@article{Larsson2017,

title = {Effects of HPMC substituent pattern on water up-take, polymer and drug release: an experimental and modelling study},

author = {Diego Caccavo and Gaetano Lamberti and Anna Angela Barba and Susanna Abrahms\'{e}n-Alami and Anna Virid\'{e}n and Anette Larsson},

url = {http://www.sciencedirect.com/science/article/pii/S0378517317305720},

doi = {10.1016/j.ijpharm.2017.06.064},

issn = {0378-5173},

year  = {2017},

date = {2017-08-07},

journal = {International Journal of Pharmaceutics},

volume = {528},

number = {1-2},

pages = {705-713},

abstract = {The purpose of this study was to investigate the hydration behavior of two matrix formulations containing the cellulose derivative hydroxypropyl methylcellulose (HPMC). The two HPMC batches investigated had different substitution pattern along the backbone; the first one is referred to as heterogeneous and the second as homogenous. The release of both the drug molecule theophylline and the polymer was determined. Additionally, the water concentrations at different positions in the swollen gel layers were determined by Magnetic Resonance Imaging. The experimental data was compared to predicted values obtained by the extension of a mechanistic Fickian based model. The hydration of tablets containing the more homogenous HPMC batch showed a gradual water concentration gradient in the gel layer and could be well predicted. The hydration process for the more heterogeneous batch showed a very abrupt step change in the water concentration in the gel layer and could not be well predicted. Based on the comparison between the experimental and predicted data this study suggests, for the first time, that formulations with HPMC of different heterogeneities form gels in different ways. The homogeneous HPMC batch exhibits a water sorption behavior ascribable to a Fick´s law for the diffusion process whereas the more heterogeneous HPMC batches does not. This conclusion is important in the future development of simulation models and in the understanding of drug release mechanism from hydrophilic matrices. },

keywords = {Erosion, HPMC, Hydrogel Characterization, Hydrogel Modeling, Mathematical modeling},

pubstate = {published},

tppubtype = {article}

}

@article{Barba2009f,

title = {Swelling of cellulose derivative (HPMC) matrix systems for drug delivery},

author = { Anna Angela Barba and Matteo D'Amore and Serafina Chirico and Gaetano Lamberti and Giuseppe Titomanlio},

url = {http://www.sciencedirect.com/science/article/pii/S0144861709002707},

doi = {10.1016/j.carbpol.2009.05.001},

issn = {01448617},

year  = {2009},

date = {2009-10-01},

journal = {Carbohydrate Polymers},

volume = {78},

number = {3},

pages = {469--474},

abstract = {The water swellable hydrogels are commonly used in the production of solid pharmaceutical dosage systems for oral administration (matrices). Their use allows to obtain the controlled drug release. The key role is played by the transport phenomena which take place: water up-take, gel swelling and erosion, increase in diffusivity due to hydration. Thus, knowledge of these phenomena is fundamental in designing and realizing the pharmaceutical systems. In this work, tablets made of pure hydrogel, HydroxyPropyl-MethylCellulose (HPMC), were produced and immersed in a thermostatic bath filled with stirred distilled water (37°C). The water up-take was allowed only by radial direction (from the lateral surface) by confining the tablet between two glass slides. Two distinct methods, an optical technique already described in a previous work, and a gravimetric procedure described here, were applied to measure the water concentration profiles along the radial direction in the tablets. The data obtained were used both to clarify the nature of the transport phenomena involved, and to perform a better tuning of a mathematical model previously proposed.},

keywords = {Erosion, Extended release, HPMC, Hydrogel Characterization, Swelling, Water diffusion},

pubstate = {published},

tppubtype = {article}

}

@article{Chirico2007,

title = {Analysis and modeling of swelling and erosion behavior for pure HPMC tablet},

author = { Serafina Chirico and Annalisa Dalmoro and Gaetano Lamberti and Giuseppina Russo and Giuseppe Titomanlio},

url = {http://www.sciencedirect.com/science/article/pii/S0168365907003215},

doi = {10.1016/j.jconrel.2007.07.001},

issn = {01683659},

year  = {2007},

date = {2007-09-01},

journal = {Journal of Controlled Release},

volume = {122},

number = {2},

pages = {181--188},

abstract = {This work is focused on the transport phenomena which take place during immersion in water of pure hydroxypropylmethylcellulose tablets. The water uptake, the swelling and the erosion during immersion were investigated in drug-free systems, as a preliminary task before to undertake the study of drug-loaded ones. The tablets, obtained by powder compression, were confined between glass slabs to allow water uptake only by lateral surface and then immersed in distilled water at 37 °C, with simultaneous video-recording. By image analysis the normalized light intensity profiles were obtained and taken as a measure of the water mass fraction. The time evolutions of the total tablet mass, of the water mass and of the erosion radius were measured, too. Thus a novel method to measure polymer and water masses during hydration was pointed out. Then, a model consisting in the transient mass balance, accounting for water diffusion, diffusivity change due to hydration, swelling and erosion, was found able to reproduce all experimental data. Even if the model was already used in literature, the novelty of our approach is to compare model predictions with a complete set of experimental data, confirming that the main phenomena were correctly identified and described.},

keywords = {Controlled drug release, Erosion, HPMC, Hydrogel Characterization, Hydrogel Modeling, Swelling},

pubstate = {published},

tppubtype = {article}

}