Dynamic light scattering and fluorescence dual-signal sensing of cancer antigen-125 via recognition of the polymerase chain reaction product with gold nanoparticle probe

CdS/Bi2S3/NiS ternary heterostructure-based photoelectrochemical immunosensor for the sensitive detection of carbohydrate antigen 125

The sensitive, accurate and rapid detection of carbohydrate antigen 125 (CA125) is essential for the early diagnosis and clinical management of ovarian cancer, but there is still challenge. Herein, a photoelectrochemical (PEC) immunosensor based on CdS/Bi2S3/NiS ternary sulfide heterostructured photocatalyst was presented for the detection of CA125. The CdS/Bi2S3/NiS was synthesized by a one-step hydrothermal approach. The heterojunction comprising of CdS and Bi2S3 could separate photogenerated carriers, the introduced narrow bandgap NiS could act as electron-conducting bridge to facilitate the transfer of interfacial photogenerated electrons, thereby improving the photoelectric conversion efficiency. Due to their synergistic effect, the photocurrent response produced by the composite was up to 14.6 times of pure CdS. On the basis, a PEC immunosensor was constructed by introducing the CA125 antibody through thioglycolic acid linkage. It was found that the resulting immunosensor showed good performance. Under the optimized conditions, its linear detection range was as wide as 1 pg mL-1-50 ng mL-1, and the detection limit was low to 0.85 pg mL-1. Furthermore, we experimentally tested its anti-interference, stability and reproducibility, and satisfactory results were achieved. The practicable feasibility of the sensor was confirmed by testing serum sample. Thus this work provided a simple, fast and enough sensitive approach for CA125 monitoring.

Naked-eye detection of plant viral disease using polymerase chain reaction amplification and DNAzyme

Plant viral diseases can seriously affect the yield and quality of crops. In this work, a convenient and highly sensitive biosensor for the visual detection of plant viral disease is proposed by the PCR-induced generation of DNAzyme. In the absence of nucleic acid for a target plant virus, the primers prohibited the production of G-quadruplex by forming a hairpin structure. However, PCR amplification occurred and generated a number of specific PCR products with free G-quadruplex sequences at both ends in the presence of the target cDNA. A catalytically active G-quadruplex DNAzyme was formed with the help of K+ and hemin, resulting in the formation of colored products visible to the naked eye and a strong absorbance by the addition of ABTS2- and H2O2. The absorbance and the logarithm of target cDNA concentrations showed a good linear relationship in the range of 10 fM-1.0 nM, with a linear regression equation of A = 0.1402 lg c + 0.3761 (c: fM) and a detection limit of 0.19 fM. This method was successfully applied to the analysis of emerging tobacco mosaic virus (TMV) infections in tobacco leaf samples collected in the field due to its flexibility and convenience, indicating a potential application for the early detection of plant viral disease.

Ultrasensitive detection of genetic variation based on dual signal amplification assisted by isothermal amplification and cobalt oxyhydroxide nanosheets/quantum dots

PML/RARα fusion gene (P/R) is the characteristic signature genetic variation of acute promyelocytic leukemia (APL). Here, by integrating triple-stranded DNA hybridization-triggered strand displacement amplification (tri-HT SDA) and cobalt oxyhydroxide nanosheets/quantum dots (CoOOH/QD)-based amplification, we constructed a novel biosensor of easy-operating, time-saving and high sensitivity for detecting P/R to meet clinical needs. Owing to the specific recognition and efficient amplification of tri-HT SDA as well as impressive anti-interference and considerable amplification of CoOOH/QD, this biosensor demonstrated a wide dynamic range (10 fM to 10 nM) with a low limit of detection (5.50 fM) in P/R detection. Additionally, this biosensor could detect P/R spiked into human serum with good recoveries and relative standard deviation (RSD), thus potentially exhibiting ultrasensitive and specific nuclear acid sequence detection ability in clinical diagnosis owing to combing isothermal amplification and nanomaterials.

