Development of a novel starch with a three-dimensional ordered macroporous structure for improving the dissolution rate of felodipine

Materials Science and Engineering C 58 (2016) 1131–1137

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Development of a novel starch with a three-dimensional ordered macroporous structure for improving the dissolution rate of felodipine Yanna Hao, Chao Wu ⁎, Zongzhe Zhao, Ying Zhao, Jie Xu, Yang Qiu, Jie Jiang, Tong Yu, Chunyu Ma, Buyun Zhou Pharmacy School, Liaoning Medical University, 40 Songpo Road, Linghe District, Jinzhou, Liaoning Province 121000, China

a r t i c l e

i n f o

Article history: Received 30 June 2015 Received in revised form 12 August 2015 Accepted 2 September 2015 Available online 7 September 2015 Keywords: Starch Three-dimensional ordered macroporous Felodipine Insoluble drug The dissolution rate Relative bioavailability

a b s t r a c t In this study, silica nanospheres with different particle sizes were used as hard template for synthesis of a starch with a novel three-dimensional ordered macroporous structure (3DOMTS). As a pharmaceutical adjuvant, 3DOMTS was used to improve the dissolution rate and oral relative bioavailability of water-insoluble drugs. Felodipine (FDP) was chosen as a model drug and was loaded into the 3DOMTS by solvent evaporation. FDP loading into 3DOMTS with different pore sizes was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimeter (DSC), powder X-ray diffractometer (PXRD) and Fourier-Transform Infrared (FTIR). The results obtained showed that FDP was present in the pores in an amorphic or microcrystalline state. The in vitro dissolution results showed that 3DOMTS could effectively improve the dissolution rate of FDP in comparison with commercial common tablets. Pharmacokinetic results indicated that the oral relative bioavailability of self-made FDP–3DOMTS tablets were 184%, showing that 3DOMTS produced a significantly increased oral absorption of FDP. In conclusion, 3DOMTS exhibits the dual potential of improving the dissolution rate of poorly water soluble drugs and the novel filler produced by direct compression technology confirming that 3DOMTS will be useful for many applications in the field of pharmaceutics. © 2015 Elsevier B.V. All rights reserved.

1. Introduction It is well known that many new compounds with good biological activity have limited clinical applications due to a number of disadvantages. Poor water solubility is one of the most important of these [1–3], especially drugs belonging to the Biopharmaceutics Classification System Class II (BCSII). This is a key factor which limits drug absorption and oral bioavailability. Following oral administration, drugs are initially dissolved in the gastrointestinal tract and then absorbed into the body. BCSII drugs have good biological membrane permeability and, therefore, the absorption and bioavailability of these drugs would be increased if the problem of poor solubility could be solved. This is an enormous challenge for all pharmaceutical researchers who need to find suitable methods to improve the dissolution rate of poorly soluble drugs [4]. In recent past decades, many studies have been carried out to solve this problem. Sharma used a solid dispersion to increase the solubility of water-insoluble drugs [5] while Meiyan Yang used pH-modified solid dispersions to increase the dissolution rate of a poorly watersoluble weakly basic drug, GT0918 [6]. Habib Ali designed liposomes for the solubilization of poorly water soluble drugs [7]. Micronization of insulin by high pressure homogenization, not only increased its bioavailability but also maintained the stability and biological activity of insulin [8]. In recent years, an increased number of researchers had ⁎ Corresponding author. E-mail address: [email protected] (C. Wu).

http://dx.doi.org/10.1016/j.msec.2015.09.018 0928-4931/© 2015 Elsevier B.V. All rights reserved.

focused on using nanomaterials to improve the dissolution rate of insoluble drugs [9–15], such as mesoporous silica nanomaterials [16–21] and carbon nanomaterials [22–24]. However, inorganic materials have unpredictable biological safety and are not very biodegradable [25–28]. Shi has reported that intravenous and intraperitoneal injection of mesoporous silica particles had toxic effects, while subcutaneous injection did not produce any significant toxicity at the same dose [29]. This limits the clinical application of some dosage forms and, therefore, it is necessary to develop a novel safe and biodegradable material. In the study, we suggested that starch can be used as a natural matrix material constructed with a three-dimensional ordered macroporous structure for overcoming the problems associated with inorganic nanoporous materials. Felodipine (FDP) classified as a BCSII compound was selected as a model drug. The drug is a selective calcium antagonist, which inhibits the calcium flow of arterial smooth muscle extracellular calcium, as well as selective expansion of the small arteries, with no effect on veins, and does not cause orthostatic hypotension, or produce any significant inhibitory effect on the myocardial system. In order to improve the oral relative bioavailability of FDP, we prepared FDP–3DOMTS tablets and studied their in vitro dissolution and pharmacokinetics compared with the commercially available conventional tablets. The experimental results obtained showed that the self-made FDP–3DOMTS tablets had a higher relative bioavailability. Therefore, the 3DOMTS appears to be a very promising material as a novel safe and biodegradable organic nanoporous carrier for improving the solubility and relative bioavailability of poorly soluble drugs.

