Aptamer-Based Magnetic Nanoprobe for Quantitative Measurement of Chloramphenicol in Milk through Portable Reader.

Background: We described here an aptamer-based magnetic nanoprobe for measuring the amount of chloramphenicol (CAP) in milk. Methods: The nanoprobe presented in this method consists of a magnetic nanoparticle conjugated to a specific CAP aptamer. If the target is detected in the sample, the nanoprobe binds to it, and the aptamer forms a G-quadruplex structure. This structure mimics the peroxidase activity in the presence of the hemin cofactor. If tetramethylbenzidine is added to the sample containing the nanoprobe, a blue color light is observed. After adding a stop reagent solution, the color produced is measured by a microplate reader and a portable meter. Results: This study proves a 99% positive linear relationship between the microplate reader's results and the portable meter results. Conclusion: Conjugation of the aptamer to magnetic nanoparticles and applying magnetic separation operations change the nanoprobe performance by 11% for both mentioned devices.

The Role of Advanced Technologies against COVID-19: Prevention, Detection, and Treatments.

Concurrent with the global outbreak of COVID-19, the race began among scientists to generate effective therapeutics for the treatment of COVID-19. In this regard, advanced technology such as nanotechnology, cell-based therapies, tissue engineering and regenerative medicine, nerve stimulation and artificial intelligence (AI) are attractive because they can offer new solutions for the prevention, diagnosis and treatment of COVID-19. Nanotechnology can design rapid and specific tests with high sensitivity for detecting infection and synthases new drugs and vaccines based on nanomaterials to directly deliver the intended antiviral agent to the desired site in the body and also provide new surfaces that do not allow virus adhesion. Mesenchymal stem cells and exosomes secreted from them apply in regenerative medicine and regulate inflammatory responses. Cell therapy and tissue engineering are combined to repair or substitute damaged tissues or cells. Tissue engineering using biomaterials, cells, and signaling molecules can develop new therapeutic and diagnostic platforms and help scientists fight viral diseases. Nerve stimulation technology can augment body's natural ability to modulate the inflammatory response and inhibit pro-inflammatory cytokines and consequently suppress cytokine storm. People can access free online health counseling services through AI and it helps very fast for screening and diagnosis of COVID-19 patients. This study is aimed first to give brief information about COVID-19 and the epidemiology of the disease. After that, we highlight important developments in the field of advanced technologies relevant to the prevention, detection, and treatment of the current pandemic.

Fluorescent Detection of Methicillin Resistant Staphylococcus aureus by Loop-mediated Isothermal Amplification Assisted with Streptavidin-coated Quantum Dots.

Background: Methicillin Resistance Staphylococcus aureus (MRSA) could be considered as a major concern in medicine can cause nosocomial infection and bacteremia, especially in patients using catheter and household medical devices. Methods: Using molecular diagnostic methods are important for identification of MRSA from the Methicillin Sensitive Staphylococcus aureus (MSSA). Here we described a fluorescent assay using biotin-labelling Loop-mediated isothermal amplification (LAMP) method assisted with streptavidin-coated Quantum Dots (QDs) for detection of MRSA. For comparison, another fluorescent assay using LAMP assisted with Green Viewer (GV; a fluorescent dye) was applied for detection of MRSA. The mecA gene was selected as the target for amplification by LAMP and for biotin-labeling of the LAMP amplicons, biotin-11-dUTP was mixed with the dNTPs (deoxy Nucleotide Phosphates) in LAMP reaction. For determining the clinical performance of the developed assay, 30 blood samples with MRSA positive results were tested with QD-LAMP, the conventional LAMP, GV-LAMP, and Polymerase Chain Reaction (PCR). Results: Obtained results indicated that % sensitivity of QD-LAMP was 86.66% for detection of mecA positive MRSA samples; however, the Limit of Detection (LoD) of QD-LAMP was 1.5×104 Colony Forming Unit (CFU). Conclusion: The results suggested that the QD-LAMP assay was easy to operate and could be used for detection of MRSA in parallel to the blood culture with less sensitivity for detection of bacteremia and pediatric septicemia with low counts of MRSA.

Fabrication of DNA nanotubes with an array of exterior magnetic nanoparticles.

Described here a methodology for arraying of magnetic nanoparticles (MNPs) on the surface of DNA nanotubes (DNTs). Positioning of magnetic nanoparticles at exterior surface of DNTs were shaped after self-assembling of oligonucleotide staples within an M13mp18 DNA scaffold via an origami process. The staples were partially labeled with biotin to be arrayed at the surface of DNTs. Gel retardation assay of the DNTs carrying magnetic nanoparticles indicated a reversely behavioral electrophoretic movement in comparison to the nanotubes have been demonstrated previously. Also, high resolution transmission electron microscopy confirmed positioning magnetic nanoparticles at the exterior surface of DNTs, correctly. Ultrastructural characteristics of these DNA nanotubes using atomic force microscopy demonstrated topographic heights on their surfaces formed through positioning of magnetic nanoparticles outside the tubules. This nanoarchitecture would be potential for multiple arraying of nanoparticles that those be useful as functionalized chimeric nanocarriers for developing novel nanodrugs and nanobiosensors.

Ultrastructural characterizations of DNA nanotubes using scanning tunneling and atomic force microscopes.

The potential applications of scanning tunneling microscopy and atomic force microscopy for the characterizations of DNA nanotubes in nanoscale have been described here. The nanotubes were designed using the Cadnano software according to M13 mp18 DNA as a scaffold. DNA nanotubes were fabricated using the origami technique assisted with ligase treatment subsequently. Transmission electron microscopy confirmed the morphology of DNA nanotubes. For the topographic characterization of DNA nanotubes, an atomic force microscope was used in comparison to a scanning tunneling microscope. The scanning tunneling microscopy results revealed a high-resolution topography of DNA nanotubes in the constant-current mode; however, more details of the self-assembly in DNA strands in nanotubes were explored by atomic force microscopy with contact mode (or constant height). Our findings suggested that those two microscopes could be candidates for ultrastructural characterizations of DNA nanotubes for obtaining two- and three-dimensional micrographs.