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。     

Cyclosporine a loaded solid lipid nanoparticles: optimization of formulation, process variable and characterization

Solid lipid nanoparticles (SLNs) loaded with Cyclosporine A using glyceryl monostearate (GMS) and glyceryl palmitostearate (GPS) as lipid matrices were prepared by melt-homogenization using high-pressure homogenizer. Various process parameters such as homogenization pressure, homogenization cycles and formulation parameters such as ratio of drug: lipid, emulsifier: lipid and emulsifier: co-emulsifier were optimized using particle size and entrapment efficiencies as the dependent variables. The mean particle size of optimized batches of the GMS SLN and GPS SLN were found to be 131 nm and 158 nm and their entrapment efficiencies were 83 +/- 3.08% and 97 +/- 2.59% respectively. To improve the handling processing and stability of the prepared SLNs, the SLN dispersions were spray dried and its effect on size and reconstitution parameters were evaluated. The spray drying of SLNs did not significantly alter the size of SLNs and they exhibited good redispersibility. Solid state studies such as Infra Red Spectroscopy and Differential Scanning Calorimetry indicated absence of any chemical interaction between Cyclosporine A and the lipids. Scanning Electron Microscopy of optimized formulations showed spherical shape with smooth and non porous surface. In vitro release studies revealed that GMS based SLNs released the drug faster (41.12% in 20 hours) than GPS SLNs (7.958% in 20 hours). Release of Cyclosporine A from GMS SLN followed Higuchi equation better than first order while release from GPS SLN followed first order better than Higuchi model.     

Solid lipid nanoparticles (SLN) as ocular delivery system for tobramycin

Aim of this study was to evaluate solid lipid nanoparticles (SLN) as carriers for topical ocular delivery of tobramycin (TOB). The SLN were in the colloidal size range (average diameter below 100 nm; polydispersity index below 0.2) and contained 2.5% TOB as ion-pair complex with hexadecyl phosphate. The preocular retention of SLN in rabbit eyes was tested using drug-free, fluorescent SLN (F-SLN): these were retained for longer times on the corneal surface and in the conjunctival sac when compared with an aqueous fluorescent solution. A suspension of TOB-loaded SLN (TOB-SLN) containing 0.3% w/v TOB was administered topically to rabbits, and the aqueous humour concentration of TOB was determined up to six hours. When compared with an equal dose of TOB administered by standard commercial eyedrops, TOB-SLN produced a significantly higher TOB bioavailability in the aqueous humour.     

Preparation and characterization of n-dodecyl-ferulate-loaded solid lipid nanoparticles (SLN)

Solid lipid nanoparticles (SLN) containing a novel potential sunscreen n-dodecyl-ferulate (ester of ferulic acid) were developed. The preparation and stability parameters of n-dodecyl-ferulate-loaded SLN have been investigated concerning particle size, surface electrical charge (zeta potential) and matrix crystallinity. The chemical stability of n-dodecyl-ferulate at high temperatures was also assessed by thermal gravimetry analysis. For the selection of the appropriated lipid matrix, chemically different lipids were melted with 4% (m/m) of active and lipid nanoparticles were prepared by the so-called high pressure homogenization technique. n-Dodecyl-ferulate-loaded SLN prepared with cetyl palmitate showed the lowest mean particle size and polydispersity index, as well as the highest physical stability during storage time of 21 days at 4, 20 and 40 degrees C. These colloidal dispersions containing the sunscreen also exhibited the common melting behaviour of aqueous SLN dispersions.     

Key production parameters for the development of solid lipid nanoparticles by high shear homogenization

In this work, we report the development and optimization of solid lipid nanoparticles (SLN) production by a simple, fast, and cost-effective high shear homogenization process. A screening of several solid lipids (Compritol 888 ATO, Precirol ATO 5, Cetyl Palmitate, Dynasan 118, Imwitor 900K, Stearic acid) has been carried out in combination with Poloxamer 188 as the selected surfactant, based on the mean particle size and polydispersity index. The improvement of the physical stability of the SLN dispersions was achieved by the use of a cationic lipid (cetyl trimethylammonium bromide) reaching zeta potential values above +60 mV. Combining the optimized speed and time of shear, monodispersed SLN (PdI < 0.25) under the nanometer range could be produced.     

