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As one of the most well-known metal nanoparticles, gold nanoparticles (AuNPs) have attracted much attention for the biological applications. This great interest in AuNPs can be attributed to their outstanding physical and chemical properties, such as special optical and electrochemical characteristics, high X-ray attenuation ability, strong X-ray absorption, photothermal effect, stability and biocompatibility. In addition, due to the ease of synthesis and modification of the surface of AuNPs, it is possible to control their shape, size and surface characteristics. All these features suggest that AuNPs can be used for biosensing strategies, drug delivery, photothermal therapy, nanobrachytherapy, enhanced radiotherapy and CT imaging. In addition, they can be used as antibacterial and antifungal agents. This minireview focuses on the key principles, research achievements and new opportunities in the synthesis of AuNPs as well as their biological applications. In fact, the growing progress in the use of AuNPs for the diagnostic and therapeutic applications is described in this survey. Overall, a better understanding of the key aspects of the synthesis methodologies will lead to the development of new protocols that can provide ideas for more cost-effective and reliable approaches to the production of AuNPs. [ABSTRACT FROM AUTHOR]

The outbreak rate of human coronaviruses (CoVs) especially highly pathogenic CoVs is increasing alarmingly. Early detection of these viruses allows treatment interventions to be provided more quickly to people at higher risk, as well as helping to identify asymptomatic carriers and isolate them as quickly as possible, thus preventing the disease transmission chain. The current diagnostic methods such as RT-PCR are not ideal due to high cost, low accuracy, low speed, and probability of false results. Therefore, a reliable and accurate method for the detection of CoVs in biofluids can become a front-line tool in order to deal with the spread of these deadly viruses. Currently, the nanomaterial-based sensing devices for detection of human coronaviruses from laboratory diagnosis to point-of-care (PoC) diagnosis are progressing rapidly. Gold nanoparticles (AuNPs) have revolutionized the field of biosensors because of the outstanding optical and electrochemical properties. In this review paper, a detailed overview of AuNP-based biosensing strategies with the varied transducers (electrochemical, optical, etc.) and also different biomarkers (protein antigens and nucleic acids) was presented for the detection of human coronaviruses including SARS-CoV-2, SARS-CoV-1, and MERS-CoV and lowly pathogenic CoVs. The present review highlights the newest trends in the SARS-CoV-2 nanobiosensors from the beginning of the COVID-19 epidemic until 2022. We hope that the presented examples in this review paper convince readers that AuNPs are a suitable platform for the designing of biosensors. [ABSTRACT FROM AUTHOR]

Abstract In this work, a novel simple and sensitive electrochemical immunosensor was developed based on lactate oxidase as a single electrochemical probe for the detection of carcinoma antigen 125 (CA125). Chitosan-gold nanoparticle/multiwall carbon nanotube/graphene oxide (CS-AuNP/MWCNT/GO) was used as the electrode substrate to increase the electrode specific surface area and improve the protein immobilization and the electrochemical performance of the electrode in terms of oxidation of H 2 O 2. Due to the peroxidase-like function of CS-AuNP, the oxidation peak of H 2 O 2 was observed at a very low potential (0.034 V). The lactate oxidase is used, for the first time, as the single-enzyme label in a sandwich type immunosensor. In the optimum condition, the designed immunosensor exhibited two linear ranges (0.01–0.5 U/mL and 0.5–100 U/mL) by chronoamperometry (CHA). The limit of detection (LOD) was estimated to be 0.002 U/mL. The immunosensor displayed excellent reproducibility and stability with remarkable selectivity in terms of the detection of CA125 even in the human serum samples as compared to the ELISA. In conclusion, the engineered immunosensor is proposed as an ultra-sensitive tool for the detection and monitoring of CA125 in the human serum. Graphical abstract fx1 Highlights • A novel sandwich immunosensor based on lactate oxidase as a single-enzyme label was developed for the detection of CA125. • Gold nanoparticles were synthesized using chitosan as the reducing and capping agent. • The potential of hydrogen peroxide oxidation was reduced to 0.034 V by the chitosan-Au nanoparticles. • CA125 was detected with a low limit of detection of 0.002 U/mL and a linear range of 0.01–100 U/mL. [ABSTRACT FROM AUTHOR]

