A novel particle engineering technology: spray-freezing into liquid

Supersaturation Produces High Bioavailability of Amorphous Danazol Particles Formed by Evaporative Precipitation into Aqueous Solution and Spray Freezing into Liquid Technologies

The bioavailability of high surface area danazol formulations was evaluated in a mouse model to determine what effect high supersaturation, as measured in vitro, has on the absorption of a poorly water soluble drug. Danazol, a biopharmaceutics classification system II (BCS II) compound, was used as the model drug. Evaporative precipitation into aqueous solution (EPAS) and spray freezing into liquid (SFL) technologies were used to prepare powders of danazol/PVP K-15 in a 1:1 ratio. The evaporative precipitation into aqueous solution (EPAS) and SFL compositions, physical mixture and commercial product were dosed by oral gavage to 28 male Swiss/ICR mice for each arm of the study. Samples were taken at time points ranging from 0.5 to 24 h. Pooled mouse serum was analyzed for danazol by high performance liquid chromatography (HPLC). Powders were analyzed for their ability to form supersaturated solutions through dissolution at concentrations of 1 mg/mL which was the dose delivered to the mouse models. Spray freezing into liquid (SFL) and EPAS compositions displayed higher C(max) at 392.5 ng/mL and 430.1 ng/mL, respectively, compared to the physical mixture (204.4 ng/mL) and commercially available danazol (199.3 ng/mL). The T(max) for all compositions studied was near the 1 h time point. The area under the curve (AUC) for the SFL composition was 2558 ng.h/mL compared to EPAS composition at 1534 ng.h/mL. The area under the curve (AUC) for the physical mixture and commercially available danazol were 672 ng.h/mL and 1519 ng.h/mL, respectively. The elimination rate constants for the EPAS composition, SFL composition, and physical mixture were similar at approximately 0.15 h(-1) where as the commercially available danazol capsules displayed an elimination rate constant of 0.103 h(-1). The extent of danazol absorption in the mouse model was higher for SFL composition compared to the less amorphous EPAS composition, physical mixture, and commercially available danazol powders. Both EPAS and SFL compositions were able to form supersaturated solutions. However, the SFL composition displayed a supersaturation of 33% above control and was able to maintain supersaturation for 90 min compared to the EPAS composition (27% supersaturation above control for 60 min). Through the use of a testing method for supersaturation, it was found that EPAS and SFL compositions achieve higher apparent solubilities when compared to the physical mixture and commercially available danazol capsules. Because of the greater extent of dissolution of the SFL composition, the bioavailability was enhanced in a mouse model.

Murine airway histology and intracellular uptake of inhaled amorphous itraconazole

Aerosolization of amorphous itraconazole may be a safe and effective method of pulmonary delivery. Our objective was to evaluate the histologic effects, immunogenic potential, and cellular uptake of aerosolized amorphous itraconazole. Mice received amorphous itraconazole (30mg/kg), excipient placebo, or saline control by nebulization every 12h for up to 12 days. Broncho-alveolar lavage (BAL) and formalin fixation of both lungs were conducted. BAL supernatant was assayed for IL-12 by ELISA, and cellular components were analyzed by high performance liquid chromatography-mass spectroscopy. Coronal sections of the entire lung were stained, viewed by light microscopy, and the Cimolai histopathologic inflammatory score was obtained for each lobe. No evidence of bronchiolar, peribronchiolar or perivascular inflammation was found in any treatment group, nor were epithelial ulceration or repair observed. The Cimolai histopathologic scores for amorphous itraconazole, excipient, and saline control on days 3 and 8 did not differ between groups. ELISA analysis showed no cytokine induction of IL-12. Itraconazole was detected within cells collected from BAL fluid on days 1, 3, 8 and 12. Aerosolized administration of amorphous itraconazole or excipients does not cause inflammation or changes in pulmonary histology and are not associated with pro-inflammatory cytokine production.

