生物工程学报  2024, Vol. 40 Issue (2): 367-377
http://dx.doi.org/10.13345/j.cjb.230482
中国科学院微生物研究所、中国微生物学会主办
0

文章信息

王佳慧, 赵佩佩, 秦梦飞, 赵燕秋, 刘成伟, 夏雪奎
WANG Jiahui, ZHAO Peipei, QIN Mengfei, ZHAO Yanqiu, LIU Chengwei, XIA Xuekui
CRISPR传感检测技术的研究进展
Advances in CRISPR sensing and detection technology
生物工程学报, 2024, 40(2): 367-377
Chinese Journal of Biotechnology, 2024, 40(2): 367-377
10.13345/j.cjb.230482

文章历史

Received: July 1, 2023
Accepted: September 8, 2023
Published: September 21, 2023
CRISPR传感检测技术的研究进展
王佳慧1 #, 赵佩佩1 #, 秦梦飞2 , 赵燕秋1 , 刘成伟3 , 夏雪奎1     
1. 齐鲁工业大学(山东省科学院)生物研究所, 山东 济南 250103;
2. 黑龙江大学现代农业与生态环境学院, 黑龙江 哈尔滨 150080;
3. 东北林业大学生命科学学院, 黑龙江 哈尔滨 150040
摘要:CRISPR传感检测技术具有便宜、简单、便携、高灵敏和高特异等优点,被称为“下一代分子诊断技术”。由于CRISPR-Cas系统具有特异的识别、顺式切割和非特异性的反式切割能力,已经实现了对DNA和RNA等核酸靶标以及蛋白质、外泌体、细胞和小分子等非核酸靶标的检测。为了解不同CRISPR传感检测技术的优势和发展历程,促进该技术的发展和应用,本文根据不同Cas蛋白的活性特征,对目前的CRISPR传感检测技术进行了分类总结,并在此基础上根据检测的靶标类型,依次总结了各种CRISPR传感检测技术的应用情况,以期为开发新型CRISPR传感检测技术提供参考。
关键词规律间隔成簇短回文重复序列(CRISPR)    生物传感器    即时检测    分子诊断    
Advances in CRISPR sensing and detection technology
WANG Jiahui1 #, ZHAO Peipei1 #, QIN Mengfei2 , ZHAO Yanqiu1 , LIU Chengwei3 , XIA Xuekui1     
1. Biology Insititute, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250103, Shandong, China;
2. School of Modern Agriculture and Ecology and Environment, Heilongjiang University, Harbin 150080, Heilongjiang, China;
3. College of Life Sciences, Northeastern Forestry University, Harbin 150040, Heilongjiang, China
Abstract: The CRISPR sensing and detection technology has the advantages of cheap, simple, portable, high sensitivity, and high specificity, therefore is regarded as the "next-generation molecular diagnostic technology". Due to the specific recognition, cis-cleavage and nonspecific trans-cleavage capabilities, CRISPR-Cas systems have been implemented for the detection of nucleic acid targets (DNA and RNA) as well as non-nucleic acid targets (e.g., proteins, exosomes, cells, and small molecules). This review summarizes the current CRISPR sensing and detection technologies in terms of the activity characteristics of different Cas proteins, with the aim to understand the advantages and development history of different CRISPR sensing and detection technologies, as well as promote its development and application. Moreover, this review summarizes the applications of various CRISPR sensing and detection technologies according to the types of detection targets, hoping to facilitate the development of novel CRISPR sensing detection technology.
Keywords: clustered regulatory interspaced short palindromic repeats (CRISPR)    biosensors    instant detection    molecular diagnostics    

高灵敏、高特异、低成本的生物传感技术的开发,有助于代谢产物、环境分子、疾病标志物和流感病毒等靶标检测传感器的构建,对于生物学研究、环境监测、卫生安全和食品安全等具有重要的意义。同时,大型仪器因昂贵和操作繁琐无法适应日益增长的检测需求,需要小巧且便于应用于现场即时检测的生物传感器进行补充和替代。因此,拓展新工具并开发通用的传感检测平台,将有利于加快各种生物传感器的构建和应用。

