Roshchupkin A. Biomedical patterns of using MXene for photothermal therapy of malignant tumours

Malignant neoplasms remain one of the most acute problems in modern medicine. Highly aggressive forms, such as skin melanoma, whose incidence is steadily increasing, are of particular concern. Traditional treatment methods (chemotherapy, immunotherapy) are often accompanied by high systemic toxicity, the development of resistance, and autoimmune reactions. Given this, modern oncology urgently needs to transition to minimally invasive strategies that effectively destroy tumors while preserving the architecture of healthy tissues and minimizing systemic burden on the patient. Thermal ablation of tumors, particularly photothermal therapy (PTT), is a promising treatment option. Its mechanism is based on induced hyperthermia: heating above 50 °C leads to irreversible protein denaturation and coagulation necrosis. The use of near-infrared (NIR) radiation ensures light penetration through biological tissues. The "biological transparency window" in NIR-II (1000–1700 nm) is particularly promising, as it is characterized by low scattering, greater tissue tolerance, and the ability to penetrate to significant depths. This guarantees the spatial selectivity of the therapy, significantly reducing the risk of damaging surrounding healthy structures. Nanomaterials open up a new level of precision in PTT. Of particular interest are MXenes—a class of two-dimensional materials consisting of transition metal carbides or nitrides. They strongly absorb light in the NIR range and exhibit high efficiency in converting it into heat. However, continuous-wave lasers have been used in most studies to date. Conversely, pulsed lasers reduce the total impact energy, enabling effective tumor ablation with minimal thermal damage to surrounding tissues. The dissertation is devoted to the development, optimization, and evaluation of the efficacy and biocompatibility of PTT protocols for malignant neoplasms using MXenes (Ti3C2Tx and Nb4C3Tx) in synergy with pulsed NIR radiation. The hypothesis regarding the advantages of using pulsed Nd:YAG lasers (1064 nm, NIR-II) in combination with MXenes was experimentally confirmed. Energy generation via ultrashort flashes with thermal relaxation periods enables thermal confinement, preserving surrounding cells. Using a suite of physicochemical methods (XRD, SEM/TEM, EDS), the successful synthesis and structural stability of Ti3C2Tx and Nb4C3Tx were confirmed, and their ability to convert light into heat effectively was demonstrated. Optimal laser exposure parameters were established: a power density of 3.1 J/cm², a pulse duration of 200 ms, and a frequency of 1 Hz (heating above 60 °C). In vitro studies using normal and tumor cell models have demonstrated that both types of MXenes exhibit high biocompatibility and low cytotoxicity. Nb4C3Tx is effectively internalized by melanoma cells and localizes to the cytoplasm. A crucial methodological regularity was discovered: MXenes can undergo autocatalytic reduction of resazurin, which can lead to false-positive results and requires mandatory cross-verification. The combined effect of MXenes and pulsed laser irradiation induced the dose-dependent death of tumor cells. In vivo safety evaluation of the method on a rat model confirmed the absence of systemic toxicity: histological analysis of visceral organs revealed no pathological changes or off-target material accumulation following Ti3C2Tx administration and laser irradiation. Local skin reactions were transient and resolved with complete repair. The therapeutic efficacy of Nb4C3Tx-mediated PTT in the NIR-II window was demonstrated in vivo for the first time on a syngeneic melanoma model in mice. Intratumoral injections of Nb4C3Tx followed by threefold pulsed irradiation (1064 nm) significantly inhibited tumor growth: on the 26th day, their relative size was almost three times smaller compared to the control group. Massive necrosis of melanoma cells and destruction of the vascular bed were observed. Using immunohistochemical analysis, the mechanism of local nanomaterial clearance in vivo was described for the first time: Nb4C3Tx nanoflakes are eliminated via active phagocytosis by M1 (CD68+) and M2 (CD163+) macrophages, which form clusters in the tumor repair zone without accumulating in internal organs. Although complete eradication of large tumor masses was not achieved due to the physical limitations of light penetration depth and the lack of active targeting in pristine MXenes, the results obtained provide a reliable fundamental basis for developing innovative precision nanomedicine platforms. Optimized pulsed-laser parameters, combined with active targeting strategies, will enable safe and highly effective treatments for oncological diseases.