Ampicillin micronization by supercritical assisted atomization

The micronization technique called supercritical assisted atomization (SAA) was used to produce ampicillin microparticles with controlled particle size and particle size distribution suitable for aerosol drug delivery. The process is based on the solubilization of supercritical CO2 in a liquid solution. The ternary mixture is then sprayed through a nozzle and, as a consequence of enhanced atomization, solid microparticles are formed. Water and organic solvents were tested with ampicillin to determine the influence of the solvent on the process mechanism. SAA process parameters were studied by testing different supercritical/liquid solvent flow ratios, ampicillin concentrations in the liquid solution and nozzle diameters. The effect of these parameters on morphology, particle size and particle size distribution of microparticles was analysed. Ampicillin particles suitable for aerosol delivery in the size range 1-5 microm were obtained using buffered water. Moreover, by varying the solute concentration, ampicillin particles in a narrower range (1-3 microm) than that usually suggested for aerosol deliverable drugs were obtained. This is an example of particle size tailoring by SAA.     

Simultaneous micronization and surface modification for improvement of flow and dissolution of drug particles

Simultaneous micronization and surface modification of drug particles is considered in order to mitigate disadvantages of micronization, e.g., agglomeration, poor flowability, marginal increase in surface area and low bulk density. Particles of ibuprofen (102 μm), a model drug, pre-blended with hydrophilic nano-silica, are micronized down to 10 and 5 μm in a continuous fluid energy mill (FEM) to obtain fine surface modified particles. The solid feeding rate and the grinding pressure are shown as critical parameters for achieving the desired particle size and size distribution. The powder properties were characterized via SEM, laser scattering, powder rheometer with shear-cell, and dissolution test. Significant improvement in flow properties and dissolution rate was observed when micronization accompanied surface modification. Additionally, co-grinding with water-soluble polymer during micronization led to further increase in bulk density and more enhanced dissolution rate improvement, which is attributed to improved wettability. XRD, DSC and Raman were used to examine crystallinity, indicating minimal detectable physical transformation with FEM processed ibuprofen. The surface modified, micronized powders also showed improved dispersion, higher bulk densities (>0.4 g/ml), reduced electrostatic, and higher flowability (FFC ≥ 6) compared to just micronized powder (0.19 g/ml, FFC=1.0), indicating they may be used in high drug loaded formulations amenable to direct compression.     

Bioactive insulin microparticles produced by supercritical fluid assisted atomization with an enhanced mixer

Supercritical fluid assisted atomization introduced by a hydrodynamic cavitation mixer (SAA–HCM) was used to micronize insulin from aqueous solution without use of any organic solvents. Insulin microparticles produced under different operating conditions including solution type, solution concentration and precipitator temperature presented distinct morphologies such as highly folded, partly deflated, corrugated or smooth hollow spherical shape. Solution concentration had a striking influence on particle size, and insulin microparticles produced from acidic solution had mean diameters increasing from 1.4 μm to 2.7 μm when protein concentration increased from 3 g/L to 50 g/L. HPLC chromatograms showed no degradation of insulin after SAA–HCM processing and FTIR, CD and fluorescence data further confirmed the structural stability. TGA analysis revealed that insulin microparticles remained moderate moisture content compared with raw material. In vivo study showed that insulin processed by SAA–HCM from acidic solution retained identical bioactivity. SAA–HCM is demonstrated to be a very promising process for insulin inhaled formulation development.     

Supercritical fluid assisted atomization introduced by an enhanced mixer for micronization of lysozyme: Particle morphology, size and protein stability

Supercritical fluid assisted atomization introduced by hydrodynamic cavitation mixer (SAA-HCM) was used to produce lysozyme microparticles with controlled particle size distribution in the range for aerosol drug delivery. The process is based on the atomization effect of carbon dioxide. The solubilization of certain amount of carbon dioxide in the solution plays the key role and the HCM can intensify mass transfer between carbon dioxide and liquid feedstock greatly. Water was used as the solvent to solubilize lysozyme and thus no organic residual was detected. The influences of process parameters on particle formation were investigated including temperature in the precipitator, pressure and temperature in the mixer, concentration of the solution and feed ratio CO(2)/solution. The particles were characterized with respect to their morphologies and particle size: well defined, spherical and separated particles with diameters ranging between 0.2 and 5μm could be always produced at optimum operating conditions. Bio-activity assay showed that good activity maintenance of higher than 85% for lysozyme was usually achieved. Solid state characterizations were further performed to investigate the changes of lysozyme in the process. Fourier transform infrared spectroscopy indicated that no change in secondary structure had occurred for processed lysozyme. X-ray diffraction analysis showed that the lysozyme particles produced remained similarly amorphous as the raw material. Differential scanning calorimetry and thermogravimetry analysis revealed that there was no significant difference in water association but with the increase of water content after processing.     

