Fluorescent Carbon Dots for Sensitive and Rapid Monitoring of Intracellular Ferrous Ion

Although iron is an essential constituent for almost all living organisms, iron dyshomeostasis at a cellular level may trigger oxidative stress and neuronal damage. Hence, there are numerous reported carbon dots (CDs) that have been synthesized and applied to determine intracellular iron ions. However, among reported CDs focused to detect Fe3+ ions, only a few CDs have been designed to specifically determine Fe2+ ions over Fe3+ ions for monitoring of intracellular Fe2+ ions. We have developed the nitrogen-doped CDs (NCDs) for fluorescence turn-off detection of Fe2+ at cellular level. The as-synthesized NCDs exhibit a strong blue fluorescence and low cytotoxicity, acting as fluorescence probes to detect Fe2+ as low as 0.702 µM in aqueous solution within 2 min and visualize intracellular Fe2+ in the concentration range from 0 to 500 µM within 20 min. The as-prepared NCDs possess some advantages such as high biocompatibility, strong fluorescence properties, selectivity, and rapidity for intracellular Fe2+ monitoring, making NCDs an excellent nanoprobe for biosensing of intracellular ferrous ions.

Influence of Atmospheric Cold Plasma Exposure on Naturally Present Fungal Spores and Physicochemical Characteristics of Sundried Tomatoes (Solanum lycopersicum L.)

This research aimed to evaluate the impact of atmospheric cold plasma (ACP) treatment on the fungal spores naturally present in sundried tomatoes, as well as their influence on the physico-chemical properties and antioxidant activity. ACP was performed with a Surface Dielectric Barrier Discharge (SDBD), applying 6 kV at 23 kHz and exposure times up to 30 min. The results showed a significant reduction of mesophilic aerobic bacteria population and of filamentous fungi after the longer ACP exposure. In particular, the effect of the treatment was assessed on Aspergillus rugulovalvus (as sensible strain) and Aspergillus niger (as resistant strain). The germination of the spores was observed to be reliant on the species, with nearly 88% and 32% of non-germinated spores for A. rugulovalvus and A. niger, respectively. Fluorescence probes revealed that ACP affects spore viability promoting strong damage to the wall and cellular membrane. For the first time, the sporicidal effect of ACP against A. rugulovalvus is reported. Physicochemical parameters of sundried tomatoes such as pH and water activity (aw) were not affected by the ACP treatment; on the contrary, the antioxidant activity was not affected while the lycopene content was significantly increased with the increase in ACP exposure time (p ≤ 0.05) probably due to increased extractability.

Pyrene-based monomer-excimer dual response organosilicon polymer for selective detection of 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP)

The formation or destruction of pyrene excimer with strong emission change make it a versatile fluorophore to construct excimer emission-based fluorescence probes for various analytes detection. The distinct difference between...

Reaction-based fluorescence probes for “turn on” sensing fluoride ions

Introducing a weak covalent bond into an originally highly fluorescent molecule to create a non-fluorescent probe is able to afford a new way to detect some neucleophilic targets with enhanced...

Terpenoid Hydrazones as Biomembrane Penetration Enhancers: FT-IR Spectroscopy and Fluorescence Probe Studies

Hydrazones based on mono- and bicyclic terpenoids (verbenone, menthone and carvone) have been investigated in vitro as potential biomembrane penetration enhancers. In this regard, liposomes composed of lecithin or cardiolipin as phospholipid phase components with incorporated fluorescence probes have been prepared using the thin-film ultrasonic dispersion method. The mean particle size of the obtained liposomes, established using laser diffraction, was found to be 583 ± 0.95 nm, allowing us to categorize them as multilamellar vesicles (MLVs) according to their morphology. Pursuant to fluorescence analysis, we may assume a reduction in microviscosity and, consequently, a decrease in the packing density of lecithin and cardiolipin lipids to be the major mechanism of action for terpenoid hydrazones 1–15. In order to determine the molecular organization of the lipid matrix, lipids were isolated from rat strata cornea (SCs) and their interaction with tested compounds was studied by means of Fourier transform infrared spectroscopy. FT-IR examination suggested that these hydrazones fluidized the SC lipids via the disruption of the hydrogen-bonded network formed by polar groups of SC constituents. The relationship between the structure of terpenoid hydrazones and their ability to enhance biomembrane penetration is discussed.

Advanced NIR ratiometric probes for intravital biomedical imaging

Near-infrared fluorescence imaging technology (NIR-I region, 650–950 nm and NIR-II region, 1000–1700 nm), with deeper tissue penetration and less disturbance from auto-fluorescence than that in visible region (400−650 nm), is playing a more and more extensive role in the field of biomedical imaging. With the development of precise medicine, intelligent NIR fluorescent probes have been meticulously designed to provide more sensitive, specific and accurate feedback on detection. Especially, recently developed ratiometric fluorescence probes have been devoted to quantify physiological and pathological parameters with a combination of responsive fluorescence changes and self-calibration. Herein, we systemically introduced the construction strategies of NIR ratiometric fluorescence probes and their applications in biological imaging in vivo, such as molecular detection, pH and temperature measurement, drug delivery monitoring and treatment evaluation. We further summarized possible optimization on the design of ratiometric probes for quantitative analysis with NIR fluorescence, and prospected the broader optical applications of ratiometric probes in life science and clinical translation.

Mitochondria Endoplasmic Reticulum Contact Sites (MERCs): Proximity Ligation Assay as a Tool to Study Organelle Interaction

Organelles cooperate with each other to regulate vital cellular homoeostatic functions. This occurs through the formation of close connections through membrane contact sites. Mitochondria-Endoplasmic-Reticulum (ER) contact sites (MERCS) are one of such contact sites that regulate numerous biological processes by controlling calcium and metabolic homeostasis. However, the extent to which contact sites shape cellular biology and the underlying mechanisms remain to be fully elucidated. A number of biochemical and imaging approaches have been established to address these questions, resulting in the identification of a number of molecular tethers between mitochondria and the ER. Among these techniques, fluorescence-based imaging is widely used, including analysing signal overlap between two organelles and more selective techniques such as in-situ proximity ligation assay (PLA). While these two techniques allow the detection of endogenous proteins, preventing some problems associated with techniques relying on overexpression (FRET, split fluorescence probes), they come with their own issues. In addition, proper image analysis is required to minimise potential artefacts associated with these methods. In this review, we discuss the protocols and outline the limitations of fluorescence-based approaches used to assess MERCs using endogenous proteins.

Carbon “quantum” dots for bioapplications

Carbon “quantum” dots or carbon dots (CDots) exploit and enhance the intrinsic photoexcited state properties and processes of small carbon nanoparticles via effective nanoparticle surface passivation by chemical functionalization with organic species. The optical properties and photoinduced redox characteristics of CDots are competitive to those of established conventional semiconductor quantum dots and also fullerenes and other carbon nanomaterials. Highlighted here are major advances in the exploration of CDots for their serving as high-performance yet nontoxic fluorescence probes for one- and multi-photon bioimaging in vitro and in vivo, and for their uniquely potent antimicrobial function to inactivate effectively and efficiently some of the toughest bacterial pathogens and viruses under visible/natural or ambient light conditions. Opportunities and challenges in the further development of the CDots platform and related technologies are discussed.