仿生嗅觉与味觉传感技术及其应用的研究进展

动物的化学感受系统具有惊人的能力,能够在极低的浓度下识别数千种分子结构各异的化学物质,其灵敏性、选择性和响应速度都远高于当前的人工识别系统.近年来,研究者致力于利用完善的天然分子识别机制,开发出一种与传统嗅觉/味觉传感器相比更具仿生意义的新型化学探测系统,即仿生嗅觉/味觉传感器.仿生嗅觉/味觉传感器通常将动物嗅觉味觉的受体、细胞和组织作为敏感材料,然后使用多种人工检测方法,如光学、电化学和声波检测器件等,实现对化学物质的检测和识别.文中概述了动物嗅觉/味觉感受系统对化学物质的信息处理机制,并结合本实验室的工作,综述了目前仿生嗅觉/味觉传感器的常用技术及其未来发展趋势,并展望了其在医疗、工业和军事等领域的应用前景.     

人工味觉及其模式识别

本文探讨了生物味觉的机理，研究了模拟生物味觉构造的人工味觉系统和用于对味觉物质敏感的生物类脂材料的特性、选择性及用生物类脂材料构成的多通道电极阵列式味觉传感器。针对基本的五种味觉物质，给出了有关测试结果以及一些有意义的结论。实验表明，上述方案可用于开发一种实用的新型味觉传感系统     

基于声表面波器件的仿生嗅觉受体传感器的研究

嗅觉受体可以与气味分子发生特异性的相互作用,这一机理不仅在生物嗅觉系统分辨和识别气味的过程中发挥着重要作用,而且也为解决传统嗅觉传感器特异性低的问题提供新的途径。从仿生设计角度,利用嗅觉受体对其配体特异性识别的机理,提高嗅觉传感器的特异性。以嗅觉受体作为敏感元件,声表面波器件作为二级传感器,构建一种可用于特异性气味检测的新型嗅觉受体传感器。选择秀丽线虫嗅觉受体ODR-10作为生物识别元件,通过基因工程的方法,将其表达在人乳腺癌细胞MCF-7细胞质膜上,提取含有ODR-10的细胞质膜组分,将其涂覆在声表面波器件的敏感区域。结果表明,ODR-10可以有效地表达于MCF-7的细胞质膜上,用这种异源表达的ODR-10构建的仿生嗅觉传感器对ODR-10的配体丁二酮具有很高的灵敏度,并具有很好的特异性。实验结果证实,这种基于嗅觉受体的仿生嗅觉传感器不仅适用于特异性气味检测,也适用于筛选特异性的嗅觉受体-配体对,将进一步推动嗅觉传导机理研究的进展。     

人工嗅觉——电子鼻的研究

本文对人工嗅觉－电子鼻进行了较全面的研究，包括人工嗅觉的神经生理学基础、新型嗅觉感受器的成膜技术、具有柔顺性的嗅觉感受器阵列的构造及人工神经网络在嗅觉的检测和识别中的应用。最后针对几种曲型的气味给出了有关实验结果。     

人工嗅觉───电子鼻的研究

本文对人工嗅觉电子鼻进行了较全面的研究，包括人工嗅觉的神经生理学基础、新型嗅觉感受器的成膜技术、具有柔顺性的嗅觉感受器阵列的构造及人工神经网络在嗅觉的检测和识别中的应用。最后针对几种典型的气味给出了有关实验结果。     

仿生嗅觉神经芯片的研究进展

嗅觉神经芯片是在电子鼻和细胞传感器研究的基础上，在芯片表面培养嗅觉感受神经元所构成的一种神经芯片。该技术是通过用微电极阵列等芯片技术记录气体分子作用于神经元膜表面嗅觉受体产生的动作电位而达到气体检测的一种更具仿生意义的生物电子鼻技术。在嗅觉生物学研究的基础上对嗅觉芯片的研究进行了综合论述，重点介绍了嗅觉细胞的培养和神经芯片技术等嗅觉芯片相关技术的研究进展。并对该领域的应用前景进行了展望。     

电子鼻技术在医学中的应用

目的:探讨电子鼻技术方法及其在医学中的应用。方法:电子鼻是利用气体传感器阵列的响应图案来识别气味的电子系统,通常由气味取样器、气体传感器阵列和信号处理系统三部分组成。介绍了电子鼻的发展状况、论述了通用电子鼻的组成、原理及所用的传感器(金属氧化物传感器、导电型聚合物传感器、压电型传感器等)的特性及其医学检测中的应用。结果:电子鼻可用于检测肺部疾病(肺癌、肺结核)、糖尿病、尿毒症和细菌感染(厌氧菌、耳鼻喉感染细菌、不同类型的金黄葡萄球菌、伤口微生物感染)。结论:电子鼻作为一种无创的、快速诊断技术在疾病的早期诊断筛查及微生物感染的快速检测方面具有重要的临床应用价值。     

