Dissolution and antioxidant potential of apigenin self nanoemulsifying drug delivery system (SNEDDS) for oral delivery.

Self-nanoemulsifying drug delivery systems (SNEDDS) have been used to improve the oral bioavailability of various drugs. In the current study, apigenin was developed as SNEDDS to solve its dissolution problem and enhance oral bioavailability and antioxidant potential. SNEDDS were prepared by mixing Gelucire 44/14, Tween 80, and PEG 400 under controlled conditions. The droplet of diluted SNEDDS demonstrated a spherical shape with a size of less than 100 nm and a neutral charge. The very fast self-emulsification was obtained within 32 s, and the transmittance values exceeded 99%. The highest drug loading was 90.10 ± 0.24% of the initial load with the highest %encapsulation efficiency of 84.20 ± 0.03%. FT-IR and DSC spectra showed no interaction between components. The dissolution in buffer pH 1.2, 4.5, and 6.8 showed significantly higher dissolved apigenin than the apigenin coarse powder. The dissolution profiles were fitted to the Korsmeyer-Peppas kinetics. The cellular antioxidant activities in Caco-2 cells were approximately 52.25-54.64% compared to no treatment and were higher than the apigenin coarse powder (12.70%). Our work highlights the potential of SNEDDS to enhance the dissolution and permeability of apigenin and promote antioxidant efficacy, which has a strong chance of being developed as a bioactive compound for nutraceuticals.

Controlled Sublimation Rate of Guest Drug from Polymorphic Forms of a Cyclodextrin-Based Polypseudorotaxane Complex and Its Correlation with Molecular Dynamics as Probed by Solid-State NMR.

Encapsulation of active pharmaceutical ingredients (APIs) in confined spaces has been extensively explored as it dramatically alters the molecular dynamics and physical properties of the API. Herein, we explored the effect of encapsulation on the molecular dynamics and physical stability of a guest drug, salicylic acid (SA), confined in the intermolecular spaces of γ-cyclodextrin (γ-CD) and poly(ethylene glycol) (PEG)-based polypseudorotaxane (PPRX) structure. The sublimation tendency of SA encapsulated in three polymorphic forms of the γ-CD/PEG-based PPRX complex, monoclinic columnar (MC), hexagonal columnar (HC), and tetragonal columnar (TC), was investigated. The SA sublimation rate was decreased by 3.0-6.6-fold and varied in the order of MC form > HC form > TC form complex. The 13C and 1H magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectra and 13C spin-lattice relaxation time (T1) indicated that the encapsulated SA molecules existed as the monomeric form, and its molecular mobility increased in the order of MC form > HC form > TC form complex. In the complexes, a rapid chemical exchange between two dynamic states of SA (free and bound) was suggested, with varying adsorption/desorption rates accounting for its distinct molecular mobility. This adsorption/desorption process was influenced by proton exchange at the interaction site and interaction strength of SA in the complexes, as evidenced by 1H MAS spectra and temperature dependency of the 13C carbonyl chemical shift. A positive correlation between the molecular mobility of SA and its sublimation rate was established. Moreover, the molecular mobility of γ-CD and PEG in the complexes coincided with that of SA, which can be explained by fast guest-driven dynamics. This is the first report on the stability improvement of an API through complexation in polymorphic supramolecular host structures. The relationship between the molecular dynamics and physical properties of encapsulated API will aid in the rational design of drug delivery systems.

Analysis of Lutein Content in Microencapsulated Marigold Flower Extract (Tagetes erecta L.) Using UHPLC-Q-Orbitrap-HRMS and Its Cytotoxicity in ARPE-19 Cells.

Organic solvents are commonly used to extract lutein. However, they are toxic and are not environmental-friendly. There are only a few reports on the quantification of lutein. Therefore, this study aimed to determine a suitable extraction method by which to obtain lutein from marigold flower (Tagetes erecta L.), using coconut oil to evaluate the cytotoxicity of extract in ARPE-19 cells, to optimize the encapsulation process for the development of microencapsulated marigold flower extract, and to develop the method for analysis of lutein by using UHPLC-Q-Orbitrap-HRMS. Coconut oil was used for the extraction of marigold flowers with two different extraction methods: ultrasonication and microwave-assisted extraction. The UHPLC-Q-Orbitrap-HRMS condition for the analysis of lutein was successfully developed and validated. Marigold flower extract obtained using the microwave method had the highest lutein content of 27.22 ± 1.17 mg/g. A cytotoxicity study revealed that 16 µM of lutein from marigold extract was non-toxic to ARPE-19 cells. For the development of microencapsulated marigold extract, the ratio of oil to wall at 1:5 had the highest encapsulation efficiency and the highest lutein content. Extraction of lutein using coconut oil and the microwave method was the suitable method. The microencapsulated marigold extract can be applied for the development of functional ingredients.

