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Nanostructured zinc oxide platform for

mycotoxin detection

Biophysic Department

Faculty of Natural Sciences and Mathematics

Bogor Agricultural University2010

NoerhayatiNoerhayati RofiahRofiah G751090021G751090021

Superviser Dr. Akhirudin Maddu

Anees A. Ansari , Ajeet Kaushik, Pratima

R. Solanki, B.D. MalhotraBioelectrochemistry Journal 77 (2010) 7581


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Introduction

Electrochemical

immunosensors

for detection of :

desired proteins,

biomarkers,

biological toxins

bio-warfare agents

in critical situations,

food,

environment,

Pharmaceutical chemistry

clinical diagnostics

To obtain a sensitive,

compact and stable

immunosensorplatform

desired antibodies

should be directed

in a given

orientation on theelectrode

The selection

of a matrix for the

immobilization of

antibodies (Abs) is

extremely important toobtain desired

characteristics of an

immunoelectrode


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Introduction

Nanostructured

metal oxides rs

electrocatalytic,

piezoelectric, Photonic,

tunable size dependent

surface properties

attractive for biosensing

applications

Zirconium oxide,

titanium oxide,

tin oxide ,

cerium oxide,zinc oxide (ZnO)

interesting

properties

large surface to volume ratio,

high surface reaction activity,

high catalytic efficiency,strong adsorption ability


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Introduction

nanostructured

ZnO

high isoelectric point (IEP ~9.5) biocompatibility facilitate

immobilization of an enzyme and protein

friendly microenvironment for immobilizing negatively

charged antibodies(r-IgGs; IEP ~5.5)

non-toxicity

high electron transfer capabilitychemical stability

immunosensor for detectionof ochratoxin-A (OTA)

produce nephrotoxic,

tetratogenic,carcinogenic

and immune toxic

activity in several animal

species


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Fabrication of solgel derived nanostructured

ZnO film/electrode

1 g of zinc acetate dihydrate is dissolved in 10 ml ethanol.

Then 3 ml (1 M) solution of ammonium hydroxide (NH4OH) is

added at room temperature to maintain pH=910.

A white milky precipitate of Zn(OH)2 thus obtained is

centrifuged and is followed by washing with deionized water

until neutral pH is achieved. this precipitate is dispersed in

distilledwater and dilute HNO3 (1 M) in ambient conditions for

peptization.

A transparent viscous solution is obtained for film fabrication

on ITO (indium tin oxide) coated glass plate via dip-coatingtechnique.

These films are then allowed to dry at 400 C for about 1 h.


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Methods

Schematic of fabrication of BSA/r-IgGs/Nano-ZnO/ITO immunosensor


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e lt a i i

FTI pe tra f Na -Z O ele tr e (a), r-IgG /Na

Z O/ITO ele tr e (b) a BSA/r-IgG /Na -Z O/ITO

ele tr e ( )


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e lt a i i

X-ray iffra ti patter f lgel erive Z O film; i et h w

ab rpti pe tr m f lgel erive Na -Z O film


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e lt a i i

X-ray iffra ti patter f lgel erive Z O film; i et h w

ab rpti pe tr m f lgel erive Na -Z O film


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TujuanResults and discussion

Nano-ZnO/ITO film

r-IgGs/Nano-ZnO/ITO electrode

BSA/r-IgGs/Nano-ZnO/ITO electrode

SEM image


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Cyclic voltammetry studies

A) Cyclic voltammogram of bare ITO (a) solgel derived Nano-ZnO/ITO

electrode (b) r-IgGs/Nano-ZnO/ITO electrode (c) and BSA/r-IgGs/Nano-

ZnO/ITO electrode (d),


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B) DPV studies of solgel derived Nano-ZnO/ITO electrode (a), r-

IgGs/Nano-ZnO/ITO electrode (b) and BSA/r-IgGs/Nano-ZnO/ITO

electrode (c) in PBS solution (50 mM, pH =7.0, 0.9%

NaCl) containing 5 mM of [Fe(CN|6]3 and 5 mM of [Fe(CN|6]4


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C) CV of BSA/r-IgGs/Nano-ZnO/ITO electrode as a function of scan rate

(10100 mV/s1) in ascending order in PBS solution (50 mM, pH =7.0,

0.9% NaCl) containing 5 mM of [Fe(CN|6]3 and 5 mM of [Fe(CN|6]4


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D) Magnitude of cathodic and anodic response current as a function of

scan rate (10100 mV/s)


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Linear response curve of BSA/r-IgGs/Nano-ZnO/ITO immunosensor

obtained between OTA concentration and RCT value.


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Conclusion

solgel derived Nano-ZnO film can be used

for the immobilization of r-IgGs and BSA for

blocking nonspecific binding sites of r-IgGs

to detect OTA

Nano-ZnO electrode results in amplifiedelectrochemical signal due to strong r-IgGs-

OTA interaction occurring at the

immunoelectrode surface.

A good linear relationship between the

electron transfer resistance and OTA

concentration in the range, 0.0060.01

nM/dm3 with improved sensitivity and

detection limit etc has been obtaoined


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