Yasufumi Mizuno

Flow-injection-type biosensor system for salivary amylase activity

The authors aim to establish a method that can quantitatively evaluate vital reactions to stress. We have been examining the correlation between stress and salivary amylase activity in order to verify its validity as a stress index. In order to quantify human stress, which changes over time, the relationship between stress and salivary amylase activity must be verified by fast and repeated analysis of salivary amylase activity. Standard biosensors are designed such that the enzyme immobilized on an electrode (enzyme electrode) and the substrate-dependent activity is measured. The reverse approach of measuring the alpha-amylase-dependent activity was adopted. We fabricated an amylase activity analytical system. Maltopentaose was selected as a substrate for alpha-amylase and a flow-injection-type device was used to supply maltopentaose continuously. alpha-Glucosidase, having relatively low enzyme activity, was immobilized on a pre-activated membrane so that it could be enclosed in a pre-column, Glucose oxidase, having higher enzyme activity, was immobilized on a working electrode so that it could function as an amperometric biosensor. A saliva-collecting device was fabricated to make saliva pretreatment unnecessary. As a result, an amylase activity analytical system was fabricated that enabled us to measure salivary amylase activity from 0 to 30 kU/l, with an R(2) value of 0.97. The time-course changes in the salivary amylase activities for 1 week were 5.1%, and the initial sensitivity remained nearly constant. Through this study, we were able to verify the possible development of the amylase activity analytical system.

Salivary amylase activity monitor used for stress evaluation

The authors have been focusing on the activity of alpha-amylase in saliva (salivary amylase) with the aim of developing a simple quantitative measurement technique to monitor human stress. However, measurement of enzymatic activity required a sufficiently enough volume of substrate and the realization of quantification also required some mechanism to control the reaction time. Based on this concept, a salivary amylase activity monitor consisting of the test strip, the salivary transcription device and an optical analyzer was fabricated. The calibration curve for the salivary amylase activity monitor obtained an R/sup 2/ value of 0.72. It was considered that the monitor could be used for the analysis of salivary amylase activity. In order to evaluate the monitor, salivary amylase activity was measured with a roller coaster ride as a mental stressor. A significant difference between salivary amylase activities were recognized in before the ride and after the ride, and it was confirmed that increasing or decreasing human stress levels could be perceived as rises and falls in salivary amylase activity.

Nonverbal Communication Tool for Children with Severe Motor and Intellectual Disabilities Using Biochemical Measurement

Children with severe motor and intellectual disabilities (SMID) find it almost impossible to communicate whether they are feeling comfortable or uncomfortable. Most of the children with SMID rely on medical care involving disposable-type life support devices such as tracheostomy tubes or gastric tubes. It is believed that the insertion and removal of these medical devices could cause extreme physical pain under certain circumstances. The authors have previously reported a hand-held type salivary amylase (AMY) activity monitor that can be used to evaluate the sympathetic nervous system. This report proposes a nonverbal communication procedure based on a biochemical measurement using AMY activity for children with SMID. The physiological conditions of these children were evaluated using a hand-held type AMY activity monitor that we fabricated. The AMY activity and heart rate of six subjects, who required daily insertion and removal of tracheostomy tubes or gastric tubes, were simultaneously measured before and after medical care. Apart from one subject who required a respirator due to severe cerebral palsy, the experimental results showed that the AMY value increased sharply by 200 400% after medical care compared to the resting state. Furthermore, the rate of change of AMY activity was 10 times larger than the change in heart rate. Therefore, it is suggested that using these biochemical measurements a nonverbal communication tool for children with SMID can be established