Enhanced Aqueous Dissolution of a Poorly Water Soluble Drug by Novel Particle Engineering Technology: Spray-Freezing into Liquid with Atmospheric Freeze-Drying

Purpose. The purpose of this work was to investigate spray-freezing into liquid (SFL) and atmospheric freeze-drying (ATMFD) as industrial processes for producing micronized SFL powders with enhanced aqueous dissolution. Micronized SFL powders dried by ATMFD were compared with vacuum freeze-dried SFL powders. Methods. Danazol was formulated with polyvinyl alcohol (MW 22,000), polyvinylpyrrolidone K-15, and poloxamer 407 to produce micronized SFL powders that were freeze-dried under vacuum or dried by ATMFD. The powders were characterized using Karl-Fischer titration, gas chromatography, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, surface area, and dissolution testing (SLS 0.75%/Tris 1.21% buffer media). Results. Micronized SFL powders containing amorphous drug were successfully dried using the ATMFD process. Micronized SFL powders contained less than 5% w/w and 50 ppm of residual water and organic solvent, respectively, which were similar to those contents detected in a co-ground physical mixture of similar composition. Micronized SFL powders dried by ATMFD had lower surface areas than powders produced by vacuum freeze-drying (5.7 vs. 8.9 m²/g) but significantly greater surface areas than the micronized bulk drug (0.5 m²/g) and co-ground physical mixture (1.9 m²/g). Rapid wetting and dissolution occurred when the SFL powders were introduced into the dissolution media. By 5 min, 100% dissolution of danazol from the ATMFD-micronized SFL powder had occurred, which was similar to the dissolution profile of the vacuum freeze-dried SFL powder. Conclusions. Vacuum freeze-drying is not a preferred technique in the pharmaceutical industry because of scalability and high-cost concerns. The ATMFD process enables commercialization of the SFL particle-engineering technology as a micronization method to enhance dissolution of hydrophobic drugs.     

Spray freezing into liquid (SFL) particle engineering technology to enhance dissolution of poorly water soluble drugs: organic solvent versus organic/aqueous co-solvent systems.

A spray freezing into liquid (SFL) particle engineering technology has been developed to produce micronized powders to enhance the dissolution of poorly water soluble active pharmaceutical ingredients (APIs). Previously, a tetrahydrofuran (THF)/water co-solvent was used as the solution source in the SFL process. In the present study, an organic system was developed to further enhance the properties of particles produced by SFL. The influence of solution type (e.g. organic versus organic/water) on the physicochemical properties of SFL powders was investigated and compared. The physicochemical properties of SFL carbamazepine (CBZ)/poloxamer 407/PVP K15 (2:1:1 ratio) powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size distribution, surface area analysis, contact angle measurement, Karl-Fisher (KF) titration, gas chromatography (GC) analysis, HPLC analysis, and dissolution testing. The CBZ loading in the feed solution of the SFL acetonitrile system was 2.2% (w/w), which was greater than 0.22% (w/w) loading of the THF/water co-solvent system. XRD results indicated CBZ was amorphous in SFL powders produced by either system. SEM micrographs indicated that SFL powders from acetonitrile appeared less porous with a smaller primary particle size than particles from the co-solvent. The M50 (50% cumulative percent undersize) of micronized powder from the SFL acetonitrile system and the THF/water co-solvent system with 0.22% CBZ loading were 680nm and 7.06microm, respectively. The surface area of SFL powders from the acetonitrile and co-solvent systems were 12.89 and 13.31m(2)/g, respectively. The contact angle of the SFL powders against purified water was about 35 degrees for both systems. The SFL powders from both systems exhibited similar and significantly enhanced dissolution rates compared to the bulk CBZ. Acetonitrile was an effective alternative solvent to THF/water co-solvent for use with the SFL micronization process to produce free flowing particles containing CBZ with significantly enhanced wetting and dissolution properties.     

