Bioelectronic detector with monoamine oxidase for halitosis monitoring

Abstract

Methyl mercaptan (MM) is known as one of the major chemicals of halitosis (bad breath). In this study, a bioelectronic gas sensor (bio-detector) for gaseous MM was developed and was applied to measure halitosis in breath. The bio-detector consisted of a Clark-type dissolved oxygen electrode, a monoamine oxidase type-A (MAO-A) immobilized membrane and a reaction unit that had liquid and gaseous compartments separated by a hydrophobic porous polytetrafluoroethylene (PTFE) diaphragm membrane. The tip of the electrode covered with MAO-A membrane was placed into the liquid compartment as touching to the PTFE diaphragm membrane. In order to amplify the bio-detector output, a substrate regeneration cycle caused by coupling the monooxygenase with l-ascorbic acid as reducing reaction with reagent system, was applied. The results of MM vapor measurements showed the calibration range of the bio-detector for MM vapor was from 0.087 to 11.5 ppm (correlation coefficient: 0.993) and included the human sense of smell level 5 (0.2 ppm). The bio-detector had good selectivity being attributed to enzyme specificity was obtained for several substances (trimethyl amine, ammonia, dimethyl sulfide, etc.). The bio-detector was applied for halitosis measurement. Expired gases in five subjects were sampled every hour and the concentrations of MM in the expired gases were monitored. The output of bio-detector showed behaviour of halitosis level changes in a day such as increasing with passage of time and decreasing after eating.

A review of the current literature on aetiology and measurement methods of halitosis

“…109,110 Other promising chemical sensors for measuring ammonia and methyl mercaptan in breath air have been introduced lately. 111,112 Recently, a compact gas chromatograph with an indium oxide semiconductor gas sensor was developed. The apparatus measures each volatile sulphur-containing compound separately.…”

Halitosis: could it be more than mere bad breath?

“…Diabetes mellitus and especially diabetic keto-acidosis are characterized by a sweet ''fruity'' breath due to the accumulation of ketones (acetoacetate, b-hydroxybutyrate, and acetone) in the blood that are excreted through the respiratory system [16]. The principle cause of this sweet smell is the high levels of acetoacetate or acetone, the most abundant metabolite in alveolar air of patients with diabetes, and derived from decarboxylation of acetyl-CoA when lipolysis or lipid peroxidation occurs.…”

Halitosis: A Review of Current Literature

“…Chemical sensors, also known as electronic nose, could measure ammonia, methyl mercaptan compounds and each volatile sulphur-containing compound from breath air. The sensitivity of the sensors has positive correlation to gas chromatography and organoleptic scores (29,(44)(45)(46)(47).…”

“…Combined use of CHX and CPC resulted in both a reduction of aerobic and anaerobic bacterial load and a further decrease in VSCs level (46). In a study using a combination of zinc at 0.3% concentration and CHX at 0.025% concentration were observed to 0.16% drop at 1 hours, 0.4% drop at 2 hours, and 0.75% drop after 3 hours at H 2 S levels (64).…”