European Journal of Pharmaceutics and Biopharmaceutics (v.78, #1)

APV Diary (I).

A review about the state of the art of drug nanocrystals about 20 years after their invention; covering their special features, production methods, as well as nanotoxicology aspects (including a suggestion of a Nanotoxicological Classification System); intracellular delivery.Drug nanocrystals are the latest, broadly introduced nanoparticulate carrier to the pharmaceutical market from the year 2000 onwards. The special features of nanocrystals for the delivery of poorly soluble drugs are briefly reviewed (saturation solubility, dissolution velocity, adhesiveness). The industrially relevant bottom up (precipitation) and top down production technologies (pearl milling, high pressure homogenization, combination technologies) are presented. As nanotoxicological aspects, the effect of size, degradability versus biopersistency and intracellular uptake are discussed, classifying the nanocrystals in the low/non-risk group. Intracellular uptake plays a minor or no role for dermal and oral nanocrystals, but it plays a key role for intravenously injected nanocrystals (e.g. nevirapine, paclitaxel, itraconazole). Uptake by the macrophages of the mononuclear phagocytic system (MPS, liver spleen) can modify/optimize blood profiles via prolonged release from the MPS (itraconazole), but also target toxicity by too high organ concentrations and thus cause nanotoxicity. The balance in the competitive intracellular uptake by MPS and the target cells (e.g. blood–brain barrier) decides about therapeutic efficiency. The concept of “differential protein adsorption” to modulate this balance is shown for its applicability to nanocrystals for intracellular delivery to the cells of the blood–brain barrier (atovaquone).
Keywords: Nanocrystals; Nanosuspensions; High pressure homogenization; Precipitation; Smartcrystals; Review;

Colloidal polyelectrolyte complexes from Chitosan and Dextran Sulfate are formed by charge neutralization in aqueous media, without toxic chemical nor emulsification step. Hence, a great variety of bio-active molecules can be associated to these versatile carriers for potentially a large number of applications in nanomedicine.Nanomedicine is an emerging field and requires new tools to achieve its goals, such as nanomaterials capable of performing various functions as bioactive (macro)molecule delivery in a spatio- and time-controlled manner, biofeedback as for instance imaging the course of a therapeutic treatment, active and controlled interaction with the biological environment as in vaccine applications. Obviously, these nanomaterials should be non-toxic, biocompatible, bioresorbable, which means also that the materials and the manufacturing processes should meet these requirements. This review is focused on colloidal polyelectrolyte complexes of chitosan and dextran sulfate, (i) because these polysaccharides comply with the above specifications; (ii) because chitosan is a complex polysaccharide whose physicochemical properties depend on the molar mass and the fraction of N-acetyl glucosamine moieties within the chain; (iii) to underline the impact of the physicochemical properties of chitosan on the performances of the colloidal complexes; (iv) to establish the versatility of the coarcervation, a mild, energy-sparing, environment friendly, straightforward to set-up manufacturing process.
Keywords: Chitosan; Dextran sulfate; Complexes; Colloids; Delivery; Vaccine;

Calu-3 cells grown under AIC and LCC conditions: Implications for dipeptide uptake and transepithelial transport of substances by Anna Stentebjerg-Andersen; Ingrid Vedsted Notlevsen; Birger Brodin; Carsten Uhd Nielsen (19-26).
Carrier-mediated Gly-Sar uptake in Calu-3 cells grown under AIC or LCC culture conditions for 17 days.The aim of the present study was to investigate whether Calu-3 cell culture conditions influence drug and nutrient transport known to occur via carriers or transporters. Calu-3 cell layers, an in vitro model of the lung epithelium, were cultured using air interfaced culture (AIC) or liquid covered culture (LCC) on either polycarbonate or polyester as filter support material. We found that the development of the Calu-3 cell layer barrier function did not depend on the filter material but rather on the culture conditions as follows: (i) the apical uptake of Gly-Sar was significantly larger for cells grown in AIC compared to LCC, (ii) the TEER values for cells grown in LCC were approximately three times larger than for cells grown in AIC, (iii) the transepithelial transport in both AIC and LCC Calu-3 cells was polarized in the apical–basolateral direction of proline, glycine, α-methyl-d-glucoside, glipizide, taurocholic acid and estrone-3-sulfate, whereas inulin, mannitol and Gly-Sar showed no polarized transport. Etoposide showed polarized efflux (basolateral to apical transport) in AIC and LCC Calu-3 layers. These findings provide information about nutrient and drug transport in Calu-3 cells, and this may have implications for selecting culture conditions for transport studies in this in vitro model of the lung epithelium.
Keywords: Calu-3 cells; Liquid-covered culture (LCC); Air-interfaced culture (AIC); Pulmonary drug delivery; Gly-Sar; Peptide transporters (hPEPT1);

