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PubMed2002

Trojan particles: large porous carriers of nanoparticles for drug delivery.

We have combined the drug release and delivery potential of nanoparticle (NP) systems with the ease of flow, processing, and aerosolization potential of large porous particle (LPP) systems by spray drying solutions of polymeric and nonpolymeric NPs into extremely thin-walled macroscale structures. These hybrid LPPs exhibit much better flow and aerosolization properties than the NPs; yet, unlike the LPPs, which dissolve in physiological conditions to produce molecular constituents, the hybrid LPPs dissolve to produce NPs, with the drug release and delivery advantages associated with NP delivery systems. Formation of the large porous NP (LPNP) aggregates occurs via a spray-drying process that ensures the drying time of the sprayed droplet is sufficiently shorter than the characteristic time for redistribution of NPs by diffusion within the drying droplet, implying a local Peclet number much greater than unity. Additional control over LPNPs physical characteristics is achieved by adding other components to the spray-dried solutions, including sugars, lipids, polymers, and proteins. The ability to produce LPNPs appears to be largely independent of molecular component type as well as the size or chemical nature of the NPs.

Biocompatible Materials↗
PubMed2006

Improvement of bioavailability and photostability of amlodipine using redispersible dry emulsion.

To improve the bioavailability and photostability of poorly water-soluble and photosensitive amlodipine, dry emulsion (DE) was prepared by spray-drying the oil-in-water emulsion of amlodipine. Labrafil M 1944 CS and dextrin were employed as oil phase and matrix material, respectively. Dispersing DE in distilled water formed an emulsion with a mean droplet size 1.4-fold larger than that of the homogenized amlodipine emulsion before spray-drying (0.24 +/- 0.30 microm versus 0.17 +/- 0.02 microm). The mean droplet size of DE remained unchanged during 6-month storage at room temperature. 94.4% versus 33.1% of amlodipine remained intact after 24-h UV irradiation of amlodipine as DE formulation or as powder. These data suggest that DE formulation greatly improved the photostability of amlodipine, as well as increasing the physical stability of emulsion systems. In vitro release of DE was higher than that of amlodipine powder (66% versus 48% release at 60 min). Consequently, DE formulation resulted in 2.6- and 2.9-fold higher Cmax and AUC0-24 h of amlodipine compared after oral administration of amlodipine powder in rats. Our data suggest that the DE may be a potential oral dosage form for amlodipine to improve its bioavailability.

Amlodipine↗
PubMed2001

Survival rate of preserved cultures contained in baker's vaccine.

The studies comprised the preparation and preservation, by the method of spray-drying, of baker's vaccine composed of lactic acid bacteria. The selection of particular strains was conducted taking into consideration the fermentation activity and growth dynamics of Lactobacillus rods isolated from plant material. Mixed vaccine was composed of chosen monocultures, characterized by the highest acidifying activity (4 strains). Before the vaccine was preserved, it had been used for making bread leaven (of rye flour) whose activity and usefulness for rye bread production was then determined The vaccine was subjected to spray-drying. The survival rate of Lactobacillus rods was determined directly after drying and during storage. It was found that the parameters of spray-drying applied in the experiment caused a considerable reduction in the number of vaccine components--by 2 log on average.

Colony Count, Microbial↗
PubMed1999

Immunogenicity of single-dose diphtheria vaccines based on PLA/PLGA microspheres in guinea pigs.

Biodegradable polyester microspheres (MS) have shown potential for single-dose vaccines. This study examined the immunogenicity of diphtheria toxoid (Dtxd) microencapsulated in different types of poly(lactide) (PLA) and poly(lactide-co-glycolide) (PLGA) MS prepared by the methods of spray-drying and coacervation. We investigated the influence of polymer type (PLGA 50:50 of low M(w); PLA of high M(w); end-group stearylated PLAs of low M(w)) and co-encapsulated excipients (BSA and/or trehalose) on Dtxd content, in vitro release and immunogenicity in guinea pigs. The co-encapsulated trehalose lowered the Dtxd entrapment efficiency in the spray-dried particles from 75 to 56%, whereas albumin alone had no effect in the spray-drying, but improved the encapsulation in the coacervation process. With the hydrophobic, end-group stearylated PLAs, Dtxd could only be encapsulated in the presence of albumin. Guinea pigs immunised with Dtxd-MS made with the relatively hydrophilic PLGA 50:50 exhibited specific and sustained antibody responses over 40 weeks, comparable to the responses to alum-adjuvanted toxoid. In contrast, undetectable or very low antibody responses were determined after immunisation with MS made with hydrophobic polymers. Surprisingly, large (15-60 microm) and small (1-5 microm) MS gave comparable primary antibody responses. In conclusion, the data presented confirm the feasibility of MS vaccines to induce strong, long-lasting protective antibody responses after a single immunisation.

