Preparation of irbesartan composite microparticles by supercritical aerosol solvent extraction system for dissolution enhancement

J. of Supercritical Fluids 153 (2019) 104594

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Preparation of irbesartan composite microparticles by supercritical aerosol solvent extraction system for dissolution enhancement Tingyuan Yan a , Yi Zhang c , Mengru Ji a , Zhixiang Wang c , Tingxuan Yan a,b,∗ a b c

School of Chemistry and Chemical Engineering, Anhui University of Technology, Ma’anshan, Anhui 243002, PR China Biochemical Engineering Research Center, Anhui University of Technology, Ma’anshan, Anhui 243002, PR China School of Engineering, China Pharmaceutical University, Nanjing 210009, PR China

h i g h l i g h t s

g r a p h i c a l

a b s t r a c t

• Irbesartan microparticles and its composite microparticles were prepared by the ASES process for the first time. • The physicochemical of Irbesatan and the its composites were investigated and compared. • The solubility and dissolution rate of Irbesatan microparticles were improved obviously. • ASES Irbesartan composite microparticles should be a candidate for drug delivery system.

a r t i c l e

i n f o

Article history: Received 22 June 2019 Received in revised form 21 July 2019 Accepted 15 August 2019 Available online 17 August 2019 Keywords: Irbesartan Supercritical aerosol solvent extraction system Solubility Dissolution enhancement Solid dispersion

a b s t r a c t In this study, irbesartan (IST) microparticles, an IST /hydroxypropyl-␤-cyclodextrin (HP-␤-CD) inclusion complex, and an IST/polyvinylpyrrolidone (PVP) complex were prepared using a supercritical aerosol solvent extraction system (ASES). The goal was to improve the solubility and dissolution rate of IST, which is an angiotensin II receptor blocker and exhibits solubility-limited oral bioavailability in pharmacokinetics. It is noteworthy that these three drug delivery systems show a higher solubility and dissolution rate of IST compared with raw IST. Fourier-transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy analyses were conducted to study the physicochemical properties of IST before and after ASES processing, and to confirm the formation of the IST complexes with HP-␤-CD and PVP. This study provides valuable information for the potential clinical application of IST microparticles and IST composite particles synthesized using the ASES process. © 2019 Elsevier B.V. All rights reserved.

1. Introduction

∗ Corresponding author at: No. 59 Hudong Road, Ma’anshan, Anhui 243002, PR China. E-mail address: [email protected] (T. Yan). https://doi.org/10.1016/j.supflu.2019.104594 0896-8446/© 2019 Elsevier B.V. All rights reserved.

In drug delivery systems, the bioavailability of orally administered drugs is always determined by the solubility in physiological fluids and the intestinal permeability. Generally, for poorly-watersoluble drugs, which fall into the biopharmaceutical classification system (BSC) class II category, the dissolution process is the major rate-limiting step [1–4]. The primary factors that affect the

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dissolution rate, including the diffusion coefficient, surface area, mass concentration, and diffusion thickness, can be calculated using the Noyes–Whitney equation [5]. The Hixson–Crowell equation is derived from the Noyes–Whitney equation, and it expresses the inverse correlation between the particle size and dissolution rate. Some poorly soluble drugs or materials have been prepared as micro- or nanoparticles to improve their dissolution rates, oral bioavailability as well as to use in medical field [6–10]. Instead of particle size reduction, many prefer adding excipients such as surfactants, polymers, and emulsifiers to achieve this purpose [4,11–14]. Among the large numbers of pharmaceutical excipients, polyvinylpyrrolidone (PVP) and cyclodextrins (CDs) are widely used to enhance the dissolution rate of poorly soluble drugs [15]. Kang, Marco, Kim and so on have used pvp or cyclodextrin composite particles in field of catalysis, drug and food fields [14–16]. In addition, CDs and PVP are very cheap and easy to obtained. Adeoye et al. prepared ibuprofen/hydroxypropyl-␥-cyclodextrin inclusion complexes with a particle size of 2.28 ␮m using supercritical-CO2 assisted spray drying; these inclusion complexes are particularly useful for the development of pulmonary drug delivery systems [16]. PVP can work as an inhibitor of crystal growth when co-precipitating with crystalline substances [2,17,18]. Therefore, hydrophobic drugs in solid dispersions typically have smaller particle sizes, as well as better dispersibility and wettability. At present, there are many forms of PVP with different molecular weights. In this study, PVP K30, with an average molecular weight of 40,000, was applied. CDs are often used as complexing agents in pharmaceutical dosage form development. Their hydrophobic interior cavity can harbor drug compounds, whereas their hydrophilic external surface has an affinity for aqueous media [19,20]. Hydroxypropyl-␤-cyclodextrin (HP-␤-CD), which is a CD derivative, can promote the dissolution and absorption of insoluble drugs, thus improving their bioavailability [21–24]. Compared with other CDs, HP-␤-CD is more widely used in the pharmaceutical industry owing to its higher aqueous solubility and better ability to harbor drug molecules. Irbesartan (IST), an angiotensin II receptor antagonist, was originally approved by the US Food and Drug Administration with a brand name of “Avapro” in 1997. IST tablets are used to treat high blood pressure via the oral route, which has been considered the most suitable administration method [25]. However, this drug suffers from the drawback of poor water solubility, which brings about a big challenge in the drug development industry. To enhance the dissolution rate of IST in oral solid dosage form, some formulations such as mesoporous molecules, solid dispersions, and CD inclusions, and techniques such as self-emulsification have been applied [26–30]. However, no research on preparing IST as microparticles, or formulation of composite particles using a supercritical aerosol solvent extraction system (ASES) has been reported. Hence, this study was focused on improving the solubility and dissolution rate by reducing the particle size of the drug or producing drug composite particles. The ASES technology is based on the mechanism of anti-solvent crystallization or precipitation. Different supercritical processes for particles formation are classified based on the behavior of supercritical fluid as solven (rapid expansion of supercritical solutions (RESS)), solute (particle formation from gas-saturated solutions (PGSS)), antisolvent anti-solvent(supercritical antisolvent (SAS), gaseous anti-solvent (GAS), aerosol solvent extraction system (ASES), precipitation with compressed anti-solvent (PCA), solution enhanced dispersion by supercritical fluids (SEDS))and some other improved methods on the base of supercritical fluid process [16,31]. In general, the environment-friendly supercritical carbon dioxide (SC-CO2 ) is chosen as the anti-solvent with respect to the solute, which has a stronger dissolving capacity compared to