Luminescence of carbon quantum dots and their application in biochemistry

Similar to fullerenes, carbon nanotubes and graphene, carbon dots (CDs) are causing a lot of research work in their own right. CDs are a type of surface-passivated quantum dot that contain carbon atoms. Their distinctive characteristics, such as luminescent emission that varies with size and wavelength, resistance to photobleaching, easy biological binding, lack of toxicity, and economical production without the need for intricate synthetic processes, have led to a noteworthy surge in attention within the research community. Different techniques can be utilized to create these CDs, spanning from basic candle burning to laser ablation. This review article delves into the principles of fluorescence technology, providing insights into how different synthesis methods of quantum dots impact their luminescent properties. Additionally, it highlights the latest applications of quantum dots in catalysis and biomedical fields, with special emphasis on the current status of luminescent properties in biology and chemistry. Towards the end, the article discusses the limitations of quantum dots in current practical applications, pointing out that CDs hold promising potential for future applications.

A simple and programmable dual-mode aptasensor for the ultrasensitive detection of multidrug-resistant bacteria

Accurately identifying multidrug-resistant (MDR) bacteria from clinical samples has long been a challenge. Herein, we report a simple and programmable dual-mode aptasensor called DAPT to reliably detect MDR bacteria. The DAPT method comprises two elements, namely the mode of dynamic light scattering (Mode-DLS) for ultrasensitive detection and the mode of fluorescence (Mode-Flu) for reliable quantification as a potent complement. Benefiting from the states of aptamer-modified gold nanoparticles (AptGNPs) sensitively changing from dispersion to aggregation, the proposed Mode-DLS achieved the rapid, specific, and ultrasensitive detection of methicillin-resistant Staphylococcus aureus (MRSA) at the limit of detection (LOD) of 4.63 CFU mL^-1 in a proof-of-concept experiment. Simultaneously, the Mode-Flu ensured the accuracy of the detection, especially at a high concentration of bacteria. Moreover, the feasibility and universality of the DAPT platform was validated with four other superbugs by simply reprogramming the corresponding sequence. Overall, the proposed DAPT method based on a dual-mode aptasensor can provide a universal platform for the rapid and ultrasensitive detection of pathogenic bacteria due to its superior programmability.

Application of Various Optical and Electrochemical Nanobiosensors for Detecting Cancer Antigen 125 (CA-125): A Review

Nowadays, diagnosing early-stage cancers can be vital for saving patients and dramatically decreases mortality rates. Therefore, specificity and sensitivity in the detection of cancer antigens should be elaborately ensured. Some early-stage cancers can be diagnosed via detecting the cancer antigen CA-125, such as ovarian cancer, and required treatments can be applied more efficiently. Thus, detection of CA-125 by employing various optical or electrochemical biosensors is a preliminary and crucial step to treating cancers. In this review, a diverse range of optical and electrochemical means of detecting CA-125 are reviewed. Furthermore, an applicable comparison of their performance and sensitivity is provided, several commercial detection kits are investigated, and their applications are compared and discussed to determine whether they are applicable and accurate enough.

M13 bacteriophage as biometric component for orderly assembly of dynamic light scattering immunosensor

The ordered assembly of nanostructure is an effective strategy used to manipulate the hydrodynamic diameter (D_H) of nanoparticles. Herein, a versatile dynamic light scattering (DLS) immunosensing platform is presented to sensitively detect small molecules and biomacromolecules by using the M13 phage as the building module to order the assembly of gold nanoflowers and gold-coated magnetic nanoparticles, respectively. After the directional assembly of M13 phage, the D_H of the probes was significantly increased due to its larger filamentous structure, thus improving the detection sensitivity of the DLS immunosensor. The designed M13 assembled DLS immunosensor with competitive and sandwich formats showed high sensitivities for ochratoxin A and alpha-fetoprotein in real corn and undiluted serum samples, with the detection limits of 1.37 and 57 pg/mL, respectively. These values are approximately 15.8 and 164.9 times lower than those of traditional phage-based enzyme-linked immunosorbent assays. Collectively, this work provides a promising strategy to manipulate the D_H of nanoparticles by highly evolved biomaterials such as engineered M13 phages and opens upon a new direction for developing DLS immunosensors to detect various targets by the fusion expression of special peptide or nanobody on the pIII or pVIII protein of M13 phage.

