Silica-Supported Assemblage of CuII Ions with Carbon Dots for Self-Boosting and Glutathione-Induced ROS Generation

Olga Bochkova,Syumbelya Amerhanova,Tatiana Gerasimova,Anna Lyubina,Alexey Dovjenko,Artem Laskin,Svetlana Fedorenko,Rinata Biktimirova,Asiya Mustafina,Irek Nizameev,Rustem Zairov,Amina Daminova,Alexandra Voloshina,Kirill Kholin,Vladimir Evtugyn

doi:10.3390/coatings12010097

Abstract

The present work introduces coordinative binding of CuII ions with both amino-functionalized silica nanoparticles (SNs) and green-emitting carbon dots (CDs) as the pregrequisite for the CuII-assisted self-assembly of the CDs at the surface of the SNs. The produced composite SNs exhibit stable in time stimuli-responsive green fluorescence derived from the CuII-assisted assemblage of CDs. The fluorescence response of the composite SNs is sensitive to the complex formation with glutathione (GSH), enabling them to detect it with the lower limit of detection of 0.15 μM. The spin-trap-facilitated electron spin resonance technique indicated that the composite SNs are capable of self-boosting generation of ROS due to CuII→CuI reduction by carbon in low oxidation states as a part of the CDs. The intensity of the ESR signals is enhanced under the heating to 38 °C. The intensity is suppressed at the GSH concentration of 0.35 mM but is enhanced at 1.0 mM of glutathione, while it is suppressed once more at the highest intracellular concentration level of GSH (10 mM). These tendencies reveal the concentrations optimal for the scavenger or reductive potential of GSH. Flow cytometry and fluorescence and confocal microscopy methods revealed efficient cell internalization of SNs-NH2-CuII-CDs comparable with that of “free” CDs.

Highlights

Silica nanoparticles (SNs) are convenient nanobeads for both molecular and nanosized dopants, which can be either included in the silica matrix or deposited onto the silica surface through the cooperative effect of multiple noncovalent interactions [1,2,3,4]
The present work represents an assemblage of green-emissive carbon dots (CDs) facilitated by coordination bond as a mode of noncovalent surface decoration of silica nanoparticles (SNs) aimed at developing a composite nanomaterial for sensing, imaging and reactive oxygen species (ROS) generation
The claimed aim requires specific metal ions and functional groups at the surface of SNs, which are able to (1) form efficient coordination bonds to provide the assemblage of CDs at the surface of SNs, (2) be labile to give a quick response on biorelevant substrates and (3) be redox-active to generate ROS in cell cytoplasm

Summary

Introduction

Silica nanoparticles (SNs) are convenient nanobeads for both molecular and nanosized dopants, which can be either included in the silica matrix or deposited onto the silica surface through the cooperative effect of multiple noncovalent interactions [1,2,3,4]. It is worth noting that a surface modification of SNs is of greater impact on their cellular uptake and sensing than the inclusive modification of SNs. the present work represents noncovalent surface decoration of SNs by green-emissive carbon dots (CDs) facilitated by coordination bonds as a route for developing a composite nanomaterial combining functional properties derived from both metal ions and CDs. Emissive carbon dots (CDs) have gained much attention as the basis for sensing [5,6]. The present work represents an assemblage of green-emissive carbon dots (CDs) facilitated by coordination bond as a mode of noncovalent surface decoration of SNs aimed at developing a composite nanomaterial for sensing, imaging and reactive oxygen species (ROS) generation. The claimed aim requires specific metal ions and functional groups at the surface of SNs, which are able to (1) form efficient coordination bonds to provide the assemblage of CDs at the surface of SNs, (2) be labile to give a quick response on biorelevant substrates and (3) be redox-active to generate ROS in cell cytoplasm

Methods

Results

Conclusion