Gabriele Betz

New insights into respirable protein powder preparation using a nano spray dryer

In this study the Nano Spray Dryer B-90 (BÜCHI Labortechnik AG, Flawil, Switzerland) was evaluated with regard to the drying of proteins and the preparation of respirable powders in the size range of 1-5 μm. β-galactosidase was chosen as a model protein and trehalose was added as a stabilizer. The influence of inlet temperature, hole size of the spray cap membrane and ethanol concentration in the spray solution was studied using a 3³ full factorial design. The investigated responses were enzyme activity, particle size, span, yield and shelf life. Furthermore, the particle morphology was examined. The inlet temperature as well as the interaction of inlet temperature and spray cap size significantly influenced the enzyme activity. Full activity was retained with the optimized process. The particle size was affected by the hole size of the spray cap membrane and the ethanol content. The smallest cap led to a monodisperse particle size distribution and the greatest yield of particles of respirable size. Higher product recovery was achieved with lower inlet temperatures, higher ethanol contents and smaller cap sizes. Particle morphology differed depending on the cap size. The protein exhibited higher storage stability when spray dried without ethanol and when a larger spray cap size was used.

Interaction of liposome formulations with human skin in vitro

The interaction of liposome formulations consisting of Phospholipon 80 and sphingomyelin with human skin was investigated. These formulations were shown previously to have a composition-dependent effect on the penetration of Heparin into the skin. Fluorescence labelled phosphatidylethanolamine (PE-NBD) was incorporated in the liposomes and the depth in which the fluorescent phospholipid label enters into epidermal membrane and full thickness skin was studied by confocal laser scanning microscopy (CLSM). Confocal sections parallel to the surface of the skin were recorded in heat separated epidermis. An even distribution of phospholipid in the lipid matrix of the stratum corneum surrounding the corneocytes was observed with Phospholipon 80 but not when sphingomyelin was included in the formulation. The addition of Heparin which formed a coating around the liposomes, caused a strong localization of fluorescence within the epidermis. For full thickness skin, mechanical cross sections of skin were made and optical sections were recorded parallel to the plane of cut. Phospholipid penetrated and was distributed fairly homogeneously in the lower dermis layers within 30 min of application regardless of liposome composition and the presence of Heparin. This rather quick penetration process seemed to follow distinct pathways along the epidermis and the upper dermis, notably the hair follicle route. Thus, a strong and in some respects composition-dependent interaction of phospholipids with skin is evident. These observations, however, are limited to the level of phospholipid molecules, rather than of entire liposomes interacting with skin.

Heparin penetration into and permeation through human skin from aqueous and liposomal formulations in vitro

The transport of unfractionated (UH) and low molecular weight Heparin (LMWH) in human skin was investigated in vitro using heat separated epidermal membrane and dermis and the effect of liposomal formulations with Phospholipon(R) 80 (PL80) and Sphingomyelin (SM) was assessed. The distribution of Heparin within skin tissue was studied by the tape stripping method. Heparin concentrations were measured with a biological assay. Transepidermal water loss was determined to characterize barrier properties of skin. No consistent permeation of Heparin through epidermal membrane was detected. Penetration into the epidermal membrane was for LMWH significantly greater than for UH. Accumulation of UH was largely restricted to the outermost layers of the stratum corneum while LMWH penetrated into deeper epidermal layers. UH penetration into epidermis was detected for the PL80 liposomal formulation only. The extent of LMWH penetration was independent of the formulation, LMWH, however, showed a trend to accumulate in deeper epidermal layers for the PL80 compared to the aqueous formulation. Thus, molecular weight and liposomal formulations influenced the penetration pattern of Heparin in the epidermis. It can not be concluded whether the concentration of LMWH achieved at the blood capillaries is sufficient to exert a pharmacological effect. UH permeated readily through dermis irrespectively of formulation and its accumulation in the dermis was significantly enhanced and its lag time of permeation increased in the presence of SM liposomes.