Ex vivo skin delivery of diclofenac by transcutol containing liposomes and suggested mechanism of vesicle–skin interaction by Maria Manconi; Carla Caddeo; Chiara Sinico; Donatella Valenti; Maria Cristina Mostallino; Giovanni Biggio; Anna Maria Fadda (27-35).
Novel transcutol containing PEVs showed to be suitable carriers for dermal delivery of diclofenac. Confocal Laser Scanning Microscopy was also used to visualize vesicle-skin interactions.Recently, we described a novel family of liposomes, the Penetration Enhancer-containing Vesicles (PEVs), as carriers for enhanced (trans)dermal drug delivery. In this study, to go deeply into the potential of these new vesicles and suggest the possible mechanism of vesicle–skin interaction, we investigated transcutol containing PEVs as carriers for diclofenac, in the form of either acid or sodium salt. PEVs, prepared with soy phosphatidylcholine and aqueous solutions containing different concentrations of transcutol, were characterized by size distribution, zeta potential, incorporation efficiency, thermotropic behavior, and stability. (Trans)dermal diclofenac delivery from PEVs was investigated ex vivo through new born pig skin using conventional liposomes and a commercial gel as controls. The mode of action of the vesicles was also studied by performing a pre-treatment test and confocal laser scanning microscopy (CLSM) analyses. Results of the all skin permeation experiments showed an improved diclofenac (both acid and sodium salt) delivery to and through the skin when PEVs were used (especially in comparison with the commercial gel) thus suggesting intact PEVs’ penetration through the pig skin. Images of the qualitative CLSM analyses support this conclusion. Thus, this work shows the superior ability of the PEVs to enhance ex vivo drug transport of both hydrophilic and lipophilic diclofenac forms.
Keywords: Liposome; Transcutol; Rheology; (Trans)dermal delivery; Confocal laser scanning microscopy; Vesicle–skin interaction;

Examination of drug release and distribution from drug-eluting stents with a vessel-simulating flow-through cell by Anne Seidlitz; Stefan Nagel; Beatrice Semmling; Niels Grabow; Heiner Martin; Volkmar Senz; Claus Harder; Katrin Sternberg; Klaus-Peter Schmitz; Heyo K. Kroemer; Werner Weitschies (36-48).
Analysis of release and distribution from drug-eluting stents via finite element methods and comparison of the obtained data to experimental results.The recently introduced vessel-simulating flow-through cell offers new possibilities to examine the release from drug-eluting stents in vitro. In comparison with standard dissolution methods, the additional compartment allows for the examination of distribution processes and creates dissolution conditions which simulate the physiological situation at the site of implantation. It was shown previously that these conditions have a distinct influence on the release rate from the stent coating. In this work, different preparation techniques were developed to examine the spatial distribution within the compartment simulating the vessel wall. These methods allowed for the examination of diffusion depth and the distribution resulting in the innermost layer of the compartment simulating the vessel wall. Furthermore, the in vitro release and distribution examined experimentally were modelled mathematically using finite element (FE) methods to gain further insight into the release and distribution behaviour. The FE modelling employing the experimentally determined diffusion coefficients yielded a good general description of the experimental data. The results of the modelling also provided important indications that inhomogeneous coating layer thicknesses around the strut may result from the coating process which influence release and distribution behaviour.Taken together, the vessel-simulating flow-through cell in combination with FE modelling represents a unique method to analyse drug release and distribution from drug-eluting stents in vitro with particular opportunities regarding the examination of spatial distributions within the vessel-simulating compartment.
Keywords: Drug-eluting stent; In vitro dissolution; Vessel-simulating flow-through cell; Finite element modelling; Spatial distribution; Vessel-simulating compartment;

