Quantum Dots Meet Enzymes: Hydrophobicity of Surface Ligands and Size Do Matter

Abstract

Colloidal quantum dots (QDs) are a class of representative fluorescent nanomaterials with tunable, bright, and sharp fluorescent emission, with promising biomedical applications. However, their effects on biological systems are not fully elucidated. In this work, we investigated the interactions between QDs with different surface ligands and different particle sizes and α-chymotrypsin (ChT) from the thermodynamic and kinetic perspectives. Enzymatic activity experiments demonstrated that the catalytic activity of ChT was strongly inhibited by QDs coated with dihydrolipoic acid (DHLA-QDs) with noncompetitive inhibitions, whereas the QDs coated with glutathione (GSH-QDs) had weak effects. Furthermore, kinetics studies showed that different particle sizes of DHLA-QDs all had high suppressive effects on the catalytic activity of ChT. It was found that DHLA-QDs with larger particle sizes had stronger inhibition effects because more ChT molecules were bound onto the surface of QDs. This work highlights the importance of hydrophobic ligands and particle sizes of QDs, which should be considered as the primary influencing factors in the assessment of biosafety. Meanwhile, the results herein can also inspire the design of nano inhibitors.

New Insights on the Size-Dependent Inhibition of Enzymes by Gold Nanoparticles

“…This was mainly because that larger Amsil had larger S t and could bind more taspase1 . Our group also found the same rule using CdSe quantum dots and chymotrypsin (ChT) as the object of study . However, Zhu et al found that smaller TiO 2 nanoparticles had stronger E on pepsin under the same mass concentration .…”

“…9 Our group also found the same rule using CdSe quantum dots and chymotrypsin (ChT) as the object of study. 8 However, Zhu et al found that smaller TiO 2 nanoparticles had stronger E on pepsin under the same mass concentration. 17 This could also be explained by S t .…”

“…The main influencing factors of the binding between AuNPs and enzymes included the hydrophobicity of ligands, ,, surface charges, − as well as the size of AuNPs. ,, Among them, particle size was an important factor which might affect the binding parameters in several ways (Table ). Using coarse-grained simulations, Jahan Sajib et al.…”

“…Except for the uncompetitive inhibition of AChE by p MBA–AuNCs and DHLA–AuNCs, most of the inhibition of enzymes by AuNPs was through the binding-based competitive or noncompetitive mechanism. − Therefore, in the majority of cases, the inhibitory efficacy ( E ) could be simply expressed as the function of binding parameters. E = f ( N , K a , D ) = f ( S t , ρ , K a , D ) Here, N is the total number of binding sites on all AuNPs, which is equal to the total surface area of all AuNPs ( S t ) multiplied by the density of binding sites ( ρ ). K a represents the association constant.…”

“…The main influencing factors of the binding between AuNPs and enzymes included the hydrophobicity of ligands, 7,8,13 surface charges, 14−16 as well as the size of AuNPs. 8,9,17 Among them, particle size was an important factor which might affect the binding parameters in several ways (Table 1). Using coarse-grained simulations, Jahan Sajib et al found that AuNPs with larger curvatures had higher ρ of ovispirins because ovispirins preferred to stand on the surface of smaller AuNPs while they were more likely to lie down on the surface of larger AuNPs.…”