Animals↗
PubMed2006

In vivo performance of implantable biodegradable preparations delivering Paclitaxel and Etanidazole for the treatment of glioma.

Drug-releasing implants delivering chemotherapeutic and radio-sensitizing agents are beginning to play a major role in the post-surgical eradication of residual glioma in the brain. Benefits from early arresting of tumor growth and tumor recovery dynamics stress the impact of drug release profiles of the implants on the efficacy of the treatment. This paper examines responses of BALB/c nude mice, bearing C6 glioma tumors subcutaneously, to treatments by PLGA microspheres, microparticles and discs-delivering Paclitaxel and Etanidazole. The experimental results are used to correlate the efficacy of treatment to in vitro release profiles from the various formulations. Our study demonstrates that radio-sensitizing effects during irradiation could be achieved by double burst profiles from Etanidazole-loaded discs, when compared to controls 17 days after implantation despite the short half-life of Etanidazole (1.4h) in vivo. These results also showed inhibited tumor growth on tumor volumes of 59%, 65% and 70% over the blank placebo groups after 21 days of tumor growth for spray-dried microspheres, electrohydrodynamic atomization microparticles and spray-dried discs, respectively.

Animals↗
PubMed2002

Alginate microparticles for enzyme peroral administration.

In order to protect protein and peptide drugs against inactivation by different barriers in the gastro-intestinal tract and to improve their absorption, alginate microparticles as a carrier of L-lactate dehydrogenase, were developed by spray-drying technique. However, alginate complexation and spray-drying conditions led to enzyme activity loss. Such a drawback was overcome by using protectant additives (carboxymethylcellulose sodium salt, polyacrylic acid sodium salt, lactose) preventing the enzyme inactivation by both interaction with alginate and experimental conditions, lactose having the most protective effect. Nevertheless, only polyacrylic acid sodium salt provided a microparticulate structure required for the target of the Peyer's patches.

Alginates↗
PubMed1996

Morphological characterization of polyanhydride biodegradable implant gliadel during in vitro and in vivo erosion using scanning electron microscopy.

PURPOSE: The objectives of the current study are to characterize the distribution of the chemotherapeutic agent carmustine (BCNU) in spray dried polyanhydride microspheres and to describe the morphological changes that occur during the in vitro and in vivo erosion of the polyanhydride implant--GLIADEL, which consists of BCNU distributed in the copolymer matrix of poly(carboxyphenoxy propane:sebacic acid) in a 20:80 molar ratio (p(CPP:SA, 20:80)). METHODS: Scanning electron microscopy (SEM) was used to visualize the morphological changes of the polymer during the manufacturing process and in vitro and in vivo erosion. RESULTS: This study revealed that BCNU was homogeneously distributed within spray dried polyanhydride microspheres with no phase separation. The porosity of the wafer fabricated from spray dried polyanhydride microspheres gradually increased during erosion. During the initial period following wafer implantation in the brains of rats, erosion was mainly confined to the surface layer of the wafer with the majority of the wafer remaining intact. The eroding front gradually advanced from the surface to the interior of the wafer in a layerwise fashion, creating pores and connecting channel. Eventually both the interior and exterior of the wafers were eroded and the same porous structure was seen throughout the whole wafer. CONCLUSIONS: This study provides the first visual observation of the morphological changes of the GLIADEL(R) wafer during erosion of the polyanhydride matrix and release of the drug substance BCNU. The observations in this study support the conclusion that BCNU release from a polyanhydride wafer is controlled both by diffusion of the drug and erosion of the polymer matrix.

Anhydrides↗
PubMed2001

Evaluation of microencapsulation of a Bifidobacterium strain with starch as an approach to prolonging viability during storage.

