Odorant Biosensors Research Articles

Feasibility Study of Odor Biosensor Using Dissociate Neuronal Culture with Gene Expression of Ionotropic Odorant Receptors

We propose a highly sensitive and real-time odor biosensor by expressing ionotropic odorant receptors of insects into dissociated cultures of neurons of rats. The odorant-gated ion channel structure of insect odorant receptor is expected to allow easy functional expression into cells. The neuronal dissociated cultures of rats have two significant advantages: a long lifetime comparable to rats, i.e., a few years; and amplification ability from weak ionic currents of odorant receptors into easily detectable action potentials of neurons. In the present work, in order to show the feasibility of the proposed sensor, we attempt to express the pheromone receptors of silkmoth, Bombyx mori, into cultured neurons of rats. We demonstrate that 10% of neuronal cells transfected using Lipofectamine successfully expressed pheromone receptors, and that these cells showed significant increase of calcium signals by 50% at the presentation of pheromone.

The feasibility study of novel odor biosensor using dissociate neuronal culture expressing ion channel built-in odor receptors

Pheromone-binding proteins (PBP) supply olfactory neuron cells with pheromones by binding the ligands they are tailored for and carrying them to their receptor. The function of a PBP as an efficient carrier requires fast ligand uptake and release. The molecular basis of the ligand-binding mechanism was addressed here for the intriguing case of the PBP of the silk moth Bombyx mori. This PBP completely encapsulates its ligand bombykol without displaying any obvious ligand entrance/exit sites. Here, two opposite dissociation routes were identified as the most likely entrance/exit paths by replica-exchange molecular dynamics, essential dynamics, and force-probe molecular dynamics simulations. One of the paths runs along a flexible front lid; the other along the termini at the back. Calculated forces and energies suggest that both routes are physiologically relevant. The multiplicity of pathways may reduce or tune the entropic barrier for ligand binding.

Study of Langmuir and Langmuir−Blodgett Films of Odorant-Binding Protein/Amphiphile for Odorant Biosensors

To make ultrathin films for the fabrication of artificial olfactory systems, odorant biosensors, we have investigated mixed Langmuir and Langmuir-Blodgett films of odorant-binding protein/amphiphile. Under optimized experimental conditions (phosphate buffer solution, pH 7.5, OBP-1F concentration of 4 mg L(-1), target pressure 35 mN m(-1)), the mixed monolayer at the air/water interface is very stable and has been efficiently transferred onto gold supports, which were previously functionalized by self-assembled monolayers (SAMs) with 1-octadecanethiol (ODT). Atomic force microscopy and electrochemical impedance spectroscopy were used to characterize mixed Langmuir-Blodgett (LB) films before and after contact with a specific odorant molecule, isoamyl acetate. AFM phase images show a higher contrast after contact with the odorant molecule due to the new structure of the OBP-1F/ODA LB film. Non-Faradaic electrochemical spectroscopy (EIS) is used to quantify the effect of the odorant based on the electrical properties of the OBP-1F/ODA LB film, as its resistance strongly decreases from 1.18 MOmega (before contact) to 25 kOmega (after contact).

Elaboration of odorant biosensors based on Langmuir-Blodgett technique

The advent of electronic noses opened a new kind of analytical approach, which offers an easy, quick, and cheap measurement comparing to conventional analytical approaches. It has potential applications on many different fields, such as assessment of various foodstuffs and beverages, environmental contamination monitoring and medical diagnostics etc. In this study, we used odorant binding protein (OBP) as odor-sensing material for developing such kind of artificial odorant biosensor. And biological films of OBP-1F (rat OBP) were deposited by Langmuir-Blodgett (LB) technique on gold electrode previously functionalised with 1-octadecanethiol (ODT) by self-assembled monolayers (SAMs). It is known that successful immobilization of the Langmuir-Blodgett films depends strongly on the characteristics, particularly stability, of the corresponding Langmuir films at the air/water interface. Hence the characteristics of monolayer of amphiphile octadecylamine (ODA) and the mixed monolayer of ODA/OBP were studied. Electrochemical impedance spectroscopy (EIS) was used to monitor the response of the system to a specific odorant molecule, isoamyl acetate.