Zero-order release of 5-fluorouracil from PCL-based films featuring trilayered structures for stent application by Lei Lei; Xi Liu; Yuan-Yuan Shen; Jie-Ying Liu; Mu-Fei Tang; Zhong-Min Wang; Sheng-Rong Guo; Liang Cheng (49-57).
The trilayered PCL films can load drug in the middle layer or in both the middle layer and the top coating layer, and they can release drug in highly tunable behaviors (in some cases, in zero-order manners). The drug release can be adjusted by changing the compositions of the three separate layers.A trilayered Poly(ε-caprolactone) (PCL)-based film with a coating layer (CL), a drug-storing layer (DSL) loaded with antitumor drug 5-Fluorouracil (5-FU) and a backing layer (BL) are presented for film-based stent application in malignant stricture or stenosis. V-C diffusion cells were used to investigate the drug permeability of the CL, while scanning electron microscopy (SEM) was employed for observing the microscopic architectures and morphologies. Drug release from the trilayered films exhibited a zero-order pattern, and the release process followed an ‘outer-to-inner’ pattern. The formation mechanism and influencing factors of the zero-order drug release pattern were in-depth elucidated, and factors affecting the drug release were also investigated. The reduction of initial drug loading in DSL slowed the drug release and diminished the zero-order release pattern. Drug permeability of the CL depended significantly on CL thickness, but not significantly on PCL molecular weight. Besides, the addition of PEG porogen in the CL accelerated the drug release by elevation of the drug permeability of CL, and the action mechanism of PEG was revealed by the PEG release test and SEM. The loading of 5-FU in the CL could lead to a two-phased release profile. This study revealed the potential of the trilayered film in controlled drug delivery to intraluminal tumor due to its highly tunable zero-order drug release.
Keywords: Film; Poly(ε-caprolactone) (PCL); 5-Fluorouracil (5-FU); Controlled drug delivery; Scanning electron microscopy (SEM);

Comparison of ibuprofen release from minitablets and capsules containing ibuprofen: β-Cyclodextrin complex by P.J. Salústio; H.M. Cabral-Marques; P.C. Costa; J.F. Pinto (58-66).
Complexes drug: β-cyclodextrin were not affected by further processing into minitablets and capsules.Mixtures containing ibuprofen (IB) complexed with β-cyclodextrin (βCD) obtained by two complexation methods [suspension/solution (with water removed by air stream, spray- and freeze-drying) and kneading technique] were processed into pharmaceutical dosage forms (minitablets and capsules). Powders (IB, βCD and IBβCD) were characterized for moisture content, densities (true and bulk), angle of repose and Carr’s index, X-ray and NMR. From physical mixtures and IBβCD complexes without other excipients were prepared 2.5-mm-diameter minitablets and capsules. Minitablets were characterized for the energy of compaction, tensile strength, friability, density and IB release (at pH 1.0 and 7.2), whereby capsules were characterized for IB release. The results from the release of IB were analyzed using different parameters, namely, the similarity factor (f 2), the dissolution efficiency (DE) and the amounts released at a certain time (30, 60 and 180 min) and compared statistically (α  = 0.05). The release of IB from the minitablets showed no dependency on the amount of water used in the formation of the complexes. Differences were due to the compaction force used or the presence of a shell for the capsules. The differences observed were mostly due to the characteristics of the particles (dependent on the method considered on the formation of the complexes) and neither to the dosage form nor to the complex of the IB.
Keywords: β-Cyclodextrin; Capsule; Compaction; Dissolution; Ibuprofen; Minitablet;

Plasma deposited stability enhancement coating for amorphous ketoprofen by Stephanie Bosselmann; Donald E. Owens; Rachel L. Kennedy; Matthew J. Herpin; Robert O. Williams (67-74).
Application of hydrophobic barrier coating via pulsed plasma-enhanced chemical vapor deposition.A hydrophobic fluorocarbon coating deposited onto amorphous ketoprofen via pulsed plasma-enhanced chemical vapor deposition (PPECVD) significantly prolonged the onset of recrystallization compared to uncoated drug. Rapid freezing (RF) employed to produce amorphous ketoprofen was followed by PPECVD of perfluorohexane. The effect of coating thickness on the recrystallization and dissolution behavior of ketoprofen was investigated. Samples were stored in open containers at 40 °C and 75% relative humidity, and the onset of recrystallization was monitored by DSC. An increase in coating thickness provided enhanced stability against recrystallization for up to 6 months at accelerated storage conditions (longest time of observation) when compared to three days for uncoated ketoprofen. Results from XPS analysis demonstrated that an increase in coating thickness was associated with improved surface coverage thus enabling superior protection. Dissolution testing showed that at least 80% of ketoprofen was released in buffer pH 6.8 from all coated samples. Overall, an increase in coating thickness resulted in a more complete drug release due to decreased adhesion of the coating to the substrate.
Keywords: Plasma-enhanced chemical vapor deposition; Amorphous drug; Recrystallization; Physical stability; Fluorocarbons;

