結合靜電紡絲聚丙烯腈奈米碳纖維與噬菌體的電化學阻抗式生物感測器

Abstract

本篇研究嘗試開發一種電化學生物感測器(Electrochemical-based biosensor)，用於快速且準確檢測食品中常見的大腸桿菌(Escherichia coli, E. coli)。此生物感測器以網版印刷碳電極(Screen-printed electrode, SPE)為基礎，利用滴附沉積法(Drop-casting)結合靜電紡絲聚丙烯腈(Polyacrylonitrile, PAN)經過高溫鍛燒所產生的奈米碳纖維(PAN-derived electrospun carbon nanofibers, CNF)以及大腸桿菌噬菌體(E. coli bacteriophage)。能量射散X射線光譜(Energy-dispersive X-ray spectroscopy, EDS)、X光繞射分析(X-ray diffraction, XRD)以及掃描式電子顯微鏡(Scanning electron microscopy, SEM)用於分析靜電紡絲纖維以及網版印刷碳電極的化學特徵與結構。循環伏安法(Cyclic voltammetry, CV)和電化學阻抗圖譜(Electrochemical impedance spectroscopy, EIS)則用於研究各階段的電子轉移速率與電荷轉移電阻(Charge transfer resistance, Rct)。此外為了提升阻抗數值計算之準確性，在套用等效電路(Equivalent circuit)時嘗試調整傳統蘭德斯電路(Randles circuit)之半無限擴散元件(Semi-infinite Warburg impedance, W)為有限擴散元件(Finite Warburg impedance, O)。 SEM的結果顯示高溫鍛燒能夠有效地降低CNF的平均直徑，EDS與XRD也分別驗證了CNF中碳元素的比例以及石墨烯晶體結構的存在。除此之外，CV的波峰電流以及EIS的電荷轉移電阻數值改變也指出CNF與噬菌體的成功修飾。定量結果顯示此生物感測器可以在10分鐘內有效檢測102 -106 CFU/mL的大腸桿菌，同時具有很低的偵測極限(Limit of detection, LOD) 36 CFU/mL。方法確效的部分，也針對生物感測器和檢測溶液的穩定性、真實樣品(蘋果汁)中的選擇性與其相關的應用進行探討。此研究所設計的生物感測器可以在室溫下保存至少一個月，同時對於目標宿主細菌具有良好的選擇性。在使用真實樣品(蘋果汁)檢測的部分，可接受的回收率也驗證了此生物感測器的準確性。

This study aims to introduce a facile method for fabricating a novel electrochemical-based biosensor for the detection of Escherichia coli. The bare screen-printed electrode (SPE) was modified by a two-step drop-casting method, in which the polyacrylonitrile (PAN) derived electrospun carbon nanofibers (CNF) were deposited followed by E. coli bacteriophage immobilization. The deposition of PAN-derived electrospun CNF significantly increased the rate of electron transfer and the surface area of the bare SPE. Energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed the hexagonal graphite structure of the CNF and the presence of bacteriophage on CNF. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to study the rate of electron transfer and the value of charge transfer resistance (Rct) for bare SPE, CNF/SPE, phage/CNF/SPE, and E. coli/phage/CNF/SPE. Besides, a new circuit (R(C(RO)) instead of (R(C(RW)) was fitted to the Nyquist plot of the EIS data to obtain better fitting accuracy. According to the SEM images of nanofiber, the average diameter of CNF significantly decreases after the thermal treatment. Besides, EDS and XRD confirm the proportion of carbon atoms and crystallographic structure of CNF, respectively. In addition, the change in peak current of CV and the value of Rct also ensure the success of CNF and bacteriophages modification. Moreover, the developed biosensor exhibited a low LOD of 36 CFU/mL in PBS buffer within 10 min, which also showed great stability for 1 month and high selectivity to the host bacteria. In the least, acceptable recoveries also confirmed the accuracy of the biosensor in real sample (apple juice).