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2. Materials and methods 2.1. Materials Soluble starch was obtained from Tianjin Guangfu Fine Chemical Research Institute Co., Ltd. (Tianjin, China). FDP with a purity N99% was provided by Wuhan Da hua wei ye Pharmaceutical Chemical Co., Ltd. (Wuhan, China). Commercial common Felodipine tablets provided by Beijing Union Pharmaceuticals (active pharmaceutical ingredient (API) was 5 mg). KCl, ethanol, chloroform, ammonia and hydrofluoric acid (HF) were provided by Tianjin Yong Sheng Fine Chemical Co., Ltd. (Tianjin, China) and all the chemicals used in this study were analytical/chromatographic grade. 2.2. Preparation of 3DOMTS The novel starch materials (3DOMTS) was synthesized using silica nanospheres as the hard template. The silica nanospheres were closely stacked and then starch solution was used to fill to the gap between the spheres. After removal of the silica nanospheres, a three-dimensional ordered macroporous structure with spherical pores was obtained. The specific steps were as follows: Step 1: 180 ml ethanol, and 65 ml deionized water were placed in a 500 ml glass container, and then 4.5 ml ammonia and 15 ml TEOS were added dropwise with stirring at room temperature. During the experiment, the amount of potassium chloride (KCl) and the dropping rate of TEOS had a direct impact on the size of the silica nanoparticles [30–32]. The silica nanospheres of 100 nm, 200 nm, 400 nm, 800 nm and 1000 nm corresponded to the concentrations of KCl 0 mol/m3, 0.5 mol/m3, 1 mol/m3, 5 mol/m3, 6 mol/m3 and the dropping rate of TEOS 0.24 mol/h, 0.08 mol/h, 0.04 mol/h, 0.024 mol/h, 0.008 mol/h respectively. After 4 h, the suspension was centrifuged, washed three times with alcohol and then washed three times with deionized water. The obtained samples with different size, as a hard template, were dried at 40 °C for 12 h in a vacuum oven (DZF6050, Shang hai boyuan, China). Step 2: 8 g of soluble starch was dissolved in 50 ml deionized water and then the solution was stirred at 100 °C in a water bath for 1 h. Then, 1 g of the silica nanospheres (100 nm) obtained in step 1 were dispersed in 50 ml deionized water and sonicated for 20 min. The starch solution and the dispersed silica nanosphere suspension were mixed and stirred for 2 h at 100 °C. After centrifugation at 7000 rpm/min, the mixture of silica nanospheres and starch gelled at 4 °C. The gel mixture was dried in a vacuum oven at 35 °C for 12 h, and then soaked in 10% hydrofluoric acid to remove the template. After washing three times with ethanol and drying under vacuum, 3DOMTS with 100 nm pore size were obtained. By changing the concentration of soluble starch and the sizes of templates, we could get the 3DOMTS with different pore sizes (200 nm, 400 nm, 800 nm and 1000 nm). 2.3. Drug loading FDP was incorporated into 3DOMTS (with different pore sizes) by solvent evaporation. For this, FDP was completely dissolved in chloroform and different ratios of 3DOMTS were added to the FDP solution. The mixtures were stirred for 4 h in a sealed and dark environment to prevent FDP decomposition in the drug loading process. After complete evaporation of the solvent at room temperature for 12 h, the FDP–3DOMTS (1:1, 1:3 and 1:5) were obtained. Finally, the samples were stored in a vacuum oven to protect them from the solvent residue. 2.4. Characterization of FDP–3DOMTS 2.4.1. Scanning electron microscopy (SEM) The surface topography of FDP–3DOMTS was examined by SEM (JEOL JSM-7001F, operated at 20 kV). Prior to examination, the powder

samples were dried and dispersed on double-sided adhesive tape with conductivity, and then sputtered with a thin layer of gold under vacuum. 2.4.2. Transmission electron microscopy (TEM) The fine detail of the macroporous structure was obtained by TEM (Tecnai G2F30, FEI, USA, operated at 200 kV). Prior to examination, the dried samples were put into ethanol solution and dispersed under ultrasound, and then the suspension was dropped into the copper net. After drying, the samples were observed by TEM. The average size of silica nanospheres was obtained by TEM. We randomly selected 30 particles from a TEM photographs and calculated their average particle size. 2.4.3. Solid state characterization by differential scanning calorimeter (DSC) and powder X-ray diffractometer (PXRD) A differential scanning calorimeter (DSC-60, Shimadzu, Inc. Japan) was used to record the changes in crystallinity or phase transition temperature of the crystalline drug. So, DSC could be used to identify the solid state of FDP in 3DOMTS. The instrument was calibrated with standard indium, the samples were continuously heated from 50 °C to 300 °C at a rate of 10 °C/min and the system was maintained in an inert state under a constant nitrogen flow at a rate of 150 ml/min. A powder X-ray diffractometer (PXRD, Rigaku Denki, Japan) was used to examine in detail the changes of FDP crystallinity in 3DOMTS. Samples were irradiated with Cu–Kα radiation under 30 kV and 30 mA. The step size was 0.02°, the scan speed was 4°/min and the range (2θ) was from 3° to 60°. 2.4.4. Fourier-transform infrared spectroscopy (FT-IR spectroscopy) An FT-IR spectrometer (Bruker IFS 55, Switzerland) was used to obtain FT-IR spectra over the range 4000 to 400 cm−1 using KBr tablets. Samples were milled and mixed with 100-fold amount of dried KBr in an agate mortar. KBr tablets were prepared with a compression force of 20 MPa using a 13-mm-diameter round flat face punch. The laboratory temperature was controlled at 15–30 °C and the relative humidity should be less than 65%. Before the sample was detected, we have already detected potassium bromide tablet in order to avoid interference absorption. 2.5. Preparation of FDP tablets FDP tablets were prepared by powder direct compression technology. First of all, we should precisely weight the drugs and adjuvant according to prescription. Then, the powders were mixed with a mortar and passed through an 80-mesh sieve. By controlling the amount of different adjuvant and pressure to control the qualities of the tablets, for example, the amount of adhesives could influence the hardness of the tablets and the rate of drug release. Through regulating each of the factors, finally, the FDP–3DOMTS tablets were obtained using a TDP single punch tabletting machine (TDP-1.5, Shanghai Wangqun, China). The hardness was measured by the Shore hardness (provided by the Dongguan fast Measuring Instruments Ltd.). And we also measured the friability and disintegration time of the tablets. Tablet friability tester was provided by Shanghai Double Asahi Electronics Co., Ltd. 2.6. In vitro dissolution of FDP–3DOMTS powder samples The dissolution testing was carried out using the USP II paddle method with a dissolution instrument (ZRS-8G, Tianjin Xintianguang, China). The drug dissolution medium consisted of 500 ml water and 2% w/v sodium dodecyl sulfate (SDS) (Chinese Pharmacopeia). The dissolution condition was maintained at (37 ± 0.5) °C with a paddle speed of (100 ± 1) rpm/min. Accurately weighed samples of FDP–3DOMTS, equivalent to 5 mg raw FDP, were added to the dissolution medium at the start and then 5 ml samples were collected after 5, 10, 15, 20, 30, 45 and 60 min and passed through a 0.45 μm microporous membrane

