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Abstract Long-term live cell tracking is desirable and necessary to understand the dynamics and complexity of biological interactions in stem cells and cancer cells. Conventional live cells fluorescence trackers are generally non-degradable and are showing increased toxicity concerns during the long-term application. Previously we developed biodegradable fluorescent poly(citrate)-based hybrid elastomers for bone regeneration applications. Here, we fabricated the photoluminescent poly(citrate-siloxane) nanoparticles (PCSNPs) through an oil/water emulsion method and demonstrated their long-term live stem cells/cancer cells imaging applications. PCSNPs showed a uniform size distribution (mean diameter 120 nm) and highly stable dispersability (above 30 days) in various physiological medium, as well as excellent fluorescent properties and photostability. PCSNPs possess excellent cellular biocompatibility, which could be efficiently internalized by cells and selectively image the cell lysosome with a high photostability. Compared with commercial Cell Tracker™ Green and Cell Tracker™ Red, the adipose-derived mesenchymal stem cells or human hepatoma cells were stably labeled by PCSNPs for over 14 days as they grew and developed (7 passages). Additionally, PCSNPs efficiently tracked cells up to 7 days in vivo through a non-invasively way compared with 1 day of commercial tracker. This study demonstrates an important strategy to design biodegradable multifunctional delivery platforms for biomedical applications such as long-term bioimaging. Graphical abstract Unlabelled Image Highlights • Biodegradable PCS nanoparticles were fabricated through a facile emulsion technology. • PCSNPs showed a monodispersed size (120 nm) and highly stable dispersability. • PCSNPs exhibited excellent fluorescent properties and photostability. • PCSNPs possess excellent cellular biocompatibility and long term cell tracking. [ABSTRACT FROM AUTHOR]

A bioorthogonal Raman reporter-embedded Au-core and polydopamine-shell nanoprobe was initially designed and synthesized for live cell surface-enhanced Raman scattering (SERS) imaging in Raman-silent region. The firstly synthetic bioorthogonal Raman reporter (E)-2- ((4-(phenylethynyl) benzylidene)amino)ethanethiol (PBAT) provided intense Raman signal at 2220cm-1 in Raman-silent region. And its synthetic method was environmentally benign, high yield and easy in operation. In addition, the hydrophobicity of PBAT led to slightly aggregation of gold nanoparticles, which enhance the SERS intensity of the nanoprobe through hot spots. Furthermore, owing to the remarkable biocompatibility of polydopamine (PDA), the SERS nanoprobe can be smoothly internalized into cancer cells to realize SERS imaging in Raman-silent region. Finally, the SERS mapping results confirmed that nanoprobe exhibited strong SERS signal intensity, excellent stability in complex biological environment and low toxicity inside live cancer cells. Therefore, the reporter-embedded core-shell nanoprobe has enormous potential of applications in biomedical diagnostics in the near future. Graphical abstractHighlights· One-step synthetic method of thiol and alkynyl contained bioorthogonal SERS reporter is environmentally benign, high yield and easy in operation. · Au@PBAT@PDA nanoparticles exhibit strong SERS signal intensity, excellent stability in complex biological environment. · Au@PBAT@PDA nanoparticles show good imaging results for live cancer cell SERS imaging in Raman-silent region. · The rich functional groups (i.e., catechol and amine) on PDA surface provide a broad platform for further modification in biomedical application. · A Raman-silent region nanoprobe was synthesized for live cell SERS imaging. [ABSTRACT FROM AUTHOR]