When reference to carbon nanotubes, consider the following statements: 1. They can be used as carriers of drugs and antigens in the human body. 2. They can be made into artificial blood capillaries for an injured part of human body. 3. They can be used in biochemical sensors. 4. Carbon nanotubes are biodegradable. Which of the statements given above are correct?
Contents23
- A1 and 2 only
- B2, 3 and 4 only
- C1, 3 and 4 only
- D1, 2, 3 and 4
Show answer
Answer: (C) 1, 3 and 4 only
Carbon nanotubes (CNTs) are tiny tube-shaped structures made of carbon atoms.
Think of them as rolled-up sheets of graphene (a single layer of carbon atoms arranged in a honeycomb pattern).
Statement 1 is CORRECT: CNTs can be transformed into biocompatible drug-delivery systems (including antigens), for specific targeting and elimination of tumour cells. They have a large surface area and can pass through cell membranes.
Statement 2 is INCORRECT: When blood comes into contact with foreign surfaces, the platelets in blood get activated which leads to blood clots being formed. This can be catastrophic in clinical settings. Scientists have found that carbon nanotubes stimulate blood platelet activation, subsequently leading to serious and devastating blood clotting. This makes them unsuitable for artificial blood capillaries.
Statement 3 is CORRECT: NASA has demonstrated the development of biochemical sensors using carbon nanotube arrays. These are called 'Ultrasensitive Label-Free Electronic Biochips' for health monitoring and biomarker detection.
Statement 4 is CORRECT: A variety of experimental and molecular simulation technologies have been used to explore the biodegradation of Carbon Nanotubes. Multiple types of microbes including bacteria and fungi have the ability to degrade Carbon Nanotubes, graphene, and their derivatives. So they are biodegradable.
Since statements 1, 3 and 4 are correct, the answer is C.
Key Takeaway: CNTs are versatile — drug delivery, biosensors, and biodegradable. However, they cause blood clotting and cannot be used for artificial blood capillaries.
Carbon nanotubes have applications in drug delivery, artificial blood vessels, biosensors, and are biodegradable through enzymes like peroxidase.
The biodegradability of carbon nanotubes was a major research development in the late 2010s, making it a current topic for UPSC to test updated scientific knowledge.
UPSC is testing whether students know the latest research findings, not outdated assumptions about carbon nanotube properties.
Carbon Nanotubes: Structure & Properties
Science And Technology carbon nanotubes CNTs
Carbon Nanotubes: Structure, Types & Key Properties
Carbon nanotubes are rolled-up sheets of graphene forming tube-shaped structures
CNTs have exceptional strength (100x stronger than steel) and high surface area
CNTs are biodegradable by enzymes like peroxidase
Two main types: Single-Walled CNTs (SWCNTs) and Multi-Walled CNTs (MWCNTs)
What Are CNTs
Carbon nanotubes are cylindrical structures made of carbon atoms arranged in a honeycomb lattice. Imagine taking a single sheet of graphene (one-atom-thick carbon layer) and rolling it into a seamless tube — that's essentially what a CNT is.
Types & Properties
Type | Structure | Diameter | Key Property |
|---|---|---|---|
Single-Walled CNTs | Single graphene sheet rolled | 0.4-2 nm | Better electrical properties |
Multi-Walled CNTs | Multiple concentric tubes | 2-100 nm | Higher mechanical strength |
Functionalized CNTs | CNTs with attached molecules | Variable | Enhanced biocompatibility |
Unique Properties
Mechanical strength: 100 times stronger than steel at 1/6th the weight
Electrical conductivity: Can be metallic or semiconducting depending on structure
Thermal conductivity: Better than diamond and copper
Large surface area: Enables high drug-loading capacity
Biocompatibility: Compatible with blood and body tissues when properly functionalized
CNT Structure
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Source: Tuball — Single-walled Carbon Nanotubes: Structure, Properties, Applications · tuball.com
CNTs in Biomedical Applications
Science And Technology drug carriers artificial blood capillaries human body
Carbon Nanotubes in Medicine: Drug Delivery & Tissue Engineering
CNTs serve as drug carriers due to large surface area and cell membrane penetration ability
Used in artificial blood vessels and tissue scaffolds for medical implants
Can deliver antigens for vaccine development and immunotherapy
Functionalization improves biocompatibility and reduces toxicity
Why CNTs Work
CNTs excel in biomedical applications because of their high surface area for drug loading and ability to penetrate cell membranes. When properly functionalized (modified with biocompatible molecules), they become safe for use inside the human body.
Biomedical Applications
Application | How CNTs Help | Current Status | Key Advantage |
|---|---|---|---|
Drug Delivery | Load drugs on surface, target specific cells | Clinical trials | Can cross blood-brain barrier |
Antigen Carriers | Transport vaccines to immune cells | Research phase | Enhanced immune response |
Artificial Blood Vessels | Form scaffolds for tissue growth | Experimental | Biocompatible, strong structure |
Gene Therapy | Deliver DNA/RNA into cells | Laboratory studies | Protect genetic material |
Medical Advantages
Targeted delivery: Can be programmed to reach specific organs or cell types
Minimal side effects: Biodegradable nature reduces long-term toxicity concerns
Versatile loading: Can carry small molecules, proteins, or genetic material simultaneously
Controlled release: Drug release can be triggered by pH, temperature, or enzymes
Question Connection
This 2020 UPSC question tested whether students knew CNTs could function as both drug carriers (Statement 1) and artificial blood capillaries (Statement 2) — both are correct due to CNT biocompatibility and structural properties.
