In recent years, two-dimensional (2D) materials have attracted a lot of attention because of their unique properties and wide range of possible applications. Graphene is the most famous example, but it doesn’t stand alone anymore. A new family of 2D materials, called MXenes, is quickly becoming just as interesting—especially for energy, water treatment, and environmental technologies.

One particular MXene, Ti₃C₂Tₓ, has already been explored for water purification and desalination membranes. Because water treatment systems are constantly exposed to microorganisms like bacteria, an important question arises:

Can Ti₃C₂Tₓ MXene also prevent bacterial growth and biofouling?

This article answers that question by carefully studying the antibacterial activity of Ti₃C₂Tₓ MXene against two common bacteria:

• Escherichia coli (E. coli) – a Gram-negative bacterium

• Bacillus subtilis (B. subtilis) – a Gram-positive bacterium

The results show that Ti₃C₂Tₓ is not only antibacterial—it is more effective than graphene oxide (GO), which is already a well-known antibacterial nanomaterial. The study also investigates how Ti₃C₂Tₓ kills bacteria and what factors affect its performance.

In this blog, we will walk through the main ideas and findings of the paper in a clear, simple, and logical way.

1. What Are MXenes and Why Do They Matter?

MXenes are a large family of 2D materials made from layered ceramics known as MAX phases. Their general formula is:

Mₙ₊₁XₙTₓ, where

• M is an early transition metal (like Ti, Nb, V, Mo, etc.),

• X is carbon and/or nitrogen,

• Tₓ represents surface terminations such as –O, –OH, or –F.

In this study, the focus is on Ti₃C₂Tₓ, the most widely studied MXene to date.

Ti₃C₂Tₓ has several properties that make it very attractive for water-related applications:

• It is hydrophilic, meaning it interacts well with water.

• It has a layered structure with spaces between the sheets that can host water and ions.

• It shows excellent ionic sieving, meaning it can selectively filter different kinds of ions.

• It has high electrical conductivity, which is useful in membranes, sensors, and electrochemical systems.

In earlier work, Ti₃C₂Tₓ membranes were shown to provide ultrafast water flux and selective separation of metal ions, performing even better than graphene oxide membranes in some cases.

However, until this article, one crucial aspect had not been explored:

Does Ti₃C₂Tₓ MXene have antibacterial properties?

This is important not only for water purification, but also for biomedical, disinfection, and antifouling applications.

2. Why Study Antibacterial Activity?

In water treatment plants, pipes, filters, and membranes are constantly exposed to bacteria. Over time, bacteria can attach to surfaces, form biofilms, and block pores. This is known as biofouling, and it:

• reduces the efficiency of water treatment,

• increases maintenance costs,

• shortens the lifetime of membranes and equipment.

If a membrane material is naturally antibacterial, it is far less likely to suffer from biofouling. That’s why understanding whether MXenes can kill or inhibit bacteria is critical.

There is a lot of background work on other nanomaterials:

• Graphene-based materials (like GO and reduced GO) have shown antibacterial behavior through physical damage and oxidative stress.

• Metal and metal oxide nanoparticles (e.g., Ag, ZnO, TiO₂) show antibacterial effects often linked to reactive oxygen species (ROS) formation and interaction with bacterial membranes and DNA.

• Carbon nanotube composites can damage membranes and interfere with electron transport.

But until now, MXenes had not been systematically studied as antibacterial materials. Given their structure and chemical activity, it was reasonable to suspect that they might behave similarly to graphene or even better.

This study is the first detailed investigation of the antibacterial activity of Ti₃C₂Tₓ MXene in aqueous suspension.

3. How Ti₃C₂Tₓ MXene Was Prepared and Compared

The researchers used three related materials:

1. Ti₃AlC₂ (MAX phase) – the parent ceramic material

2. Multilayer Ti₃C₂Tₓ (ML-MXene) – partially exfoliated MXene with stacked layers

3. Delaminated Ti₃C₂Tₓ MXene – single- and few-layer flakes in colloidal suspension

In simple terms:

• The MAX phase is a 3D solid.

• ML-MXene is like a stack of thin sheets.

• Delaminated Ti₃C₂Tₓ is a well-separated dispersion of individual nanosheets.

The MXene was synthesized by etching away the aluminum layer from Ti₃AlC₂ using an LiF/HCl method and then delaminated by ultrasonication in water under argon. This produced single- and few-layer Ti₃C₂Tₓ flakes that could stay dispersed in water as a stable colloidal solution.

Graphene oxide (GO) was also prepared using a modified Hummers method and was used as a reference material, since GO is already considered a strong antibacterial nanomaterial.

The different forms of MXene were characterized with tools like SEM, TEM, EDS, and XRD to confirm:

• their layered structure,

• the presence of surface terminations (–O, –F),

• and their high degree of exfoliation.

