Gene silencing meets chemotherapy: A dual topical strategy using lipid nanoparticles against squamous cell carcinoma

The rising incidence of skin cancer represents a significant public health challenge, not only due to its clinical burden but also its psychosocial implications, necessitating the development of innovative therapeutic strategies. Gene therapy-based interventions, particularly those employing multifunctional delivery systems, have shown promise in enhancing antitumor efficacy. Here, we present a nanostructured lipid carrier (NLC) engineered for the topical co-delivery of Bcl-2-targeting siRNA and 5-fluorouracil (5-FU). The NLCs exhibited a mean particle size of ∼200 nm, a PdI of 0.25, and a zeta potential of +49 mV. Drug loading achieved ∼7.6% with 85% encapsulation efficiency for 5-FU, and approximately 60% release over 8 h, following Higuchi kinetics. In vitro and ex vivo human skin permeation assays confirmed preferential retention of both agents in the epidermis with minimal transdermal diffusion. The co-loaded NLCs demonstrated enhanced cytotoxicity (IC₅₀: 8.17 µM/0.83 nM for 5-FU/siRNA in 2D cultures; 134.4 µM/8.67 nM in 3D spheroids), mediated by clathrin-dependent endocytosis and ∼60% uptake efficiency. Functional assays revealed significant inhibition of cell migration (∼60%) and proliferation (∼3-fold), alongside efficient Bcl-2 silencing and apoptosis induction. In vivo, the NLCs suppressed tumor growth in a xenograft model, reduced inflammatory markers (MPO, NAG, TNF-α), and promoted apoptosis without inducing extracellular matrix remodeling. These findings underscore the therapeutic potential of dual-acting lipid nanoparticles for localized treatment of squamous cell carcinoma via combinatorial gene silencing and chemotherapy, offering a promising platform for advanced topical oncologic therapies.