仿生嗅觉神经芯片的研究进展

嗅觉神经芯片是在电子鼻和细胞传感器研究的基础上,在芯片表面培养嗅觉感受神经元所构成的一种神经芯片。该技术是通过用微电极阵列等芯片技术记录气体分子作用于神经元膜表面嗅觉受体产生的动作电位而达到气体检测的一种更具仿生意义的生物电子鼻技术。在嗅觉生物学研究的基础上对嗅觉芯片的研究进行了综合论述,重点介绍了嗅觉细胞的培养和神经芯片技术等嗅觉芯片相关技术的研究进展。并对该领域的应用前景进行了展望。     

基于微电极阵列的嗅球细胞网络传感器的研究

嗅球(OB)是嗅觉系统的第一中转站,在嗅觉信息的识别和处理中具有重要的作用.嗅球中具有多种类型的神经元,分别具有不同的生理特点和功能.本研究利用细胞培养技术,将嗅球神经元与微电极阵列(MEA)芯片耦合,构建一种细胞网络传感器,用于对多点的嗅球神经元电活动进行同步观察与分析.结果显示,MEA上培养的嗅球细胞生长良好,能够检测多个通道的嗅球神经元的自发电位以及谷氨酸作用下的诱发响应.研究表明,该嗅球细胞网络传感器能够实现信号的多通道同步检测及有效分辨神经元的自发信号和诱发响应,并且能够很好地捕捉不同通道神经元响应的特点.该研究对于进一步分析嗅觉信息在嗅球内的传导和编码具有重要的意义.     

基于LAPS的电子舌的设计与实现

目的：基于光寻址电位传感器（LAPS）的原理设计一种用于对酸、甜、苦、咸、鲜五种基本味觉物质进行测量的传感器系统。方法：基于味觉传感器阵列智能味觉识别系统—电子舌是一种利用多传感器阵列感测液体样品,然后集合信息融合算法对液体样品定性、定量识别的技术,它主要由传感器阵列、信号处理和模式识别系统组成。本文主要包括以下几个方面：介绍了LAPS的工作原理;阐述了TiO2溶胶—凝胶分子印记膜的制备方法,使用分子印迹膜技术制备的敏感膜,对味觉物质分子表现为高度的识别性,对光寻址味觉感知生物传感器阵列的研究具有重要的意义;设计出光寻址电位传感器（LAPS）味觉感知系统的硬件软件系统测试了五种味觉物质的响应信号;采用PCA以及人工神经网络算法对五种不同味觉物质响应信号进行模式识别。结果：通过该味觉感知系统测试样本中的五个味道样本的输出分别接近各自对应的期望输出,可以正确判别出五种味觉的结果,实现了对五种不同味觉物质的区分和检测。结论：味觉仿生感知技术的研究对人工智能的飞跃发展具有十分重要的意义,采用科学有效的检测技术手段来评价味觉品质是必然的发展趋势。因此,本文基于LAPS原理的电子舌系统的研究具有重要的应用价值和实际意义。     

Expiration: The moment we experience retronasal olfaction in flavor

Respiration is essential for smell perception. Previously we found that 8–12-Hz cortical rhythms were phase-locked to inspiration onset during the presentation of odor stimuli; this is referred to as inspiration phase-locked alpha band oscillation (I-α). Generators of I-α estimated with a dipole fitting model were found in the piriform, the entorhinal cortex (ENT), the amygdala (AMG), the hippocampus (HI) and the orbitofrontal cortex (OFC). Such olfactory perception is said to occur via the orthonasal olfaction route. Another route is the retronasal olfaction route. In this study, we investigated the link between respiration phase and retronasal olfactory perception. Electroencephalograph (EEG) and respiratory flows (separately measured with mouth and nose) were simultaneously recorded during stimulation of subjects’ tongues with liquids of chocolate, sucrose and water. The percentage of subjects correctly identifying the chocolate taste was higher when subjects were asked to breathe through the nose than when they were breathing through the mouth. In the averaged EEGs triggered by the onset of expiration measured from the flow through the nose, a 8–12-Hz oscillation was observed. Generators of this potential were found in the left ENT, HI, AMG and OFC in the order of milliseconds after expiration onset. Perception of retronasal olfaction is dependent on expiration, and combining retronasal olfactory information with gustatory information and somatosensation enable us to identify flavors when drinking and feeding.     

