Continuous and Scalable Process for the Production of Hollow

Subscriber access provided by UNIV OF WESTERN ONTARIO

Article

A continuous and scalable process for the production of hollow crystals of a poorly water-soluble active pharmaceutical ingredient for dissolution enhancement and inhaled delivery Fei Sheng, Pui Shan Chow, Yuancai Dong, Desmond Heng, Sie Huey Lee, and Reginald B. H. Tan Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.9b00292 • Publication Date (Web): 06 May 2019 Downloaded from http://pubs.acs.org on May 7, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

A continuous and scalable process for the production of hollow crystals of a poorly watersoluble active pharmaceutical ingredient for dissolution enhancement and inhaled delivery Fei Sheng, †,*, Pui Shan Chow†, Yuancai Dong†, Desmond Heng†, Sie Huey Lee†, Reginald B. H. Tan†‡,* †

Institute of Chemical and Engineering Sciences, A*STAR (Agency for Science, Technology and Research), 1 Pesek Road, Jurong Island, Singapore 627833, Singapore

‡

Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 119260, Singapore

Key worlds: Hollow crystal, Continuous crystallization, Spironolactone, Antisolvent precipitation, Dissolution enhancement, Dry powder inhaler (DPI)

1 ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract This study reports a new technique for the manufacture of micron-sized hollow crystals of a poorly water-soluble pharmaceutical compound, spironolactone, by a continuous and scalable antisolvent precipitation platform called a static mixer. Additives (PVP and Tween80) were added during antisolvent precipitation to achieve the diffusion-limited growth condition required for the formation of hollow crystals. Over 90% of the products out of the total yield would form hollow crystals as adequate time provided for crystal growth. PVP was found to be more effective in inducing hollow formation than Tween80. The suspensions from antisolvent precipitation were subjected to freeze drying or spray drying to obtain the final dried powder. The hollowness and morphology of the crystals were retained after freeze drying and spray drying although the crystallinity of the crystals was slightly reduced by the drying processes. The feasibility of applying such hollow crystals for oral and inhaled drug delivery was evaluated through in vitro dissolution study and aerosolization studies. The dissolution rate of spironolactone was significantly improved due to the high specific surface area of hollow crystals. In addition, a much improved aerosolization performance (~3-fold increase) over the raw drug demonstrates the value and importance of hollow crystals in enhancing the performance of inhaled therapeutics.


Page 2 of 31

Page 3 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Introduction Hollow crystal have been studied widely due to its specific properties, such as low density and high specific surface area

1-4.

According to the Noyes Whitney equation, increasing the specific

surface area leads to an increase in dissolution rate 5. This is unlike the size reduction approaches that normally require significant energy input

6

and would induce disorder, defects and even

amorphicity 7. Producing hollow crystals is a feasible strategy to improve the dissolution rate of poorly water soluble drugs through modifying particle morphology, subsequently enhancing the bioavailability 8-9. Also, hollow particles are expected to have better aerosol performance as they have much smaller aerodynamic diameters over solid rods of the same size (the former have lower densities)

10-11.

aerosolization

Previously, hollow particles had been shown to be beneficial in enhancing

12-14.

But traditional hollow active pharmaceutical ingredients (APIs) for aerosols

were normally obtained through direct spray drying of drug solution 15, in which the amorphous state of APIs consequently causes physico-chemical instability of the product. If the crystals were precipitated in a suspension first, the crystallinity of the particles collected from spray drying can be retained, offering better stability and shelf life 16. Hence, it would be beneficial to achieve both crystallinity and hollowness/low density in a particle. To date, there has been limited literature on such multi-faceted particles 17. Antisolvent precipitation is a simple, cost effective, and scalable approach to produce submicron particles

18-19.

At the same time, antisolvent precipitation offers greater flexibility in controlling

particle morphology 20-22. In a typical antisolvent precipitation, the poorly water-soluble active is first dissolved in a water-miscible organic solvent, and then rapidly mixed with the antisolvent, which is normally water. High supersaturation is generated after the mixing of solvent and antisolvent, resulting in fast nucleation rate and the production of a large number of nuclei. Bigger 3 ACS Paragon Plus Environment


Page 4 of 31

particles with various morphologies are subsequently produced through nanoparticle agglomeration or Ostwald ripening 23-24. Previous researches showed that hollow crystals can be obtained under proper experimental conditions in beakers or stirred tanks

25-28.

Hollow crystals

produced by antisolvent precipitation were believed to form under diffusion-limited growth mechanism, i.e., crystal centers stop growing while the edges of crystal surface continue to grow and form hollow, because it is easier for the drug molecules to diffuse to the edge of crystal surface than to the crystal center

4, 29-30.

The existence of stabilizer (such as tween 80 and PVP) would

increase nucleation rate and supersaturation consumption, preventing formation of dendritic particles. Furthermore, hydrogen bonding formed between drug molecules and stabilizer aids in the formation of superstructures via agglomeration of precipitated nanoparticles. However, for continuous and large scale antisolvent precipitation processes, slow and non-uniform mixing is a common problem, which could lead to the production of particles that have a wide size distribution 31-32.