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Fig. 1. The SEM micrographs of 3-DOMTS with different pore size (A - 100 nm, B - 200 nm, C - 400 nm, D - 800 nm, E - 1000 nm).

filter. Each time a similar amount of fresh medium was added to the dissolution medium to maintain a constant volume. The drug concentrations were measured by UV spectroscopy (UV-2000, Unico, USA) at a wavelength of 237 nm. All experiments with FDP were carried out in the dark to prevent light-induced degradation of FDP and all measurements were carried out in triplicate. 2.7. In vivo pharmacokinetic study 2.7.1. Animals and dosing The protocol of the animal experimental study was approved by the Liaoning Medical University Laboratory Animal Ethics Committee. All experimental procedures carried out in this study were performed in accordance with the Guidelines on the care and use of animals for scientific purposes [33]. The pharmacokinetics of FDP–3DOMTS tablets and commercial FDP tablets were studied using rabbits provided by the Liaoning Medical University Laboratory Animal Center. Twelve rabbits (2.5–3.0 kg) were randomly assigned to two groups and fasted for 12 h before dosing. One group was given commercial common FDP tablets and the other group was given self-made FDP–3DOMTS tablets (3 mg/kg). The self-made FDP–3DOMTS tablets and commercial common FDP tablets were used for rabbits in order to prove that 3DOMTS obviously enhances oral relative bioavailability of FDP [34]. The tablets were given by oral gavage, that was to say, the whole tablets were poured into the stomach of the rabbit, then a small amount of water was given. All rabbits had free access to water throughout the experiment. Blood samples (3.0 ml) were withdrawn from the ear vein at 5 min, 15 min, 30 min, 45 min, 60 min, 1.5 h, 2 h, 3 h, 4 h, 6 h, 8 h, 10 h, 12 h and 24 h after dosing and placed in heparinized tubes, and then centrifuged at 4250 × g for 10 min using a high-speed centrifuge (TG22-WS,Shanghai Danding, China). The obtained plasma samples were stored at −20 °C. 2.7.2. Determination of FDP in plasma FDP plasma concentrations were determined by HPLC (L-2400, HITACHI, Japan) with a UV–vis detector. A Welch C18 column (4.6 mm × 200 mm, 5 μm) was used for analysis. The mobile phase was a mixture of acetonitrile and water (60:40, v/v) and detection was carried out at 25 °C with a flow rate of 1 ml/min. Nitrendipine was selected as the internal standard and UV detection was performed at 236 nm. The retention time of nitrendipine and FDP was 8.01 min

and 12.98 min, respectively. Plasma samples (1 ml) were transferred to 10 ml centrifuge tubes, followed by 20 μl internal standard solution (1 mg/ml), 3 ml sodium hydroxide solution (1 mol/l) and 5 ml ethyl acetate. The solutions were vortexed for 10 min then each sample was centrifuged at 4250 ×g for 10 min and the organic layer was transferred to another tube and evaporated to dryness at 40 °C using a high-speed centrifuge (LNG-T120, Hualida, China). The residue was dissolved in 50 μl mobile phase. After centrifugation at 12,750 ×g for 10 min, 20 μl samples of the supernatant were subjected to HPLC analysis. 2.7.3. Data analysis All the pharmacokinetic data on FDP were analyzed using DAS 2.0 software. Several pharmacokinetic parameters, including the maximum peak concentration of the drug in plasma (Cmax), the time to reach the maximum concentration (Tmax) and the area under the curve (AUC), were obtained directly from the recorded results. 3. Results and discussion 3.1. Preparation and characterization of 3DOMTS carrier During the preparation of organic porous materials, shrinkage and collapse of the framework structure is an inevitable problem. Some researchers used supercritical fluid methods to overcome it [35,36]. Because it was time-consuming and costly, we urgently need a simple method. We found that dry starch gel had enough rigidity to maintain the nanoporous structure [37–39]. In the present study, 3DOMTS was produced by the hard template method. A major advantage of this approach was that the pore size of the 3DOMTS could be accurately controlled by adjusting the size of the template (silica nanospheres). We prepared different sizes of silica nanospheres by controlling the drip rate of TEOS and adding a selected amount of electrolyte (KCl) [30–32]. The average size and morphology of the silica nanospheres were examined by TEM. The obtained well-arranged threedimensional silica sphere arrays could be used as templates for the production of 3DOMTS. SEM micrographs (Fig. 1) clearly showed 3DOMTS with different pore sizes (A — 100 nm, B — 200 nm, C — 400 nm, D — 800 nm, E — 1000 nm). The three-dimensional structure of 3DOMTS did not shrink and collapse. Because starch is a natural, cheap, safe and biodegradable material, it is perfect as a carrier for improving the

Fig. 2. The SEM micrographs of raw FDP (2A) and FDP–3DOMTS samples (1:1 — 2B, 1:3 — 2C and 1:5 — 2D).

