High-sensitive bioorthogonal SERS tag for live cancer cell imaging by self-assembling core-satellites structure gold-silver nanocomposite

A novel, high sensitivity, biocompatible SERS tag with core-shell structure based on gold nanoparticles containing alkynyl molecule core-silver nanoparticle satellites shell was fabricated for the first time to be used for live cancer cells Surface enhanced Raman scattering (SERS) imaging. (E)-2-((4-(phenylethynyl)benzylidene) amino) ethanethiol (PBAT) synthesized facilely in our lab is the Raman-silence region reporter which is advantage for bioorthogonal SERS cell imaging. In order to enhance the intensity of the Raman tags for live cancer cell imaging, a series of news measures have been adopted. Firstly, reporter molecules of the PBAT were added twice, which is embedded in the gold core with the reduction of tetrachloroaurate and then PBAT is conjugated again on disperse gold nanoparticles (PBAT-Au). Furthermore, numerous Ag nanoparticles self assembly were densely arranged around PBAT-Au core surface (PBAT- Au@Ag), just like a circle of satellites cluster, which produce obvious "hot spots" effects enhancing the signal of the Raman tags enormously. Finally, Bovine serum albumin (BSA) and polydopamine (PDA) coated on the PBAT- Au@Ag successively, defined as (PBAT-Au@Ag@BSA@PDA), which make as-synthesized nanocomposites own features of bio-compatibility and facilitates antibody modification. Compared with Au@PBAT@PDA, PBAT-Au@Ag@BSA@PDA with core shell satellites structure showed 10-fold increase in the Raman signals intensity. Moreover, PBAT-Au@Ag@BSA@PDA nanocomposites were successfully applied in the Raman imaging of human glioma cells (U251) by the recognition of the anti-epidermal growth factor receptor (EGFR). All experimental results demonstrated that the nanocomposites have high value and huge potential application in the live cancer cells imaging and biomedical diagnostics in the near future.