Surface-Enhanced Raman Spectroscopy (SERS) Cellular Imaging of Intracellulary Biosynthesized Gold Nanoparticles

Abstract

Green algae biosynthesize gold nanoparticles (AuNPs) in the presence of dissolved gold, but the precise biosynthesis mechanism remains unclear. Furthermore, few surface-enhanced Raman spectroscopy (SERS) spectra and even fewer SERS cellular images have been collected of intracellularly grown gold nanoparticles, despite the detailed information SERS can provide about nanosurface-associated molecules. In this effort, SERS imaging was used to detect intracellular and extracellular gold nanoparticles biosynthesized by the green algae Pseudokirchneriella subcapitata to identify surface-associated biomolecules and to evaluate the nanoparticle biosynthesis mechanism. Three-dimensional SERS spectral maps imaged AuNPs biosynthesized in the presence of 0.005–0.5 mM HAuCl4 over a variety of pH conditions. Algal growth and AuNP biosynthesis were monitored over a 72 h exposure period using UV–vis spectroscopy, electron microscopy, and elemental analysis. Principle component analysis (PCA) and cluster analysis of SERS ...