Drug release mechanisms of chemically cross-linked albumin microparticles: Effect of the matrix erosion

Abstract

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A c c e p t e d M a n u s c r i p t Page 4 of 25 A c c e p t e d M a n u s c r i p tsphericity. In such a case, BSA played a role as a surface active agent, replacing PVA. For longer stirring times, BSA was unable to act as an emulsifier.These microparticles showed an uncommon release profile, consisting of a two-step release mechanism, at the pH range studied. Considering that a two-step release mechanism is occurring, the experimental data were adjusted by applying modified power law and Weibull equations in order to describe release mechanism n and release rate constant k, respectively. Each one of the release stages was related to a specific value of n and k. The second stage was driven by a super case II transport mechanism, as a result of diffusion, macromolecular relaxation, and erosion. A third model, described by Hixson-Crowell, confirmed the erosion mechanism.Vit-B 12 diffusion kinetics in aqueous solutions (i.e., without the microparticles) follows a one-step process, being k dependent on the pH, confirming that the two-step release mechanism is a characteristic profile of the developed microparticles. The microparticles released only 2.70% of their initial drug load at pH 2, and 58.53% at pH 10.

Preparation of Spray-Dried Soy Isoflavone-Loaded Gelatin Microspheres for Enhancement of Dissolution: Formulation, Characterization and in Vitro Evaluation

“…This suggests that the release was not controlled by drug diffusion [ 27 ], but mainly by disintegration of the microspheres. The Hixson–Crowell cube root law [ 49 ] describes the release from the systems, where it depends on the change in surface area and diameter of the particles with time; it mainly applies to systems that dissolve or erode over time [ 50 ] In this case, the GEN release rate is limited by the microparticle erosion rate.…”

Encapsulated Microparticles of (1→6)-β-d-Glucan Containing Extract of Baccharis dracunculifolia: Production and Characterization

“…The diffusional exponent (n) values vary according to the system geometry of the particles, with values of n = 0.43 for a sphere, n = 0.45 for a cylinder, and n = 0.5 for a thin film with Fickian diffusion [55,56]. Diffusional exponent (n) values of 0.89 indicate a Case II transport, and values greater than 0.89 characterize Super Case II transport [57], which is controlled by diffusion, polymer chain relaxation, and erosion [58]. In this model, the “K” constant is considered the release velocity and reflects the geometrical structural characteristics of the system [59].…”

Comparative statistical analysis of the release kinetics models for nanoprecipitated drug delivery systems based on poly(lactic-co-glycolic acid)

“…In order to relate the Weibull model to the predominant transport mechanism in drug release, relationships between the Weibull parameter “β” and the Korsmeyer-Peppas parameter “ n” have been proposed [ 140 ]. Following this theory, Fickian diffusion would be demonstrated when β≤0.75, anomalous transport (diffusion and swelling) when β is between 0.75 and 1, case II type transport when β = 1 and case II type transport which is the combination of phenomena such as diffusion, erosion and macromolecular ratio of polymer chains for the case of cylindrical tablets with β>1 [ 141 , 142 ]. Doing this analysis with "n" and "β" obtained in this study ( S6 File ) we obtain a value of “β” to check Fickian diffusion of 0.75, while the transport type case II is explained by β = 1.45.…”