Electrospray encapsulation of hydrophilic and hydrophobic drugs in poly(L-lactic acid) nanoparticles.

An electrospray method is developed for preparation of beclomethasone-dipropionate- and salbutamol-sulfate-loaded biodegradable poly(L-lactic acid) nanoparticles. Different set-up parameters for electrospraying are examined on particle size, and preparation conditions are optimized for producing spherical-drug-loaded nanoscale particles by controllable processing parameters. Polylactide (PLA)-drug nanoparticles with average diameters of around 200 nm are achieved in a stable cone-jet mode with a flow rate of 4 microL min(-1), polymer concentration of 1%, and ammonium hydroxide content of 0.05%. Morphology and size of the drug-polymer nanoparticles are analyzed by scanning electron microscopy and transmission electron microscopy. Changes in the crystallinity of the PLA polymer and the model drugs are detected by X-ray powder diffraction, and the absence of molecular interactions are confirmed by thermal analyses. The results indicate clearly that electrospraying is a potential method for producing polymeric nanoparticles and for encapsulating both hydrophilic and hydrophobic drugs efficiently into the nanoparticles.

Determination of amorphous content in the pharmaceutical process environment.

The amorphous state has different chemical and physical properties compared with a crystalline one. Amorphous regions in an otherwise crystalline material can affect the bioavailability and the processability. On the other hand, crystalline material can function as nuclei and decrease the stability of an amorphous system. The aim of this study was to determine amorphous content in a pharmaceutical process environment using near infrared (NIR) and Raman spectroscopic techniques together with multivariate modelling tools. Milling was used as a model system for process-induced amorphization of a crystalline starting material, alpha-lactose monohydrate. In addition, the crystallization of amorphous material was studied by storing amorphous material, either amorphous lactose or trehalose, at high relative humidity conditions. The results show that both of the spectroscopic techniques combined with multivariate methods could be applied for quantitation. Preprocessing, as well as the sampling area, was found to affect the performance of the models. Standard normal variate (SNV) transformation was the best preprocessing approach and increasing the sampling area was found to improve the models. The root mean square error of prediction (RMSEP) for quantitation of amorphous lactose using NIR spectroscopy was 2.7%, when a measuring setup with a larger sampling area was used. When the sampling area was smaller, the RMSEPs for lactose and trehalose were 4.3% and 4.2%, respectively. For Raman spectroscopy, the RMSEPs were 2.3% and 2.5% for lactose and trehalose, respectively. However, for the optimal performance of a multivariate model, all the physical forms present, as well as the process environment itself, have to be taken into consideration.

Multivariate data analysis as a fast tool in evaluation of solid state phenomena.

A thorough understanding of solid state properties is of growing importance. It is often necessary to apply multiple techniques offering complementary information to fully understand the solid state behavior of a given compound and the relations between various polymorphic forms. The vast amount of information generated can be overwhelming and the need for more effective data analysis tools is well recognized. The aim of this study was to investigate the use of multivariate data analysis, in particular principal component analysis (PCA), for fast analysis of solid state information. The data sets analyzed covered dehydration phenomena of a set of hydrates followed by variable temperature X-ray powder diffractometry and Raman spectroscopy and the crystallization of amorphous lactose monitored by Raman spectroscopy. Identification of different transitional states upon the dehydration enabled the molecular level interpretation of the structural changes related to the loss of water, as well as interpretation of the phenomena related to the crystallization. The critical temperatures or critical time points were identified easily using the principal component analysis. The variables (diffraction angles or wavenumbers) that changed could be identified by the careful interpretation of the loadings plots. The PCA approach provides an effective tool for fast screening of solid state information.

Understanding processing-induced phase transformations in erythromycin-PEG 6000 solid dispersions.

