Formulation and Stability Testing of Itraconazole Crystalline Nanoparticles

Itraconazole (ITZ) crystalline nanoparticles were prepared using relatively simple, low-cost sonoprecipitation technique, in which both the solvent and antisolvent were organic in nature. The effect of stabilizer type (hydroxypropyl methylcellulose, hydroxypropyl cellulose, Inutec SP1®, and pluronic F127), drying method (oven and freeze drying) and matrix former used (Avicel PH101, and Aerosil®200) on the dissolution performance as a key characteristic of nanocrystals was evaluated. In 10 min, all of the prepared nanocrystals showed 3.77−8.59 times improvement in percent drug dissolved compared to pure ITZ. Concerning the effect of stabilizer type, the following rank order can be given: pluronic F127 ≥ hydroxypropyl cellulose ≥ hydroxypropyl methylcellulose (HPMC) > inutec SP1. Freeze-dried ITZ nanocrystals containing Avicel PH 101 showed better dissolution rate compared to other nanocrystals. The chemical structure of itraconazole nanocrystals was not changed as revealed by Fourier transform infrared. Stability study of selected nanocrystals (F5, F7, and F8) revealed physical and chemical stability of F7 and F8, while a decrease in dissolution rate of F5 was observed (although being chemically stable) when stored under high relative humidity conditions. Although inutec is less potent than pluronic F127 and HPMC regarding their effect on dissolution rate enhancement, it is equipotent to pluronic F127 in preserving the rapid drug dissolution.Key words: itraconazole, nanocrystals, nanoparticles, stability study     

Effect of Formulation Variables on Preparation of Celecoxib Loaded Polylactide-Co-Glycolide Nanoparticles

Polymer based nanoparticle formulations have been shown to increase drug bioavailability and/or reduce drug adverse effects. Nonsteroidal anti-inflammatory drugs (e.g. celecoxib) reduce prostaglandin synthesis and cause side effects such as gastrointestinal and renal complications. The aim of this study was to formulate celecoxib entrapped poly lactide-co-glycolide based nanoparticles through a solvent evaporation process using didodecyldimethylammonium bromide or poly vinyl alcohol as stabilizer. Nanoparticles were characterized for zeta potential, particle size, entrapment efficiency, and morphology. Effects of stabilizer concentration (0.1, 0.25, 0.5, and 1% w/v), drug amount (5, 10, 15, and 20 mg), and emulsifier (lecithin) on nanoparticle characterization were examined for formula optimization. The use of 0.1, 0.25, and 0.5% w/v didodecyldimethylammonium bromide resulted in a more than 5-fold increase in zeta potential and a more than 1.5-fold increase in entrapment efficiency with a reduction in particle size over 35%, when compared to stabilizer free formulation. Nanoparticle formulations were also highly influenced by emulsifier and drug amount. Using 0.25% w/v didodecyldimethylammonium bromide NP formulations, peak zeta potential was achieved using 15 mg celecoxib with emulsifier (17.15±0.36 mV) and 20 mg celecoxib without emulsifier (25.00±0.18 mV). Peak NP size reduction and entrapment efficiency was achieved using 5 mg celecoxib formulations with (70.87±1.24 nm and 95.55±0.66%, respectively) and without (92.97±0.51 nm and 95.93±0.27%, respectively) emulsifier. In conclusion, formulations using 5 mg celecoxib with 0.25% w/v didodecyldimethylammonium bromide concentrations produced nanoparticles exhibiting enhanced size reduction and entrapment efficiency. Furthermore, emulsifier free formulations demonstrated improved zeta potential when compared to formulations containing emulsifier (p<0.01). Therefore, our results suggest the use of emulsifier free 5 mg celecoxib drug formulations containing 0.25% w/v didodecyldimethylammonium bromide for production of polymeric NPs that demonstrate enhanced zeta potential, small particle size, and high entrapment efficiency.     

