Enteric complex layer-coated controlled release of capsaicin from phytosterol/γ-cyclodextrin microparticles via guest exchange reaction with taurocholic acid

Phytosterol (PSE)/γ-cyclodextrin (γ-CD) microparticles have a capsule-like structure, wherein the hydrophobic PSE core is surrounded by outer layers of the hydrophilic PSE/γ-CD inclusion complex crystal. The microparticles could mask the undesirable taste of capsaicin (CAP) by encapsulation of CAP into the microparticles. In the present study, the dissolution of CAP from PSE/γ-CD microparticles into artificial intestinal fluids was examined using the paddle method. The dissolution of CAP from the microparticles was suppressed at pH 1.2 and 5.0. On the other hand, the dissolution was significantly enhanced in fasted and fed state simulated intestinal fluid (FaSSIF and FeSSIF) . Taurocholate (TCA), contained in these artificial fluids, induced rapid dissolution of CAP from microparticles. The mechanism of CAP dissolution from the microparticles in the presence of TCA was investigated using in situ¹H NMR spectroscopy. During the incubation of the mixed suspension of the microparticles and TCA, γ-CD peaks started to appear, and the TCA peak showed a gradual upfield shift. Quantitative analysis of NMR results showed that the TCA/γ-CD inclusion complex could form during incubation, according to the dissolution of γ-CD from the microparticles via the guest exchange reaction of PSE by TCA. The collapse of the PSE/γ-CD inclusion complex crystal at the outer shell of microparticles could trigger the release of CAP into the intestinal fluid. Thus, PSE/γ-CD microparticles can be used as an enteric controlled-release system that releases encapsulated drugs not via the conventional pH changes but via guest exchange reaction with TCA.

[Solid State NMR Investigation for Molecular States of Specialized Formulation to Improve the Water Solubility of Poorly Water-soluble Drugs]

70-90% of recently developed new drug candidates are poorly soluble in water, which creates a series of thorny challenges in developing its oral dosage forms, resulting in low bioavailability. In pre-formulation study, various specialized formulations have been developed to improve drug solubility. Intermolecular interactions between drug and excipients in the formulations can modify the drug state and achieve the improvement of drug solubility. Therefore, the understanding of intermolecular interaction is essential to design formulations with higher quality and to assure the quality as a pharmaceutical product. Solid-state NMR has attracted much attention as a promising method to evaluate the molecular state of a drug and the interaction between a drug and excipient in its formulation. I have applied solid-state NMR and its characteristic technique, namely magic-angle spinning (MAS), for various specialized formulations including amorphous solid dispersion, supersaturated solution, drug-loaded organic nanotube, and drug nanosuspension. The intermolecular interactions of drug and excipient in amorphous solid dispersion have been identified by ¹³C and ¹⁵N solid-state NMR. High-resolution MAS determined the interaction modes of drug and excipient in a supersaturated solution. The two-step dissolution profile of drug from organic nanotube was understood, based on the molecular states revealed by the combination of various solid-state NMR techniques. A suspended-state NMR clarified the nanostructure of drug nanoparticles dispersed in water. It is expected that more qualified pharmaceutical formulations with improved drug solubility can be designed based on the remarkable development of recent solid-state NMR technology.

Revealing the mechanism of morphological variation of amorphous drug nanoparticles formed by aqueous dispersion of ternary solid dispersion

Probucol (PBC)/hypromellose (HPMC)/sodium dodecyl sulfate (SDS) ternary solid dispersions (SDs) of various weight ratios were prepared and evaluated to unveil the effect of HPMC and SDS on the formation of amorphous PBC nanoparticles. The morphological variation of the PBC nanoparticles prepared using SDs of different compositions was determined using dynamic light scattering and cryogenic transmission electron microscopy (cryo-TEM). Statistical analysis of particle size versus roundness of PBC nanoparticles was carried out based on cryo-TEM images. A clear correlation was observed between the morphologies of the PBC nanoparticles and the amounts of HPMC and SDS, either admixed in SDs or pre-dissolved in an aqueous solution. The admixed HPMC in SDs was demonstrated to play the major role in determining the primary particle sizes of discrete amorphous PBC nanoparticles. Based on ¹³C solid-state NMR spectroscopy, this phenomenon should be due to the enlarged size of the PBC-rich domains in SDs, which depended on the decreasing amounts of admixed HPMC. Although the pre-dissolved part of HPMC had less impact on the primary particle sizes, it was found to inhibit the particle agglomeration and recrystallization of amorphous PBC nanoparticles. On the other hand, sufficient SDS admixed in SDs could suppress the size enhancement of the PBC-rich domains during water immersion and nanoparticle evolution (agglomeration and crystallization) after aqueous dispersion. The pre-dissolved SDS could restrain the agglomeration of amorphous PBC nanoparticles, ultimately forming hundreds of irregular nanometer-order structures. Since the increase in size during water immersion, their sizes were still slightly larger than those obtained with a high portion of admixed SDS. The findings of this study clarified the usefulness and necessity of adding polymers and surfactants to SDs to fabricate drug nanoparticle formulations.