Since the quality and performance of a pharmaceutical solid formulation depend on solid state of the drug and excipients, a thorough investigation of potential processing-induced transformations (PITs) of the ingredients is required. In this study, the physical phenomena taking place during formulation of erythromycin (EM) dihydrate solid dispersions with polyethylene glycol (PEG) 6000 by melting were investigated. PITs were monitored in situ using variable temperature X-ray powder diffraction (VT-XRPD), differential scanning calorimetry (DSC), and hot-stage microscopy (HSM). Possible intermolecular interactions between the drug and polymer in the solid state were further studied by Fourier transform infrared (FTIR) spectroscopy. While in the absence of PEG the dehydration was the only transformation observed, hot-melt processing with the polymer caused the drug to undergo multiple phase transformations (EM dihydrate --> EM dehydrate --> EM anhydrate). This alteration in phase behavior of EM was attributed to the ability of PEG in promoting nucleation and crystal growth of the EM anhydrate through a solvent-mediated route. In situ monitoring of solid dispersion formation, especially by VT-XRPD and HSM, enabled both early-stage detection of phase transformations during the hot-melt processing and better process understanding.

Crystallization of glycine with ultrasound.

Sonocrystallization has proved to be an efficient tool to influence the external appearance and structure of a crystalline product obtained by various crystallization methods. The present work focuses on high intensity sonocrystallization of glycine by varying amplitude of ultrasound with an ultrasound frequency of 20kHz at two temperature ranges 40-50 and 20-30 degrees C in a jacketed 250-ml cooling crystallizer equipped with a stirrer. The polymorph composition of the obtained crystals was analyzed with a temperature variable X-ray powder diffractometer (XRPD). XRPD results showed that, besides the operating temperature, the glycine polymorphism was affected also by insonation. This was especially the case at the lower temperature range. Furthermore, based on the heat balance within the crystallizer, an increase in required cooling capacity was presented as a function of increasing ultrasound power. This study also showed, the higher the ultrasound amplitude the smaller the crystals obtained.

Role of water in the physical stability of solid dosage formulations.

The interaction of moisture with pharmaceutical solids is highly crucial to an understanding of water-based processes, for example, manufacturing processes or prediction of solid dosage form stability and shelf life. Both the active pharmaceutical ingredient (API) and excipients in the formulation have different moisture sorption properties that can result in unexpected processing-induced phase transitions and they can affect solid-state phase transitions in the final dosage forms. The character of excipient effects on the stability of formulation. Phase transformations in formulations can lead to instability in physicochemical, biopharmaceutical, and processing properties of products. The aim of the present study was to investigate the water sorption properties of different excipients, model the sorption isotherms, examine the phase transitions, and identify differences of excipients in solid dosage form stability using dynamic vapor sorption analysis, near-infrared spectroscopy, and X-ray diffraction methods. The thermal processing was carried out with a variable temperature X-ray powder diffractometer to compare the dehydration behavior of wet excipients and evaluate solid-state properties during heating. These results showed that despite some limitations, moisture sorption isotherms of excipients are useful in predicting solid-state stability, interactions at early stages of formulation development, and effects of moisture on physicochemical properties of the final dosage forms.

Characterization of polymorphic solid-state changes using variable temperature X-ray powder diffraction.

The aim of this study was to use variable temperature X-ray powder diffraction (VT-XRPD) to understand the solid-state changes in the pharmaceutical materials during heating. The model compounds studied were sulfathiazole, theophylline and nitrofurantoin. This study showed that the polymorph form of sulfathiazole SUTHAZ01 was very stable and SUTHAZ02 changed as a function of temperature to SUTHAZ01. Theophylline monohydrate changed via its metastable form to its anhydrous form during heating and nitrofurantoin monohydrate changed via amorphous form to its anhydrous form during heating. The crystallinity of SUTHAZ01, SUTHAZ02 and theophylline monohydrate were very high and stable. Nitrofurantoin monohydrate was also very crystalline at room temperature but during heating at lower temperatures the crystallinity decreased and started to increase strongly at the temperature where the sample had changed to the anhydrous form. The average crystallite size of sulfathiazole samples varied only a little during heating. The average crystallite size of both theophylline and nitrofurantoin monohydrate decreased during heating. However, the average crystallite size of nitrofurantoin monohydrate returned back to starting size at higher temperatures. These analyses showed that VT-XRPD can be used to effectively characterize polymorphic changes during heating.

