Scale-up and optimization of an evaporative drying process applied to aqueous dispersions of solid lipid nanoparticles

An apparatus to dry aqueous dispersions of solid lipid nanoparticles (SLNs) was designed. Optimal running conditions were evaluated to obtain minimum process time and produce dried SLNs characterized by small size variation. To achieve process optimization, SLN average diameter, SLNs polydispersity index, and drying time were related to three operative variables: process temperature, SLN concentration in the original aqueous dispersions, and nitrogen flow rate as the physical means of the drying process. An experimental design procedure and a multicriteria optimization method, targeting desirability functions, enabled us to obtain the optimal conditions for all responses. Drying time, average diameter, and polydispersity index of dried SLN batches were more favorable than those obtained by freeze-drying identical SLN aqueous dispersions with the same initial nanoparticle concentration.     

Flocculated Amorphous Nanoparticles for Highly Supersaturated Solutions

Purpose  To recover polymer-stabilized amorphous nanoparticles from aqueous dispersions efficiently by salt flocculation and to show that the particles redisperse and dissolve rapidly to produce highly supersaturated solutions. Methods  Nanoparticle dispersions of itraconazole stabilized by nonionic polymers were formed by antisolvent precipitation and immediately flocculated with sodium sulfate, filtered and dried. The size after redispersion in water, crystallinity, and morphology were compared with those for particles produced by spray drying and rapid freezing. Results  Particle drug loading increased to ∼90% after salt flocculation and removal of excess polymer with the filtrate. The formation of the flocs at constant particle volume fraction led to low fractal dimensions (open flocs), which facilitated redispersion in water to the original primary particle size of ∼300 nm. Amorphous particles, which were preserved throughout the flocculation–filtration–drying process, dissolved to supersaturation levels of up to 14 in pH 6.8 media. In contrast, both spray dried and rapidly frozen nanoparticle dispersions crystallized and did not produce submicron particle dispersions upon addition to water, nor high supersaturation values. Conclusions  Salt flocculation produces large yields of high surface area amorphous nanoparticle powders that de-aggregate and dissolve rapidly upon redispersion in pH 6.8 media, for supersaturation levels up to 14.     

Aerosol Delivery of Nanoparticles in Uniform Mannitol Carriers Formulated by Ultrasonic Spray Freeze Drying

Purpose

While most examples of nanoparticle therapeutics have involved parenteral or IV administration, pulmonary delivery is an attractive alternative, especially to target and treat local infections and diseases of the lungs. We describe a successful dry powder formulation which is capable of delivering nanoparticles to the lungs with good aerosolization properties, high loadings of nanoparticles, and limited irreversible aggregation.

Methods

Aerosolizable mannitol carrier particles that encapsulate nanoparticles with dense PEG coatings were prepared by a combination of ultrasonic atomization and spray freeze drying. This process was contrasted to particle formation by conventional spray drying.

Results

Spray freeze drying a solution of nanoparticles and mannitol (2 wt% solids) resulted in particles with an average diameter of 21?±?1.7 μm, regardless of the fraction of nanoparticles loaded (0–50% of total solids). Spray freeze dried (SFD) powders with a 50% nanoparticle loading had a fine particle fraction (FPF) of 60%. After formulation in a mannitol matrix, nanoparticles redispersed in water to < 1 μm with hand agitation and to < 250 nm with the aid of sonication. Powder production by spray drying was less successful, with low powder yields and extensive, irreversible aggregation of nanoparticles evident upon rehydration.

Conclusions

This study reveals the unique advantages of processing by ultrasonic spray freeze drying to produce aerosol dry powders with controlled properties for the delivery of therapeutic nanoparticles to the lungs.     

Effervescent dry powder for respiratory drug delivery.

