In this study, we explored the use of MnO and Fe
2O
3 NPs as targeted therapeutic agents for the disruption of cancer cell function. Conventional cancer therapies are often limited by challenges such as drug resistance, off-target effects, and serious adverse events, highlighting the urgent need for strategies that selectively target cancer cells while sparing healthy tissues. Mitochondria, essential for cellular energy production, apoptosis regulation, and reactive oxygen species (ROS) generation, have emerged as key therapeutic targets in cancer treatment (
35).
Our approach involved treating colorectal (HT29) and breast (Skbr3) cancer cells with MnO and Fe
2O
3 NPs, followed by exposure to IR laser radiation. Cell viability was assessed using the MTT assay in six experimental groups: T
c, T
F, T
Mn, T
L, T
L.Fe, and T
L.Mn. As shown in
Figure 3A and
B, cell viability decreased over time in both HT29 and Skbr3 cells, with the lowest viability observed at 72 hours. The combination of IR laser radiation and NPs produced the greatest cytotoxic effect in both cell lines. Among the individual treatments, Fe
2O
3 NPs showed greater cytotoxicity than MnO NPs or IR radiation alone. Notably, Skbr3 breast cancer cells exhibited higher sensitivity to treatment compared to HT29 colorectal cancer cells.
Supporting evidence comes from Razumov et al., who demonstrated selective cytotoxicity of MnO NPs against human glioblastoma cells while sparing healthy cells. Their study also identified the activation of cell death signaling pathways induced by the nanoparticles (
38). Similarly, another study confirmed significant cytotoxicity of MnO NPs in HT29 cells through MTT assays (
39). Alarifi et al. showed that Fe
2O
3 NPs induced cytotoxic and genotoxic effects in MCF-7 breast cancer cells via ROS production, lipid peroxidation, decreased antioxidant enzyme activity, nuclear fragmentation, apoptosis, and caspase-3 activation (
40).
The IR laser radiation, known for its potential to induce DNA damage and trigger programmed cell death, was shown in a separate study to significantly increase apoptosis in pancreatic cancer cells. The addition of gemcitabine to near-infrared (NIR) laser therapy synergistically enhanced apoptotic effects (
41).
Nanoparticles have been widely reported to generate ROS in cancer cells, elevating oxidative stress levels (
23). Reactive oxygen species, including superoxide (O₂⁻) and hydrogen peroxide (H
2O
2), are byproducts of mitochondrial respiratory chain activity and can damage cellular macromolecules, particularly lipids, proteins, and DNA (
42). This oxidative damage disrupts mitochondrial electron transport chains and triggers apoptosis or necrosis. A direct correlation between TBARS formation and LPO was observed in HT29 and Skbr3 cells following treatment with MnO, Fe
2O
3, and IR radiation, as shown in
Figure 5A and
B.
Protein carbonylation, another marker of oxidative damage, also increased in a time-dependent manner in both cell lines (
Figure 6A and
B) following treatment. This increase may be associated with the release of pro-apoptotic proteins such as cytochrome c, which play a critical role in cell death signaling pathways (
42). Reactive oxygen species-induced protein oxidation alters amino acid side chains, resulting in carbonyl formation. Protein carbonylation has been implicated in endoplasmic reticulum and lysosomal stress, aging, and antioxidant depletion (
42,
43).
Lysosomal membrane integrity was assessed using the acridine orange redistribution assay, as illustrated in
Figure 4A and
B. Cells were treated across the six groups (T
c, T
F, T
Mn, T
L, T
L.Fe, and T
L.Mn) for 6, 12, 24, 48, and 72 hours. Treatment with MnO, Fe
2O
3, and IR laser radiation led to redistribution of acridine orange from lysosomes to the cytoplasm, evidenced by a time-dependent increase in red fluorescence. The most significant redistribution occurred at 72 hours, indicating extensive lysosomal membrane permeabilization and cytotoxicity.
These findings confirm that the combined application of NPs and IR radiation induces greater cytotoxicity than any single treatment. This was consistent with MTT results. Previous studies have also employed acridine orange staining to evaluate lysosomal integrity. One such study using magnetic systems and iron oxide NPs on liver cancer cells found increased cathepsin B activity, supporting lysosomal membrane permeabilization and apoptosis induction (
42). Ramu et al. developed a binuclear platinum (II) BODIPY complex for lysosomal targeting and near-IR-induced photocytotoxicity. Using acridine orange assays, they demonstrated lysosomal accumulation and potent photodynamic apoptotic activity in cancer cells, with minimal toxicity in the absence of light (
43).
