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Article

Crystallization of Small Molecules in Microgravity Using Pharmaceutical In-Space Laboratory–Biocrystal Optimization eXperiment (PIL-BOX)

by
Lillian Miller
1,
Molly K. Mulligan
2,
Kenneth A. Savin
2,
Stephen Tuma
2 and
Anne M. Wilson
1,*
1
Department of Chemistry and Biochemistry, Butler University, 4600 Sunset Avenue, Indianapolis, IN 46208, USA
2
Redwire, 7200 US-150, Greenville, IN 47124, USA
*
Author to whom correspondence should be addressed.
Crystals 2025, 15(6), 527; https://doi.org/10.3390/cryst15060527
Submission received: 12 May 2025 / Revised: 22 May 2025 / Accepted: 23 May 2025 / Published: 30 May 2025
(This article belongs to the Section Organic Crystalline Materials)
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Abstract

:
Crystallization in microgravity has measurable benefits, from molecules as simple as sodium chloride to elaborate protein complexes. However, small organic molecules have not been reported. The small organic molecules glycine, famoxadone, carbamazepine, and 5-methyl-2-((2-nitrophenyl)amino)thiophene-3-carbonitrile (ROY) were crystallized on Earth under microgravity conditions. When comparing these different gravity crystallization conditions, we found the formation of different polymorphs and/or habits for glycine, carbamazepine, and ROY. The crystallization of famoxadone occurred more slowly in microgravity. The differences in size, appearance, and, in the case of ROY, color, are detailed in this report.

1. Introduction

Crystallization is a basic laboratory technique often taught in chemistry courses. It is a critical component of industrial processes to provide pure compounds as specialty chemicals or intermediates and products in the pharmaceutical industry [1] (p. xxii). The control of crystallization methods can result in products with a precise crystal size, a uniform crystal shape, specific polymorphs, fewer inclusions, fewer impurities, and a lesser degree of agglomeration [1] (p. 22). A variety of hardware systems, including evaporative crystallizers [1] (pp. 51–70), batch crystallizers [1] (pp. 210–233), and techniques like solvent/antisolvent crystallization [1] (pp. 234–261) and melt crystallization [1] (pp. 261–283), have been developed to grow crystals, depending on the application.
Despite the widespread use of crystallization, the process(es) by which polymorphs interconvert are still being studied. The two prevailing theories are Ostwald’s Rule of Stages [2] and classical nucleation theory [3] (which now includes cross-nucleation [4,5]), and the investigation of these two theories continues [6]. There are tools available to observe early stages of nucleation and crystallization, especially Raman spectroscopy [7,8]. A more complete understanding of the crystallization process, especially in regard to polymorph formation, would inform modeling processes and the prediction of optimal pharmaceutical processes [9].
Microgravity is an excellent tool for making crystals that are larger, more uniform, and with an improved structure [10]. However, at the time of the preparation of this manuscript, only the following four small organic molecules (molecular weights below 750 amu) have been reported to have been crystallized in a microgravity environment: triglycine sulfate from a solution [11,12,13], L-arginine phosphate dihydrate from a solution [14], and TTF-TCNQ from a solution [15]. There is also a preliminary report of crystallization of ritonavir by melt recrystallization [16]. Given the dearth of published small-molecule crystallization in microgravity research, this is an area ripe for exploration that could also provide insights into the driving forces of the early stages of nucleation and crystallization.
Several factors are believed to contribute to improvements in crystal growth in microgravity, including reduced convection near growing crystal surfaces [17,18] and diffusion-limiting kinetics slowing crystal growth [19]. Microgravity can also offer the opportunity for metastable polymorphs of crystals to be formed [16], which could offer the opportunity for improved drug delivery [20,21]. To evaluate microgravity as a tool for small-molecule crystal growth, glycine, famoxadone, carbamazepine, and 5-methyl-2-((2-nitrophenyl)-amino)-thiophene-3-carbonitrile (ROY) were chosen for our initial studies (Figure 1).
Glycine is the simplest amino acid known to crystallize in four different polymorphs [22]. Famoxadone is a fungicide known to exist in six different polymorphic forms [23]. Carbamazepine is an anticonvulsant that has four polymorphs [24]. ROY is a colored compound that has at least fourteen known polymorphs, of which eight have been at least partially characterized [25,26,27]. The diversity of the polymorphic forms of each of these compounds allows for the study of the impact of microgravity on the crystallization of a diversity of small organic molecules.