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dissolution rate of poorly water soluble drugs compared with other inorganic three-dimensional ordered macroporous materials [40–42]. 3.2. Drug incorporation into 3DOMTS Solvent evaporation was used to load FDP into 3DOMTS with different pore sizes. The three-dimensional ordered macroporous structure effectively inhibits the crystallization of water insoluble drugs due to the space limiting effect of the nanoscale pores. As shown in Fig. 2A, crude FDP powder was found to be irregular-shaped particles with a relatively wide particle size distribution (mean particle size of several micrometers). However, after incorporation into 3DOMTS, large crystals of FDP disappeared and the pores of 3DOMTS were filled, suggesting that the entrapment of FDP into 3DOMTS was successful. Specially, traces of drug crystals could be observed on the surface of FDP– 3DOMTS samples (1:1), which might be due to that the drug amount exceeded the pore volume capacity of 3DOMTS. Furthermore, with the increase in the 3DOMTS amount, drug crystals on the outer surface became few and negligible, such as the FDP–3DOMTS at the ratio of 1:5 with highest 3DOMTS amount. Therefore, we concluded that sufficient 3DOMTS amount was a prerequisite for the fine dispersion and complete incorporation of drugs. Compared with crystalline drugs, drugs in an amorphous or microcrystalline state usually exhibited a faster dissolution rate. We examined a series of drug–3DOMTS ratios (1:1, 1:3 and 1:5) in our preliminary experiment in order to find the most suitable ratio for obtaining FDP in an amorphous state which was directly

Fig. 4. DSC micrographs of pure FDP, 3DOMTS (100 nm), physical mixtures (PM) of FDP and 3DOMTS (at the ratio of 1:5) as well as FDP–3DOMTS samples at ratio of 1:1, 1:3, 1:5 (A); 3DOMTS with 100 nm, 200 nm, 400 nm, 800 nm and 1000 nm pore loaded FDP at a ratio of 1:5 (B).

related to the dissolution rate. It was found that FDP could be effectively loaded into 3DOMTS at a FDP–3DOMTS ratio of 1:5 and FDP was present in amorphous form, as supported by the DSC and PXRD results. 3.3. Solid state characterization by PXRD and DSC The crystalline nature of raw FDP, 3DOMTS (100 nm), physical mixtures (PM) of raw FDP and 3DOMTS as well as FDP–3DOMTS samples at a ratio of 1:1, 1:3 and 1:5 were evaluated by PXRD analysis. In Fig. 3A, the characteristic diffraction reflections of FDP was showed at a 2θ of

Fig. 3. PXRD profile of raw FDP, 3DOMTS (100 nm), physical mixtures (PM) of FDP and 3DOMTS (at the ratio of 1:5) as well as FDP–3DOMTS samples at ratio of 1:1, 1:3 and 1:5 (A); 3DOMTS with 100 nm, 200 nm, 400 nm, 800 nm and 1000 nm pore loaded FDP at a ratio of 1:5 (B).

Fig. 5. FT-IR spectra of raw FDP, 3DOMTS, FDP–3DOMTS (1:1, 1:3 and 1:5) and. physical mixtures (PM) of FDP and 3DOMTS (at the ratio of 1:5).

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Fig. 6. Dissolution profile of different ratios of FDP–3DOMTS powder samples and raw FDP (5A); dissolution profile of different nano-pore size 3DOMTS at the ratio of 1:5 (5B). The data represent the average results of three independent batches.

10°, and the intensity was markedly reduced with an increase in the proportion of 3DOMTS in comparison with raw FDP, 3DOMTS and PM. In FDP–3DOMTS samples at a ratio of 1:5, the absence of FDP crystal reflections was very obvious. This indicated that FDP was loaded into 3DOMTS pores and was present in a noncrystalline state. In order to explore the degree of inhibition of different apertures for drug crystallinity, 3DOMTS with 100 nm, 200 nm, 400 nm, 800 nm and 1000 nm poreloaded FDP at a ratio of 1:5 was used which showed that the degree of inhibition was significantly reduced with an increase in the aperture in Fig. 3B. 3DOMTS with 100 nm was able to maintain FDP in a noncrystalline state. When the aperture was larger than 100 nm, FDP was in a microcrystalline state. According to the Scherrer formula [43], the change in grain size at 2θ = 10° was 0 nm, 24.57 nm, 32.71 nm, 43.31 nm, and 59.23 nm corresponding to 100 nm, 200 nm, 400 nm, 800 nm and 1000 nm. Debye-Scherrer formula as follows: D = Kλ/ βcosθ. In the formula, K is Scherrer constant (typically 0.89), D is the grain size of perpendicular to the crystal plane direction, β is halfheight peak width the diffraction peak (rad), θ is Bragg diffraction angle, λ is the wavelength of the incident X-ray (Cuka wavelength 0.154056 nm). This also confirmed that the grain size gradually increased with the increase in pore size and the specific surface area of the FDP particles decreased, which is the main reason for the effect on the dissolution rate based on the Noyes-Whitney equation. To further confirm these results, DSC measurement was performed. As seen in Fig. 4A, the DSC curves of 3DOMTS did not exhibit an endothermic peak. FDP and PM produced a single sharp endothermic peak at 148 °C. The endothermic peak of FDP was reduced in FDP–3DOMTS samples at ratios of 1:1 and 1:3, showing that the FDP existed in a microcrystalline state. When FDP–3DOMTS samples were in a ratio of 1:5, FDP existed in an amorphous form. A high proportion of the FDP exceeded the maximum dispersion ability of 3DOMTS. Increasing the proportion of 3DOMTS could increase the dispersion of FDP at the same pore size. In Fig. 4B, FDP–3DOMTS samples corresponding to a 100 nm pore showed that FDP did not have endothermic peak at the same ratio, but other aperture samples (200 nm, 400 nm, 800 nm and 1000 nm) had an endothermic peak at 142 °C. This endothermic peak

