周建红,令玉林,司士辉
(1.湖南科技大学生命科学学院,湖南湘潭411201;2.湖南科技大学化学化工学院,湖南湘潭411201;3.中南大学化学化工学院,湖南长沙 410083)
丝网印刷电极在食品检测中的应用研究进展
周建红1,令玉林2,司士辉3
(1.湖南科技大学生命科学学院,湖南湘潭411201;2.湖南科技大学化学化工学院,湖南湘潭411201;3.中南大学化学化工学院,湖南长沙 410083)
丝网印刷电极因价格便宜、使用方便、重现性好、检测灵敏度高而成为研究热点。对丝网印刷电极在食品检测中的应用进行了综述,主要阐述丝网印刷电极在亚硝酸盐、硫化物、毒枝菌素、致病菌、海产食品毒性等污染物的检测和乳酸的检测、电子鼻和电子舌的应用与发展趋势。对于同一种成分,则按工作电极的修饰方法或检测方法来进行分述,并对丝网印刷电极的应用前景进行了展望。
丝网印刷电极,综述,传感器,食品检测
电分析化学方法具有灵敏度高、选择性好、可野外操作和价格便宜的优势,有些电分析技术能够在线、活体内检测各种性能的物质,其中一种就是采用丝网印刷电极(Screen-printed electrode,SPE)的电化学分析。SPE又称厚膜电极,是用厚膜集成电路工艺制备的电化学传感器。丝网印刷技术主要优点包括:设计灵活,印制过程容易实现自动化,重现性好,适用于各种材质,成本低廉。由于可大批量生产重现性好的传感器且成本低,可以一次性使用,对使用者十分方便。这种在用户手上不需要标定的一次性产品成功地解决了电极重现性差等问题。这项技术为现场检测提供了很大的发展前景[1]。SPE的多功能性表现在可采用不同方法来修饰电极。印刷的各种油墨的比例可通过添加不同的物质例如金属、酶、聚合物、复合剂等来改变[2-5];另一方面,可在已生产出的电极表面上采用不同电沉积方式来修饰电极[6-7]。本文主要对近年来的各种SPE在食品中的应用进行了综述概括。根据被检测的成分来进行分类,阐述了丝网印刷电极在食品方面的应用与发展,并对其以后的发展趋势进行了展望。
最早的丝网印刷传感器主要集中在血糖的测定方面,之后逐渐拓展到诸如生物分子、杀虫剂、离子及污染物的测定。以下就近年来丝网印刷电极在食品中有关成分的检测做一阐述。
1.1 亚硝酸盐(Nitrite)和硫化物的检测
亚硝酸盐的检测结果对地下水及饮用水质量的评价非常重要。Neuhold[8]等将Aliquat 336a阴离子交换剂加入碳油墨中来印刷电极,克服了以往采用固态交换剂操作费时且不严密的弊端。Chang[9]等报道,发展一种便宜的聚二甲基硅氧烷(PDMS)基电化学电池,设计了一种一次性超微SPE,采用FIA系统来检测亚硝酸盐。Lin[10]等采用聚3,4-乙撑二氧噻吩/铁酞菁/多壁碳钠米管(PEDOT/FePc/MWCNT)来修饰丝网印刷电极,减小了亚硝酸盐氧化的过电位,使检测限达到了71nM,灵敏度达到638mA·cm-2·M-1。
对于硫外物的测定,有采用聚(L-交酯)固定金钠米粒子修饰SPCE,利用As3+减少氧化电流能间接测定硫化物,其检测限为0.04μM[11]。徐肖邢[12]等在一次性印刷碳电极(SPCE)的基础上,研究了N,N-二甲基对苯二胺(DMPD)在印刷电极上的电化学行为及其对硫离子的电催化氧化,采用DPV测定了S2-。
1.2 致癌物质——毒枝菌素的检测
很多食品中的毒枝菌素含量超标。牛奶通常被少量的黄曲霉毒素M1(AFM1)即奶牛对黄曲霉毒素B1(AFB1)的代谢产物所污染。Micheli[13]等描述了一种在SPCEs表面上直接固定抗体制得的电化学免疫传感器,在其表面游离的AFM1与连接有HRP的AFM1发生竞争抗体;另一种建立在间接竞争的ELISA基础上的一种一次性电化学免疫传感器,采用DPV和SPCEs来简单快速地测定AFB1[14]。表面吸附有抗AFB1抗体的SPCEs,基于游离分析物与连接有AFB1生物素之间竞争抗体的原理而被应用于竞争性免疫分析中[15]。随后添加结合有ALP的生物素,1-萘基磷酸盐底物能产生一种电化学活性产物1-萘酚,采用线性扫描伏安法(LSV)得以测定。Piermarini[16]等首次采用一个微盘多通道的电化学检测器,采用间歇脉冲电流(IPA)技术来检测AFB1。Alarcon[17]等描述了一种直接竞争性的ELISA来测定另一种毒枝菌素——赭曲霉素A(OTA,ochratoxin),他们采用了多克隆抗体的SPCEs,适合于普查食品中的OTA。Romanazzo[18]等将磁性珠子作为载体,SPEs作为敏感元件,利用便携式掌式传感器来检测毒枝菌素,在数秒钟内能自动完成八次测定。Hervas[19]等采用碳SPEs作为电化学免疫传感器来检测婴儿食品中的玉米烯酮,检测限低至0.007μgL-1。
