CN113061649B - 检测microRNA的表面增强拉曼光谱传感器及其制备方法 - Google Patents
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Abstract
本发明提供了一种检测microRNA的表面增强拉曼光谱传感器及其制备方法,该传感器的构建主要分为三个部分:SERS标签的组装、基于热电极的DSN辅助目标循环信号放大、SERS基底的组装。本发明将AgNCs与4‑MBA和sDNA相结合以制备SERS标签。并将热电极技术与DSN辅助目标循环信号放大技术相结合,在DSN辅助目标循环信号放大过程中,通过提高电极的温度来提高DSN的活性,从而使得酶切循环过程更为高效彻底。本文的SERS传感器对miRNA‑21的检出限达到2.9 fM(S/N=3),且具有很高的特异性。
Description
技术领域
本发明属于生物传感器技术领域,具体涉及一种检测microRNA的表面增强拉曼光谱传感器及其制备方法。
背景技术
表面增强拉曼散射(SERS)是一种强大的分析技术,因其超高的灵敏度,窄的光谱带以及在各种环境中的通用性性,广泛用于检测包括小分子,蛋白质和核酸在内的生物标记物。 SERS信号通常可以可通过金,银和铜纳米粒子(如银纳米球,金纳米球和金纳米棒)增强。与球形贵金属纳米粒子相比,银纳米立方体(AgNCs)由于具有其几何特征而提供了更大的电场增强。因此,AgNC非常适合利用这些优势的SERS应用增强的近场。例如,Zhu等。通过在还原的氧化石墨烯板上包裹AgNCs开发出一种SERS传感器,用于高度灵敏地检测二硫代氨基甲酸酯杀虫剂,检测限(LOD)估计为10ppb。但据我们所知,AgNCs迄今尚未用作microRNA(miRNA)检测的SERS底物。
酶辅助信号放大技术由于反应条件温和、生物相容性好和催化效率高等优点而广泛用于生化分析中。常用工具酶包括聚合酶、核酸内切酶、核酸外切酶、连接酶等。双链特异性核酸酶(DSN)为一种核酸内切酶,因其对DNA双链体和RNA/DNA异源双链体有极强的切割偏好,对单链DNA,单链RNA和双链RNA的活性较小的特性,而在miRNA的信号放大中突显出巨大的优势。因此人们开发了许多基于DSN信号放大的传感器用于miRNA的检测。如Degliangeli等将荧光标记的DNA探针固定在金纳米颗粒(AuNPs)上。当存在目标miRNA时,DNA-RNA异源双链形成并被DSN识别并剪切,使得荧光基团从AuNPs上释放出来从而检测到荧光信号。目标miRNA重复循环杂交酶切,从而释放出更多的荧光基团,实现信号放大。通过荧光信号的改变来实现对目标miRNA的检测。
1990年代,Gründler等人开发了具有对称结构的直接电加热电极,该电极能够消除加热交流电对电化学信号的干扰,从而导致了加热电极的广泛应用和推广。现已有一系列基于不同材料的加热电极已开发并应用于痕量检测,如用将石墨加热电极用于核黄素的高灵敏检测,将玻碳加热电极用于细胞的高敏感检测。此外,将加热电极与生物酶结合可提高酶活性,从而提高检测灵敏度。例如,Wu等人将加热电极与核酸外切酶III结合使用,可对实现对Hg2+的高灵敏的电化学检测。但是据我们所知,加热电极还没有与双链特异性核酸酶(DSN)相结合,进行DSN辅助的目标循环扩增,并用SERS方法进行miRNA的检测。
发明内容
本发明的目的在于提供一种检测microRNA的表面增强拉曼光谱传感器及其制备方法。
为实现上述目的,本发明采用如下技术方案:
一种检测microRNA的表面增强拉曼光谱传感器的制备方法,包括如下步骤:
(1) SERS标签AgNCs/4-MBA/sDNA的组装
取10 μM 10 μL巯基修饰的sDNA,加入5 mM 10 μL TCEP,室温避光放置1 h,对二硫键进行还原,然后将其混入80 μL 8nM的AgNCs溶液中,加入300 μL的PBSS溶液混合均匀,37 ℃孵育过夜得到AgNCs/sDNA;接着向溶液中加入1 mM 4 μL的对巯基苯甲酸溶液,继续孵育2 h;然后将溶液离心,去除上清液后重新分散在400 μL的PBSS溶液中,重复离心3次后4℃保存备用;
