Melanin Nanoparticles as a Safe and Effective Iron Chelation Therapy: An ex vivo Assessment of Placental Transfer in Pregnant Beta-Thalassemia

Nahla Bakhamis,1 Toluwalase Awoyemi,1 Manu Vatish,1 Helen Townley1,2 1Nuffield Department of Women’s & Reproductive Health, University of Oxford, Oxford, UK; 2Department of Engineering Science, University of Oxford, Oxford, UKCorrespondence: Helen Townley, Oxford University, Begbroke Science Park, Woodstock Road, Oxford, OX5 1PF, United Kingdom, Tel +44 1865 283792, Email [email protected]: Iron toxicity is a major contributor to adverse pregnancy outcomes in women with transfusion-dependent thalassemia. Currently used iron chelators are not recommended during pregnancy, as they can cross the placenta causing potential risk to the fetus. However, ceasing medication may adversely affect the mother’s health in both the short- and long-term.Objective: We previously demonstrated that melanin nanoparticles can effectively chelate iron, and this has been confirmed by others in iron-overloaded mice. This study aims to assess whether these nanoparticles cross the placenta and evaluate their biocompatibility and haemocompatibility.Study Design: A library of 50 nm, 200 nm, and 500 nm melanin nanoparticles were synthesized and coated with Polyethylene Glycol (PEG) to improve their stability. The particles were tested for chelating iron efficacy in and biocompatibility. An in vitro BeWo (choriocarcinoma) cell model and ex vivo human placental perfusion system were used to assess nanoparticle transplacental passage.Results: Melanin nanoparticles of all sizes were able to chelate iron with a maximum adsorption of 14 mm iron/g of material; significantly higher than Desferrioxamine (DFO) of the same concentration. It was also determined that PEGylated melanin nanoparticles with appropriate size (cut off 200 nm) could be restricted from passing across the placental barrier in an in vitro model using a human choriocarcinoma cell line and in an ex vivo human placental perfusion model. The particles did not cause red cell haemolysis or blood clotting at concentrations up to 1 mM.Conclusion: It was demonstrated herein that transport of MNPs across the placental barrier is highly dependent on particle size (cut off size of 200 nm PEGylated MNPs). Findings suggest the possibility of providing a safe method of iron chelation during pregnancy. Future work in in vivo models will be applied to study systemic particle interaction.Plain Language Summary: At present, clinicians are faced with the choice of whether to continue maternal chelation therapy with possible risk to the fetus, or to cease medication with risk to the mother. The latter may adversely affect the mother’s health long after delivery of the baby. Although there are very few clinical trials on using DFO during pregnancy, the use of the small MW DFO on pregnant women is contraindicated. Thus, DFO is classified by the Food and Drug Association as category C during pregnancy due to severe skeletal anomalies and teratogenic effects reported in animal studies. PEGylated melanin nanoparticles (MNPs) of 200 nm or larger are unable to cross the placenta, as shown in both an in vitro BeWo cell model and an ex vivo human placental perfusion model. These findings suggest that MNPs may be a safer option for iron chelation during pregnancy. However, pre-clinical animal testing and clinical trials are needed to determine overall interaction of MNPs in vivo before routine use in a clinical setting.The exclusion of pregnant women from clinical trials has limited research on medications specifically designed for pregnancy with only a couple of drugs developed in the past four decades.1 There is a critical need to fill the knowledge gap regarding safer and effective therapeutics in this population. The use of clinically approved nanoparticles in pregnancy has increased rapidly; with the Covid 19 vaccines developed by Pfizer and Moderna being prominent examples. These vaccines have been used in a large population of pregnant women without reports of unfavorable complications,2 paving the way for more nanoparticle medications to be used in the future. Keywords: Melanin, nanoparticles, beta thalassemia, placenta, iron chelation, BeWo, PEGylation