Preparation of griseofulvin nanoparticle suspension by high-pressure homogenization and preservation of the suspension with saccharides and sugar alcohols

Mechanisms of drug release from a melt-milled, poorly soluble drug substance

Increasing the dissolution kinetics of low aqueous soluble drugs is one of the main priorities in drug formulation. New strategies must be developed, which should consider the two main dissolution mechanisms: surface reaction and diffusion. One promising tool is the so-called solid crystal suspension, a solid dispersion consisting of purely crystalline substances. In this concept, reducing the drug particle size and embedding the particles in a hydrophilic excipient increases the dissolution kinetics. Therefore, a solid crystal suspension containing submicron drug particles was produced via a modified stirred media milling process. A geometrical phase-field approach was used to model the dissolution behavior of the drug particles. A carrier material, xylitol, and the model drug substance, griseofulvin, were ground in a pearl mill. The in-vitro dissolution profile of the product was modeled to gain a deep physical understanding of the dissolution process. The used numerical tool has the potential to be a valuable approach for predicting the dissolution behavior of newly developed formulation strategies.

Devitrification of lyoprotectants: A critical determinant for bacteriophages inactivation in freeze-drying and storage

Bacteriophages as promising natural antibacterial additives are widely used in food processing and storage. Although freeze-drying is an economical and efficient way to preserve phages, so far there is limited data for phage freeze-drying and key factors that inactivate phages during freeze-drying and storage remain unknown. Here we systemically compared different types of saccharides/polyols (dextran 5000, glucose, sucrose, trehalose, mannitol, and xylitol) as lyoprotectants and their potential ratios for phage freeze-drying. The pH and osmotic pressure tolerance of bacteriophages were determined and all lyoprotectant solutions were within the tolerance range of phages. Combined with thermodynamic data, it was found that only completely vitrified formulations (glucose, sucrose, and trehalose) could preserve phages during freeze-drying. Selected freeze-dried phages were further arranged for an accelerated stability study. Most formulations stored at higher temperatures (≥25 ℃) presented devitrification, resulting in a significant drop in phage titer. 10% (w/v) of sucrose was recommended as the best formulation for freeze-dried phage storage with less devitrification and a better fitting coefficient (R2 = 0.9592) to the Arrhenius equation, predictively reaching shelf-time as 1093.3 days at 4 ℃ storage. These findings implied that the devitrification of lyoprotectants was the critical determinant for bacteriophage inactivation both in freeze-drying and storage.

Solubility and Pharmacokinetic Profile Improvement of Griseofulvin through Supercritical Carbon Dioxide-Assisted Complexation with HP-γ-Cyclodextrin

Since griseofulvin was marketed as a non-polyene antifungal antibiotic drug in 1958, its poor water solubility has been an issue for its wide applications, and over the last sixty years, many attempts have been made to increase its water solubility; however, a significant result has yet to be achieved. Through supercritical carbon dioxide-assisted cyclodextrin complexation with the addition of a trace amount of water-soluble polymer surfactant, the griseofulvin inclusion complex with HP-γ-cyclodextrin was prepared and confirmed. The 1:2 ratio of griseofulvin and HP-γ-cyclodextrin in the complex was determined based on its NMR study. After complexation with HP-γ-cyclodextrin, griseofulvin's water solubility was increased 477 times compared with that of griseofulvin alone, which is the best result thus far. The complex showed 90% of griseofulvin release in vitro in 10 min, in an in vivo dog pharmacokinetic study; the Cmax was increased from 0.52 µg/mL to 0.72 µg/mL, AUC0-12 was increased from 1.55 μg·h/mL to 2.75 μg·h/mL, the clearance was changed from 51.78 L/kg/h to 24.16 L/kg/h, and the half-life time was changed from 0.81 h to 1.56 h, indicating the obtained griseofulvin complex can be a more effective drug than griseofulvin alone.

