Department of Chemistry, Faculty of Engineering, Istanbul University-Cerrahpasa, Avcilar, 34320 Istanbul, Turkey.
Department of Chemistry, Faculty of Engineering, Istanbul University-Cerrahpasa, Avcilar, 34320 Istanbul, Turkey; Turkish Academy of Sciences (TUBA), Piyade Sok., No. 27, Cankaya, 06550 Ankara, Turkey.
Talanta. 2019 May 1;196:32-38. doi: 10.1016/j.talanta.2018.12.022. Epub 2018 Dec 11.
A novel colorimetric nanosensor was developed for evaluating peroxyl radical scavenging activity of phenolic antioxidants and for the detection of hydroperoxides formed during AAPH-induced oxidation of linoleic acid emulsions. Starch was used as a green reduction/stabilization agent for gold nanoparticles (AuNPs) synthesis in alkaline medium. When tert-butyl hydroperoxide (tert-BHP) was incubated with an excess of iodide ions in a 37 °C water bath for 90 min, triodide (I) was formed in an amount equivalent to tert-BHP concentration. Upon the addition of starch-stabilized gold nanoparticles (ss-AuNPs) solution to the incubation mixture, triiodide ions were rapidly adsorbed on the surface of AuNPs and caused their aggregation. A concomitant red shift (from 525 nm to 563 nm) of surface plasmon resonance (SPR) absorption of the nanoparticles was observed, absorbance linearly increasing with aqueous tert-BHP concentration. The method provided an LOD of 39 µM for tert-BHP, and was validated through linearity, precision and accuracy. The concentration of hydroperoxides estimated in linoleic acid peroxidation correlated well with those found by the reference ferric thiocyanate assay. Peroxyl radical scavenger antioxidants decreased the red-shifted SPR absorption of aggregated ss-AuNPs, thereby enabling an indirect estimation of antioxidant activity. This AuNPs-based colorimetric sensor is the first of its kind to directly determine peroxyl radical scavenging activity of polyphenols. The half-maximal inhibitive concentrations (IC) of selected antioxidant compounds were calculated by utilizing the decrease in absorbance with increasing concentration of scavengers, and compared to those of classical oxygen radical absorbance capacity (ORAC) assay. The proposed nanosensor was superior over FL-based ORAC in determining the peroxyl radical scavenging activity of the lipophilic antioxidant α-tocopherol. The percentage scavenging of real samples such as green tea infusion and synthetic serum were determined. The proposed assay can be used for estimating the peroxyl scavenging of various food and biological samples in terms of its low cost, ease of use and compatibility.
一种新型的比色纳米传感器被开发出来，用于评估酚类抗氧化剂的过氧自由基清除活性，并用于检测 AAPH 诱导亚油酸乳液氧化过程中形成的过氧化物。在碱性介质中，使用淀粉作为绿色还原/稳定剂来合成金纳米粒子（AuNPs）。当叔丁基过氧化物（tert-BHP）在 37°C 水浴中与过量的碘离子孵育 90 分钟时，会形成与 tert-BHP 浓度相当的三碘化物（I）。当向孵育混合物中加入淀粉稳定的金纳米粒子（ss-AuNPs）溶液时，三碘化物离子迅速被吸附在 AuNPs 的表面并导致其聚集。纳米粒子的表面等离子体共振（SPR）吸收发生了伴随的红移（从 525nm 到 563nm），吸收值与水溶液中 tert-BHP 的浓度呈线性关系增加。该方法对 tert-BHP 的检出限为 39µM，并通过线性度、精密度和准确度进行了验证。在亚油酸过氧化反应中估计的过氧化物浓度与参考铁硫氰酸盐测定法发现的浓度非常吻合。过氧自由基清除抗氧化剂降低了聚集的 ss-AuNPs 的红移 SPR 吸收，从而能够间接估计抗氧化活性。这种基于 AuNPs 的比色传感器是直接测定多酚类过氧自由基清除活性的首例。通过利用随着清除剂浓度的增加而吸收值的降低，计算出所选抗氧化化合物的半最大抑制浓度（IC），并与经典的氧自由基吸收能力（ORAC）测定法进行比较。与基于 FL 的 ORAC 相比，该纳米传感器在测定疏水性抗氧化剂 α-生育酚的过氧自由基清除活性方面具有优势。测定了绿茶提取物和合成血清等实际样品的清除率。与成本高、使用复杂的基于 FL 的 ORAC 相比，该测定法具有成本低、使用方便和兼容性强等优点，可用于测定各种食品和生物样品的过氧自由基清除率。
