纳米混悬液的制备方法及其在药物输送中应用的研究进展

纳米混悬液系采用少量表面活性剂或其它载体等稳定纯药物粒子所形成的一种亚微米胶体分散体系。纳米混悬液可增大难溶性药物的溶解度,提高药物的有效性和安全性等。通过查阅国内外相关文献,文章就纳米混悬液的制备方法、评价方法及在药物输送中的应用进行了综述。纳米混悬液的制备技术主要有两种,即Bottom up技术和Top down技术。其评价方法主要包括:粒径及粒径分布、Zeta电势、药物晶体状态等。纳米混悬液在各种给药途径中均有优势。纳米混悬液做为一种新型的药物载体有着广阔的研究前景     

Drug nanosuspensions: a ZIP tool between traditional and innovative pharmaceutical formulations

Introduction: A nanosuspension or nanocrystal suspension is a versatile formulation combining conventional and innovative features. It comprises 100% pure drug nanoparticles with sizes in the nano-scale range, generally stabilized by surfactants or polymers. Nanosuspensions are usually obtained in liquid media with bottom-up and top-down methods or by their combination. They have been designed to enhance the solubility, the dissolution rate and the bioavailability of drugs via various administration routes. Due to their small sizes, nanosuspensions can be also considered a drug delivery nanotechnology for the preparation of nanomedicine products.

Areas covered: This review focuses on the state of the art of the nanocrystal-based formulation. It describes theory characteristics, design parameters, preparation methods, stability issues, as well as specific in vivo applications. Innovative strategies proposed to obtain nanomedicine formulation using nanocrystals are also reported.

Expert opinion: Many drug nanodelivery systems have been developed to increase the bioavailability of drugs and to decrease adverse side effects, but few can be industrially manufactured. Nanocrystals can close this gap by combining traditional and innovative drug formulations. Indeed, they can be used in many pharmaceutical dosage forms as such, or developed as new nano-scaled products. Engineered surface nanocrystals have recently been proposed as a dual strategy for stability enhancement and targeting delivery of nanocrystals.     

纳米混悬剂的制备方法及在药剂学中应用的研究进展

纳米混悬剂可增大难溶性药物的溶解度，改变药物的体内动力学特征，提高安全性和有效性。综述了纳米混悬剂的制各方法及其在药剂学中应用的研究进展。     

Nanosuspensions: a promising drug delivery strategy

Nanosuspensions have emerged as a promising strategy for the efficient delivery of hydrophobic drugs because of their versatile features and unique advantages. Techniques such as media milling and high-pressure homogenization have been used commercially for producing nanosuspensions. Recently, the engineering of nanosuspensions employing emulsions and microemulsions as templates has been addressed in the literature. The unique features of nanosuspensions have enabled their use in various dosage forms, including specialized delivery systems such as mucoadhesive hydrogels. Rapid strides have been made in the delivery of nanosuspensions by parenteral, peroral, ocular and pulmonary routes. Currently, efforts are being directed to extending their applications in site-specific drug delivery.     

Curcumin-docetaxel co-loaded nanosuspension for enhanced anti-breast cancer activity

ABSTRACT

Purpose: A curcumin-docetaxel co-loaded nanosuspension with increased anti-breast cancer activity was developed. Curcumin is a potential anticancer agent with p-glycoprotein (p-gp) inhibiting activity may be co-administered with docetaxel as a nanosuspension to enhance its anticancer effect by increasing the oral bioavailability and decreasing drug efflux.

Methods: Nanosuspensions of curcumin and docetaxel were prepared by precipitation-homozenisation technique and evaluated for particle size, polydispersity, zeta potential and drug release. The in vitro MTT assay was conducted using MCF-7 for anti-breast cancer activity. The in vivo biodistribution by radiolabeling and tumor inhibition study was conducted in mice.

Results: Homogenous nanosuspensions of 80 ± 20 nm were obtained with increased solubility. The drugs as nanosuspensions showed higher cytotoxicity on MCF-7 cell line compared to their suspensions due to the increased in vitro cellular uptake. Due to this increased solubility, sensitization of tumor cells and inhibition of p-gp the in-vivo results showed greater tumor inhibition rate of up to 70% in MCF-7 treated mice. Histopathological results showed higher apoptotic activity and reduced level of angiogenesis.