The objective of this work was to develop a new type of respiratory drug delivery carrier particle that incorporates an active release mechanism. Spray drying was used to manufacture inhalable powders containing polybutylcyanoacrylate nanoparticles and ciprofloxacin as model substances for pulmonary delivery. The carrier particles incorporated effervescent technology, thereby adding an active release mechanism to their pulmonary route of administration. Effervescent activity of the carrier particles was observed when the carrier particles were exposed to humidity. Gas bubbles caused by the effervescent reaction were visualized by confocal laser scanning microscopy. The images showed that nanoparticles were distributed throughout the gas bubble. For the effervescent formulation the average mass median aerodynamic diameter (MMAD) was 2.17 microm+/-0.42, fine particle fraction (FPF(<=5.6 microm)) was 46.47%+/-15 and the GSD was 2.00+/-0.06. The results also showed that the effervescent carrier particles released 56+/-8% ciprofloxacin into solution compared with 32+/-3% when lactose carrier particles were used. The mean nanoparticle size did not significantly change upon release when the nanoparticles were incorporated into an effervescent formulation. However, the mean size significantly increased upon release when only lactose was used as carrier particle matrix. In conclusion, effervescent carrier particles can be synthesized with an adequate particle size for deep lung deposition. This opens the door for future research to explore this technology for delivery of a large range of substances to the lungs with possible improved release compared to conventional carrier particles.     

Nanoparticle aerosol generation methods from bulk powders for inhalation exposure studies

Abstract

Inhalation toxicity studies of nanoparticles require production of test aerosols with a number of acceptable characteristics. Five different generation methods for producing a nanoparticle aerosol from the bulk powder were evaluated with the goal of producing an acceptable aerosol that is homogenous, has a consistent concentration over time in which the magnitude may be intentionally varied, and has a size distribution that is both unimodal and has a small geometric mean diameter relative to the primary particle size of the nanoparticle bulk powder. Four types of bulk powders were evaluated including titanium dioxide, silicon dioxide, polymer-coated silver, and single walled carbon nanotubes. A nebulizer was the only tested method able to produce a consistent aerosol of sufficient magnitude. However, the resulting aerosol contains particles derived from the carrier water. Prior sonication of the nanoparticle suspension alone was found to be not useful for deagglomerating nanoparticles.     

Formulation and characterization of clozapine and risperidone co-entrapped spray-dried PLGA nanoparticles

In the current study, polylactide-co-glycolide (PLGA) nanoparticles entrapping both clozapine (CLZ) and risperidone (RIS) were formulated by spray-drying using Buchi Nano Spray Dryer B-90 (Flawil, Switzerland). Parameters such as inlet temperature, spray mesh diameter, sample flow rate, spray rate and applied pressure were optimized to produce nanoparticles having desired release profile using both low- and high-molecular weight PLGA polymer. Smallest size nanoparticle of size around 248?nm could be prepared using a 4.0 μm mesh diameter with low-molecular weight polymer. The load of CLZ and RIS was 126.3 and 58.2?μg/mg of polymer particles, respectively. Entrapment efficiency of drugs in PLGA nanoparticles was 94.74% for CLZ and 93.12% for RIS. Both the drugs released continuously from the nanoparticle formulations. PLGA nanoparticles formulated using low-molecular weight polymer released around 80% of the entrapped drug over 10 days of time. Nature of drug inside polymer particles was amorphous, and there was no chemical interaction of CLZ and RIS with polymer. Polymeric nanoparticles were found to be non-toxic in nature using PC12 cell line. This nanospray drying process proved to be suitable for developing polymeric nanoformulation delivering dual drugs for the treatment of Schizophrenia.     

Cryoprotectant choice and analyses of freeze-drying drug suspension of nanoparticles with functional stabilisers

