On-chip graphene oxide aptasensor for multiple protein detection

The versatility of an on-chip graphene oxide (GO) aptasensor was successfully confirmed by the detection of three different proteins, namely, thrombin (TB), prostate specific antigen (PSA), and hemagglutinin (HA), simply by changing the aptamers but with the sensor composition remaining the same. The results indicate that both DNA and RNA aptamers immobilized on the GO surface are sufficiently active to realize an on-chip aptasensor. Molecular selectivity and concentration dependence were investigated in relation to TB and PSA detection by using a dual, triple, and quintuple microchannel configuration. The multiple target detection of TB and PSA on a single chip was also demonstrated by using a 2 × 3 linear-array GO aptasensor. This work enables us to apply this sensor to the development of a multicomponent analysis system for a wide variety of targets by choosing appropriate aptamers.     

A sensitive fluorescence anisotropy method for detection of lead (II) ion by a G-quadruplex-inducible DNA aptamer

Sensitive and selective detection of Pb²⁺ is of great importance to both human health and environmental protection. Here we propose a novel fluorescence anisotropy (FA) approach for sensing Pb²⁺ in homogeneous solution by a G-rich thrombin binding aptamer (TBA). The TBA labeled with 6-carboxytetramethylrhodamine (TMR) at the seventh thymine nucleotide was used as a fluorescent probe for signaling Pb²⁺. It was found that the aptamer probe had a high FA in the absence of Pb²⁺. This is because the rotation of TMR is restricted by intramolecular interaction with the adjacent guanine bases, which results in photoinduced electron transfer (PET). When the aptamer probe binds to Pb²⁺ to form G-quadruplex, the intramolecular interaction should be eliminated, resulting in faster rotation of the fluorophore TMR in solution. Therefore, FA of aptamer probe is expected to decrease significantly upon binding to Pb²⁺. Indeed, we observed a decrease in FA of aptamer probe upon Pb²⁺ binding. Circular dichroism, fluorescence spectra, and fluorescence lifetime measurement were used to verify the reliability and reasonability of the sensing mechanism. By monitoring the FA change of the aptamer probe, we were able to real-time detect binding between the TBA probe and Pb²⁺. Moreover, the aptamer probe was exploited as a recognition element for quantification of Pb²⁺ in homogeneous solution. The change in FA showed a linear response to Pb²⁺ from 10 nM to 2.0 μM, with 1.0 nM limit of detection. In addition, this sensing system exhibited good selectivity for Pb²⁺ over other metal ions. The method is simple, quick and inherits the advantages of aptamer and FA.     

核酸适配体在癌症诊断中的研究进展

核酸适配体是通过指数富集配体系统进化技术(SELEX)从体外合成的寡核苷酸文库中筛选得到的短的寡核苷酸分子(ssDNA或RNA).核酸适配体能够通过折叠成特定的空间结构与靶标分子进行特异性结合,与抗体相比,适配体具有高亲和力、易修饰、低成本、易于合成和低免疫原性等优势,可以针对细胞、蛋白质、组织、生长因子进行癌症生物标...     

基于DNA和小沟结合染料DAPI快速检测水样中Hg2+

设计了一条DNA序列作为专一识别Hg2+的探针,结合小沟结合染料DAPI,构建了一种新型无标记荧光降低型核酸适体传感器。无Hg2+时DNA折叠成稳定的茎-环结构,DAPI插入茎部位有强荧光发射;Hg2+存在时DNA发生结构转变,DAPI释放荧光降低。结果表明：在最佳实验条件下,体系荧光降低百分数和Hg2+浓度正相关,在较低的浓度范围（0.5~50nmol/L）仍呈良好的线性关系,实际检出限为0.5nmol/L。该方法操作简单、对于环境水样中Hg2+的快速实时检测具有潜在的应用前景。     

Cell-SELEX-based aptamer-conjugated nanomaterials for enhanced targeting of cancer cells

Early detection and treatment of cancer depends on developing highly sensitive and specific methods for targeting cancer cells. To do this, aptamers, which are generated by a novel technique called cell-SELEX (systematic evolution of ligands by exponential enrichment), have been widely applied in cancer cell targeting based on such merits as high target affinity and specificity, small size, minimal immunogenicity, and ease of chemical modification. Furthermore, aptamers can gain more flexibility as cancer c...     

Enhanced Peroxidase‐Like Properties of Graphene–Hemin‐Composite Decorated with Au Nanoflowers as Electrochemical Aptamer Biosensor for the Detection of K562 Leukemia Cancer Cells

Graphene composites with hemin and gold nanoparticles show a better performance for hydrogen peroxide decomposition compared to that of the three components alone or duplex/hybrid complexes. Our previous studies showed that the morphology of the Au nanoparticles may greatly influence the catalytic activity of graphene‐family peroxidase mimics. Recently, we found that Au nanoflowers could grow in situ and form on the surface of hemin/RGO (reduced graphene oxide). The prickly morphology of this Au nanoflower brought a higher catalytic ability with enhanced kinetic parameters than traditional Au nanoparticles that showed a smooth surface. Therefore, based on this discovery, a smart electrochemical aptamer biosensor for K562 leukemia cancer cells was further presented with good performance in selectivity and sensitivity attributed to the excellent mimetic peroxidase catalytic activity of this newly synthesized Au nanoflower decorated graphene–hemin composite (H‐RGO‐Au NFs).     

间接竞争酶联适配体检测食品中土霉素

研究建立了一种间接竞争酶联适配体检测食品中土霉素（OTC）的分析方法。通过方阵滴定法和单因素实验优化了检测条件。在最佳实验条件下,方法的半抑制浓度（IC50）为6.3ng/mL,对OTC的检测线性范围为0.5~50ng/mL;与结构类似物有较低的交叉反应;对牛奶、奶粉、鸡肉、水产品和蜂蜜样品中土霉素的加标回收率为62.1%~102%,相对标准偏差（RSD）小于15%。将建立的方法用于实际样品检测,并与国标方法进行对比,两者获得较高的相关性（r2=0.979）。本方法可实现对实际样品中土霉素的快速、高灵敏和高通量检测。     

A Label‐Free Electrochemical Aptasensor for Thrombin Using a Single‐Wall Carbon Nanotube (SWCNT) Casted Glassy Carbon Electrode (GCE)

An electrochemical aptasensor with a thrombin binding aptamer (TBA) was developed using a single‐wall carbon nanotube (SWCNT) casted GCE. The TBA was immobilized on SWCNTs through π‐stacking without any special modification, resulting in helical wrapping to the surface. In the presence of thrombin, the TBA binds with thrombin and the TBA concentration on the SWCNT surface decreases. The remaining amount of TBA can be analyzed by an electrochemical method without any label, because the guanine bases of the nucleic acid are measurable by electrochemical methods. The electrochemical oxidation of guanine nucleotides was enhanced by electrocatalytic mediation using Ru(bpy)₃²⁺ for higher sensitivity and reduction of the overpotential for electrochemical detection.