PMC:4996384 / 19259-21594 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/4996384","sourcedb":"PMC","sourceid":"4996384","source_url":"https://www.ncbi.nlm.nih.gov/pmc/4996384","text":"3.4. Adenosine Detection with Split-APT4 Sequence\nThe case of the biosensor grafted with Split-APT4 sequence differs from the previous one with Split-APT8 since no specific signal (signal OFF) is observed without adenosine. We injected a series of different adenosine solutions (from 1 nM to 1 μM) in presence of 200 pM of AuNPs in the same conditions than the injection of AuNPs alone. The injections of AuNPs with or without adenosine were longer and stopped after 40 min due to the reduced SPR signal observed compared to the Split-APT8 probes. The stabilization of the complex formed by the target and the split-aptamers leads to a specific signal (signal ON) with an increased SPRi reflectivity shift. This increased signal is dependent of the concentration of adenosine (Figure 5) with a limit of detection (LOD) of 50 nM. This LOD is three order of magnitude lower than the one obtained with Split-APT8 biosensor. Two main reasons may explain this huge effect. First of all, it is known that signal OFF—signal ON biosensors are generally more efficient than the ones with an increased signal ON in presence of the targets. This is principally due to the fact that it is easier to detect an increased signal form the background noise than from an important reference signal. However, this requires a limited non-specific signal to reduce the noise which is precisely the case with our grafting procedure. Furthermore, the sequence of the split‑aptamers may also explain a large part of the LOD improvement. Since the number of hybridization bases in the stem is reduced for Split-APT4 than for Split-APT8 the stabilizing effect of the target on the complex formation is relatively more important. Finally, the selectivity of the biosensor assay was also validated by an injection of 1 μM of guanosine (G curve) whose reflectivity shift is weak and comparable to the injection of AuNPs alone.\nFigure 5 A range of adenosine (A) concentrations have been incubated in presence of Split-APT coated gold nanoparticles. Higher SPRi signals on Split-APT4 spots are observed upon increased concentrations allowing a detection limit of 50 nM. The injection of 1 μM of guanosine (G) does not significantly modify the SPRi signal compared to the injection of gold nanoparticles (AuNPs) alone implying a good selectivity of the biosensor.\n\n4","divisions":[{"label":"Title","span":{"begin":0,"end":49}},{"label":"Figure caption","span":{"begin":1898,"end":2334}}],"tracks":[]}