Cyclosporine A Nanosuspensions for Ophthalmic Delivery: A Comparative Study between Cationic Nanoparticles and Drug-Core Mucus Penetrating Nanoparticles

The effect of mucin on ocular bioavailability depends on the extent to which it acts as a barrier or retention site. Mucus penetrating particles (MPPs) can evade the mucus entrapment and associated rapid clearance, but cationic nanoparticles have high adhesion to the mucosa. Both formulations can prolong the drug residence time on the surface of the eyes. The purpose of this work is to compare the effects of mucoadhesion of cationic nanoparticles and mucous permeability of MPPs on ocular bioavailability. Cationic nanosuspensions and drug-core MPP nanosuspensions were developed using the anti-solvent precipitation method. The results of X-ray diffraction revealed that CsA was amorphous. In vitro mucoadhesion evaluation demonstrated that cationic nanosuspensions enhanced the interaction with pig mucin about 5.0-6.0 fold compared to drug-core MPP nanosuspensions. A mucus permeation study by the transwell diffusion system showed that the P_app values of drug-core MPP nanosuspensions were 5.0-10.0 times higher than those of cationic nanosuspensions. In vivo ocular bioavailability evaluation of those CsA formulations was conducted in rabbits using a conventional nanosuspension as a comparison. The CsA concentrations in the cornea following the administration of a cationic nanosuspension and a drug-core MPP nanosuspension were 13,641.10 ng/g and 11,436.07 ng/g, respectively, significantly higher than that of the conventional nanosuspension (8310.762 ng/g). The results showed that both the cationic and MPP nanosuspensions were able to deliver CsA to anterior ocular tissues in effective therapeutic concentrations (10-20 μg/g) with topical drop instillation. The cationic nanosuspension could achieve relatively higher bioavailability than the MPP nanosuspension. The cationic nanosuspension would be a promising ocular drug delivery system.

Rational design of polysorbate 80 stabilized human serum albumin nanoparticles tailored for high drug loading and entrapment of irinotecan

Human serum albumin (HSA) nanoparticles are considered to be versatile carrier of anticancer agents in efficiently delivering the drug to the tumor site without causing any toxicity. The aim of the study was to develop stable HSA nanoparticles (NPs) of drug irinotecan (Iro) having slightly water solubility and moderate HSA binding. A novel strategy of employing a hydrophilic non-ionic surfactant polysorbate 80 which forms protein-polysorbate 80 complex with increased affinity and improvement in Iro-HSA binding has been used to maximize the loading and entrapment efficiency of Iro in HSA-NPs. Bespoke nanoparticles with entrapment efficiency (79.09%) and drug loading of 9.62% could be achieved with spherical shape and particle size of 77.38 nm, 0.290 polydispersity index and -23.7 mv Zeta potential. The drug entrapment in nanoparticles was confirmed by Differential Scanning Calorimeter, Fourier Transformation Infrared Spectroscopy and Fluorescence Spectroscopy. In vitro release of Iro from NPs showed biphasic-release with initial burst followed by prolonged release upto 24 h. The short-term stability investigation of nanodispersion showed no significant changes in physicochemical properties of NPs. Long-term studies on freeze dried Iro-HSA-NPs indicated good stability of NPs up to 12 months. This is the first report for efficient fabrication of Iro delivery system based on HSA nanoparticles.

Design of experiments for microencapsulation applications: A review

Microencapsulation techniques have been intensively explored by many research sectors such as pharmaceutical and food industries. Microencapsulation allows to protect the active ingredient from the external environment, mask undesired flavours, a possible controlled release of compounds among others. The purpose of this review is to provide a background of design of experiments in microencapsulation research context. Optimization processes are required for an accurate research in these fields and therefore, the right implementation of micro-sized techniques at industrial scale. This article critically reviews the use of the response surface methodologies in pharmaceutical and food microencapsulation research areas. A survey of optimization procedures in the literature, in the last few years is also presented.

[Preparation and physicochemical study of the preservation of nanoparticles]

The importance of nanoparticle formulation is increasingly recognized in supporting pharmaceutical development. Thus, maintaining nanoparticles in a constant state is a major issue. A method involving lyophilization with the addition of saccharides can be used to maintain the steady state of nanoparticles. In this study, trisaccharides, tetrasaccharides, and pentasaccharides were added to nanoparticle suspensions, followed by rehydration of the samples, which had been either dried normally or freeze-dried. The particle size after rehydration was measured. In addition, each powder was measured using a powder X-ray diffractometer and thermal analysis device to investigate the correlation between the nanoparticles' aggregation and the crystal form of saccharides. The diameter of the nanoparticles was maintained when it was freeze-dried, while particle aggregation occurred when normally dried samples were used. In addition, crystalline saccharide was not observed in the freeze-dried group, but did appear in the normally dried group.