(2)DSN辅助目标循环信号放大过程;
将金热电极HAuE依次用1 μm和0.05 μm的氧化铝粉在抛光布上进行抛光,然后在超纯水中超声清洗3 min,置于0.5 M NaOH溶液中− 0.35 - 1.35 V电位间连续扫描500圈,接着置于5 mM H2SO4溶液中− 0.35 - 1.5 V电位间扫描20圈,对电极进行电化学清洗,最后用超纯水清洗冲洗,氮气吹干;
在固定pDNA前,将10 μM 5 μL巯基修饰的 pDNA与5 mM 5 μL TCEP混匀室温避光处理1 h以断裂二硫键,然后取10μL滴到清洗干净的金热电极表面,4 ℃组装过夜得到pDNA/HAuE;超纯水冲洗后浸泡在2 mM MCH溶液中,室温封闭1 h得到MCH/pDNA/HAuE,同样用超纯水对电极表面进行清洗;
取179 μL一定浓度的miRNA-21,加入20 μL的10×DSN buffer和0.5 U/μL 1 μLDSN酶配置成总体积为200 μL的酶切液;将MCH/pDNA/HAuE浸泡于酶切液中进行酶切反应60min;酶切温度控制为55 ℃;反应完成后,向酶切液中加入10 mM 50 μL EDTA于55℃恒温反应10 min,对DSN酶进行失活处理,得到所需的含有rDNA的酶切液;
(3)SERS基底的组装及检测
按照上述金热电极HAuE相同的处理方法,对直径为3mm的金电极AuE进行抛光清洗;取10 μM 5 μL巯基修饰的cDNA与5 mM 5 μL TCEP混匀,室温避光孵育1 h;再加入PBS缓冲液稀释溶液至50 μL;取10 μL稀释液滴在清洗干净的AuE表面,4℃组装过夜得到cDNA/AuE;用PBS缓冲液冲洗电极表面后置于200 μL 2mM 的MCH溶液中1h,随后置于200 μL1wt.%的BSA溶液中1h,得到BSA/MCH/cDNA/AuE;将电极用PBS缓冲液冲洗干净并用N2轻轻吹干电极表面;滴加10 μL步骤(2)制备获得的含rDNA的酶切液在电极表面,37℃杂交反应4h得到rDNA/BSA/MCH/cDNA/AuE;同样用PBS缓冲液冲洗电极表面除去电极表面未杂交的DNA,然后电极浸泡于65 μL制备好的SERS标签AgNCs/4-MBA/sDNA中,37 ℃杂交反应4h得到SERS基底;然后对基底表面检测进行得到SERS信号。
所述sDNA为TTTTTTAGGGT(T)8-(CH2)6SH;pDNA为SH-(CH2)6-GCGCCCAACATCAGTCTGATAAGCTACCCTAAAAAACCACACGGCGC;cDNA为SH-(CH2)6-(T)8GCGCCGTGTGG。
本发明传感器原理:
将基于热电极的DSN辅助信号放大技术与和AgNCs的SERS增强技术相结合,构建了用于miRNA-21检测的SERS传感器。如图1所示,该传感器的构建主要分为三个部分:SERS标签的组装、基于热电极的DSN辅助目标循环信号放大、SERS基底的组装(具体步骤详见下方传感器的制备过程)。对于SERS标签的组装:信号探针sDNA与拉曼信号分子4-MBA均通过Ag-S键组装到AgNCs表面得到SERS标签AgNCs/4-MBA/sDNA。对于DSN辅助目标循环信号放大过程:巯基修饰的pDNA,通过Au-S键组装到HAuE表面,当目标miRNA-21存在时,pDNA的其中一部分将与目标杂交形成异源双链结构,双链体中的DNA链会被DSN识别并剪切。miRNA-21和pDNA中剩余未杂交的部分(rDNA)将被释放出来。释放出的miRNA-21可以继续与pDNA杂交进行下一个酶切循环,从而产生更多的rDNA片段。在此过程中,通过提高HAuE的温度来提高DSN酶的活性,从而使得该过程进行更快更彻底。SERS基底的组装过程:rDNA的3´端可以与AuE表面的捕获探针cDNA杂交,5′端与SERS标签上的sDNA杂交,将SERS标签组装到AuE表面制得SERS基底,从而在基底表面检测到SERS信号。
本发明的优点在于:
