Intelligent gelatin: an engineered material for smelling

A research team at UCIBIO in Lisbon NOVA School of Science and Technology (FCT-NOVA), led by Cecília Roque, showed that gelatin can be more than food. For the first time, it was shown an example of soft matter in artificial olfaction, where engineered gelatin materials combined with artificial intelligence tools were used to mimic the sense of olfaction. The results of this research work are published in the scientific journal Materials Today Bio.

In olfaction, volatile compounds, which make up odors, bind to specialized olfactory proteins in the nose. These binding events result in electrical signals sent to the brain, where pattern recognition is performed and the odor is identified (Image 1). Electronic noses (e-noses) are intelligent gas sensing devices that mimic the sense of smell, mirroring the biological orchestra of olfactory proteins and the intricate brain computing processes used in odor recognition, by a combination of chemical sensors and artificial intelligence. Conventional e-noses use metal semiconductors and synthetic polymers for chemical sensing. However, these are associated with low selectivity and with a high carbon-footprint during production and operation. 

Recently, Cecília Roque’s research group introduced the concept of hybrid gels. In these gels, gelatin is combined with liquid crystals (ubiquitous in LCD flat-screens on televisions, laptops, or mobile phones) (Image 2), resulting in optical materials responsive to external stimuli, including odors. By implementing an automatic classifier of odors based on machine learning algorithms (one of the tools used in artificial intelligence), the study published shows that a gelatin hybrid gel can distinguish volatile compounds with very similar structures, such as acetone and ethanol. 
“The liquid crystals in the gels are ordered. However, in the presence of volatile compounds this order is disrupted, yielding typical optical signals to each odor, just like our digital fingerprint”, explains Carina Esteves, one of the first authors of the study. Gonçalo Santos, the other first author, adds that “to apply machine learning algorithms to these odor fingerprints and build an automatic classifier, we first taught the system which signals correspond to which odors; then, when the system is exposed to an unknown sample, it can accurately identify the odor”.
“This is the first report of an intelligent system for gas sensing employing gelatin-based materials. Our findings strengthen the importance of simple and widespread soft matter, as gelatin and liquid crystals, to design smart functional materials that respond to external stimuli. Although we explored the gels for artificial olfaction, an area increasingly relevant in the field of non-invasive clinical diagnostics, there are many other interesting applications, as for example in soft bioelectronics and robotics, or wearable devices" says Cecília Roque, coordinator of this study and also professor at FCT-NOVA. This research work was funded by the SCENT project, a grant awarded to Cecília Roque by the European Research Council (ERC).

https://www.sciencedirect.com/science/article/pii/S2590006418300401
 
Reference of the publication:

Carina Esteves*, Gonçalo M. C. Santos*, Cláudia Alves, Susana Palma, Ana R. Porteira, João Filho, Henrique M. A. Costa, Vitor D. Alves, Bruno M. M. Faustino, Isabel Ferreira, Hugo Gamboa, Ana C. A. Roque. 2019. Effect of film thickness in gelatin hybrid gels for artificial olfaction, Materials Today Bio, Volume 1, January 2019, 100002. https://doi.org/10.1016/j.mtbio.2019.100002

About SCENT: The main objective of SCENT is to develop tools for rapid identification of bacterial infections. Recent works demonstrate that fast microbial identification is possible with chemical nose sensors but present limitations and require aggressive conditions during operation. Bioinspired nose sensors are an alternative but very complex and with low stability. The class of stimulusresponsive gels developed by SCENT's team tackle these main challenges. The team is studying how these materials can detect and identify bacteria, in particular those most prevalent in human infections and associated with antibiotic resistance.
 
About Biomolecular Engineering Group: The Biomolecular Engineering Lab is led by Cecília Roque and composed by a multidisciplinary team dedicated to mimic and engineer biological systems. The group has expertise in combining molecular recognition with functional materials, which together find applications in Bioengineering fields.
 
About UCIBIO: The research unit on Applied Molecular Biosciences, UCIBIO, gathers a team of researchers who perform their work at the Universities of Porto and NOVA from Lisbon. Created on January 2015 is one of the 3 top performers in Biomolecular Sciences in Portugal. UCIBIO’s key strength lies on its broad scope of fundamental and applied research, standing at the interface of Chemistry, Biology and Engineering to address pertinent questions at atomic, molecular, sub-cellular and cellular levels, including cell-to-cell interactions and population evolutionary dynamics.