AIMS: To optimize a spray coating process for the production of encapsulated microspheres containing viable Bifidobacterium cells and to determine whether the readily gelatinized modified starch coating used in this study improved bacterial survival in foods or under acid conditions. METHODS AND RESULTS: An air inlet temperature of 100 degrees C was demonstrated to be optimal for the spray drying process, as it afforded good drying, low outlet temperatures (45 degrees C) and resulted in less than 1 log reduction in bifidobacteria numbers during drying. Maximum recovery yields of 30% were obtained after optimizing the air aspiration conditions. The average size of the Bifidobacterium PL1-containing starch microparticles was determined by scanning electron microscopy to be of the order of 5 microm. The starch-coated cells did not display any enhanced viability compared with free PL1 cells when exposed to acid conditions for 6 h or in two dry food preparations over 20 d storage at ambient temperature (19-24 degrees C). Determination of 1491 nucleotides of the 16S rRNA gene from PL1 indicated that it shared 97% homology with a previously sequenced Bifidobacterium ruminantium strain. CONCLUSIONS: Our data demonstrated that, although spray drying is a valuable process for encapsulating bifidobacteria, further work is required to ascertain a more appropriate coating material that will protect this strain against adverse environmental conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The production of small, uniformly coated microspheres containing viable bifidobacteria using an affordable and industrially convenient process, such as spray drying, has commercial implications for the production of probiotic products. Although popular for use as a coating polymer by the food industry, this study indicated that modified starches might not be suitable for use as an encapsulating material for probiotic strains.

Aerosol Propellants↗
PubMedDate not supplied

Nano-liposomal dry powder inhaler of Amiloride Hydrochloride.

The purpose of this study was to encapsulate Amiloride Hydrochloride into nano-liposomes, incorporate it into dry powder inhaler, and to provide prolonged effective concentration in airways to enhance mucociliary clearance and prevent secondary infection in cystic fibrosis. Liposomes were prepared by thin film hydration technique and then dispersion was passed through high pressure homogenizer to achieve size of nanometer range. Nano-liposomes were separated by centrifugation and were characterized. They were dispersed in phosphate buffer saline pH 7.4 containing carriers (lactose/sucrose/mannitol), and glycine as anti-adherent. The resultant dispersion was spray dried. The spray dried powders were characterized and in vitro drug release studies were performed using phosphate buffer saline pH 7.4. In vitro and in vivo drug pulmonary deposition was carried out using Andersen Cascade Impactor and by estimating drug in bronchial alveolar lavage and lung homogenate after intratracheal instillation in rats respectively. Nano-liposomes were found to have mean volume diameter of 198 +/- 15 nm, and 57% +/- 1.9% of drug entrapment. Mannitol based formulation was found to have low density, good flowability, particle size of 6.7 +/- 0.6 microm determined by Malvern MasterSizer, maximum fine particle fraction of 67.6 +/- 0.6%, mean mass aerodynamic diameter 2.3 +/- 0.1 microm, and geometric standard deviation 2.4 +/- 0.1. Developed formulations were found to have prolonged drug release following Higuchi's Controlled Release model and in vivo studies showed maximal retention time of drug of 12 hrs within the lungs and slow clearance from the lungs. This study provides a practical approach for direct lung delivery of Amiloride Hydrochloride encapsulated in liposomes for controlled and prolonged retention at the site of action from dry powder inhaler. It can provide a promising alternative to the presently available nebulizers in terms of prolonged pharmacological effect, reducing systemic side effects such as potassium retention due to rapid clearance of the drug from lungs in patients suffering from cystic fibrosis.

Administration, Inhalation↗
PubMed2004

Biodegradable PLGA microparticles for sustained release of a new GnRH antagonist: part II. In vivo performance.

Poly (DL-lactide-co-glycolide) microparticles (MP) containing a highly potent peptidic gonadotropin releasing hormone antagonist (degarelix) of interest in the prostate cancer indication were screened for biological performance. Efficacy was tested in a castrated male rat model at 3 doses (0.4, 1.0 and 1.5 mg/kg) and assessed as inhibition of luteinizing hormone (LH) secretion. When increasing the dose, onset of inhibition was faster, inhibition was more intense, and duration of action was prolonged. The MP type was also highly influent. If spray-dried and microextrusion particles exhibited comparable potencies, double emulsion microspheres were significantly less potent, both for onset and duration of inhibition. Interestingly, for the latter type it was found that the degarelix fraction released upon reconstitution in the solution for injection was significantly lower (max 0.3%), in comparison to spray-dried MP (max 2%) or microextrusion (max 4%). With the three types of particles, increasing peptide content was detrimental for duration of action, but only little difference was noticed between particles based on different polymers. At 1.5 mg/kg, LH inhibition was achieved over 36 days with spray-dried MP based on 75/25 lactate/glycolate copolymer. This was superior by 1 week to the performance of unformulated degarelix given at the same dose.

Animals↗
PubMed2006

Dry powder aerosol delivery of large hollow nanoparticulate aggregates as prospective carriers of nanoparticulate drugs: effects of phospholipids.

