CNTs in Biomedical Applications – Drug Delivery and Biosensing
Carbon nanotubes (CNTs) have long been recognized for their exceptional electrical, mechanical, and thermal properties. In recent years, the biomedical field has increasingly adopted CNTs for advanced applications that require high sensitivity, targeted interaction with biological systems, and nanoscale precision. Two of the most promising areas are drug delivery and biosensing, where CNTs enable new therapeutic strategies and highly responsive diagnostic tools.
This article explores how single-walled (SWCNT) and multi-walled carbon nanotubes (MWCNT) are engineered for biomedical use, how they interact with cells and tissues, and why they are reshaping the landscape of next-generation healthcare technologies.
1. Why CNTs Are Valuable in Biomedicine
CNTs possess a distinctive combination of properties that make them suitable for medical applications:
✔ Nanoscale Dimensions
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Comparable in size to proteins, DNA, and cell membrane structures
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Easily internalized by cells via endocytosis or membrane penetration
✔ High Surface Area
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Ideal for loading drugs, antibodies, nucleic acids, or imaging agents
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Tunable functionalization improves solubility and targeting
✔ Strong Optical & Electrical Properties
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SWCNTs exhibit near-infrared (NIR) fluorescence, enabling deep-tissue optical sensing
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Conductivity supports electrochemical biosensors
✔ Mechanical Strength
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Robust carriers that maintain structural integrity under physiological conditions
Because of these characteristics, CNTs act as both carriers and sensing elements—something that few other nanomaterials can achieve simultaneously.
2. Surface Functionalization: The Key to Biomedical CNTs
Raw CNTs are hydrophobic and can agglomerate in aqueous environments, limiting biological compatibility.
Thus, functionalization is essential:
A. Covalent Functionalization
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Attaching functional groups (–COOH, –OH, –NH₂) via chemical reactions
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Enhances solubility and provides binding sites
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Slightly affects electrical properties
B. Non-Covalent Functionalization
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Polymer wrapping (PEG, PLGA)
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Surfactant or biomolecule adsorption
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Preserves intrinsic CNT conductivity and optical behavior
C. Targeted Ligand Functionalization
Ligands can be added to target:
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Tumor receptors (HER2, folate receptor)
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Immune cells
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Inflammation markers
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Neuroreceptors
Functionalization is what transforms CNTs from raw nanomaterials into medically useful tools with controlled biodistribution and improved biocompatibility.
3. CNTs in Drug Delivery
CNTs serve as nanoscale carriers capable of transporting therapeutic molecules and releasing them in specific tissues. They are used for:
3.1 Targeted Chemotherapy Delivery
CNTs can load high quantities of chemotherapeutic drugs such as:
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Doxorubicin
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Paclitaxel
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Cisplatin
Thanks to ligand functionalization, CNTs selectively accumulate in tumor tissues through:
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Receptor-mediated targeting (e.g., folate receptors in ovarian cancer)
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Enhanced permeability and retention (EPR) effect in tumors
Advantages:
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Significantly reduced systemic toxicity
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Higher local drug concentration
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Enhanced patient tolerance
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Improved drug stability during circulation
CNT-based nanocarriers can also perform pH-triggered release, ensuring chemotherapy is only released in acidic tumor environments.
3.2 Gene and RNA Therapeutics Delivery
CNTs transport:
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siRNA
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mRNA
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DNA plasmids
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CRISPR-Cas9 complexes
Through CNT-assisted cellular uptake, gene therapies achieve:
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Higher transfection efficiency
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Improved protection from enzymatic degradation
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Greater cell membrane penetration
This offers a promising route for difficult-to-treat genetic conditions, cancers, and degenerative diseases.
3.3 Photothermal Therapy (PTT)
CNTs absorb NIR light and convert it into heat. When injected into a tumor, NIR irradiation raises the temperature locally to 45–50°C, killing cancer cells with high precision and minimal damage to healthy tissues.