Conclusions: The in vitro and in vivo study of the nanosuspensions has shown that Co-administration of Curcumin as a p-gp inhibitor with docetaxel may have the potential to increase the anti-breast cancer efficacy of both drugs.     

Pharmacokinetic evaluation of oral fenofibrate nanosuspensions and SLN in comparison to conventional suspensions of micronized drug

An increasing number of newly developed drugs show bioavailability problems due to poor water solubility. Formulating the drugs as nanosuspensions may help to overcome these problems by increasing saturation solubility and dissolution velocity. In the present study the bioavailability of the poorly soluble fenofibrate following oral administration was investigated in rats. Four formulations were tested: a nanosuspension type DissoCube(R), one solid lipid nanoparticle (SLN) preparation and two suspensions of micronized fenofibrate as reference formulations, one suspension in sirupus simplex and a second in a solution of hydroxyethy-cellulose in physiological saline. Both colloidal drug delivery systems showed approximately two-fold bioavailability enhancements in terms of rate and extent compared to the reference formulations. No significant differences were found in AUC(0-22 h) as well as in C(max) and t(max) between the two colloidal delivery systems. In conclusion, nanosuspensions may be a suitable delivery system to improve the bioavailability of drugs with low water solubility.     

Nanosuspensions as advanced printing ink for accurate dosing of poorly soluble drugs in personalized medicines

Folic acid was used as a model drug to demonstrate the advantages of formulating poorly soluble drugs as nanosuspensions and their use in an inkjet-type printing technique to produce personalized medicines. 10% folic acid nanosuspensions stabilized with Tween 20, a stabilizer showing the best wetting potential for folic acid, were prepared via high pressure homogenization. The particle size of the folic acid nanosuspension was well below 5 μm being a prerequisite for inkjet type printing technique. A good reproducibility of the particle size of folic acid nanosuspension prepared via high pressure homogenization was found. As indicated by the zeta potential the formulation showed a good storage stability. High pressure homogenization had no influence on the crystalline state of folic acid. An increase in the saturation solubility by 53.7% was found reducing the particle size from the micrometer range to the nanometer range. The dissolution velocity of the folic acid nanosuspension was significantly enhanced compared to a folic acid suspension, i.e. after 5 min 78.6% of the folic acid was dissolved from the nanosuspension and only 6.2% from the suspension. Moreover, the printing of 10% folic acid nanosuspension could be successfully demonstrated.     

Evaluation of controlled-release polar lipid microparticles

The poorly soluble drug buparvaquone is used in experimental clinics against the gastrointestinal persisting parasite Cryptosporidium parvum. It was produced as nanosuspension by high pressure homogenisation. Main advantages of nanosuspensions (amongst others) are their increase of saturation solubility and dissolution velocity, improving the bioavailability of drugs. The buparvaquone nanosuspension had a bulk population of about 600 nm (analysed by photon correlation spectroscopy (PCS)). The additional analysis performed with laser diffraction showed that only a very small content of microparticles occurred, which is, for the special features of nanosuspensions, negligible because they were still below 3 microm. Another feature of nanosuspensions is the adhesion properties to surfaces, e.g. mucosa. To further increase the adhesion time of the buparvaquone nanosuspension to C. parvum, the nanosuspension was formulated with hydrogels made from mucoadhesive polymers, e.g. different types of Carbopol and chitosan. Only a small increase of the particle size of the bulk population occurred directly after the incorporation of buparvaquone nanosuspension into the hydrogels. The nanosuspension/hydrogel systems were physically long-term stable over a period of 6 months as indicated by the unchanged particle sizes.     

纳米混悬剂的物理稳定性研究进展

纳米混悬剂具有增加药物溶解度,提高生物利用度,降低毒副作用等特点,有关这方面的研究是目前纳米制剂研究的一个热点,美国FDA至今已批准多个相关产品上市。物理稳定性问题在纳米药物混悬液中比较突出,是制约纳米混悬液研发的重要因素之一。本文就纳米混悬剂物理稳定性所面临的问题、理论机制及其应对策略进行综述。     