1.3 致病菌的检测
李斯特产单核细胞细菌污染的食品会引起严重的传染病。Crowley[20]等描述了一种测定牛奶中该菌的免疫传感器,采用直接三明治式的对两种亲合多克隆的山羊、兔和一种单克隆的老鼠抗L.产单核细胞抗体进行了比较分析,应用生物素-抗生物素蛋白的SPCEs进行检测来克服敏感性低的弊端。Rao[21]等描述了一次性的电流式免疫传感器快速测定霍乱弧菌(V.cholerae)。另有研究采用锥虫成虫期表面的醣蛋白制成的电流式免疫传感器来诊断查格斯氏病[22]。Farabullini[23]等采用电化学基因传感器阵列来同时快速检测污染食品中的不同病原菌。Elizabeth Tully[24]等用聚苯胺(PANI)丝网印刷电极,将生物素-抗生物素蛋白固定在(PANI)表面,随后多克隆抗-内化素B(InlB)抗体,采用电化学阻抗光谱(EIS)来实现无标检测。Fernandez-Baldo[25]等采用碳钠米管修饰丝网印刷免疫传感器测定苹果中的灰葡萄孢菌。利用竞争性的免疫方法达到0.02μg·mL-1,而一般的ELISA的检测限为10μg·mL-1。SPE用于致病菌的检测发展很迅速,也是目前研究的热点。Lin[26]等利用商业的银和碳墨制成的SPE,采用双层抗体的制成安培免疫条带,利用间接的三明治式的酶联免疫分析快速检测Escherichia coliO157∶H7。Escamilla-Gómez[27]等采用自组装单层修饰金SPE,然后固定抗体制成无标的电化学阻抗免疫传感器。采用的硫基化抗体使得分析性能明显改善,在不用富集和预处理的情况下能选择性地检测Escherichia coli,检测限达到了3.3cfu· mL-1。Salam和Tothill IE[28]采用集三电极系统于一体的SPE来实现Salmonella typhimurium的检测。Mata[29]等采用集成的SPE微系统电化学检测致病菌。对于浓度为102cfu·mL-1和108cfu·mL-1的致病菌在样品量只需10μL,不到30min内得以快速检测。为推行手提式病原菌控制装置奠定了基础。
1.4 海产食品毒性的检测
大部分的海产品中毒是因为摄取了海产品中低分子量的毒性物质[30]。Kreuzer[31]等通过检测标有ALP而产生的p-氨基酚,尝试制作了一种免疫传感器来快速地、准确地评定痕量海产品毒性物质。在软骨藻酸(DA)存在的情况下[32],DA与BSA共轭覆盖在SPCE工作电极上,接着样品(或标准的毒物)和抗-DA抗体共同培养,用一种抗山羊IgG-碱性磷酸酯酶(AP)来产生信号,利用DPV方法来进行测定。
1.5 乳酸的检测
Shkotova[33]等采用在丝网印刷铂电极上固定乳酸氧化酶来测量发酵过程中酒中乳酸的含量。Prieto-Simon[34]等采用萘酚蓝和辅因子NAD(+)固定在SPE’s上测定,灵敏度较差为260μA·M-1,而用介体-聚砜-石墨复合膜后的SPE’s灵敏度明显改善,达到80mA·M-1,检测限达到0.87μM。接着有Piano[35]等采用萘酚蓝和雷氏盐,并用乳酸脱氢酶和辅因子NAD(+)采用流动注射方法来检测乳酸。该传感器的线性范围为0.55~10mM。
1.6 制得味觉和嗅觉传感器来检测食品
