摘""""" 要: 隨著人類生活質(zhì)量的提高,膽固醇的檢測(cè)成為一個(gè)重要的研究課題。電化學(xué)方法具有選擇性強(qiáng)、檢測(cè)速度快等優(yōu)點(diǎn)。綜述了近年來(lái)利用電化學(xué)方法在有酶和無(wú)酶的條件下測(cè)定膽固醇含量的電化學(xué)原理和最新進(jìn)展,并對(duì)用電化學(xué)方法檢測(cè)膽固醇進(jìn)行了展望。
關(guān)" 鍵" 詞:膽固醇;有酶;無(wú)酶;電化學(xué)傳感器
中圖分類號(hào):O657.1"""" 文獻(xiàn)標(biāo)識(shí)碼: A"""" 文章編號(hào): 1004-0935(2023)08-1193-04
膽固醇是一種化學(xué)式為C27H46O的環(huán)戊烷多氫菲的衍生物。膽固醇是人體內(nèi)最普遍存在的化合物,主要存在于大腦的中樞神經(jīng)組織,另外還存在于腎臟、脾臟、皮膚以及膽汁。膽固醇能經(jīng)由多種途徑進(jìn)入身體。高膽固醇會(huì)引起慢性心臟病、高血壓、腦血栓等致命的心腦血管病[1-2]。目前,膽固醇的檢測(cè)方法有高效液相色譜法[3-4],比色法[5-6]和光譜法[7-8]等,這些檢測(cè)方法一般存在檢測(cè)周期長(zhǎng)、靈敏度低、選擇性、儀器標(biāo)準(zhǔn)化、樣品預(yù)處理要求高等缺點(diǎn)。另一方面,電化學(xué)方法[9-10]由于具有選擇性強(qiáng)、制備方法簡(jiǎn)單、儀器簡(jiǎn)單、成本低、操作方便、檢測(cè)速度快等特點(diǎn),受到研究者的廣泛關(guān)注[11]。電化學(xué)檢測(cè)膽固醇的方法包括包括差分脈沖伏安法(DPV)[12]、安培法[13-14,15-17]、電荷轉(zhuǎn)移(CT)[18]、循環(huán)伏安法(CV)[19-22]、線性掃描伏安法""""" (LSV)[23-24]、電化學(xué)發(fā)光法(ECL)[25]和電化學(xué)阻抗譜(EIS)[26]。在這些方法中,電流測(cè)量法是許多研究中最常用和最敏感的方法[27]。隨著技術(shù)的發(fā)展,基于各種材料制備出的膽固醇電化學(xué)傳感器成為研究熱點(diǎn)之一。
1" 電化學(xué)方法檢測(cè)膽固醇的原理
1.1" 基于膽固醇氧化酶電化學(xué)檢測(cè)膽固醇的原理
膽固醇氧化酶(ChOx)是一種含有黃素腺嘌呤二核苷酸(FAD)的葉黃素酶,在氧氣存在下催化膽固醇,生成膽固醇-4-烯-3-酮和H2O2[28]?;贑hOx電化學(xué)檢測(cè)膽固醇的原理主有3類,如圖1所示。
第一類:氧氣作為電子傳輸介質(zhì),用氧電極或H2O2電極測(cè)量氧消耗或氧化產(chǎn)物H2O2濃度來(lái)檢測(cè)膽固醇含量。
第二類:使用電子介體,如二茂鐵及其衍生" 物[29-30]、鐵氰化物[31]、染料分子[32-33]和苯酚[34]等,替代氧氣和H2O2在電極表面和ChOx活性中心之間(FAD)有效傳遞電子,通過(guò)檢測(cè)電子介體在電極表面氧化還原得失電子數(shù)檢測(cè)膽固醇的含量。
第三類:隨著各種新型電極材料的研制,基于電極與ChOx之間的直接電子轉(zhuǎn)移(DET)的電化學(xué)檢測(cè)膽固醇方法也隨之產(chǎn)生,膽固醇的含量可以通過(guò)酶在電極表面的直接氧化還原得失電子數(shù)來(lái)測(cè)定。
1.2" 無(wú)酶電化學(xué)檢測(cè)膽固醇的原理
為了克服酶在使用過(guò)程中受到儲(chǔ)存和分析條件的限制,近年發(fā)展了無(wú)酶電化學(xué)檢測(cè)膽固醇的方法。無(wú)酶電化學(xué)測(cè)定是通過(guò)直接在電極表面電化學(xué)催化膽固醇或通過(guò)氧化還原劑電子介質(zhì)來(lái)傳導(dǎo)膽固醇與電極表面電子進(jìn)行間接檢測(cè),如圖2所示。
2" 電化學(xué)檢測(cè)膽固醇研究進(jìn)展
2.1 "基于膽固醇氧化酶電化學(xué)檢測(cè)膽固醇的進(jìn)展
