Tandem antioxidant and polymer coating stabilizes MXene for biomedicine

Mar 23, 2026

A two-step surface treatment combining ascorbic acid with a polymer shell keeps niobium carbide MXene nanosheets stable and non-toxic in biological media.

(Nanowerk News) Niobium carbide MXene nanosheets can be reliably protected from oxidative degradation in biological fluids using a two-step surface treatment, according to new research published in Frontiers of Materials Science (“Effect of tandem-type stabilization of Nb2CTx MXene on their colloidal and cytotoxic properties”). The approach, which pairs an antioxidant with a polymer shell, maintained the material’s colloidal stability and non-toxicity for at least 72 hours in conditions that mimic the body’s internal environment.

Key Findings

MXenes are ultra-thin, two-dimensional materials made from metal carbides that have attracted growing interest for medical applications such as drug delivery, biosensing, and cancer therapy. Among the many MXene compositions under investigation, niobium carbide (Nb2CTx) is considered especially suitable for use in the body because of its low toxicity and biological compatibility. Its practical use, however, has been limited by a tendency to oxidize and degrade when exposed to water and dissolved oxygen, a process that begins at the reactive edges of the nanosheets. Jakubczak et al. addressed this problem with a tandem stabilization strategy. In the first step, they treated single-layer Nb2CTx nanosheets with L-ascorbic acid, a form of vitamin C that acts as an antioxidant. The ascorbic acid binds to the exposed edges of the MXene flakes, which are the most vulnerable points of attack for water molecules and dissolved oxygen. By capping these reactive sites, the antioxidant suppresses the early stages of oxidation that would otherwise convert the niobium carbide into an oxide. The second step adds a macromolecular shell to the outer surface. The team tested three polymers, each of which interacts with the MXene surface differently. Polyethylene glycol (PEG) creates a physical barrier that spaces the nanosheets apart through steric hindrance, reducing the particle-to-particle contact that leads to clumping. Polydopamine (PDA) forms a tightly adherent shell through a combination of covalent bonds and pi–pi stacking, providing strong and lasting surface coverage. Poly-L-lysine (PLL) relies on electrostatic attraction between its positively charged groups and the negatively charged MXene surface, a weaker attachment mechanism. Testing in two standard biological media, phosphate-buffered saline and Dulbecco’s Modified Eagle’s Medium, revealed clear differences between the three polymer systems. The PEG and PDA combinations maintained consistent zeta potential values between roughly minus 15 and minus 12 millivolts, along with stable particle sizes, over a 72-hour period. The PLL-coated version showed progressive aggregation and a decline in surface charge, indicating that electrostatic bonding alone does not provide sufficient stability under physiological conditions. Cytotoxicity tests on two human skin cell lines, A375 melanoma cells and HaCaT keratinocytes, confirmed that none of the tandem-modified formulations caused measurable cell damage at concentrations ranging from zero to 100 milligrams per liter. The coating process preserves the intrinsic biocompatibility of niobium carbide MXene while adding the stability needed for reliable performance in biological settings. The combination of antioxidant edge protection and macromolecular surface coating produces a synergistic effect that exceeds what either treatment achieves alone. The ascorbic acid prevents oxidation at the most reactive sites, while the polymer layer guards against aggregation and further environmental exposure. The contrasting performance of the three polymers also offers practical design guidance: covalent and steric bonding mechanisms outperform purely electrostatic attachment for MXene surface engineering in biological media. The improved stability of the ascorbic acid-treated systems indirectly confirms the antioxidant’s role in suppressing MXene oxidation, though the current study evaluated this primarily through colloidal and electrokinetic measurements rather than direct oxidation-state analysis. Future work focused on quantifying antioxidant activity and testing these stabilized systems in animal models would bring niobium carbide MXene closer to practical use in nanomedicine and clinical research.