The key point here is that delaminated Ti₃C₂Tₓ has a much higher exposed surface area and better dispersion, which should improve its interaction with bacteria and enhance antibacterial performance.

4. Testing Antibacterial Activity: First Comparisons

The antibacterial activity of the three materials—MAX, multilayer MXene, and delaminated Ti₃C₂Tₓ—was tested against E. coli and B. subtilis.

Bacterial cells were exposed to each material at the same concentration (100 µg/mL) for 4 hours, then plated on nutrient agar and incubated. The number of colonies formed was counted to determine cell survival.

The results were clear and progressive:

• Ti₃AlC₂ (MAX):
  Only about 14–18% inhibition of bacterial growth. Most bacteria survived.

• Multilayer Ti₃C₂Tₓ (ML-MXene):
  Moderate antibacterial activity, with around 30–34% growth inhibition.

• Delaminated Ti₃C₂Tₓ MXene:
  Very strong antibacterial effect, with about 97% loss of cell viability for both E. coli and B. subtilis.

This showed that delamination is crucial. The more the material is exfoliated into thin nanosheets, the more effectively it can interact with and kill bacteria. Due to this strong performance, only the delaminated Ti₃C₂Tₓ was used for the detailed follow-up studies.

5. Concentration-Dependent Antibacterial Effect

Next, the researchers examined how the antibacterial activity changes with increasing MXene concentration. They exposed bacteria to various concentrations of Ti₃C₂Tₓ (from 2 to 200 µg/mL) and measured:

• Bacterial cell viability using colony counts

• Bacterial growth curves using optical density (OD) measurements

Key findings:

• Even at the lowest concentration tested (2 µg/mL), there was already a measurable impact on bacteria.

• As the concentration increased:

  • The survival rate of both E. coli and B. subtilis dropped sharply.

  • At around 20 µg/mL, cell survival was in the range of roughly 28–35%.

  • At 100 µg/mL, more than 96% of bacteria were inactivated.

  • At 200 µg/mL, over 99% of bacterial cells were killed.

This makes it clear that Ti₃C₂Tₓ MXene shows strong, dose-dependent antibacterial behavior against both Gram-negative and Gram-positive bacteria.

The study also observed that, especially at lower concentrations, B. subtilis (Gram-positive) seemed slightly more sensitive than E. coli (Gram-negative). This is consistent with known differences in bacterial cell wall structures and surface charges, which affect how nanomaterials interact with them.

6. Comparison with Graphene Oxide (GO)

Since GO is widely known as an antibacterial nanomaterial, the authors compared its effect with Ti₃C₂Tₓ under the same conditions.

Both E. coli and B. subtilis were treated with various concentrations of GO (0–200 µg/mL), and the cell survival rates were measured.

The comparison showed:

• At the same concentration, Ti₃C₂Tₓ always caused more bacterial inactivation than GO.

• At 200 µg/mL:

  • Ti₃C₂Tₓ caused >98–99% cell inactivation,

  • GO caused about 90% cell inactivation.

The researchers also expressed the results in terms of “log reduction”, a standard way to describe how many orders of magnitude the bacterial population is reduced. Ti₃C₂Tₓ gave higher log reductions than GO, again confirming that Ti₃C₂Tₓ is more potent than GO as an antibacterial agent in this setup.

7. Effect of Time: How Fast Does MXene Kill Bacteria?

The researchers then asked: How quickly does Ti₃C₂Tₓ act?

They exposed bacteria to 200 µg/mL of Ti₃C₂Tₓ and monitored bacterial viability over 4 hours. The results showed that:

• After 2 hours, cell viability had already dropped to about 50%.

• After 4 hours, more than 98% of bacterial cells were inactivated.

This relatively short contact time for such a high killing rate is promising for real-world use, where water or biological fluids may only remain in contact with a membrane or material for limited periods.

They also evaluated bacterial regrowth after exposure to MXene. Bacteria treated with various MXene concentrations were transferred into nutrient media and their growth was monitored over time using OD at 600 nm.

The key observations:

• The higher the MXene concentration, the slower the bacteria regrew.

• Growth rate constants decreased and doubling times increased significantly with increasing Ti₃C₂Tₓ concentration.

• Even after being moved to fresh growth media, the bacteria that had been exposed to higher MXene concentrations grew much more slowly or not at all.

This confirms that the treatment with Ti₃C₂Tₓ is truly bactericidal, not just temporarily inhibiting growth.

8. What Happens to Bacterial Cells? (Membrane Damage)

To understand how Ti₃C₂Tₓ kills bacteria, the authors examined the morphology and integrity of bacterial cells after treatment.

They focused particularly on:

• Cell membrane damage

• Leakage of cellular contents

Using electron microscopy and biochemical assays, they found:

• In untreated samples (controls), both E. coli and B. subtilis cells had smooth, intact membranes and healthy internal structures.

