Synthesis and Characterization of Elongated-Shaped Silver Nanoparticles as a Biocompatible Anisotropic SERS Probe for Intracellular Imaging: Theoretical Modeling and Experimental Verification

• Main Authors: Carlos Caro, Pedro Quaresma, Eulália Pereira, Jaime Franco, Manuel Pernia Leal, Maria Luisa García-Martín, Jose Luis Royo, Jose Maria Oliva-Montero, Patrick Jacques Merkling, Ana Paula Zaderenko, David Pozo, Ricardo Franco
• Format: Article
• Language: English
• Published: MDPI AG 2019-02-01
• Series: Nanomaterials
• Subjects: surface enhanced Raman scattering; SERS; finite element method; density functional theory calculations; cell labeling; cancer
• Online Access: https://www.mdpi.com/2079-4991/9/2/256
• ISSN: 2079-4991

Progress in the field of biocompatible SERS nanoparticles has promising prospects for biomedical applications. In this work, we have developed a biocompatible Raman probe by combining anisotropic silver nanoparticles with the dye rhodamine 6G followed by subsequent coating with bovine serum albumin. This nanosystem presents strong SERS capabilities in the near infrared (NIR) with a very high (2.7 × 10⁷) analytical enhancement factor. Theoretical calculations reveal the effects of the electromagnetic and chemical mechanisms in the observed SERS effect for this nanosystem. Finite element method (FEM) calculations showed a considerable near field enhancement in NIR. Using density functional quantum chemical calculations, the chemical enhancement mechanism of rhodamine 6G by interaction with the nanoparticles was probed, allowing us to calculate spectra that closely reproduce the experimental results. The nanosystem was tested in cell culture experiments, showing cell internalization and also proving to be completely biocompatible, as no cell death was observed. Using a NIR laser, SERS signals could be detected even from inside cells, proving the applicability of this nanosystem as a biocompatible SERS probe.