Nevertheless, some unique continuous mixing devices enabling rapid and homogeneous

mixing have been studied, such as microfludics 33, membrane contactor 34, confined impinging jet mixers

31,

and T-mixer

35,

etc. Among these approaches, the static mixer is an efficient mixing

device for continuous precipitation. A static mixer consists of many identical and unmovable elements, which are assembled inside a tube, column or reactor in operation. These mixing elements possess generally tortuous structures and are able to distribute and recombine the feed fluids to realize a rapid and homogeneous mixing of the fluids. In addition, they possess many advantages, such as no additional energy input needed except pumping, compact space requirement, low equipment cost, easy-to-operate and suitability for continuous and large scale operation

36.

Static mixing has been successfully employed to produce nanoparticles of poorly


Page 5 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


water-soluble drugs

37-39.

However, to the best of our knowledge, no research has been reported

for continuous production of hollow crystals via the static mixing platform. Spironolactone, a poorly water-soluble Class II steroid was used as the model drug. Previously, a variety of approaches had been attempted to accelerate its dissolution rate, such as size reduction 40-41,

solid dispersion 42, complexation with cyclodextrin 43, and co-crystallization 44. Furthermore,

some previous research had also focused on enhancing the aerosol performance of spironolactone 45.

In this work, we aimed to produce hollow spironolactone crystals in a continuous process. In

particular, cavity formation under the influence of different additives was also investigated. Subsequent application of these hollow crystals to the drug delivery field was explored. Feasibility to the oral route was evaluated based on potential enhancements to the dissolution rate, while aerosol applications were evaluated based on in-vitro aerosolization studies. Experimental Section Materials Spironolactone (SP) was obtained from Wuhan Hezheng Biochemical Manufacture CO. Ltd, China. Tween80 and polyvinyl pyrrolidone (PVP K30) were purchased from Sigma-Aldrich. Clay (CLOISITE®Ca++) was a gift from Southern Clays Products Inc. Reagent grade ethanol was supplied by Fisher Scientific and deionized water was used. Molecular structures of SP, Tween80 and PVP are presented in Figure 1. Precipitation of SP hollow crystals using static mixing. The SMV DN25 static mixers were supplied by Sulzer Chemtech, Switzerland. The size of each mixing element is 25 mm. One segment is composed of six elements, which are welded together



by being offset at 90°. The static mixing precipitation process of SP is illustrated in Figure 2. SP was dissolved in ethanol at a concentration of 10mg/ml to obtain the drug solution, and antisolvent was achieved by dissolving Tween80 or PVP in deionized water at 0.1 mg/ml. The flow rate ratio of drug solution to antisolvent was kept constant at 1:5. Some basic process parameters were: (1) the flow rates of the drug solution stream and the water stream were 20 and 100 mL/min, respectively, (2) the number of the mixing elements was 6, i.e. 1 segment, and (3) the diameters ddrug and dwater of the inlet tubing were 0.6 and 1.2 mm for the drug solution and water, respectively. In brief, the drug solution and water were pumped into static mixers in parallel to induce immediate precipitation by a Chemyx Fusion 200 syringe pump and an Ismatec VC-380 peristaltic pump, respectively. After reaching equilibrium for 30 s, approximately 60 ml of drug suspension was collected in a beaker and maintained at ambient temperature with stirring at certain times. A portion of such suspension was freeze dried or spray dried to produce a dry powder. For freeze drying, clay was used as the dispersant due to its high specific area and ion exchange/adsorption capability

46.

300 mg of clay was mixed with 60 ml of drug suspension for 10 s to ensure full

dispersion, and then flash frozen in liquid nitrogen and freeze dried (Virtis ES model bench top 2000, US) under vacuum for 3 days. For spray drying, clay was in absence of the formulation as carrier-free dry powder inhaler (DPI) was designed. Without clay, tween80 precipitated out during spray drying would attached on the surface of SP particles, enhancing the agglomeration between SP particles via particle-particle adhesion. Therefore, only PVP was used as stabilizer in spray drying. During drying process, a portion of drug suspension was directly fed into the spray dryer (Büchi Mini Spary dryer B-290 with inlet loop B-295, Germany) at a feeding rate of 3.5 ml/min via a peristaltic pump. The inlet temperature was kept at 130 ℃ and the aspirator was at 100%. Particle size and morphology 6 ACS Paragon Plus Environment

