Preparation and release property of norfloxacin sustained-release microspheres

doi:10.12307/2023.509

Abstract

Abstract: BACKGROUND: Norfloxacin is widely used in clinical practice. When it is used as the sustained-release microspheres, it can play a role in a long time, largely improve the bioavailability and elevate the compliance of patient’s medication, and also can decrease the adverse reaction, discomfort and medication dosage during the treatment period. It has important research significance and application value.
OBJECTIVE: To prepare norfloxacin-loaded microspheres and investigate and analyze its preparation conditions, release properties and structure with chitosan, nano-SiO2 and sodium alginate as the raw materials.
METHODS: Norfloxacin microspheres were prepared by extrusion-exogenous gel method. The effects of norfloxacin concentration, m(SiO2):m(norfloxacin) and crosslinking time on the encapsulation rate of norfloxacin microspheres were investigated by single factor experiment. The optimal preparation conditions were determined and two types of norfloxacin sustained release microspheres, calcium alginate/chitosan and SiO2-calcium alginate/chitosan, were prepared under the optimal preparation conditions. The microspheres were characterized and released in vitro.
RESULTS AND CONCLUSION: (1) The single factor experiment results showed that the encapsulation rate of microspheres was better when the concentration of norfloxacin was 1.5 g/L, the concentration of m(SiO2):m(norfloxacin) was 4:10, and the crosslinking time was 20 minutes. (2) Through the characterization of the microspheres by Fourier Transform Infrared Spectroscopy, scanning electron microscopy, X-ray diffraction and thermogravimetric analysis, it can be concluded that the microspheres prepared under the above conditions tended to be amorphous materials, with uniform appearance size and regular shape, and SiO2 had good compatibility with calcium alginate and chitosan, forming a new complex. The addition of SiO2 had no effect on the morphology of the microspheres. The thermal stability of SiO2 microspheres was better. (3) The sustained release performance of the prepared microspheres showed that the microspheres had a certain sustained release effect, no sudden release phenomenon occurred during the release, and the addition of SiO2 microspheres had better salt resistance.

Key words: sustained-release microsphere, norfloxacin, chitosan, sodium alginate, nano SiO2, encapsulation rate, release performance, extrudation-exogenous gel method

CLC Number:

Yuan Jialu, Liu Mei, Qin Xiaolong, Qiu Yang, Li Jing. Preparation and release property of norfloxacin sustained-release microspheres[J]. Chinese Journal of Tissue Engineering Research, 2023, 27(30): 4790-4795.

Figures/Tables 3

2.1 微球制备的单因素实验结果图1A为诺氟沙星质量浓度对诺氟沙星缓释微球包封率的影响，可以看出，随着诺氟沙星质量浓度的增大，诺氟沙星缓释微球包封率先逐渐增大、再略有降低，说明适当增大诺氟沙星的质量浓度对提高微球的包封率有一定的促进作用。当诺氟沙星质量浓度为1.5 g/L时，诺氟沙星缓释微球包封率最高。图1B为m(SiO2)∶m(诺氟沙星)对诺氟沙星缓释微球包封率的影响，可以看出SiO2加量对包封率影响较大，随着SiO2加量的增加，诺氟沙星缓释微球的包封率先逐渐增大后减小，其原因可能是SiO2加量太小，无法对溶液中的诺氟沙星形成有效的负载；而加量太多，诺氟沙星缓释微球的包封率降低，这可能是由于溶液中SiO2表面电荷与诺氟沙星的表面电荷相互排斥，不利于对诺氟沙星的包覆。当m(SiO2)∶m(诺氟沙星)为4∶10时，诺氟沙星缓释微球的包封率最高，在后续实验中选择m(SiO2)∶m(诺氟沙星)为4∶10制备的缓释微球。图1C为交联时间对Si-CA/CTS微球包封率的影响，可以看出，随着交联时间的增大，微球的包封率先增大后减小，这可能是交联时间太短，不利于微球的形成和对药剂的包覆，但交联时间太长，微球表面药物的扩散损失将会增大，微球的包封率减小。继续增大交联时间，微球的包封率基本不变，这可能是在较长的交联时间内，微球表面已经被固化成膜，药物难以从内部扩散出来，导致包封率不再降低。因此，选择20 min作为最佳交联时间。在上述最佳制备条件下，平行3次制备出CA/CTS及Si-CA/CTS两种缓释微球，其包封率与载药量如图1D所示，可以看出，Si-CA/CTS较CA/CTS表现出较高的包封率与载药量。这是由于SiO2的强吸附性使得诺氟沙星被吸附于其表面或孔道内，在交联过程中不容易被溶出，从而提高了微球的包封率和载药量。Si-CA/CTS微球的最优包封率为35.6%。"