规律间隔成簇短回文重复序列与关联蛋白系统(clustered regulatory interspaced short palindromic repeats-CRISPR-associated protein, CRISPR-Cas)是古菌和细菌的一种适应性免疫系统,包括CRISPR和Cas蛋白,已被用作强大的RNA引导的DNA/RNA靶向平台。CRISPR-Cas系统具有强大的基因编辑能力,由于其对Cas蛋白的特异性或非特异性切割活性,极大地激发了人们对开发新型检测工具的兴趣。利用CRISPR-Cas系统的多样性来设计不同的基因序列,能够对不同的靶标进行特异性和低成本的检测。因此,理解和应用CRISPR-Cas技术将有助于进一步探索疾病诊断的边界。随着CRISPR-Cas技术的增强,该系统的应用逐渐从核酸扩展到非核酸,如蛋白质、金属离子等。Cas系统对核酸的特异性识别使其被纳入各种信号放大方法中,用于灵敏检测微量物质,并有助于在现场及时检测,以进行后续研究。

CRISPR-Cas技术的出现极有可能成为生物传感领域的一个里程碑。本文首先总结了CRISPR-Cas系统的不同结构、特征和能力,以更好地了解每个Cas系统之间的异同(表 1)。随后,将Cas测定的靶标分为核酸类和非核酸类,强调它们在生物测定中的经典应用。这些检测方法已用于单核苷酸多态性(single nucleotide polymorphisms, SNP)、miRNA、蛋白质和外泌体等的检测。相信随着技术的进一步发展,CRISPR-Cas相关生物传感器可能会发生革命性的变化。

表 1 不同CRISPR-Cas系统的结构和特点 Table 1 Structures and features of different CRISPR-Cas systems
Item Cas9 Cas12 Cas13 Cas14
Subtypes Type Ⅱ Type Ⅴ Type Ⅵ Type Ⅴ
Nuclease domains HNH, RuvC RuvC HEPN RuvC
Guide RNA tracrRNA, crRNA crRNA crRNA crRNA, tracrRNA
Target dsDNA, ssDNA, ssRNA dsDNA, ssDNA ssRNA ssDNA, dsDNA
Trans-cleavage substrates ssDNA ssDNA ssDNA
PAM/PFS 5′-NGG-3′ TTTN Non-G-PFS
Advantages DNA target detection; signal amplification by trans-cleavage No PAM sequence restrictions; distinguish single base differences PAM sequence restriction for dsDNA detection; lower specificity for ssDNA detection Smaller size; no PAM sequence restrictions; distinguish single base differences
Disadvantages RNA target detection; signal amplification by trans-cleavage PAM sequence restriction; additional signal amplification means PAM sequence restriction longer sgRNA
–: No trans-cleaving activity or no PAM/PFS sequence.
1 CRISPR-Cas传感检测系统的分类 1.1 基于Cas9的传感技术

Cas9属于Ⅱ型CRISPR系统,含有HNH和RuvC结构域,由Cas9蛋白、反式激活crRNA (trans-activating crRNA, tracrRNA)和crRNA复合体对目的基因进行编辑。Cas9能够识别质粒和噬菌体的原型间隔序列毗邻基序(protospacer adjacent motif, PAM) NGG序列,然后crRNA-tracrRNA复合体与cDNA进行配对,Cas9随后对目标DNA进行双链切割(图 1A)[1]。研究人员通过结合DNA荧光原位杂交及构建核酸酶失活的dCas9等方式,开发了不依赖于反式切割活性的基于Cas9的生物传感检测技术[2-3]。此外通过补充相关的PAM序列,也可以靶向单链RNA (single-stranded RNA, ssRNA)[4]。虽然基于Cas9的生物传感检测技术表现不俗,但真正开启CRISPR传感检测技术时代帷幕的,是基于Cas13反式切割放大活性开发的特异性高灵敏度酶报告基因解锁(specific high-sensitivity enzymatic reporter unlocking, SHERLOCK)技术。

