Monitoring microsphere coating processes using PAT tools in a bench scale fluid bed.

Among the factors that influence adherence to medication within the pediatric population, taste/irritation has been identified as a critical barrier to patient compliance. With the goal of improving compliance, microspheres (matrix systems within which the drug is dispersed) can be coated with a reverse enteric polymer that will prevent the release of the drug in the oral cavity while maintaining an immediate release once the drug product reaches the stomach, thereby achieving a taste neutral profile. In this work, the in-line performance of three process analytical technology (PAT) tools is evaluated in order to monitor the microsphere coating process. These tools are Raman spectroscopy, near-infrared spectroscopy and focused beam reflectance measurements, together with process data and raw material attributes. The ability of these different sources of information to predict the coating's barrier performance is evaluated by using a combined-data-approach: multiblock partial least squares (MBPLS). Results show that Raman spectroscopy has a superior predictive performance and that it has the potential to monitor the coating process of the microspheres as well as to detect process discrepancies (such as spray rate changes), demonstrating its usefulness for the monitoring of fluid bed coating processes. It was also demonstrated that Raman can be used to clearly differentiate batches with significantly difference in-vitro dissolution performance. This monitoring is considered critical to ensure consistent coating performance for this thin film barrier membrane that is essential to patient compliance.

Building Process Understanding of Fluid Bed Taste Mask Coating of Microspheres.

Taste is routinely cited as one of the major contributing factors that negatively influence pediatric patient compliance. A promising solution is coated microsphere systems, which provide doses of active pharmaceutical ingredients (API) subdivided into a plurality of small dosage units. In this work, the microspheres were coated with Kollicoat® Smartseal, a reverse enteric polymer, which acts to minimize or prevent the release of API in the neutral pH of the oral cavity, which results in a masking effect of the unpleasant taste of the API. A screening of seven key variables in a Wurster coating process was evaluated by D-optimal design and by analysis of variance. The percentage of API released at pH 6.2 was used as a surrogate method for the taste-masking performance evaluation of Kollicoat® Smartseal. The seven studied variables were: product bed temperature, inlet airflow, atomizing air pressure, spray rate (process parameters), coating level, plasticizer level, solids in coating suspension (material attributes), and curing. Results show that coating level, plasticizer level, product bed temperature, and spray rate are the critical process parameters and reinforce the importance of curing to reduce the overall variability within the batch by promoting complete film formation. The link between material attributes, process parameters, and quality attributes were demonstrated to allow a better understanding of the parameters that affect the API release profile at neutral pH (in vitro) while not injuring release at acidic pH (in vitro). It was demonstrated that not only thickness but also coating morphology have an impact on the dissolution in 50 mM potassium phosphate buffer, pH 6.2.

In-line monitoring of Ibuprofen during and after tablet compression using near-infrared spectroscopy.

Near infrared spectroscopy (NIRS) used as process analytical technology tool to monitor Active Pharmaceutical Ingredient concentrations during tablet manufacturing has been reported to enhance overall product quality assurance. NIRS applications in different manufacturing stages are facilitated by their ability to handle different sample presentations - be it solids, liquids, gels or powders. The present study evaluates NIRS suitability for monitoring Ibuprofen concentrations (coated pellets form) inside the feed frame of a tableting press as well as in output tablets. Process monitoring was undertaken with quantitative chemometric analysis. NIRS-based predictions of concentrations both inside the feed frame and in tablets were compared to ultraviolet (UV) spectroscopy assays of temporally stratified tablet samples. Process dynamics were also compared in terms of concurrent concentrations change kinetics in the feed frame and in output tablets. NIRS showed good sensitivity to Ibuprofen concentrations despite the use of coated pellets. Ibuprofen contents as low as 1.7% w/w were detected effectively. NIRS-based quantitative predictions in the feed frame and in tablets closely matched the UV assay values of sampled tablets. As anticipated from the 2-wheel feed frame geometry, upon the addition of each consecutive blend, results show that the predicted concentration inside the feed frame were delayed compared with that of the tablets exiting the tablet press. For these tests, the delay was estimated to be 1.25 min. This finding highlights the importance of NIRS probe position inside the feed frame as a function of its geometry. Successive feed frame and tablet monitoring by NIRS could prove beneficial for real time release testing of tablet formulations.

Squeezing and detachment of living cells.

The interaction of living cells with their environment is linked to their adhesive and elastic properties. Even if the mechanics of simple lipid membranes is fairly well understood, the analysis of single cell experiments remains challenging in part because of the mechanosensory response of cells to their environment. To study the mechanical properties of living cells we have developed a tool that borrows from micropipette aspiration techniques, atomic force microscopy, and the classical Johnson-Kendall-Roberts test. We show results from a study of the adhesion properties of living cells, as well as the elastic response and relaxation. We present models that are applied throughout the different stages of an experiment, which indicate that the contribution of the different components of the cell are active at various stages of compression, retraction, and detachment. Finally, we present a model that attempts to elucidate the surprising logarithmic relaxation observed when the cell is subjected to a given deformation.

Aspiration of biological viscoelastic drops.

Spherical cellular aggregates are in vitro systems to study the physical and biophysical properties of tissues. We present a novel approach to characterize the mechanical properties of cellular aggregates using a micropipette aspiration technique. We observe an aspiration in two distinct regimes: a fast elastic deformation followed by a viscous flow. We develop a model based on this viscoelastic behavior to deduce the surface tension, viscosity, and elastic modulus. A major result is the increase of the surface tension with the applied force, interpreted as an effect of cellular mechanosensing.