He Liyong,Shen Zhipeng,Wang Jiaqi,Zeng Jin,Wang Wenhai,Wu Huihui,Wang Qiqin,Gan Ning
The authors describe a microfluidic chip-based aptasensor platform combined with magnetic tripartite DNA structure-functionalized nanocomposites to achieve simultaneous determination of kanamycin (KANA), aflatoxin M1 (AFM1), and 17β-estradiol (E2) in milk. The two-duplex tripartite DNA nanostructure was first assembled on the surface of magnetic beads. When the aptamer on the probes recognized the specific target, the aptamer-target would be released into the supernatant. The pre-primer@circular DNA template structure initiates rolling circle amplification (RCA) by phi29 polymerase. After magnetic separation, the magnetic nanocomposites were added into a solution containing three different lengths of complementary strands to the RCA products. The number of complementary strands significantly decrease, and this can be quantitated by the microfluidic chip. Further, the employment of magnetic nanocomposites and microfluidic chip not only resolve the complex matrix interference, but also dramatically enhances the determination selectivity and sensitivity. This aptasensor allows for determination of KANA, AFM1, and E2 with limits of detection as low as 0.32 pg mL −1 , 0.95 pg mL −1 , and 6.8 pg mL −1 , respectively. This novel method exhibits the advantages of excellent stability and fast response time (< 3 min on microfluidic chip platform) for simultaneous determination of KANA, AFM1, and E2 in milk samples and ensures food safety.
Graphical abstract
A novel kind of electrochemical biocodes based on nanoscale metal organic framework (NMOF) was developed for simultaneous detection of multiple antibiotics such as kanamycin (KANA) and chloramphenicol (CAP). Herein, amine-functionalized NMOF (UiO-66-NH 2 ) was firstly employed as substrate to carry different metal ions (Pb 2+ or Cd 2+ ) respectively (M-NMOF). The adsorption capacities were 293.52 mg g −1 for Pb 2+ and 268.37 mg g −1 for Cd 2+ . Secondly, the M-NMOFs were respectively labeled with the complementary DNA strands of aptamers toward KANA and CAP to obtain two signal tags. Finally, both of the tags were conjugated with aptamers functionalized magnetic beads ( [email protected] /Apt2) to obtain the biocodes. Upon aptamers bound to targets (KANA and CAP) specifically, the corresponding M-NMOFs were released into supernatant after magnetic separation, which can be detected by square wave voltammetry (SWV). Results showed the high sensitivity with detection limits as low as 0.16 pM and 0.19 pM (S/N = 3) toward KANA and CAP respectively, which is 3 or 4 orders of magnitude lower than that of ELISA. Moreover, it exhibited excellent selectivity and more resistant to interference in food analysis. Furthermore, this NMOF based biocodes can be extended to other simultaneous detection system just by changing the aptamer and increasing the types of metal ions.
Wan Huang,Danyan Zhan,Yiming Xie,Xin Li,Guosong Lai
DNA walkers have been recognized as a type of powerful signal amplification tool for biosensors, but how to adopt a proper strategy to increase their amplification efficiency is still highly desirable. Herein we design a dual-catalytic hairpin assembly (CHA)-mediated strategy for the high-efficient formation of a tripedal Mg 2+ -dependent DNAzyme (MNAzyme)-DNA walker, and thus develop a novel proteinase-free dual-mode biosensing method for the kanamycin (Kana) antibiotic assay. The first CHA is initiated by a target-biorecognition reaction, which can produce the DNA walker and also induce the target recycling. The second CHA is initiated by a special base sequence designed as a one-half substrate of the MNAzyme. Upon the first CHA-triggered DNA walking at a magnetic bead (MB) track, this “pseudo-target” sequence can be released to induce another CHA-cycle for the formation of the same DNA walker. Meanwhile, the other one-half substrate strand exposed on the MB surface will trigger the quantitative hybridization chain reaction (HCR)-assembly of a G-quadruplex DNAzyme (G-DNAzyme)-enriched double-stranded DNA polymer. So the enzymatic reaction of G-DNAzymes enabled the convenient colorimetric and photoelectrochemical dual-mode signal transduction of the method. Due to the dual-CHA facilitation to the tripedal and three-dimensional DNA walking and synergetic signal amplification of HCR, this method exhibits very low detection limits of 9.4 and 0.55 fg mL −1 , respectively. In combination with its wide linear range, automated manipulation, and excellent selectivity , repeatability and reliability, the proposed method is expected to be used for the convenient semiquantitative screening and accurate determination of possible antibiotic residues in complicated matrices.
危险品化学品经营许可证（带存储）