2.2 微球表征图2A为CA/CTS及Si-CA/CTS两种缓释微球干燥前的实物图，可以看出，所制备的缓释微球外貌尺寸均一、形状规整，微球表面具有一层透明的薄膜，这是海藻酸盐与壳聚糖通过静电作用形成的聚电解质复合物。图2B为两种缓释微球的扫描电镜照片，可以看出，两种缓释微球呈均质实心不规则球体，其直径为50-300 μm。由于钙离子浓度与凝胶时间对微球的凝胶厚度有一定影响，而先后滴入到钙离子溶液中的含诺氟沙星海藻酸盐液滴享有不同的平均钙离子浓度与交联时间，使其凝胶厚度与强度具有一定的差异，致使其在烘干后产品的微观形貌不够均匀。从图2B还可以看出，微球表面粗糙，其切面边缘上可观察到层状结构，可能是由海藻酸钙与壳聚糖之间的静电络合作用使高分子链之间相互缠绕而形成的微观结构。二者的样品在形貌上差别不大，说明SiO2的加入并未改变壳聚糖-海藻酸钙形成的微观形貌，SiO2与壳聚糖和海藻酸钙具有较好的相容性。图2C为CA/CTS和Si-CA/CTS两种缓释微球的傅里叶红外光谱图，可以看出，两种样品的红外峰形大致相同，其中3 430 cm–1左右的宽吸收峰为样品中羟基和氨基的伸缩振动峰混合而成，670 cm–1处为羟基的面外弯曲振动吸收，1 613，1 424 cm–1处为样品中海藻酸钠引入的羧基的反对称与对称伸缩振动峰。在CA/CTS中，1 087，1 033 cm–1处主要为样品中C-O-C伸缩振动引起的吸收峰。与CA/CTS相比，Si-CA/CTS在3 430，670 cm–1处的吸收峰变强、变宽，且吸收峰发生了明显红移，这是样品中引入了含有丰富表面羟基的SiO2引起的，该结果也说明SiO2的表面羟基与CA/CTS中的羟基及氨基发生了明显的缔合效应，这有利于提升微球的吸附性能。其次，Si-CA/CTS在1 087，1 033 cm–1处的吸收峰因SiO2的引入显著增强，这主要是由Si-O-Si的反对称伸缩振动峰与此处的吸收峰重叠引起的。同时，Si-CA/CTS还在943 cm–1和474 cm–1处出现了Si-O-Si的对称伸缩振动和弯曲振动峰[26]，进一步证实了该样品中SiO2的存在。此外，与CA/CTS相比，Si-CA/CTS在1 341，1 306 cm–1处还呈现出2个新的吸收峰，可归属于-CO-NH-与Si-OH-C的吸收[27-28]，说明在孵化过程中，部分海藻酸盐中的羧基与壳聚糖上的氨基依靠氢键作用形成了新的化学单元，而部分SiO2也通过-OH与海藻酸钙发生了桥连，由此可以说明SiO2与CA/CTS之间通过化学键结合并形成了新的复合物。图2D为CA/CTS和Si-CA/CTS的X射线衍射谱图，可以看出，CA/CTS与Si-CA/CTS更倾于非晶性物质，2个样品中，在41°附近的衍射峰是海藻酸盐与壳聚糖强烈的相互作用以及与钙离子交联形成的结晶结构，在12.65°与26.65°附近的衍射峰属于诺氟沙星的特征衍射峰，该处的衍射峰与纯诺氟沙星相比(13.24°、25.02°)位置发生了一定程度的改变[29]，说明诺氟沙星并不是简单的被吸附在微球材料上。与CA/CTS相比，Si-CA/CTS的X射线衍射图谱中在20.90°处的衍射峰属于SiO2的特征峰，再次证明SiO2与CA/CTS复合成功，和纯SiO2相比(22°)[30]，该处的衍射峰向低角度发生了偏移，说明SiO2与CA/CTS的复合破坏了SiO2的结晶结构。在CA/CTS样品中，11.60°处的衍射峰可归属于壳聚糖的特征衍射峰，它是由壳聚糖分子上的NH3+和羟基之间形成的分子内氢键，使其分子链的运动受到限制引起的，加入SiO2以后，该处的衍射峰明显减弱，说明SiO2与壳聚糖因氢键或静电作用而发生缔合，其相容性较好。和CA/CTS相比，Si-CA/CTS样品中在27.88°处出现了一个新的衍射峰，结合红外分析结果可知，这是由于SiO2与CA/CTS复合后，部分SiO2表面羟基与海藻酸钙作用使其原有的结构发生畸变所致。图2E为Si-CA/CTS的热重-微商热重曲线，可以看出，Si-CA/CTS的总失重率约为77%，其热稳定性较好，在室温至180 ℃区间内，失重率约为10%，这主要是微球表面及孔道内的吸附水和结构水受热而损失所导致的；在180-350 ℃范围内，失重率约为32%，说明在该温度区间缓释微球中的有机物开始分解，在该过程中其最大分解速率所对应的温度为260 ℃；当温度大于350 ℃时，失重率约为35%，是因为有机物上的骨架碳开始分解导致的，其最大分解速率所对应的温度为514 ℃和700 ℃。"

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