Intracellularly grown gold nanoislands as SERS substrates for monitoring chromate, sulfate and nitrate localization sites in remediating bacteria biofilms by Raman chemical imaging

Abstract

Understanding the chemical composition of biofilm matrices is vital in different fields of biology such as surgery, dental medicine, synthetic grafts and bioremediation. The knowledge of biofilm development, composition, active reduction sites and remediation efficacy will help in the development of effective solutions and evaluation of remediating approaches prior to implementation. Surface-enhanced Raman spectroscopy (SERS) based imaging is an invaluable tool to obtain an understanding of the remediating efficacy of microorganisms and its role in the formation of organic and inorganic compounds in biofilms. We demonstrate for the first time, the presence of chromate, sulfate, nitrate and reduced trivalent chromium in soil biofilms. In addition, we demonstrate that SERS imaging was able to validate two observations made by previous studies on chromate/sulfate and chromate/nitrate interactions in Shewanella oneidensis MR-1 biofilms. Additionally, we show a detailed Raman mapping based evidence of the existence of chromate-sulfate competition for cellular entry. Subsequently, we use Raman mapping to study the effect of nitrate on chromate reduction. The findings presented in this paper are among the first to report- detection of multiple metallic ions in bacterial biofilms using intracellular SERS substrates. Such a detailed characterization of biofilms using gold nanoislands based SERS mapping substrate can be extended to study cellular localization of other metallic ions and chemical species of biological and toxicological significance and their effect on reduction reactions in bacterial biofilms.

Rapid on-site detection of ephedrine and its analogues used as adulterants in slimming dietary supplements by TLC-SERS

“…Although SERS imaging provides valuable spatial chemical information with image resolutions in the sub-micrometer range [32], it is still not sufficient for the on-site detection. In order to resolve the problem like R f offset or approximation and invisible TLC spot, the developed point-by-point scanning of SERS detection can be used to figure out the situation.…”

The application of Raman spectroscopy for the detection and identification of microorganisms

“…Two publications dealt with the bacterium Shewanella oneidensis MR‐1, which is capable of reducing hexavalent chromium, a highly soluble, priority pollutant and carcinogen, to stable and harmless Cr(III) complexes. In one paper, a biofilm‐gold nanoisland SERS mapping was performed to gain spatially resolved confocal Raman intensity images to map Cr(VI) bioreduction in chromate‐reducing S. oneidensis MR‐1 biofilm samples . Simultaneously, the distributions of chromate, trivalent chromium, nitrate, and sulfate were monitored to explore possible chromate–sulfate and chromate–nitrate interactions or competitions (e.g.…”

Effect of T‐DNA insertions on mRNA transcript copy numbers upstream and downstream of the insertion site in Arabidopsis thaliana explored by surface enhanced Raman spectroscopy

“…After acquisition of the spectra, a baseline correction of each spectrum was performed and the plasmon‐phonon band (180–230 cm −1 ) used as a self‐referencing parameter for normalization. This plasmon‐phonon band arises from nanoparticle/nanoparticle interactions and is established as an internal standard as described in our previous work (Ravindranath et al ., ). The corrected peak ( I 1075 ) (Figure ) was normalized against the corrected plasmon‐phonon band ( I ˜220 ), that is, I n = I 1075 / I 220 .…”