MEVE 018: Unit 14 – Nanobioanalytical Techniques

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UNIT 14: NANOBIOANALYTICAL TECHNIQUES

14.0 Introduction

Nanobioanalytical techniques combine nanotechnology and biological analysis to detect, monitor, and understand biological systems at the molecular level. With advancements in miniaturization and sensitivity, these tools are revolutionizing diagnostics, environmental monitoring, and precision biotechnology. This unit explores key nanoscale technologies such as nanopore sequencing, nanowires, nanogold, and optofluidic sensor arrays—highlighting their working principles, synthesis, and environmental applications.

14.1 Objectives

After studying this unit, you should be able to:

  • Understand the principle and process of nanopore sequencing.
  • Describe nanowires and their synthesis.
  • Explain the properties of nanogold and surface plasmon resonance.
  • Understand nanoscale optofluidic sensors and their functioning.
  • Explore the applications of nanobioanalytical techniques in environmental monitoring.

14.2 Nanopore Sequencing

14.2.1 DNA Sequencing

DNA sequencing is the process of determining the exact order of nucleotides in a DNA molecule. Traditional techniques include Sanger sequencing and next-generation sequencing (NGS). These methods, while powerful, can be time-consuming and expensive.

14.2.2 Nanopore Sequencing

Nanopore sequencing is a third-generation sequencing method that involves passing single-stranded DNA through a nanoscale pore embedded in a membrane. As DNA passes through the pore, each nucleotide causes a characteristic disruption in ionic current, which is measured to determine the sequence.

Key components:

  • Nanopore (biological or synthetic)
  • Membrane system
  • Ionic current detector

14.2.3 Types of Nanopore Sequencing

  1. Biological nanopores: Derived from proteins such as alpha-hemolysin and MspA.
  2. Solid-state nanopores: Made from synthetic materials (e.g., silicon nitride).
  3. Hybrid systems: Combine biological selectivity with synthetic stability.

14.2.4 Pros and Cons of Nanopore Sequencing

Pros:

  • Real-time sequencing
  • Long read lengths
  • No need for amplification or labeling
  • Portable devices (e.g., Oxford Nanopore MinION)

Cons:

  • Higher error rates compared to NGS
  • Sensitive to environmental conditions
  • Complex data interpretation

14.3 Nanowires

14.3.1 Introduction

Nanowires are one-dimensional nanostructures with diameters in the nanometer range and lengths up to several micrometers. They possess unique electrical and optical properties, making them excellent candidates for biosensors and nanoelectronics.

Applications include:

  • Detection of biomolecules
  • Gas sensing
  • Environmental pollutant detection

14.3.2 Synthesis of Nanowires

Common methods:

  • Vapor-liquid-solid (VLS) growth
  • Electrochemical deposition
  • Template-assisted synthesis
  • Chemical vapor deposition (CVD)

These methods allow precise control over size, morphology, and surface chemistry.

14.4 Nanogold

14.4.1 Properties of Gold Nanoparticles

Gold nanoparticles (AuNPs) exhibit unique physicochemical properties due to their high surface area and quantum size effects.

Key features:

  • Biocompatibility
  • Easy functionalization with biomolecules
  • Strong optical absorption in the visible region

14.4.2 Surface Plasmon Resonance (SPR)

SPR is a phenomenon where conduction electrons on the gold nanoparticle surface oscillate in resonance with incident light. It leads to strong absorption/scattering, which can be used for:

  • Label-free biosensing
  • Environmental monitoring
  • Detection of toxins and pathogens

14.5 Nanoscale Optofluidic Sensor Array

14.5.1 Introduction

An optofluidic sensor array integrates optical detection with fluid handling at the nanoscale. These systems are highly miniaturized and can perform high-throughput analysis of biological and chemical substances.

14.5.2 Nanofluidics

Nanofluidics deals with the behavior and control of fluids in nano-sized channels. It enhances sensitivity and reduces sample volume.

Applications:

  • Detection of heavy metals
  • Monitoring pesticides in water
  • Single-molecule detection

14.5.3 Assembly and Working

  • Microfabrication or nanolithography is used to create nanochannels.
  • Fluid samples are introduced into the array.
  • Optical components (e.g., lasers or LEDs) detect changes in fluorescence or absorbance.
  • Data is interpreted through digital interfaces.

14.5.4 Advantages and Disadvantages

Advantages:

  • High sensitivity and specificity
  • Small sample volumes
  • Rapid analysis
  • Integration with portable systems

Disadvantages:

  • Complex fabrication
  • Expensive setup
  • Fragile components

14.6 Application of Bio-analytical Techniques in Environmental Monitoring

14.6.1 Introduction

Nanoscale bioanalytical tools have opened new avenues in real-time, in-field detection of environmental contaminants. They enable the detection of pollutants at very low concentrations and facilitate targeted remediation strategies.

14.6.2 Nanocontacts

Used for building nanoelectronic devices, nanocontacts are junctions between nanoscale wires or particles. They can detect electrical changes caused by molecular interactions with pollutants or biomolecules.

14.6.3 Cantilever Sensor (Nanoarm)

Cantilever sensors measure bending due to molecular interactions on their surface. These label-free sensors are extremely sensitive and useful for detecting:

  • Heavy metals
  • Toxins
  • Biological contaminants in water

14.6.4 Nanowires

As mentioned earlier, nanowires are ideal for gas sensors and biosensors due to their high surface-to-volume ratio. Their conductivity changes upon interaction with environmental chemicals.

14.6.5 Conducting Polymer

Conducting polymers (e.g., polyaniline, polypyrrole) are used in chemiresistive sensors that detect gases, heavy metals, and organic pollutants by changes in electrical resistance.

14.6.6 Peptide Nanoelectrode

Peptide-coated nanoelectrodes selectively bind to pollutants or biomolecules. Their electrical signal changes are used for ultrasensitive detection, even at parts-per-trillion levels.

14.7 Let Us Sum Up

Nanobioanalytical techniques are transforming the way biological and environmental analyses are conducted. With their high sensitivity, real-time monitoring, and miniaturized formats, tools like nanopore sequencing, nanowires, nanogold, and optofluidic arrays provide new solutions for environmental surveillance. Their applications include detection of pollutants, biomonitoring, and understanding molecular mechanisms underlying environmental responses.

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