Architecture of odor information processing in the olfactory system

Since the discovery of the superfamily of approximately 1000 odorant receptor genes in rodents, the structural simplicity as well as the complexity of the olfactory system have been revealed. The simple aspects include the one neuron-one receptor rule and the exclusive convergence of projections from receptor neurons expressing the same receptors to one or two glomeruli in the olfactory bulb. Odor decoding in the olfactory cortex or higher cortical areas is likely to be a complicated process that depends on the sequence of signal activation and the relative signal intensities of receptors overlapping for similar but different odors. The aim of the present study was to investigate odor information processing both in receptors and in the olfactory cortex. At the receptor level, the similarity and difference in receptor codes between a pair of chiral odorants were examined using the tissue-printing method for sampling all the epithelial zones. In order to dissect odor-driven signal processing in the olfactory cortex by reducing cross-talk with the non-olfactory activities, such as cyclic respiration or other sensory inputs, an in vitro preparation of isolated whole brain with an attached nose was developed, and the methodologies and resulting hypothesis of receptor-sensitivity-dependent hierarchical odor information coding were reviewed.     

结合磁共振成像和脑机接口的新型在体生物电子鼻的研究

在体生物电子鼻利用了哺乳动物的嗅觉系统,因此具有很高的灵敏度和特异性,但在嗅球中植入电极的过程中其位置主要根据经验确定,因此成功率并不理想。利用锰离子的钙离子相似性和强顺磁性,在10只大鼠单侧鼻腔中滴入锰离子并给予气味刺激,进行磁共振扫描并标记出大鼠嗅球中的对特定气味的响应区域。在该区域中植入微丝阵列电极,记录电生理信号并就行神经信号解码,实验结果表明,受到该特异性气体刺激后,嗅球神经元的电生理信号中LFP信号β波能量增强,spike信号对该气体刺激也会有响应,并且有些通道的spike发放频率变化与刺激气体的浓度有较好的线性关系。此方法对乙酸异戊酯和正丁酸的检测下限分别为0.033和0.007 2 μM。第一次利用锰离子增强磁共振辅助定位的生物电子鼻,未来在爆炸物搜索、食品安全等方面都有广阔的前景。     

Mimicking the human smell sensing mechanism with an artificial nose platform

Sensing smell is a highly complex biological process, and characterizing and mimicking the interaction between the olfactory receptor (OR) protein and its ligands is extremely challenging. Herein, we report a highly sensitive and selective human nose-like nanobioelectronic nose (nbe-nose), which responds to gaseous odorants sensitively and selectively, has a signal specificity pattern similar to that in the cellular signal transduction pathway, and maintains an antagonistic behavior similar to the human nose. The human olfaction mechanism was mimicked by using carboxylated polypyrrole nanotubes (CPNTs) functionalized with human OR protein. The nbe-nose was able to detect gaseous odorants at a concentration as low as 0.02 parts-per-trillion (ppt), which was comparable to a highly trained, human expert’s nose. The nbe-nose can be used scientifically for smell mechanism studies. It can be also applied to various fields that rely on smell monitoring for industrial and public purposes.     

Morituri te salutant? Olfactory signal transduction and the role of phosphoinositides

During the past 150 years, researchers have investigated the cellular, physiological, and molecular mechanisms underlying the sense of smell. Based on these efforts, a conclusive model of olfactory signal transduction in the vertebrate's nose is now available, spanning from G-protein-mediated odorant receptors to ion channels, which are linked by a cyclic adenosine 3',5'-monophosphate-mediated signal transduction cascade. Here we review some historical milestones in the chronology of olfactory research, particularly emphasising the role of cyclic nucleotides and inositol trisphosphate as alternative second messengers in olfactory cells. We will describe the functional anatomy of the nose, outline the cellular composition of the olfactory epithelium, and describe the discovery of the molecular backbone of the olfactory signal transduction cascade. We then summarize our current model, in which cyclic adenosine monophosphate is the sole excitatory second messenger in olfactory sensory neurons. Finally, a possible significance of microvillous olfactory epithelial cells and inositol trisphosphate in olfaction will be discussed.     