Physical stability of micronized powders produced by spray-freezing into liquid (SFL) to enhance the dissolution of an insoluble drug

PURPOSE: The objective of this study was to investigate the physical stability of micronized powders produced by the spray-freezing into liquid (SFL) particle engineeringtechnology. MATERIALS AND METHODS: Danazol was formulated with polyvinyl alcohol (MW 22,000), poloxamer 407, and polyvinylpyrrolidone K-15 to form a cosolvent solution that was SFL processed. The dried micronized SFL powders were sealed in glass vials with desiccant and exposed to 25 degrees C/60% RH for 3 and 6 mo, 40 degrees C/75% RH for 1, 2, 3, and 6 mo, and conditions where the temperature was cycled between -5 and +40 degrees C (6 cycles/24 hr) with constant 75% RH for 1, 2, 3 and 4 wk. The samples were characterized by using Karl-Fisher titration, differential scanning calorimetry, x-ray diffraction, specific surface area, scanning electron microscopy, and dissolution testing. RESULTS: Micronized SFL powders consisting of porous aggregates with small-particle domains were characterized as having high surface areas and consisted of amorphous danazol embedded within a hydrophilic excipient matrix. Karl-Fischer titration revealed no moisture absorption over the duration of the stability studies. Differential scanning calorimetry studies demonstrated high degrees of molecular interactions between danazol, PVA, poloxamer, and PVP. Scanning electron microscopy studies confirmed these interactions, especially those between danazol and poloxamer. These interactions facilitated API dissolution in the aqueous media. Powder surface area remained constant during storage at the various stability conditions, and danazol recrystallization did not occur during the entirety of the stability studies. Micronized SFL powders containing danazol dissolved rapidly and completely within 5 min in aqueous media. No differences were observed in the enhanced dissolution profiles of danazol after exposure to the storage conditions investigated. Physically stable micronized powders produced by the SFL particle engineering technology were produced for the purpose of enhancing the dissolution of an insoluble drug. CONCLUSIONS: The potential of the SFL particle-engineering technology as a micronization technique for enhancing the dissolution of hydrophobic drugs was demonstrated in this study. The robustness of the micronized SFL powders to withstand stressed storage conditions was shown.     

Micronized powders of a poorly water soluble drug produced by a spray-freezing into liquid-emulsion process.

The purpose of this paper is to investigate the influence of the emulsion composition of the feed liquid on physicochemical characteristics of drug-loaded powders produced by spray-freezing into liquid (SFL) micronization, and to compare the SFL emulsion process to the SFL solution process. Danazol was formulated with polyvinyl alcohol (MW 22,000), poloxamer 407, and polyvinylpyrrolidone K-15 in a 2:1:1:1 weight ratio (40% active pharmaceutical ingredient (API) potency based on dry weight). Emulsions were formulated in ratios up to 20:1:1:1 (87% API potency based on dry weight). Ethyl acetate/water or dichloromethane/water mixtures were used to produce o/w emulsions for SFL micronization, and a tetrahydrofuran/water mixture was used to formulate the feed solutions. Micronized SFL powders were characterized by X-ray diffraction, surface area, scanning and transmission electron microscopy, contact angle and dissolution. Emulsions containing danazol in the internal oil phase and processed by SFL produced micronized powders containing amorphous drug. The surface area increased as drug and excipient concentrations were increased. Surface areas ranged from 8.9 m(2)/g (SFL powder from solution) to 83.1 m(2)/g (SFL powder from emulsion). Danazol contained in micronized SFL powders from emulsion and solution was 100% dissolved in the dissolution media within 2 min, which was significantly faster than the dissolution of non-SFL processed controls investigated (<50% in 2 min). Micronized SFL powders produced from emulsion had similar dissolution enhancement compared to those produced from solution, but higher quantities could be SFL processed from emulsions. Potencies of up to 87% yielded powders with rapid wetting and dissolution when utilizing feed emulsions instead of solutions. Large-scale SFL product batches were manufactured using lower solvent quantities and higher drug concentrations via emulsion formulations, thus demonstrating the usefulness of the SFL micronization technology in pharmaceutical development.     

Rapid dissolving high potency danazol powders produced by spray freezing into liquid process

The objective of this study was to investigate the use of organic solvents in the spray freezing into liquid (SFL) particle engineering process to make rapid dissolving high potency danazol powders and to examine their particle size, surface area and dissolution rate. The maximum drug potency produced was 91% for SFL micronized danazol/PVP K-15. XRD indicated that danazol in the high potency SFL powders was amorphous. SEM micrographs revealed that the SFL danazol/PVP K-15 nanostructured aggregates had a porous morphology and were composed of many smooth primary nanoparticles with a diameter of about 100 nm. Surface areas of SFL danazol/PVP K-15 high potency powders were in the range of 28-115 m2/g. The SFL powders exhibited significantly enhanced dissolution rates. The rate of dissolution of micronized bulk danazol was slow; only 30% of the danazol was dissolved in 2 min. However, 95% of danazol was dissolved in only 2 min for the SFL high potency powders. The SFL process offers a highly effective approach to produce high potency danazol nanoparticles contained in larger structured aggregates with rapid dissolution rates, and is especially applicable to delivery systems containing poorly water soluble drugs.     

