㞟✚໬MEMSᢏ⾡䛻䜘䜛⣽⳦䛾䝇䝖䝺䝇ᛂ⟅ゎ᫂䛸⣽⳦ྠᐃᢏ⾡䜈䛾ᛂ⏝
Identification of Legionella Species by Photogate-Type Optical Sensor
䕿Sawako Tanaka1, Yong Joon Choi1, Toshihiko Noda1, Makoto Ishida1, Kazuaki Sawada1, Hiromu Ishii1,Katsuyuki Machida2,Yasuhiko Nikaido3, Mitsumasa Saito3, and Shin-ichi Yoshida4

1Engineering, Toyohashi University of Technology, Aichi, Japan, Engineering, 2Tokyo Institute of Technology, Tokyo, Japan, 3Medical, University of Occupational andEnvironmental Health, Fukuoka, Japan, Clinic, 4Fukuoka Megumi Hospital, Fukuoka, Japan
E-mail : tanaka-sa@int.ee.tut.ac.jpSummary

Experiment Results

This work describes simple method for sensing bacteria, Legionella by using a photogate-type
optical sensor and MEMS chip. We observed the behavior of fluorescence from Legionella
dumoffii (L. dumoffii) and Legionella erythra (L. erythra) when they are exposed to ultravioletlight. The time dependence of the fluorescence intensity of L. dumoffii and L. erythra obtainedwith photogate-type optical sensor agreed well with that of fluorescence intensity obtainedwith spectrometer, showing that each Legionella is able to be detected by photogate-type
optical sensor. Using the difference of their behavior, the identification of each bacterium
was successfully performed for a mixed bacterial system of L. dumoffii and L. erythra by thecombination of photogate-type optical sensor and optical filters.

This work describes the following two investigations:(1) Observation of respective fluorescence from L. dumoffii and L. erythra by the sensor
when they are exposed to UV light.
(2) Discrimination of L. erythra from a mixed system of L. dumoffii and L. erythra byusing the combination of PG-sensor and optical filters.

Introduction A Sensor for avoiding an outbreak of bacterial infection

Identification of Legionella species

Measurement system- Irradiation 1.2 mW/cm2
365 nm- Applied voltage Vsub, VPG, Iout䞉䞉䞉3VVwell 䞉䞉䞉GND

Cover glass
UV irradiation

Legionella

Legionella
PDMS

Biochip

Cultivation

SensorUbiquitous system

Development of a sensor that can detects bacteria without cultivation in a short time is desired.

Optical filter

L. dumoffii : blue fluorescence

What is Legionella ?

1μm[1] Ed. by S.Yoshida䠈Y.Yanagi䠈Y.Yoshikai䠖䛂Toda’s New Bacteriology䛃 Nanzando, 2013

Size : length 1-10μm, diameter 0.3-0.9μm
Infection : pneumonia
Habitat : Facilities using circulating water circulating water
Characteristic : Fluorescence emission
by ultraviolet light irradiation
Definitive diagnosis䠖 Culture method

λ…490 nm, φ0(t)؆݇ଵ …, ݇ଶ …

䞉The spectra have 3 clear peaks.
䞉We observed the photobleachingprocess of Legioliulin.

Method The combination of photogate-type optical sensor and MEMS ChipProcedure‫ࣅܵݍ‬‫ܫ‬ൌͳ െ ݁ ିఈௐ ࣘ૙ ሺ࢚ሻ݄ܿ

Rate constants
Spectrometer ݇ଶ …0.023Sensor݇ଶ …0.021

݇ଵ …, ݇ଶ …) Bacteria 2(λ…, φ0((t)؆݇
) ݇ଵ …,
L. erythra : red fluorescence݇ଶ …)

1. Put bacteria with beads in the chip
2. Set the chip on the sensor
3. UV irradiation
4. Legionella emits fluorescence
5. Detect fluorescence by the sensor
λ…677 nm, φ0(t)؆݇ଵ …, ݇ଶ …

Photogate-type optical sensor
䞉The spectra have 4 clear peaks‫ࣅܵݍ‬ͳ െ ݁ ିఈௐ ࣘ૙ ሺ࢚ሻ䞉We observed the photobleaching ‫ ܫ‬ൌ݄ܿ
process at 500, 600, 640 nm
䞉We observed the increases atRate constants
677 nm. This increase isprobably due to the production Spectrometer ݇ଵ…0.0013, ݇ଶ…0.0028
Sensor݇ଵ …0.0019, ݇ଶ …0.0022
of new fluorescent material.

• Potential diagram of the sensor• Schematic cross-section• Absorb UV excitation

The whole change• Photocurrent produced by Legionella fluorescence• Bird's eye viewn-sub contact

UV irradiation (a. u. )p-well contact
Sensing area
Output contact‫ࣅܵݍ‬‫ܫ‬ൌͳ െ ݁ ିఈௐ ࣘ૙ ሺ࢚ሻ݄ܿ

With a long pass optical filtera : Absorption coefficients : Sensing areah : Planck's constantq : Elementary chargeϕ : Intensity of light
W : Depth
λ : Wavelength
I : Photocurrent

Mixture of L. dumoffii & L. erythra

Photogate contact
Depth of Si (nm)

It is necessary to know characteristic parameters: wavelength λ and intensity φ0(t).

How to identify ?
• Chemical kinetic analysis• Use λ and rate constants‫ࣅܵݍ‬ͳ െ ݁ ିఈௐ ࣘ૙ ሺ࢚ሻ݄ܿ

Photo intensity

Photo intensity‫ܫ‬ൌ

Wavelength

Changes in substances
inside bacteria

ARate equation
ௗ୅ൌ − ݇ଵ ൈA
ୢ୲Time௞B䠄t䠅=‫ܣ‬଴ ൈ భ (exp(− ݇ଵ t) − exp(− ݇ଶ t))௞మ ି௞భBacteria 1(λ…, φ0(t)؆݇ଵ …, ݇ଶ …)
Bacteria 2(λ…, φ0(t)؆݇ଵ …, ݇ଶ …)

Starting materialCompareୢ୆ൌ ݇ଵ ൈA− ݇ଶ ൈ ୢ୲ୢ஼ൌ ݇ଶ ൈ ୢ୲

݇ଵFluorescent materialB݇ଶThe reaction product

CBoundary condition䠖
Break nutrients in a pure water

When t՜ λǡ

A=B=0, C=଴Time change of each substanceA䠄t䠅=଴ ൈexp(− ݇ଵ t)
௞భB䠄t䠅=‫ܣ‬଴ ൈ ௞ ି௞(exp(− ݇ଵ t) − exp(− ݇ଶ t))
మC䠄t䠅=଴ ൈభ௞భ ௞మଵଵൈexp(− ݇ଶ t) − ൈ exp(− ݇ଵ t)) ൅଴௞భ௞మ ି௞భ ௞మ(‫ࣅܵݍ‬‫ܫ‬ൌͳ െ ݁ ିఈௐ ࣘ૙ ሺ࢚ሻ݄ܿRate constants
Spectrometer ݇ଵ …0.0012, ݇ଶ …0.0014
Sensor݇ଵ …0.0013, ݇ଶ …0.0014

L. erythra cells in the bacterial mixed system were identified
by using a combination of the sensor and an optical filter.