Preparation of chitosan-coated hollow tin dioxide nanoparticles and their application in improving the oral bioavailability of febuxostat

The aim of this study was to design a chitosan-coated hollow tin dioxide nanosphere (CS-HSn) for loading febuxostat (FEB) using an adsorption method to obtain a sustained-release system (CS-HSn-FEB) to improve the oral bioavailability of FEB. The morphological characteristics of hollow tin dioxide nanospheres (HSn) and CS-HSn were analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The hemolysis test and CCK-8 test were used to assess the biosafety of HSn and CS-HSn. Powder X-ray diffraction (PXRD) and differential scanning thermal analysis (DSC) were performed on CS-HSn-FEB to analyze the drug presence status. The dissolution behavior and changes in plasma drug concentration of CS-HSn-FEB were evaluated in vitro and in vivo. Sections of intestinal tissues from SD rats were obtained to observe whether chitosan could increase the distribution of nanoparticles in the intestinal tissues. The results showed that FEB was present in CS-HSn in an amorphous state. Moreover, CS-HSn, with good biosafety, significantly improved the water solubility and oral absorption of FEB, indicating that CS-HSn has great potential to improve the intestinal absorption and oral bioavailability of insoluble drugs.

Antifungal nanosuspensions with surfactants and silver for the treatment of onychomycosis

Fungal nail infection (Onychomycosis) often requires prolonged treatment and is associated with a high risk of resistance to treatment. Here in this contribution, we introduce a novel approach to enhance penetration and antifungal activity of the antifungal drug griseofulvin (GF). Solid dispersions were prepared with hydroxypropyl methylcellulose acetate succinate (HPMCAS) and combined with surfactant (either sodium dodecyl sulphate (SDS), dodecyl trimethylammonium bromide (DTAB), or Pluronic F127) using mechanochemical activation. The prepared powders were then suspended with spray-dried silica-coated silver nanoparticles and applied onto infected bovine hooves to assess permeability and antifungal activity. The results showed that the prepared nanosuspensions significantly suppressed fungal activity causing disruption of fungal biofilms. Raman mapping showed enhanced permeation while dynamic vapor sorption (DVS), and particle size measurements showed varied effects depending on the type of surfactant and milling conditions. The prepared nanosuspensions displayed enhanced solubility of the poorly soluble drug reaching approximately 1.2 mg/mL. The results showed that the dispersions that contained DTAB displayed maximum efficacy while the inclusion of colloidal silver did not seem to significantly improve the antifungal activity compared to other formulations.

In situ determination of the saturation solubility of nanocrystals of poorly soluble drugs for dermal application

The aim of this study was to determine, in situ, the saturation solubility and dissolution rate of nanocrystals of three poorly water-soluble drugs for dermal application. The nanocrystals were prepared by wet bead milling. Their size could be controlled by various process parameters. The saturation solubility was measured in water or in the presence of surfactant at 32°C with a Sirius^® inForm based on in situ UV-vis spectroscopy. The saturation solubility of nanocrystals with sizes of ∼300nm increased for each drug in comparison to non-milled drug powders, with factors of increase in the range 1.3-2.8. The tacrolimus solubility was further analyzed with excess nanocrystal amounts four and ten times higher than the drug powder solubility. The corresponding solubility increases were 2.8 and 6.6 and thus dependent on the amount of excess nanocrystals. The higher increase was due to the presence of a larger fraction of small size particles, and only crystals far below 1μm showed supersaturation. The solubility increase for nanocrystals determined in situ was remarkably lower than the one previously reported with the use of non in situ methods. Nanomilling increased the drug dissolution rates: the highest increase was obtained with ibuprofen (rate increase ∼30).

