Especially in the context of hard tissue defects, electrospun nonwovens are a versatile material to be applied as biodegradable implantable scaffolds. Owing to fiber diameters in the micro- and nanometer range and a high surface-to-volume ratio with high porosity, they can mimic the natural structure of the extracellular matrix (ECM) [1] and are replaced within remodelling and regeneration processes in the long term. [2] Yet, the treatment of bone matrix defects with porous synthetic materials for guided bone regeneration often fails due to missing mechanical and biological cues. The blood plasma binding protein Fetuin A offers a high calcium affinity, thus enhancing the formation of initial CaP crystallization nuclei and promoting calcium phosphate mineralization. [3]

PLLA-co-PEG electrospun nonwovens have been pre-treated with O2-plasma, functionalized by covalent bonding with Fetuin A and subsequently calcified in vitro. CaP affinity of the functionalized nonwovens has been investigated with a tailored in vitro-calcification protocol. CaP load was quantified using a photochemical assay and morphological characterization of the mineralization was performed using SEM. Cell seeding behaviour over 48h was investigated using human MG-63 osteoblasts, followed by the determination of metabolic activity as well as cell morphology and migration via fluorescence staining and SEM. The type I collagen and cytokine and chemokine levels were verified via ELISA.

Superficially immobilized Fetuin A complexes calcium ions from the surrounding medium, which act as crystallization nuclei initializing biomimetic hydroxyapatite crystallites mineralization (Fig. 1 B). CaP formation takes place homogeneously distributed over the entire surface of the functionalized material. Against the use of seed crystals, the entire fibers are thus surrounded by a CaP layer, maintaining the fibrous ECM-like morphology with its high surface-to-volume ratio and porous fiber interstices. This morphology supports both cells and hydroxyapatite to replace the scaffold structure from within. Initial results indicate a highly elevated metabolic activity on Fetuin A functionalized nonwoven, which led to increased cell ingrowth with spread cell morphology and dense cell layers. ELISA showed decreased collagen levels in the supernatant of Fetuin A surfaces, maybe indicating binding of collagen propeptides to Ca2+ growth nuclei. [4]
Fetuin A modification of biodegradable nonwovens enables a distinct CaP crystal growth on the material surface being a feasible way towards enhanced biomineralization and osteoblastic growth behaviour.