A pattern recognition artificial olfactory system based on human olfactory receptors and organic synaptic devices.

Neuromorphic sensors, designed to emulate natural sensory systems, hold the promise of revolutionizing data extraction by facilitating rapid and energy-efficient analysis of extensive datasets. However, a challenge lies in accurately distinguishing specific analytes within mixtures of chemically similar compounds using existing neuromorphic chemical sensors. In this study, we present an artificial olfactory system (AOS), developed through the integration of human olfactory receptors (hORs) and artificial synapses. This AOS is engineered by interfacing an hOR-functionalized extended gate with an organic synaptic device. The AOS generates distinct patterns for odorants and mixtures thereof, at the molecular chain length level, attributed to specific hOR-odorant binding affinities. This approach enables precise pattern recognition via training and inference simulations. These findings establish a foundation for the development of high-performance sensor platforms and artificial sensory systems, which are ideal for applications in wearable and implantable devices.

Hydrogel-based Bioelectronic Tongue for the Evaluation of Umami Taste in Fermented Fish.

Bioelectronic tongues based on umami taste receptors have recently been reported for versatile applications such as food analyses. However, their practical applications are still limited, partly due to their limited stability and non-specific responses in real sample environments. Herein, we have developed a hydrogel-based bioelectronic tongue for the sensitive assessment of umami intensity in fish extract samples. In this study, the T1R1 venus flytrap of an umami taste receptor was immobilized on the gold floating electrodes of a carbon nanotube-based field-effect transistor. A polyacrylamide conducting hydrogel film was further hybridized on the sensor surface via physical adsorption, which could provide a good physiological environment to maintain the activity of receptors due to its excellent hydrophilicity and biocompatibility. The bioelectronic tongue with a receptor-embedded hydrogel structure showed a sensitive detection of umami substances down to 1 fM, and it also had a wide detection range of 10-15-10-2 M for monosodium glutamate and disodium inosinate, which covers the human taste threshold. More importantly, the proposed sensor could significantly reduce the non-specific binding of non-target molecules to a carbon nanotube channel as well as exhibit long-term stability, enabling sensitive detection of umami substances even in fish extract samples. Our hydrogel-based bioelectronic tongue provides a promising platform for future applications such as the flavor evaluation of foods and beverages.

Eye-Mimicked Neural Network Composed of Photosensitive Neural Spheroids with Human Opsin Proteins.

An in vitro model, composed of the short-wavelength human opsins and rhodopsins, is created. Two types of photosensitive neural spheroids are transfected for selective reaction under bluish-purple and green lights. These are employed to two devices with intact neuron and neural-spheroid to study the interaction. By photostimulation, the photosensitive spheroid initiated photoactivation, and the signal generated from its body is transmitted to adjacent neural networks. Specifically, the signal traveled through the axon bundle in narrow gap from photosensitive spheroid to intact spheroid as an eye-to-brain model including optic nerve. The whole process with photosensitive spheroid is monitored by calcium ion detecting fluorescence images. The results of this study can be applied to examine vision restoration and novel photosensitive biological systems with spectral sensitivity.

Photosensitive Nanodiscs Composed of Human Photoreceptors for Refractive Index Modulation at Selective Wavelengths.

A photoreceptor on the retina acts as an optical waveguide to transfer an individual photonic signal to the cell inside, which is determined by the refractive index of internal materials. Under the photoactivation of photoreceptors making conformational and chemical variation in a visual cell, the optical signal modulation is demonstrated using an artificial photoreceptor-based waveguide with a controlling beam refraction. Two types of nanodiscs are made of human photoreceptor proteins, short-wavelength-sensitive opsin and rhodopsin, with spectral sensitivity. The refractive index and nonlinear features of those two photosensitive nanodiscs are investigated as fundamental properties. The photonanodiscs are photoactivated in such a way that allow refractive index tuning over 0.18 according to the biological function of the respective proteins with color-dependent response.

Bitter taste receptors protect against skin aging by inhibiting cellular senescence and enhancing wound healing.

