Label-free detection of DNA methylation by surface-enhanced Raman spectroscopy using zirconium-modified silver nanoparticles.

DNA methylation is an important feature of gene epigenetics that affects the metabolic process of organisms. Although surface-enhanced Raman spectroscopy (SERS) has demonstrated great potential in label-free DNA detection, discriminating the various processes involved in DNA methylation remains a challenge. DNA molecules fold themselves, wrapping the hydrophobic bases, thus making it difficult for traditional methods to detect single-base signals. In this study, we develop a SERS platform for detecting DNA via modifying silver nanoparticles by zirconium ions to obtain the DNA fingerprint information of base methylations (N6-methylated adenine and 5-methylated cytosine). Zirconium ions open the folded DNA molecules, enabling SERS signals of the four DNA bases (A, C, G, T) to be obtained as well as identification of the subtle differences between normal and methylated DNA with single base-level sensitivity. Moreover, the identifying information of DNA methylation was obtained by combining principal component analysis (PCA) with 2D correlation spectroscopy analysis. The findings of this study provide a substantial progress for current platforms for DNA sequencing, genetic testing, and gene-disease treatment.

Electrochemically renewable SERS sensor: A new platform for the detection of metabolites involved in peroxide production.

The accurate detection of hydrogen peroxide (H2O2)-involved metabolites plays a significant role in the early diagnosis of metabolism-associated diseases, whereas most of current metabolite-sensing systems are often hindered by low sensitivity, interference of coexisting species, or tedious preparation. Herein, an electrochemistry-regenerated surface-enhanced Raman scattering (SERS) sensor was developed to serve as a universal platform for detecting H2O2-involved metabolites. The SERS sensor was constructed by modifying newly synthesized 2-mercaptohydroquinone (2-MHQ) molecules on the surface of gold nanoparticles (AuNPs) that were electrochemically predeposited on an ITO electrode. Metabolites were detected through the changes in the SERS spectrum as a result of the reaction of 2-MHQ with H2O2 induced by the metabolites. Combining the superiority of SERS fingerprint identification and the specificity of the related enzymatic reactions producing H2O2, the designed SERS sensor was highly selective in detecting glucose and uric acid as models of H2O2-involved metabolite with limits of detection (LODs) of 0.159 µM and 0.0857 µM, respectively. Moreover, the sensor maintained a high SERS activity even after more than 10 electrochemical regenerations within 2 min, demonstrating its effectiveness for the rapid detection of various metabolites with electrochemistry-driven regulation. Importantly, the presented SERS sensor showed considerable practicability for the detection of metabolites in real serum samples. Accordingly, the SERS sensor is a new detection platform for H2O2-involved metabolites detection in biological fluids, which may aid the early diagnosis of metabolism-related diseases.

Sensitive and selective SERS probe for detecting the activity of γ-glutamyl transpeptidase in serum.

γ-Glutamyl transpeptidase (GGT) has attracted considerable attention for its regulatory effect on glutathione metabolism in living organisms; further, its close relationship with physiological dysfunctions such as hepatitis and liver cancers has enhanced its applicability. Therefore, the accurate detection of GGT levels is particularly important for the early diagnosis of diseases. Thus, we herein report the development of a surface-enhanced Raman spectroscopic (SERS) probe, namely bis-s,s'-((s)-4,4'-thiolphenylamide-Glu) (b-(s)-TPA-Glu), that comprises of a γ-glutamyl moiety for detection of the GGT activity. In this system, detection was achieved by observing differences in the SERS spectral profiles of the b-(s)-TPA-Glu probe and its corresponding hydrolysis product that resulted from the catalytic action of GGT. This SERS probe system exhibited a high selectivity toward GGT due to a combination of its specific catalytic action and the distinctive spectroscopic fingerprint of the SERS technique. The developed SERS approach was also found to be approximately linear in the range of 0.2-200 U/L, and a limit of detection of 0.09 U/L was determined. Furthermore, the proposed SERS method was suitable for detection of the GGT activity of clinical serum samples and also for evaluation of the inhibitors of GGT. Consequently, this approach is considered to be a promising diagnostic and drug screening tool for GGT-associated diseases.

Simultaneous Detection of Intracellular Nitric Oxide and Peroxynitrite by a Surface-Enhanced Raman Scattering Nanosensor with Dual Reactivity.

A functional surface-enhanced Raman scattering (SERS) nanosensor which can simultaneously detect nitric oxide (NO) and peroxynitrite (ONOO-) in living cells is explored. The SERS nanosensor is fabricated through modifying gold nanoparticles (AuNPs) with newly synthesized 3,4-diaminophenylboronic acid pinacol ester (DAPBAP), which has two reactive groups. The simultaneous detection achieved in this work is not only because of the SERS spectral changes of the nanosensor resulting from the dual reactivity of DAPBAP on AuNPs with NO and ONOO- but also by the narrow SERS bands suitable for multiplex detection. Owing to the combination of SERS fingerprinting information and chemical reaction specificity, the nanosensor has great selectivity for NO and ONOO-, respectively. In addition, the nanosensor has a wide linearity range from 0 to 1.0 × 10-4 M with a submicromolar sensitivity. More importantly, simultaneous monitoring of NO and ONOO- in the Raw264.7 cells has been fulfilled by this functional nanosensor, which shows that the SERS strategy will be promising in comprehension of the physiological issues related with NO and ONOO-.