Fluorescence Quenching of CdTe Nanocrystals by Bound Gold Nanoparticles in Aqueous Solution

Water-soluble gold nanoparticles with an average diameter of 5 nm were prepared with carboxylic acid terminated thiol ligands. These ligands contain zero to eight methylene moieties. CdTe nanocrystals with an average diameter of 5 nm were synthesized with aminoethanethiol capping. These nanocrystals displayed characteristic absorption and emission spectra of quantum dots. The amine terminated CdTe nanocrystals and carboxylic-acid-terminated gold nanoparticles were conjugated in aqueous solution at pH 5.0 by electrostatic interaction, and the conjugation was monitored with fluorescence spectroscopy. The CdTe nanocrystals were significantly quenched upon binding with gold nanoparticles. The quenching efficiency was affected by both the concentration of gold nanoparticles in the complex and the length of spacer between the CdTe nanocrystal and Au nanoparticle. The observed quenching was explained using Förster resonance energy transfer (FRET) mechanism, and the Förster distance was estimated to be 3.8 nm between the donor–acceptor pair.     

Influence of Formulation Factors on the Preparation of Zein Nanoparticles

The main objective of the present study was to investigate the influence of various formulation parameters on the preparation of zein nanoparticles. 6,7-dihydroxycoumarin (DHC) was used as a model hydrophobic compound. The influence of pH of the aqueous phase, buffer type, ionic strength, surfactant, and zein concentration on particle size, polydispersity index, and zeta potential of DHC-loaded zein nanoparticles were studied. Smaller nanoparticles were formed when the pH was close to the isoelectric point of zein. DHC-loaded zein nanoparticles prepared using citrate buffer (pH 7.4) was better than phosphate buffer in preventing particle aggregation during lyophilization. The ionic strength did not have a significant influence on the particle size of DHC-loaded zein nanoparticles. A combination of Pluronic F68 and lecithin in 2:1 ratio stabilized the zein nanoparticles. An increase in zein concentration led to increase in particle size of DHC-loaded zein nanoparticles. The use of optimal conditions produced DHC-loaded nanoparticles of 256 ± 30 nm and an encapsulation efficiency of 78 ± 7%. Overall, the study demonstrated the optimal conditions to prepare zein nanoparticles for drug encapsulation.KEY WORDS: drug delivery, particle size distribution, pH nanoprecipitation, protein polymers, zein, zeta potential     

Effects of Formulation Variables on the Particle Size and Drug Encapsulation of Imatinib-Loaded Solid Lipid Nanoparticles

Imatinib (IMT), an anticancer agent, inhibits receptor tyrosine kinases and is characterized by poor aqueous solubility, extensive first-pass metabolism, and rapid clearance. The aims of the current study are to prepare imatinib-loaded solid lipid nanoparticles (IMT-SLN) and study the effects of associated formulation variables on particle size and drug encapsulation on IMT-SLN using an experimental design. IMT-SLN was optimized by use of a “combo” approach involving Plackett-Burman design (PBD) and Box-Behnken design (BBD). PBD screening resulted in the determination of organic-to-aqueous phase ratio (O/A), drug-to-lipid ratio (D/L), and amount of Tween® 20 (Tw20) as three significant variables for particle size (S _z), drug loading (DL), and encapsulation efficiency (EE) of IMT-SLN, which were used for optimization by BBD, yielding an optimized criteria of O/A?=?0.04, D/L?=?0.03, and Tw20?=?2.50%?w/v. The optimized IMT-SLN exhibited monodispersed particles with a size range of 69.0?±?0.9 nm, ζ-potential of ?24.2?±?1.2 mV, and DL and EE of 2.9?±?0.1 and 97.6?±?0.1%?w/w, respectively. Results of in vitro release study showed a sustained release pattern, presumably by diffusion and erosion, with a higher release rate at pH 5.0, compared to pH 7.4. In conclusion, use of the combo experimental design approach enabled clear understanding of the effects of various formulation variables on IMT-SLN and aided in the preparation of a system which exhibited desirable physicochemical and release characteristics.     