Formulation parameters determining the physicochemical characteristics of solid lipid nanoparticles loaded with all-trans retinoic acid

Solid lipid nanoparticles (SLNs) have gained attention as a colloidal drug carrier, particularly for drugs with limited solubility. The poor aqueous solubility of all-trans retinoic acid (ATRA) has been a limiting factor in its clinical use. This study was undertaken to overcome the solubility limitation of ATRA by loading in SLNs. The physicochemical characteristics of ATRA-loaded SLNs were investigated by particle size analysis, zeta potential measurement, thermal analysis and HPLC determination of ATRA content. The mean particle size of ATRA-loaded SLNs could be reduced (1) by mixing EggPC and Tween 80 as a surfactant and (2) by increasing the total surfactant amount. The smallest mean particle size of SLNs was obtained with 50 mg/g surfactant mixture composed of 54:46% (w/w) EggPC:Tween 80 (154.9 nm). The zeta potential of SLNs could be increased by mixing EggPC, Tween 80 and DSPE-PEG in the surfactant mixture. The zeta potential of SLNs prepared with 50 mg/g surfactant mixture composed of 48:6:46% (w/w) of EggPC:DSPE-PEG:Tween 80 was -38.18 mV. ATRA could be loaded at 2.4% (percentage of lipid matrix) on these SLNs without impairing their physical stability. After freeze-drying, the mean particle size and polydispersity index of ATRA-loaded SLNs were only slightly increased (181.8 vs. 265.2 nm, 0.173 vs. 0.200). Furthermore, no significant change was observed in the SLN-loaded concentration of ATRA and the zeta potential of SLNs after freeze-drying. Taken together, SLN formulation of ATRA with similar characteristics to those of parenteral emulsions could be obtained even after freeze-drying.     

Preparation and characterization of nocodazole-loaded solid lipid nanoparticles

Abstract

Nocodazole (NCD) has more carcinogenic effect than similar drugs. Moreover, it has low drug release time and high particle size. Solid Lipid Nanoparticles (SLNs) have been evaluated for decrease in particle size and therefore increase in drug release time, for such drugs. In this study, NCD has been successfully incorporated into SLNs systems and remained stable for a period of 90 days. NCD structure related to the chemical nature of solid lipid is a key factor to decide whether anticarcinogenic agent will be incorporated in the long term and for a controlled optimization of active ingredient incorporation and loading, intensive characterization of the physical state of the lipid particles were highly essential. Thus, NMR, FT-IR, DSC (for thermal behavior) analyses were performed and the results did not indicate any problem on stability. Moreover, SLNs were decreased size of NCD in addition to increase in time of the drug release. After SLN preparation, particle size, polydispersity index, electrical conductivity and zeta potential were measured and drug release from NCD-loaded SLNs were performed. These values seem to be of the desired range.     

Ciprofloxacin hydrochloride-loaded glyceryl monostearate nanoparticle: factorial design of Lutrol F68 and Phospholipon 90G

Purpose: This investigation was undertaken to develop glyceryl monostearate (Geleol)-based solid lipid nanoparticles (SLNs) of a hydrophilic drug ciprofloxacin HCl.

Methods: Hansen's solubility parameter study was carried out in screening of a suitable carrier and solvent system. Subsequently, SLNs were prepared by solvent diffusion evaporation method and investigated for particle size, polydispersity index (PDI), zeta potential (ZP), entrapment efficiency (EE) and drug release behaviour.

Results: Variations in SLN composition resulted in particle sizes between 170 and 810?nm and ZPs between 8 and 14?mV. The maximum EE was found to be 26.3% with particle size of 188.8?nm. SLN can sustain the release of drug for up to 15?h and it shows Higuchi matrix model as the best-fitted model. SLNs were stable without aggregation of particles under storage conditions.

Conclusions: The results of this study provide the framework for further study involving the SLN formulation for hydrophilic drug molecule.     

Scale-up of the preparation process of solid lipid nanospheres. Part I

An apparatus was designed to prepare solid lipid nanospheres (SLN), potential colloidal therapeutic system obtained by dispersing a warm oil-in-water (o/w) microemulsion in cold water. The apparatus, consisting mainly of a thermostated aluminium chamber and a pneumatic piston, permitted to disperse through a needle up to 100 ml of warm microemulsion and to vary the temperature, the dispersing rate and the drop size of the warm o/w microemulsion. Experimental design was applied to study the effect of four experimental factors, such as chamber temperature, piston pressure, needle gauge and volume of dispersing water, on average diameter and polydispersity index of SLN and on dispersing time of microemulsion (the time required for the microemulsion to drip completely from the apparatus). The results showed that temperature and pressure play the most important roles depending on the needle gauge used. In particular, the smallest SLN were obtained using high temperature and pressure values and a small needle gauge.     

