An Overview of Recent Developments in Nanomaterial Based

7/30/2019 An Overview of Recent Developments in Nanomaterial Based

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ARUN.S .SIDDARTH

C E N T R E F O R E D U C A T I O N

C E N T R A L E L E C T R O C H E M I C A L R E S E A R C H

I N S T I T U T E ( C S I R - C E C R I )K A R A I K U D I , T A M I L N A D U

AN OVERVIEW OF RECENT

DEVELOPMENTS IN NANOMATERIALBASED ELECTROCHEMICAL BIOSENSORS


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WHAT ARE BIOSENSORS?

Biosensor: biological sensing element connected to atransducer to convert observed response into ameasurable signal, whose magnitude is proportional

to the concentration of a specific chemical or set ofchemcials

Divided into several categories based on the

transduction process, such as electrochemical,optical, piezoelectric, and thermal/calorimetric

biosensors


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ELECROCHEMICAL BIOSENSORS

A molecular sensing device which couples abiological recognition element to an electrodetransducer.

Amperometric or potentiometric transducers used.

Potentiometric devices: biorecognition processconverted into a potential signal

Amperometric devices: monitors current associatedwith reduction or oxidation of electroactive speciesinvolved in the recognition process.

Electrochemical biosensors- offer great promiseforbiomedical applications.


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NANOMATERIALS FOR ELECTROCHEMICALBIOSENSORS

Metal nanoparticles: isolable particles between 1 and 50 nm insize.

Nanoparticles :physical, electronic and chemical propertiesdifferent from those of bulk metals

High surface-to-volume ratio and novel electron transportproperties of nanostructures- strong influence of minorperturbations on electronic conductance.

Extreme smallness of nanomaterials- allow packing a hugenumber of sensing elements onto small footprint of array device.

Offer prospect of rapid and sensitive label-free bioelectronicsdetection, massive redundancy in nanosensor arrays

1D nanostructures like CNT, semiconductor or conductingpolymer nanowires- particularly attractive for bioelectronic

detection


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ENZYME ELECTRODES.

Enzyme electrodes: used for monitoring wide range ofclinically or environmentally important substrates

Establishment of satisfactory electrical communicationbetween the active site of the enzyme and the electrode

surface- major challenge [1] The redox center of most oxidoreductases is electrically

insulated by protein shell.

The enzyme cannot be oxidized or reduced at anelectrode at any potential.

The possibility of direct electron-transfer betweenenzymes and electrode surfaces could pave the way forsuperior reagentless biosensing devices

[1] Electroanalysis, 1997, 9, 661.


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CNT BASED ENZYME ELECTRODES

Aligned CNT trees : prepared by self assembly Act as molecular wires to allow electrical communication

between the underlying electrode and redox proteins. linking of aligned reconstituted glucose oxidase (GOx)

on the edge of SWCNT to an electrode surfacedemonstrated [2] Enzyme reconstitution on the end of CNT represents an

extremely efficient approach for plugging an electrodeinto GOx.

Interfacial electron transfer rate constant of 42 s-1

estimated for 50 nm long SWCNT. Edge plane defects at end caps- electron transfer at CNT

[2] Angew Chem. Int. Ed., 2004, 43, 2113.


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Assembly of SWCNT electrically contacted glucose oxidase electrode: linking the reconstituted enzyme, on the edge of the

FAD functionalized SWCNT, to the electrode surface.


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OTHER NANOMATERIAL BASED ENZYMEELECTRODES

Catalytic properties of metal nanoparticles- facilitatedthe electrical contact of redox centers of proteins withelectrode surfaces.

Gold nanoparticles: electron relays for alignment of

glucose oxidase on conducting supports and wiring itsredox center [3]

Platinum nanoparticles deposited onto CNT:improvements in detection of the enzymatically-liberatedperoxide species [4]

Dispersed iridium nanoparticles (2 nm diameter) ingraphite-like carbon: improved amperometric biosensingof glutamate [5]

[3] Science, 2003, 299, 1877[4] Anal. Chem., 2010, 76, 1083.

[5] Electroanalysis, 2007, 16, 54.


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IN-VIVO GLUCOSE MONITORING

Pair of nanoelectrodes separated with a small (20-60nm) gap connected by polyanaline/glucoseoxidaseFilm [6] IN-VIVO glucose monitoring

Electrodeposition within the channel betweenelectrodes- controllable route for preparingconducting polymer nanowire enzyme sensors [7]

[6] NanoLett, 2006, 4, 1785.[7] NanoLett, 2007, 4, 1237.


