Iron Nanoparticle Composite Hydrogels for Studying Effects of Iron Ion Release on Red Blood Cell In Vitro Production

Growing numbers of complex surgical interventions increase the need for blood transfusions, which cannot be fulfilled by the number of donors. Therefore, the interest in producing erythrocytes from their precursors-the hematopoietic stem and progenitor cells (HSPCs)-in laboratories is rising. To enable this, in vitro systems are needed, which allow analysis of the effects of essential factors such as iron on erythroid development. For this purpose, iron ion-releasing systems based on poly(ethylene glycol) (PEG)-iron nanocomposites are developed to assess if gradual iron release improves iron bioavailability during in vitro erythroid differentiation. The nanocomposites are synthesized using surfactant-free pulsed laser ablation of iron directly in the PEG solution. The iron concentrations released from the material are sufficient to influence in vitro erythropoiesis. In this way, the production of erythroid cells cultured on flat PEG-iron nanocomposite hydrogel pads can be enhanced. In contrast, erythroid differentiation is not enhanced in the biomimetic macroporous 3D composite scaffolds, possibly because of local iron overload within the pores of the system. In conclusion, the developed iron nanoparticle-PEG composite hydrogel allows constant iron ion release and thus paves the way (i) to understand the role of iron during erythropoiesis and (ii) toward the development of biomaterials with a controlled iron release for directing erythropoiesis in culture.

Tissue Concentrations of Zinc, Iron, Copper, and Magnesium During the Phases of Full Thickness Wound Healing in a Rodent Model

Wound healing is a complex orchestration of processes involving cell proliferation, migration, differentiation, anabolism, and catabolism in order to restore skin continuity. Within these processes, elements such as metallic ions are involved due to their implications in cell behavior and enzymatic activity regulation. This study analyzed the kinetics of zinc, iron, copper and magnesium concentrations in a full thickness open wound rat model over 14 days. We made wounds with a diameter of 6 mm on the back of Lewis rats and let them heal naturally prior to analysis by histology and inductively coupled plasma mass spectrometry analysis. Histological and immunofluorescence analysis confirmed an inflammation phase until 7 days, epithelial proliferation phase from 16 h to 10 days, and remodeling phase from 7 days onward. These defined phases were correlated with the measured metal element kinetics. Zinc concentrations showed an inverted parabolic progression between 30.4 and a maximum of 39.9 μg/g dry weight. Magnesium values had a similar pattern between 283 and 499 μg/g dry weight. Copper concentrations, on the other hand, followed an inverted sigmoid trend with a decrease from 9.8 to 1.5 μg/g dry weight. Iron had a slight decrease in concentration for 24 h followed by an increase to a maximum of 466 μg/g dry weight. In conclusion, zinc, iron, and copper, even though differing in their total mass within the wound, exhibited concentration curve transitions at day 3. Interestingly, this time point correlates with the maximum proliferating keratinocyte rate during the proliferation phase.