图 1 CRISPR-Cas结构和切割活性示意图[1] Fig. 1 Schematic representation of CRISPR-Cas structure and cleavage activities[1]. A: Schematic diagram of Cas9 cleavage activity. crRNA can bind to tracrRNA and guide Cas9 to recognize and cleave specific dsDNA with PAM sequences. The HNH structural domain of Cas9 cleaves one strand of dsDNA complementary to crRNA, and the RuvC structural domain cleaves another strand of dsDNA. B: Schematic diagram of Cas12a cleavage activity. Cas12a has only one RuvC catalytic structural domain. Under the guidance of crRNA, Cas12a can recognize the T-rich PAM sequence and specifically cleaves dsDNA while non-specifically cleaving surrounding ssDNA. C: Schematic diagram of Cas13a cleavage activity. Cas13a contains two HEPN domains that can specifically recognize and cleave target ssRNA while non-specifically cleaving surrounding ssRNA under the guidance of crRNA. D: Schematic diagram of Cas14a cleavage activity. Under the guidance of tracrRNA and crRNA, Cas14 can specifically bind and cleave target ssDNA without PAM, and non-specifically cleave ssDNA in the vicinity.
1.2 基于Cas12的传感技术

Cas12a属于Ⅴ型CRISPR系统,由王金团队于2015年发现,是第一个用于基因组编辑的Cas12核酸酶[5]。与Cas9不同的是,Cas12a只有一个RuvC催化结构域,在crRNA的介导下靶向切割双链DNA[6],并在切割完成后形成特定构象的三元复合物,激活对非特异性单链DNA (single-stranded DNA, ssDNA)的反式切割活性(图 1B)。此外CRISPR-Cas12b (又称C2c1)是一种独特的V-B型DNA核酸内切酶系统。与Cas12a不同,crRNA和trrRNA与Cas12b的结合对于向导链和靶标链之间的配对至关重要[7]。值得注意的是,Cas12b的体积比Cas9和Cas12a小,并对在单核苷酸错配极其敏感[8]

1.3 基于Cas13的传感技术

Cas13属于Ⅵ型CRISPR系统,具有两个较高的真核生物和原核生物核苷酸结合(higher eukaryotic and prokaryotic nucleasedomains, HEPN)结构域(图 1C),在crRNA的介导下靶向切割RNA,产生对非特异性RNA的反式切割活性[9-10]。利用这些特性,张峰团队建立了第一个基于CRISPR-Cas13a的核酸检测系统SHERLOCK,利用T7转录结合重组聚合酶扩增使信号二次放大,实现了以单碱基分辨率检测DNA和RNA靶标[11]。进一步改善的SHERLOCKv2结合核糖核酸酶Csm6使信号灵敏度提高了3.5倍,并且检测时间缩短到30 min[12]

1.4 基于Cas14的传感技术

Cas14属于Ⅴ型CRISPR-Cas系统,大小只有400−700个氨基酸,迄今为止被证明是最小的第Ⅱ类CRISPR效应器。它是一种靶向ssDNA的CRISPR内切酶,与CRISPR-Cas12a不同,在gRNA的介导下,Cas14以不依赖PAM位点的方式特异性识别靶ssDNA序列[13],并激活其特异性的顺式切割活性以及非特异性的反式切割活性。与Cas12类似,Cas14a也是Ⅴ型的,能与目标核酸结合,进而激活ssDNA反式切割活性(如图 1D),可用于目标核酸的分子检测。各种CRISPR-Cas检测系统比较见表 1

