Raman and Surface-Enhanced Raman Scattering Detection in Flowing Solutions for Complex Mixture Analysis.

Raman scattering provides a chemical-specific and label-free method for identifying and quantifying molecules in flowing solutions. This review provides a comprehensive examination of the application of Raman spectroscopy and surface-enhanced Raman scattering (SERS) to flowing liquid samples. We summarize developments in online and at-line detection using Raman and SERS analysis, including the design of microfluidic devices, the development of unique SERS substrates, novel sampling interfaces, and coupling these approaches to fluid-based chemical separations (e.g., chromatography and electrophoresis). The article highlights the challenges and limitations associated with these techniques and provides examples of their applications in a variety of fields, including chemistry, biology, and environmental science. Overall, this review demonstrates the utility of Raman and SERS for analysis of complex mixtures and highlights the potential for further development and optimization of these techniques. Expected final online publication date for the Annual Review of Analytical Chemistry, Volume 17 is May 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Electric Potential Induced Prevention and Removal of an Algal Biofoulant from Planar SERS Substrates.

Ulva zoospores are widespread marine macroalgae and a common organism found in biofouling communities due to their strong adhesive properties and quick settlement times. Using Ulva as a model organism, a strategy is presented where direct-current (DC) electric potentials are applied in conjunction with surface-enhanced Raman spectroscopy (SERS) to characterize, remove, and prevent Ulva from forming a biofilm on gold-capped nanopillar SERS substrates. Experiments were conducted within a poly(tetrafluoroethylene) (PTFE) flow channel device where the SERS substrates were used as an electrode. Ulva density, determined in situ by SERS and ex situ by electron and fluorescence microscopy, decreased under successively increasing low negative potentials up to -1.0 V. The presence of damaged Ulva suggests that the applied potential led to spore rupture. At the highest negative applied potential (-1.0 V), microparticles containing copper, which is known for its antimicrobial properties, were associated with Ulva on the SERS substrate and the lowest Ulva density was observed. These findings indicate that (1) SERS can be employed to study biofilm formation on nanostructured metal surfaces and (2) applying low-voltage electric potentials may be used to control Ulva biofouling on SERS marine sensors.

Organic Anion Detection with Functionalized SERS Substrates via Coupled Electrokinetic Preconcentration, Analyte Capture, and Charge Transfer.

Detecting ultralow concentrations of anionic analytes in solution by surface-enhanced Raman spectroscopy (SERS) remains challenging due to their low affinity for SERS substrates. Two strategies were examined to enable in situ, liquid phase detection using 5(6)-carboxyfluorescein (5(6)-FAM) as a model analyte: functionalization of a gold nanopillar substrate with cationic cysteamine self-assembled monolayer (CA-SAM) and electrokinetic preconcentration (EP-SERS) with potentials ranging from 0 to +500 mV. The CA-SAM did not enable detection without an applied field, likely due to insufficient accumulation of 5(6)-FAM on the substrate surface limited by passive diffusion. 5(6)-FAM could only be reliably detected with an applied electric field with the charged molecules driven by electroconvection to the substrate surface and the SERS intensity following the Langmuir adsorption model. The obtained limits of detection (LODs) with an applied field were 97.5 and 6.4 nM on bare and CA-SAM substrates, respectively. For the CA-SAM substrates, both the ligand and analyte displayed an ∼15-fold signal enhancement with an applied field, revealing an additional enhancement due to charge-transfer resonance taking place between the metal and 5(6)-FAM that improved the LOD by an order of magnitude.

PFAS fluidize synthetic and bacterial lipid monolayers based on hydrophobicity and lipid charge.

Poly- and Perfluoroalkyl substances (PFASs) are pollutants of emerging concern that persist in nature and pose environmental health and safety risks. PFAS disrupt biological membranes resulting in cellular inhibition, but the mechanism of disruption and the role of lipid composition remain unclear. We examine the role of phospholipid saturation and headgroup charge on the interactions between PFASs and phospholipid monolayers comprised of synthetic phosphocholine (PC) and phosphoglycerol (PG) lipids and prepared from bacteria membrane extracts rich in PG lipids from an environmentally relevant marine bacterium Alcanivorax borkumensis. When deposited on a buffered subphase containing PFAS, PFAS mixed within and fluidized zwitterionic and net-anionic monolayers leading to increases in monolayer compressibility that were driven by a combination of PFAS hydrophobicity and monolayer charge density. Differences in the monolayer response using saturated or unsaturated lipids are attributed to the ability of the unsaturated lipids to accommodate PFAS within 'void space' arising from the bent lipid tails. Similar fluidization and compressibility behavior were also observed in A. borkumensis lipid monolayers. This work provides new insight into PFAS partitioning into bacterial membranes and the effect PFAS have on the physicomechanical properties of zwitterionic and charged lipid monolayers.

Comparing the Efficacy of Leishman-Giemsa Cocktail Stain, Giemsa Stain, and Papanicolaou Stain in Potentially Malignant Oral Lesions: A Study on 540 Cytological Samples.

BACKGROUND: This study was planned to compare and evaluate the staining efficacy of Leishman-Giemsa cocktail (LG), Papanicolaou, and Giemsa stain (G) in potentially malignant disorders and malignant lesions. AIMS: To evaluate the quality of nuclear and cytoplasmic staining of LG with G, and rapid Papanicolaou stain (Pap) and to compare the total staining efficiency of LG against G and P. MATERIALS AND METHODS: One hundred and eighty participants were studied under three groups - 60 as healthy controls, 60 with potentially malignant disorders, and 60 with malignant lesions; smears were taken thrice from the buccal mucosa. One smear was fixed with Bio-Fix spray and other two smears were allowed to air dry for 2-3 minutes. Then, the ethyl alcohol-fixed smear was stained with Pap and the two other air-dried smears were stained with G and LG stains. Analysis was done using Friedman test and Wilcoxon Signed Rank Test with SPSS Version 15.0. RESULTS: In the normal group, staining of LG was highly significant (P < 0.001). Among potentially malignant lesions, LG was observed to be highly significant (P < 0.001) when compared with G and was not significant when compared with Pap (P = 0.186). In the malignant group, LG was highly significant (P < 0.001). LG was superior with the highest average staining score of (2.018) than Pap and G. CONCLUSION: LG cocktail is a better stain with excellent cytoplasmic and nuclear staining intensity compared to Pap and G stains.

Nanotechnology in oral cancer: A comprehensive review.

Oral health could be maintained by application of this technology in prevention, diagnosis and treatment. Oral cancer is a debilitating disease, and numerous research activities are being pursued worldwide to combat this deleterious process. Nanotechnology is very diverse field that has revolutionized the industry and is setting new trends in the management of oral cancer. Hence, we performed a PubMed search on nanotechnology in oral cancer and found 211 articles related to this search. We have reviewed the reported literature to the best of our abilities and summarized the various aspects of nanotechnology, its role in diagnosis - nanodiagnostics and treatment of oral cancer - nanotherapeutics in this article.