Preparation of uniform prednisolone microcrystals by a controlled microprecipitation method

Prednisolone (PDL) microcrystals were successfully prepared by a controlled microprecipitation method. The characterization of PDL microcrystals by SEM and PSD indicated that the hexagonal and tetragonal PDL microcrystals with an average particle size of 1.60 and 1.46 microm could be prepared under a stirring speed of 10,000 rpm at 14 and 4 degrees C, respectively. The morphology and the particle size of PDL could be well controlled, from 1.60 to 6.12 microm for hexagonal microcrystals and 1.46 to 3.90 microm for tetragonal ones, by altering the operating parameters such as temperature, stirring speed and stabilizers. The XRD, TGA-DSC, FT-IR and physical stability studies demonstrated that the as-prepared hexagonal and tetragonal PDL microcrystals with the same pseudopolymorphic form were much more stable in water than the commercial micronized PDL with another crystal form. The dissolution tests showed that the hexagonal and tetragonal PDL microcrystals exhibited significantly enhanced dissolution property when compared to commercial micronized PDL.

Aerosolized nanostructured itraconazole as prophylaxis against invasive pulmonary aspergillosis

OBJECTIVE

Prophylactic strategies against invasive pulmonary aspergillosis are often limited by drug interactions and toxicities. Targeted airway delivery of antifungals to the lungs may avoid these pitfalls. We evaluated the effectiveness of an aerosolized nanostructured formulation of itraconazole produced by spray freezing into liquid (SFL) as prophylaxis against invasive pulmonary aspergillosis caused by A. fumigatus.

METHODS

Immunocompromised Balb/C mice received either itraconazole by oral gavage (Sporanox Oral Liquid [SOL] 30 mg/kg TID) or by aerosolization (SFL 30 mg/kg via 20 min aerosolizations, or control, BID). Dosing began 2 days prior to pulmonary inoculation with A. fumigatus and continued for 7 days post-inoculation. Changes in lung histopathology were also assessed. In the survival arm, mice were monitored over a 5 day period following discontinuation of therapy and survival was assessed by Kaplan-Meier analysis.

RESULTS

SFL survival (35%) was greater compared to control (10%; p=0.03) and SOL (0%; p=0.02). Histopathology demonstrated severe invasive disease involving vessels and small airways in control and SOL animals. SFL animals demonstrated colonization with some invasion predominately of large airways.

CONCLUSIONS

Prophylactic aerosolization of nanostructured SFL significantly improved survival and limited invasive disease of small airways due to A. fumigatus.

Stable high surface area lactate dehydrogenase particles produced by spray freezing into liquid nitrogen

Enzyme activities were determined for lactate dehydrogenase (LDH) powder produced by lyophilization, and two fast freezing processes, spray freeze-drying (SFD) and spray freezing into liquid (SFL) nitrogen. The 0.25 mg/mL LDH aqueous feed solutions included either 30 or 100 mg/mL trehalose. The SFL process produced powders with very high enzyme activities upon reconstitution, similar to lyophilization. However, the specific surface area of 13 m(2)/g for SFL was an order of magnitude larger than for lyophilization. In SFD activities were reduced in the spraying step by the long exposure to the gas-liquid interface for 0.1-1s, versus only 2 ms in SFL. The ability to produce stable high surface area submicron particles of fragile proteins such as LDH by SFL is of practical interest in protein storage and in various applications in controlled release including encapsulation into bioerodible polymers. The SFL process has been scaled down for solution volumes <1 mL to facilitate studies of therapeutic proteins.

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.

Morphology of protein particles produced by spray freezing of concentrated solutions

The mechanisms for the formation of high surface area lysozyme particles in spray freezing processes are described as a function of spray geometry and atomization, solute concentration and the calculated cooling rate. In the spray freeze-drying (SFD) process, droplets are atomized into a gas and then freeze upon contact with a liquid cryogen. In the spray freezing into liquid (SFL) process, a solution is sprayed directly into the liquid cryogen below the gas-liquid meniscus. A wide range of feed concentrations is examined for two cryogens, liquid nitrogen (LN2) and isopentane (i-C5). The particle morphologies are characterized by SEM micrographs and BET measurements of specific surface area. As a result of boiling of the cryogen (Leidenfrost effect), the cooling rate for SFL into LN2 is several orders of magnitude slower than for SFL into i-C5 and for SFD in the case of either LN2 or i-C5. For 50 mg/mL concentrated feed solutions, the slower cooling of SFL into LN2 leads to a surface area of 34 m(2)/g. For the other three cases with more rapid cooling rates, surface areas were greater than 100 m(2)/g. The ability to adjust the cooling rate to vary the final particle surface area is beneficial for designing particles for controlled release applications.