2. Materials and Methods

Initial ground experiments were conducted in round-bottomed flasks with saturated solutions of analyte in the solvent (see Table 1), and an antisolvent was added dropwise to obtain crystalline compounds. Ground experiments were repeated using the hardware described below. During these tests, it was found that the saturated solutions (with the exception of glycine) were too concentrated to provide visualization through the chambers. In almost all cases, the analyte concentrations were reduced to the concentrations described in Table 1. Famoxadone was reduced from 80 mg/mL to 11 mg/mL, carbamazepine was reduced from 200 mg/mL to approximately 13 mg/mL, and ROY was reduced from 60 mg/mL to approximately 11 mg/mL. These ground experiments were performed three times each at the new concentrations. These conditions were the conditions utilized for the official ground controls (4X each) and flight (4X each).
The hardware used to perform this experiment was unique as it was made to operate in the microgravity environment on the International Space Station (ISS). The ADvanced Space Experiment Processor (ADSEP) (Figure 2A) is on the International Space Station (ISS) and operates cassettes (Figure 2B), which are routinely flown to and from the ISS via the National Aeronautics and Space Administration (NASA)’s Commercial Resupply (CRS) missions currently flown by SpaceX and Northop Grumman. To perform this experiment, the Pharmaceutical In-space Laboratory (PIL)–Biocrystal Optimization eXperiment (BOX) cassette was flown to the ISS on a CRS mission to perform crystallization experiments. There are three types of PIL-BOXes and, in the case of small-molecule crystallization, the PIL-BOX Small Molecule Accelerated Laboratory for Structure (SMALS) (Figure 2B) is flown to the ISS to perform experiments. Inside the PIL-BOX SMALS are four fluid loops (Figure 2C), which each contain two syringes (syringe A and syringe B) that are loaded with fluid and then, once on the ISS, those syringes inject the fluids into the experiment chamber. The injection process and the crystallization process are then observed via a microscope and recorded via video and images at regular intervals. This ensures that the crystals formed in microgravity are the ones that are present when the PIL-BOX SMALS returns to Earth and allows the scientists to watch the process of crystallization in microgravity. The PIL-BOX SMALS can also be operated on the ground inside a ground-based ADSEP, which allows for ground controls of the experiments.
Solutions were prepared for each of the compounds as listed in Table 1. These solutions were loaded into syringe A of each of the four fluid loops for each of the four experiments (Figure 2C). The antisolvent (0.4 mL; Table 1) for each experiment was loaded into syringe B (Figure 2C). The fluid loops were loaded into the PIL-BOX SMALS cassettes and prepared for launch as per NASA protocols at ambient temperatures (between 18 and 26 °C). Once on the ISS, the PIL-BOXes (Figure 2B), were removed from the packaging and inserted into the ADSEP facility (Figure 2A). Operations on the ISS were then initiated. The two solutions (the material to be crystalized in the solvent and the antisolvent in syringes A and B, respectively) were simultaneously injected into the crystallization/observation chamber. The two solutions combined within a manifold and shared a single tube to flow into the reaction chamber in microgravity and were observed by video (Figure 2B). The total volume of the crystallization/observation chamber was 0.3 mL, and excess volumes of liquid and gas (the tubing and crystallization/observation chamber were not primed leading up to the initiation of on-orbit operations) were allowed to run into an overflow syringe. A schematic of the fluid loop can be seen in Figure 2D. The materials in the overflow syringe were also collected and evaluated. Terrestrial studies and the space-grown studies were executed in the same manner using the same setups to ensure the best gravity-to-microgravity comparisons.
In flight, the PIL-BOXes were loaded into the ADSEP facility (Figure 2A) by an astronaut on the ISS. The injections took place over approximately three minutes at a temperature setpoint of 22 °C and remained at that temperature for the duration of the crystallization process. In most cases, crystallization was immediately observed in the crystallization chamber and likely began immediately upon contact between the two solutions. The PIL-BOXes were processed (with the crystals in the crystallization solution) for two days. The crystallizations were observed and images were taken every 15 min up to the point where the PIL-BOXes were removed from the ADSEP facility. The PIL-BOXes were then packaged and held on station for approximately two additional weeks before being deorbited and brought to a facility for initial return observations. During that time, the crystals were suspended in the crystallization solvent mixture. Upon return to Earth, the PIL-BOXes were sent to the laboratory to have the chambers opened and the crystals harvested and evaluated. The microgravity crystals were compared with those grown under the same conditions terrestrially. Visualization was performed using a Leica S9D stereo microscope (Liece Mikrosyteme Vertrieb GmbH, Wetzlar, Germany) equipped with Enersight software (Flexcam_C3, v. 3.01a) at 0–5× magnification as well as the 10× and 20× objectives of the BWTek BAC151C Raman microscope (BWTek a division of Metrohm, Plainsboro, NJ, USA) attachment to the iRamanPlus fiber optic Raman system (BWTek a division of Metrohm, Plainsboro, NJ, USA).