2 CRISPR检测技术的应用 2.1 核酸 2.1.1 基因检测

CRISPR-Cas系统对核酸的特异性识别在核酸检测中提供了独特的优势,而靶标量少、粗品浓度的信号转换和放大是分析系统中的关键挑战。一开始需将CRISPR-Cas系统与核酸扩增技术相结合实现信号放大,但随着对Cas12a、Cas13a和Cas14蛋白反式切割活性的鉴定,利用靶标结合后激活的反式切割活性,可以在一定程度上实现对原始信号的扩增。此外通过结合各种信号输出方法,一系列的无扩增系统被相继开发出来,实现了对核酸的高灵敏度和选择性的检测。

CRISPR-Cas9系统在sgRNA的指导下可实现对dsDNA特异性切割。Huang等[14]建立了CRISPR-Cas9触发的等温指数放大反应(CAS-EXPAR)方法,在无外部引物条件下,通过将单碱基甲基化转化为单碱基突变,实现位点特异性DNA甲基化检测,这对于监测肿瘤的诊断和预后至关重要。与石墨烯相结合开发了一种基于CRISPR的石墨烯场效应晶体管技术(CRISPR-chip)[15],对靶DNA进行无扩增的直接检测。

而Cas12a的反式切割活性提供了一种新思路:通过将非特异性报告基因(如ssDNA)加载到Cas12a系统中,在检测到靶DNA的同时,报告基因将被切割以释放荧光等信号。基于这一特性开发了DNA核酸内切酶靶向CRISPR反式报告基因(DNA endonuclease-targeted CRISPR trans reporter, DETECTR)[16],实现了对人乳头状瘤病毒(human papilloma virus, HPV)的检测。利用Cas12a反式切割荧光标记的ssDNA的活性开发了HOLMES,将相关的PAM序列引入引物中,对SNP位点进行检测。HOLMES与DETECTER系统的不同之处在于,HOLMES借助PCR扩增。进一步研究发现Cas12b具有与Cas12a相似的切割活性,并具有单碱基分辨率。王金团队开发了基于LAMP和Cas12b的一锅一步诊断系统(HOMLESv2)[17],可特异性鉴别SNPs,检测病毒RNA、人细胞mRNA和环状RNA等多种靶标。李维等开发了Cas12b介导的DNA检测方法(CDetection)[18],可以在单碱基水平上区分HPV病毒核酸序列的差异。为了提高信号检测器的灵敏度,CRISPR-Cas12a与电化学结合开发了E-CRISPR系统,Cas12a的反式切割可以在靶核酸存在的情况下被激活,并且与金电极偶联的亚甲基蓝(methylene blue, MB)修饰的ssDNA可以被切割,导致MB的分离和导电性的转变,通过电流值的变化来监测目标核酸[19]

Cas13没有严格的序列限制,具有遗传修饰功能,可作为干扰RNA的工具用于编辑病原体突变的RNA序列等领域。张峰团队[10]首先提出SHERLOCK方法,在低浓度下检测到DNA和RNA的单分子。Myhrvold等[20]将SHERLOCK方法优化为加热未提取的诊断骨质样品以消除核酸酶(heating unextracted diagn ostic samples to obliterate nucleases, HUDSON),简化了DNA/RNA提取和纯化等操作,使SHERLOCK方法可用于直接检测临床样品中的病毒核酸。Freije等基于SHERLOCK开发了Cas13辅助限制病毒表达和读出(Cas13 assisted restriction of viral expression and readout, CARVER),增加了Cas13的切割功能,用于快速诊断和治疗[19]

将DETECTR的原理与Cas14a的非特异性切割活性相结合,开发了Cas14a-DETECTR,它可以实现高保真SNP基因组分型[21]。结果表明,当检测与蓝色或棕色眼睛相关的HERC2基因时,Cas12a不能区分2个ssDNA靶点,而Cas14a在识别蓝色眼睛SNPs方面表现出增强作用。CRISPR-Cas14系统与HUDSON结合[20],检测更加方便,并已成功应用于细小病毒检测人类博卡病毒(human bocavirus, HBoV1)[22]