Non-Destructive Analysis of Chlorpheniramine Maleate Tablets and Granules by Chemometrics-Assisted Attenuated Total Reflectance Infrared Spectroscopy.

Non-destructive analysis of chlorpheniramine maleate (CPM), pharmaceutical tablets, and granules was conducted by chemometrics-assisted attenuated total reflectance infrared spectroscopy (ATR-IR). For tablets, an optimum PLSR model with eight latent factors was obtained from area-normalized and standard normal variate (SNV) pretreated ATR-IR spectral data with correlation coefficients (R2) of calibration and cross-validation of 0.9716 and 0.9602, respectively. The model capability for the 42 test set samples was proven with R2 between the reference and model prediction values of 0.9632, and a root-mean-square error of prediction (RMSEP) of 1.7786. The successive PLSR model for granules was constructed from SNV and first derivative pretreated ATR-IR spectral data with two latent factors and correlation coefficients (R2) of calibration and cross-validation of 0.9577 and 0.9450, respectively.

Effects of Wall Material on Medium-Chain Triglyceride (MCT) Oil Microcapsules Prepared by Spray Drying.

A medium-chain triglyceride (MCT) oil microcapsule was prepared by spray drying. The effects of the wall-material parameters of wall-to-oil ratio (1:1 to 3:1) and type of wall material (gum arabic (GA), whey protein isolate (WPI), and octenyl succinic anhydride (OSA) starch) on the microcapsules were evaluated. The droplet size, size distribution, viscosity, zeta potential, and stability of the emulsions were measured. The spray-dried powder was characterized by its morphology, yield, encapsulation efficiency, and moisture content. The wall material influenced the characteristics of the emulsions and microcapsules. The formulation with a 2:1 wall-to-oil ratio and OSA starch/maltodextrin as the wall material resulted in a small droplet size (0.177 ± 0.002 µm) with high encapsulation efficiency (98.38 ± 0.01%). This formulation had good physical stability over three months under accelerated conditions. Thus, OSA starch/maltodextrin is an appropriate wall material for encapsulating MCT oil.

The nanostructure of rod-like ascorbyl dipalmitate nanoparticles stabilized by a small amount of DSPE-PEG.

Previously, we reported the formation of 100-200 nm disk- and tube-like nanoparticles by hydration of L-ascorbyl 2,6-dipalmitate (ASC-DP) and distearoylphosphatidylethanolamine polyethylene glycol 2000 (DSPE-PEG) films prepared at an initial molar ratio of 2:1. This study investigated the feasibility of nanoparticle formation with higher ASC-DP loading. Although particle size distribution determined by dynamic light scattering showed a multimodal pattern including micro-sized particles at a molar ratio of 3:1, the mean particle size gradually decreased with a further increased molar ratio. Homogeneous ca. 240 nm nanoparticles with a unimodal size distribution were obtained at a molar ratio of 10:1. FE-TEM showed that the nanoparticles at a molar ratio of 10:1 were rod-shaped with a diameter of ca. 100 nm and a length of ca. 300 nm. After centrifugation, X-ray analysis of the nanoparticle precipitates showed that these rod-like nanoparticles were composed of a series of lamellar structures with 3.7 nm repeated units. The molar ratio of ASC-DP/DSPE-PEG in the nanoparticle precipitates determined by 1H NMR measurements was 68.8:1. The rod-like nanoparticles should be composed of a core-shell structure, where a small amount of DSPE-PEG covers the lamellar structure of ASC-DP. Further increase in the ASC-DP/DSPE-PEG molar ratio over 33:1 no longer provided nanoparticles. Hence, to prepare a stable ASC-DP nanoparticle suspension, it is necessary to prepare ASC-DP/DSPE-PEG films containing at least 3 mol% DSPE-PEG.

Size Reduction Efficiency of Alpha-Mangostin Suspension Using High-Pressure Homogenization.