3. Results

Although every effort was made to ensure that the crystallization conditions were the same for both ground and flight, there was no way to measure the final concentrations of the solutions pre- and post-experiment. There were occasions for both ground and flight experiments where the solutions ran around the edges of the crystallizing cell and directly into the waste syringe. In addition, some chambers had air bubbles of differing sizes. These differences may have impacted some of the results. However, the overall study suggests that the differences observed between the ground and flight crystallizations were valid.

3.1. Glycine

Crystallization experiments on the ground demonstrated that crystals grew on the sides of the glass and on the edges of the chamber as both rods and blocks (Figure 3). Crystals appeared within five minutes and continued to grow for approximately thirty minutes. The final crystals varied in size, with the largest measuring up to 0.40 mm.
Under microgravity conditions, spindles were observed in three of the reaction chambers (Figure 4A–C). Upon return to Earth, the spindles had vanished and the crystals observed (by Raman) were very uniform crystals of α-glycine (Figure 5). This is a known transition [28]. Glycine is known to exist in three forms (α, β, and γ). These are also known by their habits, which are well-defined and can be visually differentiated in some cases. One form is less common (spindles) but we observed all three often as mixtures in the different runs. It is believed that the most thermodynamically stable crystalline form is the fate of crystals grown in microgravity under equilibrium conditions [11,12,13]. However, the initial formation of the β-form of glycine in some runs—perhaps as much as ¾ of the β-form, from a cursory evaluation of the microscopic images taken on station—was a surprise. We would have missed this without on-orbit image capture. This result led us to re-evaluate our thinking around the expected outcomes of the work undertaken in space relative to terrestrial results because a kinetic crystal could be the dominant result (more quiescent conditions may not exclusively lead to a more thermodynamically stable form) as the kinetic form may not only be the fastest to form but also the first and only crystals.
Depending upon conditions, some models predict that γ-glycine is the most stable of the polymorphs [28], whereas others suggest that α-glycine is the most stable polymorph [29], with each of these forms being very close in energy. The β-form is less stable and known to transition to both α- and γ-glycine.

3.2. Famoxadone

Ground experiments on the growth of famoxadone crystals resulted in spherulitic crystals (Figure 6). These compact structures clumped together and often formed at the edges of the chambers. The crystals grew within five minutes of fluid injection and mixing within the reaction chamber.
In space, the crystals appeared to grow from a central point and then fill in around the central point (Figure 7). They were very fine dendritic structures, whereas on Earth they tended to be more compact and spherical. There is a debate in the literature as to the impact of gravity on atomic mobility in liquids, with some researchers suggesting that diffusion is unchanged [30] and others suggesting it is slower in microgravity [31]. The progression of crystal growth for famoxadone could have captured the process for the spherulite formation of these crystals, starting from the dendritic structures in the middle of the solution (Figure 7A), to more delicate structures forming in the center of the dendrites (Figure 7B), to the final spherulites collected on Earth (Figure 8), perhaps providing evidence that diffusion-based crystal growth is slower in microgravity. This is reasonable as the limiting factor could be access to material in a solution. The fastest access to materials is at the edges and corners, leading to longer needles as the crystal grows to where the crystal-growing nutrients are. As these different morphologies are in the same chamber at different depths, this could also represent inhomogeneity in the solution.