gradually increased with an increase in aperture. The enthalpy change was − 5.32 J/g, − 18.59 J/g, − 22.12 J/g, − 27.94 J/g corresponding to 200 nm, 400 nm, 800 nm and 1000 nm. This indicated that the increase in the aperture reduced the drug dispersion and the space restriction effect of the nanopores was weakened, which was not helpful for improving the drug dissolution rate [44]. 3.4. FT-IR analysis The FT-IR spectra were used to identify possible chemical interactions between FDP and 3DOMTS. The FT-IR spectra of raw FDP, 3DOMTS, FDP–3DOMTS (1:1, 1:3 and 1:5) and physical mixtures (PM) of raw FDP and 3DOMTS are presented in Fig. 5. Raw FDP showed a characteristic peak νc_o at 1701 cm− 1. Typical features of FDP– 3DOMTS compared with the PM showed no new peaks or migration of the characteristic peak position. This demonstrated that there was no interaction between FDP and 3DOMTS. Moreover, 3DOMTS had hydroxyl stretching peaks at 3000–3500 cm−1, demonstrating that there was a hydrophilic surface which was easy wetted with water. The drug molecules in the pores were rapidly surrounded with water, which promoted drug dissolution. 3.5. In vitro dissolution of FDP–3DOMTS powder samples In the present work, the dissolution of FDP–3DOMTS with different drug-carrier ratios was determined and compared with that of raw FDP. As presented in Fig. 6A, FDP–3DOMTS exhibited a rapid release of 80% within 5 min in comparison with 30% within 45 min for raw FDP. With an increase in the proportion of 3DOMTS, the dissolution rate

Table 1 Compositions of self-made FDP–3DOMTS tablets.

Carrier Adjuvant

Ingredients

Formulation

FDP–3DOMTS Lactose PVP CMC-Na Magnesium stearate

45 mg 45 mg 2 mg 10 mg 2 mg

Fig. 7. Dissolution rate of self-made FDP–3DOMTS tablets and commercial common tablets. The data represent the average results of three independent batches.

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was a perfect substitute for starch used in the traditional compression method [45,46]. At the same time, compared with other inorganic nano porous materials, starch has several distinct advantages: (1) cheapness, nontoxicity, biocompatibility, biodegradability [47]; (2) due to the large number of hydroxyl groups on the surface of 3DOMTS, some functional groups can be easily grafted on to the surface of 3DOMTS; (3) soluble starch as the natural material can partially dissolve in water [48], which promotes the release of FDP dispersed in 3DOMTS pores. The advantage was obvious for all other fillers or adjuvants. 3.7. In vivo pharmacokinetics study

Fig. 8. The FDP plasma concentration–time curves of the self-made FDP–3DOMTS tablets and commercial common FDP tablets in rabbits (n = 6).

was increased. The dissolution of FDP–3DOMTS samples at a ratio of 1:5 was clearly faster than that of samples at a ratio of 1:1 and 1:3. Combined with the PXRD and DSC results, this further explained that the dissolution rate of amorphous FDP was higher than that of microcrystalline FDP at the same pore size. Fig. 6B shows the relationship between the dissolution rate and nano-pore size at the same ratio of FDP–3DOMTS. When the pore size of 3DOMTS was less than 400 nm, the dissolution rate gradually increased with the increase in pore size. The reason for this was that the increase in pore size reduced the diffusion resistance and accelerated the drug dissolution in spite of the drug particle size being increased. After the pore size reached 800 nm, the dissolution rate began to decline instead of increase. According to calculation results of X-ray grain size, it showed that the degree of crystallinity of drug increased with the increase of pore size. So, we can conclude that the increase in pore size can accelerate the drug dissolution in the nanoscale range and there is an upper limit. When the pore size was more than the upper limit, the drug dissolution rate was reduced. 3.6. Evaluation of self-made FDP–3DOMTS tablets There are three factors mainly affecting drug release from FDP– 3DOMTS: adhesives, disintegrants, and fillers. Therefore, we designed a three factors orthogonal experiment to study the effects of these factors on drug release behavior and obtain the optimum formulation (Table 1). As shown in Fig. 7, self-made FDP–3DOMTS tablets had a faster dissolution rate in comparison with commercial common FDP tablets. Approximately 90% of FDP within 5 min was released by selfmade FDP–3DOMTS tablets, while the corresponding figure for commercial common FDP tablets was 65%. It was found that the hardness of self-made FDP–3DOMTS tablets was 4.5 ± 0.243 kg/cm2. The friability was 0.83% ± 0.02 and there was no occurrence of fracture or crack when disintegration time was 10 min. The results were consistent with the tablet quality standard. In our study, we found that 3DOMTS had two functions. One function was as filler used for powder direct compression technology. The other function was as a carrier for improving the dissolution of a poorly soluble drug. 3DOMTS, as the novel filler,