In this study, we aimed to investigate the effects of stabilizers and processing parameters on the size reduction of alpha-mangostin (AMG) using high-pressure homogenization (HPH). The solubility of AMG in various stabilizers was studied. Selected stabilizers were used to prepare AMG suspensions by HPH under different conditions. After HPH, the particle size of AMG suspensions with stabilizers significantly decreased to microns. Percent size reduction efficiency of all AMG suspensions with each stabilizer increased with the increase in the number of homogenization cycles. Sodium lauryl sulfate and poloxamer188 provided a greater extent of particle size reduction than polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer. AMG suspensions with binary stabilizers at higher pressure were also prepared. The use of high pressure increased percent size reduction efficiency.

Composition-dependent structural changes and antitumor activity of ASC-DP/DSPE-PEG nanoparticles.

Ascorbyl 2,6-dipalmitate (ASC-DP) and distearoyl phosphatidylethanolamine polyethylene glycol 2000 (DSPE-PEG) formed stable nanoparticles at a molar ratio of less than or equal to 2:1 after dispersing the solvent-evaporated film in water. The mean particle sizes measured by dynamic light scattering were within the range of ca. 100-160nm. Composition-dependent changes of the ASC-DP and DSPE-PEG molecular states within the film were analyzed by wide-angle X-ray diffraction and infrared (IR) and solid-state nuclear magnetic resonance (NMR) spectroscopy. Transmission electron microscopy (TEM) of nanoparticles revealed that ASC-DP/DSPE-PEG changed from a micelle to a disk and tubular structure as the molar ratio increased. Quantitative solution-state 1H NMR measurements elucidated the structure of nanoparticle in water; the core could be composed of ASC-DP and hydrophobic acyl chains of DSPE, whereas the hydrophilic PEG chains of DSPE-PEG on the surface form the hydration shell to stabilize the nanoparticle dispersion in water. Cytotoxicity of ASC-DP against cancer cell lines was observed by using ASC-DP/DSPE-PEG nanoparticles, and no cytotoxicity against normal cells was found. Thus, the ASC-DP/DSPE-PEG formulation, with tumor cell specific cytotoxicity, can be applicable for cancer monotherapy or in combination with other anticancer drugs.

Mechanistic insight into the dramatic improvement of probucol dissolution in neutral solutions by solid dispersion in Eudragit E PO with saccharin.

OBJECTIVES: Solid dispersion using Eudragit E PO (EPO) improves the dissolution of poorly water-soluble drugs in acidic solutions; however, the dissolution extremely decreases in neutral solutions. In this report, ternary solid dispersions containing probucol (PBC), EPO, and saccharin (SAC) were prepared to enable high drug dissolution at neutral pH. METHODS: Cryogenic-grinding was used to obtain ternary solid dispersions. Dissolution tests at neutral pH values were conducted to confirm the usefulness of the cryogenic-ground mixture (cryo-GM). The molecular state of each component and intermolecular interactions in the ternary cryo-GM were evaluated using powder X-ray diffraction (PXRD) and (13) C solid-state NMR including spin-lattice relaxation time evaluation. KEY FINDINGS: PBC dispersed in ternary cryo-GM had an improved dissolution in neutral solutions. PBC and SAC were in amorphous states in EPO polymer matrices. The weak hydrophobic interaction between PBC and EPO and the ionic bond or hydrogen bond between EPO and SAC were demonstrated. These two molecular interactions improved the dissolution of PBC in neutral solutions. CONCLUSION: Preparation of ternary solid dispersion is a potential method of improving drug solubility and absorption.

Design of one-dimensional power spectrum using two-dimensional fast Fourier transform for discrimination of paper-based kraft tapes.

A novel type of spectrum, the one-dimensional power spectrum (1D-PS), was designed for the discrimination of adhesive packing tapes, i.e., kraft tapes. The 1D-PS offered complementary information to that provided by the improved two-dimensional PS (2D-PS), which was calculated using our previously established image processes combined with a two-dimensional fast Fourier transform (2D-FFT) to obtain information about the spatial periodicity within kraft tapes. The 1D-PS was calculated using a three-step image process: (i) the 2D-FFT was applied to 50 randomly selected areas in a transmitted light image; (ii) the obtained 2D-PSs were accumulated without applying a logarithmic transform; (iii) the wavenumber and the maximum intensity were plotted on the x-axis and y-axis, respectively. Through an intra-roll comparison, the 1D-PSs collected from single rolls showed similar profiles. In an inter-roll comparison, the 1D-PSs from 50 commercially available brand-name products were classified into 29 groups. The 1D-PSs contained other useful information than that provided by the improved 2D-PSs: they presented more peaks and absolute intensity with a wider range. The 1D-PSs enabled us to compare the spectra quickly and easily, owing to their unchanging profiles regardless of the orientation of the scanned images. A combined use of the 1D-PSs with the improved 2D-PSs-both spectrum types being convenient, rapid, non-destructive, and applicable to dirty and/or damaged samples-could further improve the identification of kraft tapes.