The present work details the effects of incorporating phospholipids, a major component of lung surfactants, in the formulation of large hollow nanoparticulate aggregates, which are specifically designed to serve as potential carrier particles in inhaled delivery of nanoparticulate drugs. The large hollow aerosol particles (d(g) approximately 10 microm), whose shells are composed of nanoparticulate aggregates, are manufactured via the spray drying of nanoparticulate suspensions under a predetermined operating condition. Polyacrylate and silica nanoparticles of various sizes (20-170 nm), without loaded drugs, are employed as the model nanoparticles. The effects of increasing the phospholipids concentration in the presence of the nanoparticles, and vice versa, on the degree of hollowness and morphology of the spray-dried particles are investigated. Varying the phospholipids concentration in the presence of a constant amount of nanoparticles is found to influence the degree of hollowness, without significantly affecting the particle size distribution and respirable fine particle fraction, of the aerosol particles. The effects of increasing the phospholipids concentration on the degree of hollowness of the spray-dried particles are found to depend on the size and chemical nature of the nanoparticles.

Acrylates↗
PubMed1978

Effects of processing and cooking on PBB residues.

To study the effect of processing on polybrominated biphenyl (PBB) levels, milk from four dairy herds containing less than 0.3 ppm (fat basis) of physiologically incorporated PBBs was presented individually into cream, skim milk, butter, and stirred curd cheese. Pasteurized and freeze-dried whole milk, skim milk, and cream, spray-dried whole milk and skim milk, and condensed whole milk were also made. PBBs were concentrated in the high-fat products. Spray-drying reduced PBBs in whole milk and skim milk while pasteurization, freeze-drying, aging of cheese, and condensation were not effective. To study the effect of cooking on PBB levels, thigh meat, thigh skin, drumstick and breast (with skin) from half of chickens fed PBBs were analyzed raw, and pieces from the other halves were analysed following separate pressure cooking. The level of PBBs expressed as parts per million on a solids basis was lower in the cooked sample than in the corresponding raw piece and part of the PBBs lost were found in the drip. Recoveries of PBBs in cooked tissue and broth ranged from 68.1% in the thigh skin to 84.6% in the drumstick, with approximately two-thirds of the recovered PBBs found in the cooked meat itself. Therefore, pressure cooking resulted in a loss ranging from 36% for the drumstick to 53% for the thigh skin.

Animals↗
PubMed1998

In vitro degradation study of polyester microspheres by a new HPLC method for monomer release determination.

Biodegradable polyesters have increasing importance as materials used for the preparation of microspheres. The knowledge of their degradation process is important to prepare microparticulate delivery systems with suitable drug release rates. In this work an in vitro degradation study of empty and drug loaded microspheres is described. Three different polyesters were used: two poly-d, l-lactides of different molecular weight and a poly-d, l-lactide-co-glycolide (50:50). Diazepam has been chosen as the model drug. Solvent evaporation and spray-drying were used as preparation methods. To study the polymer degradation process, a new HPLC method is proposed for the direct and (in the case of the copolymer) simultaneous determination of the monomer(s): lactic acid (LA) and glycolic acid (GA). SEM and particle size analysis highlight the different characteristics of the particles, depending on their preparation method: spray-dried spheres result to be always smaller with respect to particles obtained by solvent evaporation. The results obtained indicate in particular that: the preparation methods play an important role in determining the degradation behaviour of microspheres, as unloaded spray-dried particles are characterized by a higher monomer release rate with respect to microspheres obtained by solvent evaporation; PLGA spheres degrade faster than PDLLA microparticles, according to the higher hydrophilicity of the copolymer; the two monomers are released at a different rate in the case of PLGA (faster for GA, slower for LA); the presence of diazepam increases the polymer degradation rate, with respect to empty particles.

Biocompatible Materials↗
PubMed2004

Visualization of the crystallization of lactose from the amorphous state.

The physical stability and solid-state recrystallization of spray-dried 'amorphous' lactose particles were visualized using environmentally controlled atomic force microscopy (EC-AFM) and conventional optical microscopy. The morphology and crystalline state were investigated as a function of relative humidity (RH) and were correlated with bulk gravimetric vapor sorption measurements that were run in parallel. The metastable nature of amorphous spray-dried lactose particles was apparent at low RHs (<30% RH). Visualization of the recrystallization transformation of amorphous lactose during moisture uptake at 58 and 75% RH suggested only a proportion of the collapsed particles undergoes nucleation and crystal growth. The irregular surface morphology of the recrystallized particles suggested a secondary nucleation and growth process. Primary nucleation of alpha-lactose monohydrate within the non-recrystallized particles required exposure to elevated RH (94% RH). In relation to bulk measurements of moisture-induced amorphous recrystallization of spray-dried lactose, the results suggest that recrystallization of amorphous lactose, above a critical RH, may be induced by the presence of very low levels of a seed material, which may dramatically reduce the activation energy barrier for nucleation and crystal growth.