Benefits of CNT-mediated PTT:
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Non-invasive
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Highly localized
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Compatible with drug co-delivery for synergistic effects
Dual-mode systems combine drug release + photothermal therapy for maximum efficacy.
3.4 Crossing Biological Barriers
CNTs are capable of crossing:
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The blood–brain barrier (BBB)
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Cellular membranes
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Mucosal surfaces
This ability opens the door to treatments for:
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Brain tumors
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Neurodegenerative disorders (Parkinson’s, Alzheimer’s)
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CNS drug delivery
4. CNTs in Biosensing
CNTs are exceptionally sensitive to chemical and biological changes. Their conductivity varies with the adsorption of biomolecules, making them powerful transducers in sensing devices.
4.1 Electrochemical Biosensors
CNT electrodes detect:
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Glucose
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Dopamine
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Uric acid
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Cholesterol
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Heavy metals
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Tumor biomarkers
Performance advantages include:
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Low detection limits (pM–nM range)
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Fast electron transfer
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High stability
CNT-modified electrodes are used in lab-on-chip diagnostics, wearable sensors, and point-of-care devices.
4.2 Gas and Breath Biosensors
CNT sensors can detect trace gases associated with disease biomarkers:
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Acetone → Diabetes
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Nitric oxide → Asthma
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Ammonia → Kidney dysfunction
The ultra-high sensitivity of CNTs enables early diagnosis via non-invasive breath analysis.
4.3 NIR Fluorescence Biosensing (SWCNT)
SWCNTs naturally emit in the NIR-II window (1000–1700 nm), allowing deep tissue imaging and biosensing.
Applications include:
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Real-time detection of neurotransmitters
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Monitoring inflammatory markers
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Optical tracking of drug release
The signal is stable, non-photobleaching, and highly selective when functionalized with specific recognition molecules.
4.4 Mechanical and Pressure Biosensing
CNT networks have piezoresistive behavior. When pressure or strain changes, their resistance changes proportionally.
Applications:
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Implantable pressure sensors (e.g., in blood vessels)
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Smart bandages for wound healing
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Wearable health monitoring patches
These sensors require extremely thin, flexible materials—CNT films are ideal.
5. Biocompatibility and Safety Considerations
While CNTs hold enormous potential, clinical translation requires careful evaluation.
Key considerations:
A. Purity
Residual metal catalysts must be minimized (<100 ppm preferred).
B. Functionalization
Proper surface treatment dramatically improves biocompatibility.
C. Dose and Size
Shortened CNTs (50–300 nm) display lower toxicity and improved clearance.
D. Biodistribution
Understanding retention and excretion pathways ensures safe clinical use.
Many studies show that properly functionalized CNTs demonstrate excellent biocompatibility and are suitable for therapeutic and diagnostic applications.
6. Manufacturing Challenges & Opportunities
Commercializing CNT-based biomedical materials requires:
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High-purity SWCNT or MWCNT production
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Reproducible functionalization
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Uniform dispersions
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Sterilization compatibility
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GMP manufacturing workflow
Graphene Echo’s CNT-based product line (powders, dispersions, functionalized CNTs) and customization services can supply research labs and biotech companies developing next-generation nanomedicine solutions.
7. Future Outlook: CNTs as a Pillar of Next-Gen Medicine
CNTs are poised to become foundational materials in biomedical innovation, driven by:
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Precision medicine
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Miniaturized diagnostics
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Nanocarrier-based drug delivery
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Smart wearable and implantable devices
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AI-enabled biosensing platforms
Key frontier areas include:
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CNT-enabled neural interfaces
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Ultra-fast point-of-care disease detection
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Hybrid CNT–polymer scaffolds for tissue engineering
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CNT-based microfluidic medical devices
Their unique ability to act as both carriers for therapy and transducers for sensing places CNTs among the most versatile nanomaterials in biomedical engineering.