The core issue is the overlooked paradox of the nano-knife effect and the inflammatory cascade. You highlight the physical piercing of bacterial membranes as a key antibacterial mechanism. However, in a physiological in vivo environment, this same physical disruption of cellular membranes is not selective. If MXene flakes, especially micron-sized accordion-like structures, are introduced into a tissue or bloodstream, they will inevitably interact with and potentially damage host cells (erythrocytes, fibroblasts, immune cells). This triggers a complex inflammatory response (the foreign body response) characterized by protein adsorption, macrophage activation, and giant cell formation. Your review does not critically address how the nano-knife effect can be harnessed to kill bacteria without simultaneously exacerbating inflammation and fibrosis that would lead to implant encapsulation and failure. The discussion of biocompatibility is presented as a static property, whereas it is a highly dynamic and context-dependent interaction with the immune system.
To clarify this critical concern and strengthen the scientific rigor of your review, I would ask the following questions:
1. Your paper highlights the “nano-knife” effect for antibacterial activity but also notes the risk to “beneficial microorganisms.” More critically, how do you reconcile this physical membrane disruption mechanism with the requirement for long-term cytocompatibility with mammalian cells (e.g., osteoblasts, fibroblasts) at the implant-tissue interface? Is there any evidence that the physical interaction of bare MXene flakes with host cell membranes does not trigger pro-inflammatory pathways or pyroptosis, and if so, why was this crucial aspect of biocompatibility not discussed in the context of implantable scaffolds?
2. Degradation Products and Immunomodulation: You correctly state that MXene degradation in physiological environments is a concern. However, the fate of the degradation products (e.g., metal ions like Ti, Nb, or V) and their subsequent immunomodulatory effects are not addressed. Given that transition metal ions are known to be potent modulators of immune cell behavior (e.g., M1/M2 macrophage polarization), how can the promising in vitro osteoinductive and regenerative results be reliably extrapolated to in vivo success without a critical discussion on whether the therapeutic effect is driven by the intact 2D structure or by the ionic byproducts of its degradation? Ignoring this pharmacokinetic and pharmacodynamic aspect represents a major oversight in evaluating true clinical potential.