Biopolymeric Nanocarriers with Balanced Guanidinium-Choline Conjugates Enable Faster Nuclear Drug Delivery and Amplified Cancer Cell Apoptosis

Rational control over polymer surface chemistry is central to designing nanocarriers with predictable stability and intracellular trafficking. Here, we report a modular materials strategy based on poly(succinimide) to elucidate how balanced cationic functionality governs nanocarrier assembly, colloidal robustness, and nanobio interfacial interactions. Amphiphilic polymer derivatives were prepared by sequential conjugation of oleyl chains and cationic headgroups to generate three nanocarrier variants containing guanidinium and choline, choline only, or guanidinium only. Systematic physicochemical characterization revealed that cooperative guanidinium-choline conjugation is essential for colloidal stability in physiological media. In contrast, guanidinium-only nanocarriers suffer from rapid aggregation. Cellular uptake studies demonstrated that guanidinium-choline surface chemistry dictates rapid, energy-independent membrane translocation and preferential nuclear localization, while others internalized via clathrin-mediated endocytosis and remain lysosomally sequestered. Leveraging this accelerated nuclear drug delivery enables amplified cancer cell apoptosis. The direct translocation capability further facilitated rapid penetration into three-dimensional (3D) tumor spheroids, highlighting the importance of surface charge balance for transport across multicellular barriers. Collectively, this study establishes cationic conjugation balance as a parameter that links polymer design to nanocarrier stability, cellular entry mechanism, and intracellular targeting capabilities.