Understanding the interactions between nanomaterials and biological systems plays a pivotal role in enhancing the efficacy of nanomedicine and advancing the disease diagnosis. The nanoparticle-protein corona, an active biomolecular layer, is formed around nanoparticles (NPs) upon mixing with biological fluid. The surface layer which consists of rapidly exchanged biomolecules is called the "soft" corona. The inner layer which is more stable and tightly packed is called the "hard" corona. It has been suggested that the NP-protein corona has a decisive effect on the in vivo fate of nanomedicine upon intravenously administration into the mouse. Furthermore, the features of the NP-protein corona make it a powerful platform to enrich low-abundance proteins from serum/plasma for downstream mass-spectrometry (MS)-based proteomics for biomarker discovery and disease diagnosis.Herein, we summarize our recent work on the development of nanomedicine and disease detection from the level of nano-bio interactions between nanoparticles and biological systems. Nanomedicine has made substantial progress over the past two decades. However, the significant enhancement of overall patient survival by nanomedicine remains a challenge due to the lack of a deep understanding of nano-bio interactions in the clinical setting. The pharmacokinetic effect of the protein corona on PEGylated NPs during blood circulation indicated that the adsorbed apolipoproteins could prolong the circulation time of NPs. This mechanistic understanding of the protein corona (active biomolecule) formed around polymeric NPs offered insights into enhancing the efficacy of nanomedicine from the biological interactions point of view. Moreover, we discuss the basic rationale for developing bioresponsive cancer nanomedicine by exploiting the pathophysiological environment around the tumor, typically the pH, reactive oxygen species (ROS), and redox-responsive supramolecular motifs based on synthetic amphiphilic polymers. The protein corona in vivo determines the biological fate of NPs, whereas it opens a new avenue to enrich low abundant proteins in a biospecimen ex vivo to render them "visible" for downstream analytical workflows, such as MS-based proteomics. Blood serum/plasma, due to easy accessibility and great potential to uncover and monitor physiological and pathological changes in health and disease, has remained a major source of detecting protein biomarker candidates. Inspired by the features of the NP-protein corona, a Proteograph platform, which integrates multi-NP-protein coronas with MS for large-scale efficient and deep proteome profiling has been developed. Finally, we conclude this Account with a better understanding of nano-bio interactions to accelerate the nanomedicine translation and how MS-based proteomics can boost our understanding of the corona composition and facilitate the identification of disease biomarkers.