While surface-enhanced Raman spectroscopy (SERS) has been attracting a continuously increasing interest of scientific community since its discovery, it has enjoyed a particularly rapid growth in the last decade. Most notable recent advances in SERS include novel technological approaches to SERS substrates and innovative applications of SERS in medicine and molecular biology. While a number of excellent reviews devoted to SERS appeared in the literature over the last two decades, we will focus this paper more specifically on several promising trends that have been highlighted less frequently. In particular, we will briefly overview strategies in designing and fabricating SERS substrates using deterministic patterning and then cover most recent biological applications of SERS.

The increasing applications of surface-enhanced Raman scattering (SERS) has led to the development of various SERS-active platforms (SERS substrates) for SERS measurement. This work reviews the current optimization techniques available for improving the performance of some of these SERS substrates. The work particularly identifies self-assembled-monolayer- (SAM-) based substrate modification for optimum SERS activity and wider applications. An overview of SERS, SAM, and studies involving SAM-modified substrates is highlighted. The focus of the paper then shifts to the use of SAMs to improve analytical applications of SERS substrates by addressing issues including long-term stability, selectivity, reproducibility, and functionalization, and so forth. The paper elaborates on the use of SAMs to achieve optimum SERS enhancement. Specific examples are based on novel multilayered SERS substrates developed in the author’s laboratory where SAMs have been demonstrated as excellent dielectric spacers for improving SERS enhancement more than 20-fold relative to conventional single layer SERS substrates. Such substrate optimization can significantly improve the sensitivity of the SERS method for analyte detection.

Evaluation of joint toxic action of metal ion mixtures is one of the priority research areas due to the simultaneous occurrence of metals in the environment and the health risk they posed to humans and the environment as a mixture. Individual and composite mixture acute toxicities of arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb), which are among the top eight toxic chemicals, were characterized at varying concentrations. MCF 7 cell lines were exposed to individual and composite mixtures containing the four metal ions in the proportion of their EPA's MCL for 24 hours, and the concentration-response data were generated spectrofluorometrically. Acute toxicities were estimated based on the uptake of fluorescence diacetate dye. Toxicological interactions among the four metals were profiled, based on computed interactive index. Results demonstrated that the toxicity of each of the metal ions was enhanced in the composite mixture, and the metals demonstrated differential interactions in a concentration dependent manner. Lead, the least toxic among the four metals, showed the highest enhancement (23-to 64-fold) in toxicity when in the mixture. Interaction among the four metals was largely additive although there was slight departures form additivity at the two extremes of the concentration range.

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