Freeze-drying is an effective way to improve long-term physical stability of nanosuspension in drug delivery applications. Nanosuspension also known as suspension of nanoparticles. In this study, the effect of freeze-drying with different cryoprotectants on the physicochemical characteristics of resveratrol (RSV) nanosuspension and quercetin (QUE) nanosuspension was evaluated. D-α-tocopheryl polyethylene glycol succinate (TPGS) and folate-modified distearoylphosphatidyl ethanolamine-polyethylene glycol (DSPE-PEG-FA) were selected as functional stabilisers formulated nanosuspension which were prepared by anti-solvent precipitation method. RSV nanoparticle size and QUE nanoparticle size were about 210 and 110?nm, respectively. The AFM and TEM results of nanosuspension showed uniform and irregular shape particles. After freeze-drying, the optimal concentration of four cryoprotectants was determined by the particle size of re-dispersed nanoparticles. The dissolution profile of drug nanoparticle significantly showed approximately at a 6–8-fold increase dissolution rate. Moreover, TPGS and DSPE-PEG-FA stabilised RSV nanosuspension and QUE nanosuspension samples showed better effect on long-term physical stability.     

Effect of conditions of preparation on the size and encapsulation properties of PLGA-mPEG nanoparticles of cisplatin

The effect of conditions of preparation on the size and encapsulation properties of PLGA-mPEG nanoparticles of cisplatin was investigated. A modified double emulsion method was applied for the preparation of PLGAmPEG nanoparticles of cisplatin, based on the partial or complete replacement of the water of the inner aqueous phase of the emulsion by dimethyl formamide(dmf) or the addition of cisplatin in the form of a complex with poly(glutamic acid). These modifications resulted in significant improvement of cisplatin loading in the PLGA-mPEG nanoparticles. Increased cisplatin loading and encapsulation efficiency were obtained when a relatively low dmf/water ratio, low dmf volume (when pure dmf formed the inner polar phase), or a high drug/polymer ratio were applied. A reduction of average size of nanoparticles was observed with decreasing the amount of PLGA-mPEG added in the formulation or increasing sonication time. The only factor that had a significant effect on size distribution was the sonication time, with the size P.I. being decreased with increasing sonication time. Prolonged sonication, however, decreased cisplatin loading and encapsulation efficiency. From the four lyoprotectant sugars tested (glucose, lactose, mannitol, and trehalose), only mannitol could prevent nanoparticle aggregation upon lyophilization. When appropriate amounts of an effective lyoprotectant were added in nanoparticles before lyophilization, drug loading of the nanoparticles was not affected by nanoparticle lyophilization.     

Preparation of amorphous cefuroxime axetil nanoparticles by sonoprecipitation for enhancement of bioavailability.

The aim of the present work was to prepare amorphous discreet nanoparticles by sonoprecipitation method for enhancing oral bioavailability of cefuroxime axetil (CA), a poorly water-soluble drug. CA nanoparticles (SONO-CA) were prepared by sonoprecipitation and compared with particles obtained by precipitation without sonication (PPT-CA) and amorphous CA obtained by spray drying. Spray drying present broad particle size distribution (PSD) with mean particle size of 10mum and low percent yield, whereas, precipitation without sonication resulted in large amorphous aggregates with broad PSD. During sonoprecipitation, particle size and yield improve with an increase in the amplitude of sonication and lowering the operation temperature due to instantaneous supersaturation and nucleation. The overall symmetry and purity of CA molecule was maintained as confirmed by FTIR and HPLC, respectively. All the three methods resulted in the formation of amorphous CA with only sonoprecipitation resulting in uniform sized nanoparticles. Sonoprecipitated CA nanoparticles showed enhanced dissolution rate and oral bioavailability in Wistar rat due to an increased solubility attributed to combination of effects like amorphization and nanonization with increased surface area and reduced diffusion pathway.     

Freeze-drying of nanosuspensions, part 3: investigation of factors compromising storage stability of highly concentrated drug nanosuspensions

On the basis of a previously developed formulation and process guideline for lyophilized, highly concentrated drug nanosuspensions for parenteral use, it was the purpose of this study to demonstrate that the original nanoparticle size distribution can be preserved over a minimum period of 3 months, even if aggressive primary drying conditions are used. Critical factors were evaluated that were originally believed to affect storage stability of freeze-dried drug nanoparticles. It was found that the nature and concentration of the steric stabilizer, such as Poloxamer 338 and Cremophor EL, are the most important factors for long-term stability of such formulations, independent of the used drug compound. The rational choice of an adequate steric stabilizer, namely Poloxamer 338, in combination with various lyoprotectants seems crucial to prevent physical instabilities of the lyophilized drug nanoparticles during short-term stability experiments at ambient and accelerated conditions. A 200 mg/mL concentration of nanoparticles could successfully be stabilized over the investigated time interval. In the course of the present experiments, polyvinylpyrrolidone, type K15 was found superior to trehalose or sucrose in preserving the original particle size distribution, presumably based on its surface-active properties. Lastly, it was demonstrated that lower water contents are generally beneficial to stabilize such systems.     