基于ChOx的膽固醇電化學(xué)檢測(cè)是通過(guò)固化附著在工作電極表層上的ChOx 特異性識(shí)別和催化膽固醇,利用天然化學(xué)物質(zhì)如氧氣為主要電子傳遞介質(zhì),來(lái)測(cè)定氧氣消耗及ChOx氧化產(chǎn)物含量的傳感器。其主要機(jī)理是ChOx催化游離膽固醇在O2存在下生成膽固醇-4-烯-3-酮和H2O2,然后用氧電極或H2O2電極測(cè)定膽固醇含量。夏天子[35]等利用一類新型的二維過(guò)渡金屬碳化物、氮化物(MXene)和殼聚糖(Chit)的有益特性設(shè)計(jì)成了膽固醇傳感器,如圖3所示。Chit和Ti3C2Tx作為支撐ChOx的底物,并在提高電導(dǎo)率方面發(fā)揮作用。修飾電極對(duì)H2O2電化學(xué)響應(yīng)與膽固醇濃度在0.3~4.5 nmol·L-1之間有良好的線性關(guān)系,它的檢測(cè)限為0.11 nmol·L-1,靈敏度為132.66 μA·(nmol·L-1)-1·cm-2。
薛中華[36]等研制出具有類似于過(guò)氧化物酶的特性MoS2@PBNCS,對(duì)3,3',5,5'-四甲基聯(lián)苯胺(TMB)與H2O2 反應(yīng)起到催化作用。在最佳實(shí)驗(yàn)條件下,膽固醇的濃度與TMB的還原電流在0.3~100 μmol·L-1成良好的線性關(guān)系,檢出限為12 nmol·L-1。SALAZAR等開(kāi)發(fā)了一種利用鎳氧化物(NiO)修飾電極的膽固醇電化學(xué)傳感器[37]。他們發(fā)現(xiàn),在中性環(huán)境下,NiO改性電極可以有效地探測(cè)H2O2,將NiO修飾電極與ChOx組裝成膽固醇電化學(xué)生物傳感器,靈敏度達(dá)到7.8 μA·(mmol·L-1)-1·cm-2,檢測(cè)線為""" 20 μmol·L-1??傮w上,這種檢測(cè)方法借助ChOx氧化產(chǎn)物濃度來(lái)測(cè)量膽固醇,使用這種方法會(huì)存在很多干擾物質(zhì),反應(yīng)時(shí)需要借助游離氧的催化作用,可能會(huì)造成實(shí)驗(yàn)結(jié)果不準(zhǔn)確。
基于電子介質(zhì)和ChOx的電化學(xué)檢測(cè)膽固醇是利用電子介質(zhì)作為電極和ChOx電活性中心之間的電子傳遞通道,透過(guò)測(cè)量小分子電子介質(zhì)的電化學(xué)信號(hào)的改變來(lái)測(cè)量膽固醇含量。HALDER等將二茂鐵作為電子介質(zhì),利用高支化多聚物基質(zhì)將ChOx和石墨烯納米片連接制修飾電極,對(duì)膽固醇的檢測(cè)限為0.5 μmol·L-1,線性響應(yīng)范圍為2.5~25μmol·L-1,靈敏度380 mA·(mol·L-1)-1·cm-2[37]。此方法可以使用的電子介質(zhì)有限,需要進(jìn)一步的探索。介質(zhì)仍然會(huì)與血液中的干擾物質(zhì)發(fā)生反應(yīng),影響準(zhǔn)確性和效率,同時(shí)很難在電極和酶表面附近保持介質(zhì)的存在。
利用酶與電極表面的直接電子傳遞來(lái)檢測(cè)膽固醇。范佳琳等將泡沫介孔硅(MCF)修飾的還原氧化石墨烯復(fù)合材料(McF@rGo)作為修飾電極,MCF的多孔給固定酶提供了很好的場(chǎng)所,在MCFs@rGO的輔助下,可以在固定化ChOx和電極之間實(shí)現(xiàn)有效的DET[38]。碳材料由于比表面積大"" (3 000 m2·0-1)、無(wú)毒、來(lái)源豐富、成本低廉、導(dǎo)電性好、綠色環(huán)保以及良好的化學(xué)穩(wěn)定性等優(yōu)點(diǎn)而被廣泛應(yīng)用[39]。另外,導(dǎo)電聚合物、金屬納米材料、復(fù)合材料等材料也可以實(shí)現(xiàn)固定化ChOx和電極之間實(shí)現(xiàn)的DET[40-46]。WU[47]等利用分層組裝(LBL)技術(shù)開(kāi)發(fā)了一種膽固醇電化學(xué)傳感器,它由水溶性聚乙烯亞胺還原氧化石墨烯復(fù)合材料和ChOx組成的。在優(yōu)化條件下,所制備的電極的膽固醇濃度呈較寬的線性范圍1×10-5~9.331×10-3mol·L-1,檢測(cè)限為0.021 μmol·L-1。這種檢測(cè)過(guò)程不受電活性物質(zhì)的干擾,不受溶解氧的影響,大大減少了溶解氧與電極之間競(jìng)爭(zhēng)再生酶的干擾效應(yīng)。
2.2" 無(wú)酶膽固醇電化學(xué)傳感器研究進(jìn)展