本发明将AgNCs与4-MBA和sDNA相结合以制备SERS标签。并将热电极技术与DSN辅助目标循环信号放大技术相结合,在DSN辅助目标循环信号放大过程中,通过提高电极的温度来提高DSN的活性,从而使得酶切循环过程更为高效彻底。本文的SERS传感器对miRNA-21的检出限达到2.9 fM(S/N = 3),且具有很高的特异性。
附图说明
图1 为检测microRNA的表面增强拉曼光谱传感器原理图。
图2为不同温度下SERS谱图,其中A为在不同电极温度下进行DSN辅助循环放大过程所得SERS谱图,a-g:35 ℃、40 ℃、45 ℃、50 ℃、55 ℃、60 ℃、65 ℃ ,B为相应SERS谱图在1586 cm−1 处的峰强变化。
图3为所述DSN用量、反应时间优化以及4-MBA浓度的优化图,其中A为DSN用量优化图,B为反应时间优化,C为4-MBA浓度的优化图。
图4为传感器对miRNA-21的高灵敏检测图。
图5为传感器的选择性图。
具体实施方式
传感器的制备过程所用碱基序列以及缓冲液
Tris缓冲液:10 mM Tris,0.1M NaCl,pH 7.4;
PBS缓冲液:10 mM PB,0.1 M NaCl,pH 7.4;
PBSS缓冲液:10 mM PB,0.1 M NaCl,0.01%(wt/vol)SDS,pH 7.4。
实施例1
一种检测microRNA的表面增强拉曼光谱传感器的制备方法,包括如下:
(1) SERS标签AgNCs/4-MBA/sDNA的组装
取10 μM 10 μL巯基修饰的sDNA,加入5 mM 10 μL TCEP,室温避光放置1 h,对二硫键进行还原,然后将其混入80 μL 8nM的AgNCs溶液中,加入300 μL的PBSS溶液混合均匀,37 ℃孵育过夜得到AgNCs/sDNA;接着向溶液中加入1 mM 4 μL的对巯基苯甲酸溶液,继续孵育2 h;然后将溶液离心,去除上清液后重新分散在400 μL PBSS溶液中,重复离心3次后4℃保存备用。
(2)DSN辅助目标循环信号放大过程;
将金热电极依次用1 μm和0.05 μm的氧化铝粉在抛光布上进行抛光,然后在超纯水中超声清洗3 min,置于0.5 M NaOH溶液中− 0.35 - 1.35 V电位间连续扫描500圈,接着置于5 mM H2SO4溶液中− 0.35 - 1.5 V电位间扫描20圈,对电极进行电化学清洗,最后用超纯水清洗冲洗,氮气吹干;
在固定pDNA前,将10 μM 5 μL巯基修饰的 pDNA与5 mM 5 μL TCEP混匀室温避光处理1 h以断裂二硫键,然后取10μL滴到清洗干净的金热电极表面,4 ℃组装过夜得到pDNA/HAuE;超纯水冲洗后浸泡在2 mM MCH溶液中,室温封闭1 h得到MCH/pDNA/HAuE,同样用超纯水对电极表面进行清洗;
取179 μL一定浓度的miRNA-21,加入20 μL的10×DSN buffer和0.5 U/μL 1 μLDSN酶配置成总体积为200 μL的酶切液;将MCH/pDNA/HAuE浸泡于酶切液中进行酶切反应60min;酶切温度控制为55℃;反应完成后,向酶切液中加入10 mM 50 μL EDTA于55℃恒温10 min,对DSN酶进行失活处理,得到所需的含有rDNA的酶切液;
(3)SERS基底的组装及检测
按照上述HAuE相同的处理方法,对直径为3mm的金电极(AuE)进行抛光清洗;取10μM 5 μL巯基修饰的cDNA与5 mM 5 μL TCEP混匀,室温避光孵育1 h;向上述混合液中加入PBS缓冲液稀释溶液至50 μL;取10 μL稀释液滴在清洗干净的AuE表面,4℃组装过夜得到cDNA/AuE;用PBS缓冲液冲洗电极表面后置于置于200 μL 2mM 的MCH溶液中1h,随后置于200 μL 1wt.%的BSA溶液中1h,得到BSA/MCH/cDNA/AuE;将电极用PBS缓冲液冲洗干净并用N2轻轻吹干电极表面;滴加10 μL步骤(2)制备获得的含rDNA的酶切液在电极表面,37℃杂交反应4h得到rDNA/BSA/MCH/cDNA/AuE;同样用PBS缓冲液冲洗电极表面除去电极表面未杂交的DNA,然后电极浸泡于65 μL制备好的SERS标签AgNCs/4-MBA/sDNA中,37 ℃杂交反应4h得到SERS基底;然后对基底表面检测进行得到SERS信号。 所用激光为He-Ne,激光波长为632.8nm,激光功率为最大功率的5%。
