TiO2/SnO -Au nanocomposite catalyzed photochromic reaction for colorimetric immunoassay of tumor marker

Molybdenum blue mediated photothermal immunoassay for CEA detection based on Ag4P2O7@Ag nanocomposites

A photothermal immunoassay was built for tumor marker detection based on Ag₄P₂O₇@Ag nanocomposites. Ag₄P₂O₇@Ag nanomaterials were synthesized by precipitation-photoreduction reaction, and characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectra (XPS) and X-ray powder diffraction (XRD). Come about PO₄^3- derived from Ag₄P₂O₇@Ag under acidic conditions react with ammonium molybdate in the action of reductant generating molybdenum blue. The photothermal change is due to molybdenum blue solution depending on the concentration of carcinoembryonic antigen (CEA) in immunoassay. Under optimal conditions, there is a linear relation between ΔT and CEA concentration in the range of 1 pg mL^-1-40 ng mL^-1 with the detection limit of 0.33 pg mL^-1. Meanwhile, the developed photothermal immunoassay displays preferable selectivity, repeatability, and stability.

Recent developments on nanomaterial-based optical biosensor as potential Point-of-Care Testing (PoCT) probe in carcinoembryonic antigen detection: A review

For the past decades, several cancer biomarkers have been exploited for rapid and accurate prognosis or diagnosis purposes. In this review, the optical biosensor is targeted for carcinoembryonic antigen (CEA) detection. The CEA level is a prominent parameter currently used in clinical cases for the prognosis of cancer-related diseases. Many nanomaterial-based biosensors are invented as alternatives for the commonly used enzyme-linked immunosorbent assays (ELISA) immunoassay method in CEA detection as the traditional approach but they possess certain drawbacks such as tedious procedure, high technical demand, and costly. Nevertheless, the effort appears to be wasted as none of them are being actualised. Generally, the sensor function was carried out by converting bio-signals generated upon the interface of the receptor into light signals. These sensors were popular due to specific advantages such as sensitivity, being free from chemical and electromagnetic interferences, wide dynamic range, and being easy to be monitored. The features of PoC diagnostics are discussed and associated with the various applications of colorimetric-based and chemiluminescent-based biosensors. The roles of nanomaterials in each application were also summarised by comparing the modification, incubation period, lowest detection limit (LOD) and linear range of detection amount. The challenges and future perspectives were highlighted at the end of the review.

Ratiometric electrochemical aptasensor for the sensitive detection of carcinoembryonic antigen based on a hairpin DNA probe and exonuclease I-assisted target recycling

A novel ratiometric electrochemical aptasensor was constructed for the detection of carcinoembryonic antigen (CEA) based on a hairpin DNA (hpDNA) probe and exonuclease Ⅰ (Exo Ⅰ)-assisted target recycling amplification strategy. A thiolated methylene blue (MB)-labeled hpDNA as the internal control element was fixed on the surface of the gold nanoparticles (AuNPs)-modified gold electrode (AuE) through Au-S bonds. A ferrocene (Fc)-modified aptamer DNA (Fc-Apt) was partially hybridized with hpDNA to form a Fc-Apt/hpDNA duplex. Due to the specific recognition of Fc-Apt to CEA, the presence of CEA caused dissociation of Fc-Apt from the duplex, and further triggered the degradation process of Exo Ⅰ and recycling of CEA. Hence, the Fc tags were released from the electrode surface and the oxidation peak current of Fc (I_Fc) decreased while that of MB (I_MB) remained stable owing to the distance between MB tags and the electrode unchanged. A linear relationship was observed between I_Fc/I_MB and the logarithm of CEA concentration from 10 pg mL^-1 to 100 ng mL^-1 with a detection limit of 1.9 pg mL^-1. Moreover, the developed aptasensor had been applied to detect CEA in diluted human serum with satisfactory results, indicating its great potential in practical applications.

Rapid and sensitive detection of PD-L1 exosomes using Cu-TCPP 2D MOF as a SPR sensitizer

Two-dimensional metal organic framework (2D MOF Cu-TCPP) with significantly enhanced photoelectric properties was synthesized by a simple hydrothermal method. The π-stacked electroactive porphyrin molecules of TCPP-based 2D MOF carry out charge transport in the MOF structure. The d-d band transition of Cu²⁺ and its 2D ultra-thin characteristics can produce excellent near-infrared light absorption to couple with SPR. Three key parameters including the refractive index sensitivity, detection accuracy and quality factor were improved significantly for 2D MOF modified gold chips. Especially, the refractive index sensitivity was increased from 98 to 137.67°/RIU after modified with 2D MOF. Thus, for the first time, we applied it as a signal enhancer to improve direct SPR assay for the Programmed death ligand-1 (PD-L1) exosomes. Owning to its large specific surface area, excellent photoelectric properties, highly ordered structure, good dispersion and biocompatibility, the LOD of the SPR sensor was 16.7 particles/mL. The reliability and practicability were further validated by analysis of PD-L1 exosomes in human serum samples. The recovery rate was 93.43 %-102.35%, with RSD of 5.79 %-14.6%. Given their excellent signal amplification ability, 2D MOF Cu-TCPP could serve as an ideal SPR sensitizer for rapid and sensitive detection of trace disease markers.