Comparative Studies of Lamivudine-zidovudine Nanoparticles for the Selective Uptake by Macrophages

The present study investigates the specific drug targeting of anti retroviral drugs, such as lamivudine and zidovudine, after intraperitoneal (i.p) injection by incorporation into polymeric nanoparticles (PNs) and solid lipid nanoparticles (SLNs). Our results showed that Glyceryl Monosterate-Poloxamer 188 SLNs (average diameter of 522.466 nm) showed slow drug release rates (63.18% of lamivudine and 62.37% of zidovudine were released in 12 hrs) among all the SLN formulations. For Poly lactic-co-glycolic acid (PLGA)-Poloxamer 188 PNs (average diameter of 70.348 nm), there were faster release rates of both lamivudine and zidovudine (97% and 94.06%, respectively, in 12 hrs). Tissue distribution studies were carried out in mice and concentrations of drugs in different organs were determined using high performance liquid chromatography (HPLC) after i.p. administration. Glyceryl Monosterate-Poloxamer 188 SLNs and PLGAPoloxamer 188 PNs showed increase in the distribution of lamivudine and zidovudine to liver and spleen when compared to the drugs in solution. Also, Glyceryl Monosterate-P 188 SLNs showed higher concentration of drugs in RES organs than PLGA-P 188 PNs.     

Liquid and semisolid SLN dispersions for topical application: rheological characterization.

Aqueous dispersions of solid lipid nanoparticles (SLN) are promising drug carrier systems for topical application. A drawback, however, is the need of incorporating the SLN dispersion in commonly used dermal carriers (creams, gels) to obtain the required semisolid consistency for dermal application. This study describes the production of SLN dispersions having the desired semisolid consistency by a one-step process. Physical characterization of these systems in terms of particle size and rheological properties revealed some interesting features. Despite the high lipid content it was possible to produce colloidal dispersions by high pressure homogenization. Continuous flow measurements revealed systems with yield point, plastic flow and thixotropy. Oscillation measurements proved the viscoelastic microstructure of the SLN dispersions. Higher concentrated SLN dispersions were found to have a prevailing elastic component in contrast to lower concentrated systems. Viscoelastic properties of a 40% SLN dispersion were found to be comparable to standard dermal preparations. Storage stability at room temperature in terms of particle size could be demonstrated over a 6-month period. The development of the gel structure of semisolid SLN dispersions is delayed comparable to commercial O/W creams with non-ionic emulsifiers. Parameters like concentration of the dispersed phase, particle size and particle shape were identified as significant factors influencing the microstructure of these complex semisolid systems.     

Rheological and in vitro release behaviour of clotrimazole-containing aqueous SLN dispersions and commercial creams

Clotrimazole is a wide spectrum local imidazolic antifungal agent used in several dermatological creams, having e.g. 1% (m/m) such as Canesten and Fungizid-ratiopharm cream. In the present work, a new system based on solid lipid nanoparticles (SLN) containing the identical concentration of drug has been developed. A comparative study between the rheological properties of the referred creams and the developed aqueous SLN dispersions was carried out. The influence of incorporation of SLN in a standard hydrophilic cream on its flow curves was also assessed. In addition, the release of clotrimazole from the two commercial creams, as well as from aqueous SLN dispersions was studied. Concerning the rheological investigations, all tested commercial creams revealed very low shear rates and no yield points. Lipid nanoparticles having a mean diameter of approx. 200 nm have been incorporated into a hydrophilic cream, in a concentration of 20%, 30% or 40% (m/m). The hydrophilic cream containing 20% of SLN showed a dilatant-like character; however, increasing the percentage of incorporated lipid nanoparticles to 30% and 40% the formulation changed to a more pseudoplastic character, showing yield values of 28 Pa and 39 Pa, respectively. For in vitro release studies, Franz diffusion cells with a cellulose acetate membrane were used to measure the release of clotrimazole from two different commercial formulations in comparison to the aqueous SLN dispersion. After 6 h the amount of drug released was higher than 48% when delivered from both investigated commercial formulations and not higher than 25% when delivered from the aqueous SLN dispersion. The percentage of drug released determined after 24 h was more than 50% for Canesten cream and Fungizid-ratiopharm cream and not higher than 30% for the developed SLN formulation showing its prolonged release character.     

