Abstract：
The monitoring of foodborne bacterial contamination requires simple and convenient biosensors. This work describes a novel paper-based colorimetric biosensor for the rapid and sensitive bacteria detection. The biosensor was constructed via the encapsulation of D-alanyl-D-alanine capped gold nanoparticles (DADA-AuNPs) in a modified paper that was fabricated by the freeze-drying of TEMPO-oxidized cellulose nanofibers/cationic guar gum composite hydrogel-modified filter paper. The results indicated that the size of DADA-AuNPs largely determined the color of their aqueous system and they exhibited light red to dark red as their size increased from around 6 to 36 nm. All these different sized DADA-AuNPs turned into colorless when encountered with either S. aureus or E. coli. In particular, the smaller the DADA-AuNPs size, the faster the discoloration. The encapsulation of DADA-AuNPs into modified paper negligibly changed their responsiveness towards bacteria. In comparison to the original filter paper and oven-dried hydrogel-modified filter paper, the freeze-dried hydrogel-modified paper was demonstrated to be a better substrate for the encapsulation of DADA-AuNPs since they could be loaded with a larger amount of DADA-AuNPs in a faster way and showed a better perceivable color. This work demonstrated a promising paper-based colorimetric biosensor for the facile and rapid detection of bacteria.
摘要：
食源性细菌污染的监测需要简单方便的生物传感器。这项工作描述了一种新型的纸质比色生物传感器，用于快速和灵敏的细菌检测。生物传感器是通过将D-丙氨酰-D-丙氨酸覆盖的金纳米颗粒（DADA-AuNP）封装在改性纸中而构建的，该改性纸是通过冷冻干燥TEMPO氧化的纤维素纳米纤维/阳离子瓜尔胶复合水凝胶改性的滤纸制成的。结果表明,DADA-AuNP的尺寸在很大程度上决定了它们的水性体系的颜色,并且当它们的尺寸从大约6增加到36nm时,它们表现出浅红色到暗红色。当遇到金黄色葡萄球菌或大肠杆菌时,所有这些不同大小的DADA-AuNP变成无色。特别是,DADA-AuNPs的大小越小，变色越快。将DADA-AuNP封装到改性纸中可忽略地改变其对细菌的反应性。与原始滤纸和烘箱干燥的水凝胶改性滤纸相比，冷冻干燥的水凝胶改性纸被证明是封装DADA-AuNP的更好的底物，因为它们可以以更快的方式加载更大量的DADA-AuNP，并显示出更好的可感知颜色。这项工作证明了一种有前途的纸质比色生物传感器，可用于轻松快速地检测细菌。