Synthesis and intestinal transport of the iron chelator maltosine in free and dipeptide form by Stefanie Geissler; Michael Hellwig; Fritz Markwardt; Thomas Henle; Matthias Brandsch (75-82).
The oral bioavailability of the iron chelator maltosine might be increased by applying this drug candidate in peptide-bound form. Alanylmaltosine and maltosinylalanine are transported by the intestinal proton-coupled peptide transporter 1 (PEPT1) into intestinal cells.Maltosine, a 3-hydroxy-4-pyridinone derivative of lysine formed in the course of the advanced Maillard reaction, is an effective metal chelating agent. It therefore represents an interesting compound for the treatment of metal ion storage diseases. We synthesized 6-(3-hydroxy-4-oxo-2-methyl-4(1H)-pyridin-1-yl)-l-norleucine (free maltosine) and its dipeptide derivatives alanylmaltosine (Ala-Mal) and maltosinylalanine (Mal-Ala) and examined the transepithelial flux of these compounds across Caco-2 cells and their interaction with membrane transporters. Transepithelial flux of maltosine was significantly higher when added as Ala-Mal and Mal-Ala than in free form. Assays at Caco-2 cells and at HeLa cells expressing the human peptide transporter (hPEPT)1 revealed that Ala-Mal and Mal-Ala show medium to high affinity to the system. Only free but not peptide-bound maltosine inhibited the uptake of l-[3H]lysine in Caco-2 and OK cells. Maltosine dipeptides were transported by hPEPT1 across cell membranes and accumulated in hPEPT1-transfected HeLa cells. In electrophysiological measurements at hPEPT1-expressing Xenopus laevis oocytes, Ala-Mal and Mal-Ala induced significant inward directed currents. We conclude that Ala-Mal and Mal-Ala are transported by hPEPT1 into intestinal cells and then hydrolyzed to free maltosine and alanine. The results suggest that the oral bioavailability of maltosine can be increased significantly by applying this drug candidate in peptide-bound form.
Keywords: Maillard reaction; Intestine; PEPT1; Iron chelator; 3-Hydroxy-4-pyridinone; Prodrug;

Modelling of molecular phase transitions in pharmaceutical inhalation compounds: An in silico approach by Heba Abdel-Halim; Daniela Traini; David Hibbs; Simon Gaisford; Paul Young (83-89).
Molecular dynamic simulations have been successfully utilised with molecular modelling to estimate the glass transition temperature of a small drug molecule (beclomethasone dipropionate). Simulation results were in good agreement with solid-state experientially determined values. This approach opens up the opportunity to study fundamental properties and the behaviour of amorphous systems with respect to drug development (for example diffusion properties or the influence of impurities).Molecular dynamic simulations have been successfully utilised with molecular modelling to estimate the glass transition temperature (T g) of polymers. In this paper, we use a similar approach to predict the T g of a small pharmaceutical molecule, beclomethasone dipropionate (BDP). Amorphous beclomethasone dipropionate was prepared by spray-drying. The amorphous nature of the spray-dried material was confirmed with scanning electron microscopy, differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD). Molecular models for amorphous BDP were constructed using the amorphous cell module in Discovery studio™. These models were used in a series of molecular dynamic simulations to predict the glass transition temperature. The T g of BDP was determined by isothermal-isobaric molecular dynamic simulations, and different thermodynamic parameters were obtained in the temperature range of −150 to 400 °C. The discontinuity at a specific temperature in the plot of temperature versus amorphous cell volume (V) and density (ρ) was considered to be the simulated T g. The predicted T g from four different simulation runs was 63.8 °C ± 2.7 °C. The thermal properties of amorphous BDP were experimentally determined by DSC and the experimental T g was found to be ∼65 °C, in good agreement with computational simulations.
Keywords: Amorphous; Beclomethasone dipropionate; Glass transition temperature; Molecular dynamic simulations;