Comparison of powder produced by evaporative precipitation into aqueous solution (EPAS) and spray freezing into liquid (SFL) technologies using novel Z-contrast STEM and complimentary techniques.

The objective of this study was to compare the properties of particles formed by nucleation and polymer stabilization (e.g. evaporative precipitation into aqueous solution (EPAS)) versus rapid freezing (e.g. spray freezing into liquid (SFL)). Powders formed by EPAS and SFL, composed of danazol and PVP K-15 in a 1:1 ratio, were characterized using X-ray powder diffraction, modulated differential scanning calorimetry (MDSC), contact angle determination, dissolution, scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), BET specific surface area, and Z-contrast scanning transmission electron microscopy (STEM). Large differences in particle morphologies and properties were observed and explained in terms of the particle formation mechanisms. Both techniques produced amorphous powders with high T(g) and low contact angle values. However, STEM analysis showed highly porous bicontinuous nanostructured 30nm particles connected by narrow bridges for SFL versus aggregated 500 nm primary particles for EPAS. The combination of STEM and other characterization techniques indicates solid solutions were formed for the SFL powders consistent with rapid freezing. In contrast, the EPAS particle cores are enriched in hydrophobic API and the outer surface is enriched in the hydrophilic polymer, with less miscibility than in the SFL powders. Consequently, dissolution rates are faster for the SFL particles, although both techniques enhanced dissolution rates of the API.     

A novel particle engineering technology: spray-freezing into liquid

Spray-freezing into liquid (SFL) is a novel particle engineering technology where a feed solution containing an active pharmaceutical ingredient (API) and pharmaceutical excipient(s) is atomized beneath the surface of a cryogenic liquid, such as liquid nitrogen. Intense atomization results from the impingement that occurs between the liquid feed and the cryogenic liquid. The atomized feed droplets instantly solidify within the liquid nitrogen continuous phase to form a suspension. The frozen microparticles are then collected and lyophilized to obtain the dry SFL micronized powder. The novel SFL process has been used in this study to enhance the dissolution rates of two poorly water soluble APIs, carbamazepine and danazol. The SFL process has also been used to produce stable peptide particles of insulin.     

A novel particle engineering technology to enhance dissolution of poorly water soluble drugs: spray-freezing into liquid.

A novel cryogenic spray-freezing into liquid (SFL) process was developed to produce microparticulate powders consisting of an active pharmaceutical ingredient (API) molecularly embedded within a pharmaceutical excipient matrix. In the SFL process, a feed solution containing the API was atomized beneath the surface of a cryogenic liquid such that the liquid-liquid impingement between the feed and cryogenic liquids resulted in intense atomization into microdroplets, which were frozen instantaneously into microparticles. The SFL micronized powder was obtained following lyophilization of the frozen microparticles. The objective of this study was to develop a particle engineering technology to produce micronized powders of the hydrophobic drug, danazol, complexed with hydroxypropyl-beta-cyclodextrin (HPbetaCD) and to compare these SFL micronized powders to inclusion complex powders produced from other techniques, such as co-grinding of dry powder mixtures and lyophilization of bulk solutions. Danazol and HPbetaCD were dissolved in a water/tetrahydrofuran cosolvent mixture prior to SFL processing or slow freezing. Identical quantities of the API and HPbetaCD used in the solutions were co-ground in a mortar and pestle and blended to produce a co-ground physical mixture for comparison. The powder samples were characterized by differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy, surface area analysis, and dissolution testing. The results provided by DSC, XRD, and FTIR suggested the formation of inclusion complexes by both slow-freezing and SFL. However, the specific surface area was significantly higher for the latter. Dissolution results suggested that equilibration of the danazol/HPbetaCD solution prior to SFL processing was required to produce the most soluble conformation of the resulting inclusion complex following SFL. SFL micronized powders exhibited better dissolution profiles than the slowly frozen aggregate powder. Results indicated that micronized SFL inclusion complex powders dissolved faster in aqueous dissolution media than inclusion complexes formed by conventional techniques due to higher surface areas and stabilized inclusion complexes obtained by ultra-rapid freezing.     