Continuous production of drug nanoparticle suspensions via wet stirred media milling: a fresh look at the Rehbinder effect

Nanoparticles of BCS Class II drugs are produced in wet stirred media mills operating in batch or recirculation mode with the goal of resolving the poor water-solubility issue. Scant information is available regarding the continuous production of drug nanoparticles via wet media milling. Griseofulvin and Naproxen were milled in both recirculation mode and multi-pass continuous mode to study the breakage dynamics and to determine the effects of suspension flow rate. The evolution of the median particle size was measured and described by an empirical breakage model. We found that these two operation modes could produce drug nanosuspensions with similar particle size distributions (PSDs). A reduced suspension flow rate slowed the breakage rate and led to a wider PSD and more differentiation between the two operation modes. The latter part of this study focused on the roles of stabilizers (hydroxypropyl cellulose and sodium lauryl sulfate) and elucidation of the so-called Rehbinder effect (reduction in particle strength due to adsorbed stabilizers such as polymers and surfactants). Milling the drugs in the absence of the stabilizers produced primary nanoparticles and their aggregates, while milling with the stabilizers produced smaller primary nanoparticles with minimal aggregation. Using laser diffraction, BET nitrogen adsorption, scanning electron microscopy imaging, and a microhydrodynamic analysis of milling, this study, for the first time, provides sufficient evidence for the existence of the Rehbinder effect during the milling of drugs. Not only do the polymers and surfactants allow proper stabilization of the nanoparticles in the suspensions, but they also do facilitate drug particle breakage.

Preparation of azithromycin nanosuspensions by reactive precipitation method

PURPOSE

The aim of this work was to prepare azithromycin (AZI) nanosuspensions to increase the solubility and dissolution rate.

METHOD

AZI nanosuspensions were prepared by the combination of reactive precipitation and freeze-drying in presence of biocompatible stabilizer. Formulation and process variables affecting the characteristics of nanosuspensions were optimized. Various tests were carried out to study the physicochemical characteristics of AZI nanosuspensions.

RESULTS

The nanosuspensions were parenterally acceptable and autoclavable, because soybean lecithin was the stabilizer of choice and no organic solvents were used during the preparation. The mean particle size and zeta potential of the AZI nanosuspensions were about 200 nm (±20 nm) and -36.7 mV (±7.6 mV), respectively. Solid nanoparticles were obtained by lyophilization of the nanosuspensions and nanosuspensions rapidly reconstituted when the nanoparticles were dispersed in water. X-ray diffraction and differential scanning calorimetry analysis showed that the crystal state of nanoparticles was amorphous. Solubility and in vitro release studies indicated that the saturated solubility and dissolution rate increased obviously in comparison of raw AZI. The nanoparticles were physically stable over a period of 5 months as demonstrated by unchanged crystallinity and stable particle size when stored at room temperature and protected from humidity.

CONCLUSION

The results suggested that reactive precipitation is an effective way to prepare AZI nanosuspensions with increased solubility and dissolution rate.

Poorly water-soluble drug nanoparticles via an emulsion-freeze-drying approach

Low water solubility of a high percentage of pharmaceuticals is a big issue for pharmaceutical applications due to the resulting low bioabsorption and hence limited therapeutic efficacy. Preparation of drug nanoparticles has been one of the mostly investigated routes to address this problem. In this study, we reported the preparation of nanoparticles via an emulsion-freeze-drying approach. Indomethacin (IMC, a poorly water-soluble drug) nanoparticles were formed in situ within porous poly(vinyl alcohol). The IMC nanoparticles could be released into water to form stable nanodispersions simply by rapid dissolution of the porous polymeric scaffold. This study focused on how preparation conditions including phase volume ratios in the emulsions and the concentrations of polymer, surfactant and drug influenced the formation of IMC nanoparticles. It was concluded that the loading and size of IMC nanoparticles could be easily tuned by changing the preparation conditions.