目前广泛运用生物模拟味觉传感系统:类脂/高聚物膜对接触味觉物质产生的电势差的原理制成多通道味觉传感器。而瑞典Linkpoing大学Fredrik Winquist课题小组使用的惰性贵金属传感器阵列,使用六种惰性贵金属(金、铱、钯、铂、铼、铑),中心为Ag/AgCl参比电极,外周为不锈钢对电极组成传感器阵列构成电子舌来检测不同品牌的饮料,对其施加脉冲电压,结果显示使用脉冲电压的电子舌也能够区分不同类型的饮料[29,36]。因为在所施的电位下,溶液中的所有具有电化学活性的物质对仪器所测得的响应电流均有贡献,需通过计量学方法来解析,对溶液中的金属及其他导电性能良好的离子进行表达。俄罗斯圣彼得堡大学Hakhyun设计的丝网印刷电位传感器[37],它是一种全固态平面式电位电子舌系统,将掺有PVC、PPY、聚氨酯等不同物质的高交叉灵敏度聚合物薄膜覆盖在由普鲁士兰修饰的碳糊丝网印刷传感器阵列电极表面,该系统可用于检测饮用水、软饮料和啤酒的味道。Busch[38]等采用SPEs碳电极和酪氨酸酶以及过氧化物酶作为生物传感器,来检测轻榨优质橄榄油中的酚类化合物,以此确定苦味和辛辣味。Gine Bordonaba[39]等采用葡萄糖生物传感器快速估计草莓质量。利用萘酚蓝作为介体,葡萄糖氧化酶固定在SPEs上,根据葡萄糖含量区分八种不同品种的草莓。
近年来,根据大量的参考资料报道,丝网印刷传感器适应于执行快速准确地现场分析和紧凑轻便的装置的需要。本文综述了丝网印刷电极在食品检测中的应用,这项技术的主要改进体现在如下方面:引入新的印刷材料和新的支撑表面来提高丝网印刷传感器的重现性和灵敏性;采用新的修饰工作电极方法,主要集中于新的配位体、聚合物和纳米结构材料;采用不同的固定方法来固定酶;采用多阵列电极以及化学计量学手段进行多种产物的同时识别和检测。
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Recent development of application of screen-printed electrodes in food determination
ZHOU Jian-hong1,LING Yu-lin2,SI Shi-hui3(1.College of Life Science,Hunan University of Science and Technology,Xiangtan 411201,China;
2.School of Chemistry and Chemical Engineering of Hunan University of Science and Technology,Xiangtan 411201,China;
3.College of Chemistry and Chemical Engineering,Central South University,Changsha 410083,China)
This review presents various applications and the developments of screen-printed electrodes(SPEs)in food determination in recent years.They were categorized according to the types of analytes,including nitrite,sulfide,mycotoxins,pathogenic bacteria and seafood toxins.Lactic acid determination and electronic nose or tongue was also summarized.For the same analyze,they were categorized according to the materials that modified the working electrode and the determination methods.At the same time,the main trends of screen-printed electrode were predicted.
screen-printed electrodes;review;sensors;food determination
TS201.1
A
1002-0306(2012)01-0388-04
2010-12-06
周建红(1973-),女,博士研究生,讲师,研究方向:电分析化学。
湖南大学化学化工学院,国家化学生物传感和计量学重点实验室开放项目(200907);国家科技重大专项湘江水环境重金属水质目标管理与监测技术研究子课题(2009ZX07212-001-06)。