the solvent [31,32]. Owing to their unique characteristics, poorlywater-soluble drugs can be manufactured not only as micro- or nanoparticles but also as composite formulations [9,33–36]. Owing to these advantages, the ASES process was chosen to prepare drug composite particles. In this process, the drug solution was pumped into the precipitation vessel through a nozzle with an inner diameter of 75 ␮m. Immediately, it attained a high supersaturation state as a result of almost all the solvent dissolving in the SC-CO2 . Thereafter, the residual solvent could be extracted with the SC-CO2 from the vessel, and the fine drug powder was precipitated. It is notable that particular systems can be set by varying the operating parameters, particularly the operating temperature, operating pressure, and solution concentration [37–41]. In this study, we prepared IST microparticles and IST composite particles with HP-␤-CD and PVP K30 using ASES technology. Irbesartan microparticles and its composite microparticles were prepared to improve the solubility and dissultion rate of Irbesartan, so as to improve its clinical application value. These particles were characterized using scanning electron microscopy (SEM; morphology), powder X-ray diffraction (PXRD; crystallinity), Fourier-transform infrared spectroscopy (FTIR; drug structure), and a USP II dissolution apparatus (dissolution profile). After the ASES process, the pharmacokinetic properties of IST improved obviously.

2. Materials and methods 2.1. Materials IST (purity >97%) and the IST standard (purity ≥98.0%) were provided by Zhejiang Huahai Pharmaceutical Co., Ltd. HP-␤-CD with a molar substitution of 0.6 was purchased from Yuan Ye Biotechnology Co., Ltd. PVP K30 was purchased from Sinopharm Chemical Reagent Co., Ltd. Carbon dioxide with a high purity of 99.9% was supplied by Nanjing Spring Industrial Gas Plant (China). Dimethyl sulfoxide (purity ≥99.5%) and acetone (purity ≥99.7%) were purchased from Guoyao Chemical Co., Ltd. (Shanghai, China). All the other chemicals were of HPLC or analytical grade. 2.2. Physical mixing IST and PVP, and IST and HP-␤-CD were accurately weighed with ratios of 1:1 (w/w) and 1:1 (M/M), respectively. Thereafter, they were tumble-mixed for 10 min. These physical mixtures (PMs) were used as contrasts in subsequent analytical characterization. 2.3. Supercritical aerosol solvent extraction system IST was completely dissolved by mixing in organic solvents containing acetone– dimethyl sulfoxide (7:1, v/v), at different initial concentrations. When preparing IST composite particles, two types of solutions were needed. One was a 1:1 mass ratio of IST and PVP K30 dissolved in dichloromethane, and the other was a 1:1 M ratio of IST and HP-␤-CD dissolved in a 9:1 (v/v) mixture of ethanol and dimethyl sulfoxide. Fig. 1 shows a schematic of the particular supercritical ASES instrument (Applied Separations, US) that was used in this study. In all the cases, SC-CO2 and the solution were passed at flow rates of 5 L/min and 0.8 mL/min, respectively. At the beginning of the ASES process, the precipitation vessel (internal volume =300 mL) was filled with SC-CO2 , which had been heated and pressurized to a pre-determined point. Backpressure regulation was used to manipulate the flow rate of SC-CO2. The prepared solution was pumped into the vessel; meanwhile, SC-CO2 was continuously circulated until the residual solvents were exhausted. The

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Fig. 1. Schematic of ASES apparatus. (1) CO2 storage tank, (2) low-temperature thermostat, (3) high-pressure pump, (4) preheater, (5) solution, (6) high-pressure infusion pump, (7) precipitation vessel, and (8) separator.

precipitation of microparticles occurred at the wall and the bottom of the vessel, as they were retained by a metal filter.

