Laccase-mimicking Mn–Cu hybrid nanoflowers for paper-based visual detection of phenolic neurotransmitters and rapid degradation of dyes

Abstract

Background Laccase-based biosensors are efficient for detecting phenolic compounds. However, the instability and high cost of laccases have hindered their practical utilization. Results In this study, we developed hierarchical manganese dioxide–copper phosphate hybrid nanoflowers (H–Mn–Cu NFs) as excellent laccase-mimicking nanozymes. To synthesize the H–Mn–Cu NFs, manganese dioxide nanoflowers (MnO2 NFs) were first synthesized by rapidly reducing potassium permanganate using citric acid. The MnO2 NFs were then functionalized with amine groups, followed by incubation with copper sulfate for three days at room temperature to drive the coordination interaction between the amine moieties and copper ions and to induce anisotropic growth of the petals composed of copper phosphate crystals, consequently yielding H–Mn–Cu NFs. Compared with those of free laccase, at the same mass concentration, H–Mn–Cu NFs exhibited lower Km (~ 85%) and considerably higher Vmax (~ 400%), as well as significantly enhanced stability in the ranges of pH, temperature, ionic strength, and incubation periods evaluated. H–Mn–Cu NFs also catalyzed the decolorization of diverse dyes considerably faster than the free laccase. Based on these advantageous features, a paper microfluidic device incorporating H–Mn–Cu NFs was constructed for the convenient visual detection of phenolic neurotransmitters, including dopamine and epinephrine. The device enabled rapid and sensitive quantification of target neurotransmitters using an image acquired using a smartphone. Conclusions These results clearly show that H–Mn–Cu NFs could be potential candidates to replace natural laccases for a wide range of applications in biosensing, environmental protection, and biotechnology. Graphical Abstract

Biodegradation of Aflatoxin B1 in Peanut Oil by an Amphipathic Laccase–Inorganic Hybrid Nanoflower

“…Laccase is a polyphenol oxidase that can oxidize a wide range of substrates while reducing dioxygen to water and has been considered as a green biological tool for the degradation of various phenolic and non-phenolic contaminants. − Previous studies have revealed that laccase can catalyze the oxidation of AFB 1 to aflatoxin Q 1 (AFQ 1 ) in aqueous solution. , The toxicological analysis illustrated that AFQ 1 was almost non-toxic to human liver cells . However, the detoxification efficiency for non-phenolic compounds is poor as a result of the low redox potential (0.5–0.8 V) of laccase .…”

Genome of the epiphytic bacterium Achromobacter denitrificans strain EPI24, isolated from a macroalga located in the Colombian Caribbean

“…However, the inappropriate disposal of wastewater is a big challenge that disturbs all aquatic environments in the whole world. Wastewater containing phenolic compounds affects humans and other organisms for their high toxicity [ 1 , 2 ].…”

Laccase Immobilization on Copper-Magnetic Nanoparticles for Efficient Bisphenol Degradation

“…Compared to other systems, the Cu metals-based encapsulation of laccases via metal-protein hybrids is beneficial to retain better residual activity due to the presence of Cu as an active center in laccase [ 16 , 23 , 32 ]. In addition, Cu-based hybrids also exhibit laccase-mimicking properties and are helpful in the degradation of phenolics [ 33 , 34 ]. However, the Cu-containing magnetic NPs have never been used to immobilize laccase covalently.…”