Enzymatic cascade catalysis has emerged as an effective means to enhance the sensitivity of biosensors due to its remarkable amplification effect on electrochemical signals.However,the most used natural enzymes have high specificity and high catalytic activity,but are susceptible to environmental factors,easy denaturation and inactivation,and high cost,which limit their practical applications.Additionally,the majority of nanozymes with excellent catalytic activity cannot be directly used as redox probes.The redox signal can only be required under high potentials in strong acid/alkali solutions,or functionalized with electroactive substances.To tackle this problem,herein,AuNPs(glucose oxidase-like activity)and Mn,Zr dual-doped CeO2 nanozymes(Mn,Zr-CeO2,peroxidase-like activity)were used as model enzymes to construct a high-performance nanozymes cascade catalytic system.Owing to high Ce4+/Ce3+ratio and a considerable number of oxygen vacancies,Mn,Zr-CeO2 nanozymes exhibited excellent peroxidase-like activity and could generate amplified electrochemical signals in neutral medium at low potentials.Furthermore,the porous structure of Mn,Zr-CeO2 nanozymes could accelerate the mass transfer of intermediate H2O2,thereby enhancing the efficiency of enzymatic cascade catalysis.As a result,a label-free electrochemical biosensor was constructed for sensitive detection of the cancer marker miRNA-21 at physiological pH,with a detection limit as low as 32.5 fmol/L.This strategy offered a novel approach for the development of a new generation of high-performance nanozymes cascade platforms,which could be widely applied in the fields such as biotechnology,bioanalysis,and disease diagnosis.

Objective To observe the association between adiponectin and small dense low-density lipoprotein (sLDL-c) in coronary artery disease (CAD) patients.Furthermore,we sought to determine the association between single nucleotide polymorphisms (SNP) rs1501299 ( + 276G/T ), rs266729 (-11365C/G) and the incidence of CAD.Methods Consecutive subjects with chest discomfort were examined by coronary angiography and divided into non-CAD [ n =250,147 male,mean age (60.26 ±7.52) years] and CAD [n =267,153 male,mean age (60.79 ±9.63) years] groups.Blood samples were collected from all participants following an overnight fasting for at least 12 hours.Plasma adiponectin levels were measured by competitive enzyme-linked immunosorbent assay (ELISA).The serum levels of sLDL-C and oxidized low-density lipoprotein (ox-LDL) were determined by ELISA.Genotypes in rs1501299 and rs266729 of the adiponeetin were determined by polymerase chain reaetion ( PCR ).Results 1.The adiponectin levels were significantly lower [ ( 306.17 ± 74.52 ) mg/L vs.( 321.78 ± 86.28 ) mg/L ],whereas sLDL-C and ox-LDL levels were significantly higher [ ( 276.30 ± 45.55 ) ng/L vs.( 249.00 ±32.02) ng/L and (545.06 ± 115.46 ) μg/L vs.(497.74 ± 106.09 ) μg/L,P ＜ 0.05 ] in CAD group than non-CAD group.2.Adiponectin level was negatively associated with sLDL-C,whereas sLDL-C positively correlated with ox-LDL in all subjects.3.Genotype distribution and allele frequencies of rs1501299 and rs266729 were similar between CAD and non-CAD subjects and not related to the serum levels of adiponectin, sLDL-C and ox-LDL.Conclusions Reduced adiponectin and increased sLDL-C were independent risk factors for coronary artery disease.Genetic polymorphisms in rs1501299 and rs266729 were not linked with coronary artery disease.

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