Previous studies indicate that NPs significantly impair mitochondrial function by modulating ROS dynamics, leading to disrupted ATP production and elevated levels of ROS (
44). This mechanism corresponds with observations suggesting that NPs utilize oxidative stress and osmotic pressure to trigger pyroptosis in tumor cells. Targeted inhibition of mitochondrial complexes can push ROS levels beyond cellular repair thresholds, thereby threatening tumor cell viability.
Our research supports this mechanism, showing that NPs designed to target specific mitochondrial complexes not only elevate ROS levels but also enhance immune responses by promoting immunogenic cell death (ICD) and facilitating T-cell infiltration into hypoxic tumor regions (
44). These findings align with recent studies demonstrating that programmed drug release in such microenvironments can amplify immune system activation. Notably, the inhibition of mitochondrial oxidative stress has been shown to generate ROS levels consistent with the "ROS storm" model, inducing oxidative damage and potentially activating ICD pathways, which initiate immune responses against residual tumor cells (
44).
Moreover, our results suggest that ROS-based therapies may overcome the barriers posed by hypoxic and acidic tumor microenvironments, which often limit ROS generation in conventional therapies. By targeting both mitochondrial and cytoplasmic ROS production, this approach may yield more consistent therapeutic outcomes. The persistent oxidative imbalance observed could serve as a preparatory phase for chemoimmunotherapy. For instance, the Na2S2O8 nanoparticle system has been shown to disrupt cellular osmolarity via Na⁺ ion release, thereby disturbing ion homeostasis and sensitizing cancer cells to therapy.
Additionally, tailoring the physicochemical properties of NPs to activate diverse cell death pathways — such as pyroptosis — presents an exciting opportunity to exploit inflammatory signaling and further enhance anti-tumor immunity. In particular, our findings demonstrate that NPs selectively disrupt oxidative stress regulation, mirroring mechanisms involved in the metabolic collapse of therapy-resistant cancer cells via inhibition of mitochondrial oxidative phosphorylation (OXPHOS). This strategy holds significant promise, especially given the reprogrammed metabolic nature of cancer cell mitochondria, which support rapid proliferation and resistance development (
44).
While this study offers valuable insights into the therapeutic potential of NPs for inducing cell death in cancer cells, several limitations must be acknowledged. First, the study is based primarily on in vitro data derived from cell lines. In vivo validation is necessary to confirm the efficacy and safety of these nanoparticle treatments. Additionally, although ROS induction was observed, the relatively small dataset limited detailed comparisons across different types of nanoparticles (
45). The study also focused on mitochondrial and lysosomal effects, without fully addressing interactions with other organelles or broader cellular pathways that could result in off-target effects.
Long-term consequences of NP exposure were not investigated, particularly regarding their accumulation and clearance within the body — key factors in determining biocompatibility. Furthermore, the mechanisms of NP uptake and mitochondrial targeting across different cancer types were not examined, limiting the generalizability of our findings.
Future research should aim to address these limitations. In vivo studies are essential for evaluating nanoparticle pharmacokinetics, biodistribution, clearance, and long-term safety profiles. Investigations into the synergistic use of NPs with conventional chemotherapy or immunotherapy — especially in drug-resistant cancers — may uncover new therapeutic avenues. Developing environmentally responsive nanocarriers, such as those sensitive to pH or redox conditions, could enhance specificity for the acidic, hypoxic tumor microenvironment, thereby improving treatment accuracy.
One promising direction is to explore NP – cancer cell interactions more deeply, particularly for preventing tumor recurrence and metastasis. For example, mitochondrial inhibitors like Gboxin — which preferentially target OXPHOS in glioblastoma cells—demonstrate that mitochondrial disruption can achieve significant anti-tumor effects while sparing healthy cells (
46,
47). These findings collectively highlight the vast potential of NPs in advancing cancer therapeutics through precise mitochondrial targeting and oxidative stress modulation.
5.1. Conclusions
In this study, we investigated the cytotoxic effects of combining IR laser therapy with MnO and Fe2O3 NPs on cancer cells. Our findings suggest that this combination induces significant cytotoxicity, supporting its potential as a targeted therapeutic strategy. To further enhance efficacy and minimize off-target effects, future research should focus on developing NPs with functional groups designed to specifically target oxidative stress pathways reprogrammed by oncogenes.
Additionally, a more comprehensive examination of the effects of NPs on other cellular organelles and metabolic pathways is essential for understanding the broader systemic impact of nanoparticle-based cancer therapies. Despite the promising in vitro results, further in vivo studies are necessary to validate the effectiveness, safety, and translational potential of this strategy in clinical cancer treatment.