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Functional expression of olfactory receptors using cell-free expression system for biomimetic sensors towards odorant detection

Chen, Fangming, Wang, Jian, Du, Liping, Zhang, Xu, Zhang, Fan, Chen, Wei, Cai, Wen, Wu, Chunsheng, Wang, Ping
Biosensors & bioelectronics 2019 v.130 pp. 382-388
Escherichia coli, Nematoda, biomimetics, biosensors, capacitance, detection limit, detergents, diacetyl, ligands, models, odor compounds, olfactory receptors, oligonucleotides
How to obtain sufficient functional olfactory receptors and coupled to transducers with high efficiency are crucial to biomimetic olfactory-based biosensors. In this study, a cell-free expression system was employed to prepare functional olfactory receptors that were utilized as sensitive elements for biomimetic olfactory receptor-based biosensors. A nematode olfactory receptor, ODR-10, was used as a model of olfactory receptors and expressed in Escherichia coli (E. coli) cell-free expression system. To improve the coupling efficiency and obtain the on-chip purification, a His6-tag was expressed as a fusion to ODR-10, which makes the expressed ODR-10 capable of selectively binding to the sensor surface modified with anti-His6-tag aptamers. Electrolyte-insulator-semiconductor (EIS) sensors were utilized as the transducer to measure the capacitance changes induced by the ODR-10 responding to its natural ligand, diacetyl. The results show that ODR-10 was successfully expressed using E. coli cell-free expression system and the expression could be promoted by adding 0.5% Brij58 as the detergent. Capacitance measurement results indicate that this olfactory receptor-based biosensor can detect diacetyl with high specificity and sensitivity. Concentration-dependent linear response to diacetyl ranging from 0.01 nM to 1 nM was obtained. The detection limit was as low as 0.01 nM. All the results demonstrated that the cell-free expression system provides a new approach for the preparation of functional olfactory receptors, which have great potential to be applied in biomimetic sensors towards chemical sensing.