Influence of Formulation and Processing Factors on Stability of Levothyroxine Sodium Pentahydrate

Stability of formulations over shelf-life is critical for having a quality product. Choice of excipients, manufacturing process, storage conditions, and packaging can either mitigate or enhance the degradation of the active pharmaceutical ingredient (API), affecting potency and/or stability. The purpose was to investigate the influence of processing and formulation factors on stability of levothyroxine (API). The API was stored at long-term (25°C/60%RH), accelerated (40°C/75%RH), and low-humidity (25°C/0%RH and 40°C/0%RH) conditions for 28 days. Effect of moisture loss was evaluated by drying it (room temperature, N₂) and placed at 25°C/0%RH and 40°C/0%RH. The API was incubated with various excipients (based on package insert of marketed tablets) in either 1:1, 1:10, or 1:100 ratios with 5% moisture at 60°C. Commonly used ratios for excipients were used. The equilibrium sorption data was collected on the API and excipients. The API was stable in solid state for the study duration under all conditions for both forms (potency between 90% and 110%). Excipients effect on stability varied and crospovidone, povidone, and sodium laurel sulfate (SLS) caused significant API degradation where deiodination and deamination occurred. Moisture sorption values were different across excipients. Crospovidone and povidone were hygroscopic whereas SLS showed deliquescence at high RH. The transient formulation procedures where temperature might go up or humidity might go down would not have major impact on the API stability. Excipients influence stability and if possible, those three should either be avoided or used in minimum quantity which could provide more stable tablet formulations with minimum potency loss throughout its shelf-life.     

Influence of Some Formulation Variables on the Optimization of pH-dependent,Colon-targeted,Sustained-release Mesalamine Microspheres

The aim of this work was to understand the influence of different formulation variables on the optimization of pH-dependent, colon-targeted, sustained-release mesalamine microspheres prepared by O/O emulsion solvent evaporation method, employing pH-dependent Eudragit S and hydrophobic pH-independent ethylcellulose polymers. Formulation variables studied included concentration of Eudragit S in the internal phase and the ratios between; internal to external phase, drug to Eudragit S and Eudragit S to ethylcellulose to mesalamine. Prepared microspheres were evaluated by carrying out in vitro release studies and determination of particle size, production yield, and encapsulation efficiency. In addition, morphology of microspheres was examined using optical and scanning electron microscopy. Emulsion solvent evaporation method was found to be sensitive to the studied formulation variables. Particle size and encapsulation efficiency increased by increasing Eudragit S concentration in the internal phase, ratio of internal to external phase, and ratio of Eudragit S to the drug. Employing Eudragit S alone in preparation of the microspheres is only successful in forming acid-resistant microspheres with pulsatile release pattern at high pH. Eudragit S and ethylcellulose blend microspheres were able to control release under acidic condition and to extend drug release at high pH. The stability studies carried out at 40°C/75% RH for 6 months proved the stability of the optimized formulation. From the results of this investigation, microencapsulation of mesalamine in microspheres using blend of Eudragit S and ethylcellulose could constitute a promising approach for site-specific and controlled delivery of drug in colon.     

Influence of Processing Parameters and Formulation Factors on the Bioadhesive,Temperature Stability and Drug Release Properties of Hot-Melt Extruded Films Containing Miconazole

This study investigated the processing parameters and formulation factors on the bioadhesive properties, temperature stability properties, and drug release properties of miconazole in PolyOx® and Klucel® matrix systems produced by Hot-melt Extrusion (HME) technology. Miconazole incorporated into these matrix systems were found to be stable for 8 months by X-ray diffraction (XRD). The addition of miconazole increased area under the curve (AUC) at contact time intervals of 30 and 60 sec, while the bioadhesion decreased with an increase in processing temperatures. The release profiles suggest that a sustained release of miconazole was observed from all of the tested HME film formulations for approximately 10 h. The release from the optimal HME film extruded at 205°C was found to be significantly different than that extruded at 190°C. Therefore, this matrix system may address the present shortcomings of currently available therapy for oral and pharyngeal candidiasis.     

Investigation of Formulation Variables and Excipient Interaction on the Production of Niosomes

