An ultrasensitive electrochemical aptasensor for early diagnosis of Alzheimer's disease, using a fern leaves-like gold nanostructure

A Cardiac Troponin T Biosensor Based on Aptamer Self-assembling on Gold

In this study, a sensitive and accurate aptasensor was designed for early detection of myocardial infarction through the determination of troponin T (TnT). The successful immobilization of a specific aptamer sequence on the surface of gold that had a high affinity toward TnT was accomplished. TnT was electrochemically quantified. The results indicated that the aptasensor detected TnT in a range of 0.05-5 ng mL, and with a detection limit of 0.01 ng/mL. The performance of the aptasensor was investigated by analyzing 99 human serum samples. Both diagnostic specificity and sensitivity of the aptasensor were found to be 95%. The use of the designed aptamer-based biosensor could be an essential achievement in health policy, preventing deaths caused by myocardial infarction, and reducing patients with heart failure. The extensive use of this aptamer-based biosensor can also reduce costs, enhance speed, and improve accuracy in the diagnosis of TnT as an important myocardial infarction biomarker.

Immobilization Techniques for Aptamers on Gold Electrodes for the Electrochemical Detection of Proteins: A Review

The development of reliable biosensing platforms plays a key role in the detection of proteins in clinically and environmentally derived samples for diagnostics, as well as for process monitoring in biotechnological productions. For this purpose, the biosensor has to be stable and reproducible, and highly sensitive to detect potentially extremely low concentrations and prevent the nonspecific binding of interfering compounds. In this review, we present an overview of recently published (2017–2019) immobilization techniques for aptamers on gold electrodes for the electrochemical detection of proteins. These include the direct immobilization of thiolated aptamers and the utilization of short linkers, streptavidin/biotin interaction, as well as DNA nanostructures and reduced graphene oxide as immobilization platforms. Applied strategies for signal amplification and the prevention of biofouling are additionally discussed, as they play a crucial role in the design of biosensors. While a wide variety of amplification strategies are already available, future investigations should aim to establish suitable antifouling strategies that are compatible with electrochemical measurements. The focus of our review lies on the detailed discussion of the underlying principles and the presentation of utilized chemical protocols in order to provide the reader with promising ideas and profound knowledge of the subject, as well as an update on recent discoveries and achievements.

Electrochemical aptasensors based on the gold nanostructures

Electrochemical aptasensors as novel diagnostic tools have attracted sufficient research interest in biomedical sciences. In this review, recent leading trends about gold (Au) nanostructures based electrochemical aptasensors have been collected, reviewed, and compared. Here, the considered electrochemical aptasensors were categorized based on the analytes and diagnostic techniques. Pharmaceutical analytes and biomolecules were reviewed in a separate section consisting of a variety of antibiotics, analgesics, and other biomolecules. Various aptasensors have also measured toxins, ions, and hazardous chemicals, and the findings of them have also been reviewed. Many aptasensors have been designed to detect different disease biomarkers that will play an essential role in the future of early diagnosis of diseases. Pathogen microorganisms have been considered as the analyte in several designed electrochemical aptasensors in recent researches, and their results have been reviewed and discussed as another section. Important aspects considered in the review of the mentioned aptasensors were the type of analyte, features of the aptamer as the biorecognition element, type of Au nanostructures, diagnostic technique, diagnostic mechanism, detection range and the limit of detection (LOD). In the last section, an in-depth analysis has been provided based on the crucial features of all included aptasensors.

Aptamers in nanostructure-based electrochemical biosensors for cardiac biomarkers and cancer biomarkers: A review

Heart disease (especially myocardial infarction (MI)) and cancer are major causes of death. Recently, aptasensors with the applying of different nanostructures have been able to provide new windows for the early and inexpensive detection of these deadly diseases. Early, inexpensive, and accurate diagnosis by portable devices, especially aptasensors can increase the likelihood of survival as well as significantly reduce the cost of treatment. In this review, recent studies based on the designed aptasensors for the diagnosis of these diseases were collected, ordered, and reviewed. The biomarkers for the diagnosis of each disease were discussed separately. The primary constituent elements of these aptasensors including, analyte, aptamer sequence, type of nanostructure, diagnostic technique, analyte detection range, and limit of detection (LOD), were evaluated and compared.