Surfactant-free redispersible nanoparticles in fast-dissolving composite microcarriers for dry-powder inhalation by Tobias Lebhardt; Susanne Roesler; Henna P. Uusitalo; Thomas Kissel (90-96).
Stabilization of PLGA-nanoparticle suspensions by spray-drying with α-cyclodextrin yielded microcarriers suitable for inhalation. Upon addition of water the carrier disintegrate into redispersible particles smaller than 200 nm.Spray-drying was investigated for the stabilization of surfactant-free nanoparticles as carriers for dry-powder inhalers. The microparticles rapidly dissolve after inhalation yielding dispersed nanoparticles.Nanoparticles were prepared by a solvent displacement technique avoiding any surfactants. Microcarriers were prepared by spray-drying nanoparticle suspensions with lactose, mannitol or α-cyclodextrin as stabilizers. Nanoparticle size and ζ-potential before and after spray-drying were analyzed with photon correlation spectroscopy and laser Doppler anemometry, respectively. Cell uptake into macrophages was studied using U 937 cells by confocal microscopy.Stabilization of nanoparticle suspensions by spray-drying with α-cyclodextrin yielded redispersible particles smaller than 200 nm. α-Cyclodextrin was a more efficient stabilizer than commonly used excipients. Microparticles with a mass median aerodynamic diameter of 4.3 μm showed properties suitable for dry-powder inhalation. The cell culture experiments with redispersed nanoparticles seem to suggest less interaction and uptake with macrophages compared to polymeric microparticles.In conclusion, nanoparticles can easily be transferred to dry-powders suitable for inhalation by spray-drying. This allows the pulmonary application of nanoparticles in high concentrations.
Keywords: Redispersible biodegradable nanoparticles; Poly (lactide-co-glycolide); Spray-drying; Microparticles; Dry-powder inhalation;

A lactose monohydrate particle compressed (pre-blend) with 15 kPa for 15 min exhibiting the effects of mild compression, as illustrated by the ridge of compacted lactose fines.Batch-to-batch variability, whereby distinct batches of dry powder inhaler formulations, though manufactured with identical components and specifications, may exhibit significant variations in aerosol performance, is a major obstacle to consistent and reproducible drug delivery for inhalation therapy. This variability may arise from processing or manufacturing effects that have yet to be investigated. This study focused on the potential effects of mild compression forces experienced during powder manufacture and transport (such as during the filling of, or storage in, a hopper) on the flowability and aerosol performance of a lactose-based dry powder inhaler formulation. Different grades of inhalation lactose were subjected to typical compression forces by either placing a weight of known mass on the sample or by using a Texture Analyzer to apply a constant force while measuring the distance of compaction. Powder flowability was evaluated with a rotating drum apparatus by imaging the avalanching of the powder over time. The average avalanche angle and avalanche time were used to determine the flowability of each sample, both before and after compression treatment. Aerosol performance of treated and untreated lactose/budesonide blends (2% (w/w)) was assessed in dispersion studies using a next generation impactor. At compression forces in excess of 5 kPa, the flowability of milled lactose was decreased relative to the untreated sample. Compression of lactose prior to blending caused a decrease in in vitro aerosol dispersion performance. However, dispersion performance was unchanged when compression occurred subsequent to drug blending. In contrast, inhalation grade sieved lactose, differing from the milled grade with a lower concentration of lactose fines (<10 μm) and larger overall particle sizes, exhibited no statistical differences in either flowability or dispersion performance across all experimental treatments. Thus, the compression of the lactose fines onto the surfaces of the larger lactose particles due to mild processing pressures is hypothesized to be the cause of these observed performance variations. It was shown that simulations of storage and transport in an industrial scale hopper can induce significant variations in formulation performance, and it is speculated that this could be a source of batch-to-batch variations.
Keywords: Lactose; Batch-to-batch variation; Dry powder inhalers; Formulations; Compression; Budesonide;

Except particle size difference, the small 230 nm and large 708 nm OVA-nanoparticles engineered from lecithin/GMS-in-water emulsions were not different in other formulation parameters, but the former induced stronger antibody and cellular immune responses than the later.There is a growing interest in identifying the relationship between the size of nanoparticles and their adjuvant activity, but the results from recent studies remain controversial. To address the controversy, it was thought that one should pay attention to the nanoparticle formulations to make sure that the antigen-loaded nanoparticles to be compared are not only different in particle size, but more importantly, as identical to each other as possible in all other formulation properties. In the present study, using ovalbumin (OVA) as a model antigen conjugated onto nanoparticles engineered from lecithin/glyceryl monostearate-in-water emulsions, we prepared OVA-nanoparticles of 230 nm and 708 nm. Before evaluating the immune responses induced by them in a mouse model, we made sure that: (i) the sizes of the two OVA-nanoparticles did not extensively overlap, (ii) the nanoparticles have similar zeta potentials and comparable antigen-loading, and (iii) the nanoparticles did not aggregate when suspended in simulated biological media. We then showed that when subcutaneously injected into mice, the 230 nm OVA-conjugated nanoparticles induced stronger OVA-specific antibody and cellular immune responses than the 708 nm OVA-nanoparticles. Future studies attempting to correlate the size of nanoparticles and their adjuvant activities need to consider formulation parameters to ensure that the particles are different only in size and are stable before and after injection.
Keywords: Immune responses; Tumor treatment; Particle uptake; Particle trafficking;

