Skip to main content
2024 BMES Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.

Biomaterials

Biomaterials - Poster Session B

Poster B7 - Design and Characterization of Iron Functionalized Colloidal Hydrogel as Biomaterial

Thursday, October 24, 2024
2:45 PM - 3:45 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Hydrogels are an important group of biomaterials used in various applications for controlled release, regenerative tissue engineering, and sensing applications. Colloidal gels, unlike monolithic mesh-like hydrogels, are formed from aggregation of submicron colloidal particles and offer significant advantage to regulate the mechanomorphology through control of aggregation kinetics. Transition metals and their complexes offer unique combination of properties to impart characteristic biofunctionality. Thus, a metal containing colloidal gel can be engineered to combine these characteristic features in a well-defined design. To develop these gels, polyurethane (PU) based colloidal gels were engineered by aggregating positively charged PU colloids with equimolar complexes of ethylene diamine tetra acetic acid (EDTA) and iron (Fe) which contain net residual negative charge. Using two complexes of Fe-EDTA based on the oxidation states of Fe (i.e., +2 and +3), Fe(II)-EDTA and Fe(III)-EDTA were used to aggregate the positively charged PU colloids through electrostatic interactions to form the gels with defined physicochemical and mechanomorphological properties. Specifically, the microstructural morphology of the gels can be expected to be a more porous structure from the dianionic complex Fe(II)-EDTA mediated aggregation which will form a more linear network of particles whereas a relatively dense structure from the monoanionic complex Fe(III)-EDTA mediated aggregation which will form compact aggregates (Fig. 1).

Materials and

Methods:  Colloidal gels were formed through the aggregation of positively charged PU colloids by complexes of Fe(II)-EDTA and Fe(III)-EDTA with a net charge of -2 and -1, respectively. Gels were formed over a range of PU colloid particle fractions and complex concentrations. Complexes were formed by combining equimolar solutions of tetra-sodium EDTA (T-EDTA) and iron chloride (for each oxidation state, FeCl2 and FeCl3) at each desired concentration. Analysis and characterization of Fe(II)-EDTA and Fe(III)-EDTA aggregated gels were performed through fluorescent imaging, rheology, and cell culture. TRITC fluorescent imaging was performed at 4x and 10x magnification to characterize the aggregation of Fe(II)-EDTA and Fe(III)-EDTA mediated gels at particle fractions of 1, 2, and 5 wt% and aggregation reagent concentrations of 0.125, 0.25, and 0.5 M. Non-aggregated PU colloid was used as a control at matching particle fractions. Nile red was used to stain a portion of PU colloid during its synthesis. Elastic (storage, G’) and viscous (loss, G”) moduli were measured from amplitude strain sweep at constant frequency of 1Hz with 10 and 50 wt% particle fraction gels aggregated by 0.125, 0.25, 0.5 M Fe(II)-EDTA and Fe(III)-EDTA. Non-aggregated PU colloid was used as a control at identical particle fractions. Cytotoxicity was evaluated for 0.5M of each aggregation reagent and performed using mesenchymal stem cells. DNA viability of these cells was measured using PicoGreen assay.

Results, Conclusions, and Discussions: Results show that the positively charged PU colloids were effectively aggregated with Fe-EDTA complexes through electrostatic interactions. Fluorescent microscopic analysis showed that the Fe(II)-EDTA mediated aggregations yielded a more porous and linear structure while the Fe(III)-EDTA mediated aggregations were dense and compact as expected. We can infer that the aggregation kinetics in the formation of these gels is therefore dependent on the dianionic and monoanionic charges of the Fe(II)-EDTA and Fe(III)-EDTA complexes, respectively. In cell culture both Fe(II)-EDTA and Fe(III)-EDTA demonstrated minimum cytotoxicity. From rheology, both gels demonstrated marked improvement in elastic solid-like mechanical characteristics compared to the non-aggregated PU colloid control. In conjunction with the known biofunctionality of iron, this suggests future viability for iron functionalized colloidal gels to be used in broad therapeutic settings such as drug delivery, controlled release, and regenerative tissue engineering. Fe-EDTA aggregated colloidal gels may potentially provide an extracellular scaffolding for tissue regeneration around which the incorporated iron may exhibit its known antibacterial properties to improve therapeutics outcomes.

Acknowledgements (Optional):