Page 6 of 31

Page 7 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


A field emission scanning electron microscope (FESEM, JEOL JSM-6700F) was used to analyze particle size and morphology. For the characterization of freshly precipitated particles in suspensions, droplets collected from suspensions at different times were deposited onto copper grids, and the droplets were instantly dried using filter paper to avoid any change in size and morphology during the drying process. For dried powders, the samples were directly deposited onto copper tapes. The samples were sputter coated with gold for 120 s at 20 mA, and the scanning was performed at 5.0 kV. Brunauer-Emmett-Teller (BET) analysis Specific surface area of spray dried SP and raw SP was determined via the nitrogen gas adsorption BET multipoint method, with five points in the relative pressure range of 0.05-0.25 (P/P0). Surface Area Analyzer Instrument (Micromeritics ASAP 2420N, USA) was used for the BET analysis. Powder samples were degassed for 24 h at 25 °C before analysis. Each measurement was repeated in triplicate based on separated sample preparation. Powder X-ray diffraction (PXRD) A D8-ADVANCE powder X-ray diffractometer (Bruker AXS GmbH, Germany) with 30 kV voltage and 40 mA current was used to obtain the PRXD patterns. The scan range was from 5 to 50° (2θ) at a scan rate of 2°/min. Differential scanning calorimetry (DSC) The physical state of raw materials, lyophilized formulation and spray dried formulation was analyzed by a Diamond DSC Calorimeter (PerkinElmer). The samples were equilibrated at 25 ºC for 10 min and then heated to 250 ⁰C at 10 ⁰C /min in a N2 atmosphere.



Dissolution measurement Dissolution measurements of freeze dried raw drug and freeze dried hollow drug were carried out using the USP type II (paddle) dissolution tester (VK 7010, VARIAN). 1000 ml of 0.1 M HCl containing 0.1% SDS was used as the dissolution medium, which was maintained at 37 ℃ during studies and the rotation speed of paddle was 100 rpm. At 2.5, 5, 10, 20, 30, 45, and 60 min, 1 ml aliquot of the dissolution medium was taken out, filtered (pore size: 0.22 µm) and directly injected to the HPLC system (Agilent 1100) for drug concentration analysis. The column used was an Agilent Eclipse XDB-C18 column (5 µm, 4.6 mm × 250 mm) and the mobile phase was a mixture of 70% (v/v) of acetonitrile and 30% (v/v) of water delivered at a flow rate of 1.5ml/min. The drug was detected at wavelength of 238 nm and retention time was 1.5 min. The experiment was conducted in triplicate. In vitro aerosol performance The aerosol performance of raw SP and spray dried SP powders was investigated by a multi-stage liquid impinger (MSLI, Copley Scientific, Nottingham, UK) coupled with a USP stainless steel throat 47. 20 ml of deionized water was introduced across all the four stages of the MSLI. Precisely weighed 20 mg of drug powder was filled into a hydroxypropyl methylcellulose (HPMC) capsule (size 3, Capsugel®, New Jersey, USA) and loaded into an Aerolizer® inhaler (Novartis Pharmaceuticals, Basel Switzerland)

48.

The capsule was then pierced and the powder was

dispersed for 4 s at an air flow rate of 60 l/min. After dispersion, the device, capsule, throat and all four stages of the MSLI were washed using deionized water separately. The washed solution was then transferred to the UV spectrophotometer (Agilent Technologies Cary 50 Conc, California,USA) for concentration measurement. The wavelength for SP detection is 238 nm. In


Page 8 of 31

Page 9 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


this study, fine particle fraction (FPF) denotes the mass fraction of drug particles smaller than 5 µm in the aerosol cloud relative to the total mass recovered and was obtained by interpolation to the cumulative percent undersize at 5 µm. Emitted FPF was obtained when the fine particle dose was expressed relative to the emitted dose. At a flow rate of 60 L/min, the aerodynamic cut-off diameters of stages 1, 2, 3 and 4 are 13.0, 6.8, 3.1 and 1.7 µm, respectively. Results and discussion Formation of hollow crystals monitored by SEM The formation of hollow crystals was monitored by SEM, and their particle size and hollow diameter were observed at different times. SEM images of SP precipitated in the presence of Tween80 (SP-TW) are presented in Figure 3. At 10 s after precipitation (Figure 3a), rod like crystals with less fused surface were precipitated. These particles were elongated with 1-3 µm in width but varying length of 3-10 µm. At 30 s (Figure 3b), the width and length of the rod particles increased to 2-5 µm and 5-20 µm, respectively. The bigger rod particles (superstructures) were agglomerated by primary units while some of the primary units were still visible. The primary units were self-assembled by tail to tail, and the hollows formed on the head of each primary unit. Our previous work has postulated that hollow crystals are reproducibly formed by a diffusionlimited growth mechanism

25.

It can be observed that the un-agglomerated primary units were

around 5 µm in length and highly homogenous in size, which is similar to the size of primary unit embedded in the superstructures. Besides, the self-assembled growth is under the non-classical crystallization, indicating that the primary units with high anisotropy would spontaneously align to form crystals with similar morphologies 23. After 1 min of precipitation (Figure 3c), there was no apparent variation in particle size, all the particles were still in the range of 5-20 µm in length.