3.3. Carbamazepine

Ground-based carbamazepine growth provided carbamazepine-I (by Raman) needles that were 0.07 mm at the widest point and 1.3 mm from end to end (Figure 9). These needles grew from the sides, window, and into the center of the chamber.
All growth in microgravity provided needles of carbamazepine-III (by Raman) (Figure 10). These crystals were also wider (0.20 mm at the widest point) and longer (1.5 mm end to end) than the ground comparisons. A cursory evaluation generated from the carbamazepine studies using the 10× power microscope built into the hardware showed that the crystals had sharper points and clean lines relative the ground-based examples. The crystals grew into the middle of the chamber and not at the edges or bottom of the reaction chamber. The different forms were visually indistinguishable and required identification via Raman spectroscopy.

3.4. ROY

ROY was generally more difficult to handle than the other compounds [32]. The material was sticky, and greater care had to be taken during loading to ensure fittings were secure before the experiments were executed. The different forms displayed not only different colors but different morphologies that were visually observable. The different structures were generally not cleanly separated from each other from sample to sample but could be easily seen and identified within the different samples. On the ground, ROY produced orange needles and yellow plates (Figure 11).
In flight, visualizing the ROY solutions was challenging due to air bubbles and a darkly colored solution, which made seeing into the chambers difficult (Figure 12). From the limited images, yellow irregular crystals appeared to be the major structures in space. When harvested on the ground, the flight crystals presented as yellow prisms (Figure 13A) as well as orange–red prisms (Figure 13B) when observed.

4. Discussion

For each of the crystallization experiments, an unexpected result was observed. Given the paucity of space-grown small-molecule examples reported in the literature, this was not unanticipated but it was still remarkable.
Glycine demonstrated polymorph interconversion in microgravity. Transitions from γ- to α-glycine are well-known and have been studied [28], and there are reports of β-glycine converting to α- and γ-glycine [29]. We observed all three crystal forms in space but, upon return to the ground, we observed no β-glycine. The preponderance of the initial β-glycine formation in microgravity was unexpected but is known to occur in situations of super-saturation. The α-glycine crystals that were isolated were uniform in size and had nice edges and clear faces. The video observation that β-glycine was initially formed in three of the four chambers implied that this metastable form of glycine could be isolated if the solvent was removed and replaced with dry atmosphere [9,33,34,35,36]. Solution enthalpy measurements of glycine polymorphs have shown that γ-glycine is most stable at room temperature [28]. Our study demonstrated that a mix of α- and γ-glycine represented the final polymorphs formed after interconversion in a microgravity environment. Presumably, the thermodynamic product was formed under equilibrium microgravity conditions, which is in line with theoretical models [29]. This led us to believe that we were not at equilibrium or that the transition that would lead to the thermodynamically most stable form was not possible under the conditions or in the time frame of the experiment.
To isolate metastable β-glycine, the solvent could be removed from the chamber upon initial crystallization. This polymorph has been shown to be stable in dry air [20]. In addition, a more consistent formation of crystal forms could be achieved by using pre-filled chambers rather than empty chambers to both avoid bubbles and create consistent mixing between the different reaction chambers in the series.
In the case of famoxadone crystal growth, dendritic structures grew to form spherulites. Dendrites are one of the favored structures when the heat of crystallization is dispersed from the edges and corners of the crystal [37]. Without gravity, these fragile structures are far more spherical and have excellent definition along the outer edges of the spheres. Remarkably, they also survived landing and transport on the ground.
Carbamazepine has at least four different polymorphs with stabilities that are within 0.7 kcal/mol in energy in terms of their thermal behavior and conversion to the lowest energy form, I [38]. Both of the forms that we observed were needles, consistent with the other form of favored structure when the heat of crystallization is dispersed from the edges and corners of the crystal [37]. Form III is the most stable form of carbamazepine at room temperature [39]. In this case, the most stable form was generated under microgravity conditions. In addition, the very fragile, long needles also survived landing and transport on the ground.
The microgravity crystallization of ROY provided different polymorphs than those we produced in our ground studies. With at least fourteen known polymorphs, the lowest energy polymorph is reputed to be amorphous yellow crystals (form Y) at room temperature [40]. Our ground studies produced yellow plates (form YN) and orange needles (form ON), which is consistent with the literature [40]. In microgravity, the forms that were produced were yellow prisms (form Y) and orange–red prisms (form ORP). From the video evidence, it appeared that Y and R crystals were initially formed and not converted from other forms, as seen with glycine.
In all four experiments, there were challenges with the solvents wicking around the sides of the chamber, resulting in an incomplete fill and large bubbles in the chamber. This could be alleviated in future experiments by having the chamber pre-filled with one of the solutions. Given the interconversion of glycine from one polymorph to another in a solution, it would also be helpful for future experiments to have the option of removing the solvent upon crystallization. In this way, kinetic and/or metastable crystals could be pre-isolated while still under a microgravity environment.

