硅壳包被的核壳型量子点荧光纳米颗粒的制备及其细菌计数的应用

以氧化镉和硬脂酸锌为前驱体,合成了CdSe/ZnS核壳型量子点(QDs).采用反相微乳液技术,在温和条件下实现了硅壳包被的CdSe/ZnS荧光纳米颗粒的成功制备.在戊二醛的交联作用下,以金黄色葡萄球菌(S.aureus)为目标细菌、荧光纳米颗粒为荧光探针,建立了一种高灵敏的、简单快速的细菌计数的方法,并借助荧光显微镜成功地进行成像探测研究.通过考察荧光纳米颗粒与细菌的孵育时间、包入硅壳的核壳量子点质量等多种因素的影响.在最优化条件下,本方法的线性范围为5×102～5×107 CFU/mL;检出限为500 CFU/mL;线性回归方程为Y=494.96749X- 1194.25738(R=0.9960).本方法操作简单,检测时间短,有效克服了传统平板计数方法和基于有机染料的荧光检测方法存在的缺陷,提高了灵敏度.将此法用于6种实际样品的细菌数量测定,检测结果与平板计数方法基本一致,相对标准偏差在3.1％～8.2％之间,结果令人满意.

Synthesis of Core/Shell Quantum Dots Doped Silica Nanoparticles and Their Application for Detecting Bacterial Count

CdSe/ZnS core/shell quantum dots(QDs) were synthesized with cadmium oxide and zinc stearate as precursors.A reverse-microemulsion technique was used to synthesize CdSe/ZnS quantum dots doped silica nanoparticles modified with amine and phosphonate groups under very mild conditions.A highly sensitive,simple and rapid counting approach for bacteria was established by using fluorescent nanoparticles as a fluorescence label,Staphylococcus aureus(S.aureus) acted as detection target bacteria and glutaraldehyde as the crosslinker.The bacterial cell images were obtained using fluorescence microscopy.The effect of parameters such as reaction time and the amount of CdSe/ZnS in SiO2-coated fluorescent nanoparticles was discussed.Under the optimized conditions,a linear relationship of the fluorescence peak intensity(Y) and the total bacterial count(X) was established in the range of 5×102-107 CFU/mL using the equation Y=494.96749X-1194.25738(R=0.9960).This method shows a bright application prospect for detection of the total bacterial count due to its several advantages such as rapid,technically simple and high sensitivity while compared with the conventional plate counting and organic dye-based method.Results of determination for the total count of bacteria in six real samples were identical with the conventional plate count method,and the relative standard deviation(3.1%-8.2%) were satisfactory.