Effect of Mesoporous Silica-Loaded Anticancer Drugs on 3D vs 2D Models of Colon Cancer Cells

Colorectal cancer (CRC) stands as a prominent cause of cancer-related mortality globally. Conventional chemotherapy suffers from limited efficacy due to its non-specificity and reduced bioavailability at tumour sites, necessitating the development of nanocarriers for enhanced drug delivery. Furthermore, tumour resistance to anticancer drugs warrants evaluation in a suitable 3D model mimicking in vivo tumours. This study investigated the impact of a potential chalcone-based anticancer drug, DMU121, and oxaliplatin (OXA) used in treating CRC. Both anticancer drugs were loaded onto mesoporous silica nanoparticles (MSNs) and tested on 3D spheroids and 2D monolayer cells of the HCT116 colon cancer cell line. Due to its poor water solubility, DMU121, a synthesised chalcone with potential anticancer properties, was encapsulated onto MSNs. MSNs, biocompatible nanocarriers, offer sustained and controlled drug delivery, improving solubility and bioavailability. Anticancer drugs DMU121 and OXA were encapsulated via electrospraying, and various physicochemical and thermal properties of the anticancer drug formulations were evaluated. Encapsulation efficiency revealed approximately 80% of DMU121 encapsulated within MSN pores. Characterisation techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), dynamic light scattering (DLS) and zeta potential analysis confirmed amorphous state, stability, and suitable particle size for cellular uptake. In vitro release studies demonstrated sustained drug release over 72 hours, with greater stability observed at 4°C. Cytochrome P450 (CYP) enzymes play a central role in drug metabolism, with this study revealing differential expression in 2D vs 3D cellular models. Real-time PCR showed higher baseline expression of CYP enzymes such as CYP1A1, CYP1A2 and CYP1B1 in 3D spheroids than in 2D monolayer cells (p = 0.0069, p = 0.00001, and p = 0.0004, respectively). Treatment with DMU121MSN (p < 0.001) and OXAMSN (p < 0.01) increased CYP1A1, CYP1A2, and CYP1B1 expression in both 2D and 3D cellular models. Cytotoxic effects of encapsulated anticancer drug formulations were assessed using MTT assay on 2D monolayer cells and 3D spheroids. DMU121MSN and OXAMSN exhibited greater concentration- and time-dependent cytotoxicity (p <0.01) in 2D monolayer cells than in 3D spheroids, indicating enhanced efficacy of DMU121 in 2D models. p53 expression increased in 2D cells post-treatment, correlating with increased cytotoxicity in MSN-loaded formulations. Mucins, known to confer resistance to anticancer drugs in tumours, show altered expression in CRC. Immunocytochemistry and immunofluorescence techniques revealed higher MUC1 expression in 3D spheroids compared to 2D monolayer cells. Increased MUC1 expression correlated with decreased cytotoxicity in 3D spheroids, suggesting a barrier effect against MSN-loaded formulations. While the result showed increased CYP enzyme expression, the increased MUC1 expression seems to be a barrier to DMU121MSN and its ability to induce cell death in 3D spheroids. Thus, this study highlights the importance of MSN as a suitable nanocarrier for drug delivery and also emphasises the need for a representative 3D model to screen for MSN-loaded cytotoxic drugs.