Conversion of Nanosuspensions into Dry Powders by Spray Drying: A Case Study

Purpose  Drying of nanosuspensions can cause destabilization of the particles, leading to irreversible aggregation. In order to prepare an effective solid dosage form for a nanosuspension, it is imperative that the spray-dried nanoparticles should go back to their original particle size when reconstituted in an aqueous system. This case study examines impact of various formulation and processing parameters on redispersibility of the spray dried nanoparticles. Methods  Nanosuspensions were prepared using the microprecipitation–homogenization process. Spray drying of nanosuspensions was achieved using a lab-scale Buchi spray dryer. Results  Formulation components appeared to have the most significant impact on redispersibility of spray dried particles. Absence of surface charge led to particles that could not be redispersed. On the other hand, charged particles stabilized with an appropriate sugar led to spray dried powders that were flowable and easily redispersible. Dissolution testing showed the presence of two phases—a lag phase that represented dispersion of the loose aggregates, and dissolution of the dispersed nanoparticles. Conclusions  Nanosuspensions of a poorly soluble drug could be spray dried to obtain flowable powders that could be easily redispersed. These optimized powders also showed significantly improved dissolution rates as compared to the micronized drug, or unoptimized nanosuspensions.     

Drug release and permeation studies of nanosuspensions based on solidified reverse micellar solutions (SRMS)

Solidified reverse micellar solutions (SRMS), i.e. mixtures of lecithin and triglycerides, offer high solubilisation capacities for different types of drugs in contrast to simple triglyceride systems [Friedrich, I., Müller-Goymann, C.C., 2003. Characterisation of SRMS and production development of SRMS-based nanosuspensions. Eur. J. Pharm. Biopharm. 56, 111-119]. Nanosuspensions based on SRMS were prepared by homogenisation close to the melting point of the SRMS matrix. In a first step the SRMS matrices of 1:1 (w/w) ratios of lecithin and triglycerides were loaded with 17beta-estradiol-hemihydrate (EST), hydrocortisone (HC) or pilocarpine base (PB), respectively, and subsequently ground in liquid nitrogen to minimise drug diffusion later on. The powder was then dispersed in a polysorbate 80 solution using high pressure homogenisation. The drug loading capacities of the nanosuspensions were very high in the case of poorly water-soluble EST (99% of total 0.1%, w/w, EST) and HC (97% of total 0.5%, w/w, HC) but not sufficient with the more hydrophilic PB (37-40% of total 1.0%, w/w, PB). These findings suggest SRMS-based nanosuspensions to be promising aqueous drug carrier systems for poorly soluble drugs like EST and HC. Furthermore, in vitro drug permeation from the different drug-loaded nanosuspensions was performed across human cornea construct (HCC) as an organotypical cell culture model. PB permeation did not differ from the nanosuspension and an aqueous solution whereas the permeation coefficients of HC-loaded nanosuspensions were reduced in comparison to aqueous and oily solutions of HC. However, the permeated amount was higher from the nanosuspensions due to a much lower HC concentration in the solution than that in the nanosuspension (solution 0.02%, w/w, versus nanosuspension 0.5%, w/w). The high drug load of the nanoparticles provides prolonged HC release. Permeated amounts of EST were reduced in comparison to HC and only detectable with an ELISA technique. The EST release from nanosuspensions and different EST-loaded systems revealed a prolonged EST release from the nanoparticulate systems in contrast to a faster release of an oily solution of an equal EST concentration. With regard to an aqueous EST suspension of similar concentration which represents a depot system the release rate from the nanosuspensions revealed the same order of magnitude which points again to a prolonged release potential of the nanosuspensions.     

Development of a New Method to Assess Nanocrystal Dissolution Based on Light Scattering

Purpose

Nanocrystals exhibit enhanced dissolution rates and can effectively increase the bioavailability of poorly water soluble drug substances. However, methods for in vitro characterization of dissolution are unavailable. The objective of this study was to develop an in situ noninvasive analytical method to measure dissolution of crystalline nanosuspensions based on light scattering.

Methods

Fenofibrate nanosuspensions were prepared by wet media milling. Their solubilities and dissolution profiles in simulated gastric fluid supplemented with 0.1% Tween^? 80 were measured in a small scale setup with an instrument for dynamic light scattering and the intensity of scattered light as readout parameter.

Results

A good correlation was achieved between the dissolution profile of a nanosuspension measured in the light scattering setup and a conventional dissolution experiment. Nanosuspensions of 120–270?nm size could be distinguished by the light scattering method. The suspensions dissolved within 1.9–12.3?min. Over a concentration range of 40–87% of the solubility dissolution profiles of a nanosuspension with 140?nm were monitored and the determined total dissolution times were in good agreement with the Noyes-Whitney dissolution model.