2.1.2 miRNA检测

miRNA是长度约为22 bps的小的单链非编码RNA,通过与靶mRNA结合来调节基因表达。miRNA的基因调控对人类的发育、分化、生长和代谢至关重要。miRNA可作为各种疾病相关的生物标志物。Qiu等[23]开发了滚动圆扩增-CRISPR-分裂-辣根过氧化物酶(rolling circle amplification-CRISPR-split-horseradish peroxidase, RCH)系统,通过RCA技术对靶miRNAs进行等温扩增,再使用一对分别与半个分裂辣根过氧化物酶(split-horseradish peroxidase, sHRP)蛋白融合的dCas9效应子,用于结合扩增的靶序列。dCas9效应子与附近靶序列的结合,会导致sHRP的重建,最后加入显色底物四甲基联苯胺(tetramethylbenzidine, TMB)产生相应的比色信号。该方法灵敏度高,适用于检测临床血清样品中的miRNAs。Shan等[24]基于Cas13a/crRNA复合体通过对靶标miRNAs进行特异性识别,激活了Cas13a的酶切活性,从而产生荧光信号。该方法简便、快速,但需要与等温扩增等方法相结合以进一步提高检测灵敏度。Zhou等[25]将Cas13a切割活性与电化学发光技术相结合,构建了PECL (portable-electroche milumi nescence)-CRISPR平台。通过靶标miRNAs激活Cas13a的酶切活性,对设计好的引物进行裂解,从而触发指数扩增和ECL检测。该方法可达到单核苷酸分辨率,适用于检测肿瘤细胞中的miRNAs,在分子诊断方面具有广阔的应用前景。一些CRISPR-Cas核酸检测系统见表 2

表 2 基于CRISPR-CAS的核酸检测系统 Table 2 Nucleic acid detection system based on CRISPR-Cas systems
Cas Target Technology Amplification Detection References
Cas9 DNA DNA-FISH Fluorescence detection [1]
DNA PC PCR Fluorescence detection [2]
DNA/RNA CAS-EXPAR EXPAR Real-time fluorescence [14]
DNA/RNA FELUDA RPA/PCR Paper-based IF device [26]
DNA/RNA CASLFA RPA/PCR Paper-based IF device [27]
Cas12 DNA DETECTR RPA Fluorescence detection [16]
DNA/RNA HOLMESv2 LAMP Fluorescence detection [17]
DNA CDetection RPA Fluorescence detection [18]
DNA/RNA HOLMES PCR Fluorescence detection [28]
RNA CRISPR-Cas12a-NER RT-RAA Naked eye [29]
DNA CRISPR-Cas12a PCR/LAMP Naked eye [30]
DNA POC RPA/LAMP Fluorescence detection [31]
RNA STOPCovid RT-LAMP Fluorescence/
Lateral flow detection
[32]
RNA CASdetec RT-RAA Naked eye [33]
Cas13 RNA HUDSON RPA Fluorescence detection [20]
RNA SHERLOCKv2 RPA Fluorescence detection [11]
DNA/RNA mCas13 RT-LAMP Fluorescence detection [34]
RNA SHERLOC Fluorescence detection [35]
DNA SHERLOC RPA qPCR [36]
DNA CREST RPA/PCR Fluorescence detection [37]
DNA APC-Cas RT-qPCR Fluorescence detection [38]
Cas14 DNA Cas14-DETECTR PT Fluorescence detection [21]
−: No expansion is required.
2.2 小分子 2.2.1 基于别构转录因子的小分子检测

别构转录因子(allosteric transcription factors, aTFs)通常用于基于配体识别时aTF和DNA序列之间结合亲和力的变化来调节基因表达。因此,基于aTF的生物传感器可广泛应用于检测多种分子。Liang等开发了CaT-SMelor成功地检测了人类血清样本中的尿酸和对羟基苯甲酸及其结构相似的类似物[39]。当aTF与其他小分子结合时,它与dsDNA基序的亲和力降低。