Herein, aptamer-modified self-propelled nanomotors were used for transportation of human promyelocytic leukemia cells (HL-60) from a human serum sample. For this purpose, the fabricated manganese oxide nanosheets-polyethyleneimine decorated with nickel/gold nanoparticles (MnO 2 -PEI/Ni/Au) as nanomotors were added to a vial containing thiolated aptamer KH1C12 solution as a capture aptamer to attach to the gold nanoparticles on the surface of nanomotors covalently. The aptamer-modified self-propelled nanomotors (aptamer KH1C12 /nanomotors) were then separated by placing the vial in a magnetic stand. The aptamer-modified self-propelled nanomotors were rinsed three times with water to remove the non-attached aptamers. Then, the resulting aptamer KH1C12 /nanomotors were applied for the on-the-fly” transporting of HL-60 cancer cell from a human serum sample. To release of the captured HL-60 cancer cells, the complementary nucleotide sequences of KH1C12 aptamer solution (releasing aptamer) that has a with capture aptamer was added to phosphate buffer solution (1 M, pH 7.4) containing HL-60/aptamer KH1C12 /nanomotors. Because of the high affinity of capture aptamer to complementary nucleotide sequences of aptamer KH1C12 , the HL-60 cancer cells released on the surface of aptamer KH1C12 /nanomotors into the solution. The second goal of the present work was determining the concentration of HL-60 cancer cell in the human serum samples. The electrochemical impedance spectroscopy technique (EIS) was used for the determination of HL-60 cancer cell. The concentration of separated cancer cell was determined by aptamer/gold nanoparticles-poly(3,4-ethylene dioxythiophene) modified GC electrode (GC/PEDOT-Au nano /aptamer KH1C12 ). The proposed aptasensor exhibited a good response to the concentration of HL-60 cancer cells in the range of 2.5 × 10 1 to 5 × 10 5 cells mL -1 with a low limit of detection of 250 cells mL -1 . [ABSTRACT FROM AUTHOR]

In the current study, we report on the design and development of a novel electrochemical immunosensor for the detection of cancer antigen 125 (CA125) oncomarker. Polyamidoamine/gold nanoparticles (PAMAM/AuNPs) were used to increase the conductivity and enhance the number of antibodies (Abs) immobilized on the electrode surface. Three-dimensional reduced graphene oxide-multiwall carbon nanotubes (3DrGO-MWCNTs) were used to modify the glassy carbon electrode to improve the electrode conductivity and specific surface area. Ab and toluidine blue attached to O -succinyl-chitosan-magnetic nanoparticles (Suc-CS@MNPs) as a tracer. The poor solubility of chitosan (CS) was improved by succinic anhydride using a novel modification method. Under optimum condition, the developed immunosensor exhibited a wide linear range (0.0005–75 U/mL) and an excellent limit of detection around 6 μU/mL. The reliability of the engineered immunosensor in detecting CA125 was verified by standard addition recovery method, which was further compared to enzyme-linked immunosorbent assay (ELISA). The proposed immunosensor exhibited excellent stability, high selectivity and sensitivity, and good reproducibility. Based on the great performance of the engineered immunosensor, it is proposed as a robust and reliable diagnostic tool for the detection of CA125 in the clinic. Image 1 • An immunosensor was developed for detecting CA125 with a wide linear range (0.0005–75 U/mL) and an excellent LOD (6 μU/mL). • PAMAM/AuNPs were synthesized through a one-step method using PAMAM as a stabilizing and reducing agent. • Chitosan water solubility in natural pH was increased using a novel modification method. • Succinyl-chitosan-coated magnetic nanoparticles were synthesized with good dispersity and high surface functional groups. [ABSTRACT FROM AUTHOR]