Electrochemical immunosensor based on AuBP@Pt nanostructure and AuPd-PDA nanozyme for ultrasensitive detection of APOE4

An ultrasensitive sandwich-type electrochemical immunosensor based on AuBP@Pt nanostructures and AuPd-PDA nanozyme was developed for the detection of apolipoprotein E4 (APOE4) which was an important risk factor for Alzheimer's disease (AD). In this work, gold nanobipyramid coated Pt (AuBP@Pt) nanostructures were prepared and applied to electrochemical immunosensors as a substrate material. AuBP@Pt nanostructures have advantages of electrical conductivity and large electroactive area, which could greatly increase electron transfer rate. In previous work, we designed AuPd alloy modified polydopamine (AuPd-PDA) nanozyme which catalyzed the decomposition of hydrogen peroxide (H₂O₂). AuPd-PDA nanozyme was used to label detection antibody due to excellent catalytic capability and stability in this new paper. And the concentration of APOE4 could be detected quantitatively by variation for transient current. As a result, the electrochemical immunosensor based on AuBP@Pt and AuPd-PDA exhibited a wide linear range from 0.05 to 2000 ng mL⁻¹ and low detection limit of 15.4 pg mL⁻¹ (S/N = 3). Furthermore, the designed biosensor displayed good selectivity in phosphate buffer saline (PBS) buffer solution or commercial goat serum, which provided a promising tool for early diagnosis of AD.

An ultrasensitive sandwich-type electrochemical immunosensor based on AuBP@Pt nanostructures and AuPd-PDA nanozyme was developed for the detection of apolipoprotein E4 (APOE4) which was an important risk factor for Alzheimer's disease (AD).

Combined X-ray radiotherapy and laser photothermal therapy of melanoma cancer cells using dual-sensitization of platinum nanoparticles

Metal nanostructures are promising agents sensitizing by laser light and X-ray in photothermal therapy (PTT) and radiotherapy (RT) of cancer that improve treatment strategies of cancer. Nanoscale platinum materials are favorable in nanomedicine applications. In this study, platinum nanoparticles (PtNPs) were synthesized and applied for cancer therapy upon 808-nm laser light and X-ray radiation, or their combination. Two power densities of laser (1.0 and 1.5 W cm^-2) and three X-ray doses (2, 4 and 6 Gy) were selected for irradiation of B16/F10 cell line at 24 and 72 h-post treatment. The synthesized PtNPs had a spherical shape with a diameter of 12.2 ± 0.7 nm, and were cytocompatible up to 250 μg mL^-1. A photothermal conversion activity in a concentration-dependent manner at 72 h-post treatment was observed. Also, PtNPs represented cytotoxicity upon X-ray radiation doses of 2, 4, and 6 Gy after 24 h, while, 72-h time passing led to deeper outcomes. Dual radiation of laser light and X-ray into PtNPs considerably improved the treatment via reactive oxygen species (ROS) production. PtNPs can act as a novel dual absorber of laser light and X-ray, a common sensitizer, for treatment of cancer. The results of this study can be considered after further clinical investigations for treatment of tumor models.

An antifouling interface integrated with HRP-based amplification to achieve a highly sensitive electrochemical aptasensor for lysozyme detection

We report here a highly sensitive sandwich type electrochemical aptasensor for lysozyme (lys) detection by the integration of an antifouling interface with HRP-based signal amplification. The biosensing interface with antifouling ability is designed, consisting of a lys-binding aptamer (LBA), dithiothreitol (DTT) and mercaptohexanol (MCH). When lys is captured by the immobilized LBA due to the specific recognition of the aptamer, gold nanoparticles (AuNPs) functionalized with HRP and LBA (HRP-AuNP-LBA) are further conjugated to the surface-bound lys, forming a sandwich assay format. HRP catalyzes the chemical oxidation of hydroquinone (HQ) by hydrogen peroxide (H₂O₂) to produce benzoquinone (BQ) which results in a large electrochemical reduction signal of BQ. Therefore, this reduction signal measured by differential pulse voltammetry (DPV) is used to detect lys. The catalytic behavior of HRP toward the reaction between HQ and H₂O₂, together with the high loading of HRP on AuNPs, remarkably amplifies the signal. A linear relationship between the DPV response and the logarithm of lys concentration from 0.01 pg mL^-1 to 10⁵ pg mL^-1 with a detection limit of 0.003 pg mL^-1 (S/N = 3) is obtained. The proposed biosensing platform combines antifouling ability and signal amplification, resulting in high sensitivity, providing an effective way for ultrasensitive assay of protein biomarkers in complex media.