Protein Inhalation Powders: Spray Drying vs Spray Freeze Drying

Purpose. To develop a new technique, spray freeze drying, for preparing protein aerosol powders. Also, to compare the spray freeze-dried powders with spray-dried powders in terms of physical properties and aerosol performance. Methods. Protein powders were characterized using particle size analysis, thermogravimetric analysis, scanning electron microscopy, X-ray powder diffractometry, and specific surface area measurement. Aerosol performance of the powders was evaluated after blending with lactose carriers using a multi-stage liquid impinger or an Anderson cascade impactor. Two recombinant therapeutic proteins currently used for treating respiratory tract-related diseases, deoxyribonuclase (rhDNase) and anti-IgE monoclonal antibody (anti-IgE MAb), were employed and formulated with different carbohydrate excipients. Results. Through the same atomization but the different drying process, spray drying (SD) produced small (3 m), dense particles, but SFD resulted in large (8–10 m), porous particles. The fine particle fraction (FPF) of the spray freeze-dried powder was significantly better than that of the spray-dried powder, attributed to better aerodynamic properties. Powders collected from different stages of the cascade impactor were characterized, which confirmed the concept of aerodynamic particle size. Protein formulation played a major role in affecting the powder's aerosol performance, especially for the carbohydrate excipient of a high crystallization tendency. Conclusions. Spray freeze drying, as opposed to spray drying, produced protein particles with light and porous characteristics, which offered powders with superior aerosol performance due to favorable aerodynamic properties.     

Use of Solid Corrugated Particles to Enhance Powder Aerosol Performance

Purpose. To study the dispersion performance of non-porous corrugated particles, with a focus on the effect of particle surface morphology on aerosolization of bovine serum albumin (BSA) powders. Methods. The solid-state characteristics of the spray-dried BSA powders, one consisting of smooth spherical particles and another corrugated particles, were characterized by laser diffraction, X-ray powder diffraction, scanning electron microscopy, confocal microscopy, thermogravimetric analysis, surface area analyzer, and buoyancy method. The powders were dispersed using the Rotahaler® and the Dinkihaler® coupled to a four-stage liquid impinger operating at 30 to 120 L/min. Fine particle fraction (FPF) was expressed as the wt. % of BSA particles of size 5 m collected from the liquid impinger. Results. Apart from the morphology and morphology-related properties (specific surface area, envelope density), the corrugated particles and spherical particles of BSA had very similar solid-state characteristics (particle size distribution, water content, true density, amorphous nature). Using the Dinkihaler®, the FPFs of the corrugated particles were 10-20 wt. % higher than those of the smooth particles. Similar FPF differences were found for the powders dispersed by the Rotahaler®, but the relative changes were larger. In addition, the differences were inversely proportional to the air flows (17.3% at 30 L/min, 25.2% at 60 L/min, 13.8% at 90, 8.5% at 120 L/min). Depending on the inhaler, capsule and device retention and impaction loss at the impinger throat were lower for the corrugated particles. Conclusions. Enhanced aerosol performance of powders can be obtained by surface modification of the particles. The surface asperities of the corrugated particles could lower the true area of contact between the particles, and thus reduce the powder cohesiveness. A distinct advantage of using corrugated particles is that the inhaler choice and air flow become less critical for these particles.     

Cryogenic liquids, nanoparticles, and microencapsulation

The biopharmaceutical classification system (BCS) is used to group pharmaceutical actives depending upon the solubility and permeability characteristics of the drug. BCS class II compounds are poorly soluble but highly permeable, exhibiting bioavailability that is limited by dissolution. The dissolution rate of BCS class II drug substances may be accelerated by enhancing the wetting of the bulk powder and by reducing the primary particle size of the drug to increase the surface area. These goals may be achieved by nucleating drug particles from solution in the presence of stabilizing excipients. In the spray freezing into liquid (SFL) process, a drug containing solution is atomized and frozen rapidly to engineer porous amorphous drug/excipient particles with high surface areas and dissolution rates. Aqueous suspensions of nanostructured particles may be produced from organic solutions by evaporative precipitation into aqueous solution (EPAS). The suspensions may be dried by lyophilization. The particle size and morphology may be controlled by the type and level of stabilizers. In vivo studies have shown increased bioavailability of a wide variety of drugs particles formed by SFL or EPAS. For both processes, increased serum levels of danazol (DAN) were observed in mice relative to bulk DAN and the commercial product, Danocrine. Orally dosed itraconazole (ITZ) compositions, formed by SFL, produce higher serum levels of the drug compared to the commercial product, Sporanox oral solution. Additionally, nebulized SFL processed ITZ particles suspended in normal saline have been dosed via the pulmonary route and led to extended survival times for mice inoculated with Aspergillis flavus. SFL and EPAS processes produce amorphous drug particles with increased wetting and dissolution rates, which will subsequently supersaturate biological fluids in vivo, resulting in increased drug bioavailability and efficacy.     