Improvement of the dissolution rate of artemisinin by means of supercritical fluid technology and solid dispersions

The purpose of this study was to enhance the dissolution rate of artemisinin in order to improve the intestinal absorption characteristics. The effect of: (1) micronisation and (2) formation of solid dispersions with PVPK25 was assessed in an in vitro dissolution system [dissolution medium: water (90%), ethanol (10%) and sodium lauryl sulphate (0.1%)]. Coulter counter analysis was used to measure particle size. X-ray diffraction and DSC were used to analyse the physical state of the powders. Micronisation by means of a jet mill and supercritical fluid technology resulted in a significant decrease in particle size as compared to untreated artemisinin. All powders appeared to be crystalline. The dissolution rate of the micronised forms improved in comparison to the untreated form, but showed no difference in comparison to mechanically ground artemisinin. Solid dispersions of artemisinin with PVPK25 as a carrier were prepared by the solvent method. Both X-ray diffraction and DSC showed that the amorphous state was reached when the amount of PVPK25 was increased to 67%. The dissolution rate of solid dispersions with at least 67% of PVPK25 was significantly improved in comparison to untreated and mechanically ground artemisinin. Modulation of the dissolution rate of artemisinin was obtained by both particle size reduction and formation of solid dispersions. The effect of particle size reduction on the dissolution rate was limited. Solid dispersions could be prepared by using a relatively small amount of PVPK25. The formation of solid dispersions with PVPK25 as a carrier appears to be a promising method to improve the intestinal absorption characteristics of artemisinin.     

A three step supercritical process to improve the dissolution rate of eflucimibe.

The aim of this study is to improve the dissolution properties of a poorly-soluble active substance, Eflucimibe by associating it with gamma-cyclodextrin. To achieve this objective, a new three-step process based on supercritical fluid technology has been proposed. First, Eflucimibe and cyclodextrin are co-crystallized using an anti-solvent process, dimethylsulfoxide being the solvent and supercritical carbon dioxide being the anti-solvent. Second, the co-crystallized powder is held in a static mode under supercritical conditions for several hours. This is the maturing step. Third, in a final stripping step, supercritical CO(2) is flowed through the matured powder to extract the residual solvent. The coupling of the first two steps brings about a significant synergistic effect to improve the dissolution rate of the drug. The nature of the entity obtained at the end of each step is discussed and some suggestions are made as to what happens in these operations. It is shown the co-crystallization ensures a good dispersion of both compounds and is rather insensitive to the operating parameters tested. The maturing step allows some dissolution-recrystallization to occur thus intensifying the intimate contact between the two compounds. Addition of water is necessary to make maturing effective as this is governed by the transfer properties of the medium. The stripping step allows extraction of the residual solvent but also removes some of the Eflucimibe which is the main drawback of this final stage.     

管状介孔硅用于提高西洛他唑的溶出速率及对其物理稳定性的影响

目的以合成不同于传统球形介孔硅的管状硅(mesoporous silica tube,MST)为载体,制备西洛他唑(cilostazol,CLT)固体分散体系(CLT-MST),提高难溶性药物CLT的溶出速率和物理稳定性。方法采用多壁纳米碳管(carbon nanotube,CNT)为硬模板,以表面活性剂十六烷基三甲基溴化铵(cetyltrimethyl ammonium bromide,CTAB)为辅助模板制备MST,应用扫描电子显微镜(scanning electron microscope,SEM)、透射电子显微镜(transmission electron microscope,TEM)和比表面积分析仪表征MST外在形貌和内部孔道特征。采用挥干载药的方法,将CLT载入制备的MST中,并测定所制备的固体分散体系的药物溶出度,以差示扫描量热仪(differential scanning calorimetry,DSC)和X射线衍射仪(X ray diffraction,XRD)分析药物在载体中的存在状态。最后对介孔硅固体分散体系进行稳定性试验。结果所制备CLT-MST在1 h时累计溶出度达到82%,且储存6个月后CLTMST的DSC和XRD表征图谱均没有显著变化。结论 MST可使难溶性药物CLT高度分散,能够改善CLT的溶出速率以及保持CLT的物理稳定性。     

