Designing Gold Nanoparticle-Ensembles as Surface Enhanced Raman Scattering Tags inside Human Retinal Cells

Sanda Boca,Dumitrita Rugina,Nicolae Leopold,Adela Pintea,Simion Astilean

doi:10.1155/2012/961216

Abstract

Apart from the traditional development of surface-enhanced raman scattering (SERS) substrates for ultrasensitive spectroscopic analysis, an increasing interest is given nowadays to the design of the so-called SERS nanotags which integrate multiple SERS applications into single plasmonic nanoparticles. The fabrication of SERS tags is still a challenging task due to the complicated fabrication process. Typically, SERS tags are hybrid nanoconstructs consisting in a unique plasmonic nanoobject encoded with specific reporter molecules and enveloped in a protective shell that provides both biocompatibility and targeting function. Herein, we produce effective SERS tags consisting in small aggregates of gold nanoparticles (mainly dimers and trimers) which are captured from solution and then transferred into cells to perform as individual plasmonic nanostructures. Actually the small aggregates formed under controlled conditions are stabilized in solution by interlocking into a polymeric envelope made of thiol-modified poly(ethylene) glycol (PEG-SH). No further encoding operation is necessary in our case since part of ascorbic acid used as reducing agent remains attached in the interparticle junctions, providing persistent and strong SERS signal when the fabricated tags are internalized by human retinal cells. Our studies demonstrate a promising potential of new SERS-active nanoparticles to serve as effective reporters for biomedical tracing and imaging.

Highlights

The development of various strategies for the preparation of new optical labels as probes for detection and imaging has gained tremendous interest in the past years [1,2,3,4]
We produce effective surface-enhanced Raman scattering (SERS) tags consisting in small aggregates of gold nanoparticles which are captured from solution and transferred into cells to perform as individual plasmonic nanostructures
When the maximum concentration of the polymer was added to the colloidal nanoparticles, the band corresponding to ensembles of nanoparticles featured only negligible red shift, indicating that further aggregation was inhibited and the formed PEG-GENs remained in that aggregation state thereafter

Summary

Introduction

The development of various strategies for the preparation of new optical labels as probes for detection and imaging has gained tremendous interest in the past years [1,2,3,4]. Using SERS technique, different Raman reporters can be simultaneously excited with a single light source of choice (such as near-infrared light for human tissue) to achieve quantitative multiplexed detection [9] These advantages confer to such SERS labels wide applicability in biomedical systems. The particles were fabricated by an alternative method of the commonly Turkevich-Frens synthesis, by the use of ascorbic acid as reducer of the gold salt [18] This class of nanoparticles does not require any supplementary operation of encoding since ascorbic acid remains attached in between nanoparticles and give a persistent and strong SERS signal when nano-tags are internalized by cells. The signal reproducibility in simulated body fluid salted solution, and in vitro measurements on human retinal cells highlight the potential of such SERSactive nanoparticles to serve as biomedical imaging tools

Experimental Section

Results and Discussion

Conclusions