Targeted delivery of DAPT using dual antibody functionalized solid lipid nanoparticles for enhanced anti-tumour activity against triple negative breast cancer.

Triple-negative breast cancer (TNBC) is a subtype known for its aggressive nature, high rates of recurrence, and treatment resistance, largely attributed to the presence of breast cancer stem cells (BCSCs). Traditional therapies often struggle to eliminate BCSCs, which contributes to tumor recurrence. One promising strategy for addressing this challenge is targeting the Notch signaling pathway, which plays a critical role in the self-renewal and maintenance of BCSCs. DAPT, a potent γ-secretase inhibitor that down-regulates Notch, has limited use due to poor bio-distribution and off-target effects. To achieve the targeted delivery of DAPT to TNBC cells, we encapsulated DAPT in solid lipid nanoparticles (SLNs), and the surface of SLNs was further decorated with DLL4 and DR5 antibodies to produce DLL4-DR5-DAPT@SLNs (∼256 ± 3 nm). The developed DLL4-DR5-DAPT@SLNs have been characterized using various spectroscopy and microscopy techniques. The in vitro studies demonstrated that, DLL4-DR5-DAPT@SLNs can effectively internalize, showing excellent cytotoxicity and efficiently suppress cell migration and invasion by reducing the expression of Notch-1, promote apoptosis by increasing the expression of Caspase-8 and eventually inhibit the process of EMT via up-regulating the E-cadherin and down-regulating the vimentin expression at protein level. Further, in vivo studies demonstrated that DLL4-DR5-DAPT@SLNs exhibit targeted accumulation within tumors, resulting in a notable reduction in tumor size from 2.3 cm to 0.9 cm and a decrease in tumor volume from 2506.2 ± 104.6 mm to 832.4 ± 93.1 mm. The targeted treatment significantly reduced the overall tumor burden, contributing to the extension of long-term survival rates. The findings reveal that functionalization of DLL4 and DR5 significantly enhances the therapeutic delivery of DAPT to TNBC cells via simultaneously inhibiting the Notch signaling pathway and promoting apoptosis. The developed nanosystem addresses limitations associated with conventional therapies, such as insufficient targeting, systemic toxicity, and poor bioavailability. This study presents the innovative nanosystem as a potential treatment strategy for TNBC, aiming to enhance treatment efficacy and reduce off-target effects.