Amorphous Drug Solubility and Maximum Free Drug Concentrations in Cyclodextrin Solutions: A Quantitative Study Using NMR Diffusometry

Cyclodextrin (CD) has been widely used as a solubilizing agent for poorly water-soluble drugs. In the present study, the effect of CD on the amorphous drug solubility and the maximum thermodynamic activity of the drug in the aqueous phase when the drug concentration exceeded the liquid-liquid phase separation (LLPS) concentration was investigated using three chemically diverse CDs, β-cyclodextrin (β-CD), dimethyl-β-CD (DM-β-CD), and hydroxypropyl-β-CD (HP-β-CD). The amorphous solubility of ibuprofen (IBP) increased substantially linearly with the increase in the CD concentration due to IBP/CD complex formation. Surprisingly, although the crystalline solubility of IBP in the β-CD solution reached a plateau at β-CD concentrations above 3 mM (B_S-type solubility diagram) because of the limited crystalline solubility of the IBP/β-CD complex, the amorphous solubility of IBP increased linearly even when the β-CD concentration was higher than 3 mM. The amorphous solubility of IBP in CD solutions was influenced primarily by the phase separation of the IBP-supersaturated solution to the aqueous phase and the other phase mainly composed of IBP, namely, the IBP-rich phase, via LLPS. NMR spectroscopy revealed that DM-β-CD was distributed into the IBP-rich phase when the IBP concentration exceeded its amorphous solubility, while β-CD and HP-β-CD showed minimal mixing with the IBP-rich phase. NMR diffusometry showed that the maximum free IBP concentration was reduced in the DM-β-CD solution compared to that in the buffer. The mixing of DM-β-CD with the IBP-rich phase reduced the chemical potential of IBP in the IBP-rich phase, which in turn reduced the maximum thermodynamic activity of IBP in the aqueous phase. In contrast, the maximum free IBP concentration was unchanged when β-CD or HP-β-CD was present. The hydrophobic nature of the DM-β-CD substituent may contribute to its partitioning into the IBP-rich phase. The present study highlights the impact of CD on the maximum thermodynamic activity of drugs as well as the apparent amorphous solubility of the drug. This aspect should be considered for improving the effective absorption of poorly water-soluble drugs.

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.

Unveiling the Interaction Potential Surface between Drug-Entrapped Polymeric Micelles Clarifying the High Drug Nanocarrier Efficiency

Polymeric micelles are invaluable media as drug nanocarriers. Although knowledge of an interaction between the micelles is a key to understanding the mechanisms and developing the superior functions, the interaction potential surface between drug-incorporated polymeric micelles has not yet been quantitatively evaluated due to the extremely complex structure. Here, the interaction potential surface between drug-entrapped polymeric micelles was unveiled by combining a small-angle scattering experiment and a model-potential-free liquid-state theory. Triblock copolymer composed of poly(ethylene oxide) and poly(propylene oxide) was investigated over a wide concentration range (0.5-10.0 wt %). Effects of the entrapment of a water-insoluble hydrophobic drug, cyclosporin A, on the interaction were explored by comparing the interactions with and without the drug. The results directly clarified the high drug carrier efficiency in terms of the interaction between the micelles. In addition, an investigation based on density functional theory provided a deeper insight into the monomer contribution to the extremely stable dispersion of the nanocarrier.

Mechanistic study of preparation of drug/polymer/surfactant ternary hot extrudates to obtain small and stable drug nanocrystal suspensions

We studied optimized conditions for preparing ternary hot extrudates (HEs) of glibenclamide (GLB)/polyvinylpyrrolidone (PVP)/sodium dodecyl sulfate to generate stable nanocrystal suspensions following aqueous dispersion. Raman and solid-state NMR measurements of ternary HEs prepared by altering HE conditions revealed that GLB crystallinity in HEs reduced with increased extrusion temperature and count and decreased screw speed. Aqueous dispersions of all HEs temporarily formed GLB nanoparticles with a diameter of 75-420 nm. The suspension from the HEs with the low GLB crystallinity (<22%) precipitated after 4-h storage, while the HEs with the high GLB crystallinity (>22%) formed stable nanocrystal suspension. Interestingly, the number of GLB nanoparticles <150  nm was different despite aqueous dispersion of HEs with similar GLB crystallinity, reflecting the different GLB crystalline size in those HEs. Although both the crushing by shear force and GLB dissolution into PVP reduced GLB crystalline size, the crushing GLB crystal by the shear force has a relatively high ability to decrease GLB crystalline size without excess amorphization of GLB. Performing the hot extrusion at a low temperature, a high screw speed, and maximizing extrusion count with GLB crystallinity >22% led to formation of small and stable nanocrystal suspensions.