1 mL/min. The column temperature was maintained at 25 ◦ C and the signal was monitored at 245 nm.

2.4. Analytical methods

2.4.6. Drug content To measure the drug contents of the ASES-processed composites, the powder samples were weighed accurately and dissolved in methanol. After 30 min of ultrasonic vibration, the concentrations of IST in the composite solutions were determined using HPLC.

2.4.1. Scanning electron microscopy The surface morphologies of raw IST, ASES-processed IST, IST/PVP K30, and IST/HP-␤-CD were studied using a scanning electron microscope (SSX550, Shimadzu, Japan). The samples were placed on an aluminum stub with double-sided adhesive carbon tape, and then coated with a thin layer of gold using a sputter module, before analysis. 2.4.2. Fourier-transform infrared spectroscopy Infrared spectra were recorded using a 4100 Type A FT-IR spectrometer (Jasco, Japan) equipped with a TGS detector. The spectral scanning range was between 4000 and 400 cm−1 with a speed of 12 cm/min. Each spectrum had a resolution of 4 cm−1 and an accumulation of 4. 2.4.3. Powder X-ray diffraction The crystalline patterns of various samples were obtained using a powder X-ray diffractometer (D8 Advance, Bruker, Germany) with nickel slit copper as the source of radiation. All the powder samples were examined in the 2␪ angle range between 2.5◦ and 40◦ . The scan rate was 4◦ /min, and the generation was set up at 40 kV and 40 mA. 2.4.4. Differential scanning calorimetry The thermal characteristics of the samples were determined using a differential scanning calorimeter (DSC 204 F1, Netzsch). Approximately 5 mg of each sample was placed on an aluminum pan. The sample cell was operated at a heating rate of 20 ◦ C/min from normal to 300 ◦ C. 2.4.5. Solubility determination via high-pressure liquid chromatography The powders were shaken for 48 h in distilled water using a constant-temperature shaker and then filtered with a 0.22␮m membrane filter. The solubility of these saturated aqueous solution was determined via high-pressure liquid chromatography (HPLC). IST was detected using a C18 reverse phase column (250 mm × 4.6 mm, 5 ␮m) with a mobile phase of methanol–water–phosphoric acid (36:64:0.1, v/v) at a flow rate of

2.4.7. In-vitro dissolution profile In-vitro dissolution tests were conducted in a simulated gastric juice (pH = 1.2) using the USP II dissolution apparatus. In each dissolution test, the sample, which was equivalent to 10 mg of IST, was accurately weighed and dispersed into 900 mL (under sink conditions) of dissolution media with a speed of 100 rpm at 37 ± 0.1 ◦ C. Aliquots (5 mL, each) were withdrawn and filtered at specific time intervals of 5, 10, 15, 20, 25, 30, 40, 50, 60, 90, and 120 min in the tests for raw IST and ASES-processed IST. The other set of time intervals was 2, 5, 8, 10, 15, 20, 25, 30, 40, 50, and 60 min. After each sampling, an equal volume of fresh solution was added immediately. The concentration of IST in the filtrated solutions was measured using HPLC. Each test was performed in triplicate. 3. Results and discussion 3.1. Effects of temperature and pressure on particle size of IST As most earlier research focused on the effects of the pressure and temperature on the particle size of drugs, the other process parameters were fixed based on our previous preliminary experiment (solution rate =1 mL/min, nozzle diameter = 50 ␮m, CO2 flow rate = 0.35 L/min, concentration =5 mg/mL). As shown in Table 1, when the temperature was set at 40 ◦ C, the particle size of processed IST decreased from 8.32 ± 0.46 to 3.28 ± 0.37 ␮m as the pressure increased from 8 to 16 MPa. This may have been because a smaller particle size of IST was obtained as the degree of supersaturation and the diffusion rate increased; this depended on the precipitation pressure. Chen et al. [42], Yan et al. [43], and Gokhale et al. [44] also reported similar phenomena. When the pressure was set at 16 MPa, although the temperature changed from 35 to 45 ◦ C, it had little influence on the particle size of processed IST. It seems that although a rise in the temperature (from 35 to 50 ◦ C) can increase the supersaturation degree of the drug, this increase in

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Table 1 Effects of pressure and temperature on particle size of IST. Number

Pressure (MPa)

Temperature (◦ C)

Particle Size (␮m)