Preparation and tableting of long-term stable amorphous rutin using porous silica

Amorphous state of drugs increases the oral bioavailability, but typically faces physical stability problems. Amorphous rutin was generated and physically stabilized by encapsulating inside mesopores of porous AEROPERL® 300 Pharma and named as rutin CapsMorph® in this study. AEROPERL® 300 Pharma was loaded with rutin dissolved in DMSO containing Tween 80, and subsequently the solvent evaporated (wetness impregnation method). The loading process was monitored by light microscopy and scanning electron microscopy (SEM). X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to confirm the amorphous state in AEROPERL® 300 Pharma. A loading of 20% of the rutin-AEROPERL® 300 Pharma mixture was obtained. The amorphous state proved to be stable over 2years of storage at room temperature. Due to the amorphous state and the nanosize of the rutin in the mesopores, the kinetic saturation solubility increased to about 4mg/ml (water, 0.1MHCl, pH 6.8PBS) compared to the maximum observed thermodynamic equilibrium solubility of rutin raw drug powder of only 74.48±1.42μg/ml in pH 6.8PBS (=increase by factor about 54). The dissolution velocity also increased distinctly, e.g. about 96.1% of rutin dissolution from CapsMorph® powder in water within 5min compared to less than 40% of raw drug powder after 3h. Tablets were produced with rutin CapsMorph®, raw drug powder and their dissolution velocity compared to a marketed product. About 83.0-95.6% were released from the rutin CapsMorph® tablet within 5min, compared to 42.7-52.5% from the marketed tablet after 3h (water, 0.1MHCl, pH 6.8PBS). After dissolution the supersaturation level of rutin CapsMorph® remained over about 2h, then solubility slowly reduced, but remained after 48h still multifold above the thermodynamic rutin solubility. This should be sufficient for many poorly soluble drugs to achieve a sufficient bioavailability. For optimal exploitation of the supersaturation, a multiple step release system could be used, e.g. release of CapsMorph® particles every 2-3h.

Formulation of dried lignans nanosuspension with high redispersibility to enhance stability, dissolution, and oral bioavailability

Herpetospermum caudigerum lignans (HTL), one of the potential drugs with anti-hepatitis B virus and hepatoprotective effects, has limited clinical applications because of poor aqueous solubility and low bioavailability. Both herpetrione (HPE) and herpetin (HPN) are the most abundant ingredients in HTL and exhibit weak acidity. The purpose of the present study was to produce dried preparations of HTL (composed of HPE and HPN) nanosuspensions (HTL-NS) with high redispersibility using lyophilization technology. The HTL-NS was prepared by utilizing precipitation-combined homogenization technology based on acid-base neutralization reactions, and critical formulation and process parameters affecting the characteristics of HTL-NS were optimized. The resultant products were characterized by particle size analysis, SEM, XRD, stability, solubility, dissolution and in vivo bioavailability. HTL-NS showed near-spherical-shaped morphology and the size was 243 nm with a narrow PDI value of 0.187. The dried preparations with a relatively large particle size of 286 nm and a PDI of 0.215 were achieved by using 4% (W/V) mannitol as cryoprotectants, and had a better stability at 4 or 25 °C for 2 months, compared to HTL-NS. In the in vitro test, the dried preparations showed markedly increased solubility and dissolution velocity. Besides, in the in vivo evaluation, it exhibited significant increases in AUC_0-t, C_max,MRT and a decrease in T_max, compared to the raw drug. In conclusion, our results provide a basis for the development of a drug delivery system for poorly water-soluble ingredients with pH-dependent solubility.

CapsMorph® technology for oral delivery--theory, preparation and characterization

The CapsMorph(®) technology prepares amorphous drugs for oral delivery by encapsulating them into porous materials. Hesperidin as model compound was loaded onto AEROPERL(®) 300 Pharma using the wetness impregnation method. Hesperidin was dissolved in dimethyl sulfoxide (DMSO) and alternatively in DMSO with addition of Tween 80. The drug solutions were added dropwise to the porous material and subsequently DMSO was evaporated. The AEROPERL(®) 300 Pharma could be loaded with about 30% hesperidin in the amorphous form. Amorphous state was verified by X-ray diffraction and differential scanning calorimetry. The CapsMorph(®) formulation was compared regarding properties determining oral bioavailability, i.e., kinetic saturation solubility and dissolution rate to raw drug powder and hesperidin nanocrystals. The saturation solubility of CapsMorph(®) without Tween 80 was 654 μg/ml, which is 36-fold higher than the raw drug powder (18 μg/ml) and about 20 times higher than nanocrystals (30 μg/ml). In vitro release was faster (100% in 10 min at pH 6.8) compared to dissolution of nanocrystals with about 15%. Addition of Tween 80 to CapsMorph(®) lowered the solubility (168 μg/ml) and slowed down the release, but provided longer times of supersaturation without precipitation of drug. Based on these data, it appears that drug loaded porous materials provide better formulations compared to nanocrystals for poorly soluble drugs.