BACKGROUND/OBJECTIVES: Bitter taste receptors are taste signaling pathway mediators, and are also expressed and function in extra-gustatory organs. Skin aging affects the quality of life and may lead to medical issues. The purpose of this study was to better understand the anti-skin aging effects of bitter taste receptors in D-galactose (D-gal)-induced aged human keratinocytes, HaCaT cells. MATERIALS/METHODS: Expressions of bitter taste receptors in HaCaT cells and mouse skin tissues were examined by polymerase chain reaction assay. Bitter taste receptor was overexpressed in HaCaT cells, and D-gal was treated to induce aging. We examined the effects of bitter taste receptors on aging by using ß-galactosidase assay, wound healing assay, and Western blot assay. RESULTS: TAS2R16 and TAS2R10 were expressed in HaCaT cells and were upregulated by D-gal treatment. TAS2R16 exerted protective effects against skin aging by regulating p53 and p21, antioxidant enzymes, the SIRT1/mechanistic target of rapamycin pathway, cell migration, and epithelial-mesenchymal transition markers. TAS2R10 was further examined to confirm a role of TAS2R16 in cellular senescence and wound healing in D-gal-induced aged HaCaT cells. CONCLUSIONS: Our results suggest a novel potential preventive role of these receptors on skin aging by regulating cellular senescence and wound healing in human keratinocyte, HaCaT.

Ultrasensitive Bioelectronic Tongue Based on the Venus Flytrap Domain of a Human Sweet Taste Receptor.

Sweet taste is an important factor that regulates calorie intake and contributes to food preferences in humans and animals. Therefore, the evaluation of sweet substances is essential for various fields such as healthcare, food, and pharmaceutical industries. Sweet tastants are detected by sweet taste receptors which are class C G-protein-coupled receptors. T1R2 venus flytrap (VFT) of the sweet taste receptor is known as a primary ligand-binding domain for sweet tastants. In this study, we developed an ultrasensitive artificial sweet taste bioelectronic tongue based on the T1R2 VFT of a human sweet taste receptor. Here, the T1R2 VFT of a human sweet taste receptor was successfully overexpressed in a bacterial expression system. A T1R2 VFT-immobilized carbon nanotube field-effect transistor with floating electrodes was exploited as an artificial sweet taste sensory system. Significantly, our T1R2 VFT-functionalized bioelectronic tongue could be used to detect solutions of sweet tastants down to 0.1 fM and selectively discriminate sweet substances from other taste substances. Furthermore, our device could be used to monitor the response of the T1R2 VFT domain of a sweet taste receptor to sweet substances in real food environments such as apple juice and chamomile herb tea. Moreover, our device was used to evaluate the inhibition and enhancement effects on sweet taste receptors by zinc ions and chamomile tea, respectively. In addition, our device demonstrated long-term storability and reusability. In this respect, our sweet taste bioelectronic tongue could be a promising tool for various basic research and industrial applications.

Correlation between in vitro binding activity of sweeteners to cloned human sweet taste receptor and sensory evaluation.

The human sweet taste receptor is a TAS1R2/TAS1R3 heterodimer. To investigate the correlation between the in vitro affinity of sweeteners with stably expressed human sweet taste receptor in HEK-293 cells and human sensory evaluation, the receptor-ligand activity of bulk (sucrose, D-fructose, and allulose) and high-intensity sweeteners (saccharin, rebaudioside A, rebaudioside M, and neohesperidin dihydrochalcone) was compared by analyzing the Ca2+ release. The relative potency of the sweeteners was identified over a wide concentration range for EC50s. Relative to sucrose, bulk sweeteners showed similar concentration ranges and potency, whereas high-intensity sweeteners exhibited lower concentration ranges and higher potency. The log of the calculated EC50 of each sweetener relative to sucrose by the in vitro affinity assay was positively correlated (r = 0.9943) with the molar relative sweetness reported in the previous literatures. These results suggested a good correlation between the in vitro activity assay of sweeteners and human sensory evaluation.

FET-based nanobiosensors for the detection of smell and taste.

Various nanobiosensors composed of biomaterials and nanomaterials have been developed, due to their demonstrated advantage of showing high performance. Among various biomaterials for biological recognition elements of the nanobiosensor, sensory receptors, such as olfactory and taste receptors, are promising biomaterials for developing nanobiosensors, because of their high selectivity to target molecules. Field-effect transistors (FET) with nanomaterials such as carbon nanotube (CNT), graphene, and conducting polymer nanotube (CPNT), can be combined with the biomaterials to enhance the sensitivity of nanobiosensors. Recently, many efforts have been made to develop nanobiosensors using biomaterials, such as olfactory receptors and taste receptors for detecting various smells and tastes. This review focuses on the biomaterials and nanomaterials used in nanobiosensor systems and studies of various types of nanobiosensor platforms that utilize olfactory receptors and taste receptors which could be applied to a wide range of industrial fields, including the food and beverage industry, environmental monitoring, the biomedical field, and anti-terrorism.