Concrete with high-purity volcanic glass fine powder manufactured from pyroclastic deposit

Volcanic deposits, which are pozzolanically reactive, have long been known to improve the durability of concrete. Nevertheless, it has also been pointed out that the use of a natural pozzolan as a supplementary cementitious material (SCM) can pose problems of low workability and slow strength development. Also, in addition, its composition and physical properties have large variety and variability. We have been conducting studies on the total utilization of volcanic deposits for applications suitable for respective properties by classifying them by floating speed difference and particle diameter. It is reported that sorting out particles less than 2.4 g/cm3 by dry gravity classification and removal of smaller clay fraction by dust collector is technically effective to recover high purity volcanic glass from pyroclastic flow deposits called “Ito-Shirasu”, which is a local name for pyroclastic flow deposits in Japan. In this study, concrete containing high-purity volcanic glass powders with different finenesses are investigated regarding fresh properties, strength development, chloride ion penetration and CO2 reduction. As a result, it was found that volcanic glass powders made an excellent contribution to the improvement of flowability comparable to fly ash, the enhancement of strength comparable to silica fume, and the restraint of chloride ion penetration. Volcanic glass powders can also contrbute to the reduction of CO2 emission because the content of Portland cement can be significantly reduced to obtain the same strength compared to concrete with 100% Portland cement. This study provides a possibility to produce high performance SCMs in volcanic regions worldwide from volcanic ejecta by sorting out a high purity volcanic glass by the same method.

Application of solid-state 13C relaxation time to prediction of the recrystallization inhibition strength of polymers on amorphous felodipine at low polymer loading

The potential for inhibiting recrystallization with Eudragit® L (EUD-L), hypromellose acetate succinate (HPMC-AS), and polyvinylpyrrolidone-co-vinylacetate (PVP-VA) on amorphous felodipine (FLD) at low polymer loading was investigated in this study. The physical stabilities of the FLD/polymer amorphous solid dispersions (ASDs) were investigated through storage at 40 °C. The HPMC-AS and PVP-VA strongly inhibited FLD recrystallization, although EUD-L did not effectively inhibit the FLD recrystallization. The rotating frame ¹H spin-lattice relaxation time (¹H-T_1ρ) measurement clarified that EUD-L was not well mixed with FLD in the ASD, which resulted in weak inhibition of recrystallization by EUD-L. In contrast, the HPMC-AS and PVP-VA were well mixed with the FLD in the ASDs. Solid-state ¹³C spin-lattice relaxation time (¹³C-T₁) measurements at 40 °C showed that the molecular mobility of the FLD was strongly suppressed when mixed with polymer. The reduction in the molecular mobility of FLD was in the following order, starting with the least impact: FLD/EUD-L ASD, FLD/HPMC-AS ASD, and FLD/PVP-VA ASD. FLD mobility at the storage temperature, evaluated by ¹³C-T₁, showed a good correlation with the physical stability of the amorphous FLD. The direct investigation of the molecular mobility of amorphous drugs at the storage temperature by solid-state NMR relaxation time measurement can be a useful tool in selecting the most effective crystallization inhibitor at low polymer loading.

Intermolecular Interactions between Drugs and Aminoalkyl Methacrylate Copolymer in Solution to Enhance the Concentration of Poorly Water-Soluble Drugs

An aminoalkyl methacrylate copolymer, Eudragit^® E (EUD-E), has gained tremendous attention as a solid dispersion carrier because it efficiently stabilizes drugs in the amorphous state. Furthermore, EUD-E remarkably enhances drug dissolution in water. This review focuses on the interaction between drugs and EUD-E in solution, which contributes to the enhancement of drug concentration. Studies examining interactions between acidic drugs and EUD-E in organic solvents have revealed that the interaction occurs predominantly by electrostatic interaction, including hydrogen bonding and dipolar interactions. Other studies on interactions in aqueous solution found evidence for strong electrostatic interactions between acidic drugs and EUD-E in ion exchange experiments. ¹H-NMR studies using high-resolution magic-angle spinning, nuclear Overhauser effect spectroscopy, diffusion, and relaxation time measurements successfully identified the interaction site and strength in aqueous solution. Hydrophobic and ionic interactions occurred between drugs and EUD-E. The conformation of EUD-E, which was affected by the ionic strength and pH of the aqueous media, also influenced the interaction. The knowledge discussed in this review will be helpful in designing solid dispersion formulations with EUD-E, which will efficiently enhance drug concentration and subsequent absorption into the body.

