Superparamagnetic photonic crystals with DNA probes for rapid visual detection of mercury.

A novel superparamagnetic photonic crystal DNA probe (Fe3O4@SiO2@amino@DNA SPC) was developed to enable rapid visual detection of Hg2+. This unique photonic crystal (PC) was synthesized by combining superparamagnetic nanospheres with DNA probes. The DNA probe, rich in thymine (T), detects mercury ions through base mismatch, resulting in the formation of T-Hg2+-T loop hairpin structures. With the binding of Hg2+ to the probe attached to superparamagnetic nanospheres, the PC structure assembled by these nanospheres, formed by the magnetic field, was changed. This change enhanced the reflection intensity; it could be quantified using a fiber optic spectrometer and was visible to the naked eye. The Fe3O4@SiO2@amino@DNA SPC, specific to Hg2+, exhibited a reflection peak at 679 nm, which intensified with increasing Hg2+ concentration. The reflection intensity increased by 132.58 a.u., and the PC color shifted from red to yellow as the Hg2+ concentration increased from 0.1 µg/L to 1 mg/L.

Cytosine-rich mismatched DNA aptamer combined with superparamagnetic photonic crystal sensing material for the specific visual detection of silver ions.

DNA aptamer superparamagnetic photonic crystals (DSPCs), enriched with a highly selective cytosine-rich mismatched single-stranded DNA aptamer (CRDA), were successfully employed in a novel visual detection strategy for the detection of silver ions (Ag+). The technologies of superparamagnetic colloidal nanospheres (SCNs), DNA aptamer, and photonic crystals were combined to fabricate DPSCs. The aptamer was immobilized via electrostatic adsorption with amino groups that were chemically introduced on the surface of the SCNs, forming D-NH-SCNs. The detection is achieved by forming an Ag+ complex (C-Ag+-C) between Ag+ and D-NH-SCN. The DSPCs assembled under a magnetic field by D-NH-SCNs effectively detected Ag+ in the range of 1 µg/L to 5 mg/L, corresponding to the critical concentration range for heavy metals in drinking water. During the detection, the DSPC exhibited a wavelength blueshift from 652.8 nm to 626.4 nm (26.4 nm), as well as changes in reflection intensity. Notably, when detecting Ag+, a change in DSPC color from orange to yellow was observed. In summary, the developed visual detection material facilitates direct Ag + sensing. In the future, different DNA aptamers will be modified further to detect various targets in the fields of medicine, environmental monitoring, and food safety.

Magnetic mesoporous nanospheres anchored with LyP-1 as an efficient pancreatic cancer probe.

Immobilization of a ligand that selectively interacts with cancer cells to nanomaterials can enhance their diagnostic and therapeutic efficiency. In this study, we firstly demonstrate the high expression of receptor for cyclic nine-amino acid peptide LyP-1 (Cys-Gly-Asn-Lys-Arg-Thr-Arg-Gly-Cys) in both mouse and human pancreatic cancer. Based on these findings, sub-50 nm multifunctional superparamagnetic mesoporous nanospheres with surface modified with LyP-1 are rationally designed. Theses nanospheres have a core of silica-protected magnetite nanoparticle and a shell of FITC-labeled mesoporous silica, and they are able to specifically recognize and conjugate with the pancreatic cancer cell in vitro, as verified by the combined techniques of fluorescent imaging and T2 weight magnetic resonance imaging. After systematic administration, these LyP-1 immobilized nanospheres are found to actively target to mouse orthotopic xenograft of pancreatic cancer, which opens up the door for applications in early probing and diagnosis of pancreatic cancer by the multimodal imaging.