Theoretical Principles of Fluorescence Spectroscopy

A Comprehensive Review on the Excitation-Emission Matrix Fluorescence Spectroscopic Characterization of Petroleum-Containing Substances: Principles, Methods, and Applications

Petroleum-containing substance (PCS) is a general term used for petroleum and its derivatives. A comprehensive characterization of PCSs is crucial for resource exploitation, economic development and environmental protection. Fluorescence spectroscopy, especially excitation-emission matrix fluorescence (EEMF) spectroscopy, has been proved to be a powerful tool to characterize PCSs since its remarkable sensitivity, selectivity, simplicity and high efficiency. However, there is a lack of systematic review focusing on this field in the literature. This paper reviews the fundamental principles and measurements of EEMF for characterizing PCSs, and makes a systematic introduction to various information mining methods including basic peak information extraction, spectral parameterization and some commonly used chemometric methods. In addition, recent advances in applying EEMF to characterize PCSs during the whole life-cycle process of petroleum are also revisited. Furthermore, the current limitations of EEMF in the measurement and characterization of PCSs are discussed and corresponding solutions are provided. For promoting the future development of this field, the urgent need to build a relatively complete EEMF fingerprint library to trace PCSs, not only pollutants but also crude oil and petroleum products, is proposed. Finally, the extensions of EEMF to high-dimensional chemometrics and deep learning are prospected, with the expectation of solving more complex systems and problems.

Investigation of eco-friendly fluorescence quenching probes for assessment of acemetacin using silver nanoparticles and acriflavine reagent

The non-steroidal anti-inflammatory medication acemetacin was assessed via two straightforward green spectrofluorimetric techniques. The quenching-dependent derivatizing spectrofluorimetric reactions are the master point of this study. Acriflavine-based method (Method I) depends on forming an ion association complex between acriflavine and the drug in a ratio of 1:1, decreasing the former's fluorescence intensity. Acriflavine or Ag NP's intensity-related quenching action goes linearly with the acemetacin concentration in the 2.0-20.0 µg/mL and 1.0-16.0 µg/mL ranges, respectively. The second quenching mechanism depends on using the silver nanoparticles (Ag NP's) as a fluorescence probe (Method II); Ag NP's were prepared from reducing silver nitrate using sodium borohydride. Both methods could be applied to determine pure and pharmaceutical dosage forms of acemetacin. The methods proved valid according to the international conference on harmonization (ICH) guidelines. In addition to this, this work has been estimated under green criteria assessment tools. There is no significant difference between the proposed and the comparison methods after the statistical interpretation.

Eutectic Gallium-Indium Nanoparticles for Photodynamic Therapy of Pancreatic Cancer

Developing a cancer theranostic nanoplatform with diagnosis and treatment capabilities to effectively treat tumors and reduce side effects is of great significance. Herein, we present a drug delivery strategy for photosensitizers based on a new liquid metal nanoplatform that leverages the tumor microenvironment to achieve photodynamic therapeutic effects in pancreatic cancer. Eutectic gallium indium (EGaIn) nanoparticles were successfully conjugated with a water-soluble cancer targeting ligand, hyaluronic acid, and a photosensitizer, benzoporphyrin derivative, creating EGaIn nanoparticles (EGaPs) via a simple green sonication method. The prepared sphere-shaped EGaPs, with a core-shell structure, presented high biocompatibility and stability. EGaPs had greater cellular uptake, manifested targeting competence, and generated significantly higher intracellular ROS. Further, near-infrared light activation of EGaPs demonstrated their potential to effectively eliminate cancer cells due to their single oxygen generation capability. Finally, from in vivo studies, EGaPs caused tumor regression and resulted in 2.3-fold higher necrosis than the control, therefore making a good vehicle for photodynamic therapy. The overall results highlight that EGaPs provide a new way to assemble liquid metal nanomaterials with different ligands for enhanced cancer therapy.

Gradual compaction of the nascent peptide during cotranslational folding on the ribosome

Nascent polypeptides begin to fold in the constrained space of the ribosomal peptide exit tunnel. Here we use force-profile analysis (FPA) and photo-induced energy-transfer fluorescence correlation spectroscopy (PET-FCS) to show how a small α-helical domain, the N-terminal domain of HemK, folds cotranslationally. Compaction starts vectorially as soon as the first α-helical segments are synthesized. As nascent chain grows, emerging helical segments dock onto each other and continue to rearrange at the vicinity of the ribosome. Inside or in the proximity of the ribosome, the nascent peptide undergoes structural fluctuations on the µs time scale. The fluctuations slow down as the domain moves away from the ribosome. Mutations that destabilize the packing of the domain's hydrophobic core have little effect on folding within the exit tunnel, but abolish the final domain stabilization. The results show the power of FPA and PET-FCS in solving the trajectory of cotranslational protein folding and in characterizing the dynamic properties of folding intermediates.