However, the holes were partly shrank by crystal growth. In 5 min after precipitation (Figure 3d), the hollowness in the crystals was much reduced. In the case of precipitation in the presence of PVP (SP-PVP), all the primary units grew into hollow crystals without self-assembly, which was under diffusion-limited growth mechanism 4. At 10 s after precipitation (Figure 4a), some of the primary units have grown into bigger hollow crystals, while some of the smaller primary units (2-3 µm in length) were solid crystals. These solid primary units were the precursors for hollow crystals. At 30 s after precipitation (Figure 4b), most of the primary units grew into hollow crystals of varying length of 5-30 µm and the hollow diameter increased concomitantly. The size of these hollow crystals remained the same at 1 min after precipitation (Fig 4c), because the presence of PVP enhanced the nucleation rate and supersaturation was consumed rapidly to produce a large number of nuclei, resulting in limited crystal growth 49. At 5 min after precipitation (Figure 4d), no significant change in crystal size and hollow diameter size was observed, but the surface of crystals became highly fused. Particle morphology, size and specific surface area characterization of dry powder The typical morphologies of raw SP are presented in Figure 5 (a), which are cuboidal crystals with smooth surface, the particle size is in the range of 1-10 µm. Freeze dried raw SP formulation (FD raw SP, Figure 5b) retained the original morphology of raw SP. Images of freeze dried SP-tween80 with clay (FD SP-TW), freeze dried SP-PVP with clay (FD SP-PVP), and spray dried SP (SD SP) are shown in Figure5 (c), 5 (d) and 5 (e), respectively. Both the freeze dried and spray dried SP exhibit similar morphology and particle size, which maintained the appearance after fresh precipitation shown in Figure 3 and 4.


Page 10 of 31

Page 11 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Because of the elongated shape, light scattering technique for particle size measurement is unsuitable for this study. Alternatively, size of single particles was measured by SEM and the maximum length of particles was defined as the particle size. 100 particles taken from different areas of the samples were considered to determine the mean size of dry powders shown in Table 1. It can be seen that raw SP powder has the smallest particle size. Compared to the FD SP-PVP, FD SP-TW possessed a smaller particle size because part of the primary units failed to form superstructures. Furthermore, hydrogen bonding between SP and tween80 provided a strong inhibition on crystal growth. For SD SP, a small amount of SP crystals were crushed during drying process, which led to a slight reduction in size. Specific surface area of raw SP and SD SP is presented in Table 2. As can be seen, the specific surface area of SD SP was much improved compared to the raw SP powder. Furthermore, the deviation of the three measurements was relatively low. In comparison, agglomeration among particles led a poor specific surface area result of raw SP with a high deviation. Powder X-ray diffraction (PXRD) PXRD was used to identify the crystal form of the raw materials, freeze dried and spray dried formulations (Figure 6). Raw SP consisted of both SP form I and form II as its PXRD pattern contains all the major characteristic peaks of SP form I and form II calculated from single crystal X-ray diffraction data (form I, CSD refcode ATPRCL10 50; form II, CSD refcode ATPRCL01 51). The FD raw SP exhibited the same crystal form of raw SP. However, the FD SP-TW and FD SPPVP presented the distinct peaks of SP hydrate (CSD refcode WUWROW 44), indicating crystal form transformation occurred during antisolvent precipitation 25, 52. For SD SP formulation, both



characteristic peaks of hydrate and anhydrate forms of SP were obtained, demonstrating partial transformation of SP hydrate transformed to anhydrate during spray drying. Differential scanning calorimetry (DSC) Themograms of raw SP, raw clay, together with freeze dried and spray dried formulations in temperature range of 30-250 ℃ are presented in Figure 7. As can be seen, raw SP exhibited a melting peak at 208.5 ℃ and an enthalpy of 53.5 J/g. For raw clay, no specific melting peak was observed. A big hump covered the whole temperature range, which comes from the evaporation of immobilized water content in clay crystals. For the FD raw SP formulation, the melting peak was similar to the raw SP at 208.3 ℃ with the enthalpy slightly decreased to 37.6 J/g. In contrast, the melting peaks of FD SP-TW, FD SP-PVP and SD SP formulation shifted to 205.5, 201.5, and 191.3 ℃, respectively, and the enthalpy was decreased to 19.4, 19.1 and 22.1 J/g, respectively, due to a decrease in crystallinity after precipitation. However, partially crystalline formulation was found to be significantly more stable than amorphous formulation during storage in previous research 53. Dissolution Figure 8 displays the dissolution profiles of FD raw SP formulation, FD SP-TW formulation, and FD SP-PVP formulation within 60 min. It can be seen that 25.2±2.0% of FD raw SP dissolved within 2.5 min. After that, a total of 72.4±3.9% of drug was dissolved within 60 min. In comparison, FD SP-TW formulation exhibited a burst dissolution of 66.1±1.8% within the first 2.5 min, followed by a relatively slower dissolution and 88.2±1.1% of SP was dissolved within 60 min in total. This higher dissolution of FD SP-TW formulation could be ascribed to the enlarged surface area from hollow crystals. FD SP-PVP formulation exhibited an even higher dissolution rate. 12 ACS Paragon Plus Environment

Page 12 of 31

Page 13 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


78.0±2.1% of SP was dissolved in the first 2.5 min, which is more than 3 times of amount dissolution compared to the FD raw SP, and totally 95.3±2.0% of SP was dissolved in 60 min. The higher dissolution rate could be attributed to the higher degree of hollowness compared to the FD SP-TW as crystals with larger hollow openings were obtained from precipitation in the presence of PVP over tween80, which is evident in Figure 3. Storage stability To investigate the storage stability of hollow crystals, FD SP-PVP was stored in capped bottles for 6 months at ambient condition, and their dissolution rate was compared with the fresh formulation. It can be seen from Figure 9, the dissolution rate of FD SP-PVP had no significant difference compared to the fresh formulation after 6 months’ storage, demonstrating a good storage stability of hollow crystals. The dissolution rate of formulation after 6 months’ storage decreased around 5% only, and the overall dissolution within 60 min was still over 90%. In vitro aerosol performance Large particles (> 5µm) possessing low mass density can be successfully inspired into the lungs 54.

