TEMPO-mediated oxidation of starch: A review

Starch, a renewable and biodegradable polymer, has gained increasing attention as a functional material in industrial and biomedical applications. TEMPO-mediated oxidation has emerged as a key method for modifying starch by regioselectively oxidizing the C6-OH group to an aldehyde and/or a carboxylic moiety. This review critically evaluates advancements in TEMPO oxidation techniques, including conventional NaClO/NaBr systems, bromide-free approaches, and enzyme-mediated laccase–TEMPO pathways, with emphasis on their efficiency, selectivity, and environmental implications. The oxidation of starch enhances its hydrophilicity and improves functionality, making it suitable for various applications in the pharmaceutical, food, and packaging industries. The impact of TEMPO-mediated oxidation on starch is analyzed across multiple structural levels, including molecular weight distribution, granule morphology, crystallinity, and physicochemical behavior. It demonstrates that using this oxidation technique in tandem with mechanical-assisted approaches shows promise for producing nanostructured oxidized starch for drug delivery applications. Applications in hydrogels, nanoparticles, and biomaterials are evaluated, highlighting the role of carboxylated starch in gelation, encapsulation, and controlled release systems. Finally, this review proposes a design-oriented perspective for TEMPO-mediated starch oxidation, identifying key knowledge gaps in depolymerization control, process standardization, and application-driven material optimization, thereby providing a framework for the rational development of sustainable starch-based functional materials.