IR spectroscopy together with multivariate data analysis as a process analytical tool for in-line monitoring of crystallization process and solid-state analysis of crystalline product.

Crystalline product should exist in optimal polymorphic form. Robust and reliable method for polymorph characterization is of great importance. In this work, infra red (IR) spectroscopy is applied for monitoring of crystallization process in situ. The results show that attenuated total reflection Fourier transform infra red (ATR-FTIR) spectroscopy provides valuable information on process, which can be utilized for more controlled crystallization processes. Diffuse reflectance Fourier transform infra red (DRIFT-IR) is applied for polymorphic characterization of crystalline product using X-ray powder diffraction (XRPD) as a reference technique. In order to fully utilize DRIFT, the application of multivariate techniques are needed, e.g., multivariate statistical process control (MSPC), principal component analysis (PCA) and partial least squares (PLS). The results demonstrate that multivariate techniques provide the powerful tool for rapid evaluation of spectral data and also enable more reliable quantification of polymorphic composition of samples being mixtures of two or more polymorphs. This opens new perspectives for understanding crystallization processes and increases the level of safety within the manufacture of pharmaceutics.

Excipient selection can significantly affect solid-state phase transformation in formulation during wet granulation.

Phase transformations in formulations can lead to instability in physicochemical, biopharmaceutical, and processing properties of products. The influences of formulation design on the optimal dosage forms should be specified. The aim here was to investigate whether excipients with different water sorption behavior affect hydrate formation of nitrofurantoin in wet masses. Nitrofurantoin anhydrate was used as a hydrate-forming model drug, and 4 excipients with different water-absorbing potential (amorphous low-substituted hydroxypropylcellulose, modified maize starch, partially amorphous silicified microcrystalline cellulose, and crystalline alpha-lactose monohydrate) were granulated with varying amounts of purified water. Off-line evaluation of wet masses containing nitrofurantoin anhydrate and excipient (1:1) was performed using an X-ray powder diffractometer (XRPD) and near-infrared spectroscopy, and drying phase was evaluated by variable temperature XRPD. Only amorphous excipient in the formulation retarded hydrate formation of an active pharmaceutical ingredient (API) at high water contents. Hygroscopic partially crystalline excipient hindered hydrate formation of API at low water contents. Crystalline excipient was unable to control hydrate formation of API. The character of excipient affects the stability of formulation. Thus, correct selection of excipients for the formulation can control processing-induced phase transitions and improve the storage stability of the final dosage form.

Physical changes of beta-sitosterol crystals in oily suspensions during heating.

The aim of this research was to describe the thermal behavior of beta-sitosterol crystals in oil-suspensions with a focus on the role of water during heating. The suspensions were prepared by recrystallization in order to achieve a microcrystalline particle size. The structural changes together with the mechanical properties of the suspensions during heating were studied by using variable temperature X-ray powder diffractometry (VT-XRPD), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Hydrated beta-sitosterol crystals in an oil-suspension dehydrated, despite the composition of the suspensions, at low temperatures. At high beta-sitosterol concentration, the monohydrate crystal form changed partially to a hemihydrated form, and when only a small amount of water was initially incorporated, the hemihydrate crystal form dehydrated to a mostly anhydrate crystal form. The released water, which was immiscible in the surrounding oil, caused the recrystallization of hydrated beta-sitosterol during cooling. This procedure indicated a reversible dehydration process. Structural and thermal analysis of beta-sitosterol crystals in suspensions, together with mechanical analysis made it possible to understand various physical changes during heating.

Physical stability and moisture sorption of aqueous chitosan-amylose starch films plasticized with polyols.