Solid lipid nanoparticles (SLN) for controlled drug delivery II. drug incorporation and physicochemical characterization

Solid lipid nanoparticles (SLN) are a colloidal carrier system for controlled drug delivery. The lipophilic model drugs tetracaine and etomidate were incorporated to study the maximum drug loading, entrapment efficacy, effect of drug incorporation on SLN size, zeta potential (charge) and long-term physical stability. Drug loads of up to 10% could be achieved whilst simultaneously maintaining a physically stable nanoparticle dispersion. Incorporation of drugs showed no or little effect on particle size and zeta potential compared to drug-free SLN. The optimized production parameters previously established for drug-free SLN dispersions can therefore be transferred to drug-loaded systems to facilitate product development.     

Solid lipid nanoparticles (SLN) for controlled drug delivery. II. Drug incorporation and physicochemical characterization

Solid lipid nanoparticles (SLN) are a colloidal carrier system for controlled drug delivery. The lipophilic model drugs tetracaine and etomidate were incorporated to study the maximum drug loading, entrapment efficacy, effect of drug incorporation on SLN size, zeta potential (charge) and long-term physical stability. Drug loads of up to 10% could be achieved whilst simultaneously maintaining a physically stable nanoparticle dispersion. Incorporation of drugs showed no or little effect on particle size and zeta potential compared to drug-free SLN. The optimized production parameters previously established for drug-free SLN dispersions can therefore be transferred to drug-loaded systems to facilitate product development.     

Simultaneously manufactured nano-in-micro (SIMANIM) particles for dry-powder modified-release delivery of antibodies

Simultaneously Manufactured Nano-In-Micro (SIMANIM) particles for the pulmonary delivery of antibodies have been prepared by the spray-drying of a double-emulsion containing human IgG (as a model antibody), lactose, poly(lactide-co-glycolide) (PLGA) and dipalmitoylphosphatidylcholine (DPPC). The one-step drying process involved producing microparticles of a diameter suitable for inhalation that upon contact with aqueous media, partially dissolved to form nanoparticles, ～10-fold smaller than their original diameter. Continuous release of the model antibody was observed for 35 days in pH 2.5 release media, and released antibody was shown to be stable and active by gel electrophoresis, field-flow fractionation and enzyme linked immunosorbent assay. Adding 1% L-leucine to the emulsion formulation, and blending ‘SIMANIM’ particles with 1% magnesium stearate, achieved a fine particle fraction of ～60%, when aerosolised from a simple, capsule-based, dry powder inhaler device. ‘SIMANIM’ particles could be beneficial for the delivery of antibodies targeted against inhaled pathogens or other extracellular antigens, as well as having potential applications in the delivery of a wide range of other biopharmaceuticals and certain small-molecule drugs. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4055–4068, 2009     

