Nanoclusters of self-assembled quantum dots driven by fluorine-fluorine interactions as delivery platform for enzymes

Introduction Self-assembled NPs are considered as one of the most promising nanosystems to deliver drugs and biological molecules such as enzymes for therapeutic applications. Non-covalent hydrophobic interactions play an... [ view full abstract ]

Introduction

Self-assembled NPs are considered as one of the most promising nanosystems to deliver drugs and biological molecules such as enzymes for therapeutic applications. Non-covalent hydrophobic interactions play an important role in the formation of assemblies, and fluorine-fluorine interactions are particularly interesting because the unique hydrophobicity and lipophilicity of fluorine lead to stronger interactions. Herein, inspired by the role of fluorine in self-assembly and its favorable interaction with proteins, we report a novel delivery platform for enzymes based on self-assembled nanoclusters of fluorinated quantum dots (QD_F).

Methods

QD_F were prepared by ligand-exchange of TOPO-capped QDs with a fluorinated ligand. The self-assembly process consisted simply in mixing the QD_F dispersed in DMSO with water and stirring vigorously for 1 min. The encapsulation of the enzyme within the clusters involved two steps: i) enzyme incubation with QD_F, and ii) formation of clusters (Fig. 1). TEM, ¹H and ¹⁹F NMR, DLS, LDA, enzymatic activity assays, and BCA assay were used as characterization and analytical techniques.

Results

The obtained nanoclusters with a size of ca. 44 nm and charge of ‒35 mV presented very good colloidal stability in the presence of diverse ions up to 500 µM, in a wide range of pH (from 5 to 9) and over the time. These clusters were able to encapsulate different enzymes (laccase and α-galactosidase) obtaining high loading efficiencies. Importantly, the encapsulated enzymes maintained their catalytic activity following a Michaelis-Menten kinetic, and presented higher K_M and lower V_max than their free forms, which was due to the modification of their microenvironment Under acidic environment (as in endosomes/lysosomes), clusters were slowly disassembled allowing the release of enzymes. 50% of encapsulated enzyme was released within 24 h (Fig. 2). Importantly, enzymes retained their activity after release.

Discussion

This is the first time that self-assembled fluorinated NPs are proposed as nanocarriers for drug delivery. The main achievements of this work are: (i) Proof of the potential of non-covalent fluorine-fluorine interactions as driving force for the self-assembly of NPs, and (ii) Demonstration of the ability of this system to carry and deliver enzymes in a controlled fashion.