The FDP plasma concentration–time curves of the self-made FDP– 3DOMTS tablets and commercial common FDP tablets in rabbits are presented in Fig. 8. The self-made FDP–3DOMTS tablets had a greater AUC, a higher peak concentration and a shorter half-life than the commercial common FDP tablets. The pharmacokinetic parameters using a noncompartmental analysis after the oral administration are listed in Table 2. The relative bioavailability of FDP after oral gavage of the selfmade FDP–3DOMTS tablets was 184%. This might be due to two factors. (i) FDP adsorbed into 3DOMTS pores was present in an amorphic or microcrystalline state. This meant that drug particles became smaller and the specific surface area dramatically increased [49], which would increase dissolution rate according to the Ostwald–Freundlich and Noyes–Whitney equations [50,51]. The relative bioavailability of FDP was closely related to the solubility. The dissolved FDP molecules are directly absorbed by enterocytes into the blood circulation. (ii) Smaller drug particles could be in close contact with biomembranes which help in the absorption and delivery of a drug. This study proved that 3DOMTS could effectively improve the dissolution rate and oral relative bioavailability of FDP. 4. Conclusion In this study, a biodegradable 3DOMTS was prepared successfully and its structure was determined by SEM and TEM. PXRD and DSC characterization showed that FDP was incorporated into 3DOMTS pores and was present in an amorphic or microcrystalline state. In vitro and in vivo drug release studies showed that 3DOMTS produced accelerated immediate release of FDP and increased its oral relative bioavailability in comparison with commercial common tablets. From these conclusions, this study demonstrated the significant application potential of 3DOMTS as a novel pharmaceutical adjuvant for poorly water-soluble drugs. It could be applied as an alternative to other fillers currently used for the powder direct compression technology of poorly water-soluble drugs in the BCS II category. This will allow its application as a nano material in the field of pharmaceutics. Acknowledgments This work was supported by the National Natural Science Foundation of China (no. 81302707), Natural Science Foundation of Liaoning Province (no. 2013022052), Principal Fund of Liaoning Medical University (no. AH2014020), Dr. Start-up Foundation of Liaoning Province (no.

Table 2 Pharmacokinetic parameters of FDP after oral administration of self-made FDP–3DOMTS tablets and commercial common FDP tablets.

Commercial common tablets FDP–3DOMTS tablets

Tmax(h)a

Cmax(ng/mL)b

AUC0-24(ng/mL*h)c

t1/2 (h)d

2.000 ± 0.2133 1.500 ± 0.1426

34.94 ± 18.83 88.06 ± 16.32

153.2 ± 24.78 281.8 ± 43.56

7.429 ± 2.281 2.459 ± 1.478

Each value represents the mean ± SD (n = 6). a Time to reach Cmax. b Maximum plasma concentration. c Area under the plasma concentration–time curve. d Elimination half-life.