Hydrocortisone nanosuspensions for ophthalmic delivery: A comparative study between microfluidic nanoprecipitation and wet milling

Recently, drug nanosuspensions have shown a potential for ophthalmic delivery. In this study, a hydrocortisone (HC) nanosuspension (NS) was developed using microfluidic nanoprecipitation as a recent, simple and cost-effective bottom-up technique of drug nanonization. For comparison, a second HC NS was prepared by top-down wet milling procedures. The produced nanosuspensions were characterized for particle size, shape and zeta potential. HC nanosuspensions of approximately 300nm particle size were produced by adjusting experimental conditions of the two processing techniques. Results of X-ray diffraction and differential scanning calorimetry revealed that HC maintained the crystalline structure upon milling, while predominant amorphous particles were generated after precipitation. Ocular bioavailability of HC nanosuspensions was assessed in albino rabbits using HC solution as a control. A sustained drug action was maintained up to 9h for the nanosuspensions compared to 5h for the drug solution. The precipitated and milled NS achieved comparable AUC(0-9h) values of 28.06±4.08 and 30.95±2.2, respectively, that were significantly (P<0.05) higher than that of HC solution (15.86±2.7). After 2 months storage at room temperature, the milled HC NS showed good stability with no discernable changes in particle size, whereas the particle size of the precipitated HC NS increased to 440nm.

Particle size reduction and pharmacokinetic evaluation of a poorly soluble acid and a poorly soluble base during early development

AIM

The aim of the present study was to find out if nanosuspensions were a better choice compared with microsuspensions, for the present substances with water solubility in the order of 2-3 μM (pH 6.8, small intestinal pH) and no permeability limitations. The ambition was also to understand what the higher solubility in the stomach for BA99 means in terms of absorption properties of the substance.

METHOD

The pharmacokinetic parameters of a poorly soluble acid (AC88) and a poorly soluble base (BA99) administered orally as nanosuspensions have been compared with those from microsuspensions using rat as in vivo species.

RESULTS

A significant difference was observed between the two suspensions for AC88 already at the lowest dose, 5 μmol/kg (the particle size of the nanosuspensions and the microsuspensions was about 200 nm and 14 μm, respectively). These results were further confirmed at a high dose (500 μmol/kg). However, for BA99, there were no significant differences between the two formulations at any dose investigated (the particle size of the nanosuspensions and the microsuspensions was about 280 nm and 12 μm, respectively).

CONCLUSIONS

The study demonstrated a clear correlation between particle size and in vivo exposures for an acidic compound, the nanosuspensions providing the highest exposure. For a basic compound, on the other hand, with the present properties and doses, a microsuspension was sufficient. In the latter case, the higher solubility at gastric pH, because of the basic pK(a), limits the need for particle reduction.

A formulation comparison between micro- and nanosuspensions: the importance of particle size for absorption of a model compound, following repeated oral administration to rats during early development

AIM

The aim of this study was to maximize the exposure of a model compound (MC) for forthcoming high-dose toxicological studies with the physical form of the original compound unaffected.

METHOD

The two evaluated formulation approaches for the present poorly water-soluble compound were micro- and nanosuspensions.

RESULTS

The particle size was about 280 nm for the nanosuspensions and about 4 μm for the microsuspensions. The crystallinity and the crystalline form of the ground samples were conserved. The physical and the chemical stabilities of the two kinds of suspensions were unaffected during the investigated time period. The in vivo results of the study showed that the pharmacokinetic parameters investigated were comparable at the low-dose level (6 μmol/kg) for both formulations after single administration. However, at the two higher doses (60 and 300 μmol/kg), a significant difference in exposure was observed between the two suspensions with an improved exposure for smaller particles. After Day 7 of repeated administration, a significant difference in exposure was observed at all dose levels. The overall exposures were higher on Day 7, compared to the exposures on Day 1 (most significant for nanoparticles), due to an accumulation of compound in the body.

CONCLUSIONS

The nanoparticles have a larger surface, resulting in faster in vivo dissolution rate, faster absorption, and increased bioavailability, compared to microparticles. The differences in systemic exposure of model compound, following oral administration of nano- or microparticles of the drug substance, are probably caused by differences in the in vivo dissolution rate and possibly further enhanced by saturation of the systemic elimination.