In vivo efficacy of aerosolized nanostructured itraconazole formulations for prevention of invasive pulmonary aspergillosis

Aerosolized evaporative precipitation into aqueous solution and spray freezing into liquid nanostructured formulations of itraconazole as prophylaxis significantly improved survival relative to commercial itraconazole oral solution and the control in a murine model of invasive pulmonary aspergillosis. Aerosolized administration of nanostructured formulations also achieved high lung tissue concentrations while limiting systemic exposure.

Single dose and multiple dose studies of itraconazole nanoparticles

The objective of this study was to determine and compare the lung and serum concentrations in mice following oral and pulmonary dosing of amorphous nanoparticulate itraconazole (ITZ) compositions as well as the Sporanox oral solution (itraconazole/Janssen). Second, the steady state partitioning of ITZ in lung tissue and circulatory compartments following repeated oral and pulmonary dosing was determined. The pulmonary formulation (ITZ-pulmonary) consisted of ITZ, polysorbate 80, and poloxamer 407 in a 1:0.75:0.75 ratio and the oral formulation (ITZ-oral) consisted of ITZ, PEG 8000, poloxamer 188, and sorbitan monooleate 80 in a 1:1:2:1 ratio. Mice were dosed every 12 h by nebulization with ITZ-pulmonary, or by oral gavage with ITZ-oral or Sporanox oral solution (n = 12 per study arm). ITZ-pulmonary achieved significantly greater (>10-fold) lung tissue concentrations compared to the Sporanox oral solution and ITZ-oral. There were no statistical differences between the two oral formulations. ITZ-pulmonary achieved significantly greater lung levels per unit serum concentration compared to the orally dosed ITZ compositions. High and sustained lung tissue concentrations were achieved via inhalation of an amorphous nanoparticulate ITZ-pulmonary composition while maintaining serum levels which are above the minimum lethal concentration (MLC) of Aspergillus fumigatus.

Spray freezing into liquid versus spray-freeze drying: Influence of atomization on protein aggregation and biological activity

Protein aggregation and enzyme activity were compared for reconstituted lysozyme particles produced by two cryogenic technologies, spray freezing into liquid (SFL) and spray-freeze drying (SFD). The particles were characterized by enzyme activity measurements, scanning electron microscopy (SEM), light scattering, X-ray photoelectron spectroscopy (XPS) and BET specific surface area analysis. Highly porous microparticle aggregates of protein nanoparticles, observed by SEM, were produced by both processes. The smaller degree of protein aggregation and smaller losses in enzyme activity for the SFL process relative to the SFD process were due primarily to the spraying step. The higher stability of the SFL versus SFD powders was consistent with the smaller surface excess of lysozyme measured by XPS in SFL, resulting from the reduced time of exposure to the air-water interface during atomization. For pure lysozyme, the degree of aggregation and enzyme activity were comparable for lyophilization and SFL, despite the much larger particle surface area for SFL.

Spray freeze drying to produce a stable Δ9-tetrahydrocannabinol containing inulin-based solid dispersion powder suitable for inhalation

The purpose of this study is to investigate whether spray freeze drying produces an inhalable solid dispersion powder in which Delta(9)-tetrahydrocannabinol (THC) is stabilised. Solutions of THC and inulin in a mixture of tertiary butanol (TBA) and water were spray freeze dried. Drug loads varied from 4 to 30 wt.%. Various powder characteristics of the materials were determined. Stability of THC was determined and compared with freeze dried material. The powders, dispersed with an inhaler based on air classifier technology, were subjected to laser diffraction analysis and cascade impactor analysis. Highly porous particles having large specific surface areas (about 90 m(2)/g) were produced. At high drug loads, THC was more effectively stabilised by spray freeze drying than by freeze drying. Higher cooling rates during spray freeze drying result in improved incorporation. Fine particle fractions of up to 50% were generated indicating suitability for inhalation. It was concluded that spray freeze drying from a water-TBA mixture is a suitable process to include lipophilic drugs (THC) in inulin glass matrices. High cooling rates during the freezing process result in effective stabilisation of THC. The powders can be dispersed into aerosols with a particle size appropriate for inhalation.