Preparation,characterization, and evaluation of gatifloxacin loaded solid lipid nanoparticles as colloidal ocular drug delivery system

This article describes the preparation and characterization of solid lipid nanoparticles (SLNs) prepared with stearic acid (SLN-A) and a mixture of stearic acid and Compritol (SLN-B) as lipid matrix and poloxamer-188 as surfactant, using sodium taurocholate and ethanol as co-surfactant mixture, with a view to applying the SLN in topical ocular drug delivery. The SLNs were prepared by o/w microemulsion technique and characterized by time-resolved particle size analysis, polydispersity index, zeta(ζ )-potential, differential scanning calorimetry (DSC), IR-spectroscopy, and wide-angle X-ray diffractometry (WAXD). The results obtained in these studies were compared with SLN prepared with stearic acid alone. IR, WAXD, and DSC studies revealed low-crystalline SLN and were having positive ζ -potentials after three-months of storage. Results indicated mixed lipid-matrix produced SLN with low-crystallinity and smaller particle sizes and higher drug entrapment compared with SLN prepared with stearic acid alone, therefore SLN-B would be suitable for the preparation of nanosuspension. Nanosuspensions were subjected to rheological and physicochemical evaluation, in vitro drug release and ex vivo corneal permeation studies and their effect were evaluated on corneal hydration-level. SLN composed of stearic acid and compritol would prove to be a good ocular drug delivery system considering the smaller particle size, particle size stability, and physiologically tolerable components.     

Multifunctional Nanoparticulate Polyelectrolyte Complexes

Water-soluble, biodegradable, polymeric, polyelectrolyte complex dispersions (PECs) have evolved because of the limitations, in terms of toxicity, of the currently available systems. These aqueous nanoparticulate architectures offer a significant advantage for products that may be used as drug delivery systems in humans. PECs are created by mixing oppositely charged polyions. Their hydrodynamic diameter, surface charge, and polydispersity are highly dependent on concentration, ionic strength, pH, and molecular parameters of the polymers that are used. In particular, the complexation between polyelectrolytes with significantly different molecular weights leads to the formation of water-insoluble aggregates. Several PEC characteristics are favorable for cellular uptake and colloidal stability, including hydrodynamic diameter less than 200 nm, surface charge of >30 mV or <−30 mV, spherical morphology, and polydispersity index (PDI) indicative of a homogeneous distribution. Maintenance of these properties is critical for a successful delivery vehicle. This review focuses on the development and potential applications of PECs as multi-functional, site-specific nanoparticulate drug/gene delivery and imaging devices. An erratum to this article can be found at     

Preparation and characterization of solid lipid nanoparticles loaded with total flavones of Hippophae rhamnoides (TFH)

Solid lipid nanoparticles (SLNs) containing total flavones of Hippophae rhamnoides (TFH) were prepared by high-pressure homogenization (HPH), by both hot HPH and cold HPH. The influence of process parameters (lipid matrix, lipid concentration, carbohydrate type and its concentration) on the SLN size distribution, zeta potential, entrapment efficiency, crystal form, and in vitro release profile was investigated. The highest entrapment efficiency for TFH, at around 93%, was found for SLNs composed of TFH/Compritol 888 ATO in a 1:30 molar ratio and made by cold HPH. The advantages of TFH SLNs are the improved oral bioavailability of TFH and the prolonged mean retention time and drug release time.     

结直肠癌术中异硫蓝染色定位前哨淋巴结的研究

目的探讨结、直肠癌术中异硫蓝染色定位前哨淋巴结的可行性及其临床意义。方法对44例结直肠癌患者术中肿瘤周围注射异硫蓝,定位前哨淋巴结,手术结束后,对前哨淋巴结和其他淋巴结行苏木素-伊红染色。结果术中44例患者共检出前哨淋巴结114个,每例患者的前哨淋巴结为1—5个,平均（2．6±2．1）个,44例患者非前哨淋巴结共检出792个,每例患者的非前哨淋巴结为9—35个,平均（18．0±8．7）个,44例患者中有28例（64％）有淋巴结转移,16例（36％）无淋巴结转移。28例有淋巴结转移患者中26例（93％）有前哨淋巴结转移,2例（7％）无前哨淋巴结转移。结论结直肠癌术中异硫蓝染色定位前哨淋巴结准确性较高,具有较强的临床实用价值。     