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20141195) and the Construction of Clinical Cardiovascular System Drug Evaluation Research Technology platform (no.2012ZX09303016-002). References [1] D.P. Elder, R. Holm, H.L. Diego, Use of pharmaceutical salts and cocrystals to address the issue of poor solubility, Int. J. Pharm. 453 (2013) 88–100. [2] Y. Liu, C. Sun, Y. Hao, T. Jiang, L. Zheng, S. Wang, Mechanism of dissolution enhancement and bioavailability of poorly water celecoxib by preparing stable amorphous nanoparticles, J. Pharm. Pharm. Sci. 13 (2010) 589–606. [3] S. Stegemann, F. Leveiller, D. Franchi, H. de Jong, H. Linden, When poor solubility becomes an issue: from early stage to proof of concept, Eur. J. Pharm. Sci. 31 (2007) 249–261. [4] C.A. Lipinski, F. Lombardo, B.W. Dominy, P.J. Feeney, Experimental and computational approaches to estimate solubility and permeability in drug discovery and development settings, Adv. Drug Deliv. Rev. 64 (2012) 4–17. [5] A. Sharma, C. Jain, Solid dispersion: a promising technique to enhance solubility of poorly water soluble drug, Int. J. Drug Deliv. 3 (2011) 149–170. [6] M. Yang, S. He, Y. Fan, Y. Wang, Z. Ge, L. Shan, W. Gong, X. Huang, Y. Tong, C. Gao, Microenvironmental pH-modified solid dispersions to enhance the dissolution and bioavailability of poorly water-soluble weakly basic GT0918, a developing antiprostate cancer drug: preparation, characterization and evaluation in vivo, Int. J. Pharm. 475 (2014) 97–109. [7] M.H. Ali, B. Moghaddam, D.J. Kirby, A.R. Mohammed, Y. Perrie, The role of lipid geometry in designing liposomes for the solubilisation of poorly water soluble drugs, Int. J. Pharm. 453 (2013) 225–232. [8] A. Maschke, N. Calí, B. Appel, J. Kiermaier, T. Blunk, A. Göpferich, Micronization of insulin by high pressure homogenization, Pharm. Res. 23 (2006) 2220–2229. [9] N. Arunkumar, M. Deecaraman, C. Rani, Nanosuspension technology and its applications in drug delivery, Asian J. Pharm. 3 (2009) 168. [10] A. Bernkop-Schnurch, Nanocarrier systems for oral drug delivery: do we really need them? Eur. J. Pharm. Sci. 49 (2013) 272–277. [11] Y. Parajó, I. d'Angelo, A. Horváth, T. Vantus, K. György, A. Welle, M. Garcia-Fuentes, M.J. Alonso, PLGA: poloxamer blend micro-and nanoparticles as controlled release systems for synthetic proangiogenic factors, Eur. J. Pharm. Sci. 41 (2010) 644–649. [12] C.P. Reis, A.J. Ribeiro, S. Houng, F. Veiga, R.J. Neufeld, Nanoparticulate delivery system for insulin: design, characterization and in vitro/in vivo bioactivity, Eur. J. Pharm. Sci. 30 (2007) 392–397. [13] A. Sosnik, A.M. Carcaboso, R.J. Glisoni, M.A. Moretton, D.A. Chiappetta, New old challenges in tuberculosis: potentially effective nanotechnologies in drug delivery, Adv. Drug Deliv. Rev. 62 (2010) 547–559. [14] H. Valo, S. Arola, P. Laaksonen, M. Torkkeli, L. Peltonen, M.B. Linder, R., kuga, S., hirvonen, J., laaksonen, T., drug release from nanoparticles embedded in four different nanofibrillar celluloe aerogels, Eur. J. Pharm. Sci. 50 (2013) 69–77. [15] L. Yan, X. Chen, 7-Nanomaterials for Drug Delivery, in: S.-C. Tjong (Ed.), Nanocrystalline Materials, Second EditionOxford, Elsevier 2014, pp. 221–268. [16] J. Lu, Z. Li, J.I. Zink, F. Tamanoi, In vivo tumor suppression efficacy of mesoporous silica nanoparticles-based drug-delivery system: enhanced efficacy by folate modification, Nanomedicine 8 (2012) 212–220. [17] I.I. Slowing, J.L. Vivero-Escoto, C.W. Wu, V.S. Lin, Mesoporous silica nanoparticles as controlled release drug delivery and gene transfection carriers, Adv. Drug Deliv. Rev. 60 (2008) 1278–1288. [18] M. Vallet-Regi, M. Colilla, B. Gonzalez, Medical applications of organic–inorganic hybrid materials within the field of silica-based bioceramics, Chem. Soc. Rev. 40 (2011) 596–607. [19] S. Wang, Ordered mesoporous materials for drug delivery, Microporous Mesoporous Mater. 117 (2009) 1–9. [20] C. Wu, Z. Zhao, Y. Zhao, Y. Hao, Y. Liu, C. Liu, Preparation of a push-pull osmotic pump of felodipine solubilized by mesoporous silica nanoparticles with a core–shell structure, Int. J. Pharm. 475 (2014) 298–305. [21] Y. Zhang, Z. Wang, W. Zhou, G. Min, M. Lang, Cationic poly(ɛ-caprolactone) surface functionalized mesoporous silica nanoparticles and their application in drug delivery, Appl. Surf. Sci. 276 (2013) 769–775. [22] J. Guo, H. Zhang, H. Geng, X. Mi, G. Ding, Z. Jiao, Efficient one-pot synthesis of peapod-like hollow carbon nanomaterials for utrahigh drug loading capacity, J. Colloid Interface Sci. 437C (2014) 90–96. [23] T. Liu, L. Li, X. Teng, X. Huang, H. Liu, D. Chen, J. Ren, J. He, F. Tang, Single and repeated dose toxicity of mesoporous hollow silica nanoparticles in intravenously exposed mice, Biomaterials 32 (2011) 1657–1668. [24] P. Zhao, L. Wang, C. Sun, T. Jiang, J. Zhang, Q. Zhang, J. Sun, Y. Deng, S. Wang, Uniform mesoporous carbon as a carrier for poorly water soluble drug and its cytotoxicity study, Eur. J. Pharm. Biopharm. 80 (2012) 535–543. [25] A.J. Di Pasqua, K.K. Sharma, Y.L. Shi, B.B. Toms, W. Ouellette, J.C. Dabrowiak, T. Asefa, Cytotoxicity of mesoporous silica nanomaterials, J. Inorg. Biochem. 102 (2008) 1416–1423.