The aim of this study was to investigate the effects of formulation and process variables on the properties of niosomes formed from Span 40 as nonionic surfactant. A variety of formulations encapsulating Paclitaxel, a hydrophobic model drug, were prepared using different dicetyl phosphate (DCP) and Span 40-cholesterol (1:1) amounts. Formulations were optimized by multiple regression analysis to evaluate the changes on niosome characteristics such as entrapment efficiency, particle size, polydispersity index, zeta potential and in vitro drug release. Multiple regression analysis revealed that as Span 40-cholesterol amounts in the formulations were increased, zeta potential and percent of drug released at 24th hour were decreased. Besides, DCP was found to be effective on increasing niosome size. As a process variable, the effect of sonication was observed and findings revealed an irreversible size reduction on Span 40 niosomes after probe sonication. Monodisperse small sized (133 ± 6.01 nm) Span 40 niosomes entrapping 98.2% of Paclitaxel with a weight percentage of 3.64% were successfully prepared. The drug–excipient interactions in niosomes were observed by differential scanning calorimetry and X-ray powder diffraction analysis. Both techniques suggest the conversion of PCTs’ crystal structure to amorphous form. The thermal analyses demonstrate the high interaction between drug and surfactant that explains high entrapment efficiency. After 3-month storage, niosomes preserved their stability in terms of drug amount and particle size. Overall, this study showed that Span 40 niosomes with desired properties can be prepared by changing the content and production variables.Key words: drug delivery systems, drug release, multiple regression, niosomes, paclitaxel     

The Influence of pH on Phosphatidylethanolamine Monolayer at the Air/Aqueous Solution Interface

The dependence of the interfacial tension of a phosphatidylethanolamine (PE) monolayer on the pH of the aqueous solution has been studied. A theoretical equation is derived to describe this dependence. A simple model of the influence of pH on the phosphatidylethanolamine monolayer at the air/hydrophobic chains of PE is presented. The contributions of additive phosphatidylethanolamine forms (both interfacial tension values and molecular area values) depend on pH. The interfacial tension values and the molecular area values for PEH⁺ and PEOH^? forms of phosphatidylethanolamine were calculated. The assumed model was verified experimentally. The experimental results agreed with those derived from the theoretical equation in a whole range of pH values.     

Formulation and Optimization of Nonionic Surfactants Emulsified Nimesulide-Loaded PLGA-Based Nanoparticles by Design of Experiments

This investigation aimed to develop nimesulide (NMS)-loaded poly(lactic-co-glycolic acid) (PLGA)-based nanoparticulate formulations as a biodegradable polymeric drug carrier to treat rheumatoid arthritis. Polymeric nanoparticles (NPs) were prepared with two different nonionic surfactants, vitamin E d-α-tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS) and poly(vinyl alcohol) (PVA), using an ultrasonication solvent evaporation technique. Nine batches were formulated for each surfactant using a 3² factorial design for optimal concentration of the emulsifying agents, 0.03–0.09% for vitamin E TPGS and 2–4% for PVA. The surfactant percentage and the drug/polymer ratio (1:10, 1:15, 1:20) of the NMS-loaded NPs were investigated based on four responses: encapsulation efficiency, particle size, the polydispersity index, and the surface charge. The response surface plots and linearity curves indicated a relationship between the experiment’s responses and a set of independent variables. The NPs produced with both surfactants exhibited a negative surface charge, and scanning electron micrographs revealed that all of the NPs were spherical in shape. A narrower size distribution and higher drug loadings were achieved in PVA-emulsified PLGA NPs than in the vitamin E TPGS emulsified. Decreasing amounts of both nonionic surfactants resulted in a reduction in the emulsion’s viscosity, which led to a decrease in the particle size of NPs. According to the ANOVA results obtained in this present research, vitamin E TPGS exhibited the best correlation between the independent variables, namely drug/polymer ratio and the surfactant percentage, and the dependent variables (encapsulation efficiency R² = 0.9603, particle size R² = 0.9965, size distribution R² = 0.9899, and surface charge R² = 0.8969) compared with PVA.KEY WORDS: ANOVA, factorial design, nanoparticles, nimesulide, PLGA, PVA, vitamin E TPGS     

The Effect of an Alternating Magnetic Field and Silver Nanoparticles on the Spectral Characteristics of an Aqueous Solution of Human Serum Albumin

Biophysics - In this paper, we discuss experimental data obtained during study of the effect of a low-frequency alternating magnetic field on the conformational transitions of human serum albumin...     

Preparation of Luminescent Plasmonic Silver Nanoparticles for Electrochemical Detection of Sulphide and Thiourea in Aqueous Solution and Ab Initio DFT Study of the Chemical Affinity Towards Silver Nanoparticles

Plasmonics - A changing of the mole ratio of L-ascorbic acid: citrate is used to synthesize coloured luminescent silver nanoparticles (AgNPs) such as AgNPs green (G), reddish green (RG) and reddish...     