In addition, large particles (~10 µm) aggregate less than smaller particles 55. Therefore, hollow

particles is an efficient aerosolization approach for inhalation delivery. In previous research

15,

hollow particles were mainly obtained from spray drying, but in amorphous form. In this study, antisolvent precipitation is ideal for generating particles that are both crystalline and hollow. Moreover, the precipitated hollow crystals were dispersed during atomization in spray dryer whereas dispersant is required for freeze drying. Because the dispersant ‘clay’ is not suitable for aerosol, spray drying was cooperated with antisolvent precipitation to produce dry powder of hollow crystals. The in vitro aerosolization performance results of raw SP and SD SP are illustrated



in Figure 10. Substantial retention in device, throat and stage 1 indicate the highly cohesive nature of the raw drug, and hence the raw drug exhibited a very low FPF and emitted FPF of 7.8±0.8% and 10.5±1.2%, respectively. In comparison, SD SP showed a much improved FPF and emitted FPF of 23.1±0.4% and 33.9±1.0%, respectively, corresponding to a decreased retention in throat, stage 1 and stage 2 along with a subsequent increase in stage 3, 4 and filter in the MSLI. This is attributed to the lower density of the crystals due to hollow formation even though the particle size of the SD SP is larger than that of the raw drug Moreover, the hollow crystals with a high aspect ratio would also reduce the aerodynamic diameter that aids in the deposition deeper into the lung 17, 56.

Mechanism for the improved aerosolization performance was due mainly to efficiencies in

gravitational settling and interception brought about by the hollow (and hence low density) and elongated crystals (i.e. aerodynamic behavior is size, shape and density-dependent) 57. However, the smooth surfaces of hollow crystals could increase the adhesion between crystals subsequently reduce deaggregation during release through the nozzle, leading to a large amount of deposition of SD SP in the inhaler device. Nevertheless, this could be easily rectified via the introduction of suitable anti-adherents to the device and/or the formulation 48. Conclusions A continuous and scalable process was conducted to produce hollow spironolactone crystals, and formulate them into powder form which is suitable for oral and pulmonary administration. In this process, hollow spironolactone was continuously precipitated in the presence of tween80 or PVP, and then immediately dried to maintain particle morphology. The evolution of hollow crystals was observed by SEM, indicating both tween80 and PVP induce hollow formation during crystallization, but under different growth mechanism. In the presence of tween80, holes formation was attributed to the combination of diffusion-limited growth and particle self-assembly, while 14 ACS Paragon Plus Environment

Page 14 of 31

Page 15 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


only diffusion-limited growth led to the hollow formation in the presence of PVP. According to PXRD and DSC results, hollow SP crystals remained predominantly in crystalline state. Dissolution test showed that hollow crystals achieved significantly higher drug dissolution rates at 66.1±1.8% and 78.0±2.1% within 2.5 min in the presence of tween80 and PVP, respectively. In contrast, only 25.2±2.0% of raw drug formulation was dissolved in the first 2.5 min. Moreover, the in vitro aerosolization performance test showed a much improved FPF at 23.1±0.4% comparing to the raw drug of 7.8±0.8%, demonstrating the potential application of hollow crystals in aerosol development.

*Corresponding author: E-mail address: [email protected] (F. Sheng) E-mail address: [email protected] (R.B.H. Tan)

Acknowledgments This work was supported by project grant SC22/17-1A0220-0000 from A*STAR (Agency for Science, Technology, and Research) of Singapore.