1137

[26] H. Haniu, Y. Matsuda, Y. Usui, K. Aoki, M. Shimizu, N. Ogihara, K. Hara, M. Okamoto, S. Takanashi, N. Ishigaki, K. Nakamura, H. Kato, N. Saito, Toxicoproteomic evaluation of carbon nanomaterials in vitro, J. Proteome 74 (2011) 2703–2712. [27] A. Kunzmann, B. Andersson, T. Thurnherr, H. Krug, A. Scheynius, B. Fadeel, Toxicology of engineered nanomaterials: focus on biocompatibility, biodistribution and biodegradation, Biochim. Biophys. Acta Gen. Subj. 1810 (2011) 361–373. [28] A. Petushkov, N. Ndiege, A.K. Salem, S.C. Larsen, Chapter 7 — toxicity of silica nanomaterials: zeolites, mesoporous silica, and amorphous silica nanoparticles, in: C.F. James (Ed.) Advances in Molecular Toxicology, 4, Elsevier Publishers 2011, pp. 223–266. [29] J. Shi, Y. Hedberg, M. Lundin, I. Odnevall Wallinder, H.L. Karlsson, L. Moller, Hemolytic properties of synthetic nano- and porous silica particles: the effect of surface properties and the protection by the plasma corona, Acta Biomater. 8 (2012) 3478–3490. [30] Q. Liang, D. Zhao, Immobilization of arsenate in a sandy loam soil using starchstabilized magnetite nanoparticles, J. Hazard. Mater. 271 (2014) 16–23. [31] D. Manno, E. Filippo, M. Di Giulio, A. Serra, Synthesis and characterization of starchstabilized Ag nanostructures for sensors applications, J. Non-Cryst. Solids 354 (2008) 5515–5520. [32] K. Lee, A.N. Sathyagal, A.V. McCormick, A closer look at an aggregation model of the Stöber process, Colloids Surf. A Physicochem. Eng. Asp. 144 (1998) 115–125. [33] O. Danos, K. Davies, P. Lehn, R. Mulligan, The arrive guidelines, a welcome improvement to standards for reporting animal research, J. Gene Med. 12 (2009) 559–560. [34] Y. Hu, Z. Zhi, T. Wang, T. Jiang, S. Wang, Incorporation of indomethacin nanoparticles into 3-D ordered macroporous silica for enhanced dissolution and reduced gastric irritancy, Eur. J. Pharm. Biopharm. 79 (2011) 544–551. [35] N. Jovanovic, A. Bouchard, M. Sutter, M. Van Speybroeck, G.W. Hofland, G.J. Witkamp, D.J. Crommelin, W. Jiskoot, Stable sugar-based protein formulations by supercritical fluid drying, Int. J. Pharm. 346 (2008) 102–108. [36] Q. Wang, G. Li, B. Zhao, R. Zhou, Synthesis of La modified ceria–zirconia solid solution by advanced supercritical ethanol drying technology and its application in Pd-only three-way catalyst, Appl. Catal. B Environ. 100 (2010) 516–528. [37] S. Abbas, M. Bashari, W. Akhtar, W.W. Li, X. Zhang, Process optimization of ultrasound-assisted curcumin nanoemulsions stabilized by OSA-modified starch, Ultrason. Sonochem. 21 (2014) 1265–1274. [38] H. Nakabayashi, A. Yamada, M. Noba, Y. Kobayashi, M. Konno, D. Nagao, Electrolyteadded one-pot synthesis for producing monodisperse, micrometer- sized silica particles up to 7 μm, Langmuir 26 (2010) 7512–7515. [39] K. Nozawa, H. Gailhanou, L. Raison, P. Panizza, H. Ushiki, E. Sellier, J. Delville, M. Delville, Smart control of monodisperse Stöber silica particles: effect of reactant addition rate on growth process, Langmuir 21 (2005) 1516–1523. [40] J. Gel, W. Zhongl, Z. Guol, W. Li, K. Sakai, Biodegradable and highly resilient polyurethane poams from bark and starch, J. Appl. Polym. Sci. 77 (2001) 2575–2580. [41] B. Priya, V.K. Gupta, D. Pathania, A.S. Singha, Synthesis, characterization and antibacterial activity of biodegradable starch/PVA composite films reinforced with cellulosic fibre, Carbohydr. Polym. 109 (2014) 171–179. [42] H. Ramesh, S. Viswanatha, R. Tharanathan, Safety evaluation of formulations containing carboxymethyl derivatives of starch and chitosan in albino rats, Carbohydr. Polym. 58 (2014) 435–441. [43] A. Patterson, The scherrer formula for X-ray particle size determination, Phys. Rev. 56 (1939) 978. [44] N. Coceani, L. Magarotto, D. Ceschia, I. Colombo, M. Grassi, Theoretical and experimental analysis of drug release from an ensemble of polymeric particles containing amorphous and nano-crystalline drug, Chem. Eng. Sci. 71 (2012) 345–355. [45] M. Casas, C. Ferrero, M.V. de Paz, M.R. Jiménez-Castellanos, Synthesis and characterization of new copolymers of ethyl methacrylate grafted on tapioca starch as novel excipients for direct compression matrix tablets, Eur. Polym. J. 45 (2009) 1765–1776. [46] A. Okunlola, O.A. Odeku, Evaluation of starches obtained from four Dioscorea species as binding agent in chloroquine phosphate tablet formulations, Saudi Pharm. J. 19 (2011) 95–105. [47] F. Zhu, Structure, physicochemical properties, and uses of millet starch, Food Res. Int. 64 (2014) 200–211. [48] J.N. BeMiller, Pasting, paste, and gel properties of starch–hydrocolloid combinations, Carbohydr. Polym. 86 (2011) 386–423. [49] D. Xia, P. Quan, H. Piao, S. Sun, Y. Yin, F. Cui, Preparation of stable nitrendipine nanosuspensions using the precipitation-ultrasonication method for enhancement of dissolution and oral bioavailability, Eur. J. Pharm. Sci. 40 (2010) 325–334. [50] S. Cogswell, S. Berger, D. Waterhouse, M.B. Bally, E.K. Wasan, A parenteral econazole formulation using a novel micelle-to-liposome transfer method: in vitro characterization and tumor growth delay in a breast cancer xenograft model, Pharm. Res. 23 (2006) 2575–2585. [51] A.K. Shchekin, A.I. Rusanov, Generalization of the Gibbs–Kelvin–Köhler and Ostwald–Freundlich equations for a liquid film on a soluble nanoparticle, J. Chem. Phys. 129 (2008) 154116.