1 2 3 4 5 6 7 8

8 12 16 16 16 16 12 8

40 40 40 35 45 50 50 50

8.32 ± 0.46 6.54 ± 0.56 3.28 ± 0.37 3.58 ± 0.43 3.79 ± 0.36 4.03 ± 0.53 6.32 ± 0.59 8.37 ± 0.52

the supersaturation degree is not enough to obviously decrease the particle size of IST. As most of the drug should be processed at a low temperature, samples with a particle size of 3.28 ± 0.37 ␮m, prepared at optimized conditions (16 MPa and 40 ◦ C), were obtained for further analysis. 3.2. Scanning electron microscopy and particle size distribution of particles Fig. 2 presents the micrographs of raw IST, ASES-processed IST, IST/PVP K30, and IST/HP-␤-CD composite particles. SEM and particle size analysis show that the mean particle size of raw IST is 20.23 ± 1.89 ␮m; raw IST (Fig. 2A) exhibits irregularly shaped crystals with wide particle size distributions of D(0.1) = 7.93 ␮m and D(0.5) = 32.34 ␮m. In contrast, the particle size of ASESprocessed IST is 3.28 ± 0.37 ␮m; ASES-processed IST (Fig. 2B) becomes significantly smaller in size and nearly amorphous, with the disappearance of the rod-like shape. The particle size distributions also narrowed to D(0.1) = 0.98 ␮m and D(0.5) = 6.72 ␮m. The ASES-processed composite particles of IST/HP-␤-CD and IST/PVP K30 are shown in Figs. 2C and 2D, respectively. Two drug sites in the composites exhibit corresponding mechanisms. Based on the morphology, it is easy to distinguish the drug particles from the

respective excipients and to understand the interaction between them. In the solid dispersion, IST microparticles adhere to the surface of PVP K30. On the other hand, in the inclusion complex, the microparticles are harbored in the interior cavity of HP-␤-CD and undermine the spherical surface. Based on earlier research [17,19], it was widely agreed that many small-molecule drugs can undergo complexation and enter into the hydrophobic cavity of CDs. Fig. 2C shows the particle size distribution of the IST/HP-␤-CD particles. The mean particle size is 5.23 ␮m and the particle size distributions narrow to D(0.1) = 1.28 ␮m and D(0.5) = 8.72 ␮m. The results in Fig. 2 show that IST/HP-␤-CD particles have better crystal morphology and particle uniformity. All these results prove that the ASES process, which is a new type of pharmaceutical processing technology, produces a narrow and uniform distribution of the particle size. 3.3. Fourier-transform infrared spectroscopy analysis The FTIR spectra of raw IST, ASES-processed IST, IST/HP␤-CD, IST/PVP, and their physical mixtures are presented in Fig. 3. Raw IST exhibits characteristic absorption peaks at several wave numbers as follows: aliphatic CH3 stretching vibrations occur at 2959 and 2873 cm−1 , the two strong peaks at 1732 and 1616 cm−1 correspond to CO and C –N stretching, and 1,2-disubstituted benzene bonds absorb at 757 cm−1 . In comparison, the FT-IR spectra (Fig. 3B) of ASES-processed IST display no significant difference from those shown in Fig. 3A, suggesting that the structure of the IST molecules is maintained after the ASES process. The characteristic absorption peaks of IST, the physical mixture of IST and HP-␤-CD (Fig. 3D), and ASES-processed IST/HP-␤-CD (Fig. 3E) indicate that IST exists in the physical mixture and ASESprocessed IST/HP-␤-CD. However, a comparison of the FTIR spectra of the physical mixture and IST/HP-␤-CD indicates that the intensity of the characteristic absorption peaks decreases. This may be because IST exists as an amorphous state in the complex. The characteristic absorption peaks of IST 1616 cm-1 are not exhibited by

Fig. 2. SEM images of (A) raw IST (×1000), (B) ASES-processed IST (prepared at 15 MPa, 54 ◦ C, 5 mg/mL) (×3500), (C) ASES-processed IST/PVP K30 (×3500), and (D) ASESprocessed IST/HP-␤-CD (×2000).

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Fig. 3. FT-IR spectra of (A) raw IST, (B) ASES-processed IST, (C) raw HP-␤-CD, (D) IST/HP-␤-CD physical mixture, (E) ASES-processed IST/HP-␤-CD, (F) raw PVP, (G) IST/PVP physical mixture, and (H) ASES-processed IST/PVP.

the physical mixture of IST and PVP (Fig. 3G) and ASES processed IST/PVP(Fig. 3H). The reason may be that the there is a big broad peak in the FTIR spectra of PVP around 1700 cm-1 , which cover the characteristic peak of the the IST such as aliphatic CH3 stretching vibrations occur at 1616 cm−1 . The strong peak at 1732 cm-1 correspondingly belong to C O still presents at the IST/PVP physical mixture. However, the strong peak at 1732 cm-1 disappears at the FTIR spectrogram of IST/PVP complex, which indicate that there is a hydrogen-bond interaction between IST and PVP. Comparing the FTIR spectra of physical mixture and IST/PVP, the intension of characteristic absorption peaks also decrease. This phenomenon is in accordance with that of IST/HP-␤-CD, which because IST exist as amorphous state in the IST/PVP complex. 3.4. Powder X-ray diffraction analysis The PXRD patterns of raw IST and ASES-processed IST are illustrated in Fig. 4. In Fig. 4A, the presence of several distinct peaks at diffraction angles (2␪) of 4.70◦ , 12.44◦ , 16.99◦ , 19.39◦ , and 23.15◦

