# Critical Assessment of Intrinsic Antibacterial Properties and Photothermal Therapy Potential of MXene Nanosheets

## TL;DR

This study finds that MXene nanosheets do not have intrinsic antibacterial properties but are effective for photothermal therapy when activated by near-infrared light.

## Contribution

The study resolves a contradiction by showing that MXene's antibacterial effects are not intrinsic but arise from contamination or oxidation, while highlighting its potential for photothermal therapy.

## Key findings

- No significant antibacterial effects were observed in pure MXene nanosheets at subtoxic concentrations.
- MXene-assisted photothermal therapy under near-infrared light achieved complete bacterial killing in vitro and improved wound healing in vivo.
- Antibody-functionalized MXene enabled selective eradication of Escherichia coli without harming nontarget bacteria.

## Abstract

MXenes are well-known as highly biocompatible two-dimensional
nanomaterials
with a wide range of biomedical applications, including antibacterial
strategies. However, the coexistence of high biocompatibility and
reported strong antibacterial effects presents a fundamental contradiction
that requires critical evaluation. In this study, we systematically
investigated the antibacterial properties of pure Ti3C2T
x
, Nb2CT
x
, V2CT
x
, and
Ti3CNT
x
MXene nanosheets of
varying flake sizes using multiple in vitro assays and an in vivo
wound model. High-resolution structural and chemical characterizations
confirmed the use of high-quality, minimally oxidized MXene samples
with well-defined surface terminations. Despite using multiple evaluation
methods, including disk diffusion, broth microdilution, time-kill
kinetics, ROS quantification, and electron microscopy, no significant
antibacterial effects were observed at subtoxic concentrations. Furthermore,
neither reactive oxygen species-mediated damage nor the hypothesized
“nano-knife” mechanical disruption mechanism could be
confirmed. This suggests that the previous observations of antibacterial
properties resulted from incomplete removal of etching products or
partial oxidation of MXene nanosheets. In contrast, we demonstrate
that MXene-assisted photothermal therapy (PTT) under near-infrared
laser irradiation offers highly effective and selective bacterial
ablation. Ti3C2T
x
MXene exhibited strong photothermal performance, achieving complete
bacterial killing in vitro and significant wound healing efficacy
in an in vivo rat model. Targeted PTT using antibody-functionalized
MXene nanosheets enabled the eradication of Escherichia
coli while sparing nontarget bacteria. These findings
suggest that while intrinsic antibacterial properties of pristine
MXenes are limited, their biocompatibility and photothermal responsiveness
make them promising platforms for next-generation, externally triggered
antibacterial therapies.