固体分散技术提高枸橼酸莫沙必利片溶出度的研究

目的考察固体分散技术对枸橼酸莫沙必利片的体外溶出度的影响。方法以聚维酮K30为载体制备枸橼酸莫沙必利片固体分散体,紫外分光光度法对其体外溶出度进行测定。结果聚维酮K30-枸橼酸莫沙必利比例大于2∶1(w/w)时所得枸橼酸莫沙必利片5 min累积溶出量接近100%,而市售品溶出缓慢,5 min累积溶出量约为50%,30min累积溶出量约为90%。结论采用固体分散技术制备的枸橼酸莫沙必利片能显著提高枸橼酸莫沙必利的溶出速率。     

介孔碳(CMK-3)载体用于提高非诺贝特溶出速率及物理稳定性的研究

目的以制备的介孔碳(CMK-3)为载体载入非诺贝特制备纳米药物分散体系,以期提高非诺贝特的溶出速率和纳米分散药物的稳定性。方法采用吸附平衡法将模型药物非诺贝特载入到碳载体中,应用扫描电子显微镜(SEM)来表征制备载体的形貌,透射电子显微镜(TEM)和氮吸附曲线表征载体的内部孔道结构,差示扫描量热(DSC)和X射线衍射(XRD)研究药物在载体中的存在状态,采取溶出度测定方法研究所制备的载药体系的药物溶出速度,并测定其长期稳定性。结果药物已载入碳载体的纳米孔道中,且药物粒子的高度分散和晶型的转变,显著提高了难溶性药物非诺贝特的溶出速率,并且碳载体的刚性结构有效阻止了分散药物粒子的再聚集,物理稳定性大大提高。结论制备的非诺贝特-CMK-3载药体系,为提高难溶性药物的生物利用度以及解决纳米分散药物的物理稳定性等问题,提供了一种可能。     

Enhancement of dissolution rate of poorly-soluble active ingredients by supercritical fluid processes. Part I: Micronization of neat particles

In this first of two articles, we discuss some issues surrounding the dissolution rate enhancement of poorly-soluble active ingredients micronized into nano-particles using several supercritical fluid particle design processes including rapid expansion of supercritical solutions (RESS), supercritical anti-solvent (SAS) and particles from gas-saturated solutions/suspensions (PGSS). Experimental results confirm that dissolution rates do not only depend on the surface area and particle size of the processed powder, but are greatly affected by other physico-chemical characteristics such as crystal morphology and wettability that may reduce the benefit of micronization.     

Use of the liquisolid compact technique for improvement of the dissolution rate of valsartan

The aim of this study was to improve the dissolution rate of the poorly soluble drug valsartan by delivering the drug as a liquisolid compact. Liquisolid compacts were prepared using propylene glycol as solvent, Avicel PH102 as carrier, and Aerosil 200 as the coating material. The crystallinity of the newly formulated drug and the interaction between excipients was examined by X-ray powder diffraction and Fourier-transform infrared spectroscopy, respectively. The dissolution studies for the liquisolid formulation and the marketed product were carried out at different pH values. The results showed no change in the crystallinity of the drug and no interaction between excipients. The dissolution efficiency of valsartan at 15 min was increased from 4.02% for plain drug and 13.58% for marketed product to 29.47% for the liquisolid formulation. The increase in the dissolution rate was also found to be significant compared to the marketed product at lower pH values, simulating the gastric environment where valsartan is largely absorbed. The liquisolid technique appears to be a promising approach for improving the dissolution of poorly soluble drugs like valsartan.     

Enhancement of dissolution rate of poorly soluble active ingredients by supercritical fluid processes. Part II: Preparation of composite particles

In this second of two articles, we show that several supercritical processes have been developed to prepare composite particles of poorly soluble active ingredients. Microencapsulation, cyclodextrin inclusion and impregnation allow to incorporate poorly soluble materials in fast-dissolving hydrophilic excipients, leading to promising results in terms of dissolution rate enhancement.     

