We have developed a robust method for the visual detection of heavy metal ions (such as Hg(2+) and Pb(2+)) by using aptamer-functionalized colloidal photonic crystal hydrogel (CPCH) films. The CPCHs were derived from a colloidal crystal array of monodisperse silica nanoparticles, which were polymerized within the polyacrylamide hydrogel. The heavy metal ion-responsive aptamers were then cross-linked in the hydrogel network. During detection, the specific binding of heavy metal ions and cross-linked single-stranded aptamers in the hydrogel network caused the hydrogel to shrink, which was detected as a corresponding blue shift in the Bragg diffraction peak position of the CPCHs. The shift value could be used to estimate, quantitatively, the amount of the target ion. It was demonstrated that our CPCH aptasensor could screen a wide concentration range of heavy metal ions with high selectivity and reversibility. In addition, these aptasensors could be rehydrated from dried gels for storage and aptamer protection. It is anticipated that our technology may also be used in the screening of a broad range of metal ions in food, drugs and the environment.

A suspension array with microcarriers encoded by both structural color and shape was developed. The microcarriers with high stability, large capacity, low background noise and simplicity for practical application were the hydrogel colloidal crystals fabricated by photolithography. The aptamer based multiplex array, as an example, was constructed using the encoded microcarriers as the carrier of suspension array. The ssDNA functionalized hydrogel microcarriers are achieved by copolymerization. Based on the high selectivity recognition of aptamer to its target, a novel hydrogel microcarrier suspension array platform, as a potential tool for the efficient quantification of biomolecules, is established.

The interaction between naproxen and yeast DNA was studied using fluorescence spectrometry and ultra-violet (UV) spectrometry. The addition of yeast dsDNA to naproxen solution resulted in a strong fluorescence quenching. Both the Stern-Volmer and the Scatchard plots of the fluorescence quenching showed a curve with two slopes and a threshold DNA concentration of about 100 µmol•L -1 . The interaction between naproxen and the dsDNA was found to be a groove binding mode by UV spectra, the influence of ion strength and Iquenching effect. This mode was independent on DNA concentration. However, the increase in DNA concentration changed the binding constant K of naproxen to yeast dsDNA and the number of binding sites in DNA base pairs (n).

We synthesized a fluorescent sensor for detection of pyrophosphate (PPi) and alkaline phosphatase (ALP) based on copper/silver nanoclusters (DNA-Cu/Ag NCs) with single-stranded DNA as template. The whole synthesis process was only 30 min. When PPi was added to the reaction liquid for the preparation of DNA-Cu/Ag NCs, the fluorescence of DNA-Cu/Ag NCs would be quenched due to the strong complexation between PPi and Cu 2+. As ALP could catalyze the hydrolysis of PPi to Pi, the complexation between Cu 2+ and PPi would be destroyed and the fluorescence intensity would increase. Based on this principle, we developed a new method for detecting PPi and ALP with a detection limit of 136.7 nmol/L and 0.01 U/mL, respectively. Finally, by detecting the PPi in human serum, the diagnostic ability and practical application of the method were verified.