随后,释放dsDNA以触发CRISPR-Cas12a的反式切割活性。通过测量荧光信号的变化,可以准确地测量目标小分子。此外,CRISPR-Cas12a阵列结合四环素阻遏因子(tetracycline inhibitor, TetR),在配体存在的情况下,aTF的解离使CRISPR阵列进行转录;激活Cas12a反式切割活性,裂解单链DNA连接物以释放猝灭的荧光团,以其高灵敏度和特异性检测了不同的四环素类抗生素[40]

2.2.2 基于适配体的小分子检测

CRISPR-Cas系统可以与功能核酸(functional nucleic acids, FNAs)和分子翻译器结合使用,用于检测非核酸目标。FNAs和分子翻译器将非核酸靶标的检测转化为替代核酸靶标,例如单链DNA,它们可以启动扩增检测策略。目前研究实现了利用通用性功能DNA (functional DNA, fDNA)检测ATP或Na+[41],以及将CRISPR-Cas系统与适配体对目标物的良好亲和力相结合,成功检测了肿瘤标记物AFP和可卡因[42]。基于SHERLOCK的体外转录分析系统(SPRINT)[43]利用核糖开关或蛋白质通过特定的效应器分子来调节转录,定量检测了辅因子、核苷酸、氨基酸的代谢物、四环素和单原子离子。此外CRISPR-Cas系统也能与金属同位素检测相结合[44],在室温(25 ℃)下45 min内实现痕量氨苄青霉素水溶液的定量检测。

2.3 蛋白质

蛋白质检测的挑战是如何进行特异性识别和有效的信号转导。适配体可以有效地与靶蛋白结合,产生CRISPR-Cas系统识别的核酸激活剂。Dai等[19]使用这种方法与电化学生物传感器结合,检测了转化生长因子b1蛋白。将Cas12a的反式ssDNA切割活性与适配体对广泛的目标分析物的良好亲和力相结合,检测了肿瘤标记物甲胎蛋白[42]。通过CRISPR-Cas12a生物传感器实现对乌拉西-DNA糖酶(Ulasi-DNA glycase, UDG)和T4多核苷酸激酶(T4 polynucleotide kinase, T4 PNK)的超敏感检测[45],而且可作为检测单细胞解氧和人体血浆的强大工具箱[46]。电化学适体传感器已广泛用于蛋白质生物标志物的检测和定量,但其实际应用中受到信号放大效率低下和探针表面固定过程费力费时的限制。Qing等[47]通过将BIDSD与滚环扩增(roll ring amplification, RCA)和CRISPR-Cas12a相结合,实现了对凝血酶的特异性检测。基于CRISPR-Cas12a,整合无PCR扩增和双核酸适配体协同传感,实现在唾液或血清样品中超灵敏、快速和稳定性检测SARS-CoV-2抗原核衣壳蛋白[48]

2.4 外泌体

外泌体是非侵入性疾病诊断和治疗的最有前景的生物标志物。在外泌体表明通常含有过度表达特定的蛋白受体时,可用来检测外泌体。Zhao等[49]开发了一种基于CD63适配体和CRISPR-Cas12a系统的快速灵敏的CD63蛋白检测方法。首先CD63适配体被部分互补的ssDNA固定在磁珠上,当CD63适配子捕获CD63蛋白时,释放ssDNA阻断剂,然后利用磁铁收集CD63蛋白和CD63适配体的复合体。上清液中的ssDNA阻断剂可被CRISPR-Cas12a系统识别,导致单链DNA报告分子的裂解产生荧光信号,为外泌体的检测和诊断提供了一种高度灵敏和特异的方法。

