N-Doped Carbon Quantum Dots as Fluorescent Bioimaging Agents

A Comprehensive Review of Nanoparticles: From Classification to Application and Toxicity

Nanoparticles are structures that possess unique properties with high surface area-to-volume ratio. Their small size, up to 100 nm, and potential for surface modifications have enabled their use in a wide range of applications. Various factors influence the properties and applications of NPs, including the synthesis method and physical attributes such as size and shape. Additionally, the materials used in the synthesis of NPs are primary determinants of their application. Based on the chosen material, NPs are generally classified into three categories: organic, inorganic, and carbon-based. These categories include a variety of materials, such as proteins, polymers, metal ions, lipids and derivatives, magnetic minerals, and so on. Each material possesses unique attributes that influence the activity and application of the NPs. Consequently, certain NPs are typically used in particular areas because they possess higher efficiency along with tenable toxicity. Therefore, the classification and the base material in the NP synthesis hold significant importance in both NP research and application. In this paper, we discuss these classifications, exemplify most of the major materials, and categorize them according to their preferred area of application. This review provides an overall review of the materials, including their application, and toxicity.

Development of biomass waste-based carbon quantum dots and their potential application as non-toxic bioimaging agents

Over recent years, carbon quantum dots (CQDs) have advanced significantly and gained substantial attention for their numerous benefits. These benefits include their simple preparation, cost-effectiveness, small size, biocompatibility, bright luminescence, and low cytotoxicity. As a result, they hold great potential for various fields, including bioimaging. A fascinating aspect of synthesizing CQDs is that it can be accomplished by using biomass waste as the precursor. Furthermore, the synthesis approach allows for control over the physicochemical characteristics. This paper unequivocally examines the production of CQDs from biomass waste and their indispensable application in bioimaging. The synthesis process involves a simple one-pot hydrothermal method that utilizes biomass waste as a carbon source, eliminating the need for expensive and toxic reagents. The resulting CQDs exhibit tunable fluorescence and excellent biocompatibility, making them suitable for bioimaging applications. The successful application of biomass-derived CQDs has been demonstrated through biological evaluation studies in various cell lines, including HeLa, Cardiomyocyte, and iPS, as well as in medaka fish eggs and larvae. Using biomass waste as a precursor for CQDs synthesis provides an environmentally friendly and sustainable alternative to traditional methods. The resulting CQDs have potential applications in various fields, including bioimaging.

Carbon dots: Types, preparation, and their boosted antibacterial activity by photoactivation. Current status and future perspectives

Carbon dots (CDs) correspond to carbon-based materials (CBM) with sizes usually below 10 nm. These nanomaterials exhibit attractive properties such us low toxicity, good stability, and high conductivity, which have promoted their thorough study over the past two decades. The current review describes four types of CDs: carbon quantum dots (CQDs), graphene quantum dots (GQDs), carbon nanodots (CNDs), and carbonized polymers dots (CPDs), together with the state of the art of the main routes for their preparation, either by "top-down" or "bottom-up" approaches. Moreover, among the various usages of CDs within biomedicine, we have focused on their application as a novel class of broad-spectrum antibacterial agents, concretely, owing their photoactivation capability that triggers an enhanced antibacterial property. Our work presents the recent advances in this field addressing CDs, their composites and hybrids, applied as photosensitizers (PS), and photothermal agents (PA) within antibacterial strategies such as photodynamic therapy (PDT), photothermal therapy (PTT), and synchronic PDT/PTT. Furthermore, we discuss the prospects for the possible future development of large-scale preparation of CDs, and the potential for these nanomaterials to be employed in applications to combat other pathogens harmful to human health. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Light-Activated Modified Arginine Carbon Dots as Antibacterial Particles

Nitrogen-doped arginine carbon dots (Arg CDs) as light-sensitive antibacterial agents were prepared by using citric acid as the carbon source and arginine amino acid as the nitrogen source via a microwave-assisted synthesis method. Dynamic light scattering (DLS) measurements and TEM images revealed that the Arg CDs were in the 1–10 nm size range with a graphitic structure. To improve their antibacterial capability, the Arg CDs were modified with ethyleneimine (EDA), pentaethylenehexamine (PEHA), and polyethyleneimine (PEI) as different amine sources, and the zeta potential value of +2.8 ± 0.6 mV for Arg CDs was increased to +34.4 ± 4.1 mV for PEI-modified Arg CDs. The fluorescence intensity of the Arg CDs was significantly enhanced after the modification with EDA, and the highest antibacterial effect was observed for the PEI-modified Arg CDs. Furthermore, the photodynamic antibacterial capacity of bare and EDA-modified Arg CDs was determined upon light exposure to show their light-induced antibacterial effects. Photoexcited (315–400 nm, UVA, 300 W), EDA-modified Arg CDs at 5 mg/mL concentration were found to inhibit about 49 ± 7% of pathogenic bacteria, e.g., Escherichia coli, with 5 min of light exposure. Furthermore, the biocompatibilities of the bare and modified Arg CDs were also investigated with blood compatibility tests via hemolysis and blood clotting assays and cytotoxicity analysis on L929 fibroblast cells.

Transforming waste into value: pomelo-peel-based nitrogen-doped carbon dots for the highly selective detection of tetracycline

Tetracycline (TC) is widely used as a veterinary drug, and its residue in livestock products could enter the human body and cause damage. In this study, we developed an eco-friendly approach that utilized pomelo peel as a carbon source to synthesize new water-soluble N-doped carbon dots (P-NCDs) with blue fluorescence, obtaining a high quantum yield of up to 76.47% and achieving the goal of turning waste into value. Our prepared P-NCDs can selectively recognized TC, and their fluorescence was quenched based on the IFE. P-NCDs could measure the TC concentration in the linear range of 0-100 μmol L-1 with a detection limit (LOD, S/N = 3) as low as 0.045 μmol L-1. Furthermore, we have successfully applied our P-NCDs to the detection of TC in milk samples with convincing results within 90 s. Overall, our newly synthesized fluorescent sensor, P-NCDs, demonstrated huge potential to become an alternative way to detect TC in a simple, efficient, sensitive way without using any special instruments.

Multiple fluorescence response behaviours to proteins/bacteria and selective antibacterial activity of cetylpyridinium chloride (CPC)-based cationic carbon dots

Direct interaction between carbon dots (CDs) and biomolecules leads to changes in the chemical and physical status as well as properties of CDs, which can have various biological and biomedical applications. In this work, the surface of CDs was modified with cetylpyridinium chloride (CPC) to facilitate interactions between CDs and biomolecules. Multiple fluorescence response behaviours of CPC-based CDs were observed towards several proteins (bovine serum albumin, lysozyme, protamine, and hemoglobin) and bacterial cells (Escherichia coli and Staphylococcus aureus). Electrostatic attraction and hydrogen bonding were involved in inducing aggregation of CDs and fluorence enhancement. An inner filter effect might also occur to reduce fluorescence of CDs when interacting with proteins. Selective antibacterial activity of CPC-based CDs was observed towards Gram positive bacterium Staphylococcus aureus. This work provides potential to develop CD-based techniques for detecting and visualizing proteins/bacteria as well as selective antibacterial agents towards Gram-positive bacteria.

Aggregation of cetylpyridinium chloride-based cationic carbon dots (CPC-based CDs) inducing by proteins or bacteria could led to multiple fluorescence response behaviours. The CPC-based CDs also showed selective antibacterial activity.