In one aspect, compositions comprising a population of core-shell nanoparticles are described herein. In some cases, the population of core-shell nanoparticles comprises a core component and a shell component encapsulating or surrounding the core component. Additionally, one or more radiosensitizers are disposed in or dispersed throughout the core component, or an interior region of the core component. Similarly, one or more chemotherapeutic agents are disposed in or dispersed throughout the shell component, or an interior region of the shell component. Moreover, in some cases, the core component is formed from one or more biodegradable polymers. Further, in some instances, the shell component is formed from one or more stimuli responsive polymers, such as a temperature-responsive polymer and/or pH-responsive polymer.