2.5 细胞

在CRISRP-Cas检测策略中,一般使用适配体与细胞表面受体结合,使信号从细胞到核酸的传递,从而激活CRISPR系统。将核酸的变构探针和CRISPR-Cas13a相结合开发的APC-Cas系统[50],可高灵敏度检测肠炎沙门氏菌(Salmonellaenteritidis)细胞,该系统可以使用三级放大来生成强大的荧光信号,无需分离即可检测极少量的细菌病原体。在肿瘤的发展过程中,循环肿瘤细胞(circulating tumor cells, CTCs)会发生转移。Lv等[51]建立了一个多价双链适体网络Cas12a (multivalent double-stranded aptamer network Cas12a, MDANs-Cas12a),用于检测CTCs和调查癌症转移。该系统由多价双链核酸适体网络(multivalent double-stranded aptamer network, MDANs)调节,通过滚环扩增(RCA)在磁珠表面合成MDANs。靶细胞存在时可以触发游离“激活DNA”从MDANs结构中释放出来,激活下游的Cas12a进行信号放大。CTCs的检测为CRISPR-Cas系统在细胞检测中提供了一种新策略。

3 总结与展望

CRISPR-Cas传感技术具有高效、特异、灵敏、便携、便宜和通用的特征,这对核酸和非核酸等靶标检测具有重要的意义。且具有检测放大能力的Cas蛋白种类丰富,使得CRISPR传感技术表现出对不同类型核酸如RNA、单链DNA、双链DNA等专一的检测能力,这对适应不同检测场景具有很好的底层支撑作用。此外,别构转录因子、适配体等传感元件的使用,大大拓展了CRISPR传感技术在不同尺度靶标下的检测能力;便携荧光计、侧向流试纸条、石墨烯芯片等的使用提高了该技术即时简便的功能;快速无污染的核酸提取技术如一锅法SHERLOCK技术的开发,使得该技术更具有普适性;Cas蛋白串联放大技术以及其他元件的串联应用,使得该技术的灵敏度极高,检测时长很短。CRISPR传感技术因其优异的表现,在该技术出现的短短几年时间就迅速发展,成为广泛开发应用的新一代检测技术。

在已知的检测技术中,CRISPR传感技术虽然优异,但相较于抗体检测不够即时,相较于PCR检测不够灵敏,这是阻碍其应用的主要因素。不过,随着研究的深入,电化学传感技术对于不依赖于PCR提高CRISPR传感技术灵敏度具有很好的助力。目前利用标有大量的亚甲基蓝(methylene blue, MB)信号探针,将CRISPR-CAS12a与石墨烯电传感器相结合,极大提高了检测灵敏度。此外,对于非核酸目标的检测,需要提前将其转换为核酸信号。适配子和DNAzyme是常用的单链DNA或单链RNA寡核苷酸,可以与非核酸靶标特异结合,作为Cas蛋白的激活剂。然而,单链激活子获得的Cas蛋白活性低于双链激活子和PAM序列。设计一种互补的单链激活剂与之杂交是一种替代方法。此外,通过合理优化单链激活子序列,有可能提高Cas蛋白的切割活性。

本团队前期利用CRISPR-Cas12a系统分别构建了铜绿假单胞菌(Pseudomonas aeruginosa)核酸检测传感器、尿素小分子检测传感器[42]、甲胎蛋白检测传感器[19]及新冠病毒检测传感器[50]。近期利用CRISPR-Cas12系统实现对铜绿假单胞菌、荧光假单胞菌(Pseudomonas fluorescens)和丁香假单胞菌(Pseudomonas syringae) 3种检测体系在分子和菌体水平的高灵敏、便捷、快速同属或异种的鉴定,并与荧光定量PCR的重合率高达100%,更适用于各种检测条件。从基础的核酸检测应用开始,逐次引入别构转录因子、核酸适配体传感元件及创建双适配体协同放大策略,不断拓展升级CRISPR-Cas12a检测的应用范围。随着检测尺度的拓展,不同尺度多靶点的同时检测技术将是下一步发展的方向。同时一锅法多通道和高灵敏CRISPR传感检测技术的发展具有很大的吸引力,但耗时短至秒级的即时检测是需要解决的难点。随着CRISPR传感技术的发展,其在科学研究、卫生医疗、工业发酵、农业生产和环境保护方面将会得到越来越广泛的应用。

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