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Nanozyme, with enzyme-mimicking activity and excellent stability, has attracted extensive attention. However, some inherent disadvantages, including poor dispersion, low selectivity, and insufficient peroxidase-like activity, still limit its further development. Therefore, an innovative bioconjugation of a nanozyme and natural enzyme was conducted. In the presence of graphene oxide (GO), histidine magnetic nanoparticles (H-Fe3O4) were first synthesized by a solvothermal method. The GO-supported H-Fe3O4 (GO@H-Fe3O4) exhibited superior dispersity and biocompatibility because GO was the carrier and possessed outstanding peroxidase-like activity because of the introduction of histidine. Furthermore, the mechanism of the peroxidase-like activity of GO@H-Fe3O4 was the generation of •OH. Uric acid oxidase (UAO) was selected as the model natural enzyme and covalently linked to GO@H-Fe3O4 with hydrophilic poly(ethylene glycol) as a linker. UAO could specifically catalyze the oxidation of uric acid (UA) to generate H2O2, and subsequently, the newly produced H2O2 oxidized the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue ox-TMB under the catalysis of GO@H-Fe3O4. Based on the above cascade reaction, the GO@H-Fe3O4-linked UAO (GHFU) and GO@H-Fe3O4-linked ChOx (GHFC) were used for the detection of UA in serum samples and cholesterol (CS) in milk, respectively. The method based on GHFU exhibited a wide detection range (5–800 μM) and a low detection limit (1.5 μM) for UA, and the method based on GHFC exhibited a wide detection range (4–400 μM) and a low detection limit (1.13 μM) for CS. These results demonstrated that the proposed strategy had great potential in the field of clinical detection and food safety. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers (MIPs) can exhibit antibody-level affinity for target molecules. However, the nonspecific adsorption of non-imprinted regions for non-target molecules limits the application range of MIPs. Herein, we fabricated PEGylated boronate-affinity-oriented ellagic acid-imprinting magnetic nanoparticles (PBEMN), which first integrated boronate-affinity-oriented surface imprinting and sequential PEGylation for small molecule-imprinted MIPs. The resultant PBEMN possess higher adsorption capacity and faster adsorption rate for template ellagic acid (EA) molecules than the non-PEGylated control. To prove the excellent performance, the PBEMN were linked with hydrophilic boronic acid-modified/fluorescein isothiocyanate-loaded graphene oxide (BFGO), because BFGO could selectively label cis-diol-containing substances by boronate-affinity and output ultrasensitive fluorescent signals. Based on a dual boronate-affinity synergy, the PBEMN first selectively captured EA molecules by boronate-affinity-oriented molecular imprinted recognition, and then the EA molecules were further labeled with BFGO through boronate-affinity. The PBEMN linked BFGO (PBPF) strategy provided ultrahigh sensitivity for EA molecules with a limit of detection of 39.1 fg mL−1, resulting from the low nonspecific adsorption of PBEMN and the ultrasensitive fluorescence signal of BFGO. Lastly, the PBPF strategy was successfully employed in the determination of EA concentration in a spiked beverage sample with recovery and relative standard deviation in the range of 96.5 to 104.2% and 3.8 to 5.1%, respectively. This work demonstrates that the integration of boronate-affinity-oriented surface imprinting and sequential PEGylation may be a universal tool for improving the performance of MIPs. [ABSTRACT FROM AUTHOR]

• Hedgehog-inspired magnetic nanoparticles (HMN) was fabricated for DNA extraction. • HMN possessed a high-surface-area due to the distinct burr-like structure of hedgehog. • HMN-based solid-phase microextraction (MSPE) could capture DNA of pathogenic bacteria. • HMN-based MSPE linked qPCR was successfully used in the detection of pathogenic bacteria. Efficient separation of deoxyribonucleic acid (DNA) through magnetic nanoparticles (MN) is a widely used biotechnology. Hedgehog-inspired MNs (HMN) possess a high-surface-area due to the distinct burr-like structure of hedgehog, but there is no report about the usage of HMN for DNA extraction. Herein, to improve the selection of MN and illustrate the performance of HMN for DNA separation, HMN and silica-coated Fe 3 O 4 nanoparticles (Fe 3 O 4 @SiO 2) were fabricated and compared for the high-efficient separation of pathogenic bacteria of DNA. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are typical Gram-negative and Gram-positive bacteria and are selected as model pathogenic bacteria. To enhance the extraction efficiency of two kinds of MNs, various parameters, including pretreatment, lysis, binding and elution conditions, have been optimized in detail. In most separation experiments, the DNA yield of HMN was higher than that of Fe 3 O 4 @SiO 2. Therefore, a HMN-based magnetic solid-phase microextraction (MSPE) and quantitative real-time PCR (qPCR) were integrated and used to detect pathogenic bacteria in real samples. Interestingly, the HMN-based MSPE combined qPCR strategy exhibited high sensitivity with a limit of detection of 2.0 × 101 CFU mL−1 for E. coli and 4.0 × 101 CFU mL−1 for S. aureus in orange juice, and 2.8 × 102 CFU mL−1 for E. coli and 1.1 × 102 CFU mL−1 for S. aureus in milk, respectively. The performance of the proposed strategy was significantly better than that of commercial kit. This work could prove that the novel HMN could be applicable for the efficient separation of DNA from complex biological samples. