Enzyme-powered Janus nanomotor decorated with β-amino ester/dialdehyde starch: pH-controllable speed, and in vitro curcumin release

Abstract

Enzymatic nanomotors have garnered significant attention as promising candidates for biocompatible propulsion mechanisms and for studying kinetic parameters during enzymatic degradation. Environmental pH has a notable impact on nanomotor performance, particularly in applications that replicate the acidic conditions found in cancer cells. Additionally, understanding how these motors can regulate their speed in response to changing pH levels is crucial for assessing their operational stability. In this study, Fe₃O₄ nanoparticles were synthesized and asymmetrically functionalized with hydrophobic β-amino ester (BAE) and hydrophilic dialdehyde starch (DAS) to create Janus-type nanoparticles. Structural characterization was conducted using ¹H NMR and ¹³C NMR spectroscopy for BAE and XRD and DSC for DAS, while further analysis was conducted using TGA, selective staining to differentiate hydrophobic and hydrophilic regions, SEM, FTIR, DLS, and zeta potential measurements. The motor characteristics of these Janus nanoparticles were evaluated in the presence of the CALB enzyme under neutral and acidic conditions. Velocity and diffusion analyses revealed a significant decrease in propulsion efficiency at lower pH, attributed to enzyme deactivation. Notably, these nanomotors demonstrated the ability to adjust their speed in response to pH changes, and their performance was reversible; restoring neutral pH led to the recovery of motor velocity while maintaining structural stability. The investigation of pH-triggered curcumin release, along with these findings, indicates the promising potential of enzyme-powered Janus nanomotors for precise control in biologically relevant environments, particularly in targeted drug delivery applications.

Graphical abstract