The overuse of antibiotics can lead to the emergence of drug resistance, preventing many common diseases from being effectively treated. Therefore, based on the special composite platform of P1/graphene oxide (GO) and DNA triple helix, a programmable DNA nanoswitch for the quantitative detection of tetracycline (TC) was designed. The introduction of GO as a quenching agent can effectively reduce the background fluorescence; stabilizing the trigger strand with a triplex structure minimizes errors. It is worth mentioning that the designed model has been verified and analyzed by both computer simulation and biological experiments. NUPACK predicts the combined mode and yield of each strand, while visual DSD flexibly predicts the changes in components over time during the reaction. The feasibility analysis preliminarily confirmed the realizability of the designed model, and the optimal reaction conditions were obtained through optimization, which laid the foundation for the subsequent quantitative detection of TC, while the selective experiments in different systems fully demonstrated that the model had excellent specificity.
The effect of the moving speed between a permanent magnet and a superconductor on the
levitation force of single-domain YBCO bulk has been studied at liquid nitrogen temperature. It is
found that the levitation force is much different with different moving speed, the maximum levitation
force and the stiffness of the force-distance curve are increasing first and then decreasing with the
increasing of the moving speed and, there is a reasonable speed to get the maximum levitation force. It
is also found that the maximum attractive force is decreasing with the increasing of the moving speed.
Background:
Molecular logic gate always used fluorescent dyes to realize fluorescence signal. The labeling of the fluorophore is relatively expensive, low yield and singly labeled impuritiesaffects the affinity between the target and the aptamer. Label-free fluorescent aptamer biosensor strategy has attracted widespread interest due to lower cost and simple.
Objective:
Herein, we have designed a AND logic gate fluorescent aptasensor for detecting carbohydrate antigen 15-3(CA15-3) based on label-free fluorescence signal output.
Materials and Methods:
A hairpin DNA probe consists of CA15-3 aptamer and partly anti-CA15-3 aptamer sequences as a long stem and G-rich sequences of the middle ring as a quadruplex-forming oligomer. G-rich sequences can fold into a quadruplex by K+, and then G-quadruplex interacts specifically with N-methylmesoporphyrin IX(NMM), leading to a dramatic increase in fluorescence of NMM. With CA15-3 and NMM as the two inputs, the fluorescence intensity of the NMM is the output signal. Lacking of CA15-3 or NMM, there is no significant fluorescence enhancing, and the output of the signal is “0”. The fluorescence signal was dramatically increasing and the output of the signal is “1” only when CA15-3 protein and NMM were added at the same time.
Results:
This biosensor strategy possessed selectivity, high sensitivity for detecting CA15-3 protein from 10 to 500 U mL-1 and the detection limit was 10 U mL-1, and also showed good reproducibility in spiked human serum.
Conclusion:
In summary, the proposed AND logic gate fluorescent aptasensor could specifically detect CA15-3.
Due to the limitation of technology, electronic computing is approaching the limit of technology, and new computing tools need to be developed. Here, we build a three input cascade logic...
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