The short-term stability and the water sorption of films prepared from binary mixtures of chitosan and native amylose maize starch (Hylon VII) were evaluated using free films. The aqueous polymer solutions of the free films contained 2% (w/w) film formers, glycerol, or erythritol as a plasticizer, as well as acetic acid (1%) and purified water. Characterization of the present fresh and conditioned film formers and free films was done using X-ray diffraction analysis, determination of moisture sorption isotherms, and near infrared spectroscopy. The results indicated that clear changes in the crystallinity of the films are evident within a 3-month period of storage, and the changes in the solid state are dependent on the plasticizer and storage conditions. When stored at ambient conditions for 3 months, the aqueous chitosan-amylose starch films plasticized with erythritol exhibited a partly crystalline structure. This was as a result of sugar recrystallisation due to the high hydrogen bonding. The respective films plasticized with glycerol and stored at 25 degrees C/60% relative humidity (RH) or at 40 degrees C/75% RH remained flexible and amorphous for at least 3 months. The water sorption of the free films greatly increased as a function of storage time at 75 and 95% RH. The second derivative spectra of starting material and free films were capable of distinguishing the internal water from the free water after storage at different relative humidities. Free water resulted in a separate band at a lower wavelength (1903 nm) in comparison to the structured absorbed water band at 1920 nm, in the case of films the free water resulted in a band around 1900 nm.

Effects of excipients on hydrate formation in wet masses containing theophylline.

Transformations between solid phases in dosage forms can lead to instability in drug release. Thus, it is important to understand mechanisms and kinetics of phase transformations and factors that may influence them. During wet granulation theophylline shows pseudopolymorphic changes that may alter its dissolution rate. The aim of this study was to investigate whether excipients, such as alpha-lactose monohydrate or the highly water absorbing silicified microcrystalline cellulose (SMCC) can influence the hydrate formation of theophylline. In particular, the aim was to study if SMCC offers protection against the formation of theophylline monohydrate relative to alpha-lactose monohydrate in wet masses after an overnight equilibration and the stability of final granules during controlled storage. In addition, the aim was to study the use of spectroscopic methods to identify hydrate formation in the formulations containing excipients. Off-line evaluation of materials was performed using X-ray powder diffractometry, near infrared and Raman spectroscopy. alpha-Lactose monohydrate with minimal water absorbing potential was not able to prevent but enhanced hydrate formation of theophylline. Even though SMCC is able to take large amounts of water into its internal structure, it was able to inhibit the formation of theophylline monohydrate only at low moisture contents, not at the amounts of water needed to form granules. Both the spectroscopic methods used could identify the hydrate formation even though there were excipients in the formulation.

Role of excipients in hydrate formation kinetics of theophylline in wet masses studied by near-infrared spectroscopy.

Hydrate formation is a phase transition, which can occur during wet granulation. This kind of processing-induced transformation (PIT) can influence the quality of a finished product. The aim of the study was to investigate the effect of excipients on the kinetics of hydrate formation in wet masses. Anhydrous theophylline was chosen as the hydrate-forming model drug compound and two excipients, silicified microcrystalline cellulose (SMCC) and alpha-lactose monohydrate, with different water absorbing properties, were used in formulation. An early stage of wet massing was studied with anhydrous theophylline and its 1:1 (w/w) mixtures with alpha-lactose monohydrate and SMCC with 0.1g/g of purified water. The changes in the state of water were monitored using near-infrared spectroscopy, and the conversion of the crystal structure was verified using X-ray powder diffraction (XRPD). SMCC decreased the hydrate formation rate by absorbing water, but did not inhibit it. The results suggest that alpha-lactose monohydrate slightly increased the hydrate formation rate in comparison with a mass comprising only anhydrous theophylline.

Physical stability of a microcrystalline beta-sitosterol suspension in oil.