Encapsulation of poorly water-soluble drugs into organic nanotubes for improving drug dissolution.

Hydrocortisone (HC), a poorly water-soluble drug, was encapsulated within organic nanotubes (ONTs), which were formed via the self-assembly of N-{12-[(2-α,ß-d-glucopyranosyl) carbamoyl]dodecanyl}-glycylglycylglycine acid. The stability of the ONTs was evaluated in ten organic solvents, of differing polarities, by field emission transmission electron microscopy. The ONTs maintained their stable tubular structure in the highly polar solvents, such as ethanol and acetone. Furthermore, solution-state (1)H-NMR spectroscopy confirmed that they were practically insoluble in acetone at 25°C (0.015 mg/mL). HC-loaded ONTs were prepared by solvent evaporation using acetone. A sample with a 3/7 weight ratio of HC/ONT was analyzed by powder X-ray diffraction, which confirmed the presence of a halo pattern and the absence of any crystalline HC peak. HC peak broadening, observed by solid-state (13)C-NMR measurements of the evaporated sample, indicated the absence of HC crystals. These results indicated that HC was successfully encapsulated in ONT as an amorphous state. Improvements of the HC dissolution rate were clearly observed in aqueous media at both pH 1.2 and 6.8, probably due to HC amorphization in the ONTs. Phenytoin, another poorly water-soluble drug, also showed significant dissolution improvement upon ONT encapsulation. Therefore, ONTs can serve as an alternative pharmaceutical excipient to enhance the bioavailability of poorly water-soluble drugs.

Drug solubilization mechanism of α-glucosyl stevia by NMR spectroscopy.

We investigated the drug solubilization mechanism of α-glucosyl stevia (Stevia-G) which was synthesized from stevia (rebaudioside-A) by transglycosylation. (1)H and (13)C NMR peaks of Stevia-G in water were assigned by two-dimensional (2D) NMR experiments including (1)H-(1)H correlation, (1)H-(13)C heteronuclear multiple bond correlation, and (1)H-(13)C heteronuclear multiple quantum coherence spectroscopies. The (1)H and (13)C peaks clearly showed the incorporation of two glucose units into rebaudioside-A to produce Stevia-G, supported by steviol glycoside and glucosyl residue assays. The concentration-dependent chemical shifts of Stevia-G protons correlated well with a mass-action law model, indicating the self-association of Stevia-G molecules in water. The critical micelle concentration (CMC) was 12.0 mg/mL at 37°C. The aggregation number was 2 below the CMC and 12 above the CMC. Dynamic light scattering and 2D (1)H-(1)H nuclear Overhauser effect spectroscopy (NOESY) NMR experiments demonstrated that Stevia-G self-associated into micelles of a few nanometers in size with a core-shell structure, containing a kaurane diterpenoid-based hydrophobic core and a glucose-based shell. 2D (1)H-(1)H NOESY NMR measurements also revealed that a poorly water-soluble drug, naringenin, was incorporated into the hydrophobic core of the Stevia-G micelle. The Stevia-G self-assembly behavior and micellar drug inclusion capacity can achieve significant enhancement in drug solubility.

Characterization of cromolyn sodium hydrates and its formulation by (23) Na-multiquantum and magic-angle spinning nuclear magnetic resonance spectroscopy.

We characterized cromolyn sodium (CS) hydrates and evaluated their molecular states in low-dose formulations using Na-multiquantum magic-angle spinning (MQMAS) nuclear magnetic resonance (NMR) analysis. Two CS hydrates, low-water-content hydrated form and high-water-content hydrated form containing 2-3 and 5-6 hydrates, respectively, were prepared by humidification. Single-crystal X-ray diffraction and powder X-ray diffraction analysis revealed that these CS hydrates contained sodium channel structures and that water molecules were adsorbed on the sodium nucleus. (13) C-cross-polarization/MAS NMR spectra of these hydrates revealed similar results, confirming that the water molecules were adsorbed not on the cromolyn skeletons but mainly on the sodium nucleus. In contrast, (23) Na-MQMAS NMR analysis allowed us to clearly distinguish these hydrates without discernible effects from quadrupolar interaction. Thus, MQMAS NMR analysis is a valuable tool for evaluating salt drugs and their formulations.

