermoFisher Scientific, Waltham, MA, USA) to eliminate unentrapped drug in the supernatant. The amount of Cur in the supernatant was determined spectrophotometrically using a UV-Vis 1601 spectrophotometer (Shimadzu Italia, Milan, Italy) at a wavelength of 470 nm.
The calibration curve for the quantitative evaluation of Cur was linear in the following range: 1.61–25.80 µg/mL (R² = 0.9997); the EE% was calculated using the following equation: $Entrapmentefficiency\%=\frac{Wtotal-Wfree}{Wtotal}\times 100$
where W total and W free are the weight of Cur initially added in the formulation and the weight of free Cur in the supernatant, respectively.
The percentage of Cur encapsulated into SLN was determined by filtration using a Pellicon XL tangential ultrafiltration system (Millipore, Milan, Italy) equipped with a polyethersulfone Biomax 1000 membrane (molecular weight cut off = 1,000,000). An amount of lyophilized Cur-SLN was solubilized in dichloromethane and the Cur content was measured by UV spectrophotometry at 425 nm (Lambda 52, PerkinElmer, Waltham, MA, USA). Calibration curves for the validated UV assays of drug were run on six solutions in the concentration range 10–100 μg/mL (R² > 0.99).