Workflow of Symmetry Parameter Image Analysis (SPIA).Near-Infrared Chemical Imaging (NIR-CI) is rapidly gaining importance for the analysis of complex intermediate and final drug products. The availability of both spectral information from the sample and spatial information on the distribution of individual components offers access to greater understanding of manufacturing processes in many stages of pharmaceutical production. One major aspect in terms of chemical imaging is data analysis, since each measurement (image) generates a data cube containing several thousands of spectra (i.e., one spectrum per image pixel). The visual interpretation of component distribution (e.g., homogeneity) is an important issue but subjective. Chemometric methods are therefore required to extract qualitative and quantitative information from each image and enable comparison of several images. In this work, we describe a novel approach for the statistical evaluation of NIR-CI in terms of a multivariate treatment of univariate statistical descriptors characterizing image pixel (e.g., skewness and kurtosis). This technique was called by the authors “Symmetry Parameter Image Analysis” (SPIA), since it enables assessing the symmetry of pixel distributions in terms of different sample attributes. That approach is an innovative way of reporting results with a straightforward relation with attributes such as homogeneity, thus providing the basis for setting up acceptance criteria for good processing conditions or sample homogeneity. Furthermore, this procedure is applicable to determine product variability for large data sets without the need for explicit consideration of each image as its main attributes have been captured by the pixel distributions and their univariate descriptors.The approach is described by means of data obtained by NIR-CI on a powder blend case study (process application). Additionally, SPIA was used for the qualitative classification of tablets (sample application), showing that the approach can be generalized to set up criteria for sample-to-sample similarity and be useful in establishing criteria for e.g., counterfeiting.
Keywords: NIR-CI; QbD; MVA; Homogeneity; Skewness; Kurtosis;

Polymer and substance release – HPMC- and HPMCAS-based formulations.One of the drawbacks with solid solution systems is their thermodynamic instability in solution. Considering the release of these systems from extended-release formulations, in particular swellable matrix tablets, a successful tablet formulation can be regarded as a composition able to maintain the molecular state of the poorly soluble crystalline drug through diffusion in the matrix. This may in turn provide molecular rather than particulate delivery of the substance from the matrix. In this study, the solid state and dissolution behavior of amorphous solid dispersions of a model crystalline substance, butyl paraben in HPMC and HPMCAS, was investigated. In addition, the suitability of HPMCAS as both effective solid solution carrier and as extended-release matrix forming polymer was examined. The release from all systems investigated showed extended-release capacity with a release rate similar to the rate of matrix erosion. However, a detailed study of the factors affecting the release mechanism revealed that upon hydration, the model substance crystallized in the gel layer of the HPMC-based formulation, whereas it remained in amorphous form in the HPMCAS tablets. In the case of HPMCAS formulation, this effect was attributed to (i) the ability of this polymer to keep the model substance in a supersaturated state and (ii) the very slow matrix hydration, resulting in a steep concentration gradient of the drug substance and a short diffusion path through the matrix into the dissolution bulk.
Keywords: Solid solutions; Supersaturation; HPMC; HPMCAS; Swellable matrix tablets; Metastable zone;

Microporous bilayer osmotic tablet for colon-specific delivery by Anil Chaudhary; Neha Tiwari; Vikas Jain; Ranjit Singh (134-140).
Microporous bilayer osmotic tablet bearing dicyclomine hydrochloride and diclofenac potassium was developed using a new oral drug delivery system for colon targeting. The tablets were coated with microporous semipermeable membrane and enteric polymer using conventional pan-coating process. The developed microporous bilayer osmotic pump tablet (OPT) did not require laser drilling to form the drug delivery orifice. The colon-specific biodegradation of pectin could form in situ delivery pores for drug release. The effect of formulation variables like inclusion of osmogen, amount of HPMC and NaCMC in core, amount of pore former in semipermeable membrane was studied. Scanning electron microscopic photographs showed formation of in situ delivery pores after predetermined time of coming in contact with dissolution medium. The number of pores was dependent on the amount of the pore former in the semipermeable membrane. In vitro dissolution results indicated that system showed acid-resistant, timed release and was able to deliver drug at an approximate zero order up to 24 h. The developed tablets could be effectively used for colon-specific drug delivery to treat IBS.
Keywords: Microporous bilayer osmotic tablet; Irritable bowel syndrome; Colon-specific biodegradation; Conventional manufacturing methods;