reveals that raw IST exhibits a crystalline form. These sharp intensity peaks that indicate the crystalline nature of IST were still observed in the diffractogram of ASES-processed IST, implying that IST maintained its crystallinity and the amorphous state was not formed. However, it is important to interpret the difference in the values of the diffraction intensity. According to the theory of XRD, the peak intensity carries information on the absolute structure. Generally, an increase in the surface area exacerbates the structural defects of a crystal, resulting in a lower and broader intensity [45,46]. As shown in Fig. 4B, the micronization of IST significantly increases its surface area, and consequently, the corresponding peak intensities decrease. The PXRD patterns of raw HP-␤-CD, the IST/HP-␤-CD physical mixture, and ASES-processed IST/HP-␤-CD are respectively illustrated in Figs. 4C, 4D, and 4E. The characteristic peak at 12.44◦ disappears and that at 4.70◦ weakens. This is a further validation that IST exists as an amorphous state and undergoes complexation with HP-␤-CD. The PXRD patterns of raw PVP, the IST/PVP physical mixture and ASES-processed IST/PVP are respectively illustrated in

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Fig. 4. PXRD patterns of (A) raw IST, (B) ASES-processed IST, (C) raw HP-␤-CD, (D) IST/HP-␤-CD physical mixture, (E) ASES-processed IST/HP-␤-CD, (F) raw PVP, (G) IST/PVP physical mixture, and (H) ASES-processed IST/PVP.

Fig. 5. DSC curves of (A) raw IST, (B) ASES-processed IST, (C) raw HP-␤-CD, (D) IST/HP-␤-CD physical mixture, (E) ASES-processed IST/HP-␤-CD, (F) raw PVP, (G) IST/PVP physical mixture, and (H) ASES-processed IST/PVP.

Figs. 4F, 4 G, and 4H. In Fig. 4H, the characteristic peak of IST at 12.44◦ is absent and that at 4.70◦ is weaker. This phenomenon may be due to the recrystallization of IST in PVP. 3.5. Differential scanning calorimetry analysis The DSC curves of raw IST, raw HP-␤-CD, the IST/HP-␤-CD physical mixture, and ASES-processed IST/HP-␤-CD are shown in Fig. 5. Fig. 5A indicates that the melting point of IST is 180.8 ◦ C. Although IST has two crystal forms [44,47], the melting point of IST does not change after ASES processing (see Fig. 5C), which proves that the crystal form of IST does not change. As shown in Figs. 5B and 5D, the decalescence peaks present in the DSC curve of raw IST are absent in the DSC curve of ASES-processed IST/HP-␤-CD, implying that IST may have entered into the hydrophobic cavity of HP-␤-CD. All these results prove that IST exists as an amorphous state and undergoes complexation with HP-␤-CD. The DSC curves of raw PVP, the IST/PVP physical mixture, and ASES-processed IST/PVP are respectively illustrated in Figs. 5F, 5 G, and 5H. In Fig. 5G, the DSC curves of IST and the PVP physical mixture show a melting peak of IST at 180.8 ◦ C. On the other hand, this peak is absent in the DSC curve of the IST/PVP complex obtained via the ASES process (Fig. 5H) due to the inhibitory effect of PVP on crystal growth, which stabilizes the amorphous form of IST. This phenomenon is consistent with the results reported in the literature [28]. 3.6. Aqueous solubility and drug loading The total drug contents in the ASES-processed IST/PVP K30 and IST/HP-␤-CD composites (measured using HPLC) were 48.20 ± 0.28% and 7.51 ± 0.48%, respectively. After 48 h of shaking, the solubility of raw IST in distilled water was 15.69 ␮g/mL, conforming to its practically insoluble nature. As shown in Fig. 6, the solid binary systems of IST and PVP K30 improve the aqueous solubility of the drug, with an approximately 1.6-fold increase in the

Fig. 6. Aqueous solubility of (A) raw IST, (B) ASES-processed IST, (C) physical mixture of IST and PVP K30 (PM1), (D) ASES-processed IST/PVP K30, (E) physical mixture of IST and HP-␤-CD (PM2), and (F) ASES-processed IST/HP-␤-CD.

solubility of the physical mixture (PM1) and a 6.1-fold increase in the solubility of the ASES-processed particles. Analogously, the aqueous solubilities in the solid binary systems of IST and HP-␤CD are 32.98 (PM2) and 83.46 ␮g/mL, respectively. The difference in the aqueous solubilities of the physical mixtures and ASESprocessed particles indicates the formation of solid dispersions and inclusion complexes. However, mixing IST with the hydrophilic excipients (PVP K30, HP-␤-CD) may have also improved the solubility. This may have been because, during tumble-mix treatment, limited interaction (surface contact) between the excipients and IST could occur, leading to an increased wettability of the drug. On the other hand, compared to that of the IST particles mentioned above, the aqueous solubility of IST prepared at optimized conditions was significantly enhanced to 117.25 ␮g/mL, owing to the reduction in the particle size.

