Hemin-graphene oxide-gold nanoflower-assisted enhanced electrochemiluminescence immunosensor for determination of prostate-specific antigen

Hemin as a Molecular Probe for Nitric Oxide Detection in Physiological Solutions: Experimental and Theoretical Assessment

Given its pivotal role in modulating various pathological processes, precise measurement of nitric oxide (●NO) levels in physiological solutions is imperative. The key techniques include the ozone-based chemiluminescence (CL) reactions, amperometric ●NO sensing, and Griess assay, each with its advantages and drawbacks. In this study, a hemin/H2O2/luminol CL reaction was employed for accurately detecting ●NO in diverse solutions. We investigated how the luminescence kinetics was influenced by ●NO from two donors, nitrite and peroxynitrite, while also assessing the impact of culture medium components and reactive species quenchers. Furthermore, we experimentally and theoretically explored the mechanism of hemin oxidation responsible for the initiation of light generation. Although both hemin and ●NO enhanced the H2O2/luminol-based luminescence reactions with distinct kinetics, hemin's interference with ●NO/peroxynitrite- modulated their individual effects. Leveraging the propagated signal due to hemin, the ●NO levels in solution were estimated, observing parallel changes to those detected via amperometric detection in response to varying concentrations of the ●NO-donor. The examined reactions aid in comprehending the mechanism of ●NO/hemin/H2O2/luminol interactions and how these can be used for detecting ●NO in solution with minimal sample size demands. Moreover, the selectivity across different solutions can be improved by incorporating certain quenchers for reactive species into the reaction.

Electrochemiluminescence immunosensor based on Cu3(PO4)2 hybrid nanoflowers as a novel luminophore for the sensitive detection of prostate-specific antigen

Copper phosphate hybrid nanoflowers (Cu3(PO4)2HNFs) were demonstrated to produce cathodic ECL emission in the presence of potassium persulfate (K2S2O8) and then used as a carrier due to their large specific surface area. AgNPs modified on Cu3(PO4)2HNFs provided more binding sites for immobilizing secondary antibodies and accelerating the electron transfer rate to enhance the ECL signal. In addition, FONDs-Au was used to capture primary antibodies due to its good biocompatibility and large specific surface area. A sandwich electrochemiluminescence (ECL) immunosensor based on copper phosphate hybrid nanoflower/Ag nanoparticle (Cu3(PO4)2HNFs@Ag) composite and Au NPs-functionalized Fe2O3 nanodendrites (FONDs-Au) was constructed to detect prostate-specific antigen (PSA) in real samples. Under optimal conditions, the constructed sandwich ECL immunosensor was sensitive to PSA with a detection limit of 0.037 pg/mL (S/N = 3), a linear detection concentration range of 0.0001-50 ng/mL, and a recovery range of 97.33-102.5%. This immunosensor is expected to provide a method to detect PSA or other biomarkers.

A Hemin-Graphene Nanocomposite-Based Aptasensor for Ultrasensitive Colorimetric Quantification of Leukaemia Cells Using Magnetic Enrichment

Diagnostic blood cell counting is of limited use in monitoring a minimal number of leukaemia cells, warranting further research to develop more sensitive and reliable techniques to identify leukaemia cells in circulation. In this work, a hemin-graphene nanocomposite-based aptasensor was developed for ultrasensitive colorimetric detection of leukaemia cells (CEM) using magnetic enrichment. Hemin-conjugated graphene oxide nanocomposites (HGNs) were prepared by hydrazine reduction using graphene oxide nanosheets and hemins. Hence, the prepared HGNs become able to absorb single-stranded DNA and acquire peroxidase-like activity. The aptamer sgc8c, which recognizes a specific target on leukaemia cells, was absorbed onto HGNs to capture the target CEM cancer cells. The captured target cells that associated with the HGNs were then concentrated and separated by magnetic beads (MBs) coated with sgc8c aptamers, forming a HGN-cell-MB sandwich structure. These sandwich structures can be quantified via an oxidation reaction catalysed by HGNs. By utilizing dual signal amplification effects generated by magnetic enrichment and the improved peroxidase activity of HGNs, the biosensor allowed for highly sensitive detection of 10 to 10⁵ CEM cells with an ultra-low limit of detection (LOD) of 10 cells under optimal conditions. It is expected that the proposed aptasensor can be further employed in monitoring the minimal residual disease during the treatment of leukaemia.