Hu Xiuting, Liu Yao, Chen Yimei, Zhang Tao, Miao Ming
State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
Foods. 2021 Nov 1;10(11):2653. doi: 10.3390/foods10112653.
The pH-responsive hydrogels were obtained through successive carboxymethylation and phosphorylase elongatation of phytoglycogen and their structure and functional characterizations were investigated. Phytoglycogen (PG) was first carboxymethylated to obtain carboxymethyl phytoglycogen (CM-PG) with degree of substitution (DS) at 0.15, 0.25, 0.30, and 0.40, respectively. Iodine staining and X-ray diffraction analysis suggested that the linear glucan chains were successfully phosphorylase-elongated from the non-reducing ends at the CM-PG surface and assembled into the double helical segments, leading to formation of the hydrogel. The DS of CM-PG significantly influenced elongation of glucan chains. Specifically, fewer glucan chains were elongated for CM-PG with higher DS and the final glucan chains were shorter, resulting in lower gelation rate of chain-elongated CM-PG and lower firmness of the corresponding hydrogels. Scanning electron microscope observed that the hydrogels exhibited a porous and interconnected morphology. The swelling ratio and volume of hydrogels was low at pH 3-5 and then became larger at pH 6-8 due to electrostatic repulsion resulting from deprotonated carboxymethyl groups. Particularly, the hydrogel prepared from chain-elongated CM-PG (DS = 0.25) showed the highest sensitivity to pH. These results suggested that phosphorylase-treated CM-PG formed the pH-responsive hydrogel and that the elongation degree and the properties of hydrogels depended on the carboxymethylation degree. Thus, it was inferred that these hydrogels was a potential carrier system of bioactive substances for their targeted releasing in small intestine.
通过对植物糖原进行连续的羧甲基化和磷酸化酶延伸反应获得了pH响应性水凝胶，并对其结构和功能特性进行了研究。首先将植物糖原（PG）进行羧甲基化，分别得到取代度（DS）为0.15、0.25、0.30和0.40的羧甲基植物糖原（CM-PG）。碘染色和X射线衍射分析表明，线性葡聚糖链在CM-PG表面从非还原端成功地进行了磷酸化酶延伸，并组装成双螺旋片段，从而形成水凝胶。CM-PG的取代度显著影响葡聚糖链的延伸。具体而言，取代度较高的CM-PG延伸的葡聚糖链较少，最终的葡聚糖链较短，导致链延伸的CM-PG的凝胶化速率较低，相应水凝胶的硬度也较低。扫描电子显微镜观察到水凝胶呈现出多孔且相互连接的形态。在pH 3-5时，水凝胶的溶胀率和体积较低，而在pH 6-8时，由于羧甲基去质子化产生的静电排斥作用，溶胀率和体积变大。特别地，由链延伸的CM-PG（DS = 0.25）制备的水凝胶对pH表现出最高的敏感性。这些结果表明，磷酸化酶处理的CM-PG形成了pH响应性水凝胶，并且水凝胶的延伸程度和性质取决于羧甲基化程度。因此，推测这些水凝胶是生物活性物质在小肠中靶向释放的潜在载体系统。
