Reversible detection of phosphorylation and dephosphorylation by tip-enhanced Raman spectroscopy using a cyclopentadienyl ruthenium nanotag functionalized tip

Amine-catalyzed substitution in CpFe(CO)2I by phosphine and bisphosphine ligands

We have found that amines significantly accelerate iodide substitution in CpFe(CO)2I (1) (Cp = η5-cyclopentadienyl) with phosphines and allow the synthesis of new complexes that are not available through reactions carried out without an amine. The reaction of equimolar amounts of 1 and triphenylphosphine in toluene containing DIPA afforded [CpFe(CO)2PPh3]+I- within 5 min at room temperature in 72% yield (90% after 24 h). DIPA and pyrrolidine gave the highest yields of the tested amines. We performed a similar reaction using model bisphosphines 1,3-bis(diphenylphosphino)ethane (dppe) and 1,1'-bis(diphenylphosphino)ferrocene (dppf). The products depended on the reagent ratio and bore the CpFe(CO)2 moiety coordinated to one or two phosphine phosphorus atoms. Chelates [CpFe(CO)(dppe)]+I- (4) and [Cp2Fe2(CO)4(dppe)]2+2I- (5) were formed in 72% and 98% yield, respectively. We also performed the DIPA-catalyzed reaction of 1 with triethyl phosphite and obtained the product of an Michaelis-Arbuzov-like rearrangement, CpFe(CO)2[P(O)(OCH2CH3)2] (11). All complexes were characterized with spectroscopic analysis by NMR, FT-IR, and ESI-MS, and by XRD for three complexes. To clarify the reaction mechanism, we performed theoretical calculations of the intermolecular interactions between 1 and amine molecules. We propose two possible reaction mechanisms to explain the formation of products.

Geometrically encoded SERS nanobarcodes for the logical detection of nasopharyngeal carcinoma-related progression biomarkers

The limited availability of nasopharyngeal carcinoma-related progression biomarker array kits that offer physicians comprehensive information is disadvantageous for monitoring cancer progression. To develop a biomarker array kit, systematic identification and differentiation of a large number of distinct molecular surface-enhanced Raman scattering (SERS) reporters with high spectral temporal resolution is a major challenge. To address this unmet need, we use the chemistry of metal carbonyls to construct a series of unique SERS reporters with the potential to provide logical and highly multiplex information during testing. In this study, we report that geometric control over metal carbonyls on nanotags can produce 14 distinct barcodes that can be decoded unambiguously using commercial Raman spectroscopy. These metal carbonyl nanobarcodes are tested on human blood samples and show strong sensitivity (0.07 ng/mL limit of detection, average CV of 6.1% and >92% degree of recovery) and multiplexing capabilities for MMPs.

Probing Molecular-Scale Oxidative Generation of Quinone Methides and Their Transformation Using Tip-Enhanced Raman Spectroscopy

Quinone methides (QMs) are very important intermediates in chemistry. These species are most often generated in situ with metal oxidants and transition metal complexes. Here, tip-enhanced Raman spectroscopy (TERS) has been implemented to investigate the in situ oxidative generation of a QM species from alkylphenols facilitated by a transition metal complex. Using TERS, the metal oxidant-mediated transformation of a phenol species has been observed. The subsequent oxidative addition reaction of QM has also been identified based on distinct vibrational features, which have been assigned based on density functional theory (DFT). This study may establish TERS as a chemical detection tool for various QM-mediated reactions.

Raman Imaging: An Impending Approach Towards Cancer Diagnosis

In accordance with the recent studies, Raman spectroscopy is well experimented as a highly sensitive analytical and imaging technique in biomedical research, mainly for various disease diagnosis including cancer. In comparison with other imaging modalities, Raman spectroscopy facilitate numerous assistances owing to its low background signal, immense spatial resolution, high chemical specificity, multiplexing capability, excellent photo stability and non-invasive detection capability. In cancer diagnosis Raman imaging intervened as a promising investigative tool to provide molecular level information to differentiate the cancerous vs non-cancerous cells, tissues and even in body fluids. Anciently, spontaneous Raman scattering is very feeble due to its low signal intensity and long acquisition time but new advanced techniques like coherent Raman scattering (CRS) and surface enhanced Raman scattering (SERS) gradually superseded these issues. So, the present review focuses on the recent developments and applications of Raman spectroscopy-based imaging techniques for cancer diagnosis.