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Fig. 7. A:Dissolution profiles of (A) raw IST and (B) ASES-processed IST in simulated gastric juice (pH = 1.2). B: Dissolution profiles of (C) physical mixture of IST and PVP K30 (PM1), (D) ASES-processed IST/PVP K30, (E) physical mixture of IST and HP-␤-CD (PM2), and (F) ASES-processed IST/HP-␤-CD in simulated gastric juice (pH = 1.2).

3.7. In-vitro dissolution profile The dissolution profiles of IST and ASES-processed IST are compared in Fig. 7A. Raw IST exhibited a low dissolution rate (only 35% was dissolved after 120 min), which was consistent with the feature of poor water solubility. However, it took less than 25 min for ASES-processed IST to attain an 80% cumulative dissolution. This enhanced dissolution rate suggests that micronization is a feasible method to improve oral bioavailability. The dissolution rates of the ASES-processed IST/PVP K30 and IST/HP-␤-CD particles were measured, with the physical mixtures of IST and PVP K30 (PM1), and IST and HP-␤-CD (PM2) taken as reference. As shown in Fig. 7B, the dissolution rate of the ASESprocessed IST/HP-␤-CD complex is remarkably enhanced, with the profile indicating that 90% of IST is dissolved within 20 min. This outcome can probably be attributed to the formation of the inclusion complex with HP-␤-CD in the ASES process. The curve of ASES-processed IST/PVP K30 is similar. In the initial period of release, the solid dispersion exhibits a slightly faster dissolution rate. This may be due to the different drug sites in the composites, as well as the effect of the excipients. A comparison of the physical mixtures and raw IST reveals that merely adding hydrophilic excipients can enhance the dissolution to some extent. In addition, these figures precisely indicate that the dissolution rate has a positive association with the solubility. Based on these results, supercritical ASES shows a huge potential for application in pharmaceutical preparations to ameliorate the poor water-solubility of drugs.

4. Conclusions In this study, we prepared IST composites co-precipitated with PVP K30 and HP-␤-CD using ASES technology, with a significant enhancement in the aqueous solubility and dissolution rate. Micronization was also validated as an effective way to improve the solubility. ASES-micronized IST showed a 7.5-fold increase in the drug solubility, compared with raw IST. It is noteworthy that the solubility of IST microparticles is higher than that of the IST/HP-␤-CD and IST/PVP complexes. Furthermore, the dissolution rate is also enhanced, compared to that of raw IST. FT-IR, DSC, and PXRD analyses revealed that the structure and crystallinity of IST was maintained after complexation with HP-␤-CD. Therefore, supercritical fluid technology deserves to be proposed as a useful technique for micronization, as well as for preparing solid

dispersions or inclusion complexes in order to ameliorate the poor water-solubility of drugs. Acknowledgements We gratefully acknowledge the National Undergraduate Training Program for Innovation and Entrepreneurship (201910360028) and Natural Science Foundation of Anhui University of Technology (RD17100193). References [1] V. Majerik, G. Charbit, E. Badens, G. Horváth, L. Szokonya, N. Bosc, E. Teillaudc, Bioavailability enhancement of an active substance by supercritical antisolvent precipitation, J. Supercrit. Fluids 40 (2007) 101–110. [2] P. Kanaujia, P. Poovizhi, W.K. Ng, R.B.H. Tan, Amorphous formulations for dissolution and bioavailability enhancement of poorly soluble APIs, Powder Technol. 285 (2015) 2–15. [3] T. Yasuji, H. Takeuchi, Y. Kawashima, Particle design of poorly water-soluble drug substances using supercritical fluid technologies, Adv. Drug Deliv. Rev. 60 (2008) 388–398. [4] S. Kumar, D. Bhargava, A. Thakkar, S. Arora, Drug carrier systems for solubility enhancement of BCS class II drugs: a critical review, Crit. Rev. Ther. Drug Carrier Syst. 30 (2013) 217–256. [5] A. Tabernero, E.M. Martín del Valle, M.A. Galán, Supercritical fluids for pharmaceutical particle engineering: methods, basic fundamentals and modelling, Chem. Eng. Process. 60 (2012) 9–25. [6] B.Q. Chen, R.K. Kankala, S.B. Wang, A.Z. Chen, Continuous nanonization of lonidamine by modified-rapid expansion of supercritical solution process, J. Supercrit. Fluids 133 (2018) 483–493. [7] R.K. Kankala, Z. K, X.N. Sun, C.G. Liu, S.B. Wang, A.Z. Chen, Cardiac tissue engineering on the nanoscale, ACS Biomater. Sci. Eng. 4 (2018) 800–818. [8] Y. Zu, W. Wu, X. Zhao, Y. Li, W. Wang, C. Zhong, Y. Zhang, X. Zhao, Enhancement of solubility, antioxidant ability and bioavailability of taxifolin nanoparticles by liquid antisolvent precipitation technique, Int. J. Pharm. 471 (2014) 366–376. [9] R. Campardelli, L. Baldino, E. Reverchon, Supercritical fluids applications in nanomedicine, J. Supercrit. Fluids 101 (2015) 193–214. [10] A. Fattahi, J. Karimi-Sabet, A. Keshavarz, A. Golzary, M. Rafiee-Tehrani, F. Dorkoosh, Preparation and characterization of simvastatin nanoparticles using rapid expansion of supercritical solution (RESS) with trifluoromethane, J. Supercrit. Fluids 107 (2016) 469–478. [11] M.S. Kim, I.H. Baek, Fabrication and evaluation of valsartan-polymersurfactant composite nanoparticles by using the supercritical antisolvent process, Int. J. Nanomedicine 9 (2014) 5167–5176. [12] I. Kikic, Polymer–supercritical fluid interactions, J. Supercrit. Fluids 47 (2009) 458–465. [13] I. Kikic, F. Vecchione, Supercritical impregnation of polymers, Curr. Opin. Solid State Mater. Sci. 7 (2003) 399–405. [14] E. Franceschi, A.M. De Cesaro, M. Feiten, S.R.S. Ferreira, C. Dariva, M.H. Kunita, A.F. Rubira, E.C. Muniz, M.L. Corazza, J.V. Oliveira, Precipitation of ␤-carotene and PHBV and co-precipitation from SEDS technique using supercritical CO2 , J. Supercrit. Fluids 47 (2008) 259–269.

