An electrochemical aptasensor is described for the detection of prostate specific antigen (PSA). The aptasensor is based on the use of hemin-functionalized graphene-conjugated palladium nanoparticles (H-Gr/PdNPs) deposited on a glassy carbon electrode. The nanocomposites integrate the high electrical conductivity of graphene with the easily functionalized surface chemistry of PdNPs and their excellent catalytic property. The hemin placed on graphene acts as both a protective agent and an in-situ redox probe. The PdNPs provide numerous binding sites for the immobilization of DNA-biotin via coordinative binding between Pd and amino groups. A sensitive and specific PSA assay was attained by immobilizing the PSA aptamer via biotin-streptavidin interaction. The resulting aptasensor has a linear response that covers the PSA concentration range from 0.025 to 205 ng·mL, with a 8 pg·mL lower detection limit (at -0.362 V, scan rate: 0.1 mV·s, S/N = 3). The method was applied to the quantitation of PSA in spiked serum samples, giving recoveries ranging from 95.0 to 100.3%. Graphical abstract A signal amplified and approving electrochemical aptasensor was constructed for the determination of prostate specific antigen (PSA) based on the use of hemin-functionalized graphene conjugated to palladium nanoparticles (H-Gr/PdNPs). The sensor has a wide linear range, a relatively low detection limit, satisfying stability and high specificity.

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Cu­(I)-catalyzed azide-alkyne cycloaddition (CuAAC), the representative reaction of modern “click chemistry”, has been broadly employed in organic synthesis, bio-labeling, and surface functionalization. Nevertheless, it has limitations such as posing a dilemma of either using high concentrations of Cu­(I) catalyst or suffering from slow kinetics. Herein, we demonstrate that a newly selected DNAzyme (CLICK-17; a 79-nucleotide, catalytic DNA single strand) can rapidly catalyze CuAAC to tether redox functionalities onto an electrode surface using low concentrations of either Cu­(I) or Cu (II). Particularly, the CLICK-17 DNAzyme, at μM concentrations, facilitated the covalent immobilization of ethynylferrocene (Fc-CCH) onto 1-azido-11-undecanethiolate self-assembled monolayers on gold (N3C11S-Au SAMs); as low as 50 μM Cu­(I) together with 4 μM DNAzyme was able to complete the coupling reaction within 30 min and the pseudo first-order reaction rate constant is 7 times higher than that using the Cu­(I) catalyst alone. It was also remarkable that the CLICK-17 DNAzyme is functional with Cu­(II) in the absence of an explicit reductant for the catalyzed surface immobilization of Fc-CCH on N3C11S-Au SAMs.

In this work, a novel electrochemical aptasensor was developed for sensitive and selective detection of myoglobin based on meso-tetra (4-carboxyphenyl) porphyrin-functionalized graphene-conjugated gold nanoparticles (TCPP–Gr/AuNPs). Due to its good electric conductivity, large specific surface area, and excellent mechanical properties, TCPP–Gr/AuNPs can act as an enhanced material for the electrochemical detection of myoglobin. Meanwhile, it provides an effective matrix for immobilizing myoglobin-binding aptamer (MbBA). The electrochemical aptasensor has a sensitive response to myoglobin in a linear range from 2.0 × 10−11 M to 7.7 × 10−7 M with a detection limit of 6.7 × 10−12 M (S/N = 3). Furthermore, the method has the merits of high sensitivity, low price, and high specificity. Our work will supply new horizons for the diagnostic applications of graphene-based materials in biomedicine and biosensors.