Olfactometry in fMRI studies: odor presentation using nasal continuous positive airway pressure

We describe a method for generating and presenting olfactory stimuli in functional magnetic resonance imaging (fMRI) studies for humans. The olfactometer is based on principles of air dilution olfactometry and consists of a nasal mask and a nasal Continuous Positive Airway Pressure device, both normally used for patients suffering from obstructive sleep apnea syndrome. The system allows online monitoring and recording of the subject's breathing pattern. Switching between different olfactory conditions can easily be synchronized with the inhalation phase and be controlled by a computer. Besides, switching occurs rapidly and without any optical, acoustic, thermal, or tactile cues for the subject. As an example of implementation we present a fMRI trial of olfaction using pleasant and unpleasant odor stimuli to induce different affective states in healthy subjects. The relatively inexpensive olfactometer is reliable and permits constant odor concentrations during the inherently prolonged imaging studies.     

Behavioral and neural correlates of postnatal olfactory conditioning: I. Effect of respiration on conditioned neural responses

Following olfactory classical conditioning, infant rats exhibit a preference for the conditioned odor and exhibit enhanced uptake of focal 14C 2-deoxyglucose (2-DG) within the olfactory bulb. The present experiments assessed the role of respiration on the expression of the enhanced 2-DG uptake response. Pups were conditioned from postnatal day (PN) 1-18 with an olfactory stimulus paired with a reinforcing tactile stimulus which mimics maternal contact (Odor-Stroke). Control pups received odor only or tactile stimulation only. On PN 19, pups received 1 of 3 tests: 1) a two-odor choice test, 2) an odor/2-DG test with normal respiration allowed, or 3) an odor/2-DG test with respiration experimentally controlled. The results indicated that: 1) Odor-Stroke pups learned the conditioned odor preference, 2) Odor-Stroke, normally respiring pups exhibited enhanced olfactory bulb 2-DG uptake when compared to control pups. No difference in respiration rate was detected between groups in normally respiring pups. 3) Odor Stroke pups whose breathing was experimentally controlled exhibited enhanced olfactory bulb 2-DG uptake when compared to control pups with an identical number of respirations. Together, these results demonstrate that modified respiration during testing is not required for the expression of a modified olfactory bulb response to learned attractive odors. Therefore, the data suggest that the olfactory system itself is modified by early learning.     

Respiration and body movement analysis during sleep in bed using hetero-core fiber optic pressure sensors without constraint to human activity

We describe respiration monitoring in sleep using hetero-core fiber optic pressure sensors. The proposed hetero-core fiber optic sensor is highly sensitive to macrobending as a result of the core diameter difference due to stable single-mode transmission. Pressure sensors based on hetero-core fiber optics were fabricated to have a high sensitivity to small pressure changes resulting from minute body motions, such as respiration, during sleep and large pressure changes, such as those caused by a rollover. The sensors are installed in a conventional bed. The pressure characteristic performance of all the fabricated hetero-core fiber optic pressure sensors is found to show a monotonic response with weight changes. A respiration monitoring test in seven subjects efficiently demonstrates the effective use of eight hetero-core pressure sensors installed in a bed. Additionally, even in the case of different body postures, such as lying on one's side, a slight body movement due to respiration is detected by the hetero-core pressure sensors.     

Age-related changes in olfactory processing detected with olfactory event-related brain potentials using velopharyngeal closure and natural breathing.

Previous olfactory event-related potential (OERP) studies often employed the Velopharyngeal Closure (VC) method, which prevents respiratory air flow in the nose during odor presentation. However, the use of VC has limited the application of OERPs to populations able to perform this artificial breathing technique. The present study investigated the effects of Natural Breathing (NB) in comparison to VC on OERP latency and amplitude in young (mean age: 24 years) and elderly (mean age: 71 years) adults. OERPs were recorded from three midline scalp electrodes (Fz, Cz, Pz) for 15 trials in each breathing condition with an interstimulus interval of 3.5 min, using amyl-acetate as stimulus. Subjects were asked to report perceived stimulus intensity. A thermistor placed inside one nostril monitored nasal respiration and performance of VC. In the NB condition, subjects were instructed to breathe normally through mouth and nose, while stimulus presentation occurred during inspiration. In both breathing conditions, elderly subjects showed significantly smaller N1-P2 and N1-P3 interpeak amplitudes and longer latencies for N1, P2, P3 than younger subjects. VC generated significantly larger N1-P2 amplitudes across all electrode sites, whereas Natural Breathing produced a trend towards shorter P3 latencies. No significant interaction was found between age and breathing technique. The present investigation showed that the OERP is a sensitive measure for detecting age-related changes in olfactory function regardless of breathing technique.