Nanotechnology for combating COVID-19 - and future pandemics?

The successful fight against infectious diseases takes place on three fronts: prevention, diagnosis and treatment. Some nanomaterials are known for their antimicrobial activity and in some cases even for combating viruses. So how can nanotechnology be used to slow down or even stop the further spread of the currently rampant coronavirus? And what nanotechnological applications could be valuable in combating future pandemics? These are the questions addressed by an international team in a recently published paper in the journal ACS Nano.

Simplifying test regimes

The importance of testing is undisputed among experts. Only in this way is it possible to isolate positive cases and thus prevent their further spread. From some studies (e.g. this study by the University of Geneva: Seroprevalence of anti-SARS-CoV-2 IgG antibodies in Geneva, Switzerland (SEROCoV-POP): a population-based study), it can now be estimated that between 250,000 and 400,000 people in Switzerland have been infected, but such numbers can only be confirmed by testing. Tests are carried out by means of nasopharyngeal swabs. The sample taken is then tested by a so-called reverse transcriptase polymerase chain reaction (RT-PCR) for RNA fragments specific for SARS-CoV-2. Gold nanoparticles are a possible nanotechnological alternative. These can be provided with antibodies, which in turn bind viral antigens. If this binding takes place, the gold nanoparticles accumulate, which leads to a colour change from red to blue. Such a test would be relatively inexpensive and provide results faster than the current test procedure, as it has to be evaluated in a laboratory. Such a test regime could be enormously useful, especially in poorer countries. Another faster and cheaper test alternative are graph-based field-effect transistors, biosensors with antibodies that bind to the characteristic spike proteins of SARS-CoV-2.
Although there are numerous other methods that could be considered, the authors point out that nanotechnological diagnostics is still in its infancy. However, the current pandemic may bring important findings and progress in this field that could prove important in the future.

Nanomedicine for treatment

Compared to a bacterial effect that can (normally) be treated with antibiotics, the coronavirus has revealed that no broad-spectrum antiviral agent exists. The paper sheds light on different possible intervention strategies, including improved drug delivery in the lung tissue or preventing the coronavirus from attaching to the so-called ACE2 receptors. Nanoparticles seem particularly suitable for penetrating deep into the alveoli of the lungs precisely because they are so small. However, this would have to take place in the form of aerosols, which means a strong dilution of the substances that are actually effective, thus reducing their effectiveness.
In a large number of the severe courses of COVID-19, a particularly strong reaction of the immune system was observed. Although an adequate immune response is naturally desirable and effective in the body's fight against unwanted invaders, by far not only viruses, it is also a very important part of the immune system. However, a disproportionate response of the immune system can also occur, in which too many substances are released or this reaction lasts for a long time. The phenomenon is known in the technical jargon as "Cytokine Storm" and can sometimes cause severe damage to the body. The importance of such uncontrolled immune responses has been recognised in the recent past and is being intensively researched accordingly. Nanotechnology could also be applied to this important lever to alleviate the course of the disease, for example through the efficient delivery of immunosuppressive drugs by nanocarriers, resulting in reduced doses and organ-specific distribution of the active ingredients. In addition to the more efficient use of drugs, it is hoped that this will also lead to fewer undesired side effects.

Prevention - last but not least

Prevention should actually be the first priority. However, whether and how the zoonosis could have been prevented is a different question, and so prevention means, in the case of an already ongoing pandemic, preventing its further spread. Modified surfaces offer a promising possibility here. Metallic nanoparticles made of copper, for example, release ions which in turn can have antiviral effects. Self-cleaning or even -disinfecting surfaces are a comparatively old and well-known nanotechnological application and are thus moving back to the front line. Nanotechnology can also prevent the spread of the virus by its application in protective equipment, for example by inactivating viruses or other microbes or by nanofibres in protective masks, which filter with high efficiency and can be used several times without losing their functionality.
Nanosilver masks are not recommended
Recently, protective masks have also become available that contain nanosilver, a substance with a well-known antibacterial effect. Whether the silver ions that are released are also effective against viruses, however, is still too little known. The limited benefit of these masks is offset by the possible negative effects of inhaling these particles. Due to a lack of data, a final risk assessment on this topic is not yet possible. Accordingly, in a recent statement, the German Federal Institute for Risk Assessment (BfR) has advised against the use of nanoscale silver in consumer products - in line with the precautionary principle.

Author: Alex von Wyl

Further reading (Q&A on the novel coronavirus from the BfR, in German only): Fragen und Antworten des BfR zum neuartigen Coronavirus
Sources: ACS Nano - Toward Nanotechnology-Enabled Approaches against the COVID-19 Pandemic
DAZ online - Nanosilber in Alltagsmasken: BfR warnt vor ungeklärten Risiken