非酶膽固醇傳感器主要是借助金屬納米材料使膽固醇在電極表面直接電化學(xué)氧化。AKSHAYA[22]等通過(guò)包覆聚吡啶的磷酸釕納米團(tuán)簇促進(jìn)膽固醇的電化學(xué)氧化來(lái)測(cè)量膽固醇,如圖4所示。分散在聚吡咯中的聚吡咯納米團(tuán)簇促進(jìn)膽固醇的電化學(xué)氧化,發(fā)生負(fù)電位轉(zhuǎn)移,膽固醇的OH基團(tuán)被氧化為—C=O基團(tuán)。電化學(xué)線性響應(yīng)范圍為"nbsp;" 0.16~20.0 nmol0電-1,檢測(cè)限為5.4×10-9 mol·L-1。 KHALIQ[14]等研究了一種基于Cu2O-TiO2雜化納米結(jié)構(gòu)的新型安培非酶促膽固醇電化學(xué)傳感器。通過(guò)鈦(Ti)箔的陽(yáng)極氧化反應(yīng)合成了二氧化鈦納米管(TNTs),表面通過(guò)化學(xué)浴沉積(CBD)方法負(fù)載上氧化銅納米顆粒(NPs"),制備得到的樣品具有較好的形貌。這種材料具有良好的電化學(xué)活性、穩(wěn)定性以及較好的抗靜電性等特點(diǎn)。"在添加膽固醇后,與原始的低檢測(cè)限(0.05 μmol·L-1)和快速響應(yīng)時(shí)間(3 s)相比,混合電極的靈敏度增加了5倍。THAKUR[12]等開(kāi)發(fā)了一種基于聚(離子液體)-鈷聚氧金屬酸鹽的新型電化學(xué)傳感器,該新型復(fù)合材料對(duì)膽固醇的非酶電化學(xué)檢測(cè)限最低為 1 fmol·L-1 (1×10-15 mol·L-1),響應(yīng)時(shí)間為5 s,靈敏度為""" "64 μA·(μmol·L-1)-1·cm-2。非酶基膽固醇傳感器最大的優(yōu)點(diǎn)是易于實(shí)現(xiàn)長(zhǎng)期穩(wěn)定的目標(biāo)檢測(cè),克服了生物酶對(duì)環(huán)境溫度、pH值等因素的脆弱性,為快速電子遷移提供了優(yōu)化界面,并支持高性能連續(xù)監(jiān)控應(yīng)用場(chǎng)景。
3" 結(jié) 論
酶的使用受到儲(chǔ)存和分析條件的限制,成本很高。由于這些限制,研究者們正在努力開(kāi)發(fā)新的無(wú)酶膽固醇電化傳感器。無(wú)酶膽固醇電化學(xué)傳感器作為新一代的膽固醇傳感器,比酶基膽固醇電化學(xué)傳感器具有更好的性能和研究前景。目前,膽固醇直接電化學(xué)氧化的機(jī)理尚不清楚,需要進(jìn)一步研究。 大多數(shù)用于人體膽固醇含量檢測(cè)的新型電極有待開(kāi)發(fā)。隨著技術(shù)的進(jìn)一步發(fā)展和推廣,高性能膽固醇電化學(xué)檢測(cè)儀器將為高血壓和心血管疾病患者帶來(lái)福音。
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Research Progress in Electrochemical Methods for Cholesterol Detection
LYU Long-yang, GU Ting-ting, SHANG Shuai, LIN Chang-rui
(School of Chemical Engineering, University of Science and Technology Liaoning, Anshan Liaoning 114051, China)
Abstract: With the improvement of human life quality, measuring cholesterol has become an important research topic. Electrochemical detection of cholesterol has the advantages of high selectivity and high speed. In this paper, the electrochemistry principle and the latest progress in the determination of cholesterol by electrochemical methods in the presence and absence of enzymes were reviewed, and the prospect of electrochemical methods for the determination of cholesterol was also discussed.
Key words:" Cholesterol; Enzymes; Enzyme-free; Electrochemical sensors