In vitro evaluation of cellular response induced by manufactured nanoparticles

"Nanoparticle" is defined as the particles whose diameter in at least one dimension is less than 100 nm. Compared with fine-particles, nanoparticles have large specific surface area. There is a dramatic increase over fine-particles in chemical and physical activities, such as ion release, adsorption ability, and ROS production. These properties are important for industrial use, and many nanoparticles are already used in products familiar to consumers as sunscreens and cosmetics. However, nanoparticle properties beneficial to the industry may also induce biological influences, including toxic activities. Recently, many investigations about the toxicology of nanoparticles have been reported. In the evaluation of nanoparticles toxicity, in vitro studies give us important information, especially in terms of toxic mechanisms. In vitro studies showed that some nanoparticles induce oxidative stress, apoptosis, production of cytokines, and cell death. There are reports that cellular influences of other nanoparticles are small. There are also reports of different results, some with low and some with high influences, for the same nanoparticle. One of the causes of this inconsistency might be a diremption of the living body influence study and the characterization study. Characterization of individual nanoparticles and their dispersions are essential for in vitro evaluation of their biological effects since each nanoparticle shows unique chemical and physical properties. Particularly, the aggregation state and metal ion release ability of nanoparticles affect its cellular influences. Reports concerning the characterization in the in vitro toxicity assessment are increasing. For an accurate risk assessment of nanoparticles, in this review, we outline recent studies of in vitro evaluation of cellular influences induced by nanoparticles. Moreover, we also introduce current studies about the characterization methods of nanoparticles and their dispersions for toxicological evaluation.     

Stable nanoparticle aggregates/agglomerates of different sizes and the effect of their size on hemolytic cytotoxicity

To study the toxicity of nanoparticles under relevant conditions, it is critical to disperse nanoparticles reproducibly in different agglomeration states in aqueous solutions compatible with cell-based assays. Here, we disperse gold, silver, cerium oxide, and positively-charged polystyrene nanoparticles in cell culture media, using the timing between mixing steps to control agglomerate size in otherwise identical media. These protein-stabilized dispersions are generally stable for at least two days, with mean agglomerate sizes of ～23 nm silver nanoparticles ranging from 43-1400 nm and average relative standard deviations of less than 10%. Mixing rate, timing between mixing steps and nanoparticle concentration are shown to be critical for achieving reproducible dispersions. We characterize the size distributions of agglomerated nanoparticles by further developing dynamic light scattering theory and diffusion limited colloidal aggregation theory. These theories frequently affect the estimated size by a factor of two or more. Finally, we demonstrate the importance of controlling agglomeration by showing that large agglomerates of silver nanoparticles cause significantly less hemolytic toxicity than small agglomerates.     

喷雾干燥法固化黄豆苷元固体脂质纳米粒的研究

目的：建立一种干燥的固体脂质纳米粒的制备方法。方法：采用超声分散法制备黄豆苷元固体脂质纳米粒的混悬液,然后采用喷雾干燥法将其制成干燥的、可再分散的固体脂质纳米粒。结果：在混悬液中黄豆苷元固体脂质纳米粒为球形粒子,平均粒径约为280 nm,喷雾干燥后得到的纳米粒仍为球型,分散后的粒径与喷干前相比有所增大,平均粒径约为720 nm,稳定性较好。结论：喷雾干燥法制备黄豆苷元固体脂质纳米粒是可行的。     

Freeze drying of human serum albumin (HSA) nanoparticles with different excipients

Freeze drying is a suitable technique to improve the long-term storage stability of colloidal drug carrier systems such as nanoparticles. Aim of this study was to systematically evaluate excipients for the freeze drying and long-term stability of albumin-based nanoparticles. In our study, nanoparticles made of human serum albumin (HSA) were freeze dried in the presence of different cryoprotective agents and after reconstitution were evaluated with regard to their physico-chemical characteristics. Empty, doxorubicin-loaded, and PEGylated nanoparticles were prepared and were freeze dried in the presence of different concentrations of sucrose, trehalose, and mannitol, respectively. The samples were physico-chemically characterised with regard to lyophilisate appearance, particle size, and polydispersity using photon correlation spectroscopy. For evaluation of long-term stability, the samples were stored at 2-8, 25, and 40 degrees C over predetermined time intervals. In the absence of cryoprotectants, particle growth was observed in all freeze-dried formulations. In the presence of sucrose, mannitol, and trehalose aggregation of HSA nanoparticles during the freeze-drying procedure was prevented. Although all of the excipients were identified to be suitable stabilisers for freeze drying of HSA nanoparticles, sucrose and trehalose were superior to mannitol, especially with regard to the long-term storage stability results.     