5. Conclusions

Compared with the ground counterparts, small organic molecules (glycine, famoxadone, carbamazepine, and ROY) behaved differently when crystallized in space. Different polymorphs and/or crystallization habits were initially seen for glycine and permanently formed for carbamazepine and ROY. Famoxadone crystallization was observed to be slower in microgravity. In all cases, the crystals were more uniform when grown in microgravity. For carbamazepine, the microgravity-grown crystals were larger. For space-grown glycine and carbamazepine, the crystal edges were visually sharper, the faces were visibly cleaner, and the individual crystals themselves had fewer imperfections from a visual inspection of about 10 crystals in each sample. This report doubles the number of small organic molecules crystallized in microgravity reported in the literature. We will continue our investigations as additional studies are needed to gain a more complete understanding of these examples as well as the way that small organic molecules behave when crystallized in a microgravity environment.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/cryst15060527/s1. Raman spectra of glycine and carbamazepine.

Author Contributions

Conceptualization: K.A.S., S.T. and A.M.W.; methodology: S.T. and A.M.W.; validation: S.T., L.M. and A.M.W.; formal analysis: L.M.; investigation: A.M.W. and K.A.S.; resources: K.A.S.; data curation: L.M. and A.M.W.; writing—original draft preparation: A.M.W. and S.T.; writing—review and editing: M.K.M. and K.A.S.; supervision: A.M.W. All authors have read and agreed to the published version of the manuscript.

Funding

The research was funded by CASIS Grant Agreement GA-2022-8872 and Redwire internal research and development funds.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.

Acknowledgments

We gratefully acknowledge the work of NASA astronauts Jaenette Epps, Mike Barratt, and Tracy Dyson for their assistance in performing the microgravity studies.

Conflicts of Interest

Author Molly K. Mulligan, Kenneth A. Savin, Stephen Tuma were employed by the company Redwire. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Abbreviations

The following abbreviations are used in this manuscript:
ISSInternational Space Station
PIL-BOXPharmaceutical In-space Laboratory (PIL)–Biocrystal Optimization eXperiment
ROY5-methyl-2-((2-nitrophenyl)amino)thiophene-3-carbonitrile
ADSEPADvanced Space Experiment Processor
SMALSSmall Molecule Accelerated Laboratory for Structure

