Nanoparticle-Assisted Nuclear Relaxation-Based Detection of Oligonucleotides.

Nuclear relaxation-based techniques rely on the capability of paramagnetic center to affect the transverse relaxation time (T2) of the water protons. These changes are sensitive to the microenvironment of the paramagnetic center, which can be used to detect a variety of targets. In this work, we present an "on-off" oligonucleotide detection scheme in aqueous solutions, which uses gadolinium phthalocyanine (GdTcPc)-grafted silica nanoparticles as the paramagnetic centers. A probe oligonucleotide strand was conjugated to the GdTcPc to act as a recognition element. In the presence of the target oligonucleotide, which was complementary to the probe, an increase in the ΔT2 value, which was measured by subtracting the characteristic T2 value of the background solution from that of the sample using a benchtop relaxometer, was observed. The magnitude of this increase was proportional to the target oligonucleotide concentration. A linear range was obtained from 30 to 140 nM, with a detection limit of 15 nM. The developed nuclear relaxation-based detection scheme is shown to be a simple, fast, and selective method to detect oligonucleotide and could be useful in point-of-care diagnostic applications.