Ladybird Particles: Asymmetric Polymer–Nanoparticle Composites Prepared via Dewetting-Induced Particle Redistribution

Abstract

We introduce composite microparticles, termed ladybird particles, formed by thermally induced dewetting of thin polycaprolactone (PCL) films under aqueous-phase conditions in the presence of selenium nanoparticles. The resulting structures consist of surface-supported spherical-cap polymer domains decorated with partially exposed selenium nanoparticles, giving rise to a characteristic ladybird-like morphology. During dewetting, nanoparticles initially deposited on the polymer film are redistributed and become incorporated into the forming polymer droplets, producing composite particles with a nanoparticle-enriched surface. The morphology and composition of the structures were confirmed by SEM, EDS mapping, Raman spectroscopy, AFM, and fluorescence microscopy, while geometric analysis provided insight into nanoparticle wetting at the polymer–water interface. The process represents a simple, template-free route to asymmetrically structured polymer–nanoparticle composites based on interfacial reorganization during thin-film dewetting. As an application-oriented proof of concept, doxorubicin was incorporated into the PCL phase and the resulting particles were evaluated using MDA-MB-231 triple-negative breast cancer cells. Doxorubicin-loaded particles reduced cell viability, confirming that the drug retained biological activity after incorporation into the polymer domains. Our approach provides a versatile route to hybrid polymer-inorganic microparticles with controlled surface composition and potential utility as functional coatings or surface-supported drug-delivery systems.