米糠纳米纤维素的制备表征及其细胞毒性

研究以提取的米糠纤维素（纤维素含量90.22%）为原料，采用不同体积分数硫酸水解（60%、64%和68%）制备获得米糠纳米纤维素（Rice Bran Nanocellulose，RBNC），对其表面形貌、尺寸、电位、化学结构、热稳定性及晶体结构进行了表征，并进一步评价了其细胞毒性。透射电镜和原子力显微镜结果显示，制备得到的RBNC是长度在196.45 ~ 257.26 nm、直径为8.46 ~ 16.34 nm、长径比为17.06 ~ 24.34范围内的针状粒子；Zeta电位值在-32.9 ~ -35.2 mV范围内；红外光谱和X-射线衍射分析表明得到的RBNC化学结构未发生变化，仍保留纤维素Ⅰ型晶体结构。体积分数为64%的硫酸水解得到的RBNC长径比最优（24.34±3.63）、结晶度最高（81.32%）、Zeta电位绝对值最大（-35.2±0.85 mV）。进一步的细胞毒性评价表明，RBNC分别在≤ 2000 μg/mL和≤ 500 μg/mL浓度范围内，对Caco-2和HepG-2细胞无显著毒性，表现出良好的生物相容性。研究结果可为RBNC做为一种新型纳米材料在食品领域的应用提供理论基础，为米糠的高值化利用提供新途径。

Preparation and Characterization of Rice Bran Nanocellulose and Cytotoxicity Evaluation

The study was carried out to obtain rice bran nanocellulose (RBNC) from rice bran cellulose (cellulose content: 90.22%) using sulfuric acid hydrolysis with different volume fractions (60%, 64% and 68%). The morphology, potential, size, structure, physicochemical properties and cytotoxicity of RBNC were investigated in the further study. The results of transmission electron microscopy (TEM) and atomic force microscopy (AFM) confirmed that the obtained RBNC were needle-like shape with lengths ranging from 196.45 to 257.26 nm, diameters from 8.46 to 16.34 nm, and aspect ratios from 17.06 to 24.34. Zeta potential values of NC suspensions ranged from -32.9 to -35.2 mV. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis showed that the chemical structure of the obtained RBNC still retained the cellulose type I crystal structure. Moreover, the RBNC obtained by hydrolysis with 64% volume fraction of sulfuric acid had the best aspect ratio (24.34±3.63), the highest crystallinity (81.32%), and the highest absolute zeta potential (-35.2±0.85 mV). In addition, cytotoxicity evaluation showed that RBNC did not decreased cell viability significantly to Caco-2 cells in the concentration range of ≤ 2000 μg/mL, and to HepG-2 cells in the concentration range of ≤ 500 μg/mL, indicating that RBNC has good biocompatibility. The research results can provide a theoretical basis for the application of RBNC as a new nanomaterial in the food industry, and provide a new way for the high-value utilization of rice bran.