实施例2 温度的影响
双链特异性核酸酶(DSN)的活性与温度密切相关,为了研究金热电极HAuE的温度对DSN辅助目标循环信号放大过程的影响,将MCH/pDNA/HAuE浸入在含10 pM miRNA-21和0.6 U DSN的1× DSN缓冲溶液中,在不同电极温度下酶切90 min。用不同温度下酶切所得溶液进行SERS基底的组装,测得SERS谱图。如图2所示,当HAuE温度从35℃升高到55 ℃时,SERS峰强逐渐增加,而当温度高于60℃时,峰强开始下降。表明在一定范围内,升高温度可以提高DSN的活性,酶辅助循环过程更彻底,相应的SERS信号更强。因此本发明选择55 ℃作为最佳温度。
实施例3 DSN用量、反应时间优化以及4-MBA浓度的优化
为了获得更优异的检测性能,对实验过程中一些重要的条件进行了优化:DSN辅助目标循环信号放大过程中DSN的用量和反应时间,以及SERS标签的组装过程中信号分子4-MBA的浓度进行了优化。选择1586 cm−1处的SERS峰强作为效果评估的指标。首先对DSN的用量进行了探究。如图3-A所示,当DSN用量从0.1 U增加到0.5 U时,SERS强度也随之增强,当用量超过0.5 U后强度基本保持不变。因此,将0.5 U作为DSN的最佳用量。
然后对反应时间进行了优化,如图3-B所示,SERS强度随着反应时间的延长而增加,于60 min后趋于平稳。因此,将60 min作为后续实验的最佳反应时间。
另外,4-MBA的浓度直接影响到检测时的SERS峰强,因此对4-MBA的浓度也进行了优化。如图3-C,随着4-MBA浓度从1 μM增加到10 μM,SERS强度迅速增强。由于当4-MBA的浓度超过10 μM时,AgNCs粒子会出现聚集情况而无法继续试验,因此选择10 μM作为4-MBA分子的最佳浓度。
实施例4传感器对miRNA-21的高灵敏检测
在最优实验条件下,使用不同浓度的miRNA-21对传感器的分析性能进行探究。相应的SERS谱图如图4-A,可以看出当miRNA-21浓度从1×10−14 M增加至1×10−9 M,SERS强度也逐渐增强。图4-C(曲线a)为SERS强度与miRNA-21浓度的对数的线性关系,可以看出SERS强度与miRNA-21浓度在10 fM至1 nM范围呈良好的线性关系。线性方程为y = 33631.06 +2283.48 lg C(M)(R2 = 0.998),其中y表示1586 cm−1处的SERS峰强,计算得到检测限(LOD)为2.9 fM(S/N = 3)。
为了进一步探索HAuE的温度对传感器检测的影响,探究了HAuE温度为25 ℃,在其它条件为最优条件下,SERS峰强与miRNA-21浓度间的关系。如图4-C(曲线b),miRNA-21浓度与SERS强度在100 pM至10 nM范围内呈线性关系,线性方程为y = 8501.46 + 733.18 lg C(M)(R2 = 0.96)。计算得到LOD为7.4 pM(S/N = 3)。表明HAuE温度在55℃下,比在25℃下,检测极限可以降低大约3个数量级,进一步说明了通过提高HAuE的温度可以极大提高DSN的活性,从而提高miRNA-21检测的灵敏度。
实施例5 本发明SERS传感器对其它miRNA的响应:
我们使用miRNA-141(UAACACUGUCUGGUAAAGAUGG),miRNA-155(UUAAUGCUAAUCGUGAUAGGGGU)和非互补序列作为干扰物来评估该传感器的选择性。实验在相同的最佳条件下进行(即实施例1步骤),干扰物的浓度比目标物miRNA-21(1 pM)高10倍。如图5所示,在存在目标物miRNA-21的情况下,可以观察到明显的SERS信号,而空白实验(不存在miRNA-21)或加入其他干扰物质时,几乎无SERS信号。这些结果清楚地表明,本申请所提出的SERS传感器对于miRNA-21的检测具有极好的选择性。
实施例6本发明SERS传感器用于血清中加标回收率检测:
