Femtosecond laser synthesis and comparative analysis of fluorescent carbon dots from L-lysine aqueous solution

Laser synthesis of fluorescent species from biomolecules in living cells and tissues offers unique capabilities for fluorescent bioimaging, yet little is known about its mechanisms and characteristics of products. We examine synthesis of fluorescent products from water solution of L-lysine upon irradiation by trains of femtosecond laser pulses with varying parameters. We demonstrate that irradiation products contain nanoscale carbon-based fluorescent particles (carbon dots) with multi-colour and excitation-dependent emission. Morphology, chemical composition and fluorescent characteristics of irradiation products strongly depend on laser pulses parameters.

In Silico Investigation of Luminol, Its Analogues and Mechanism of Chemiluminescence for Blood Identification Beyond Forensics

Objective: This study aimed at discovering chemiluminescent analogues of luminol, predict their molecular binding to hemoglobin of bloodstains in household crime, and expound the mechanism of chemiluminescence of luminol. Materials and Methods: Similarity and clustering analyses of luminol analogues were conducted, and molecular docking was carried out using hemoglobin from Homo sapiens and four domestic organisms namely Gallus gallus, Drosophila melanogaster, Rattus norvegicus, and Canis familiaris. Results: The results showed the order of overall binding score as D. melanogaster > H. sapiens > C. familiaris > R. norvegicus > G. gallus. Seven compounds namely ZINC16958228, ZINC17023010, ZINC19915427, ZINC34928954, ZINC19915369, ZINC19915444, and ZINC82294978, were found to be consistently stable in binding with diverse hemoglobin and possibly have chemiluminescence than luminol in this in silico study. The interaction of human hemoglobin with luminol and its analogues, showed that amino acid residues His45, Lys61, Asn68, Val73, Met76, Pro77, Ala79, Ala82, Leu83, Pro95, Phe98, Lys99, Ser102, Ser133, Ala134, and Thr134, were possibly significant in the mechanism of action of presumptive test compounds. It was hypothesized that the improved mechanism of chemiluminescent for the identification of blood was based on peroxidase-like reaction, that produces nitric oxide which binds to hemoglobin (Hb) and inhibits Hb degradation without yielding fluorescent products. The compound 2,3-benzodioxine-1,4,5(6H)-trione was formed, which possibly emits light. Conclusion: This study provides novel insight on the luminol and its expanded mechanism for broader possible applications with careful development of new methodologies.

The Luminescence of 1,8-Diazafluoren-9-One/Titanium Dioxide Composite Thin Films for Optical Application

The investigation of innovative label-free α-amino acids detection methods represents a crucial step for the early diagnosis of several diseases. While 1,8-diazafluoren-9-one (DFO) is known in forensic application because of the fluorescent products by reacting with the amino acids present in the papillary exudate, its application for diagnostic purposes has not been fully investigated. The stabilization of DFO over a transparent substrate allows its complexation with biomolecules for the detection of α-amino acids. In this study, DFO was immobilized into a titanium dioxide (TiO2) matrix for the fluorescence detection of glycine, as a target α-amino acid (a potential marker of the urogenital tract cancers). The DFO/TiO2 composite was characterized by atomic force microscopy, spectroscopic ellipsometry, fluorescence spectroscopy and fluorescence microscopy. The performed fluorescent studies indicate spectacular formation of aggregates at higher concentration. The measurements performed using various fluorescence and microscopic techniques together with the suitable analysis show that the aggregates are able to emit short-lived fluorescence.

In-Silico Investigation of Luminol, Its Analogues and Improved Mechanism of Chemiluminescence for Blood Identification Beyond Forensics

ABSTRACTThis study aimed to discover chemiluminescent analogues of luminol, understand their molecular binding to hemoglobin of bloodstains in the household crime, and the mechanism of chemiluminescence. Similarity and clustering analyses of luminol analogues were conducted, and molecular docking was carried out on hemoglobin from Homo sapiens and other four domestic organism namely Gallus gallus, Drosophila melanogaster, Rattus norvegicus, and Canis familiaris. The results show that the order of overall binding score is D. melanogaster > H. sapiens > C. familiaris > R. norvegicus > G. gallus. Seven compounds namely ZINC16958228, ZINC17023010, ZINC19915427, ZINC34928954, ZINC19915369, ZINC19915444, and ZINC82294978, were found to be consistently stable in binding to diverse hemoglobin and possibly have chemiluminescence than luminol. The amino acid residues involved in the interaction of human hemoglobin with the 30 test compounds, show that His45, Lys61, Asn68, Val73, Met76, Pro77, Ala79, Ala82, Leu83, Pro95, Phe98, Lys99, Ser102, Ser133, Ala134, and Thr134 are significant in the mechanism of action of presumptive test compounds. The improved mechanism of chemiluminescent identification of blood hypothesized that nitrite interact with the Fe(II) heme, with the cleavage of a hydroxide ion and the formation of the nitrosonium cation in peroxidase reaction. It was proposed that degradation of rhombic heme complex to fluorescent products is possibly inhibited by nitric oxide from the test compound luminol. This study provides novel insight on the luminol and its actual mechanism for broader possible applications of luminol with careful development of new methodologies.

Novel methods for the rapid detection of trace tetracyclines based on the fluorescence behaviours of Maillard reaction fluorescent nanoparticles

The Maillard reaction and its fluorescent products have attracted widespread attention in the field of food safety and biology.

Photolysis of dimethoxynitrobenzyl-“caged” acids yields fluorescent products

Carboxylic acids conjugated with 4,5-dimethoxy-2-nitrobenzyl photoremovable protecting group are well known and widely used for biological studies. In this paper, we study the photolysis of likewise “caged” acetic, caprylic and arachidonic acids. Unexpectedly, we observed huge growth of fluorescence emission at ~430 nm during photolysis. Following further UV irradiation, a product with fluorescence at longer wavelength was formed (470 nm excitation / ~500–600 nm emission). While it may be used to monitor the “uncaging”, these fluorescent products may interfere with widespread dyes such as fluorescein in biomedical experiments. This effect might be negligible if the photolysis products dissolve in the medium. On the other hand, we observed that arachidonic and caprylic acids derivatives self-organize in emulsion droplets in water environment due to long lipophilic chains. Illumination of droplets by UV rapidly induces orange fluorescence excited by 488 nm light. This fluorescence turn-on was fast (~0.1 s) and apparently caused by the accumulation of water-insoluble fluorescent residuals inside droplets. These self-organized lipophilic structures with fluorescence turn-on capability may be of interest for biomedical and other application. We have identified and hypothesized some compounds which may be responsible for the observed fluorescense.

Highly active fluorogenic oxidase-mimicking NiO nanozymes

NiO nanoparticles can quickly catalyze oxidation of Amplex red to produce fluorescent products for intracellular imaging, much more efficiently than other types of tested nanozymes.

Photo-induced C–H bond activation of N,N′-dialkylethylenediamine upon aza-Michael addition to 1,8-pyrenedione: facile synthesis of fluorescent pyrene derivatives

We discovered a reaction between 1,8-pyrenedione and N,N′-dialkylethylenediamine to form highly fluorescent products, via aza-Michael addition followed by double C–H activation facilitated by visible light.

Bio-friendly Maillard reaction fluorescent products from glutathione and ascorbic acid for the rapid and label-free detection of Fe3+in living cells

Non-cytotoxic Maillard reaction fluorescent products were used as an imaging probe for Fe3+detection in living cells.