Metal-organic framework integrated hydrogel bioreactor for smart detection of metal ions.

Bioreactors with environment responsiveness for smart detection has attracted widespread interest. Bioreactors that operate in liquid have excellent reaction speed and sensitivity, and those that operate at a solid interface have unique portability and stability. However, bioreactors that can simultaneously take advantage of both properties are still limited. Here, we developed a metal-organic framework (MOF) integrated hydrogel bioreactor that can accommodate both solid and liquid properties by using a hydrogel as a quasi-liquid medium. To enhance the stability and intelligence of the hydrogel bioreactor, we have opted for the utilization of europium metal-organic framework (Eu-MOF) as the optical output to withstand long-term storage challenges, and DNA as the highly programmable substance for intelligent target response. On this basis, smart detection of metal ions and biological micro-molecules have been achieved. Notably, this quasi-liquid hydrogel bioreactor has effectively tackled the intrinsic issues of inadequate dispersion stability of Eu-MOF in liquid systems and poor stability of DNA against environmental interference. Moreover, this MOF integrated hydrogel bioreactor has been applied to the construction of a portable hydrogel bioreactor, which enables platform-free and arrayed target detection via a smartphone, providing a new perspective for further promoting the application of quasi-liquid hydrogel bioreactors and intelligent nanobiological sensors.

(Eu-MOF)-derived Smart luminescent sensing for Ultrasensitive on-site detection of MiR-892b.

MicroRNAs (miRNAs) are important biomacromolecules used as biomarkers for the diagnosis of several diseases. However, current detection strategies are limited by expensive equipment and complicated procedures. Here, we develop a portable, sensitive, and stable (Eu-MOF)-based sensing platform to detect miRNA via smartphone. The Eu-MOF absorbs the carboxyfluorescein (FAM)-tagged probe DNA (pDNA) to generate hybrid pDNA@Eu-MOF, which can efficiently quench the fluorescence of FAM through a photoinduced electron transfer (PET) process. When integrated with a smartphone, the nonemissive pDNA@ Eu-MOF hybrid could be utilized as a portable and sensitive platform to sense miRNA (miR-892b) with a detection limit of 0.32 pM, which could be even distinguished by the naked eye. Moreover, this system demonstrates high selectivity for identifying miRNA family members with single-base mismatches. Furthermore, the expression levels of miRNA in cancer cell samples could be analyzed accurately. Therefore, the proposed method offers a promising guideline for the design of MOF-based sensing strategies and expands their potential applications for diagnostic purposes.

Accelerated Fenton degradation of azo dye wastewater via a novel Z-scheme CoFeN-g-C3N4 heterojunction photocatalyst with excellent charge transfer under visible light irradiation.

A novel Z-scheme heterostructure photocatalyst, CoFeN-g-C3N4 (CFN-CN), was prepared by a simple strategy, and its heterostructure and a photo-Fenton system were used to synergistically catalyze the degradation of azo dyes. The experimental results showed that the CFN-CN1 heterojunction exhibited superior photocatalytic degradation performance, and the degradation rate of Methyl Orange (MO) reached 96.8% in 40 min. The degradation rate constants were 11.8 and 2.81 times those of CN and CFN, respectively. CFN-CN1 also shows excellent catalytic degradation performance for other azo dyes (Congo Red (CR), Acid Orange 7 (AO7), Mordant Black 17 (MB17) and Acid Red B (ARB)), and the degradation efficiencies all exceeded 90%. Furthermore, the addition of inorganic anions (Cl-, HCO3- and SO42-) affects the degradation of azo dyes, especially HCO3- which significantly promotes the degradation of MO. The radical trapping experiments and EPR results indicated that superoxide radicals (˙O2-) and hydroxyl radicals (˙OH) were the main active species. The above research reveals that the CFN-CN heterojunction synergistic photo-Fenton system may provide new hints for the degradation and removal of azo dyes from wastewater.

The Piezo-Fenton synergistic effect of ferroelectric single-crystal BaTiO3 nanoparticles for high-efficiency catalytic pollutant degradation in aqueous solution.

Nano-ferroelectric materials have excellent piezoelectric performance and can degrade organic dye by ultrasonic vibration in an aqueous solution. Here, BaTiO3 (BT) nanoparticles were prepared by a sol-gel/hydrothermal method and further applied in dye degradation in wastewater. BT nanoparticles exhibited excellent catalytic performance for organic dye molecule degradation through the piezo-Fenton synergistic effect. It was found that both the degradation efficiency and reaction rate were boosted by the increase of the molecular weight of organic dyes. The degradation efficiency toward different organic dyes exhibited a trend of CR > ABK > TH > RhB > MB > MO. For example, a high piezo-Fenton-catalytic degradation ratio of 82.8% at 5 min and 0.337 min-1 rate constant were achieved for the CR dye solution (10 mg L-1), which were 3.2 and 6.4 times the corresponding values of piezo-catalytic only degradation. These results mainly originate from the intrinsic properties of BT nanoparticles that can enhance the separation of charge and promote the formation of hydrogen peroxide (H2O2) and hydroxyl radicals (·OH) under ultrasonic vibration. Furthermore, the reaction of Fe(II) with H2O2 can further enhance the formation of ·OH, which can accelerate the degradation of organic dyes. These results indicate that the piezo-Fenton synergistic effect may provide a new clue for the development of the wastewater treatment field under mechanical vibration.

Smartphone-Based Pure DNAzyme Hydrogel Platform for Visible and Portable Colorimetric Detection of Cell-Free DNA.

Cell-free DNA (cfDNA), as a tumor marker, is of great importance for the diagnosis of cancer and targeted therapy. However, the need for huge analytical instruments for cfDNA analysis has restricted its practical applications, especially in rural areas and third-world countries. Herein, a portable and visual smartphone-based DNAzyme hydrogel platform is developed for cfDNA detection. The target cfDNA triggers rolling circle amplification to produce a G-quadruplex-comprised DNA hydrogel with an horseradish peroxidase (HRP)-like catalytic function, which further catalyzes the chromogenic substrate to generate a visible output signal. Notably, the naked-eye detection of cfDNA can be realized by the macroscale visibility and catalytic ability of the DNA hydrogel. The linear range of the DNAzyme hydrogel platform for cfDNA detection is 0.1 pM-1500 nM with a detection limit of 0.042 pM. Moreover, this platform is exploited for the detection of cfDNA in spiked human serum with favorable sensitivity and recovery. Therefore, the DNAzyme hydrogel platform provides highly promising potential for testing other nucleic acid biomarkers.