为了验证该传感器在miRNA-21检测中的适用性和可靠性,采用标准添加方法在血清样品中检测了目标miRNA-21,结果如表1。将不同浓度的miRNA-21(0.1、1和10 pM)加入稀释100倍的血清中,回收率在80.2 %至90.0 %的范围内,相对标准偏差(RSD)在2.8 %至6.9%之间。这些结果表明,所制备的传感器选择性高,有望用于实际样品检测。
表1
以上所述仅为本发明的较佳实施例,凡依本发明申请专利范围所做的均等变化与修饰,皆应属本发明的涵盖范围。
SEQUENCE LISTING
<110> 福州大学
<120> 检测microRNA的表面增强拉曼光谱传感器及其制备方法
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Claims (2)
1.一种检测microRNA的表面增强拉曼光谱传感器的制备方法,其特征在于:包括如下:
(1)SERS标签AgNCs/4-MBA/sDNA的组装
取10μM 10μL巯基修饰的sDNA,加入5mM 10μL TCEP,室温避光放置1h,对二硫键进行还原,然后将其混入80μL 8nM的AgNCs溶液中,加入300μL的PBSS溶液混合均匀,37℃孵育过夜得到AgNCs/sDNA;接着向溶液中加入1mM 4μL的对巯基苯甲酸溶液,继续孵育2h;然后将溶液离心,去除上清液后重新分散在400μL的PBSS溶液中,重复离心3次后4℃保存备用;
(2)DSN辅助目标循环信号放大过程
将金热电极HAuE依次用1μm和0.05μm的氧化铝粉在抛光布上进行抛光,然后在超纯水中超声清洗3min,置于0.5M NaOH溶液中-0.35~1.35 V电位间连续扫描500圈,接着置于5mMH2SO4溶液中-0.35~1.5 V电位间扫描20圈,对电极进行电化学清洗,最后用超纯水清洗冲洗,氮气吹干;
在固定pDNA前,将10μM 5μL巯基修饰的pDNA与5mM 5μL TCEP混匀室温避光处理1h以断裂二硫键,然后取10μL滴到清洗干净的金热电极表面,4℃组装过夜得到pDNA/HAuE;超纯水冲洗后浸泡在2mM MCH溶液中,室温封闭1h得到MCH/pDNA/HAuE,同样用超纯水对电极表面进行清洗;
取179μL一定浓度的miRNA-21,加入20μL的10×DSN buffer和0.5U/μL 1μL DSN酶配置成总体积为200μL的酶切液;将MCH/pDNA/HAuE浸泡于酶切液中进行酶切反应60min;酶切温度控制为55℃;反应完成后,向酶切液中加入10mM 50μL EDTA于55℃恒温反应10min,对DSN酶进行失活处理,得到所需的含有rDNA的酶切液;
(3)SERS基底的组装及检测
按照上述金热电极HAuE相同的处理方法,对直径为3mm的金电极AuE进行抛光清洗;取10μM 5μL巯基修饰的cDNA与5mM 5μL TCEP混匀,室温避光孵育1h;再加入PBS缓冲液稀释溶液至50μL;取10μL稀释液滴在清洗干净的AuE表面,4℃组装过夜得到cDNA/AuE;用PBS缓冲液冲洗电极表面后置于200μL 2mM的MCH溶液中1h,随后置于200μL 1wt.%的BSA溶液中1h,得到BSA/MCH/cDNA/AuE;将电极用PBS缓冲液冲洗干净并用N2轻轻吹干电极表面;滴加10μL步骤(2)制备获得的含rDNA的酶切液在电极表面,37℃杂交反应4h得到rDNA/BSA/MCH/cDNA/AuE;同样用PBS缓冲液冲洗电极表面除去电极表面未杂交的DNA,然后电极浸泡于65μL制备好的SERS标签AgNCs/4-MBA/sDNA中,37℃杂交反应4h得到SERS基底;然后对基底表面检测进行得到SERS信号;
所述sDNA为TTTTTTAGGGT(T)8-(CH2)6SH;pDNA为SH-(CH2)6-GCGCCCAACATCAGTCTGATAAGCTACCCTAAAAAACCACACGGCGC;cDNA为SH-(CH2)6-(T)8GCGCCGTGTGG。
2.如权利要求1所述的制备方法制备获得的检测microRNA的表面增强拉曼光谱传感器。
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