Mechanistic elucidation of formation of drug-rich amorphous nanodroplets by dissolution of the solid dispersion formulation

Drug-rich amorphous nanodroplets have great potential to improve intestinal absorption of poorly water-soluble drugs. Spray-dried samples (SPDs) of glibenclamide (GLB) with hypromellose (HPMC) or hypromellose acetate succinate (HPMC-AS, grade AS-LF and AS-HF) were prepared to investigate how GLB-rich amorphous nanodroplets form during the dissolution of solid dispersions. The co-spray drying of AS-LF significantly enhanced GLB dissolution from the SPD, leading to the temporary formation of GLB-rich amorphous nanodroplets. However, the droplets gradually coarsened as AS-LF fails to inhibit coarsening. In contrast, the addition of HPMC to the SPD failed to aid GLB-rich amorphous nanodroplet formation during dissolution. The failure of formation of GLB-rich amorphous nanodroplet was caused by slow GLB dissolution, due to the poor controllability of the GLB dissolution by HPMC. The addition of AS-HF to the SPD produced amorphous GLB particles that contained a large amount of AS-HF during dissolution. Gel-like particles formed instead of GLB-rich amorphous nanodroplets. When the SPD containing AS-LF was dissolved in AS-HF solution, stably-dispersed GLB-rich amorphous nanodroplets were successfully formed owing to rapid GLB dissolution from the SPD containing AS-LF and strong coarsening inhibition by AS-HF. Formulation optimization considering both aqueous dissolution of the solid dispersion and the inhibition of nanodroplet coarsening achieved stably-dispersed drug-rich amorphous nanodroplets.

A Novel Drug-Drug Cocrystal of Levofloxacin and Metacetamol: Reduced Hygroscopicity and Improved Photostability of Levofloxacin

Levofloxacin (LVFX), a broad-spectrum antibacterial agent from the fluoroquinolone family, is universally prescribed with antipyretics, including paracetamol (APAP) analogs. In this study, a new drug-drug cocrystal of LVFX and an APAP analog was developed using a grinding and heating approach. Among 9 APAP analogs, only metacetamol (AMAP) was able to form a cocrystal with LVFX, with a stoichiometric ratio of 1:1. This cocrystal was obtained from a eutectic melt of anhydrous LVFX and AMAP after complete desorption of water from LVFX hemihydrate. The crystal structure of the cocrystal was determined by single-crystal X-ray structural analysis. Unlike LVFX hydrates, the LVFX-AMAP cocrystal did not form a channel structure where water molecules reside in LVFX hydrates. Thus, the LVFX-AMAP cocrystal did not undergo hydration under high relative humidity conditions during vapor sorption-desorption analysis and physical stability tests. LVFX photostability was improved by cocrystallization when compared with that of the hemihydrate because of hydrogen bond formation between the hydroxyl group of AMAP and the N-methylpiperazine group of LVFX, which is possibly involved in LVFX photodegradation. The LVFX-AMAP cocrystal, which is superior to LVFX hydrates in both pharmacological and physicochemical properties, is expected to be a useful solid form.

[Design Features in the Molecular-level Development of Solid Pharmaceutical Formulations Based on Supramolecular Structures]

We focused on the crystal structure of cyclodextrin (CD) to develop new solid CD complexes. There are two large spaces in the columnar structure of CD crystals: one inside a CD cavity and another between CD columns. New solid CD complexes can be designed by incorporating guest drugs between the CD columns. We succeeded in preparing a solid drug/[polyethylene glycol (PEG)/γ-CD-polypseudoraxane (PPRX)] complex by a sealed-heating method via the gas phase. A drug/(PEG/γ-CD-PPRX) complex has a structure in which PEGs are included in a γ-CD cavity, and guest drugs are incorporated between the γ-CD columns. Screening by a sealed-heating method determined that a variety of guest drugs with varying molecular size and log P could be incorporated into the spaces between γ-CD columns, following a stoichiometric rule. Another method, via solid phase using cogrinding and subsequent heating, was developed to prepare drug/(PEG/γ-CD-PPRX) complex. This method enabled us to prepare the complex with a thermally unstable drug, as well as a drug/(PEG/α-CD-PPRX) complex not formed using the sealed-heating method. Both the structure and molecular state of each drug in the complexes were characterized by powder X-ray diffraction and solid-state NMR measurements. The dissolution character and thermal stability of the drug incorporated in the complex could be improved by the specific complex formation. The solid CD complexes thus developed have potential for drug-encapsulation and as drug-release carriers, owing to their unique structural and pharmaceutical properties.

