Date: 24th July 2020
Diagnostic testing has become a critical feature of standard medical practice – with timely and accurate diagnosis giving patients the best opportunity for a positive health outcome. However, many diagnostic tests are invasive and the turn around time for results can be slow. Now scientists have developed nanoparticle sensors that can diagnose lung disease from exhaled biomarkers in breath.
Breath is an easily accessible and potentially informative clinical analyte because it can be sampled non-invasively and contains a plethora of trace volatile organic compounds (VOCs) called metabolites. However, this route of clinical detection or monitoring of diseases has remained largely overlooked due to challenges in the identification of biomarkers.
Now scientists from the Massachusetts Institute of Technology, US, have generated a class of nanoscale agents called volatile-releasing activity-based nanosensors (vABNs) which have been designed to sense proteases in the lungs and can monitor and detect respiratory diseases such as bacterial pneumonia and alpha-1 antitrypsin deficiency, a genetic disorder.
The team, led by Sangeeta Bhatia, have been developing nanoparticle sensors that can be used as synthetic biomarkers for several years. By coating nanoparticles with peptides which are released by a specific protease associated with disease, they have developed a pregnancy type urine test for a range of conditions such as pneumonia, ovarian and lung cancer.
However, now the team wanted to turned their attention to developing biomarkers in the breath, which would allow a more rapid test, and would be better suited for patients experiencing say dehydration, where urine samples are not easy to collect.
Using their previous nanoparticles as the foundation, the Bahtia group here chemically modified the peptides attached to the nanoparticles. They attached volatile molecules, which when cleaved by the disease-associated protease, released hydroflouramine gases into the air. This reporter gas was then detected in the breath using mass spectrometry.
As a proof-of-concept, the researchers tested the vABNs in mice models for bacterial pneumonia and alpha-1 antitypsin deficiency. The volatile reporters were designed to be cleaved by neutrophil elastase, an inflammatory-associated protease, which is produced by activated immune cells in both of these diseases.
The nanosensors were delivered intrapulmonary (via intratracheal injection) into both sets of lung disease mice. The reporters were released and expelled in breath at levels detectable by mass spectrometry with high sensitivity. Neutrophil elastase activity was detected within around 10 minutes post delivery, indicating that the vABNs were a feasible method to detected lung diseases with a protease component.
The team then went on to test whether the method could be used to monitor disease progression in these mouse models and whether it could used to assess the efficacy of treatments. Serial breath tests were used to monitor the dynamic changes in neutrophil elastase activity during lung infection. Furthermore, the sensors were able to successfully monitor the effectiveness of a protease inhibitor therapy which targetted neutrophil elastase for both pneumonia and alpha-1 antitrypsin deficiency.
Conclusions and future applications:
The team here have demonstrated the effective use of vABNs as a non-invasive method of detecting lung disease from the breath. Furthermore, the nanosensors could prove a useful tool for monitoring disease progression and could be used to determine the efficiency of treatments, which could then be adapted as required.
However, as with any new technology safety concerns will be high priority. This is an area that will require extensive testing however, early indications from the mouse experiments suggest the nanosensors were well tolerated and that little lung toxicity occurred.
The team are also hoping to develop an aerosol delivery system such as we’ve seen evolve for CRISPR delivery to the lungs. In addition, they are working on the detection device, here mass spectrometry was used, but the team are hoping to develop an easy to use, hand held type detector such as a smart mirror or breathalyser type machine. This will ensure flexibility of testing and it is hoped this may even extend its use to a home environment.
The development of diagnostic biosensors is a rapidly accelerating field, we have seen the development of ultra-sensitive biosensors which detect nucleic acids using crumpled graphene and are able to detect cancer markers in patient blood or serum, the in-field diagnostic biosensors CRISPR-Chip which detects genetic mutations, and simple lateral flow assays to detect early signs of infection and rejection following organ transplants or detection of SARS-CoV-2. However, the work presented here offers an advancement in breath tests, which is currently limited.
It is hoped that this nanosensor technology can transform the measurement of disease progression in vivo in a non-invasive manner. Indeed, the tech is well-placed for progression into clinical trial as Bhatia is co-founder of Gympse Bio, a company focused on measuring disease trajectory by querying biological activity through this novel technology – activity-based sensors that are bioengineered and tuneable to any protease-mediated disease.
Chan, L. W., M. N. Anahtar, T.-H. Ong, K. E. Hern, R. R. Kunz and S. N. Bhatia (2020). “Engineering synthetic breath biomarkers for respiratory disease.” Nature Nanotechnology.