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Zhao et al Dovepress FTIr analysis The samples were combined with potassium bromide, and the mixtures of the samples and potassium bromide were pressed into a transparent tablet. The FTIR spectra for the samples were recorded on an FTIR Perkin Elmer 1720 (Perkin Elmer, USA) in the transmission mode with the wave number rang- ing from 4,000 to 400 cm-1. XrPD analysis XRPD was performed by an X-ray diffractometer with a Cu Kα (λ =1.5405 Å) radiation (D8 Advance; Bruker AXS, Germany). The measurement was carried out in a 2θ range of 5°~45° with a 0.02° step size and 10° min-1 scan speed with a 2 D detector at 40 kV and 40 mA. Thermal analysis DSC samples were analyzed by DSC thermogram analysis (Simultaneous Thermal Analyzer [STA] 6000; Perkin Elmer, MA, USA) at a heating rate of 10°C min-1 over a temperature range of 25°C–400°C in a nitrogen (N2) atmosphere. Each sample was sealed separately in a standard aluminum pan. TG analysis was carried out using a Shimadzu TG analyzer (TGA50; Kyoto, Japan) in a nitrogen atmosphere. The heat- ing rate of the experiment was 10°C min-1. Nitrogen flow was maintained at 50 mL⋅min-1. solubility and dissolution rate measurements Solubility and dissolution rate tests of the original curcumin and the curcumin nanoparticles were conducted using a modified dialysis bag method. An excessive amount of each sample (10 mg) was dispersed in 5 mL of PBS (pH 7.4) and placed in a pretreated dialysis bag (Molecular Weight: 12,000–14,000 Daltons), and then the bag was put into 50 mL of PBS and incubated in a water bath at 37°C and 60 rpm. At a specific time, 1 mL of the solution was removed, fol- lowed by centrifugation (10,000× g, 10 minutes). Next, the concentration of the supernatant was detected by UV spectrometry (PerkinElmer Lambda 18; USA) at 410 nm. The dissolution rate was calculated in terms of the curcumin concentration and incubation time. Each experiment was carried out in triplicate. Results and discussion surface morphology and particle size of curcumin nanoparticles Figure 2 shows the surface morphology of the original curcumin powders before the SEDS process. The original curcumin powders were irregular and exhibited a mean size of approximately 3.58 μm. The experimental design and results of 24 FFD experiments are presented in Table 2. Figure 3 shows the SEM micrographs of the curcumin nanoparticles fabricated by the SEDS process in different runs, the details of which are listed in Table 2. It can be concluded from Figure 3 that the curcumin nanoparticles possessed an irregular spheri- cal morphology with a mean particle size from approximately 325 to 1,024 nm. The surface morphology of the biggest and smallest curcumin particles are shown in Figure 3A and B, respectively. Therefore, optimal conditions for preparing the smallest curcumin nanoparticles (325 nm) were as follows: P =20 MPa; T =35°C; flow rate of the solution =0.5 mL⋅min-1; and concentration of the solution =0.5%. Evidently, the SEDS process is an effective way to prepare curcumin nanoparticles. Moreover, by adjusting the different process parameters of the SEDS process, curcumin nanoparticles with controllable particle size can be prepared successfully. Influence of process parameters on particle size The FFD is a suitable technique to estimate the effects of process parameters on the process outcomes. For the evalu- ation of the main effect of process parameters including the precipitation pressure (A), precipitation temperature (B), flow rate of curcumin solution (C), and concentration of curcumin solution (D) on the mean particle size of curcumin nanoparticles, the quantitative data analysis for the results shown in Table 2 was performed. Figures 4 and 5 shows the standardized effect of the factors on particle size and the main effects plot for particle size, respectively. Table 3 lists the estimated effects and coefficients for particle size. As shown in Figure 4 and Table 3, A–C (P,0.05) sig- nificantly affected the size of curcumin nanoparticles. How- ever, D (P.0.05) had an insignificant effect on particle size. × Figure 2 seM micrograph of the original curcumin powders. Abbreviation: seM, scanning electron microscopy. International Journal of Nanomedicine 2015:10 3174 submit your manuscript | www.dovepress.com DovepressPDF Image | curcumin nanoparticles via dispersion by supercritical cO2
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