Saturday, January 29, 2022

Magnetic Nanoparticles for SARS-CoV-2 and Other Virus Detection Systems

A recent article by Dr. Ramya Dwivedi, Ph.D. (National Chemical Laboratories in Pune, India) provides insights into functionalizing nanoparticles with different molecules of biological interest, and studying the reaction system and establishing useful applications. 

In light of the current coronavirus disease 2019 (COVID-19) pandemic caused by the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), researchers have become increasingly interested in novel technologies that could help quickly diagnose viral infections.

In a recent Talanta review article, researchers discuss the contributions that have been provided by magnetic nanoparticles for the molecular diagnosis of human viruses.


Nanotechnology-based techniques are adaptable and reliable in detecting diseases caused by viruses. Solid lipid nanoparticles, liposomes, inorganic nanoparticles, and polymeric nanoparticles are some of the most widely used advanced materials that are used in nanotechnology.

Nanoparticles allow researchers to conduct analyses at both cellular- and molecular-scale, which has supported their crucial role in various diagnostic advancements. For example, nanoprobes designed to recognize specific molecules have helped identify targets, even when present at low concentrations.

The present review focuses on the role of magnetic nanoparticles (MNPs) in identifying viruses, wherein the researchers provide insight into novel diagnostic methods that overcome many of the limitations associated with conventional diagnostic approaches.

Limitations of conventional systems

The technique used to diagnose the presence of a specific virus has often been specific to each virus; however, one of the most common assays includes the reverse-transcriptase polymerase chain reaction (RT-PCR). In addition to being the gold standard for diagnosing COVID-19, RT-PCR has also been used to detect the Marburg virus, Ebola virus, human immunodeficiency virus (HIV), hantavirus (HPS), influenza virus, and dengue virus.

In addition to RT-PCR, enzyme-linked immunosorbent assays, rapid antigen testing, immunofluorescence assays, and other forms of serological testing have also been used for conventional virus detection purposes.

Despite their clinical utility, many of these conventional techniques are associated with several limitations including the need for mass-testing kits, robust sensitivity capabilities, length completion requirements, and experienced personnel. For example, some of the requirements for RT-PCR in the diagnosis of COVID-19 include the refined extraction and accurate estimation of nucleic acids, which can lead to skewed results when performed by untrained personnel.  

Furthermore, despite the availability of marketable kits that are easy to use, despite their high costs, and typically yield better ribonucleic acid (RNA) quality, accessibility to these kits during the pandemic was affected as a result of supply chain interruptions.

Taken together, there is a pronounced motivation to advance alternative diagnostic approaches that address these challenges, while also eliminating the hazard of handling live viruses and its associated biological safety requirements.

Nanoparticles in viral diagnosis

Many nanomaterials including MNPs, quantum dots (QDs), silicon nanowires (SiNWs), virus-like particles (VLPs), graphene, inorganic nanoparticles, liposomes, nanoparticles of self-assembled protein, polymers, and metal, silica nanospheres, as well as carbon nanotubes (CNTs), nanostructured surfaces and films are utilized for viral diagnostic purposes. Many of these nanomaterials are associated with unique properties including bioavailability, optimum tunable size, charge, shape, biodegradability, high surface plasmon resonance (SRP), photon exchange, superparamagnetism, luminescence, biocompatibility, immunocompatibility, and tolerability, all of which can be attractive characteristics for viral detection applications.

The ability to manipulate the surface of nanomaterials using functionalization chemistry further supports the utility of these materials useful for both diagnostic and therapeutic purposes.

Importantly, nano-based detection systems, along with extraction, offer several advantages as compared to conventional diagnostic approaches. These systems allow for the easy, rapid, highly sensitive, and label-free detection of viruses that will undoubtedly advance point-of-care (POC) nanodiagnostics in clinical practice.

MNPs and virus diagnosis

Among the numerous inorganic nanoparticles including gold, silver, and iron oxide that have been widely studied over the past several years, MNPs are often utilized for nucleic acid extraction, purification, and detection.

Some of the advantages associated with MNPs for these applications include their ability to magnetically control their accumulation, superparamagnetic behavior, inexpensive preparation, quick isolation inside buffer solutions, and sensitivity for signal detection of the signal. Taken together, these properties of MNPs allow for the purification, pre-concentration, and separation of nucleic acids to be completed quickly, all the while retaining specificity during the viral detection process.

MNPs also play an important role in real-time detection systems when combined with a fluorescent or chemiluminescent probe. For these applications, the morphology, functionalization, surface coating, and properties of MNPs are highly tunable, thereby allowing researchers to attach a wide range of groups to MNPs to increase their chemical functionality, constancy, wettability, and bonding adaptability for numerous applications.