Multi-way principal component analysis (MPCA) of 3D dissolution profiles upon stability.This paper presents the use of experimental design, optimization and multivariate techniques to investigate root-cause of tablet dissolution shift (slow-down) upon stability and develop control strategies for a drug product during formulation and process development. The effectiveness and usefulness of these methodologies were demonstrated through two application examples. In both applications, dissolution slow-down was observed during a 4-week accelerated stability test under 51 °C/75%RH storage condition. In Application I, an experimental design was carried out to evaluate the interactions and effects of the design factors on critical quality attribute (CQA) of dissolution upon stability. The design space was studied by design of experiment (DOE) and multivariate analysis to ensure desired dissolution profile and minimal dissolution shift upon stability. Multivariate techniques, such as multi-way principal component analysis (MPCA) of the entire dissolution profiles upon stability, were performed to reveal batch relationships and to evaluate the impact of design factors on dissolution. In Application II, an experiment was conducted to study the impact of varying tablet breaking force on dissolution upon stability utilizing MPCA. It was demonstrated that the use of multivariate methods, defined as Quality by Design (QbD) principles and tools in ICH-Q8 guidance, provides an effective means to achieve a greater understanding of tablet dissolution upon stability.
Keywords: Dissolution; Stability; Chemometrics; Multi-way principal component analysis (MPCA); Quality by Design (QbD); Multivariate; Design of experiments (DOE);

Evolution of a physiological pH 6.8 bicarbonate buffer system: Application to the dissolution testing of enteric coated products by Fang Liu; Hamid A. Merchant; Rucha P. Kulkarni; Maram Alkademi; Abdul W. Basit (151-157).
Realistic and discriminative in vitro release in pH 6.8 [B] physiological bicarbonate buffer compared to [A] compendial phosphate buffer for enteric coated formulations.The use of compendial pH 6.8 phosphate buffer to assess dissolution of enteric coated products gives rise to poor in vitroin vivo correlations because of the inadequacy of the buffer to resemble small intestinal fluids. A more representative and physiological medium, pH 6.8 bicarbonate buffer, was developed to evaluate the dissolution behaviour of enteric coatings. The bicarbonate system was evolved from pH 7.4 Hanks balanced salt solution to produce a pH 6.8 bicarbonate buffer (modified Hanks buffer, mHanks), which resembles the ionic composition and buffer capacity of intestinal milieu. Prednisolone tablets were coated with a range of enteric polymers: hypromellose phthalate (HP-50 and HP-55), cellulose acetate phthalate (CAP), hypromellose acetate succinate (HPMCAS-LF and HPMCAS-MF), methacrylic acid copolymers (EUDRAGIT® L100-55, EUDRAGIT® L30D-55 and EUDRAGIT® L100) and polyvinyl acetate phthalate (PVAP). Dissolution of coated tablets was carried out using USP-II apparatus in 0.1 M HCl for 2 h followed by pH 6.8 phosphate buffer or pH 6.8 mHanks bicarbonate buffer. In pH 6.8 phosphate buffer, the various enteric polymer coated products displayed rapid and comparable dissolution profiles. In pH 6.8 mHanks buffer, drug release was delayed and marked differences were observed between the various coated tablets, which is comparable to the delayed disintegration times reported in the literature for enteric coated products in the human small intestine. In summary, the use of pH 6.8 physiological bicarbonate buffer (mHanks) provides more realistic and discriminative in vitro release assessment of enteric coated formulations compared to compendial phosphate buffer.
Keywords: pH-sensitive polymers; Enteric coatings; Modified release; Physiological buffers; Bicarbonate media; Biorelevant dissolution;