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Figure 1. Target small-molecule compounds for crystallization in microgravity on the International Space Station (ISS).
Figure 1. Target small-molecule compounds for crystallization in microgravity on the International Space Station (ISS).
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Figure 2. Images of the ADSEP facility (A), a PIL-BOX DM (B), a fluid loop (C), and the basic schematic of the fluid loop (D).
Figure 2. Images of the ADSEP facility (A), a PIL-BOX DM (B), a fluid loop (C), and the basic schematic of the fluid loop (D).
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Crystals 15 00527 g003
Figure 3. Glycine ground controls: both rods (α) and blocks (α and potentially γ) on the edges of the chamber (A); both rods and blocks on the glass of the chamber (B). Images taken using a Leica S9D microscope.
Figure 3. Glycine ground controls: both rods (α) and blocks (α and potentially γ) on the edges of the chamber (A); both rods and blocks on the glass of the chamber (B). Images taken using a Leica S9D microscope.
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Crystals 15 00527 g004aCrystals 15 00527 g004b
Figure 4. In-flight screen captures: spindles (presumably β) ((A)—top left); rods and spindles (α and β) (B); spindles (presumably β) (C); rods (α) and blocks (γ) (D). Images taken using the onboard PIL-BOX SMALS microscope.
Figure 4. In-flight screen captures: spindles (presumably β) ((A)—top left); rods and spindles (α and β) (B); spindles (presumably β) (C); rods (α) and blocks (γ) (D). Images taken using the onboard PIL-BOX SMALS microscope.
Crystals 15 00527 g004aCrystals 15 00527 g004b
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Figure 5. Ground observation after flight; all cubes of α-glycine. Image taken using a Leica S9D microscope.
Figure 5. Ground observation after flight; all cubes of α-glycine. Image taken using a Leica S9D microscope.
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Figure 6. Clusters of spherulitic famoxadone crystals generated terrestrially. Image taken using a Leica S9D microscope.
Figure 6. Clusters of spherulitic famoxadone crystals generated terrestrially. Image taken using a Leica S9D microscope.
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Figure 7. Famoxadone crystal images taken at different depths in the same chamber on the ISS showing the central point of growth (A) for some crystals, and spherulitic clumps (B) for other crystals. Images taken using the PIL-BOX SMALS onboard microscope.
Figure 7. Famoxadone crystal images taken at different depths in the same chamber on the ISS showing the central point of growth (A) for some crystals, and spherulitic clumps (B) for other crystals. Images taken using the PIL-BOX SMALS onboard microscope.
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Figure 8. Final spherulites of Famoxadone taken upon return to Earth. Image taken using a Leica S9D microscope.
Figure 8. Final spherulites of Famoxadone taken upon return to Earth. Image taken using a Leica S9D microscope.
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Figure 9. Carbamazepine-I needles; ground study. Image taken with a Leica S9D Microscope.
Figure 9. Carbamazepine-I needles; ground study. Image taken with a Leica S9D Microscope.
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Figure 10. Carbamazepine-III crystals from the flight experiment that were wider (A) and longer (B) when taken upon return to Earth. Images taken using a Raman microscope.
Figure 10. Carbamazepine-III crystals from the flight experiment that were wider (A) and longer (B) when taken upon return to Earth. Images taken using a Raman microscope.
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Figure 11. Ground-based ROY crystals comprising yellow plates and orange needles. Image taken using a Raman Microscope.
Figure 11. Ground-based ROY crystals comprising yellow plates and orange needles. Image taken using a Raman Microscope.
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Figure 12. Irregular yellow ROY crystals taken during the crystallization process in microgravity. Images taken with the PIL-BOX SMALS onboard microscope.
Figure 12. Irregular yellow ROY crystals taken during the crystallization process in microgravity. Images taken with the PIL-BOX SMALS onboard microscope.
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Figure 13. Yellow prisms (A) and orange–red prisms (B) of ROY crystals. Images taken using a Raman microscope.
Figure 13. Yellow prisms (A) and orange–red prisms (B) of ROY crystals. Images taken using a Raman microscope.
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Table 1. Solution conditions for microgravity experiments.
Table 1. Solution conditions for microgravity experiments.
Substrate (Amount)Solvent (Amount)Antisolvent
Glycine (198.7 mg)Water (2 mL)Ethanol
Famoxadone (48.3 mg)Acetone (4.5 mL)Water–acetone (4:1)
Carbamazepine (117.4 mg)Acetonitrile–water (2:1, 9 mL)Water
ROY (94.6 mg)Acetone (9 mL)Water–acetone (4:1)
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Miller, L.; Mulligan, M.K.; Savin, K.A.; Tuma, S.; Wilson, A.M. Crystallization of Small Molecules in Microgravity Using Pharmaceutical In-Space Laboratory–Biocrystal Optimization eXperiment (PIL-BOX). Crystals 2025, 15, 527. https://doi.org/10.3390/cryst15060527

AMA Style

Miller L, Mulligan MK, Savin KA, Tuma S, Wilson AM. Crystallization of Small Molecules in Microgravity Using Pharmaceutical In-Space Laboratory–Biocrystal Optimization eXperiment (PIL-BOX). Crystals. 2025; 15(6):527. https://doi.org/10.3390/cryst15060527

Chicago/Turabian Style

Miller, Lillian, Molly K. Mulligan, Kenneth A. Savin, Stephen Tuma, and Anne M. Wilson. 2025. "Crystallization of Small Molecules in Microgravity Using Pharmaceutical In-Space Laboratory–Biocrystal Optimization eXperiment (PIL-BOX)" Crystals 15, no. 6: 527. https://doi.org/10.3390/cryst15060527

APA Style

Miller, L., Mulligan, M. K., Savin, K. A., Tuma, S., & Wilson, A. M. (2025). Crystallization of Small Molecules in Microgravity Using Pharmaceutical In-Space Laboratory–Biocrystal Optimization eXperiment (PIL-BOX). Crystals, 15(6), 527. https://doi.org/10.3390/cryst15060527

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