Dissolution enhancement and in vitro performance of clarithromycin nanocrystals produced by precipitation-lyophilization-homogenization method

The gastroduodenal diseases caused by Helicobacter pylori were commonly treated with antibiotic clarithromycin as a standard regimen. According to the poorly water-soluble of clarithromycin, the nanocrystal formulation was prepared. The aim of this study was to investigate an enhancement effect of clarithromycin nanocrystals produced by precipitation-lyophilization-homogenization (PLH) method on the saturation solubility, dissolution velocity, antibiotic activity, permeability through the gastric mucus and cellular permeability. Poloxamer 407 and sodium lauryl sulfate (SLS) were chosen as combined stabilizers in the nanocrystal system. The obtained clarithromycin nanocrystals were identified as cubic particles by SEM with a bulk population of approximately 400nm existed in crystalline and/or partial amorphous form as investigated by DSC and XRPD. The saturation solubility of the clarithromycin nanocrystals was increased by 1.5- and 6-folds higher than clarithromycin powder in buffer pH 5.0 and 6.8, respectively. The dissolution profiles of clarithromycin nanocrystals at pH 5.0 and 6.8 were significantly different from clarithromycin powder and the marketed product (f1 value >15 and f2 value <50). All dissolution parameters (relative dissolution rate, percent dissolution efficiency and mean dissolution time) showed that clarithromycin nanocrystals had higher dissolution rate when compared with the clarithromycin powder, the lyophilized coarse suspension and the marketed product. The bioassay study by diffusion agar method showed a maintained antibiotic activity of clarithromycin nanocrystals solubilized in buffer solution which was greater potency than the lyophilized coarse suspension and the clarithromycin powder. Additionally, the nanocrystals possessed higher permeability through gastric mucus and cellular monolayer of Caco-2 and NCI-N87 cells as compared to the lyophilized coarse suspension and the clarithromycin powder. The results indicated that, the developed clarithromycin nanocrystals were a potential delivery system that exerts more effectiveness in H. pylori eradication.

Enhanced antihypertensive activity of candesartan cilexetil nanosuspension: formulation, characterization and pharmacodynamic study

The objective of the present investigation was to enhance the oral bioavailability of practically insoluble Candesartan cilexetil [CC] by preparing nanosuspension. The nanosuspension was prepared by media milling using zirconium oxide beads and converted to solid state by spray drying. The spray dried nanosuspension of CC [SDCN] was evaluated for particle size, zeta potential, saturation solubility, crystallanity, surface morphology and dissolution behavior. SDCN showed particle size of 223.5±5.4 nm and zeta potential of −32.2±0.6 mV while saturation solubility of bulk CC and SDCN were 125±6.9 μg/ml and 2805±29.5 μg/ml respectively, showing more than 20 times increase in solubility. Differential Scanning Calorimetry [DSC] and X-ray diffraction [XRD] analysis showed that crystalline state of CC remained unchanged in SDCN. Dissolution studies in phosphate buffer pH 6.5 containing 0.7% Tween 20 showed that 53±5% of bulk drug dissolved in 15 min whereas SDCN was almost completely dissolved exhibiting higher dissolution velocity and solubility. Transmission electron microscopy [TEM] revealed that nanocrystals were not of uniform size, and approximately of oval shape. Pharmacodynamic study based on deoxycorticosterone acetate [DOCA] salt model was performed in rats to evaluate in-vivo performance, which showed 26.75±0.33% decrease in systolic blood pressure for nanosuspension while plain drug suspension showed 16.0±0.38% reduction, indicating that increase in dissolution velocity and saturation solubility leads to enhancement of bioavailability of SDCN when compared to bulk CC suspension. Thus, the results conclusively demonstrated a significant enhancement in antihypertensive activity of candesartan when formulated as nanosuspension.