A competitive colorimetric aptasensor for simple and sensitive detection of kanamycin based on terminal deoxynucleotidyl transferase-mediated signal amplification strategy

We developed a rapid and sensitive colorimetric biosensor based on competitive recognition between kanamycin (KAN), magnetic beads-kanamycin (MBs-KAN) and aptamer and terminal deoxynucleotidyl transferase (TdT)-mediated signal amplification strategy. In the absence of KAN, aptamers recognize MBs-KAN. TdT can amplify oligonucleotides to the 3'-OH ends of aptamers, with biotin-dUTP being embedded in the long single stranded DNA (ssDNA). Then the assay produced visual readout due to the horseradish peroxidase (HRP)-catalyzed color change of the substrate after the linkage between biotin and streptavidin (SA)-HRP. In the presence of KAN, however, aptamers tend to bind free KAN rather than MBs-KAN. In this case, aptamers are isolated by magnetic separation, resulting in the failure of signal amplification and catalytic signals. This competitive colorimetric sensor showed excellent selectivity toward KAN with the limit of detection (LOD) as low as 9 pM. And recovery values were between 93.8 and 107.8% when spiked KAN in milk and honey samples.

Gold nanoparticle-based optical nanosensors for food and health safety monitoring: recent advances and future perspectives

Modern society has been facing serious health-related problems including food safety, diseases and illness. Hence, it is urgent to develop analysis methods for the detection and control of food contaminants, disease biomarkers and pathogens. As the traditional instrumental methods have several disadvantages, including being time consuming, and having high cost and laborious procedures, optical nanosensors have emerged as promising alternative or complementary approaches to those traditional ones. With the advantages of simple preparation, high surface-to-volume ratio, excellent biocompatibility, and especially, unique optical properties, gold nanoparticles (AuNPs) have been demonstrated as excellent transducers for optical sensing systems. Herein, we provide an overview of the synthesis of AuNPs and their excellent optical properties that are ideal for the development of optical nanosensors based on local surface plasmon resonance (LSPR), colorimetry, fluorescence resonance energy transfer (FRET), and surface-enhanced Raman scattering (SERS) phenomena. We also review the sensing strategies and their mechanisms, as well as summarizing the recent advances in the monitoring of food contaminants, disease biomarkers and pathogens using developed AuNP-based optical nanosensors in the past seven years (2015-now). Furthermore, trends and challenges in the application of these nanosensors in the determination of those analytes are discussed to suggest possible directions for future developments.

Aptamer Nanomaterials for Ovarian Cancer Target Theranostics

Ovarian cancer is among the leading causes of gynecological cancer-related mortality worldwide. Early and accurate diagnosis and an effective treatment strategy are the two primary means of improving the prognosis of patients with ovarian cancer. The development of targeted nanomaterials provides a potentially efficient strategy for ovarian cancer theranostics. Aptamer nanomaterials have emerged as promising nanoplatforms for accurate ovarian cancer diagnosis by recognizing relevant biomarkers in the serum and/or on the surface of tumor cells, as well as for effective ovarian cancer inhibition via target protein blockade on tumor cells and targeted delivery of various therapeutic agents. In this review, we summarize recent advances in aptamer nanomaterials as targeted theranostic platforms for ovarian cancer and discusses the challenges and opportunities for their clinical application. The information presented in this review represents a valuable reference for creation of a new generation of aptamer nanomaterials for use in the precise detection and treatment of ovarian cancer.