Online monitoring of dissolution tests using dedicated potentiometric sensors in biorelevant media by Daniel Juenemann; Hugo Bohets; Mahir Ozdemir; Roy de Maesschalck; Koen Vanhoutte; Karl Peeters; Luc Nagels; Jennifer B. Dressman (158-165).
An Ion-selective Electrode is set into a standard dissolution vessel (USP II apparatus). The electrode monitors the dissolution of a tablet by detecting changes in the electrochemical potential of the dissolution medium caused by the dissolving drug. These changes, measured in mV, are converted via a dedicated software (“Potential to Concentration”) into the concentration in % of dissolved drug. The results are compared to manual sampling with subsequent sample analysis using HPLC-UV. The results using analysis via the Ion Selective electrode are comparable to those with the conventional sample preparation.The performance of the Ion-Selective Electrode (ISE) for in vitro dissolution testing using biorelevant media was evaluated in this study. In vitro dissolution was carried out using USP apparatus 2 (paddle method) with classical and with updated biorelevant media to simulate the pre- and postprandial states. The ISE was used as an analytical stand-alone system and in combination with a single-point HPLC–UV measurement. A modified method enabling the use of the ISE for very poorly soluble substances is also proposed.In terms of f 2-factor, the results acquired using the ISE for the drug diphenhydramine-HCl were found to be very similar to the results obtained by manual sampling followed by HPLC–UV analysis. In Fed State Simulated Gastric Fluid (FeSSGF), a medium containing 50% milk, the ISE is more practical since the need to separate proteins from the analyte prior to HPLC–UV analysis is eliminated. Further work will be needed to establish ISE methodology for Fed State Simulated Intestinal Fluid (FeSSIF) media.In summary, the ISE has promise as an analytical tool for research and development applications.
Keywords: Ion-Selective Electrode; Online monitoring; In situ dissolution; Biorelevant media; Online measurement; Electrodes;

Effects of non-ionic surfactants on cytochrome P450-mediated metabolism in vitro by Anne Christiansen; Thomas Backensfeld; Karsten Denner; Werner Weitschies (166-172).
Non-ionic surfactants like polysorbate 80 inhibit the CYP3A4 mediated hydroxylation of testosterone and the CYP2C9 mediated hydroxylation of diclofenac.The purpose of the study was to investigate the impact of commonly used non-ionic surfactants on cytochrome P450 (CYP) 3A4-mediated metabolism of testosterone and the CYP2C9-mediated metabolism of diclofenac. Polysorbate 80 (PS 80), D-α-tocopheryl polyethylene glycol (1000) succinate (TPGS), sucrose laurate, Cremophor EL (CR EL), and Cremophor RH 40 (Cr RH 40) were incubated with human liver microsomes at different concentrations to determine the IC50 of the reduced metabolism of the model substrates. Inhibitory potential in case of all tested compounds could be observed already below their critical micelle concentrations (CMC) and in concentration-dependant manner. The IC50 of the CYP 3A4-mediated 6β-hydroxylation of testosterone has been determined as 0.40 mM (PS 80), 0.15 mM (TPGS), 0.20 mM (sucrose laurate), 0.60 mM (Cr EL), and 0.80 mM (Cr RH 40). The IC50 concerning the CYP 2C9-mediated 4-hydroxylation of diclofenac has been calculated to be 0.04 mM (PS 80), 0.30 mM (TPGS), 0.07 mM (sucrose laurate), 0.03 mM (Cr EL), and 0.03 mM (Cr RH 40). The results indicate that these non-ionic surfactants are in vitro inhibitors of CYP-mediated metabolism and might have the potential to modify the pharmacokinetics of co-administered drugs, which are substrates of CYP, and thereby enhance their bioavailability.
Keywords: Non-ionic surfactants; Excipients; Inhibition effect; Cytochrome P450; Intestinal metabolism; Bioavailability;

Workflow of Principal Component Scores Distance Analysis (PC-SDA).A novel and straightforward multivariate analytical tool for the qualitative determination of powder blend uniformity using on-line Near-Infrared Spectroscopy (NIRS) is presented. The approach combines current chemometric methods, e.g. spectral pre-processing and Principal Component Analysis (PCA), with (1) a new approach of data analysis to determine the end-point of the blending process, (2) building a design space (DS) for blend homogeneity and (3) developing a solid statistical rationale to stop blending according to Quality-by-Design (QbD) principles of FDA’s Process Analytical Technology (PAT) initiative. The new approach comprises calculation of Euclidean distances between PCA scores in a multidimensional space and determination of Moving Block Standard Deviations (MBSDs) of successive Principal Component (PC) scores distances to estimate a time-window during blending where spectral variability decreases to a preset minimum. Hotelling’s T 2 statistics is then used to monitor and report blend homogeneity. This technique is called “Principal Component Scores Distance Analysis” (PC-SDA).A Central Composite Design resulting in 10 batches mixed in a bin-blender (same composition, different blender fill level, different number of revolutions) was executed.NIR Chemical Imaging (NIR-CI) in combination with Symmetry Parameter Image Analysis (SPIA) was used to verify the NIRS analyzer response and assess homogeneity of all NIR-active components.
Keywords: PAT; on-line NIRS; NIR-CI; Blending; Design space; QbD;