Sterols have been shown to reduce plasma cholesterol by blocking the absorption of cholesterol from the gut. The physical properties of crystalline plant sterols limit their use in foods. A coarse-grained structure can be avoided by recrystallisation, a method that affords a reduction in the particle size. A previous work described how to produce a microcrystalline beta-sitosterol suspension. The present study deals with the stability of that suspension. Recrystallisation was carried out by two different methods; one based on rapid the other based on slow cooling, whereby six different compositions were made containing 5-30% of beta-sitosterol and secondly either 5 or 20% water was added. The particle size and habit were evaluated during a 16 weeks storage period (+4 or -19 degrees C) by way of optical microscopy. The crystal structure and degree of crystallinity was analysed by X-ray diffraction. Suspensions can, in most cases, be stored for 16 weeks without any changes to the size and habit. The only evidence of crystal growth came from a suspension with a low sterol concentration at a temperature of +4 degrees C. This is due to the dissolution-diffusion process which is affected by temperature and viscosity. Suspensions containing higher amounts of sterol remained stable, if stored at +4 or -19 degrees C, for 16 weeks. The suspensions included both hemihydrous and monohydrous beta-sitosterol crystals. Suspensions containing less sterol showed greater amounts of monohydrated crystals. This illustrates more water penetration into the crystals. A higher sterol concentration led to a larger number of smaller crystals creating reflections similar to hemihydrated crystals.

A novel method of producing a microcrystalline beta-sitosterol suspension in oil.

This paper describes a novel method of producing a microcrystalline oral suspension containing beta-sitosterol in oil for the treatment of hypercholesterolaemia. beta-Sitosterol pseudopolymorphs with different water contents were crystallized from acetone and acetone-water solutions. Structural analyses of the crystals were performed by Karl-Fisher titration, thermogravimetric analyses, X-ray diffraction and near infrared spectroscopy. The suspensions studied were composed of different concentrations of beta-sitosterol, oil and water. Suspensions were prepared by crystallization of hot concentrated solution of beta-sitosterol in oil by cooling with simultaneous agitation and water addition. The structural analyses of the suspensions were performed by X-ray diffraction, near infrared spectroscopy and optical microscopy. The viscosity of the suspensions was analysed as a function of shear stress. beta-Sitosterol was observed to exist in three different forms: anhydrous, hemihydrated and monohydrated crystals. By changing both the beta-sitosterol and the water concentration of the suspension, the crystal size and shape could be controlled. Addition of water resulted in the formation of monohydrated needle-shaped crystals instead of platy-like anhydrous crystals. Needle-shaped particles formed structured suspensions with shear thinning behaviour. By increasing the volume fraction of solid particles in suspension by increasing the water and/or sterol concentration, the viscosity increased. A high sterol concentration resulted in high supersaturation and thus formation of small crystals.

Comparison of the effects of two drying methods on polymorphism of theophylline.

Processing-induced transformations in drug formulation may induce adverse biopharmaceutical changes in the finished product. During the drying phase of wet granulation, theophylline monohydrate transforms either the stable (form I), or a polymorphic, metastable (form I(*)) form of anhydrous theophylline. We investigated the effect of two drying methods (multichamber microscale fluid bed dryer MMFD) or variable temperature X-ray powder diffractometer (VT-XRPD) on the relative amounts of the different theophylline forms remaining in the dried granules. Granules were analyzed using XRPD and near-infrared spectroscopy. Form I(*) was the predominant form of theophylline after drying at 40-50 degrees C with both drying techniques. Although drying at temperatures over 50 degrees C produced mostly form I, more than 20% of form I(*) remained even at 90 degrees C when drying in MMFD. In these conditions, humidity had little influence on the amount of form I(*) in the granules. In contrast, drying in a VT-XRPD at 60 degrees C produced form I already during the first 15min. Using additional drying methods, including MMFD, during the preformulation stage can be more informative about the possible polymorphic transformations and their underlying mechanisms, such as triboelectrification or recrystallization, in drug ingredients during the manufacturing process.

Influence of solvents on the variety of crystalline forms of erythromycin.

The influence of the organic solvents widely used in the pharmaceutical industry (acetone, methylethylketone, ethanol, and isopropanol) both in the presence and in the absence of water on the crystallization behavior of erythromycin (Em), a clinically relevant antibiotic of the macrolide group, was investigated. It was observed that despite a high preference for water as a guest molecule, Em rather easily forms solvates with the organic solvents studied. Consequently, 4 distinct solvates of Em have been isolated by recrystallization: acetonate, methylethylketonate, ethanolate, and isopropanolate. It was established that in a pure organic solvent, or 1:9 or 1:1 water-organic solvent mixtures, the corresponding solvate is always crystallized. However, the recrystallization of erythromycin from 2:1 water-organic solvent (excluding methylethylketone) mixture results in the formation of a crystal hydrate form. X-ray powder diffraction revealed the isostructurality of the solvates with acetone and methylethylketone. Thermogravimetric analysis showed that the loss of volatiles by all of the solvated crystals is nonstoichiometric. The desolvation behavior of the solvates with the organic solvents studied by means of variable-temperature x-ray powder diffraction indicates that in contrast to erythromycin dihydrate, they belong to a different class of solvates--those that produce an amorphous material upon desolvation.