MNPs in the diagnosis of COVID-19

Zinc ferrite (ZNF) MNPs functionalized by carboxylic group polymers, as well as multifunctional chitosan-coated lithium zinc ferrite MNPs integrated with graphene oxide MNPs (CHLZFO-GO MNC), have been used for the extraction of RNA to ultimately detect SARS-CoV-2 in patient samples.

By extracting viral RNA through these methods before the RT-PCR testing, researchers can effectively reduce the risk of false negatives. This type of advanced approach to RNA isolation from nasal swabs can also expand the ability to rapidly diagnose COVID-19 at much larger scales.

MNPs have also been studied for their ability to enhance the sensitivity of biosensing devices for the rapid detection of the SARS-CoV-2 spike protein and single-stranded RNA (ssRNA) obtained from biological samples including blood, urine, and serum. One such example is the giant magnetoresistive (GMR) biosensing device, which has the potential to provide quick and consistent detection of pathogens like SARS-CoV-2 to reduce the uncertainty during viral incubation periods.

Another biosensing application of MNPs for SARS-CoV-2 diagnostic purposes includes the use of functionalized MNPs, followed by a measurement of their magnetic response in an AC magnetic field. To this end, functionalized MNPs were used as sensors to detect mimic SARS-CoV-2 containing spike proteins that are bound with polystyrene beads, which allowed for a quick detection time that does not compromise on its sensitivity for SARS-CoV-2 detection.

To resolve some of the challenges associated with the labor-intensive requirements of current molecular analytical processes, MNPs that have been functionalized with poly (amino ester) bonded to carboxyl groups (pcMNPs) have been studied for RNA extraction techniques.

The complex of pcMNPs with RNA samples can immediately be used for RT-PCR reactions, thereby reducing the time constraints of this process to about 20 minutes. In addition to being a more rapid approach to RT-PCR analysis for COVID-19 diagnoses, this approach utilizing pcMNPs also provides a 10-copy sensitivity.  


The present review provides insights into MNP strategies that have been designed for specific and non-specific viral diagnostic approaches. Importantly, various studies have looked to how MNPs can be incorporated into each step of the viral diagnosis process including extraction and purification to enrichment and detection of pathogens.


Friday, January 28, 2022

Scientists Develop Non-invasive Sensor that Changes Color if a Wound Becomes Infected

Scientists at Queen’s University Belfast have invented a tiny indicator that changes colour if a patient’s wound shows early signs of infection.

The non-invasive indicator, which is around the same size as one of our fingertips, is the first of its kind. It does not make any contact with the wound but detects the beginnings of infection by sniffing the air above it.

It can be added to already existing bandages and allows infections to be detected without taking off the dressing – something which can inhibit the healing process and increase the likelihood of wound infection.

It is estimated that around 1 to 2 per cent of people in developed countries will experience a chronic wound in their lifetime and in the UK £3.2 billion is spent each year treating the problem.

Professor Andrew Mills from the School of Chemistry and Chemical Engineering at Queen’s has been leading the project, alongside colleagues from the School of Pharmacy and School of Electronics, Electrical Engineering and Computer Science. The project was funded by the Engineering and Physical Research Council, which is part of UK Research and Innovation. The research findings have been published in the Royal Society of Chemistry’s ChemComm journal.

“Usually if a patient has a wound, especially a chronic wound, a nurse or doctor will check for infection every two to three days by removing the dressing. Changing a dressing can be unnecessary, painful and an infection risk.  All of this could be avoided with our indicator, saving time, money and pain.”

Explaining how the indicator works, Professor Mills says: “If infection is starting in a wound, there is often a sudden growth of aerobic microbiological species and as they grow they generate carbon dioxide. 

“Our indicator detects this rise in carbon dioxide causing the dot to change colour, flagging the infection in its very early stages before it actually takes hold and overwhelms the patient’s immune system. This means it can be treated quickly, avoiding unnecessary pain for the patient and significantly reducing the possible need for hospitalisation.”

Professor Brendan Gilmore from the School of Pharmacy at Queen’s says: “This sensor can provide an early warning of infection before it has progressed to a chronic, persistent colonisation of the wound by microorganisms which are by then much more difficult to treat effectively with antibiotics. 

“The sensors respond quickly to the presence of infection, and allow healthcare providers to make informed decisions about managing the wound, including whether or not to use antibiotics. Inappropriate antibiotic use is known to drive the emergence of antibiotic resistance. Crucially, these sensors can tell us whether or not the intervention has worked in killing the microorganisms which caused these infections.”

The project is entering the next phase where an app will be developed so that the patient will be alerted if there is an infection. The same information would also be sent to the patient’s nurse or doctor and be used to inform treatment plans.

Professor Mills says: “We are very pleased to now have our research findings published and to be able to offer a simple, inexpensive, non-invasive way to monitor the progress of healing wounds. We are currently in discussions with industry in how to take this forward and we hope to run clinical trials soon."

Source: SelectScience