Conclusions

A noninvasive, sensitive and reproducible method is presented to assess nanocrystal dissolution. In situ measurements based on light scattering allow a straightforward experimental setup with high temporal resolution.     

Eudragit RS100 nanosuspensions for the ophthalmic controlled delivery of ibuprofen.

Topical application of non-steroidal anti-inflammatory drugs on the eye is a common treatment used to contrast the miosis induced by surgical traumas, such as cataract extraction. With the aim of improving the availability of sodium ibuprofen (IBU) at the intraocular level, IBU-loaded polymeric nanoparticle suspensions were made from inert polymer resins (Eudragit RS100). The nanosuspensions were prepared by a modification of the quasi-emulsion solvent diffusion technique using variable formulation parameters (drug-to-polymer ratio, total drug and polymer amount, stirring speed). Nanosuspensions had mean sizes around 100 nm and a positive charge (zeta-potential of +40/+60 mV), this makes them suitable for ophthalmic applications. Stability tests (up to 24 months storage at 4 degrees C or at room temperature) or freeze-drying were carried out to optimize a suitable pharmaceutical preparation. In vitro dissolution tests indicated a controlled release profile of IBU from nanoparticles. In vivo efficacy was assessed on the rabbit eye after induction of an ocular trauma (paracentesis). An inhibition of the miotic response to the surgical trauma was achieved, comparable to a control aqueous eye-drop formulation, even though a lower concentration of free drug in the conjunctival sac was reached from the nanoparticle system. Drug levels in the aqueous humour were also higher after application of the nanosuspensions; moreover, IBU-loaded nanosuspensions did not show toxicity on ocular tissues.     

Preparation and characterization of intravenously injectable curcumin nanosuspension

The interest in nanosuspensions by the pharmaceutical industry is increasing given several nanosuspension products currently on the market for poorly soluble drugs. In this study, a novel dosage form for curcumin (CUR), CUR nanosuspension (CUR-NS), was successfully prepared by high pressure homogenization to improve CUR’s cytotoxicity, as well as improve its application via intravenous injection. Characterization of the CUR-NS was evaluated by morphology, size, zeta potential, solubility, dissolution rate, and crystal state of drug. The nanoparticles for CUR-NS presented a sphere-like shape under transmission electron microscopy with an average diameter of 250.6?nm and the zeta potential of CUR-NS was ?27.92 mV. Solubility and dissolution rate of CUR in the form of CUR-NS were significantly increased due to the small particle size and the crystalline state of CUR was preserved to increase its stability against degradation. Superior cytotoxicity in Hela and MCF-7 cells was obtained for CUR-NS compared with CUR solution. The safety evaluation showed that, compared with the CUR solution, CUR-NS provided less local irritation and phlebitis risks, lower rate of erythrocyte hemolysis. These findings suggest that CUR-NS may represent a promising new drug formulation for intravenous administration in the treatment of certain cancers.     

Preparation and characterization of intravenously injectable curcumin nanosuspension

The interest in nanosuspensions by the pharmaceutical industry is increasing given several nanosuspension products currently on the market for poorly soluble drugs. In this study, a novel dosage form for curcumin (CUR), CUR nanosuspension (CUR-NS), was successfully prepared by high pressure homogenization to improve CUR's cytotoxicity, as well as improve its application via intravenous injection. Characterization of the CUR-NS was evaluated by morphology, size, zeta potential, solubility, dissolution rate, and crystal state of drug. The nanoparticles for CUR-NS presented a sphere-like shape under transmission electron microscopy with an average diameter of 250.6?nm and the zeta potential of CUR-NS was -27.92 mV. Solubility and dissolution rate of CUR in the form of CUR-NS were significantly increased due to the small particle size and the crystalline state of CUR was preserved to increase its stability against degradation. Superior cytotoxicity in Hela and MCF-7 cells was obtained for CUR-NS compared with CUR solution. The safety evaluation showed that, compared with the CUR solution, CUR-NS provided less local irritation and phlebitis risks, lower rate of erythrocyte hemolysis. These findings suggest that CUR-NS may represent a promising new drug formulation for intravenous administration in the treatment of certain cancers.     

