Smart stimuli-responsive polymeric nanoparticles in precision cancer therapy: From tumor microenvironment triggers to controlled release

Stimuli-responsive polymeric nanoparticles (SRPNs) constitute an advanced class of nanocarriers capable of converting tumor microenvironment (TME)–associated biochemical and physicochemical cues into spatiotemporally controlled drug release, offering an effective strategy for precision cancer therapy. Unlike conventional polymeric nanoparticles that rely predominantly on passive accumulation, SRPNs enable tumor-selective activation through rationally engineered responsiveness to endogenous signals such as acidity, redox imbalance (elevated glutathione and reactive oxygen species), hypoxia, and enzyme overexpression. This review summarizes recent progress in SRPN design with a focus on emerging delivery paradigms rather than isolated stimulus types. Particular attention is given to dual- and multi-stimuli–responsive systems, in which sequential or logic-gated activation mechanisms integrate multiple TME cues to achieve cascade drug release, thereby improving delivery robustness in the context of tumor heterogeneity and reducing premature or off-target release. Exogenous stimuli, including light, ultrasound, temperature, and magnetic fields, are discussed as externally programmable inputs that provide precise temporal control and synergize with endogenous triggers. In addition, this review highlights the concept of stimulus-regulated dynamic targeting, in which ligand–receptor interactions are conditionally activated through environment-responsive shielding or exposure, enabling the coordinated integration of prolonged circulation, deep tumor penetration, and efficient cellular internalization. Core drug-loading and release strategies—physical encapsulation, cleavable polymer–drug conjugation, and electrostatic complexation—are discussed in relation to these dynamic and logic-guided delivery mechanisms. Key biological and translational barriers, including protein corona formation, immune clearance, limited extravasation and intratumoral penetration, endosomal escape inefficiency, scalable manufacturing challenges, and the limited predictive value of conventional animal models, are critically analyzed. Based on these considerations, future directions are proposed toward biodegradable and programmable SRPNs with cascade responsiveness, as well as more human-relevant evaluation platforms such as organoids and organ-on-a-chip systems. Overall, this review positions SRPNs not merely as stimulus-sensitive carriers, but as adaptive, logic-guided nanotherapeutic systems, providing a conceptual framework to guide rational design and clinical translation in precision oncology. • We summarize design principles of stimuli-responsive polymeric nanoparticles (SRPNs) for precision cancer therapy. • Endogenous tumor microenvironment triggers (pH, redox, hypoxia, enzymes) are mapped to stimulus-cleavable motifs and activation mechanisms. • Exogenous stimuli (temperature, light, ultrasound, magnetic fields) enabling on-demand activation and controllable release are critically reviewed. • Dual/multi-stimuli logic, drug-loading strategies, and targeting paradigms are compared to address tumor heterogeneity and delivery barriers. • Translational challenges (biosafety, scalable manufacturing, reproducibility, and model limitations) are discussed with actionable future directions.