Influence of Particle Size,Air Flow,and Inhaler Device on the Dispersion of Mannitol Powders as Aerosols

Purpose. To study the effect of particle size, air flow and inhaler type on the dispersion of spray dried mannitol powders into aerosols. Methods. Mannitol powders were prepared by spray drying. The solid state properties of the powders were determined by laser diffraction, X-ray powder diffraction, scanning electron microscopy, freeze fracture, Karl Fischer titration and gas pycnometry. The powders were dispersed using Rotahaler^® and Dinkihaler^®, connected to a multistage liquid impinger at different air flows. Results. Three crystalline mannitol powders with primary particle size (MMD) 2.7, 5.0, 7.3 m and a similar polydispersity were obtained. The particles were spherical with a density of 1.5 g/cm³ and a moisture content of 0.4 wt.%. At an air flow of 30 L/min all the powders were poorly dispersed by both inhalers. With the Rotahaler^® increasing the flow (60–120 L/min) increased the fine particle fraction (FPF) in the aerosols for the 2.7 m powder, and decreased the FPF for the 7.3 m powder; whereas the FPF for 5.0 m powder was unaffected. With the Dinkihaler^®, all the powders were near complete dispersion at 60 L/min. Conclusions. The FPF in the mannitol powder aerosols was determined by an interplay of the particle size, air flow and inhaler design.     

Dissolution Rate Enhancement by in Situ Micronization of Poorly Water-Soluble Drugs

Purpose. The purpose of this study was to evaluate a novel in situ micronization method avoiding any milling techniques to produce nano- or microsized drug particles by controlled crystallization to enhance the dissolution rate of poorly water-soluble drugs. Methods. Ibuprofen, itraconazole, and ketoconazole microcrystals were prepared by the association of the previously molecularly dispersed drug using a rapid solvent change process. The drug was precipitated in the presence of stabilizing agents, such as hydrocolloids. The obtained dispersion was spray-dried. Particle size, morphology, dissolution rate, specific surface area, and wettability were analyzed. Physicochemical properties were characterized using differential scanning calorimetry and X-ray diffractometry. Results. The obtained dispersions showed a homogeneous particle size distribution. Drugs are obtained in a mean particle size of approximately 2 m and below. A high specific surface area was created and in situ stabilized. Different stabilizers showed differences in protecting the precipitated drug from crystal growth. The surface was hydrophilized because of the adsorbed stabilizer. Thus, a drug powder with markedly enhanced dissolution rate was obtained. Conclusions. In situ micronization is a suitable method for the production of micro-sized drugs. This technique can be performed continuously or discontinuously and uses only common technical equipment. Compared to milled products drug properties are optimized as all particle surfaces are naturally grown, the particle size is more uniformly distributed and the powder is less cohesive.     

Delivery of Nasal Powders of β-Cyclodextrin by Insufflation

Purpose. Delivery of nasal powders of granulated -cyclodextrin by insufflation was studied in order to find the relationship between powder properties and delivery behavior. Methods. Three nasal powder formulations, prepared by granulating -cyclodextrin with different binders, were delivered from a powder insufflation device, in which the dose to be emitted was loaded in a gelatin capsule. The delivery sequence of powder was recorded and characterized using an image analysis program. Results. Particle size was the main parameter affecting nasal powder delivery, both as to the amount of dose sprayed and the aspect of cloud produced. Between 50–150 µm of particle size a substantial change in delivery behavior of powders was observed. Powder of around 100 µm in size showed useful insufflation characteristics for nasal delivery. Bioavailability of nasal formulations of progesterone/-cyclodextrin powders was discussed in term of delivery behavior. Conclusions. The formulation approaches for improving nasal delivery of powders require the use of size optimized carriers. Insufflation of powders over 50 µm can favour the particle deposition by impaction, whereas for powders below 50 µm, deposition by sedimentation is moved. -cyclodextrin is a suitable carrier for achieving high systemic availability following nasal administration of powder formulations.     