Analysis of Parvovirus mRNA by Sedimentation and Electrophoresis in Aqueous and Nonaqueous Solution

Adenovirus-associated virus (AAV)-specific RNA present in the cytoplasm of cells coinfected with a helper adenovirus was analyzed by sucrose gradient sedimentation and gel electrophoresis. In aqueous conditions both gels or gradients revealed three AAV RNA components corresponding to 30S, 27S, and 20S and having apparent molecular weights of 2.6 x 10(6), 1.75 x 10(6) to 1.8 x 10(6), and 0.9 x 10(6) to 1.0 x 10(6), respectively. In nonaqueous, denaturing solvents only the 20S AAV RNA species was observed. For this reason, and because they would be apparently significantly larger than a single AAV DNA strand, both the 30S and 27S species are believed to result from conformational or aggregation effects in the aqueous nondenaturing systems. It is concluded that only a single RNA molecule having a molecular weight of approximately 0.9 x 10(6) to 1.0 x 10(6) is synthesized by AAV.     

Influence of Femtosecond Laser Ablated Silver Nanoparticles on the Nonlinear Optical Properties of Basic Fuchsin dye

We investigate the linear and nonlinear optical properties of Basic Fuchsin influenced by femtosecond laser ablated silver nanoparticles in deionised water. Single beam z-scan technique using a Q-switched Nd:YAG laser (Spectra PhysicsLAB-1760, 532 nm, 7 ns, 10 Hz) is used for the present study. Quenching of fluorescence is observed in the presence of silver nanoparticles. Transmission electron microscopic observation reveals that the nanoparticles are spherical in shape, with an average size of 7 nm. The samples show self-defocusing nonlinearity and better nonlinear absorption behavior in the presence of silver sol. The nonlinear absorption varies with varying input fluence and concentration. The results show that the variations in the nonlinear parameters are also due to the surface plasmon resonance of silver nanoparticles. The nonlinearity of the dye is increased in the presence of silver nanoparticles, which makes the material suitable for various photonic and optoelectronic applications.     

Investigation on Processing Variables for the Preparation of Fluconazole-Loaded Ethyl Cellulose Microspheres by Modified Multiple Emulsion Technique

Fluconazole-loaded ethyl cellulose microspheres were prepared by alginate facilitated (water-in-oil)-in-water emulsion technology and the effects of various processing variables on the properties of microspheres were investigated. Scanning electron microscopy revealed spherical nature and smooth surface morphology of the microspheres except those prepared at higher concentration of emulsifiers and higher stirring speeds. The size of microspheres varied between 228 and 592 μm, and as high as 80% drug entrapment efficiency was obtained depending upon the processing variables. When compared up to 2 h, the drug release in pH 1.2 HCl solution was slower than in pH 7.4 phosphate buffer saline solution. However, this trend was reversed at high shear conditions. The microspheres provided extended drug release in alkaline dissolution medium and the drug release was found to be controlled by Fickian-diffusion mechanism. However, the mechanism shifted to anomalous diffusion at high shear rates and emulsifier concentrations. The aging of microspheres did not influence the drug release kinetics. However, the physical interaction between drug and excipients affected the drug dissolution behaviors. X-ray diffractometry (X-RD) and differential scanning calorimetry (DSC) analysis revealed amorphous nature of drug in the microspheres. Fourier transform infrared (FTIR) spectroscopy indicated stable character of fluconazole in the microspheres. The stability testing data also supported the stable nature of fluconazole in the microspheres. The fluconazole extracted from 80% drug-loaded formulation showed good in vitro antifungal activity against Candida albicans. Thus, proper control of the processing variables involved in this modified multiple emulsion technology could allow effective incorporation of slightly water soluble drugs into ethyl cellulose microspheres without affecting drug stability.     