Stable nanoparticle aggregates/agglomerates of different sizes and the effect of their size on hemolytic cytotoxicity

Abstract

To study the toxicity of nanoparticles under relevant conditions, it is critical to disperse nanoparticles reproducibly in different agglomeration states in aqueous solutions compatible with cell-based assays. Here, we disperse gold, silver, cerium oxide, and positively-charged polystyrene nanoparticles in cell culture media, using the timing between mixing steps to control agglomerate size in otherwise identical media. These protein-stabilized dispersions are generally stable for at least two days, with mean agglomerate sizes of ～23 nm silver nanoparticles ranging from 43–1400 nm and average relative standard deviations of less than 10%. Mixing rate, timing between mixing steps and nanoparticle concentration are shown to be critical for achieving reproducible dispersions. We characterize the size distributions of agglomerated nanoparticles by further developing dynamic light scattering theory and diffusion limited colloidal aggregation theory. These theories frequently affect the estimated size by a factor of two or more. Finally, we demonstrate the importance of controlling agglomeration by showing that large agglomerates of silver nanoparticles cause significantly less hemolytic toxicity than small agglomerates.     

A comparison between spray drying and spray freeze drying for dry powder inhaler formulation of drug-loaded lipid-polymer hybrid nanoparticles

Lipid-polymer hybrid nanoparticles - polymeric nanoparticles enveloped by lipid layers - have emerged as a potent therapeutic nano-carrier alternative to liposomes and polymeric nanoparticles. Herein we perform comparative studies of employing spray drying (SD) and spray freeze drying (SFD) to produce inhalable dry-powder form of drug-loaded lipid-polymer hybrid nanoparticles. Poly(lactic-co-glycolic acid), lecithin, and levofloxacin are employed as the polymer, lipid, and drug models, respectively. The hybrid nanoparticles are transformed into micro-scale nanoparticle aggregates (or nano-aggregates) via SD and SFD, where the effects of (1) different excipients (i.e. mannitol, polyvinyl alcohol (PVA), and leucine), and (2) nanoparticle to excipient ratio on nano-aggregate characteristics (e.g. size, flowability, aqueous reconstitution, aerosolization efficiency) are examined. In both methods, PVA is found more effective than mannitol for aqueous reconstitution, whereas hydrophobic leucineis needed to achieve effective aerosolization as it reduces nano-aggregate agglomeration. Using PVA, both methods are equally capable of producing nano-aggregates having size, density, flowability, yield and reconstitutibility in the range ideal for inhaled delivery. Nevertheless, nano-aggregates produced by SFD are superior to SD in terms of their aerosolization efficiency manifested in the higher emitted dose and fine particle fraction with lower mass median aerodynamic diameter.     

Long-term stability characteristics of metal nanoparticle generator using small ceramic heater for inhalation toxicity studies

The use of silver nanoparticles is rapidly growing in various industries. However, exposure to nano-sized silver particles generated during production, use, and disposal in ambient air or the workplace remains an important concern for public and occupational health. There are currently no specific methods for measuring the inhalation toxicity of nanoparticles or specific nanoparticle generation methods. In a previous study, silver nanoparticles were generated using a small ceramic heater with a local heating area that allowed direct heating of the bulk silver source, thereby eliminating any space between the heating unit and the source material such that the volume of the nanoparticle generator and power consumption are both remarkably reduced. Therefore, to evaluate the efficacy of this nanoparticle generator for inhalation toxicity studies, the long-term particle generation characteristics were investigated, and the results confirmed a very stable continuous operation over 20-30 h. The geometric mean diameter and total number concentration of nanoparticles remained stable for about 24 h when the initial loaded mass of bulk silver on the heater surface was 160 mg. The particle size distribution after a long operating time was then estimated when changing the initial mass of bulk silver on the heater surface. It took about 36 h for the loaded silver mass to decrease from 160 mg to 100 mg, during which time the geometric mean diameter of the nanoparticles only decreased 6%, from 14 nm to 13.2 nm.