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers (MIPs) are artificial chemical receptors, and can recognize template molecules with a high selectivity and affinity. As "antibody mimics", MIPs have been widely studied in various fields. However, the general applicability of MIPs is limited by the type of functional monomers. Herein, we developed caffeic acid (CA, a natural polyphenol) as novel a functional monomer. An innovative poly(caffeic acid)-coated molecularly imprinted magnetic nanoparticles (PCA-MIMN) with transferrin (TRF) as a model glycoprotein template was fabricated by autoxidation of CA with hexamethylenediamine (HMDA) in an aerobic environment as imprinted layer. The successful fabrication of PCA-MIMN was proved in detail by diversified characterization. The PCA-MIMN exhibited not only outstanding binding affinity and specificity for target glycoprotein, but also excellent hydrophilicity due to the externally generous hydrophilic groups. To evaluate the preeminent performance, the PCA-MIMN was linked with pH-triggered allochroic-graphene oxide (AGO), which was used for determination of TRF in real samples. The proposed PCA-MIMN linked AGO strategy exhibited ultrahigh sensitivity with limit of detection of 0.38 pg mL−1 for TRF. Finally, the proposed strategy was successfully applied in determination of TRF in spiked human serum sample with recovery and relative standard deviation in the range of 97.2%–103.9% and 4.6%–5.8%, respectively. This work demonstrates that the "autoxidation of CA with HMDA" may be a universal tool for synthesis of highly specific MIPs, and the type of functional monomers will increase exponentially due to the presence of numerous polyphenols in nature. [Display omitted] • Plant-derived polyphenol, caffeic acid (CA), was developed as novel functional monomer. • A novel imprinted material, named as PCA-MIMN, was fabricated by autoxidation of CA with diamine. • PCA-MIMN had high adsorption capacity for target glycoprotein and excellent hydrophilicity. • PCA-MIMN linked allochroic-graphene oxide was successfully used for detection of transferrin. [ABSTRACT FROM AUTHOR]

[Display omitted] • Boronate affinity controllable-oriented imprinting magnetic nanoparticle (BCEMN) is obtained. • Boronic acid modified/polyethylene glycol coated allochroic-graphene oxide (BPAO) is prepared. • BCEMN linked BPAO strategy is used for rapid and ultrasensitive detection of ellagic acid. • Compared with HPLC, this proposed method is more sensitive, lower cost, and less time-consuming. Herein, we integrate boronate-affinity controllable-oriented ellagic acid-imprinted magnetic nanoparticles (BCEMN) and boronic acid-modified / polyethylene glycol-coated allochroic-graphene oxide (BPAO) for specific and ultrasensitive detection of ellagic acid (EA). The novel detection method depends on a dual boronate-affinity sandwich strategy. The symmetric EA is first specifically captured by the BCEMN based on the boronate-affinity-related molecularly imprinted recognition, and then labeled with BPAO due to the boronate-affinity recognition. The BPAO, which is functionalized with 2,6-difluoro-4-formyl-phenylboronic acid, loaded with a large amount of pH-sensitive thymol phthalide and coated with hydrophilic polyethylene glycol, can specifically recognize the cis -diol of EA at physiological condition (pH 7.4) and perform signal amplification and readout through pH-triggered allochroism. Furthermore, the signal readout of allochroism is linear with the logarithm of EA concentration over the range between 0.02 ng mL−1 to 104 ng mL−1 with a good correlation coefficient (R2 = 0.993), and the limit of detection (LOD) is 2.96 pg mL−1. Finally, the BCEMN linked BPAO (BCBP) strategy has also been successfully applied in the detection of EA concentration in spiked strawberry sample with recovery and relative standard deviation in the range of 84.9%–110.2% and 3.9%–6.1%, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Boronic acid-modified / fluorescein isothiocyanate-loaded graphene oxide (BFGO) is prepared. • Boronate-affinity-oriented surface imprinting magnetic nanoparticles (BSIMN) is fabricated. • BSIMN and BFGO are integrated for fast, sensitive and specific detection of glycoprotein. • Compared with ELISA, the innovative method is more sensitive, lower cost and less time-consuming. Here, integration of boronic acid-modified / fluorescein isothiocyanate-loaded graphene oxide (BFGO) and boronate-affinity-oriented surface imprinting magnetic nanoparticles (BSIMN) was proposed for ultrasensitive and specific detection of glycoprotein. The innovative BFGO, which was modified with boronic acid and loaded with generous fluorescein isothiocyanate, could selectively label glycoprotein by boronate-affinity and perform fluorescence signal amplification and output. In addition, the protein-free BFGO was fabricated entirely from chemicals and had fine hydrophilicity due to the modification of hydrophilic polyethylene glycol. Furthermore, the BSIMN possessed specific selectivity toward template glycoprotein because of boronate-affinity-related molecularly imprinted recognition. BSIMN linked BFGO (BSBF) for glycoprotein detection depended on a dual boronate-affinity synergy, in which glycoprotein was first selectivity captured by the BSIMN and then labeled with BFGO. The proposed BSBF strategy exhibited universal applicability, and provided ultrahigh sensitivity with limit of detection of 23 fg mL−1 and 1.2 fg mL−1 for horseradish peroxidase and carcinoembryonic antigen, respectively. Finally, the BSBF strategy was successfully used in detection of glycoprotein in spiked serum sample with recovery between 93.9 % and 106.8 %, and relative standard deviation no more than 7.0 %, respectively. Therefore, this novel approach possesses significantly potential in clinical diagnosis and prognosis evaluation of glycoprotein related diseases. [ABSTRACT FROM AUTHOR]