Influence of Colloidal Silicon Dioxide on Gel Strength,Robustness, and Adhesive Properties of Diclofenac Gel Formulation for Topical Application

The objective of this study is to identify the extent of stiffness, adhesiveness, and thixotropic character of a three-dimensional gel network of a 1% diclofenac sodium topical gel formulation in the presence and absence of colloidal silicon dioxide (CSD) and assess its ease of application and adhesiveness using both objective and subjective analysis. The 1% diclofenac gel was mixed with different amounts of CSD (e.g., 0.5, 1, 2, 3, and 5% w/w) and allowed to equilibrate prior to testing. The texture analyzer in combination with a cone-cap assembly was used to objectively investigate the changes in spreadability and adhesiveness of the gel system before and after addition of CSD. Results indicate that an increase in pliability and adhesiveness at levels ≥2 to ≤5% w/w of CSD dispersed in the gel ensues. For subjective analysis, gels with (2% w/w) CSD and in the absence of CSD were uniformly applied to a 20-cm² (5 cm × 4 cm) surface area on the forearms of healthy volunteers and vehicle preferences by the volunteers regarding ease of application, durability on the skin, compliance, and feelings concerning its textural properties were assessed. It appears that changes in the gel formulation with the addition of CSD enhance gel viscosity and bonding to the skin. Results further show that changes in physical and rheological characteristics of gel containing 2% w/w CSD did not significantly change subject preferences for the gel preparations. These findings may help formulators to have additional options to develop more robust and cost-effective formulations.KEY WORDS: colloidal silicon dioxide, gel-silica, texture analysis, thixotropic gel, topical gel     

Laser-Driven Precipitation and Modification of Silver Nanoparticles in Soda Lime Glass Matrix Monitored by On-line Extinction Measurements

In this work, we investigated the effect of nanosecond laser irradiation at 532?nm on precipitation of Ag nanoparticles (NPs) in soda lime glasses doped with silver in the Ag^?+??CNa^?+? ion-exchange process. Formation and subsequent modification of Ag NPs during laser irradiation were studied by on-line extinction measurements making use of the localized surface plasmon resonance (LSPR). These investigations were further completed using scanning and transmission electron microscopies to examine the average size and distribution of nanoparticles within the sample. It has been shown that formation of NPs, its kinetics and the particle size strongly depend on the fluence and the total number of deposited laser pulses. It has been found that Ag NPs form after some specific number of pulses and they rapidly grow in size and number until some maximal value of extinction has been reached. Further irradiation of such samples only results in destruction of precipitated NPs due to photo-breakup, laser ablation confirmed by strong plasma emission observation. Moreover, due to strong irradiation, the host matrix can also be affected by changing its refractive index which manifests as the blue shift of the LSPR.     

Physicochemical Characterization and Water Vapor Sorption of Organic Solution Advanced Spray-Dried Inhalable Trehalose Microparticles and Nanoparticles for Targeted Dry Powder Pulmonary Inhalation Delivery

Novel advanced spray-dried inhalable trehalose microparticulate/nanoparticulate powders with low water content were successfully produced by organic solution advanced spray drying from dilute solution under various spray-drying conditions. Laser diffraction was used to determine the volumetric particle size and size distribution. Particle morphology and surface morphology was imaged and examined by scanning electron microscopy. Hot-stage microscopy was used to visualize the presence/absence of birefringency before and following particle engineering design pharmaceutical processing, as well as phase transition behavior upon heating. Water content in the solid state was quantified by Karl Fisher (KF) coulometric titration. Solid-state phase transitions and degree of molecular order were examined by differential scanning calorimetry (DSC) and powder X-ray diffraction, respectively. Scanning electron microscopy showed a correlation between particle morphology, surface morphology, and spray drying pump rate. All advanced spray-dried microparticulate/nanoparticulate trehalose powders were in the respirable size range and exhibited a unimodal distribution. All spray-dried powders had very low water content, as quantified by KF. The absence of crystallinity in spray-dried particles was reflected in the powder X-ray diffractograms and confirmed by thermal analysis. DSC thermal analysis indicated that the novel advanced spray-dried inhalable trehalose microparticles and nanoparticles exhibited a clear glass transition (T _g). This is consistent with the formation of the amorphous glassy state. Spray-dried amorphous glassy trehalose inhalable microparticles and nanoparticles exhibited vapor-induced (lyotropic) phase transitions with varying levels of relative humidity as measured by gravimetric vapor sorption at 25°C and 37°C.