农产品中脱氧雪腐镰刀菌烯醇的表面增强拉曼检测

Surface-enhanced Raman detection of deoxynivalenol allenol in agricultural products

利用便携式拉曼光谱仪建立了一个快速筛查与检测谷物中真菌毒素脱氧雪腐镰刀菌烯醇(DON)的表面增强拉曼散射(SERS)方法。首先利用实验室前期开发的方法制备了具有高活性的水凝胶SERS芯片。该SERS芯片是将预先制备的高SERS活性的单层碳基点(CDs)包裹的银纳米颗粒团聚体(a-AgNPs/CDs)与聚乙烯醇(PVA)水溶液混合均匀后,再利用循环冷冻-解冻的物理交联法制备而成的。实验优化了影响水凝胶SERS芯片对DON的SERS响应的实验条件,包括溶剂、浸泡温度和浸泡时间。在最佳的SERS检测条件下(溶剂为水-乙醇(1∶1, v/v),浸泡温度为40℃,浸泡时间为5 min), DON的线性响应范围为1~10 000μg/kg(相关系数(R~2)=0.996 7),检出限(LOD)为0.14μg/kg,表明该SERS基底具有较高的灵敏度。得益于水凝胶特殊的孔径结构,实际样品基质中常见的糖、蛋白质、油脂、色素等干扰物质都被阻隔在水凝胶外。因此,在复杂样品检测中仅需要简单的提取,而不需要复杂的分离处理。将该方法用于小麦粉中DON的检测,所得回收率为97.3%~103%,相对标准偏差为4.2%~5.0%。实验结果表明所建立的检测DON的SERS方法具有响应范围宽、灵敏度高、重复性好、响应迅速、操作简单、抗干扰能力强等优点,这说明本实验室所构建的水凝胶SERS芯片在粮食中生物毒素的快速筛查与检测方面具有良好的应用潜力。

Fungal toxins are secondary metabolites of fungi. Food is highly susceptible to contamination by various fungal species that produce fungal toxins during production and storage. Fungal toxins can cause either acute or chronic poisoning from long-term, low-dose ingestion. Therefore, fungal toxins have become a topic of international interest as a food safety issue. Deoxynivalenol(DON) is a single-terminal sporam toxin produced predominantly by Fusarium graminae and Fusarium pinkosa. DON is globally one of the most common fungal toxins contaminating grain, food, and feed. Various methods have been applied for screening and detecting DON;however, these methods utilize expensive instruments and entail complex operations, poor repeatability, and low sensitivity. Therefore, the development of a simpler, more rapid, and sensitive sensing technology for DON detection is important for applications within the agriculture and food industry. Recently, surface-enhanced Raman scattering(SERS) has become a rapidly developing spectral analysis technology with unique advantages, including high sensitivity, high throughput, and rapid response rates. Therefore, attempts have been made to apply the SERS technique to detecting DON. However, due to the limitations concerning SERS substrates, the currently established SERS method exhibits serious problems, including low sensitivity and weak anti-interference ability, and cannot meet the requirements of sample detection. Recently, our group has prepared aggregated silver nanoparticles(a-AgNPs/CDs) with high SERS activity by using single-layer carbon-based dots(CDs) as a capping agent. Moreover, the obtained materials(a-AgNPs/CDs) were combined with hydrogel technology to prepare novel hydrogel SERS chips. The obtained SERS chips exhibited several advantages over traditional SERS substrates, such as high sensitivity, long-term stability, improved uniformity, and strong anti-interference capabilities. Herein, a novel SERS method for rapid screening and detection of DON in grains was established using a portable Raman spectrometer based on the developed hydrogel SERS chips. The main experimental conditions were optimized before the SERS detection of DON;this included the optimization of the hydrogel SERS chip soaking temperature and time in the DON solution. It was found that the optimal soaking temperature and time were 40 ℃ and 5 min, respectively. Under the optimal SERS detection conditions, the linear response range of DON was 1-10 000 μg/kg(correlation coefficient(R~2)=0.996 7), and the limit of detection(LOD) was 0.14 μg/kg. Due to the unique pore size structure of the hydrogel, common sugar, protein, oil, pigment, and other interfering substances in the sample matrix were blocked outside the hydrogel. Therefore, only simple extraction was required while detecting complex samples. This method was applied to detecting DON in wheat flour, yielding recoveries of 97.3%-103% with relative standard deviations of 4.2%-5.0%. The established SERS method for DON detection exhibits a broader response range, high sensitivity, good repeatability, rapid response, simple operation, and strong anti-interference capability. This shows that the laboratory-constructed hydrogel SERS chip has excellent potential for rapid screening and detection of biotoxins in food.