Reference 1. Dette, S. S.; Stelzer, T.; Römbach, E.; Jones, M. J.; Ulrich, J., Controlling the Internal Diameter of Nanotubes by Changing the Concentration of the Antisolvent. Crystal Growth & Design 2007, 7, 16151617. 2. Schuster, A.; Stelzer, T.; Ulrich, J., Generation of Crystalline Hollow Needles: New Approach by Liquid-Liquid Phase Transformation. Chemical Engineering & Technology 2011, 34, 599-603. 3. Martins, D.; Stelzer, T.; Ulrich, J.; Coquerel, G., Formation of Crystalline Hollow Whiskers as Relics of Organic Dissipative Structures. Crystal Growth & Design 2011, 11, 3020-3026. 4. Eddleston, M. D.; Jones, W., Formation of Tubular Crystals of Pharmaceutical Compounds. Crystal Growth & Design 2010, 10, 365-370. 5. Kesisoglou, F.; Panmai, S.; Wu, Y., Nanosizing—oral formulation development and biopharmaceutical evaluation. Advanced Drug Delivery Reviews 2007, 59, 631-644. 6. Parikh, D. M., Handbook of pharmaceutical granulation technology. CRC Press: 2016. 7. Chiou, H.; Li, L.; Hu, T.; Chan, H.-K.; Chen, J.-F.; Yun, J., Production of salbutamol sulfate for inhalation by high-gravity controlled antisolvent precipitation. International Journal of Pharmaceutics 2007, 331, 93-98. 8. Modi, S. R.; Dantuluri, A. K. R.; Puri, V.; Pawar, Y. B.; Nandekar, P.; Sangamwar, A. T.; Perumalla, S. R.; Sun, C. C.; Bansal, A. K., Impact of Crystal Habit on Biopharmaceutical Performance of Celecoxib. Crystal Growth & Design 2013, 13, 2824-2832. 9. Blagden, N.; de Matas, M.; Gavan, P. T.; York, P., Crystal engineering of active pharmaceutical ingredients to improve solubility and dissolution rates. Advanced Drug Delivery Reviews 2007, 59, 617630. 10. Gonda, I., The ascent of pulmonary drug delivery. Journal of Pharmaceutical Sciences 2000, 89, 940-945. 11. Vehring, R., Pharmaceutical particle engineering via spray drying. Pharmaceutical Research 2008, 25, 999-1022. 12. Heng, D.; Tang, P.; Cairney, J. M.; Chan, H.-K.; Cutler, D. J.; Salama, R.; Yun, J., Focused-ion-beam milling: a novel approach to probing the interior of particles used for inhalation aerosols. Pharmaceutical Research 2007, 24, 1608-1617. 13. Hadinoto, K.; Phanapavudhikul, P.; Kewu, Z.; Tan, R. B. H., Novel Formulation of Large Hollow Nanoparticles Aggregates as Potential Carriers in Inhaled Delivery of Nanoparticulate Drugs. Industrial & Engineering Chemistry Research 2006, 45, 3697-3706. 14. Vanbever, R.; Mintzes, J. D.; Wang, J.; Nice, J.; Chen, D.; Batycky, R.; Langer, R.; Edwards, D. A., Formulation and physical characterization of large porous particles for inhalation. Pharmaceutical Research 1999, 16, 1735-1742. 15. Elversson, J.; Millqvist-Fureby, A., Particle size and density in spray drying—effects of carbohydrate properties. Journal of Pharmaceutical Sciences 2005, 94, 2049-2060. 16. Hu, T.; Chiou, H.; Chan, H. K.; Chen, J. F.; Yun, J., Preparation of inhalable salbutamol sulphate using reactive high gravity controlled precipitation. Journal of Pharmaceutical Sciences 2008, 97, 944-949. 17. Yazdi, A. K.; Smyth, H. D. C., Hollow crystalline straws of diclofenac for high-dose and carrier-free dry powder inhaler formulations. International Journal of Pharmaceutics 2016, 502, 170-180. 18. Horn, D.; Rieger, J., Organic nanoparticles in the aqueous phase—theory, experiment, and use. Angewandte Chemie, International Edition in English 2001, 40, 4330-4361. 19. Rogers, T. L.; Gillespie, I. B.; Hitt, J. E.; Fransen, K. L.; Crowl, C. A.; Tucker, C. J.; Kupperblatt, G. B.; Becker, J. N.; Wilson, D. L.; Todd, C., Development and characterization of a scalable controlled precipitation process to enhance the dissolution of poorly water-soluble drugs. Pharmaceutical Research 2004, 21, 2048-2057. 16 ACS Paragon Plus Environment

