Synergistic Integration of Spin Crossover and Zinc Oxide in Transparent Films for Active Intelligent Packaging

TL;DR

A transparent film combining temperature-sensitive and antimicrobial properties is developed for smart packaging applications.

Contribution

A synergistic integration of spin crossover and zinc oxide in a transparent film for active intelligent packaging is demonstrated.

Findings

The SCO transition broadens and hysteresis width decreases with increasing ZnO loading.

The film maintains low active agent release and shows antiproliferative activity against MCF-7 cells at high concentrations.

The material offers scalable potential for food and pharmaceutical packaging with real-time thermal and antimicrobial functions.

Abstract

The development of multifunctional smart packaging materials capable of simultaneously monitoring temperature and suppressing microbial contamination is critical for next-generation food and pharmaceutical safety systems. In this study, we report the design and characterization of a polymeric film integrating a spin crossover (SCO)-based thermochromic sensor with zinc oxide (ZnO) nanoparticles serving as an antimicrobial agent. Beyond the individual functionalities, we demonstrate a synergistic effect between SCO and ZnO components. Notably, the SCO transition of the pristine SCO complex is broadened, and the hysteresis width of the transition is decreased (i.e., from 6 K to 1.5 K, 2 K, and 1.5 K for ZnO loading of 0.5%, 1%, and 2%, respectively), in the polysulfone–SCO–ZnO composites. Migration studies reveal that the co-existence of SCO and ZnO does not disrupt the low release profile of active agents, which remains low across ZnO loadings. The polymeric film exhibited dose-dependent antiproliferative activity against MCF-7 breast cancer cells, with a significant reduction in cell viability observed only at the highest tested concentration, indicating cytotoxic potential. This multifunctional platform represents a promising advancement in smart packaging design, enabling real-time thermal indication combined with the integration of ZnO as a literature-established antimicrobial component, within a non-toxic, and visually transparent system. Collectively, the material’s properties offer promising scalability for both food and pharmaceutical packaging applications where visual clarity, antimicrobial integrity, and temperature monitoring are imperative.

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