Enhancing the aqueous solubility of hemin at physiological pH through encapsulation within polyvinylpyrrolidone nanofibres

Iron deficiency anaemia is a widespread global nutritional disorder, affecting almost a quarter of the global population and contributing to impaired cognitive development, adverse pregnancy outcomes, and weakened immune function. Despite its prevalence, oral iron supplementation remains problematic due to the poor solubility and low bioavailability of ferric supplements, coupled with the frequently experienced gastrointestinal side effects associated with ferrous iron salt supplements. Hemin, a chloride-ligated ferric analogue of heme, presents a potentially safer alternative. However, its poor solubility at neutral pH limits its practical application in oral supplementation. Here, we aimed to develop a novel formulation for hemin using electrospun polyvinylpyrrolidone (PVP) nanofibres, as a platform to enhance the aqueous solubility of hemin and thereby improve its bioavailability. Hemin at various concentrations was successfully encapsulated within PVP nanofibres. The nanofibres were characterised for their morphology, physicochemical properties, encapsulation efficiency and dissolution properties. Notably, the nanofibres dissolved rapidly in phosphate-buffered saline (pH 7.4), forming hemin–PVP nanoparticles (10–80 nm in diameter) and larger aggregates (200–2000 nm in diameter) that maintained hemin in a soluble form. This approach achieved a total solubilised hemin concentration of 273 µM, representing an approximately 200-fold enhancement in solubility. These findings highlight the potential of electrospun hemin–PVP nanofibres as a promising component of an oral iron supplement, offering enhanced solubility and the potential of improved bioavailability for cellular uptake.