Nano-sized crystalline drug production by milling technology.

Nano-formulation of poorly water-soluble drugs has been developed to enhance drug dissolution. In this review, we introduce nano-milling technology described in recently published papers. Factors affecting the size of drug crystals are compared based on the preparation methods and drug and excipient types. A top-down approach using the comminution process is a method conventionally used to prepare crystalline drug nanoparticles. Wet milling using media is well studied and several wet-milled drug formulations are now on the market. Several trials on drug nanosuspension preparation using different apparatuses, materials, and conditions have been reported. Wet milling using a high-pressure homogenizer is another alternative to preparing production-scale drug nanosuspensions. Dry milling is a simple method of preparing a solid-state drug nano-formulation. The effect of size on the dissolution of a drug from nanoparticles is an area of fundamental research, but it is sometimes incorrectly evaluated. Here, we discuss evaluation procedures and the associated problems. Lastly, the importance of quality control, process optimization, and physicochemical characterization are briefly discussed.

Mechanistic differences in permeation behavior of supersaturated and solubilized solutions of carbamazepine revealed by nuclear magnetic resonance measurements.

A solid dispersion (SPD) of carbamazepine (CBZ) with hydroxypropyl methylcellulose acetate succinate (HPMC-AS) was prepared by the spray drying method. The apparent solubility (37 °C, pH 7.4) of CBZ observed with the SPD was over 3 times higher than the solubility of unprocessed CBZ. The supersaturated solution was stable for 7 days. A higher concentration of CBZ in aqueous medium was also achieved by mixing with Poloxamer 407 (P407), a solubilizing agent. From permeation studies of CBZ using Caco-2 monolayers and dialysis membranes, we observed improved CBZ permeation across the membrane in the supersaturated solution of CBZ/HPMC-AS SPD. On the contrary, the CBZ-solubilized P407 solution exhibited poor permeation by CBZ. The chemical shifts of CBZ on the (1)H NMR spectrum from CBZ/HPMC-AS SPD solution were not altered significantly by coexistence with HPMC-AS. In contrast, an upfield shift of CBZ was observed in the CBZ/P407 solution. The spin-lattice relaxation time (T(1)) over spin-spin relaxation time (T(2)) indicated that the mobility of CBZ in the HPMC-AS solution was much lower than that in water. Meanwhile, the mobility of CBZ in P407 solution was significantly higher than that in water. NMR data indicate that CBZ does not strongly interact with HPMC-AS. CBZ mobility was suppressed due to self-association and microviscosity around CBZ, which do not affect permeation behavior. Most of the CBZ molecules in the CBZ/P407 solution were solubilized in the hydrophobic core of P407, and a few were free to permeate the membrane. The molecular state of CBZ, as evaluated by NMR measurements, directly correlated with permeation behavior.

Formation mechanism of a new carbamazepine/malonic acid cocrystal polymorph.

A new 2/1 carbamazepine (CBZ)/malonic acid (MA) cocrystal polymorph form C was formed using a vibrational rod mill, whereas the known cocrystal polymorph form A was prepared using a ball mill. IR measurements showed that the interaction between CBZ and MA in cocrystal form C was formed by amide-carboxylic acid heterosynthons, similar to that in cocrystal form A. However, NMR results showed that the molecular states of CBZ at the dibenzazepine ring appeared to be different, which could be due to variation in either the conjugation of the aromatic rings or the π-π interaction of CBZ. Factors affecting the formation of cocrystal polymorphs, such as heat and force, were investigated to clarify the formation mechanism.

Mechanism of nanoparticle formation from ternary coground phenytoin and its derivatives.

