Exploring the frontier of oral nanomedicine in colorectal cancer therapy: Folate-targeted 5FU-Nisin-Selenium conjugates and probiotic-rich diets as a novel approach

This study aimed to assess the therapeutic potential of nisin, 5-fluorouracil (5FU) and selenium encapsulated in folate-conjugated thiolated chitosan nanoparticles (N/5FU/Se@FTCsNPs), combined with a probiotic cocktail of <i>Lactobacillus acidophilus</i> and <i>Bifidobacterium bifidum</i>, against colorectal cancer (CRC). The nanoparticles (277 nm, +9.2 mV) exhibited high drug loading efficiencies (5FU: 89.11%, nisin: 70.68%) and pH-responsive release, with minimal drug release under gastric conditions and ∼60.7% release at colonic pH, facilitating targeted delivery. The formulation remained stable for over 40 d at -20 °C and 4 °C, demonstrating excellent biocompatibility (<2% hemolysis) and exhibiting strong mucoadhesive and mucus-penetrating abilities. <i>In vitro</i>, N/5FU/Se@FTCsNPs selectively targeted CT26 colon cancer cells (IC₅₀: 1.57 µg/ml) with minimal effects on healthy cells, enhanced cellular uptake, and induced ROS-mediated apoptosis. <i>In vivo</i>, oral administration-especially with probiotics-significantly reduced tumor volume, improved survival rates and alleviated chemotherapy-related side effects such as diarrhea and weight loss. Biodistribution studies confirmed increased tumor targeting and decreased off-target exposure. Mechanistically, the treatment downregulated oncogenes and inflammatory markers (2- to 12.5-fold), including <i>β-catenin, mTOR, COX-2</i> and <i>VEGF-α</i>, while upregulating tumor suppressors and protective genes (4 to 14.8 fold), such as <i>PTEN, CASP9</i> and <i>Mucin 2</i> (<i>P</i> < 0.0001). This indicates inhibition of proliferation, metastasis, inflammation, and angiogenesis, along with improved gut barrier function. Cytokine profiling and histological analysis further confirmed reduced systemic inflammation and maintained hematological safety. These findings highlight N/5FU/Se@FTCsNPs combined with probiotics as a promising, safe and effective oral therapy for CRC, leveraging microbiota modulation and targeted delivery.