The single function and weak catalytic activity of nonprecious metal nanozymes distinctly hinder their practical applications, so it is intriguing to develop multifunctional nanozymes via a facile and green route. Here, for the first time, “bottom–up” strategies were used to realize the efficient synthesis of MnO2 quantum dots (QDs) with simple operation and mild reaction conditions based on proteins, avoiding the operation complexity of the traditional “up–down” approach. More interestingly, MnO2 QDs exhibit extraordinarily outstanding catechol oxidase-like activity. QD nanozymes can catalyze the oxidation of dopamine (DA) into DA quinone in just 2 min, and then DA quinone polymerizes to form PDA in more than 10 min at 37 °C over a broad pH range (above pH 7.4). Based on the catechol oxidase-like activity and the interaction between QDs with a DA quinone-induced passivation effect, a “turn-on” fluorescence sensor based on two sequential recognitions for DA with self-signal output is developed without using the commonly used chromogenic reactions. The dual recognition provides the sensor with extremely good selectivity, which removes the interference from common reducible substances and metal ions. The detection limit can reach 0.038 μM, and the sensor has good specificity and a short detection time (just 2 min) under mild conditions. This offers a flexible guide for rational design and fabrication of FL turn-on biosensors for redox-active dopamine and enriches our understanding of QD nanozymes in bioanalytical fields.

Developing multifunctional nanozyme based biosensor with simple operation and high reliability is of vital interests for multiplex detection. Here, wool-ball-like copper sulfide (WBLCS) was obtained facilely using an amphiphilic protein....

Strenuous efforts have been made to develop nanozymes for achieving the performance of natural enzymes, but the fabrication of high-performance and biocompatible nanozymes via facile and versatile approaches has always been a great challenge.

Although many studies have focused on the role of individual biomolecules or metal ions in the crystallization behavior of sodium urate, the regulatory effects of multiple molecular species still remain mysterious. The synergistic cooperation of biomolecules and metal ions may contribute to unprecedented regulatory effects. Here, the cooperative effect of arginine-rich peptides (APs) and copper ions on the phase behavior, crystallization kinetics, and size/morphology of urate crystals was first investigated. Compared with the individual copper ion and AP, the nucleation induction time of sodium urate is prolonged dramatically (about 48 h), and the nucleation rate of sodium urate is reduced efficiently in a saturated solution due to the synergistic effect of Cu2+ and AP in stabilizing amorphous sodium urate (ASU). The length of sodium urate monohydrate crystals decreases obviously under the synergistic effect of Cu2+ and AP. The comparative experiments of common transition metal cations show that only copper ions can cooperate with AP, which may be due to the strong coordination effect between copper ions with urate and AP. Further studies show that the synergistic effect of copper ions and APs with different chain lengths on the crystallization behavior of sodium urate is significantly different. Both the guanidine functional groups and the length of peptide chains simultaneously determine the synergistic inhibition effect of polypeptides and Cu2+. This work highlights the synergistic inhibition effect of metal ions and cationic peptides on the crystallization of sodium urate, which enriches the understanding of the regulating mechanism of biological mineral crystallization using the synergy of multispecies and offers a new strategy for designing efficient inhibitors for sodium urate crystallization in gout stone diseases.

Nanomaterial-based artificial enzymes (nanozymes) have great potential for boosting their intrinsic activities to narrow the gaps against natural enzymes. Different from natural enzymes, nanozymes usually cannot work efficiently under physiological pH, which limits their application in environmental and biological fields. Here, we proposed that the originally futile tetrakis (4carboxyphenyl) iron porphyrin (FeTCPP) compounds in the Fe II -TCPP-Au nanoparticle (Fe II -TCPP-AuNP) hybrid are functionalized to serve as critical active sites involved in cytochrome P450 to greatly boost the oxidase-mimicking activity by an Al 3+ cofactor at neutral pH. The microenvironment around FeTCPP can be chemically optimized to provoke the oxidase-mimicking activity with 3,3′,5,5′-tetramethylbenzidine (TMB) as a substrate with the help of Al 3+ . The activity-provoking ability of the system is tunable by changing the concentrations of Al 3+ , the strong ligand F − , and temperature. Based on this, the selective and sensitive colorimetric sensor of Al 3+ based on nanozymes was first developed. The novelty of the present work is not only a new means to develop iron porphyrin nanozymes with superior oxidase-mimicking activity at neutral pH but is also the first example that hard acid Al 3+ can serve as a robust and efficient cofactor to synergize the catalytic performance of nanozymes. Therefore, this study provides some enlightenment about the integration of artificial cofactors in biomimetic chemistry and expands the application of nanozymes in environmental fields.