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.

Nanoparticle Engineering Processes for Enhancing the Dissolution Rates of Poorly Water Soluble Drugs

Poor water solubility is an industry wide issue, especially for pharmaceutical scientists in drug discovery and drug development. In recent years, nanoparticle engineering processes have become promising approaches for the enhancement of dissolution rates of poorly water soluble drugs. Nanoparticle engineering enables manufacturing of poorly water soluble drugs into nanoparticles alone, or incorporation with a combination of pharmaceutical excipients. The use of these processes has dramatically improved in vitro dissolution rates and in vivo bioavailabilities of many poorly water soluble drugs. This review highlights several commercially or potentially commercially available nanoparticle engineering processes recently reported in the literature for increasing the dissolution properties of poorly water soluble drugs.

Spray freezing into liquid nitrogen for highly stable protein nanostructured microparticles

The objectives of this study were to produce nanostructured protein microparticles with the spray freezing into liquid (SFL) cryogenic process and to demonstrate a smaller degree of protein denaturation and aggregation than observed in spray freeze drying (SFD). Nanostructured microparticles were formed by atomization of an aqueous buffer solution containing bovine serum albumin (BSA) with and without excipients beneath the surface of a cryogenic liquid. Lyophilization was used to sublime the water in the frozen particles. The resulting BSA dry powder was characterized by size exclusion chromatography, Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), light scattering, and specific surface area analysis. SEM revealed highly porous microparticle with features smaller than 500 nm. The specific surface area of the BSA microparticles ranged from 19.2 to 97.7 m(2)/g as a function of the total protein and excipient content in the aqueous feed solution. SFL produced less denaturation and aggregation of protein monomer than SFD, despite the extremely high surface areas in both processes. The intense atomization and ultra-rapid freezing in the SFL process lead to nanostructured BSA microparticles with high surface areas. Protein denaturation and aggregation are reduced in SFL relative to SFD. The more rapid freezing in SFL lowers the time for proteins to aggregate or diffuse to water-air and water-ice interfaces where they may be denatured.

Hot Air Coating Technique as a Novel Method to Produce Microparticles

In this work a new technology to produce microparticles, as well as the equipment suitable for its application, is described. This technique, called hot air coating (HAC), was developed to overcome the drawbacks of the conventional spray-congealing technique and consists of a special venturimeter, deliberately designed to prevent any hindrance along the axial path through which the powder is conveyed. In HAC technology, the raw material is a solid, generally small granules, which is aspirated through the "Venturi effect" and accelerated in a flux of hot air to soften and then to melt the excipient, especially on the particle surface. The microparticles then solidify during falling in air at room temperature. Model formulations, containing acetaminophen or theophylline as drugs and glycerilmonostearate, stearic acid, or carnauba wax as coating waxes, were tested. The choice of the optimal operating parameters was found to be a function of the formulation and of the particle size of the starting material. A pressure of 3 atm and a temperature of 20-60 degrees C above the melting point of the excipient were found generally to be the optimal parameters for the coating process. The morphology, the in vitro dissolution profile, and the possible drug/excipient interactions of formulations containing different percentages (30%, 50%, and 70% w/w) of acetaminophen were evaluated. The results show that the morphology and dissolution profiles of the microparticles were quite different from those of the starting material; in particular the best coating was achieved by microparticles lower than 500 microm. Therefore, the HAC process could be a viable alternative to the conventional spray-congealing technique to produce microparticles with a high drug content.

The role of particle engineering in relation to formulation and de-agglomeration principle in the development of a dry powder formulation for inhalation of cetrorelix

We formulated cetrorelix acetate, as an adhesive mixture for use in dry powder inhalation. To achieve the highest possible deposition efficiency we investigated both the influence of different micronization techniques and different inhalers. The Novolizer with an air classifier as the powder de-agglomeration principle and the ISF inhaler were used for in vitro deposition experiments (cascade impaction). Micronization by milling as the classical approach and micronization by spray drying and spray freeze drying as advanced particle engineering techniques were investigated to determine whether advanced techniques are necessary to obtain high fine particle fractions (FPF) for this specific drug. It was found that the effects obtained with a certain micronization technique depended on the complex interaction of the physical characteristics of the drug substance with the type of formulation chosen, as well as with the de-agglomeration principle used. The combination of particle engineering by spray drying and the use of the air classifier technology resulted in a fine particle fraction of 66%, while spray freeze drying yielded extremely fragile particles resulting in a FPF of only 25%. The behaviour of the milled material showed similar trends as the spray dried material but FPF values were lower. It was concluded that when a drug is to be formulated as a powder for inhalation with high fine particle fractions, it is profitable to use advanced particle engineering techniques, however the applied technique should be tuned with the characteristics of the formulation type and process as well as with device development.