The mechanism of drug nanoparticle formation of phenytoin (DPH) and its derivatives monomethylphenytoin (MDPH) and dimethylphenytoin (DMDPH) was investigated. The drug, polyvinylpyrrolidone K17 (PVP), and sodium dodecyl sulfate were coground to obtain the ground mixture (GM). The DPH GM was amorphous; however, MDPH and DMDPH GMs contained drug crystals. Spectral changes in infrared and (13)C solid-state nuclear magnetic resonance were observed in the DPH GM, partially observed in the MDPH GM, and hardly observed in the DMDPH GM. Mean particle sizes of the DPH, MDPH, and DMDPH GM nanosuspension were almost the same; however, stability after storage differed in the order of DPH > MDPH > DMDPH. The intermolecular interaction between the drug and PVP reflected not only the crystallinity of the drug in the GM but also the stability of the GM suspension. The size and stiffness of drug nanoparticles were evaluated using atomic force microscopy. Crystallization of the amorphous GM and agglomeration of the primary nanocrystals were observed in the DPH GM suspension. In contrast, primary nanocrystals were observed in the DMDPH GM suspension. The size of the drug nanocrystals formed from the different molecular states of the drug in the GM reflects the agglomerated states in water and stability.

Yellow coloration phenomena of incorporated indomethacin into folded sheet mesoporous materials.

Solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy that included relaxation time measurement was utilized to evaluate the yellow coloration of evaporated samples (EVPs) of indomethacin (IMC) with commercially available folded sheet mesoporous materials (TMPS). Colorimetric analysis by visible light reflection spectroscopy clarified the color differences in each sample: deep yellow-colored melt-quenched amorphous IMC, a slightly yellow-colored EVP of TMPS-1.5 (pore size: 1.8nm), and a yellow-colored EVP of TMPS-7 (pore size: 7.3nm). The color of EVPs changed from yellow to white after washing with ethanol, indicating the reversible coloration without a chemical reaction. Powder X-ray diffractometry and differential scanning calorimetry demonstrated that the EVPs of TMPS-7 entrapped greater amounts of amorphous IMC into the mesopore than TMPS-1.5. The amount of amorphous IMC in the mesopores could affect the strength of yellow coloration. Solid-state (13)C NMR spectroscopy that included spin-lattice relaxation time (T(1)) measurement revealed that the mobility of the aromatic rings of amorphous IMC in TMPS mesopores was higher than that in melt-quenched amorphous IMC. The difference in color between amorphous IMC in TMPS mesopores and melt-quenched amorphous IMC can be explained by their distinct intramolecular π-conjugation systems.

Discrimination of paper-based kraft tapes using Fourier transform of transmitted light images.

This study focused on two-dimensional fast Fourier transform (2D-FFT) as a new technique for the discrimination of kraft tapes, which is a kind of adhesive packing tape. The 2D power spectrum (2D-PS) obtained by applying 2D-FFT to an image enables us to obtain information about the spatial periodicity, even if the periodicity is invisible within the image. However, in the case of kraft tape, peaks in the 2D-PS are too unclear to determine its periodicity. We developed novel analytical image processes combined with 2D-FFT. 2D-FFT was applied to 50 randomly selected areas in a transmitted light image of kraft tape. The 2D-PSs were calculated from each area without applying a logarithmic transformation, accumulated, and processed by the removal of the area surrounding the center, and finally normalized for visualization. These processes enhanced the peaks and eliminated local variations. Through an intra-roll comparison, the 2D-PSs collected from a roll were similar in the location of the peaks and in their patterns at low frequency area. Using an inter-roll comparison, the 2D-PSs from 50 commercially available brand-name products were classified into 26 groups based on these peaks and patterns. All results demonstrate that this method, which is convenient, rapid, and non-destructive, could be a valuable tool for the identification of kraft tapes.

Structural evaluation of probucol nanoparticles in water by atomic force microscopy.

Structural evaluation of probucol nanoparticles coground with polyvinylpyrrolidone K17 and sodium dodecyl sulfate for 90 min was performed by solid-state nuclear magnetic resonance (NMR) spectroscopy and atomic force microscopy (AFM) with force-distance curve analysis. The results of solid-state NMR indicated that the cogrinding changed crystalline probucol to amorphous form. The number-averaged mean heights of probucol particles in the ground mixture (GM) suspension were determined by AFM to be 6 and 15 nm for freshly prepared and 24h-stored samples, respectively. Nucleation and the subsequent crystal growth might have occurred after the GM was dispersed in water. The presence of probucol nanocrystals and agglomeration of the primary probucol nanoparticles were recognized by AFM force-distance curve analysis. AFM could be a promising tool to evaluate the structure of nanoparticles as well as their agglomeration behavior in aqueous media.