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ELECTROCHEMICAL IMMUNOASSAYS

Abnormal concentrations of certain proteins canindicate presence of cancers.

Highly sensitive enzyme electrochemical

Immunoassays developed [8] Rely on labeling of the antibody (or antigen) with an

enzyme which acts on substrate and generate anelectroactive product detected amperometrically.

Possible to use metal markers and redox tags forelectronic transduction of antigenantibodyinteractions in addition to enzyme labels.

[8] Trends Anal. Chem. 21, 213219.


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NANOMATERIALS FOR IMMUNOASSAYS

One-dimensional (1D) nanostructures likesemiconductor or conducting-polymer nanowires (NW)extremely attractive for designing high-density proteinarrays.

High surface-to-volume ratio and novel electrontransport properties and influence of minorperturbations on electronic conductance indicate greatpromise for label-free real-time protein detection

Possible to pack large number of antibody-functionalizedNW onto a remarkably small footprint of an array device[9]

Great promise for assays of multiple disease markers inultrasmall sample volumes.

[9] Science ,300, 1115.


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NANOWIRES FOR HYBRIDIZATIONMONITORING

Highly sensitive protocols for monitoring DNAhybridization or single viruses in connection to p-type silicon NW (SiNW) functionalized with PNAprobes or antibodies for influenza demonstrated [10]

Discrete conductance changes, characteristic of thebinding event observed at extremely low target

concentrations.

[10] Nano Lett. 4, 5155.


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DNA hybridization measurements at SiNW functionalized with PNA probes. (A) Real-time conductanceresponse to 60 fM WT DNA sample. The arrow marks the point in time when the sample was added.The inset shows a SEM image of a typical SiNW device with source (S) and a drain (D) indicated; scalebar is 1m. (B) Time dependent conductance in DNA-free solution; the arrow indicates the point in timewhen a new solution sample was added [13]

[13] Biosens. Bioelectron. 2006, 21, 1887-1892.


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NANOPARTICLES FOR CANCER MARKERDETECTION

Ultrahigh sensitivity of nanoparticle-basedelectrochemical sensing protocols: opens up possibilityof detecting cancer markers that cannot be measured byconventional methods.

Stripping voltammetry: useful for detecting metalnanoparticle tags due to accumulation(electrodeposition) step.

Use of gold nanoparticle tracers for stripping-basedelectrochemical detection of DNA hybridization andantibodyantigen interactions reported [11]

Relied on capturing the gold nanoparticles to hybridizedtarget or captured antigen, followed by dissolution andelectrochemical stripping measurement of metal tracer

[11] J. Pharm. Biomed. Anal. 19, 5374


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INORGANIC NANOCRYSTALS FOR PROTEINDETECTION

Inorganic nanocrystals offer electrodiverse population ofelectrical tags as needed for multiplexed clinical testing.

Use of different inorganic-nanocrystal tracers for multi-target electronic detection of proteins reported [12]

Four encoding nanoparticles (cadmium sulfide, zincsulfide, copper sulfide, and lead sulfide) used todifferentiate signals of four proteins or DNA targets inconnection with sandwich immunoassay along withstripping voltammetry of corresponding metals

Each binding event yielded distinct voltammetric peak,whose size and position reflected the level and identity,of the corresponding antigen or DNA target

[12] J. Am. Chem. Soc., 2003 125, 32143215.


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Simultaneous monitoring of multiple proteins in connection todifferent inorganic nanocrystal tags and electrochemical strippingtransduction [14]

[14] Anal. Chem. , 2003, 81, 71217129.


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CONCLUSION

One dimensional nanostructures: widely attractive for widerange of bioelectronic sensing applications.

The ability to modify nanowires and nanotubes with biologicalrecognition elements- high selectivity.

Successful utility of 1-D nanostructures requires newnanofabrication capabilities with proper interconnection,reproducible positioning of nanowires and nanotubes betweenclosely-spaced microelectrodes.

Proper attention to be given to interface of these devices withthe real world (sample delivery)

Nanomaterials-based electrochemical devices- expected tohave major impact upon clinical diagnostics, environmentalmonitoring, security surveillance, food safety.


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An Overview of Recent Developments in Nanomaterial Based