Background: Air pollution is killing close to 5 million people a year, and harming billions more. Air pollution levels remain extremely high in many parts of the world, and air pollution-associated premature deaths have been reported for urbanized areas, particularly linked to the presence of airborne nano-sized and ultrafine particles. Main text: To date, most of the research studies did focus on the adverse effects of air pollution on the human cardiovascular and respiratory systems. Although the skin is in direct contact with air pollutants, their damaging effects on the skin are still under investigation. Epidemiological data suggested a correlation between exposure to air pollutants and aggravation of symptoms of chronic immunological skin diseases. In this study, a systematic literature review was conducted to understand the current knowledge on the effects of airborne particulate matter on human skin. It aims at providing a deeper understanding of the interactions between air pollutants and skin to further assess their potential risks for human health. Conclusion: Particulate matter was shown to induce a skin barrier dysfunction and provoke the formation of reactive oxygen species through direct and indirect mechanisms, leading to oxidative stress and induced activation of the inflammatory cascade in human skin. Moreover, a positive correlation was reported between extrinsic aging and atopic eczema relative risk with increasing particulate matter exposure.
Synthesizing highly efficient red-emissive carbon dots (CDs) is a challenge that still impedes widespread applications of CDs in bioimaging. Herein, we demonstrate a facile, isolation-free synthesis of deep red (600−700 nm) emissive nitrogen-doped CDs (nCDs) based on microwave-assisted pyrolysis of citric acid and ethylenediamine. The duration of pyrolysis, the molar ratio of acid to amine, and the concentration of reactants were optimized using Central Composite Design and Response Surface Methodology to yield deep red fluorescence. We demonstrated their applicability on three different cell lines (retinal epithelial, lens epithelial, and Chinese hamster ovary cells). We measured the viability, the generation of reactive oxygen species, and percentage of apoptotic cells to determine their level of toxicity in cell culture. Confocal images showed that the nCDs fluoresced at different wavelengths depending upon the excitation wavelength and were excitable up to 635 nm. Furthermore, the ex vivo imaging of porcine ocular globes and postmortem imaging of a whole mouse exemplified the utility of nCDs.
This
work demonstrates the application of hyaluronan-conjugated
nitrogen-doped carbon quantum dots (HA-nCQDs) for bioimaging of tumor
cells and illustrates their potential use as carriers in targeted
drug delivery. Quantum dots are challenging to deliver with specificity,
which hinders their application. To facilitate targeted internalization
by cancer cells, hyaluronic acid, a natural ligand of CD44 receptors,
was covalently grafted on nCQDs. The HA-nCQD conjugate was synthesized
by carbodiimide coupling of the amine moieties on nCQDs and the carboxylic
acids on HA chains. Conjugated HA-nCQD retained sufficient fluorescence,
although with 30% lower quantum efficiency than the original nCQDs.
Confocal microscopy showed enhanced internalization of HA-nCQDs, facilitated
by CD44 receptors. To demonstrate the specificity of HA-nCQDs toward
human tumor cells, patient-derived breast cancer tissue with high-CD44
expression was implanted in adult mice. The tumors were allowed to
grow up to 200–250 mm3 prior to the injection of
HA-nCQDs. With either local or systemic injection, we achieved a high
level of tumor specificity judged by a strong signal-to-noise ratio
between the tumor and the surrounding tissue in vivo. Overall, the results show that HA-nCQDs can be used for imaging
of CD44-specific tumors in preclinical models of human cancer and
potentially used as carriers for targeted drug delivery into CD44-rich
cells.
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