串联磁致伸缩生物传感器的制备和食品中大肠杆菌的检测

Preparation of series-connected magnetostrictive biosensors and detection of Escherichia coli in food

磁致伸缩生物传感器的制造成本、检测灵敏度、检测效率是影响传感器广泛应用的重要因素。为研究串联磁致伸缩生物传感器对食品中大肠杆菌的检测性能,该研究研制了一种新型串联磁致伸缩生物传感器,该传感器的换能器采用铁基非晶软磁合金,功能涂层采用环保亲水材料聚乙烯醇。将不同尺寸的单一传感器作为对照组,利用阻抗分析仪检测传感器的谐振参数。选取尺寸为4.8 mm×0.8 mm与7.2 mm×1.2 mm的传感器进行串联,将无抗体加载的传感器作为参考传感器,检测浓度为10~10^(8)CFU/mL大肠杆菌悬浮液。利用扫描电子显微镜观察传感器表面吸附致病菌情况。探索串联磁致伸缩传感器检测大肠杆菌食品溶液时谐振频率漂移量与浸泡时间的关系。研究发现:该串联磁致伸缩生物传感器相较于单一传感器具有更好的响应强度。通过对不同浓度大肠杆菌悬浮液的检测,得到该串联抗体传感器与大肠杆菌发生特异性结合,检测限为10^(2)CFU/mL。利用扫描电子显微镜观察传感器表面,证实谐振频率偏移量均由吸附大肠杆菌引起。利用阻抗分析仪检测串联传感器在大肠杆菌食品溶液中浸泡不同时间后的谐振频率漂移量,得到传感器实现稳定检测时间为20 min。表明此新型串联磁致伸缩生物传感器具有较高的灵敏度、稳定性、检测效率且制造简单,成本较低,使用方便。该研究可为生物传感器在食品安全检测方面的广泛应用提供有力参考。

Magnetostrictive biosensors can often consist of magnetostrictive transducers,functional coatings,signal excitation,bioprobes,and detection systems.These sensors can be used to generate and transmit the signals via magnetic field coupling.Among them,the magnetostrictive material can be subjected to the excitation of alternating magnetic fields during detection.Once the frequency of the magnetic field matches the natural frequency of sensors,the resonance can occur for an impedance signal.A direct current(DC)bias magnetic field can also be applied to amplify the signal.At the same time,the adsorption of pathogens can increase the mass of the sensor,leading to the variation in the resonance frequency.Some key factors(such as manufacturing costs,detection sensitivity,and efficiency)can significantly influence the performance of magnetostrictive biosensors.In this study,a series-connected magnetostrictive biosensor was developed to integrate two sensors with different sizes.A Fe-based amorphous soft magnetic alloy was selected with 25μm thick as the transducer.The functional coating with a 350 nm thick was prepared as the polyvinyl alcohol(PVA)film from a 2.5%PVA solution.Single sensors were used with the dimensions of 3.6×0.6,4.8×0.8,6.0×1.0,7.2×1.2,and 8.4 mm×1.4 mm as the control groups.Series connections were made as follows:3.6×0.6 with 6.0×1.0,4.8×0.8 with 7.2×1.2,and 6.0×1.0 with 8.4 mm×1.4 mm.An impedance analyzer was applied with a 50 mV alternating current(AC)excitation and a 6V DC bias voltage.A comparative analysis was conducted on the resonance parameters of single-and series-connected sensors.The series-connected sensors were selected with the dimensions of 4.8 mm×0.8 and 7.2×1.2 mm to detect Escherichia coli(E.coli)suspensions with concentrations ranging from 10 to 108 CFU/mL with/without antibodies.The adsorption of pathogenic bacteria was analyzed on some shifts in resonance frequencies.Scanning electron microscopy(SEM)was used to observe the surface adsorption of pathogenic bacteria on sensors.A systematic investigation was made to explore the relationship between the resonance frequency shifts and immersion times when the E.coli was detected in the food solutions using series-connected magnetostrictive sensors.The results revealed that there was a close relationship between the resonance parameters and the size of single-and series-connected sensors.The resonance frequency decreased,as the sensor size increased,whereas,the resonance amplitude increased.The magnitude of the resonance amplitude was quantitatively analyzed using the resonance frequency.Additionally,the series-connected magnetostrictive biosensors demonstrated that there was nearly unchanged in the resonance frequencies,but there was an increase in the resonance amplitudes,compared with the single sensors.Therefore,an enhanced strength response was achieved as well.The frequency shift of resonance increased with the higher concentrations of E.coli suspensions.Antibody-loaded sensors exhibited significantly larger resonance frequency shifts than those without antibodies,due to the specific binding between antibodies and E.coli.The detection limit of the series-connected sensor was determined to be 102 CFU/mL.There were relatively close frequency shifts of resonance in the 4.8 mm×0.8 mm and the 7.2 mm×1.2 mm sensors in the same loading conditions,due to the higher number of bacteria that adsorbed by the larger sensor(7.2 mm×1.2 mm).The small difference in mass between the two sensors resulted in similar frequency shifts.SEM observations confirmed that the frequency shifts of resonance were caused by the adsorption of E.coli.The sensor demonstrated excellent detection.The sensor with the antibody loading adsorbed significantly more E.coli on the surface,compared with the sensor without antibodies.This finding was consistent with the measurements on the frequency shift of resonance.The sensor achieved stable detection within 20 minutes.The novel series-connected magnetostrictive biosensor can offer high sensitivity,strong signal strength,high detection efficiency,simple manufacturing,low cost,and ease of use.This finding can provide a strong reference to apply biosensors to safety detections in the food industry.