Page 16 of 31

Page 17 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


20. Matteucci, M. E.; Hotze, M. A.; Johnston, K. P.; Williams, R. O., Drug nanoparticles by antisolvent precipitation: mixing energy versus surfactant stabilization. Langmuir 2006, 22, 8951-8959. 21. Thorat, A. A.; Dalvi, S. V., Particle formation pathways and polymorphism of curcumin induced by ultrasound and additives during liquid antisolvent precipitation. CrystEngComm 2014, 16, 11102-11114. 22. Tierney, T. B.; Guo, Y.; Beloshapkin, S.; Rasmuson, Å. C.; Hudson, S. P., Investigation of the Particle Growth of Fenofibrate following Antisolvent Precipitation and Freeze–Drying. Crystal Growth & Design 2015, 15, 5213-5222. 23. Cölfen, H.; Mann, S., Higher-Order Organization by Mesoscale Self-Assembly and Transformation of Hybrid Nanostructures. Angewandte Chemie, International Edition in English 2003, 42, 2350-2365. 24. Liu, Y.; Kathan, K.; Saad, W.; Prud’homme, R. K., Ostwald Ripening of β-Carotene Nanoparticles. Physical Review Letters 2007, 98, 036102. 25. Sheng, F.; Chow, P. S.; Yuancai, D.; Tan, R. B. H., Polymer Templated Structural Evolution of a Poorly Water-Soluble Active Pharmaceutical Ingredient from Nanoparticles to Hierarchical Crystals. Crystal Growth & Design 2018, 18, 3089-3098. 26. Paulino, A.; Rauber, G.; Campos, C.; Maurício, M.; De Avillez, R.; Capobianco, G.; Cardoso, S.; Cuffini, S., Dissolution enhancement of deflazacort using hollow crystals prepared by antisolvent crystallization process. European Journal of Pharmaceutical Sciences 2013, 49, 294-301. 27. Mallet, F.; Petit, S.; Lafont, S.; Billot, P.; Lemarchand, D.; Coquerel, G., Crystal Growth Mechanism in a Solution of Hollow Whiskers of Molecular Compounds. Crystal Growth & Design 2004, 4, 965-969. 28. Bhargavi, N.; Chavan, R. B.; Shastri, N. R., Generation of Hollow Crystals of a Drug with Lamellar Structure Forming Ability. Crystal Growth & Design 2017, 17, 1480-1483. 29. Viswanatha, R.; Sarma, D. D., Growth of Nanocrystals in Solution. In Nanomaterials Chemistry, Wiley-VCH Verlag GmbH & Co. KGaA: 2007; pp 139-170. 30. Iwanaga, H.; Shibata, N., Growth mechanism of hollow ZnO crystals from ZnSe. Journal of Crystal Growth 1974, 24 (Supplement C), 357-361. 31. Johnson, B. K.; Prud’homme, R. K., Mechanism for Rapid Self-Assembly of Block Copolymer Nanoparticles. Physical Review Letters 2003, 91, 118302. 32. Liu, W. J.; Ma, C. Y.; Liu, J. J.; Zhang, Y.; Wang, X. Z., Analytical technology aided optimization and scale-up of impinging jet mixer for reactive crystallization process. AIChE Journal 2015, 61, 503-517. 33. Karnik, R.; Gu, F.; Basto, P.; Cannizzaro, C.; Dean, L.; Kyei-Manu, W.; Langer, R.; Farokhzad, O. C., Microfluidic Platform for Controlled Synthesis of Polymeric Nanoparticles. Nano Letters 2008, 8, 29062912. 34. Charcosset, C.; Fessi, H., Preparation of nanoparticles with a membrane contactor. Journal of Membrane Science 2005, 266, 115-120. 35. Galindo-Rodríguez, S. A.; Puel, F.; Briançon, S.; Allémann, E.; Doelker, E.; Fessi, H., Comparative scale-up of three methods for producing ibuprofen-loaded nanoparticles. European Journal of Pharmaceutical Sciences 2005, 25, 357-367. 36. Thakur, R.; Vial, C.; Nigam, K.; Nauman, E.; Djelveh, G., Static mixers in the process industries—a review. Chemical Engineering Research and Design 2003, 81, 787-826. 37. Dong, Y.; Ng, W. K.; Hu, J.; Shen, S.; Tan, R. B., A continuous and highly effective static mixing process for antisolvent precipitation of nanoparticles of poorly water-soluble drugs. International Journal of Pharmaceutics 2010, 386, 256-261. 38. Douroumis, D.; Fahr, A., Nano-and micro-particulate formulations of poorly water-soluble drugs by using a novel optimized technique. European Journal of Pharmaceutics and Biopharmaceutics 2006, 63, 173-175.



