New Insight into the Fluorescence Quenching of Nitrogen-Containing Carbonaceous Quantum Dots-From Surface Chemistry to Biomedical Applications.

Marek Wiśniewski,Michał Świdziński,Joanna Czarnecka,Paulina Bolibok,Katarzyna Roszek

doi:10.3390/ma14092454

Marek Wiśniewski, Michał Świdziński + Show 3 more

Open Access

https://doi.org/10.3390/ma14092454

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Journal: Materials	Publication Date: May 9, 2021
Citations: 14	License type: CC BY 4.0

Affiliation: Nicolaus Copernicus University

Abstract

Carbon-based quantum dots are widely suggested as fluorescent carriers of drugs, genes or other bioactive molecules. In this work, we thoroughly examine the easy-to-obtain, biocompatible, nitrogen-containing carbonaceous quantum dots (N-CQDs) with stable fluorescent properties that are resistant to wide-range pH changes. Moreover, we explain the mechanism of fluorescence quenching at extreme pH conditions. Our in vitro results indicate that N-CQDs penetrate the cell membrane; however, fluorescence intensity measured inside the cells was lower than expected from carbonaceous dots extracellular concentration decrease. We studied the mechanism of quenching and identified reduced form of β-nicotinamide adenine dinucleotide (NADH) as one of the intracellular quenchers. We proved it experimentally that the elucidated redox process triggers the efficient reduction of amide functionalities to non-fluorescent amines on carbonaceous dots surface. We determined the 5 nm–wide reactive redox zone around the N-CQD surface. The better understanding of fluorescence quenching will help to accurately quantify and dose the internalized carbonaceous quantum dots for biomedical applications.

Highlights

The development of novel functional nanosystems, connecting effective bio-imaging with therapeutic agent delivery, has recently become the most promising direction in nanomedicine and is rapidly expanding
Based on the fluorescence measured in cell lysates and culture medium, we indicated that a decrease in the nitrogen-containing carbonaceous quantum dots (N-carbon quantum dots (CQDs)) fluorescence in the extracellular environment better reflects the quantity of material endocytosed
The facile facile and environmentally friendly procedure resulted in the nitrogen-containing carboand environmentally friendly procedure resulted in the nitrogen-containing carbonaceous naceous quantum dots (N-CQDs) containing 18.4% nitrogen (Figure 2a), and possessing quantum dots (N-CQDs) containing 18.4% nitrogen (Figure 2a), and possessing almost almost uniform size nm, as presented in2b,c

Summary

Introduction

The development of novel functional nanosystems, connecting effective bio-imaging with therapeutic agent delivery (theranostic approach), has recently become the most promising direction in nanomedicine and is rapidly expanding. Well-established QDs contain toxic elements, such as Cd, Pb, Hg, Se, and Te. Well-established QDs contain toxic elements, such as Cd, Pb, Hg, Se, and Te They meet most of the expectations for drug-delivery nanosystems; the excitation-dependent emission of quantum dots allows to follow their distribution within the cells or even in the whole body. They are preferably tested in vitro in different cancer cell cultures [6,8,9]. The main drawbacks of these inorganic materials, are their high toxicity and non-biodegradability

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