Kinetics and the Theoretical Aspects of Drug Release from PLA/HAp Thin Films Innocent J. Macha 1,a* , Besim Ben-Nissan 2,b and Wolfgang Müller 3,c 1 Department of Mechanical and Industrial Engineering, University of Dar es Salaam, P.O Box 35131, Dar es Salaam, Tanzania 2 School of Life Sciences, University of Technology Sydney, P.O. Box 123, Broadway, NSW 2007, Australia 3 Technische Universität Berlin, Fak. V, Institut für Mechanik, Lehrstuhl für Kontinuumsmechanik und Materialtheorie – LKM, Sekr. MS 2 Einsteinufer 5, D-10587 Berlin a imacha@udsm.ac.tz, b besim.ben-nissan@uts.edu.au, c whmueller1000@gmail.com Keywords: kinetics, drug dissolution, thin films, coral-derived hydroxyapatite, antibiotic, drug delivery. Abstract. The theory of dissolution kinetics of gentamicin from polylactic acid-hydroxyapatite thin film composites is spotlighted with the combination of diffusion and polymer degradation modeling. The use of various mathematical models, characterizing diffusion, dissolution or/and erosion prevalence as well as a mix of dissolution-diffusion rate processes were employed in order to compare theory with experimental data. A number of factors influence the release kinetics of gentamicin from medical drug release systems and devices. It is difficult to have a single mathematical model that takes all these factors into account. It is shown that the degradation of the polymer matrix plays the biggest role in the release kinetics of polymer-ceramics thin film composites. It was also observed that multistage drug release form these devices depends also on the degradation kinetics of the polymer matrix. The effect of pH and device sizes were not studied but could also be of interest in future studies. Introduction Slow drug release has been an important research subject in the field of drug delivery for decades. Drug release systems provide an outstanding alternative to conventional clinical therapies. The use of biodegradable materials such as polymer and calcium phosphates in designing drug release devices provides the outstanding capability of performing localized and controlled delivery of drugs to different parts of the host body. In order to allow for greater potency and less toxicity to healthy tissue, therapeutic agent release systems are required to control the release. Generally speaking in slow drug delivery devices, the mechanisms leading to drug release are linked to diffusion, dissolution and erosion of the matrix. However, additional interactions with the carrier can also modify the release kinetics. Furthermore, the physicochemical and morphological properties, the positioning of the drug within the porous network, its accessibility and its solubility are key parameters that govern the release kinetics and therefore the efficiency and efficacy of the treatment. There has been an enormous effort directed to the development of biodegradable materials that are capable of releasing drugs by reproducible and predictable kinetics [1, 2] to meet these demands. Ceramics and other materials, such as polymers and biocomposites, have been proposed in the past, but it is difficult to shape them appropriately with adequate micro porosity in order to be fitted into any type and size of bone defect. Recently it has been demonstrated by Ben-Nissan and co- workers that marine shells with specific microspherical design offer desired functions for the delivery of Bisphosphonate (paminodrate) and antibiotic (Gentamicin) [3]. This has been possible by virtue of its unique structure and architecture of the foraminifera shells, which are extraordinarily difficult to manufacture with the current know-how [4]. Key Engineering Materials Submitted: 2017-06-07 ISSN: 1662-9795, Vol. 758, pp 113-119 Revised: 2017-07-16 doi:10.4028/www.scientific.net/KEM.758.113 Accepted: 2017-09-07 © 2017 Trans Tech Publications Ltd, Switzerland Online: 2017-11-15 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (#537965585, TU Berlin, Berlin, Germany-24/03/20,07:46:25)