Improved entrapment efficiency of hydrophilic drug substance during nanoprecipitation of poly(l)lactide nanoparticles.

The purpose of this research was to improve the entrapment efficiency of a model hydrophilic drug substance, sodium cromoglycate, loaded inside polylactic acid nanoparticles by a modified nanoprecipitation method. The effect of formulation parameters was studied to improve the entrapment efficiency of the drug substance inside the nanoparticles. Several parameters (changes in the amount of model drug, solvent selection, electrolyte addition, pH alteration) were tested in order to increase the loading of the hydrophilic drug in the hydrophobic nanoparticles. Lowering of the pH was the most efficient way to increase the drug loading; up to approximately 70% of the sodium cromoglycate used in the particle formation process could be loaded inside the particles. The loading efficiency without the pH change was around 10% to 15% at maximum. The crystallinity values and crystal habits of the sodium cromoglycate nanoparticles were studied (x-ray diffraction) before and after the lowering of the pH. The change in pH conditions during the nanoprecipitation process did not affect markedly the crystallinity properties of the drug substance. According to this study, it is possible to improve the entrapment efficiency of hydrophilic sodium cromoglycate inside of the nanoparticles by small changes in the process parameters without alterations in the physical properties of the original drug substance.

The effect of cosolvents on the formulation of nanoparticles from low-molecular-weight poly(l)lactide.

The aim of this study was to formulate nanoparticles from poly(l)lactide by a modified nanoprecipitation method. The main focus was to study the effect of cosolvent selection on the shape, size, formation efficiency, degree of crystallinity, x-ray diffraction (XRD) reflection pattern, and zeta potential value of the particles. Low-molecular-weight (2000 g/mol) poly(l)lactide was used as a polymer, and sodium cromoglycate was used as a drug. Acetone, ethanol, and methanol were selected as cosolvents. Optimal nanoparticles were achieved with ethanol as a cosolvent, and the formation efficiency of the particles was also higher with ethanol as compared with acetone or methanol. The particles formulated by ethanol and acetone appeared round and smooth, while with methanol they were slightly angular. When the volume of the inner phase was decreased during the nanoprecipitation process, the mean particle size was also decreased with all the solvents, but the particles were more prone to aggregate. The XRD reflection pattern and the degree of crystallinity were more dependent on the amount of the solvents in the inner phase than on the properties of the individual cosolvents. The zeta potential values of all the particle batches were slightly negative, which partially explains the increased tendency toward particle aggregation.

Solid-state and mechanical properties of aqueous chitosan-amylose starch films plasticized with polyols.

The film-forming ability of chitosan and binary mixtures of chitosan and native amylose corn starch (Hylon VII) was evaluated with free films prepared by a casting/solvent evaporation method. Unplasticized and plasticized free chitosan films in aqueous acetic acid and respective films containing a mixture of chitosan and native amylose starch in acetic acid were prepared. Glycerol, sorbitol, and i-erythritol were used as plasticizers. Solid-state and mechanical properties of the films were studied by powder x-ray diffractometry (XPRD), differential scanning calorimetry (DSC), and a materials testing machine. The films composed of a mixture of chitosan and native amylose starch in acetic acid were clear and colorless. A plasticizer concentration of 20% wt/wt (of the polymer weight) was sufficient to obtain flexible films with all samples tested. X-ray diffraction patterns and DSC thermograms indicated an amorphous state of the films independent of the type of plasticizer used. In conclusion, incorporation of native amylose corn starch into chitosan films improves the consistency and the mechanical properties of the films.