Micron-size drug particles: common and novel micronization techniques

Drug powders containing micron-size drug particles are used in several pharmaceutical dosage forms. Many drugs, especially newly developed substances, are poorly water soluble, which limits their oral bioavailability. The dissolution rate can be enhanced by using micronized drugs. Small drug particles are also required in administration forms, which require the drug in micron-size size due to geometric reasons in the organ to be targeted (e.g., drugs for pulmonary use). The common technique for the preparation of micron-size drugs is the mechanical comminution (e.g., by crushing, grinding, and milling) of previously formed larger particles. In spite of the widespread use of this technique, the milling process does not represent the ideal way for the production of small particles because drug substance properties and surface properties are altered in a mainly uncontrolled manner. Thus, techniques that prepare the drug directly in the required particle size are of interest. Because physicochemical drug powder properties are decisive for the manufacturing of a dosage form and for therapeutic success, the characterization of the particle surface and powder properties plays an important role. This article summarizes common and novel techniques for the production of a drug in small particle size. The properties of the resulting products that are obtained by different techniques are characterized and compared.

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.

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.

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.

Sustained release of ascorbate-2-phosphate and dexamethasone from porous PLGA scaffolds for bone tissue engineering using mesenchymal stem cells

The purpose of this research was to develop porous poly(D,L-lactide-co-glycolide) (PLGA) scaffolds from which ascorbate-2-phosphate (AsAP) and dexamethasone (Dex) are continuously released for a month for osteogenesis of mesenchymal stem cells for bone tissue engineering. Porous PLGA matrices containing AsAP and Dex were prepared by solvent casting/particulate leaching method. In vitro release and water uptake studies were performed in Dulbecco's phosphate buffered saline at 37 degrees C and 15 rpm. Drug loading and release rates were determined by high performance liquid chromatography. Release studies of Dex and AsAP showed that, after an initial burst release lasting 4 and 9 days, respectively, release rates followed zero order kinetics with high correlation coefficients at least until 35 days. Incorporation of AsAP into the scaffolds increased the release rates of Dex and AsAP, and the scaffold water uptake. When mesenchymal stem cells (MSCs) were cultured in the AsAP and Dex containing scaffolds in vitro, the amount of mineralization was significantly higher than in control scaffolds. In conclusion, AsAP and Dex were incorporated into porous PLGA scaffolds and continuously released over a month and osteogenesis of MSCs was increased by culture in these scaffolds.

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.

METHOD

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.

Investigation of processing parameters of spray freezing into liquid to prepare polyethylene glycol polymeric particles for drug delivery

The objective of this study was to investigate the influence of processing parameters on the morphology, porosity, and crystallinity of polymeric polyethylene glycol (PEG) microparticles by spray freezing into liquid (SFL), a new particle engineering technology. Processing parameters investigated were the viscosity and flow rate of the polymer solution, nozzle diameter, spray time, pressure, temperature, and flow rate of the cryogenic liquid. By varying the processing parameters and feed composition, atomization and heat transfer mechanisms were modified resulting in particles of different size distribution, shape, morphology, density, porosity, and crystallinity. Median particle diameter (M50) varied from 25 microm to 600 microm. Particle shape was spherical or elongated with highly irregular surfaces. Granule density was between 0.5 and 1.5 g/mL. In addition to producing particles of pure polymer, drug particles were encapsulated in polymeric microparticles. The encapsulation efficiency of albuterol sulfate was 96.0% with a drug loading of 2.4%, indicating that SFL is useful for producing polymeric microparticles for drug delivery applications. It was determined that the physicochemical characteristics of model polymeric microparticles composed of PEG could be modified for use as a drug delivery carrier.