Investigation of intrinsic dissolution behavior of different carbamazepine samples

The aim of the present study was to investigate the effect of the variability of commercially available carbamazepine (CBZ) samples on the intrinsic dissolution behavior in order to recommend a strategy to maintain product quality by monitoring the variability of critical parameters of the bulk drug. Extensive physical characterization of nine anhydrous CBZ samples from three different sources and their respective dihydrates showed that the commercial anhydrous CBZ samples exhibited the same polymorphic form, but different morphology and particle size distribution which led to a variation in the kinetics of conversion from anhydrous to the dihydrate CBZ and therefore to variation in the kinetics of solubility. Disc intrinsic dissolution rate (DIDR) tests showed different intrinsic dissolution behavior of the samples, whereby the transition points of anhydrous to dihydrate conversion varied between 15 and 25 min. On the other hand, converting the anhydrous CBZs to dihydrate eliminated the variation in intrinsic dissolution behavior. Tablets of the different CBZs and Ludipress were prepared by direct compression. The amount of CBZ dissolved after 15 min showed the same rank order as the rank order of the transition points determined by intrinsic dissolution test. Therefore, the intrinsic dissolution test with specific acceptance criteria can be a valuable and simple tool for monitoring, respectively reducing the variability of the CBZ bulk material.

Batch and continuous processing in the production of pharmaceutical granules

A quasicontinuous granulation and drying process to avoid scale-up problems is introduced in this work. Consistent and reproducible granule quality is a key factor in robust dosage form design and fits ideally the prerequisites of a drug quality system for the twenty-first century and the Food and Drug Administrations Process Analytical Technology (PAT) initiative. In scale-up, factors that simulate or reproduce the laboratory scale must be considered. This system provides a new possibility for industrial manufacturing and galenical development of pharmaceutical solids. The quasicontinuous method described in the present work, and the laboratory and production batches and the granulating equipment used to produce them, are the same. Once a robust process has been defined in the laboratory, it is merely repeated as many times as necessary to achieve the desired final batch size. The quasicontinuous process gives new possibilities to simplify manufacturing procedures and to validate them faster. The quality of the resulting granules and tablets compared with classical methods is equal until better. In many cases, existing products have been transferred to the multicell process without formulation changes. The quasicontinuous production concept for high-shear granulation and fluid-bed drying offers many advantages over the classical methods used to produce pharmaceutical granules. The wet massing process may be monitored by the power consumption of the mixer motor for each subunit, as in classical high-shear granulation processes. The air volume, temperature, and humidity of each of the drying cells may be controlled individually to avoid overheating of temperature-sensitive materials. All processing variables must be precisely controlled by a computer, and the data must be collected for documentation. As such, product quality and reproducibility for each subunit is assured.

Use of near-infrared spectroscopy to quantify drug content on a continuous blending process: Influence of mass flow and rotation speed variations

The aim of this study was to develop a quantitative Near-Infrared (NIR) method which monitors the homogeneity of a pharmaceutical formulation coming out of a continuous blender. For this purpose, a NIR diode array spectrometer with fast data acquisition was selected. Additionally, the dynamic aspects of a continuous blending process were studied; the results showed a well-defined cluster for the steady state, and the paths for the start-up and emptying stages were clearly identified. The end point of the start-up phase was detected by moving block of standard deviation, relative standard deviation, and principal component analysis. A partial least square (PLS) model was generated for the quantification of the drug, with a standard error of prediction of 0.2% m/m. The PLS model was successfully applied for monitoring the drug level at the outlet of the continuous blender. Furthermore, the PLS model was tested under different flow and stirring rates. Flow and stirring rate variations caused different powder flow dynamics, which were reflected on the NIR measurements. Therefore, the PLS model was sensitive to changes in mass flow and rotation speeds.

Investigation of different formulations for drug delivery through the nail plate.

Topical therapies for nail diseases are limited by keratinized cells in the human nail plate. An optimal permeation enhancer would not only improve drug delivery through the nail plate, but would also open new possibilities for treating neighboring target sites if systemic circulation is reached. The aim of the present work was to identify permeation enhancers and to improve the understanding of physicochemical parameters that influence drug permeation. Caffeine served as the model drug, and formulations were prepared in water and 20% (v/v) ethanol/water solutions. Tested enhancers were urea, dimethyl sulfoxide (DMSO), methanol, N-acetyl-L-cysteine (NAC), docusate sodium salt (DSS), boric acid, and fungal proteins, such as hydrophobins. Permeability studies employed cadaver nails in modified Franz-type diffusion cells. The permeability coefficient of caffeine in ethanol/water was determined to be 1.56 E-08 cm/s and was improved to 2.27 E-08 cm/s by the addition of NAC. Formulations containing either methanol or DMSO showed the highest permeability coefficients in the range of 5-7.5 E-08 cm/s. Enhancers could be classified according to their permeation enhancement: methanol>class II hydrophobins>DMSO>followed by class I hydrophobins and urea. Ethanol at a concentration of 20% (v/v) in water did not influence swelling of nail samples. Hydrophobins are suggested to be efficient in drug delivery through the nail plate.

