Biosensing Machine That Can Smell and Differentiate Odors Developed

Researchers from The University of Manchester and the University of Bari have developed a biosensor that can differentiate smells that are similar to each other. The machine can distinguish the smell of two similar objects such as spearmint or caraway.

The scientists have found a way to manufacture odorant binding proteins in quantities that can be used in the biosensor. Odorant binding proteins helps the nose perceive the different smells by reacting to the different type of chemicals around

The biosensor incorporate the proteins using a transistor. By doing so, the team were able to detect and measure the changes in current as the proteins reacted to odors. The system is incredibly sensitive with a detection limit that approaches that of the human nose.

The findings are published in the journal Nature Communications.

Research Identifies 10 Basic Categories of Odor

Researchers have classified 10 basic categories of odor. These categories describe the fundamental descriptors for the sense of smell. The categories are fragrant, woody/resinous, fruity (non-citrus), chemical, minty/peppermint, sweet, popcorn, lemon and two kinds of sickening odors: pungent and decayed.

The sense of smell (olfaction) utilizes sensory cells of the nasal cavity. Odor molecules bind to specific sites on the olfactory receptors which sends the signal to the brain for processing. These signals are then interpreted by the brain into the odor categories described above. Just like with the sense of taste, these descriptors can be combined to form complex odors.

Properties of the perceptual basis set W. (A) Plot of normalized odor descriptor amplitude vs. odor descriptor number for the basis vector W1. Each point along the x-axis corresponds to a single odor descriptor, and the amplitude of each descriptor indicates the descriptor's relevance to the shown perceptual basis vector. Colored circles show the seven largest points in the basis vector, and descriptors corresponding to these points are listed to the right. (B) Waterfall plot of the 10 basis vectors constituting W, used in subsequent analyses. Note that each vector contains many values close to or equal to zero.
Credit: Castro JB, Ramanathan A, Chennubhotla CS (2013) Categorical Dimensions of Human Odor Descriptor Space Revealed by Non-Negative Matrix Factorization. PLoS ONE 8(9): e73289. doi:10.1371/journal.pone.0073289