Harnessing Efficient ROS Generation in Carbon Dots Derived from Methyl Red for Antimicrobial Photodynamic Therapy.

The emergence of drug-resistant pathogenic microorganisms has become a public health concern, with demand for strategies to suppress their proliferation in healthcare facilities. The present study investigates the physicochemical and antimicrobial properties of carbon dots (CD-MR) derived from the methyl red azo dye. The morphological and structural analyses reveal that such carbon dots present a significant fraction of graphitic nitrogen in their structures, providing a wide emission range. Based on their low cytotoxicity against mammalian cells and tunable photoluminescence, these carbon dots are applied to bioimaging in vitro living cells. The possibility of using CD-MR to generate reactive oxygen species (ROS) is also analyzed, and a high singlet oxygen quantum efficiency is verified. Moreover, the antimicrobial activity of CD-MR is analyzed against pathogenic microorganisms Staphylococcus aureus, Candida albicans, and Cryptococcus neoformans. Kirby-Bauer susceptibility tests show that carbon dots synthesized from methyl red possess antimicrobial activity upon photoexcitation at 532 nm. The growth inhibition of C. neoformans from CD-MR photosensitization is investigated. Our results show that N-doped carbon dots synthesized from methyl red efficiently generate ROS and possess a strong antimicrobial activity against healthcare-relevant pathogens.

Bevacizumab-Conjugated Quantum Dots: In Vitro Antiangiogenic Potential and Biosafety in Rat Retina.

Purpose: Disturbances that affect the inside of the eyeball tend to be highly harmful since they compromise the homeostasis of this organ. Alongside this, the eyeball has several anatomical barriers that prevent the entry of substances. This way, diseases that affect the retina are among those that present greater difficulty in the treatment. In many cases, abnormal proliferation of blood vessels (neovascularization) occurs from the lower layers of the retina. This process damages its structure physiologically and anatomically, causing the rapid and irreversible loss of visual capacity. This work aims to develop nanosuspensions of quantum dots (QDs) conjugated to bevacizumab. Methods: Two types of QDs were produced by aqueous route, stabilized with chitosan conjugated to bevacizumab. The antiangiogenic activity was evaluated in the chorioallantoic membrane model, in which results indicated discrete activity at the doses tested. Samples were assessed for their biosafety in animals, after intravitreal administration, by means of electroretinography (ERG), intraocular pressure (IOP) measurement, histological, morphometric, and immunohistochemical evaluation. Results: No significant alterations were detected in ERG that suggests damage to retinal function by the samples. No significant changes in IOP were also detected. The histological sections did not show signs of acute inflammation, although there was evidence of late retinal damage. The immunohistochemical analysis did not detect any apoptotic bodies. Conclusion: Preliminary results suggest that QDs present potential applicability in ocular therapy, and it is necessary to better characterize their in vivo behavior and to optimize their dosage.

Biomedical applications of glyconanoparticles based on quantum dots.

BACKGROUND: Quantum dots (QDs) are outstanding nanomaterials of great interest to life sciences. Their conjugation versatility added to unique optical properties, highlight these nanocrystals as very promising fluorescent probes. Among uncountable new nanosystems, in the last years, QDs conjugated to glycans or lectins have aroused a growing attention and their application as a tool to study biological and functional properties has increased. SCOPE OF REVIEW: This review describes the strategies, reported in the literature, to conjugate QDs to lectins or carbohydrates, providing valuable information for the elaboration, improvement, and application of these nanoconjugates. It also presents the main applications of these nanosystems in glycobiology, such as their potential to study microorganisms, the development of diseases such as cancer, as well as to develop biosensors. MAJOR CONCLUSIONS: The development of glyconanoparticles based on QDs emerged in the last decade. Many works reporting the conjugation of QDs with carbohydrates and lectins have been published, using different strategies and reagents. These bioconjugates enabled studies that are very sensitive and specific, with potential to detect and elucidate the glycocode expressed in various normal or pathologic conditions. GENERAL SIGNIFICANCE: Produce a quick reference source over the main advances reached in the glyconanotechnology using QDs as fluorescent probes.