Colorable Zeolitic Imidazolate Frameworks for Colorimetric Detection of Biomolecules

Abstract

We report a series of colorable zeolitic imidazolate framework (ZIF)-based nanomaterials prepared by encapsulating starches (amylopectin, dextrin, or amylose) or tannic acid in the frameworks of ZIFs and first applied them in colorimetric assay of microRNA/DNA by adding I2/KI or FeCl3 solutions as chromogenic reagents. We found that iodine molecules can lead to rapid degradation of the ZIF-8 framework, while ZIF-90 remains stable. Therefore, ZIF-90 was selected for encapsulating the starches or tannic acid, and then assembled with polyethylenimine (PEI) and aptamers of microRNA/DNA. After interacting with the target microRNA/DNA, the aptamers (Ap) move away from the surface of the prepared Ap–starch@ZIF-90 or Ap–tan@ZIF-90, and the I2/KI or FeCl3 solution is added into the system to interact the starches (amylopectin, dextrin, or amylose) or tannic acid to generate different colors. According to the absorbance spectra, good linear correlations between the logarithm of absorbance intensity and the concentration of microRNA (1–180 nM) can be observed, and the naked eye can distinguish the change from ∼60 to ∼180 nM with a concentration gradient of 20 nM. A similar colorimetric assay ability for pathogenic bacteria can also be realized by detecting the gene fragments IS200 and eaeA. The detection limits can be potentially optimized by changing the amount of adsorbed PEI and aptamers on the surface of Ap–starch@ZIF-90 (or Ap–tan@ZIF-90) nanoparticles. This method could be a promising alternative for simple and cost-effective assay of microRNA/DNA.

Zeolitic Imidazolate Framework-90 Nanoparticles as Nanozymes to Mimic Organophosphorus Hydrolase

“…As shown in Figure 1d, we can observe the precise peak of the CO stretching vibration (1689 cm −1 ) belonging to 2-ICA and the peak of the CN and CC vibrations (1616 cm −1 ). 22 Simultaneously, we also observed blue-shifted CO stretching vibration peaks in ZIF-90. The blue shift is attributed to the self-assembly of zinc and imidazolate.…”

“…Energy-dispersive spectrometry (EDS) also shows the successful combination of zinc and imidazolate (Figure S1). As shown in Figure d, we can observe the precise peak of the CO stretching vibration (1689 cm –1 ) belonging to 2-ICA and the peak of the CN and CC vibrations (1616 cm –1 ) . Simultaneously, we also observed blue-shifted CO stretching vibration peaks in ZIF-90.…”

“…The blue shift is attributed to the self-assembly of zinc and imidazolate. 22 Besides, the band at 793 cm −1 in ZIF-90 might be attributed to the bending of the imidazole ring. 23 When zinc was combined with imidazole, CN was converted to C−N accompanied by Zn−N bond generation, so the band at 1616 cm −1 disappeared in ZIF-90, and the signals at 954 and 1167 cm −1 in ZIF-90 were assigned to C−N vibration.…”

Visualization of gaseous iodine adsorption on single zeolitic imidazolate framework-90 particles

“…2a , Supplementary Figs. 1 and 2 ) 13 . Powder XRD data confirms that the obtained patterns match the simulated one for ZIF-90, demonstrating the good purity of the sample (Supplementary Fig.…”

“…The ZIF-90 particles are prepared by a simple one-pot method 13 . Briefly, 0.02 g polyvinylpyrrolidone and 0.12 g imidazole-2-carboxaldehyde are dissolved into 9 mL of deionized water, which is stirred for 3 min at 25 °C.…”