Permeation studies of novel terbinafine formulations containing hydrophobins through human nails in vitro

Existing treatments of onychomycosis are not satisfactory. Oral therapies have many side effects and topical formulations are not able to penetrate into the human nail plate and deliver therapeutical concentrations of active agent in situ. The purpose of the present study was to determine the amount of terbinafine, which permeates through the human nail plate, from liquid formulations containing enhancers, namely hydrophobins A-C in the concentration of 0.1% (w/v). The used reference solution contained 10% (w/v) of terbinafine in 60% (v/v) ethanol/water without enhancer. Permeability studies have been performed on cadaver nails using Franz diffusion cells modified to mount nail plates and filled with 60% (v/v) ethanol/water in the acceptor chamber. Terbinafine was quantitatively determined by HPLC. The amount of terbinafine remaining in the nail was extracted by 96% ethanol from pulverized nail material after permeation experiment and presented as percentage of the dry nail weight before the milling test. Permeability coefficient (PC) of terbinafine from reference solution was determined to be 1.52E-10 cm/s. Addition of hydrophobins improved PC in the range of 3E-10 to 2E-9 cm/s. Remaining terbinafine reservoir in the nail from reference solution was 0.83% (n=2). An increase of remaining terbinafine reservoir in the nail was observed in two out of three tested formulations containing hydrophobins compared to the reference. In all cases, known minimum inhibitory concentration of terbinafine for dermatophytes (0.003 microg/ml) has been exceeded in the acceptor chamber of the diffusion cells. All tested proteins (hydrophobins) facilitated terbinafine permeation after 10 days of permeation experiment, however one of them achieved an outstanding enhancement factor of 13.05 compared to the reference. Therefore, hydrophobins can be included in the list of potential enhancers for treatment of onychomycosis.

Analysis of fluidized bed granulation process using conventional and novel modeling techniques.

Various modeling techniques have been applied to analyze fluidized-bed granulation process. Influence of various input parameters (product, inlet and outlet air temperature, consumption of liquid-binder, granulation liquid-binder spray rate, spray pressure, drying time) on granulation output properties (granule flow rate, granule size determined using light scattering method and sieve analysis, granules Hausner ratio, porosity and residual moisture) has been assessed. Both conventional and novel modeling techniques were used, such as screening test, multiple regression analysis, self-organizing maps, artificial neural networks, decision trees and rule induction. Diverse testing of developed models (internal and external validation) has been discussed. Good correlation has been obtained between the predicted and the experimental data. It has been shown that nonlinear methods based on artificial intelligence, such as neural networks, are far better in generalization and prediction in comparison to conventional methods. Possibility of usage of SOMs, decision trees and rule induction technique to monitor and optimize fluidized-bed granulation process has also been demonstrated. Obtained findings can serve as guidance to implementation of modeling techniques in fluidized-bed granulation process understanding and control.

Application of dynamic neural networks in the modeling of drug release from polyethylene oxide matrix tablets.

The main objective of this study was to demonstrate the possible use of dynamic neural networks to model diclofenac sodium release from polyethylene oxide hydrophilic matrix tablets. High and low molecular weight polymers in the range of 0.9-5 x 10(6) have been used as matrix forming materials and 12 different formulations were prepared for each polymer. Matrix tablets were made by direct compression method. Fractions of polymer and compression force have been selected as most influential factors on diclofenac sodium release profile. In vitro dissolution profile has been treated as time series using dynamic neural networks. Dynamic networks are expected to be advantageous in the modeling of drug release. Networks of different topologies have been constructed in order to obtain precise prediction of release profiles for test formulations. Short-term and long-term memory structures have been included in the design of network making it possible to treat dissolution profiles as time series. The ability of network to model drug release has been assessed by the determination of correlation between predicted and experimentally obtained data. Calculated difference (f(1)) and similarity (f(2)) factors indicate that dynamic networks are capable of accurate predictions. Dynamic neural networks were compared to most frequently used static network, multi-layered perceptron, and superiority of dynamic networks has been demonstrated. The study also demonstrated differences between the used polyethylene oxide polymers in respect to drug release and suggests explanations for the obtained results.