Strategic Timing of Gene Silencing: Cellular Kinetics-Based Administration of siRNA for Optimized Photothermal Cancer Treatment.

Heat shock protein 70 (HSP70) represents a critical barrier to effective mild-temperature photothermal therapy (MPTT), limiting its clinical utility in aggressive cancers like triple-negative breast cancer (TNBC). While small interfering RNA (siRNA)-mediated HSP70 suppression offers a promising solution, optimal timing for this therapeutic combination remains unexplored. Here, it is demonstrated that precisely timed administration significantly enhances MPTT efficacy through systematic temporal characterization of HSP70 expression dynamics. A three-component temperature-sensitive hybrid nanocarrier (I-sR@MLNP) is developed that integrates: 1) indocyanine green dimer (ICG-II) with exceptional photothermal conversion efficiency (PTCE, 95.4%); 2) macrophage membrane-derived lipid nanoparticles for active TNBC targeting through integrin α4/vascular cell adhesion molecule-1 (VCAM-1) axis; and 3) HSP70-targeting siRNA to overcome thermo-resistance. This multifunctional platform enables spatiotemporally controlled co-delivery and photo-triggered release of both therapeutic agents. Through comprehensive profiling of post-release HSP70 mRNA and protein kinetics, a critical therapeutic window is identified at 36 h post-initial treatment when siRNA-mediated suppression maximally sensitized cancer cells to subsequent thermal stress. In mouse TNBC models, this temporally optimized two-phase MPTT approach achieves superior tumor reduction compared to conventional single-treatment (+87%) or non-optimized protocols (+43%). The findings establish a novel time modulated framework for enhancing nanomedicine efficacy by aligning treatment scheduling with underlying molecular kinetics-a strategy with potential applications across various siRNA-based cancer therapies where timing of intervention may significantly impact therapeutic outcomes.