羧基化三维有序大孔炭载体用于提高羟基喜树碱的溶出度

目的制备羧基化三维有序大孔炭载体,提高水难溶性药物羟基喜树碱的溶出度。方法采用硬模板法制备三维有序大孔炭载体,以扫描电子显微镜(scanning electron microscopy,SEM)进行表征。采用表面氧化法进行羧基化修饰,对修饰前后的载体进行IR表征及Zeta电位测定。采用溶剂挥发法载药,测定载药量并对载药体系的水分散性进行考察。以DSC考察药物于载体中的存在状态,对原料药及羧基化修饰前后的载药体系的药物溶出度进行测定。结果制得的三维有序大孔炭载体孔道呈互相连通的三维结构,外孔孔径为500nm,内孔孔径为200nm。羧基化修饰后载体的Zeta电位显著降至-16mV,IR谱图中可见明显的羧基吸收峰。羟基喜树碱的载药量质量分数约为24%,羧基化修饰的载药体系水分散性显著提高,DSC显示其中所载药物的结晶峰明显减弱。原料药1h累计释放度仅为24.7%,羧基化修饰的载药体系药物累计释放度升至83.6%。结论制备的羧基化三维有序大孔炭载体可利用其独特的结构特征及改善的水分散性显著提高羟基喜树碱的溶出度。     

Single-step preparation and deagglomeration of itraconazole microflakes by supercritical antisolvent method for dissolution enhancement

Itraconazole (ITZ) microflakes were produced by supercritical antisolvent (SAS) method and simultaneously mixed with pharmaceutical excipients in a single step to prevent drug agglomeration. Simultaneous ITZ particle formation and mixing with fast-flo lactose (FFL) was performed in a high-pressure stirred vessel at 116 bar and 40 °C by the SAS-drug excipient mixing (SAS-DEM) method. The effects of stabilizers, such as sodium dodecyl sulfate and poloxamer 407 (PLX), on particle formation and drug dissolution were studied. Drug-excipient formulations were characterized for surface morphology, crystallinity, drug-excipient interactions, drug content uniformity, and drug dissolution rate. Mixture of drug microflakes and FFL formed by the SAS-DEM process shows that the process was successful in overcoming drug-drug agglomeration. PLX produced crystalline drug flakes in loose agglomerates with superior dissolution and flow properties even at higher drug loadings. Characterization studies confirmed the crystallinity of the drug and absence of chemical interactions during the SAS process. The dissolution of ITZ was substantially higher due to SAS and SAS-DEM processes; this improvement can be attributed to the microflake particle structures, effective deagglomeration, and wetting of the drug flakes with the excipients.     

Increased dissolution rate and oral bioavailability of hydrophobic drug glyburide tablets produced using supercritical CO2 silica dispersion technology

The aim of this study was to design a silica-supported solid dispersion of a water-insoluble drug, glyburide, to increase its dissolution rate and oral absorption using supercritical fluid (SCF) technology. DSC and PXRD results indicated that the encapsulated drug in the optimal solid dispersion was in an amorphous state and the product was stable for 6 months. Glyburide was adsorbed onto the porous silica, as confirmed by the SEM images and BET analysis. Furthermore, FT-IR spectroscopy confirmed that there was no change in the chemical structure of glyburide after the application of SCF. The glyburide silica-based dispersion could also be compressed into tablet form. In vitro drug release analysis of the silica solid dispersion tablets demonstrated faster release of glyburide compared with the commercial micronized tablet. In an in vivo test, the AUC of the tablets composed of the new glyburide silica-based solid dispersion was 2.01 times greater than that of the commercial micronized glyburide tablets. In conclusion, SCF technology presents a promising approach to prepare silica-based solid dispersions of hydrophobic drugs because of its ability to increase their release and oral bioavailability.     

Carvedilol dissolution improvement by preparation of solid dispersions with porous silica

Impregnation of porous SiO(2) (Sylysia) with carvedilol from acetone solution was used to improve dissolution of this poorly water-soluble drug. Solvent evaporation in a vacuum evaporator and adsorption from acetone solution were the methods used to load various amounts of carvedilol into the Sylysia pores. The impregnated carriers were characterized using nitrogen-adsorption experiments, X-ray diffraction, wettability measurements, attenuated total reflectance FTIR spectroscopy and thermal analysis. The impregnation procedures resulted in a significant improvement of drug release compared to dissolution of pure carvedilol or its physical mixtures with Sylysia. The results showed that when the drug precipitated in a thin layer within the carrier the dispersion retained a high specific surface area, micropore volume, and drug-release rate from the solid dispersion. Increasing the amount of drug in the solid dispersion caused particle precipitation within the pores that decreased the carrier's specific surface area and pore volume and decreased the release rate of the drug. The results also suggest that the amorphous form of carvedilol, the improved wettability and weak interactions between the drug and carrier in the solid dispersion also contribute to improved dissolution of the drug from the dispersion.