39. Douroumis, D.; Scheler, S.; Fahr, A., Using a modified shepards method for optimization of a nanoparticulate cyclosporine a formulation prepared by a static mixer technique. Journal of Pharmaceutical Sciences 2008, 97, 919-930. 40. Langguth, P.; Hanafy, A.; Frenzel, D.; Grenier, P.; Nhamias, A.; Ohlig, T.; Vergnault, G.; SpahnLangguth, H., Nanosuspension formulations for low-soluble drugs: pharmacokinetic evaluation using spironolactone as model compound. Drug Development and Industrial Pharmacy 2005, 31, 319-329. 41. Dong, Y.; Ng, W. K.; Shen, S.; Kim, S.; Tan, R. B. H., Preparation and characterization of spironolactone nanoparticles by antisolvent precipitation. International Journal of Pharmaceutics 2009, 375, 84-88. 42. Thommes, M.; Ely, D. R.; Carvajal, M. T.; Pinal, R., Improvement of the Dissolution Rate of Poorly Soluble Drugs by Solid Crystal Suspensions. Molecular Pharmaceutics 2011, 8, 727-735. 43. Yusuff, N.; York, P.; Chrystyn, H.; Bramley, P.; Swallow, R.; Tuladhar, B.; Losowsky, M., Improved bioavailability from a spironolactone beta-cyclodextrin complex. European Journal of Clinical Pharmacology 1991, 40, 507-511. 44. Takata, N.; Takano, R.; Uekusa, H.; Hayashi, Y.; Terada, K., A Spironolactone−Saccharin 1:1 Cocrystal Hemihydrate. Crystal Growth & Design 2010, 10, 2116-2122. 45. Every, N.; Hale, R.; Lu, A.; Rabinowitz, J., Diuretic aerosols and methods of making and using them. U.S. Patent Application No. 10/712,365.: 2004. 46. Dong, Y.; Ng, W. K.; Hu, J.; Shen, S.; Tan, R. B. H., Clay as a matrix former for spray drying of drug nanosuspensions. International Journal of Pharmaceutics 2014, 465, 83-89. 47. Lee, S. H.; Teo, J.; Heng, D.; Zhao, Y.; Ng, W. K.; Chan, H.-K.; Tan, L. T.; Tan, R. B. H., A novel inhaled multi-pronged attack against respiratory bacteria. European Journal of Pharmaceutical Sciences 2015, 70, 37-44. 48. Heng, D.; Lee, S. H.; Ng, W. K.; Chan, H.-K.; Kwek, J. W.; Tan, R. B. H., Novel alternatives to reduce powder retention in the dry powder inhaler during aerosolization. International Journal of Pharmaceutics 2013, 452, 194-200. 49. Chari, K.; Antalek, B.; Kowalczyk, J.; Eachus, R. S.; Chen, T., Polymer−Surfactant Interaction and Stability of Amorphous Colloidal Particles. Journal of Physical Chemistry B 1999, 103, 9867-9872. 50. Dideberg, O.; Dupont, L., La structure cristalline et moléculaire de la spironolactone (7αacétylthio-3-oxo-17α-4-pregnène-21, 17β carbolactone). Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry 1972, 28, 3014-3022. 51. Agafonov, V.; Legendre, B.; Rodier, N., A new crystalline modification of spironolactone. Acta Crystallographica Section C: Crystal Structure Communications 1989, 45, 1661-1663. 52. Salole, E. G.; Al-Sarraj, F. A., Spironolactone Crystal Forms. Drug Development and Industrial Pharmacy 1985, 11, 855-864. 53. Sanganwar, G. P.; Gupta, R. B., Dissolution-rate enhancement of fenofibrate by adsorption onto silica using supercritical carbon dioxide. International Journal of Pharmaceutics 2008, 360, 213-218. 54. Edwards, D. A.; Hanes, J.; Caponetti, G.; Hrkach, J.; Ben-Jebria, A.; Eskew, M. L.; Mintzes, J.; Deaver, D.; Lotan, N.; Langer, R., Large Porous Particles for Pulmonary Drug Delivery. Science 1997, 276, 18681872. 55. French, D. L.; Edwards, D. A.; Niven, R. W., The influence of formulation on emission, deaggregation and deposition of dry powders for inhalation. Journal of Aerosol Science 1996, 27, 769-783. 56. Ikegami, K.; Kawashima, Y.; Takeuchi, H.; Yamamoto, H.; Mimura, K.; Momose, D.-i.; Ouchi, K., A new agglomerated KSR-592 β-form crystal system for dry powder inhalation formulation to improve inhalation performance in vitro and in vivo. Journal of Controlled Release 2003, 88, 23-33. 57. Darquenne, C., Particle deposition in the lung. In Encyclopedia of Respiratory Medicine, Laurent, G. J.; Shapiro, S. D., Eds. Academic Press: Oxford, 2006; pp 300-304. 18 ACS Paragon Plus Environment

Page 18 of 31

Page 19 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Spironolactone

Tween80

Figure 1. Molecular structures of Spironolactone, Tween80 and PVP


PVP


Figure 2. Production of hollow crystals through static mixing


Page 20 of 31

Page 21 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b)

(c)

(d)

Figure 3. Evolution of SP hollow crystals formed in the presence of tween80 at (a) 10 s, (b) 30 s, (c) 1min, and (d) 5 min, respectively.



Page 22 of 31

(a)

(b)

(c)

(d)

Figure 4. Evolution of SP hollow crystals formed in the presence of PVP at (a) 10 s, (b) 30 s, (c) 1min, and (d) 5 min, respectively.


Page 23 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b)

(c)

(d)

(e) Figure 5. SEM images of (a) raw SP, (b) FD raw SP, (c) FD SP-TW, (d) FD SP-PVP, and (e) SD SP 23 ACS Paragon Plus Environment


Figure 6. PXRD patterns of (a) raw SP, (b) raw clay, (c) FD raw SP, (d) FD SP-TW, (e) FD SPPVP, (f) SD SP, (g) SP hydrate from database, (h) SP form I from database, and (i) SP form II from database


Page 24 of 31

Page 25 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 7. Thermograms of (a) raw SP, (b) raw clay, (c) FD raw SP, (d) FD SP-TW, (e) FD SPPVP, and (f) SD SP.



Figure 8. Dissolution profiles of (a) FD raw SP, (b) FD SP-TW, and (c) FD SP-PVP


Page 26 of 31

Page 27 of 31

100 90 80

% Dissolved

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


70 60 50

Formulation fresh

40

Formulation 6 months

30 20 10 0 0

5

10

15

20

25

30

35

40

45

50

55

Time min

Figure 9. Dissolution profile of FD SP-PVP (fresh) and FD SP-PVP (6 months)


60


raw SP

Spray dried SP

40 35 30

Deposition %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

25 20 15 10 5 0

Capsule Device Throat Stage 1 Stage 2 Stage 3 Stage 4 Filter FPF (%)Emitted FPF (%) (13 (6.8 (3.1 (1.7 (

Continuous and Scalable Process for the Production of Hollow

Recommend Documents