CNTs in Biochemical Sensors
Science And Technology biochemical sensors
Carbon Nanotube Biosensors: Detection & Applications
NASA successfully uses CNT arrays as biosensors for detecting biological substances
CNTs detect glucose, DNA, proteins and other biomolecules with high sensitivity
Work through electrical conductivity changes when target molecules bind
How CNT Sensors Work
CNT biosensors detect biological or chemical substances by measuring changes in electrical conductivity when target molecules bind to the nanotube surface. NASA has pioneered their use in space applications for detecting life signatures.
CNT Sensor Applications
Detection Target | Application | Sensitivity Level | Example Use |
|---|---|---|---|
Glucose | Diabetes monitoring | Very high | Continuous glucose monitors |
DNA sequences | Genetic testing | Single molecule | Disease diagnosis |
Proteins | Cancer biomarkers | Nanogram levels | Early cancer detection |
Pathogens | Infection diagnosis | Single bacterium | Rapid testing kits |
Toxins | Environmental monitoring | Parts per billion | Water quality testing |
Sensor Advantages
Ultra-sensitive: Can detect single molecules or bacteria
Fast response: Real-time detection within seconds to minutes
Miniaturization: Enable portable, handheld diagnostic devices
Multi-target: Single sensor can detect multiple substances simultaneously
Cost-effective: Cheaper than traditional laboratory methods
Detection Process
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Sample Introduction**
Biological sample contacts CNT sensor surface`"]
s2["`**Molecular Binding**
Target molecules bind to functionalized CNT sites`"]
s3["`**Property Change**
Electrical conductivity or resistance changes`"]
s4["`**Signal Processing**
Electronic circuit converts change to readable output`"]
s5["`**Result Display**
Concentration or presence/absence shown on device`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5CNT Biodegradability
Science And Technology biodegradable
Carbon Nanotube Biodegradation: Enzymes & Environmental Impact
CNTs are biodegradable by enzymes like peroxidase — contradicting earlier assumptions
Horseradish peroxidase can break down CNT structure in presence of hydrogen peroxide
Biodegradation reduces long-term toxicity concerns for medical applications
Discovery Background
Initially, scientists believed CNTs were non-biodegradable due to their strong carbon-carbon bonds. However, research revealed that certain enzymes can actually break down CNT structures, making them environmentally safer than previously thought.
Biodegradation Mechanisms
Enzyme Type | Example | Mechanism | Conditions Required |
|---|---|---|---|
Peroxidase | Horseradish peroxidase | Oxidative degradation | Hydrogen peroxide present |
Myeloperoxidase | Human neutrophil enzyme | Inflammatory response | In vivo conditions |
Lignin peroxidase | Fungal enzyme | Ligninolytic activity | Specific pH and temperature |
Laccase | Bacterial/fungal origin | Phenol oxidation pathway | Oxygen and mediators |
Degradation Factors
CNT structure: Single-walled CNTs degrade faster than multi-walled CNTs
Functionalization: Surface modifications can enhance or inhibit biodegradation
Enzyme concentration: Higher enzyme levels lead to faster degradation rates
Environmental conditions: pH, temperature, and oxygen levels affect degradation speed
UPSC Trap Alert
Statement 4 was the trickiest in this question. Many students assumed CNTs were non-biodegradable due to their strong structure, but the discovery of enzyme-mediated degradation makes this statement correct.
Trap: Assuming CNTs are non-biodegradable due to strong carbon bonds — peroxidase enzymes can break them down
Confusion: Mixing up carbon nanotubes with carbon fiber (which is less biodegradable)
Common error: Thinking biodegradability makes CNTs weak — they retain strength until enzyme exposure
Nanomaterials in Technology
Science And Technology
Nanomaterials: CNTs vs Other Carbon Structures
Graphene is a single-atom-thick carbon sheet; CNTs are rolled graphene tubes
Each carbon nanomaterial has unique applications based on structure
Fullerenes are soccer-ball-shaped carbon cages; different from tube structures
Carbon Nanomaterials Comparison
Material | Structure | Dimension | Key Application | Discovery Year |
|---|---|---|---|---|
Graphene | Single carbon layer | 2D sheet | Flexible electronics | 2004 |
Carbon Nanotubes | Rolled graphene | 1D tube | Drug delivery, sensors | 1991 |
Fullerenes | Carbon cage | 0D sphere | Antioxidants, solar cells | 1985 |
Carbon Nanofibers | Stacked graphene | 1D fiber | Composite materials | 1889 |
Graphene Quantum Dots | Small graphene pieces | 0D fragments | Bioimaging, LEDs | 2008 |
Nanotechnology Applications
# Nanomaterials
## Electronics
- Flexible displays
- High-speed transistors
- Memory devices
- Solar cells
## Medicine
- Drug delivery
- Biosensors
- Tissue engineering
- Medical imaging
## Environment
- Water purification
- Air filtration
- Pollution monitoring
- Energy storage
## Materials
- Stronger composites
- Lighter structures
- Conductive coatings
- Smart materialsDon't confuse: Graphene (flat sheet) with CNTs (tube shape) — different structures, different uses
Fullerenes vs CNTs: Fullerenes are spherical cages, CNTs are cylindrical tubes
Carbon fiber ≠ CNTs: Carbon fiber is made of thousands of carbon filaments, not nanoscale tubes