Structural investigations on nanoemulsions, solid lipid nanoparticles and nanostructured lipid carriers by cryo-field emission scanning electron microscopy and Raman spectroscopy

Recently, colloidal dispersions based on solid lipids (solid lipid nanoparticles, SLN) and mixtures of solid and liquid lipids (nanostructured lipid carriers, NLC) were described as innovative carrier systems. A spherical particle shape is the basis of features such as a high loading capacity and controlled drug release characteristics due to smaller lipid-water interfaces and longer diffusion pathways when compared to thin platelets. The structures of SLN and the influence of oil load (NLC) on particle properties were investigated by photon correlation spectroscopy (PCS), laser diffractometry (LD), cryo-field emission scanning electron microscopy (cryo-FESEM), Raman spectroscopy and infrared spectroscopy (IR), and compared to a conventional nanoemulsion. PCS and LD data show similar size and size distribution for SLN and NLC (approximately 210 nm, polydispersity index approximately 0.15) and suggested a long term physical stability for the dispersions which had been stored for up to 12 months at different temperatures. Using cryo-FESEM droplets (for the nanoemulsion) and almost spherical particles for SLN and NLC were observed. Raman spectroscopy resulted in spectra for NLC that are weighted to the SLN spectra, suggesting an undisturbed crystal structure. Infrared spectra of the NLC are predominantly SLN in nature. Importantly the SLN bands are unshifted in the NLC spectrum indicating that the crystalline structure is unaffected by the presence of the oil.     

Nevirapine nanosuspensions: stability, plasma compatibility and sterilization

The feasibility of preparing lyophilized or spray dried forms for reconstitution into nanosuspension (NS) was investigated in this study. The bare and surface modified aqueous NS of nevirapine were successfully converted into an anhydrous form by both techniques. The optimization of suitable cryoprotectant is essential to obtain completely dry product of desired properties. The NS adsorbed spray dried powder and granules would serve as excellent carriers for oral antiretroviral delivery. Furthermore, granules compressed to tablet showed sustained release compared to conventional marketed tablet. These results indicated that NS can be lyophilized and spray dried to prepare a product suitable for a parenteral and oral dosage form, respectively provided the formulation composition withstand phase changes during the drying processes process. Effect of sterilization method viz. steam and radiation on aqueous and lyophilized NS was also studied.     

Improved dissolution behavior of lipophilic drugs by solid dispersions: the production process as starting point for formulation considerations

INTRODUCTION: Many new drug substances have low aqueous solubility which can cause poor bioavailability after oral administration. The application of solid dispersions is a useful method to increase the dissolution rate of these drugs and thereby improve their bioavailability. So far, several methods have been developed to prepare solid dispersions. To obtain a product with the desired attributes, both the formulation and production processes should be considered. AREAS COVERED: The most currently used methods to produce solid dispersions, such as the fusion method, hot melt extrusion, spray drying, freeze drying and supercritical fluid precipitation, are reviewed in this paper. In addition, the physicochemical characteristics of the obtained solid dispersions are discussed. EXPERT OPINION: Solid dispersions can be successfully prepared by simple fusion, hot melt extrusion, spray drying, freeze drying and supercritical fluid precipitation. Hot melt extrusion, spray drying and freeze drying are processes that can be applied for large scale production. The simple fusion method is not very suitable for large scale production, but is particularly suitable for screening formulations. The most recent method to produce sold dispersions is supercritical fluid precipitation. The process conditions of this method need extensive investigation, in particular in relationship with the selection of the type of carrier and/or solvent. Both processes and formulation aspects strongly affect the characteristics of solid dispersion products. Furthermore, application of crystalline solid dispersions is gaining increasing interest because they are thermodynamically more stable than amorphous solid dispersions.     

Solid lipid nanoparticles (SLN) for topical drug delivery: incorporation of the lipophilic drugs N,N-diethyl-m-toluamide and vitamin K

Solid lipid nanoparticles (SLN) for topical delivery were prepared by high pressure homogenization using solid lipids. The lipophilic agents DEET (N,N-diethyl-m-toluamide) and vitamin K were used as model drugs. These topical agents were incorporated into SLN which were characterized. Differential scanning calorimetry studies were performed in order to detect probable interactions in the SLN dispersions. Physical stability of SLN in aqueous dispersions and the effect of drug incorporation into SLN were investigated by photon correlation spectroscopy and zeta potential measurements. Characterization and short-term stability studies showedthat DEET and vitamin K are good candidates for topical SLN formulations.