Examinando por Autor "Simon L"

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    The dynamics of shrinking and expanding drug-loaded microspheres: A semi-empirical approach
    (ELSEVIER SCIENCE BV, 2014-07-16) Simon L; Ospina J; Willits RK; Simon L; Ospina J; Willits RK; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
    The dynamics of shrinking and expanding drug-loaded microspheres were studied using a diffusion equation in spherical coordinates. A movable boundary condition was incorporated as a convection term in the original model. The resulting convective-diffusive problem was solved using Laplace transform techniques with the Bromwich integral and the residue theorem. Analytical solutions were derived for the general case of shrinking or expanding microspheres and three particular kinetics expressions: linear growth, exponential swelling and exponential shrinking. Simulations show that microspheres with fast-swelling kinetics released their therapeutic cargo at a relatively slow rate in the first two cases. Ninety-nine percent of the medication was delivered at four times the effective time constant. In line with laboratory studies using bovine serum albumin, an increase in the shrinking rate led to a fast release of the medication from its carrier. The method was applied to analyze insulin transport through spherical Ca-alginate beads. A good agreement was noted between predicted and experimental data. The theoretical effective time constant was 114.0 min.
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    Three-dimensional analyses of a perforated cylindrical drug delivery device
    (ELSEVIER SCIENCE BV, 2015-03-15) Simon L; Ospina J; Simon L; Ospina J; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
    A closed-formed solution of a perforated drug-delivery model was developed. Laplace transforms were applied to the governing equation, which included diffusion through the tubular device and mass transfer across a rectangular cut. A first-order estimate for the fraction of drug released, in terms of the Laplace variable, was derived after employing suitable boundary and initial conditions. The effective time constant for the process was calculated. The residue theorem and the Zakian method were proposed as two reliable approaches to recover the solution in the time domain. Simulations show that the drug was released faster at higher Sherwood numbers. Ninety-eight percent (98%) of the loading dose was delivered after a period corresponding to four time constants. This analytical platform can aid in the design of implants for long-term delivery applications. (C) 2015 Elsevier B.V. All rights reserved.