An Insight into Stabilization Mechanism of a Solid Dispersion of Indomethacin/Partially Hydrolyzed Polyvinyl Alcohol Prepared by Hot-Melt Extrusion

We examined the effect of hot-melt extrusion condition on the physical stability of the solid dispersion prepared using partially hydrolyzed polyvinyl alcohol (PVOH). The hot-melt extrusion of indomethacin (IMC) and PVOH mixed at the weight ratio of 3 : 7, 5 : 5 and 7 : 3 was performed either at 170 or 190°C to prepare the IMC/PVOH hot-melt extrudate (HME). Differential scanning calorimetry represented that IMC was mixed with PVOH on a scale of several tens of nanometer in all the HMEs with different weight ratio. ¹³C solid-state NMR measurement revealed that an intermolecular interaction was formed between a carboxylic group of IMC and a hydroxy group of PVOH in the HMEs. The intermolecular interaction in the HMEs was stronger at the higher extrusion temperature. At the low IMC loading, the IMC molecules could be mixed with the amorphous PVOH at the molecular level, and the remained PVOH without interaction formed the crystal phase. On the other hand, at the high IMC loading, most PVOH could be amorphized by the interaction with IMC, and the excess IMC which did not interact with PVOH formed the IMC-rich domain. The IMC/PVOH HME at the weight ratio of 7 : 3 extruded at higher extrusion temperature showed higher physical stability of amorphous IMC compared with that extruded at lower extrusion temperature. The hot-melt extrusion process at higher temperature provided the rapid melting of PVOH crystal phase, resulted in the homogeneous mixing with IMC and the formation of stronger intermolecular interaction.

Cancer-Type OATP1B3 mRNA in Extracellular Vesicles as a Promising Candidate for a Serum-Based Colorectal Cancer Biomarker

Cancer-type organic anion transporting polypeptide 1B3 (Ct-OATP1B3) mRNA is a variant isoform of the liver-type OATP1B3. Because Ct-OATP1B3 mRNA shows an excellent cancer-specific expression profile in colorectal cancer (CRC), and that its expression levels are associated with CRC prognosis, it holds the potential to become a useful CRC detection and diagnosis biomarker. While the potential is currently justified only at the tissue level, if existence of Ct-OATP1B3 mRNA in CRC-derived extracellular vesicles (EVs) is validated, the findings could enhance its translational potential as a CRC detection and diagnosis biomarker. Therefore, this study aims at proving that Ct-OATP1B3 mRNA exists in CRC-derived EVs, and can be detected using serum specimens. To examine the possibility of Ct-OATP1B3 mRNA being existed in extracellular milieu, we isolated EVs from the human CRC (HCT116, HT-29, and SW480) cell lines, and prepared their cDNAs. The RT-PCR results showed that Ct-OATP1B3 mRNA was clearly present in EVs derived from the human CRC cell lines. Then, in order to further explore the possibility that Ct-OATP1B3 mRNA in CRC-derived EVs can be detected in serum, we isolated serum EVs derived from human CRC xenograft mice, and then performed RT-PCR. The results showed that Ct-OATP1B3 mRNA could be found in all serum EV and CRC tissue samples of the mice examined. Collectively, our findings, which show that Ct-OATP1B3 mRNA exists in EVs and can be detected in (at least) mouse serum, strengthen the potential use of Ct-OATP1B3 mRNA as a serum-based CRC biomarker.

Microbes Culture System Using Cellulose Tubes and Photocatalyst-Coated Glass Balls

Currently, microbes are utilized in many fields, such as medicine, food and environment etc. For more application of microbes, we need a new culture system, which can culture target microbes in large quantities at low cost. Thereupon, we propose a culture system using cellulose tubes. Target microbes are encapsulated inside the cellulose tubes, where they acquire nutrients and oxygen through nano pores of the tubes and are protected from competitive microbes even in open environment. To further increase the amount of oxygen and nutritions available for the target microbes, we propose photocatalyst-coated glass balls (PCGB) to sterilize competing microbes outside the tubes. We experimentally verified the effectiveness of the proposed culture system by culturing Coryne gultamicum as the target microbes.