Smart Nanoparticles Are Not Smart Enough (Yet): A Cell-Aware View of Cancer Nanomedicine.

"Smart" nanoparticles are often presented as the vanguard of precision cancer therapy, defined by engineered abilities to sense predefined stimuli, enhance targeting, and control therapeutic release. Yet this notion of smartness remains largely material-centric and only partially reflects how nanomedicines behave in vivo. Cells exposed to nanoparticles are not passive recipients of engineered functions; they actively interpret these perturbations through integrated stress-response, metabolic, transcriptional, and innate immune programs. These cell-state trajectories can determine efficacy, tolerance, resistance, or toxicity, and can do so independently of uptake, biodistribution, or triggerable release efficiency. Accordingly, evaluation strategies that prioritize delivery metrics and limited a priori molecular markers may misestimate functional performance and durability. This Perspective proposes a cell-aware reframing in which smartness is defined by biological controllability: the capacity of a nanoparticle system to elicit predictable, mechanistically interpretable, and therapeutically favorable cell-state trajectories across relevant malignant and non-malignant compartments. A practical path forward is to integrate time-resolved functional profiling into benchmarking using compact response signatures that report stress buffering, immune activation or suppression, and the emergence of tolerant states. A practical path forward is to integrate time-resolved functional profiling into benchmarking using compact response signatures that report stress buffering, immune activation or suppression, and the emergence of tolerant states. Here, biological controllability refers to the ability of a nanoparticle system to reproducibly steer integrated cellular stress, metabolic, and immune programs toward predefined therapeutic endpoints while minimizing adaptive escape across heterogeneous compartments.