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T. Yan, Y. Zhang, M. Ji et al. / J. of Supercritical Fluids 153 (2019) 104594

[15] H. Nerome, S. Machmudah, R. Wahyudiono, T. Fukuzato, Y. Higashiura, Y. Youn, M. Lee, Goto, Nanoparticle formation of lycopene/␤-cyclodextrin inclusion complex using supercritical antisolvent precipitation, J. Supercrit. Fluids 83 (2013) 97–103. [16] O. Adeoye, C. Costa, T. Casimiro, A.A. Ricardo, Preparation of ibuprofen/hydroxypropyl-␥-cyclodextrin inclusion complexes using supercritical CO2 -assisted spray drying, J. Supercrit. Fluids 133 (2018) 479–485. [17] E. Adeli, Irbesartan-loaded electrospun nanofibers-based PVP K90 for the drug dissolution improvement: fabrication, in vitro performance assessment, and in vivo evaluation, J. Appl. Polym. Sci. 132 (2015) 42212–42221. [18] V. Prosapio, I. De Marco, M. Scognamiglio, E. Reverchon, Folic acid–PVP nanostructured composite microparticles by supercritical antisolvent precipitation, Chem. Eng. J. 277 (2015) 286–294. [19] S.R. Rudrangi, R. Bhomia, V. Trivedi, G.J. Vine, J.C. Mitchell, B.D. Alexander, S.R. Wicks, Influence of the preparation method on the physicochemical properties of indomethacin and methyl-beta-cyclodextrin complexes, Int. J. Pharm. 479 (2015) 381–390. [20] S.W. Jun, M.S. Kim, J.S. Kim, H.J. Park, S. Lee, J.S. Woo, S.J. Hwang, Preparation and characterization of simvastatin/hydroxypropyl-beta-cyclodextrin inclusion complex using supercritical antisolvent (SAS) process, Eur. J. Pharm. Biopharm. 66 (2007) 413–421. [21] I. De Marco, E. Reverchon, Supercritical antisolvent micronization of cyclodextrins, Powder Technol. 183 (2008) 239–246. [22] L. Zhang, W. Zhu, Q. Lin, J. Han, L. Jiang, Y. Zhang, Hydroxypropyl-beta-cyclodextrin functionalized calcium carbonate microparticles as a potential carrier for enhancing oral delivery of water-insoluble drugs, Int. J. Nanomedicine 10 (2015) 3291–3302. [23] S.Y. Lee, I.I. Jung, J.K. Kim, G.B. Lim, Preparation of itraconazole/HP-␤-CD inclusion complexes using supercritical aerosol solvent extraction system and their dissolution characteristics, J. Supercrit. Fluids 44 (2008) 400–408. [24] R. Zhou, F. Wang, Z. Guo, Y.L. Zhao, Preparation and characterization of resveratrol/ Hydroxypropyl-␤-Cyclodextrin inclusion complex using supercritical antisolvent technology, J. Food Process Eng. 35 (2012) 677–686. [25] D. Pan, G. Crull, S. Yin, J. Grosso, Low level drug product API form analysis-Avalide tablet NIR quantitative method development and robustness challenges, J. Pharm. Biomed. Anal. 89 (2014) 268–275. [26] M. Khanfar, M.M. Fares, M.S. Salem, A.M. Qandil, Mesoporous silica based macromolecules for dissolution enhancement of Irbesartan drug using pre-adjusted pH method, Microporous Mesoporous Mater. 173 (2013) 22–28. [27] B.R. Ganapuram, M. Alle, R. Dadigala, G. MangatayaruKotu, V. Guttena, Development, evaluation and characterization of surface solid dispersion for solubility and dispersion enhancement of irbesartan, J. Pharm. Res. 7 (2013) 472–477. [28] A. Homayouni, F. Sadeghi, J. Varshosaz, H.A. Garekani, A. Nokhodchi, Comparing various techniques to produce micro/nanoparticles for enhancing the dissolution of celecoxib containing PVP, Eur. J. Pharm. Biopharm. 88 (2014) 261–274. [29] Z.L. Zhang, Y. Le, J.X. Wang, J.F. Chen, Preparation of stable micron-sized crystalline irbesartan particles for the enhancement of dissolution rate, Drug Dev. Ind. Pharm. 37 (2011) 1357–1364. [30] R. Hirlekar, V. Kadam, Preformulation study of the inclusion complex irbesartan-beta-cyclodextrin, AAPS PharmSciTech 10 (2009) 276–281.

