In a world invisible to the naked eye, a quiet revolution is unfolding — scientists are making carbon nanotubes capture the molecules of life.
Imagine structures 50,000 times thinner than a human hair, capable of seamlessly penetrating living cells without causing harm. This is not a scene from a science fiction movie, but the reality of modern carbon nanotubes (CNTs) — a revolutionary material that opens new horizons in biomedicine, electronics, and materials science.
Structures at nanometer dimensions
Can penetrate cells without damage
Advanced simulation techniques
Particular interest for scientists is the interaction of nanotubes with biologically active substances, in particular with amino acids — the building blocks of life's proteins. How exactly does this interaction occur at the atomic level? What forces make amino acids stick to the surface of nanotubes? Answers to these questions can be obtained using advanced methods of computer modeling.
Carbon nanotubes are graphene planes rolled into hollow cylinders, forming structures with exceptional mechanical, electrical, and thermal properties. Their uniqueness lies in the combination of nanometer sizes with a huge specific surface area and the ability to interact with various molecules, including biologically active compounds.
Research confirms that CNTs can cross the cell membrane without disrupting it 1 , making them promising candidates for targeted drug delivery, diagnostics, and even gene therapy. This ability determines the importance of studying their interactions with amino acids — fundamental components of living organisms.
Hexagonal carbon lattice forming cylindrical structures
When experimental methods face difficulties in studying nanometer-scale objects, computer modeling comes to the rescue. This powerful tool allows scientists to "see" molecular interactions that cannot be observed directly.
In the case of studying the sorption of amino acids on nanotubes, the most effective approach is the Density Functional Theory (DFT) method, which takes into account quantum-mechanical effects and allows highly accurate prediction of the energy and geometry of molecular systems 1 .
Sophisticated mathematical method that accurately describes the behavior of electrons in molecules.
Special adjustment accounting for weak van der Waals forces, crucial for interactions with highly polarizable nanotubes.
Indicator of the binding strength of a molecule with the nanotube surface.
Russian scientists from Voronezh State University conducted a groundbreaking study of the interaction of two essential amino acids — L-arginine and L-lysine — with single-walled carbon nanotubes 1 .
Creation of computer models of nanotubes and amino acids in various spatial configurations.
Positioning of arginine and lysine molecules in three key positions: at the open end, on the external side surface, and on the internal side surface of nanotubes.
Application of density functional B3LYP/6-31G(d,p) with GD3 dispersion correction for geometry optimization and calculation of energy parameters.
Calculation of adsorption energies, dipole moments, charge distributions, and distances between atoms.
A feature of this study was the inclusion of dispersion correction, which is often ignored in similar works but is extremely important for the correct description of interactions with highly polarizable nanotubes 1 .
Select different positions to see how amino acids interact with carbon nanotubes:
Covalent bond formation
Van der Waals forces
Weakest interaction
Covalent bond formation with high electron density
The calculations showed a clear pattern in adsorption energies for all studied systems. The strongest binding of amino acids was observed at the open ends of nanotubes, while the weakest was on the external side surfaces.
| Amino Acid Position | L-Arginine | L-Lysine | Interaction Type |
|---|---|---|---|
| Open End of CNT | Highest Energy | Highest Energy | Covalent Bond |
| Internal Side Surface | Medium Energy | Medium Energy | Van der Waals Forces |
| External Side Surface | Lowest Energy | Lowest Energy | Van der Waals Forces |
This energy series satisfies the condition: Eend > Einternal > Eside 1 . Scientists explained this pattern by the different nature of interactions: on the external side surface, the amino acid interacts with only part of the tube surface; inside the nanotube — with the entire internal surface through van der Waals forces; and at the open end, a covalent bond forms between the amino acid and the nanotube.
| Parameter | L-Arginine | L-Lysine | Explanation of Differences |
|---|---|---|---|
| Adsorption Energy | Close but different values | Close but different values | Different chemical structures of side chains |
| Optimal Position | Open End of CNT | Open End of CNT | High electron density at tube ends |
| Dipole Moment | Changes upon adsorption | Changes upon adsorption | Redistribution of electron density |
The formation of a covalent bond at the open end of the nanotube was explained by researchers as due to higher electron density near the terminal sections of the nanotube compared to the external and internal side surfaces 1 .
The results of this research have not only theoretical but also significant practical value. Scientists discovered that nanotubes functionalized with arginine and lysine exhibit enhanced antibacterial activity compared to non-functionalized nanotubes 1 . This discovery opens pathways to creating new antimicrobial materials.
Development of targeted drug delivery systems using functionalized nanotubes for precise treatment.
Creation of highly sensitive sensors for detecting biological molecules based on nanotube interactions.
Assessment of nanomaterial safety by understanding their interactions with biological systems.
Construction of hybrid nano-biomaterials for advanced applications in tissue engineering and more.
Computer modeling of sorption interactions of amino acids with carbon nanotubes is not just an abstract scientific direction. It is a window into the world of nanometer scales, where form determines function, and understanding molecular interactions opens the way to creating the materials of the future.
Research like the one reviewed emphasizes the importance of fundamental science for solving applied problems. Tiny carbon nanotubes that "catch" amino acids may one day become the basis for new drugs, diagnostic systems, and high-tech materials that change our lives for the better.
As researchers note, accounting for dispersion corrections — a previously often ignored aspect — turns out to be key for accurately describing interactions in such systems 1 . This reminds us that in science, details often have decisive importance, and advancement in the smallest scales can lead to the biggest discoveries.