• After exposure to 50 and 100 µg/mL of Ti₃C₂Tₓ:

  • Many bacterial cells showed distorted shapes,

  • Membranes appeared disrupted,

  • There was visible leakage of cytoplasmic material.

• At higher concentrations (like 200 µg/mL), cells showed extensive lysis (breaking apart) and significant structural damage.

A biochemical test called the LDH release assay further supported these findings. LDH (lactate dehydrogenase) is an enzyme inside cells. When the membrane is damaged, LDH leaks out into the surrounding medium. The study showed that LDH release increased with higher MXene concentrations, indicating dose-dependent membrane damage.

Together, these results strongly suggest that direct physical interaction between MXene sheets and bacterial membranes is a key mechanism of antibacterial action.

9. Does Oxidative Stress Play a Role?

Many nanomaterials kill bacteria by generating reactive oxygen species (ROS), which damage DNA, proteins, and membranes.

To check whether ROS are involved in the antibacterial behavior of Ti₃C₂Tₓ, the authors carried out two types of abiotic (cell-free) tests:

1. Superoxide (O₂•⁻) production test using XTT

   • The study found no significant superoxide production across different MXene concentrations.

   • This suggests that superoxide is not a major factor in the antibacterial activity of Ti₃C₂Tₓ under the tested conditions.

2. Glutathione oxidation test

   • Glutathione is a key antioxidant molecule in cells.

   • When exposed to Ti₃C₂Tₓ, the amount of glutathione decreased more at higher MXene concentrations and over longer times.

   • This indicates that MXene may interact with or deplete thiol-containing molecules, causing oxidative stress or related effects.

The authors suggest that while superoxide formation is minimal, other kinds of oxidative or redox interactions may still occur, possibly involving:

• reactive surface groups on Ti₃C₂Tₓ,

• or adsorption/binding of glutathione to the MXene surface.

Additionally, because Ti₃C₂Tₓ is highly conductive, it might form electron-conductive bridges across bacterial membranes, disturbing normal electron transport and contributing to cell death.

10. Proposed Mechanism of Antibacterial Action

Based on all the experiments, the antibacterial behavior of Ti₃C₂Tₓ MXene nanosheets likely involves multiple steps and mechanisms:

1. Adsorption and wrapping

   • Hydrophilic, negatively charged Ti₃C₂Tₓ nanosheets attach to bacterial surfaces.

   • At higher concentrations, bacteria can become trapped or wrapped by thin MXene sheets, forming agglomerates.

2. Physical damage from sharp edges

   • The nanosheets have sharp edges that can mechanically damage bacterial membranes upon close contact.

   • This leads to membrane disruption, leakage of cytoplasm, and loss of integrity.

3. Chemical interactions and oxidative effects

   • MXene surfaces have reactive functional groups and strong reducing activity.

   • They may interact with cellular components (like thiol-containing molecules), disturb redox balance, or interfere with essential biochemical processes.

4. Possible electron transfer disruption

   • Due to their high conductivity, MXenes might act as electron sinks or bridges, redirecting electron flow and causing stress to the bacterial electron transport systems.

These combined physical and chemical effects result in cell death, rather than just temporarily stopping growth.

11. Why This Matters and What Comes Next

This study is important for several reasons:

• It clearly shows that Ti₃C₂Tₓ MXene is a powerful antibacterial material, effective against both Gram-negative and Gram-positive bacteria.

• Its antibacterial performance surpasses that of graphene oxide under the tested conditions.

• The antibacterial effect is:

  • dose-dependent,

  • time-dependent,

  • and confirmed through multiple methods (colony counts, growth curves, LDH release, and microscopy).

From an application point of view, this opens exciting possibilities:

• Water treatment and desalination membranes that are not only selective and high-flux, but also resistant to biofouling.

• Antimicrobial coatings on surfaces in healthcare, food processing, and filtration systems.

• Potential future uses in biomedical devices, where controlled antibacterial activity is valuable.

At the same time, the authors emphasize that this work is just a first step. There are many other MXenes with different metals (Nb, Mo, V, etc.) and different surface chemistries. Each may show different degrees of antibacterial activity and toxicity.

To fully understand the health and environmental impacts of MXenes, future work should explore:

• cellular uptake in mammalian cells,

• long-term toxicity,

• behavior in complex natural environments,

• and detailed mechanisms for different MXene compositions and surface terminations.

12. Final Thoughts

In summary, Ti₃C₂Tₓ MXene emerges from this study as a new and promising 2D antibacterial nanomaterial. It combines:

• strong antibacterial activity,

• tunable surface chemistry,

• hydrophilicity,

• and high conductivity.

These features make it a compelling candidate for next-generation water purification systems and antimicrobial technologies.