[31] R.K. Kankala, Y.S. Zhang, S.B. Wang, C.H. Lee, A.Z. Chen, Supercritical fluid technology: an emphasis on drug delivery and related biomedical applications, Adv. Healthc. Mater. 6 (2017), 1700433. [32] P. Xu, R.K. Kankala, Y. Pan, H. Yuan, S.B. Wang, A.Z. Chen, Overcoming multidrug resistance through inhalable siRNA nanoparticles-decorated porous microparticles based on supercritical fluid technology, Int. J. Nanomed. Nanosurg. 13 (2018) 4685–4698. [33] P. Sheth, H. Sandhu, D. Singhal, W. Malick, N. Shah, M. S. Kislalioglu. Nanoparticles in the pharmaceutical industry and the use of supercritical fluid technologies for nanoparticle production, Curr. Drug Deliv. 9 (2012) 269–284. [34] C. Domingo, J. Saurina, An overview of the analytical characterization of nanostructured drug delivery systems: towards green and sustainable pharmaceuticals: a review, Anal. Chim. Acta 744 (2012) 8–22. [35] A. Montes, M.D. Gordillo, C. Pereyra, E.J. Martínez de la Ossa, Supercritical CO2 precipitation of poly(l-lactic acid) in a wide range of miscibility, J. Supercrit. Fluids 81 (2013) 236–244. [36] S.P. Nalawade, F. Picchioni, L.P.B.M. Janssen, Supercritical carbon dioxide as a green solvent for processing polymer melts: processing aspects and applications, Prog. Polym. Sci. 31 (2006) 19–43. [37] F. Miguel, A. Martín, T. Gamse, M.J. Cocero, Supercritical anti solvent precipitation of lycopene : effect of the operating parameters, J. Supercrit. Fluids 36 (2006) 225–235. [38] P. Varughese, J. Li, W. Wang, D. Winstead, Supercritical antisolvent processing of ␥-Indomethacin: effects of solvent, concentration, pressure and temperature on SAS processed Indomethacin, Powder Technol. 201 (2010) 64–69. [39] E. Reverchon, I. De Marco, Mechanisms controlling supercritical antisolvent precipitate morphology, Chem. Eng. J. 169 (2011) 358–370. [40] I. De Marco, E. Reverchon, Influence of pressure, temperature and concentration on the mechanisms of particle precipitation in supercritical antisolvent micronization, J. Supercrit. Fluids 58 (2011) 295–302. [41] I. De Marco, M. Rossmann, V. Prosapio, E. Reverchon, A. Braeuer, Control of particle size, at micrometric and nanometric range, using supercritical antisolvent precipitation from solvent mixtures: application to PVP, Chem. Eng. J. 273 (2015) 344–352. [42] A.Z. Chen, L. Li, S.B. Wang, C. Zhao, Y.G. Liu, G.Y. Wang, Z. Zhao, Nanonization of methotrexate by solution-enhanced dispersion by supercritical CO2 , J. Supercrit. Fluids 67 (2012) 7–13. [43] T. Yan, Y. Cheng, Z. Wang, D. Huang, H. Miao, Y. Zhang, Preparation and characterization of baicalein powder micronized by the SEDS process, J. Supercrit. Fluids 104 (2015) 177–182. [44] A. Gokhale, B. Khusid, R.N. Dave, R. Pfeffer, Effect of solvent strength and operating pressure on the formation of submicrometer polymer particles in supercritical microjets, J. Supercrit. Fluids 43 (2007) 341–356. [45] J. Zhang, M.B. Clennell, K. Liu, D.N. Dewhurst, M. Pervukhina, N. Sherwood, Molecular dynamics study of CO2 sorption and transport properties in coal, Fuel 177 (2016) 53–62. [46] S. Parsons, H.D. Flack, T. Wagner, Use of intensity quotients and differences in absolute structure refinement, Acta Crystallogr. B Struct. Sci. Cryst. Eng. Mater. 69 (2013) 249–259. [47] E. Garcia, C. Hoff, S. Veesler, Dissolution and phase transition of pharmaceutical compounds, J. Cryst. Growth 237–239 (2002) 2233–2239.