Spray Dried Powders and Powder Blends of Recombinant Human Deoxyribonuclease (rhDNase) for Aerosol Delivery

Purpose. We have used rhDNase to investigate the feasibility of developing a dry protein powder aerosol for inhalation delivery. Methods. Powders of rhDNase alone and with sodium chloride were prepared by spray drying. Powder blends were obtained by mixing (tumbling and sieving) pure rhDNase powder with 'carrier' materials (lactose, mannitol or sodium chloride). The weight percent of drug in the blends was between 5 and 70%. The particle size distributions and crystallinity of the spray dried powders were obtained by laser diffraction and X-ray powder diffraction, respectively. Particle morphology was examined by scanning electron microscopy. The ability of the powders and powder blends to be dispersed into respirable aerosols was measured using a Rotahaler connected to a multistage liquid impinger operating at 60 L/min. Results. Pure rhDNase powder was quite cohesive with a fine particle fraction (FPF or 'respirable fraction': % wt. of particles < 7 m in the aerosol cloud) of about 20%. When particles also contained NaCl, the powders were dispersed better to form aerosols. A linear relationship was observed between the NaCl content and FPF for a similar primary size (~3 m volume median diameter) of particles. The particle morphology of these powders varied systematically with the salt content. For the blends, SEM revealed a monolayer-like adhesion of the fine drug particles to the carriers at drug contents 50 % wt. An overall 2-fold increase in FPF of rhDNase in the aerosol cloud was obtained for all the blends compared to the pure drug aerosols. Conclusions. The aerosol properties of spray dried rhDNase powders can be controlled by incorporation of a suitable excipient, such as NaCl, and its relative proportion. Coarse carriers can also enhance the performance of rhDNase dry powder aerosols.     

他克莫司阳离子微乳原位凝胶的制备及体外释放研究

目的 为了改善他克莫司水溶性差、眼部生物利用度低的问题,研制了他克莫司阳离子微乳原位凝胶,并研究其体外药物释放行为,为后期进一步研究提供基础。方法 通过高压均质法制得他克莫司阳离子纳米乳,并将其分散于泊洛沙姆407和泊洛沙姆188中制备他克莫司阳离子微乳原位凝胶。采用无膜溶出模型研究其体外释放行为。结果 采用玻璃瓶倒置法测定胶凝温度,筛选出最优凝胶基质处方为26%泊洛沙姆407和12%泊洛沙姆188;体外释药结果显示凝胶溶蚀速率是决定体外释药速率的关键。结论 成功制备了他克莫司阳离子微乳原位凝胶,其体外释药稳定,能满足眼用制剂要求,展现出良好的眼部应用前景。     

The Effect of Low Concentrations of Molecularly Dispersed Poly(Vinylpyrrolidone) on Indomethacin Crystallization from the Amorphous State

Purpose. To investigate the effect of low concentrations of molecularly dispersed poly(vinylpyrrolidone) (PVP) on indomethacin (IMC) crystallization from the amorphous state using particle size effects to identify possible mechanisms of crystallization inhibition. Methods. Different particle sizes of amorphous IMC and 1, 2, and 5% PVP were stored dry at 30°C for 84 days. PXRD was used to calculate the rate and extent of crystallization and the polymorph formed. Results. Crystallization from amorphous IMC and IMC/PVP molecular dispersions yielded the polymorph of IMC. Crystallization rates were reduced at larger particle size and in the presence of 1, 2, and 5%PVP. Crystallization did not reach completion in some IMC/PVP samples, with the quantity of uncrystallized amorphous phase proportional to particle size. Conclusions. Low concentrations of molecularly dispersed PVP affected IMC crystallization from the amorphous state. Formation of -IMC at rates dependent on particle size indicated that surface nucleation predominated in both the absence and presence of PVP. Excellent correlation was seen between the extent of crystallization and simulated depths of crystal penetration, supporting the hypothesis that increasing local PVP concentration inhibits crystal growth from surface nuclei into the amorphous particle.     