Development and characterization of an orodispersible film containing drug nanoparticles

In this study, a novel orodispersible film (ODF) containing drug nanoparticles was developed with the goal of transforming drug nanosuspensions into a solid dosage form and enhancing oral bioavailability of drugs with poor water solubility. Nanosuspensions were prepared by high pressure homogenization and then transformed into ODF containing drug nanoparticles by mixing with hydroxypropyl methylcellulose solution containing microcrystalline cellulose, low substituted hydroxypropylcellulose and PEG-400 followed by film casting and drying. Herpetrione, a novel and potent antiviral agent with poor water solubility that extracted from Herpetospermum caudigerum, was chosen as a model drug and studied systematically. The uniformity of dosage units of the preparation was acceptable according to the criteria of Japanese Pharmacopoeia 15. The ODF was disintegrated in water within 30 s with reconstituted nanosuspensions particle size of 280 ± 11 nm, which was similar to that of drug nanosuspensions, indicating a good redispersibility of the fast dissolving film. Result of X-ray diffraction showed that HPE in the ODF was in the amorphous state. In the in vitro dissolution test, the ODF containing HPE nanoparticles showed an increased dissolution velocity markedly. In the pharmacokinetics study in rats, compared to HPE coarse suspensions, the ODF containing HPE nanoparticles exhibited significant increase in AUC_0–24h, C_max and decrease in T_max, MRT. The result revealed that the ODF containing drug nanoparticles may provide a potential opportunity in transforming drug nanosuspensions into a solid dosage form as well as enhancing the dissolution rate and oral bioavailability of poorly water-soluble drugs.     

Nanosuspension as an ophthalmic delivery system for certain glucocorticoid drugs

Poorly-water-soluble compounds are difficult to develop as drug products using conventional formulation techniques. The use of nanotechnology to formulate poorly-water-soluble drugs as nanosuspensions offers the opportunity to address many of the deficiencies associated with this class of molecules. In the present study, the high pressure homogenization method used to prepare nanosuspensions of three practically insoluble glucocorticoid drugs; hydrocortisone, prednisolone and dexamethasone. The effect of particle size in the micron and nano-size ranges as well as the effect of viscosity of the nanosuspension on the ocular bioavailability was studied by measuring the intraocular pressure of normotensive Albino rabbits using shiØetz tonometer. The results show that compared to solution and micro-crystalline suspensions it is a common feature of the three drugs that the nanosuspensions always enhance the rate and extent of ophthalmic drug absorption as well as the intensity of drug action. In the majority of cases nanosuspensions extend the duration of drug effect to a significant extent. The data presented confirms that nanosuspensions differ from micro-crystalline suspensions and solution as ophthalmic drug delivery systems and that the differences are statistically, highly to very highly significant. The results confirm also the importance of viscosity of nanosuspension especially in increasing the duration of drug action.     

Efficiency of a dexamethasone nanosuspension as an intratympanic injection for acute hearing loss

Dexamethasone sodium phosphate (Dex-SP) is the most commonly used drug administered via intratympanic injection for the treatment of acute hearing loss, but its penetration efficiency into the inner ear is very low. To address this problem, we evaluated the possibility of administering dexamethasone nanosuspensions via intratympanic injection because hydrophobic drugs might be more effective in penetrating the inner ear. Three types of dexamethasone nanosuspensions were prepared; the dexamethasone nanoparticles in the three nanosuspensions were between approximately 250 and 350 nm in size. To compare the efficiency of Dex-SP and dexamethasone nanosuspension in delivering dexamethasone to the inner ear, the concentrations of dexamethasone in perilymph and cochlear tissues were compared by liquid chromatography–mass spectrometry. The dexamethasone nanosuspensions resulted in significantly higher drug concentrations in perilymph and cochlear tissues than Dex-SP at 6 h; interestingly, animals treated with nanosuspensions showed a 26-fold higher dexamethasone concentrations in their cochlear tissues than animals treated with Dex-SP. In addition, dexamethasone nanosuspension caused better glucocorticoid receptor phosphorylation than Dex-SP both in vitro and in vivo, and in the ototoxic animal model, the nanosuspension showed a significantly better hearing-protective effect against ototoxic drugs than Dex-SP. In the in vivo safety evaluation, the nanosuspension showed no toxicity at concentrations up to 20 mg/mL. In conclusion, a nanosuspension of dexamethasone was able to deliver dexamethasone to the cochlea very safely and efficiently and showed potential as a formula for intratympanic injection.