Crystallization↗
PubMed1992

Solubility and digestibility of milk proteins in infant formulas exposed to different heat treatments.

There are presently several fundamentally different technologies to produce infant formulas (IF), such as sterilization, spray-drying, and treatment at ultrahigh temperature (UHT). The effects of heat treatment on milk proteins in IF were analyzed by column chromatography, gel electrophoresis, and Kjeldahl analysis, revealing strong protein-protein and protein-lipid interactions in processed milk. These interactions were more pronounced in conventionally (in-can) sterilized than in spray-dried (powdered) and UHT products confirming their temperature dependency. Analysis of raw materials, intermediate and end products of IF processing revealed that after homogenization the first indications of protein denaturation occurred, but that in-can sterilization as the final heat treatment caused irreversible denaturation of proteins and strong protein-lipid interactions. Lowering of the pH to 4-5, which is physiological for the stomach of young infants, enhanced the interactions. Support for an impairment of protein digestibility was given by in vitro analysis of protein digestibility, demonstrating significantly lower digestibility of in-can sterilized IF compared to their spray-dried and UHT counterparts. To investigate the effect of heat treatment on chemical reactions, i.e., occurrence of Maillard products, we showed by a fluorimetric assay that the amount of "available" lysine is lower in sterilized than in powdered IF. Our findings suggest that a more differentiated view regarding the protein quality of IF is needed.

Animals↗
PubMed1977

Polybrominated biphenyls in raw milk and processed dairy products.

Milk from four dairy herds identified by the Michigan Department of Agriculture as containing less than .3 ppm (fat basis) physiologically incorporated polybrominated biphenyls was processed individually into cream, skim milk, butter, and stirred curd cheese. Pasteurized and freeze-dried whole milk, skim milk, and cream, spray-dried whole milk and skim milk, and condensed whole milk were made also. Polybrominated biphenyls were concentrated in the high-fat products. Pasteurized skim milk, buttermilk, and whey had slightly more polybrominated biphenyls than pasteurized whole milk on a fat basis. Spray-drying reduced the polybrominated biphenyls in whole milk and skim milk while pasteurization, freeze-drying, aging of cheese, and condensation were not effective.

Animals↗
PubMed1999

Effects of the host cavity size and the preparation method on the physicochemical properties of ibuproxam-cyclodextrin systems.

The effect of cyclodextrin (Cd) complexation on ibuproxam (IBUX) dissolution properties was studied by evaluating both the influence of Cd cavity size and the preparation method used for obtaining solid inclusion complexes. Binary systems of IBUX with natural Cds, prepared using different techniques (kneading, sealed-heating, spray-drying), were studied by differential scanning calorimetry (DSC), hot-stage microscopy (HSM), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and their dissolution behavior was evaluated according to the dispersed amount method. The nature and the dissolution performance of the end product appeared to be related to both steric factors of host molecule and preparation method of the solid system. The alpha Cd cavity size was less suitable for accommodating the IBUX molecule, whereas spray-drying and sealed-heating methods led to a true inclusion complex of IBUX in the beta Cd and gamma Cd cavity. In contrast, the kneading method did not lead in any case to a real inclusion complex. Spray-dried systems with beta Cd and gamma Cd were the most effective in achieving the enhancement of the IBUX dissolution rate.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

The preparation of soft gelatin capsules for a radioactive tracer study.

Clinical doses are developed for the oral coadministration of radiolabeled and nonlabeled forms of a poorly soluble investigational compound: OPC-41061. The release rates of the labeled and nonlabeled forms are equated and matched to the release rate of the polymer spray-dried form of the drug in the proposed market product. The study involves the physicochemical characterization of the powders using thermal analysis and dissolution testing, development and extemporaneous manufacture of liquid-filled soft gelatin capsules, and dissolution and stability testing of the final dosage form. Thermal analysis indicated that the labeled powder was amorphous and that the nonlabeled powder, which had been jet-milled, was crystalline. Dissolution testing of the jet-milled and spray-dried powders indicated that the former was released at a significantly slower rate. A liquid formulation containing 25% dimethyl acetamide and 75% polyethylene glycol 400 (PEG 400) solubilized the desired dose of 60 mg and exhibited a drug profile that was similar to the spray-dried formulation. The final formulation was a soft gelatin capsule containing 60 mg of drug, including 100 microCi radioactivity, dissolved in 0.8 ml of a 25% dimethyl acetamide/75% PEG 400 solution. The formulation was chemically and physically stable for a period greater than the duration of the study.

Benzazepines↗