星点设计-效应面法优化贝美前列素眼用温度敏感原位凝胶的处方工艺

目的 使用星点设计-效应面法探讨贝美前列素眼用温度敏感原位凝胶的处方组成，并考察其体外释放度。方法 以泊洛沙姆407和188为凝胶基质，用星点设计-效应面法筛选出最佳处方得到合适的胶凝温度，高效液相色谱法测定贝美前列素眼用凝胶的含量，并以无膜溶出模型考察其体外释放度。结果 处方以1%吐温80，0.03%贝美前列素（w/v）、21%泊洛沙姆407（w/v）和2%泊洛沙姆188（w/v）组成能达到最适胶凝温度。体外释放度的考察结果显示药物的释放与时间呈线性关系。结论 本实验制备的贝美前列素眼用温度敏感原位凝胶具有理想的胶凝温度，能够使药物更加持久地附在给药部位，具有给药方便等优点，是一种值得开发并推广使用的眼用制剂。     

Modification of the Copolymers Poloxamer 407 and Poloxamine 908 can Affect the Physical and Biological Properties of Surface Modified Nanospheres

Purpose. To investigate the effects of the modification of the copolymers poloxamer 407 and poloxamine 908 on the physical and biological properties surface modified polystyrene nanospheres. Methods. A method to modify poloxamer 407 and poloxamine 908, introducing a terminal amine group to each PEO chain has been developed. The aminated copolymers can be subsequently radiolabelled with lodinated (I¹²⁵) Bolton-Hunter reagent. The aminated copolymers were used to surface modify polystyrene nanospheres. The physical and biological properties of the coated nanospheres were studied using particle size, zeta potential, in vitro non-parenchymal cell uptake and in vivo biodistribution experiments. Results. The presence of protonated amine groups in the modified copolymers significantly affected the physical and biological properties of the resulting nanospheres, although the effects were copolymer specific. The protonated surface amine groups in both copolymers reduced the negative zeta potential of the nanospheres. Acetylation of the copolymer's free amine groups resulted in the production of nanospheres with comparable physical properties to control unmodified copolymer coated nanospheres. In vivo, the protonated amine groups in the copolymers increased the removal of the nanospheres by the liver and spleen, although these effects were more pronounced with the modified poloxamer 407 coated nanospheres. Acetylation of the amine groups improved the blood circulation time of the nanospheres providing modified poloxamine 908 coated nanospheres with comparable biological properties to control poloxamine 908 coated nanospheres. Similarly, modified poloxamer 407 coated nanospheres had only slightly reduced circulation times in comparison to control nanospheres. Conclusions. The experiments have demonstrated the importance of copolymer structure on the biological properties of surface modified nanospheres. Modified copolymers, which possess comparable properties to their unmodified forms, could be used in nanosphere systems where antibody fragments can be attached to the copolymers, thereby producing nanospheres which target to specific body sites.     

Aerosol Electrostatics I: Properties of Fine Powders Before and After Aerosolization by Dry Powder Inhalers

Purpose. To evaluate the dependence of fine particle dose charge (FPD charge) generated from powder inhalers on physico-chemical properties of the inhalation powder, inhaler type, deaggregation mechanism, dose number and/or retained powder. Methods. Electrostatic charges were determined on micronized powders and aerosolized fine particle doses withdrawn from two, high efficiency, multidose powder inhalers, Turbohalerand prototype Dryhaler. The behavior of terbutaline sulfate, budesonide, albuterol (sulfate and base), beclomethasone dipropionate and lactose was assessed before and after aerosolization. Results. Both inhalers conferred triboelectric FPD charges during aerosolization in the range –400 pC through +200 pC. Specific charges (charge/unit mass) on the fine particle doses of budesonide from Dryhaler were significantly less than those from Turbohaler (p < 0.01). Electrostatic charges on the potentially respirable cloud of terbutaline sulfate generated by Bricanyl Turbohaler were positive and/or negative and unpredictable. With Pulmicort Turbohaler, FPD charges on budesonide were always positive. Dryhaler was used to determine the chemical dependence of fine particle triboelectrification during the aerosolization of pure materials. A triboelectric series was constructed from the Dryhaler results ranking the powders from positive to negative as budesonide > lactose > albuterol sulfate > terbutaline sulfate albuterol beclomethasone dipropionate. Conclusions. While there was no evidence of FPD charge dependence upon dose number with either inhaler, FPD charges were dependent upon the powder under investigation, as well as the construction and deaggregation mechanism of the inhaler. The specific charge on the fine particle dose of budesonide from Turbohaler corresponded to approximately 200 electronic charges per particle, a value which is known to affect both total and regional aerosol deposition in the human lung. Electrostatic charge effects may be important determinants of aerosol behavior and should not be neglected.