以Schiff碱为酸敏开关的智能抗菌纳米包装膜的构建及控释机理研究

On-demand release could be achieved by the intelligent antimicrobial packaging system, which is the most ideal state and a development orientation of the food preservative packaging industry. In this project, a new type of intelligent nanoscale packaging membrane for on-demand release is designed according to the characteristic of acid-cleavable Schiff base linkages. This kind of membrane focuses on the food surface most prone to corruption metamorphic reactions, by following the rule that “microbial contamination of food occurs primarily at the surface and the value of pH will gradually reduce”. Firstly, the nanoparticles with aldehyde are synthesized by RAFT polymerization and self-assembly, and immobilized antibacterial agent as a carrier through Schiff base coupling. Then the resulting antibacterial-conjugated polymeric nanoparticles are dispersed in the compatible membrane material. Finally, the intelligent antimicrobial packaging film are obtained by means of tape casting. Furtherly, the release dynamics and antibacterial effect, as well as physical and mechanical properties of the film will be investigated to analyze the interaction among various factors for quantisation parameters. Moreover, the mathematical models, dynamic simulation and experimental tests are also conducted to clarify the mechanism of intelligent controlled release. The study can realize simultaneous packaging of "activity" and "intelligent", and will provide reference for technology innovation of the food preservative packaging industry in China.

仅使包装膜具备抗菌活性及实现抗菌剂缓慢释放，不能达到抑菌的理想效果，智能抗菌包装技术可实现抗菌剂按需释放，是未来食品防腐包装工业的发展方向。本项目基于“食品腐败从表面开始并伴随pH值相应逐渐降低”的规律，利用Schiff碱的酸敏特性，着眼于最易发生腐败变质反应的食品表面，设计了一种能够感知和响应食品介质pH值信号，实现抗菌剂动态调节释放的新型纳米包装膜。采用RAFT“活性”/可控自由基聚合和自组装技术获得粒径可调的带醛基纳米微球，并以此为载体通过Schiff碱偶联高效固载抗菌剂，流延分散于相容性膜材料中，获得智能活性抗菌纳米包装膜。进一步研究膜的释放动力学特征、抗菌效果和物理机械性能并分析各因素相互作用，量化参数，构建控释数学模型，并通过对控释过程的动态仿真与实验验证，阐明智能控释机理。该项目拟实现食品包装膜的“活性”和“智能”双重化目标，将为我国食品抗菌包装行业技术升级提供新参考。

智能抗菌包装技术可实现抗菌剂按需释放，是目前所有活性包装中一项最具创新性及挑战性的技术，是未来食品防腐包装工业的热点发展方向。. 本项目设计并合成了以苯乙烯（St）为核单体，4-乙烯基苯甲醛（VBA）为壳单体，并以过硫酸铵（APS）为引发剂、壬基酚聚氧乙烯-4-醚硫酸铵(DNS458)为乳化剂、甲基丙烯酸烯丙酯（AMA）为交联剂，经预乳化、种子乳液聚合后，在85 oC下成功制备了具有核壳结构的含醛基纳米聚合物微球聚P(St-co-VBA)。透射电镜显示形貌为均匀圆球形、大小均一、粒径为50-60 nm。所得微球通过Schiff碱将抗菌剂乳酸链球菌（Nisin）偶联并纳米化导入聚乙烯醇（PVA）中，制得含醛基纳米微球-乳酸链球菌缀合物/聚乙烯醇复合膜。所得膜在PH=2和7时100 h抗菌剂释放量分别是53.0%和12.4%，表明该膜抗菌剂的释放是受PH值控制的，具有酸敏响应性，符合Fick第一扩散定律，温度和食品介质的变化也会影响其释放量。乳酸链球菌纳米缀合物的添加，赋予膜具有较强的抗菌性能，阻隔性能和物理机械性能。结果表明当添加250mg缀合物到聚PVA中时，膜的抑菌圈直径是10.0 mm；弹性模量是2060.42 MPa，与未添加比较增加了8.5倍；气体透过率从2.835 cc/m2d0.1Mpa降到1.825 cc/m2d 0.1Mpa；阻湿性能从2.84 g mm/m2 day Kpa降到2.59 g mm/m2 day Kpa。所得膜在25 oC应用于新鲜猪肉的保鲜，与空白对照组相比，可将货架期延长4-5天。. 本研究基于食品腐败特定规律，通过对抗菌剂释放调控、抗菌剂加工耐受性和抗菌剂与包装材料相容性等系列问题的设计和实证，实现食品包装的“活性”和“智能”的双重化目标。有利于有害微生物和治病微生物的控制，减少食品内部防腐剂的添加，增加安全；有利于农产品新鲜品质的保持，提高商品价值，为我国食品防腐包装工业的技术升级和未来农产品产销储运提供新思路，也为我国食品保鲜研究和食品安全提供新参考，具有十分重要的理论意义和实用价值。此外，抗菌包装技术和抗菌包装材料研究应用的不断发展，还将带动一些相关产业的发展壮大，如包装机械的研究生产，食品加工业的增产增效等。