Cazalbou Sophie, Bertrand Ghislaine, Drouet Christophe
CIRIMAT Carnot Institute, UMR CNRS/INPT/UPS 5085, Faculté des Sciences Pharmaceutiques, University of Toulouse , 35 Chemin des Maraîchers, 31400 Toulouse, France.
J Phys Chem B. 2015 Feb 19;119(7):3014-24. doi: 10.1021/jp5116756. Epub 2015 Jan 29.
Biomimetic apatites are appealing compounds for the elaboration of bioactive bone-repair scaffolds due to their intrinsic similarity to bone mineral. Bone surgeries are however often heavy procedures, and the infiltration of pathogens may not be totally avoided. To prevent their development, systemic antibiotic prophylaxis is widespread but does not specifically target surgical sites and involves doses not always optimized. A relevant alternative is a preliminary functionalization by an infection-fighting agent. In this work, we investigated from a physicochemical viewpoint the association of a wide-spectrum antibiotic, tetracycline (TC), and a biomimetic nanocrystalline apatite previously characterized. TC adsorption kinetics and isotherm were thoroughly explored. Kinetic data were fitted to various models (pseudo-first-order, pseudo-second-order, general kinetic model of order n, Elovich, double-exponential, and purely diffusive models). The best fit was found for a double-exponential kinetic model or with a decimal reaction order of 1.4, highlighting a complex process with such TC molecules which do not expose high-affinity end groups for the surface of apatite. The adsorption isotherm was perfectly fitted to the Sips (Langmuir-Freundlich) model, while other models failed to describe it, and the Sips exponent greater than unity (1.08) suggested a joint impact of surface heterogeneity and positive cooperativity between adsorbed molecules. Finally, preliminary insights on TC release from pelletized nanocrystalline apatite, in aqueous medium and neutral pH, were obtained using a recirculation cell, indicating a release profile mainly following a Higuchi-like diffusion-limited rate. This work is intended to shed more light on the interaction between polar molecules not exhibiting high-affinity end groups and biomimetic apatites and is a starting point in view of the elaboration of biomimetic apatite-based bone scaffolds functionalized with polar organic drugs for a local delivery.
由于其与骨矿物质的内在相似性，仿生磷灰石是制备生物活性骨修复支架的有吸引力的化合物。然而，骨手术通常是大型手术，病原体的侵入可能无法完全避免。为了防止病原体的生长，全身抗生素预防措施很普遍，但不能特异性地靶向手术部位，且所涉及的剂量并不总是优化的。一种相关的替代方法是用抗感染剂进行初步功能化。在这项工作中，我们从物理化学的角度研究了广谱抗生素四环素（TC）与先前表征的仿生纳米晶磷灰石的结合。对TC的吸附动力学和等温线进行了深入研究。动力学数据被拟合到各种模型（伪一级、伪二级、n级通用动力学模型、埃洛维奇模型、双指数模型和纯扩散模型）。发现双指数动力学模型或十进制反应级数为1.4时拟合效果最佳，这突出了TC分子与磷灰石表面不存在高亲和力端基的复杂过程。吸附等温线与Sips（Langmuir-Freundlich）模型完美拟合，而其他模型无法描述，且Sips指数大于1（1.08），表明表面非均质性和吸附分子之间的正协同作用的联合影响。最后，使用循环池获得了在水介质和中性pH条件下，纳米晶磷灰石颗粒中TC释放的初步见解，表明释放曲线主要遵循类似Higuchi的扩散限制速率。这项工作旨在更深入地了解不具有高亲和力端基的极性分子与仿生磷灰石之间的相互作用，并且是制备用极性有机药物功能化的基于仿生磷灰石的骨支架以实现局部递送的起点。
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