Biocatalyst and colorimetric biosensor of carcinoembryonic antigen constructed via chicken egg white-copper phosphate organic/inorganic hybrid nanoflowers

In this article, the dual-functional chicken egg white-copper phosphate organic-inorganic hybrid nanoflowers (Cu-NFs), combining the functions of signal amplification and biological recognition, were prepared through a simple one-pot method. The Cu-NFs exhibit excellent biocatalytic activity of peroxidase and polyphenol oxidase. Besides, a biotin-labeled secondary antibody encapsulated Cu-NFs-2 (Cu-NFs-2@Biotin-NHS-Ab₂) capture probe was prepared by using the interaction between avidin in the egg white and biotin. Based upon this superiority, the as-prepared Cu-NFs-2 were used in labeled avidin-biotin enzyme-linked immunosorbent assay (Cu-NFs-2 based-LAB-ELISA) to construct a sensitive colorimetric biosensor for the ultrasensitive detection of carcinoembryonic antigen (CEA). Under weak alkaline (pH = 7.5) conditions, the as-developed colorimetric sensor displayed a wide linear range of 0.05-40 ng/mL with a detection limit of 3.52 pg/mL. Furthermore, this colorimetric sensor has been successfully applied to the detection of CEA in human serum samples. Therefore, the as-developed colorimetric sensor has broad application prospects in the field of medical diagnosis and portable detection.

Recent advances in nanomaterials for colorimetric cancer detection

The early diagnosis of cancer can significantly improve patient survival rates. Colorimetric methods for real-time naked-eye detection have aroused growing interest owing to their low cost, simplicity, and practicability. With the rapid development of nanotechnology, compared with conventional diagnostic methods, nanomaterials with unique physical and chemical properties were applied to improve selectivity and sensitivity in colorimetric detection of cancer biomarkers, such as MUC1 aptamer conjugated PtAuNPs to specifically recognize MUC1 proteins on the cancer cell surfaces, etching of silver nanoprisms to detect prostate-specific antigen, and aggregation or dispersion of AuNPs to sense prostate cancer antigen gene 3 or glutathione, by which the limit of detection (LOD) could approach values down to a few cancer cells per mL, several fg per mL proteins, several ng of nucleic acids, or even tens of nM of organic molecules. Herein, we review the recent progress achieved in developing colorimetric nanosensors for cancer diagnosis, particularly providing an overview of the sensing principles, target biomarkers, advanced nanomaterials employed in the fabrication of sensing platforms, and strategies for improving signal sensitivity and specificity. Finally, we sum up the nanomaterial-based colorimetric cancer detection as well as existing challenges that should be resolved to extend their clinical application.

Gold-Nanohybrid Biosensors for Analyzing Blood Circulating Clinical Biomacromolecules: Current Trend toward Future Remote Digital Monitoring

Mortality level is worsening the situation worldwide thru blood diseases and greatly jeopardizes the human health with poor diagnostics. Due to the lack of successful generation of early diagnosis, the survival rate is currently lower. To overcome the present hurdle, new diagnostic methods have been choreographed for blood disease biomarkers analyses with the conjunction of ultra-small ideal gold nanohybrids. Gold-hybrids hold varieties of unique features, such as high biocompatibility, increased surface-to-volume ratio, less-toxicity, ease in electron transfer and have a greater localized surface plasmon resonance. Gold-nanocomposites can be physically hybrid on the sensor surface and functionalize with the biomolecules using appropriate chemical conjugations. Revolutionizing biosensor platform can be prominently linked for the nanocomposite applications in the current research on medical diagnosis. This review encloses the new developments in diagnosing blood biomarkers by utilizing the gold-nanohybrids. Further, the current state-of-the-art and the future envision with digital monitoring for facile telediagnosis were narrated.

Bioconjugated gold nanoparticles as an efficient colorimetric sensor for cancer diagnostics

The chances of curing and reducing the adverse effect of cancer partly lie in early detection. Colorimetric sensor-based technique show promising results since the target is detected with high sensitivity but without the use of advanced/costly techniques through a simple visual color change. In most cases, gold nanoparticles (Au Nps) functionalized with biomolecules complementary to target analyte are used for colorimetric detection. The interaction of functionalized Au Nps with target analytes induce aggregation or dispersion where the color of the solution changes from red to blue or blue to red respectively, which can be visualized by the naked eyes. Such a facile technique has a high commercial viability and therefore, understanding its concept is essential. Here, some of the reported studies are discussed technically for better understanding about the invitro colorimetric detection of cancer.