Fibroin/sulfated alginate membranes containing exosomes of stem cells treated with B and Zn-doped hydroxyapatite for periosteal tissue engineering

Abstract

Periosteal regeneration requires tissue engineering strategies that simultaneously support osteogenesis, angiogenesis, and immunomodulation. In this study, fibroin/sulfated alginate (F/sA) composite membranes loaded with exosomes derived from human adipose-derived stem cells (hADSCs) treated with pure, 4 mol% B-doped, and 4 mol% B and 8 mol% Zn-doped hydroxyapatite (HA) were developed for periosteal tissue engineering. It was hypothesized that incorporation of sA and HA-conditioned exosomes enhance osteoimmunomodulation while preserving scaffold integrity. F/sA membranes with varying sulfated alginate content (0–20 wt%) were fabricated and characterized. Increasing sulfated alginate content enhanced water uptake and degradation while reducing tensile strength and Young’s modulus. 95:5 F/sA ratio was identified as optimal exosome delivery composition, exhibiting the highest hADSC viability and reducing IL1B and CASP1 levels in THP-1 macrophages (p < 0.05). It was also found that exosomes isolated from pure and doped HA-treated hADSCs showed treatment-dependent alterations in cargo. The 8 mol% B-doped HA group significantly increased exosome yield, while all HA treatments reduced protein/particle and DNA/particle. Doped HA treatments significantly increased RNA/particle (p < 0.05). Exosome-loaded F/sA membranes enhanced early cell attachment and proliferation and significantly promoted osteogenic differentiation of hADSCs, increasing RUNX2, COL1A1, and OCN expression. Immunomodulatory effects were observed for all exosome groups, except the 4 mol% B and 8 mol% Zn-doped HA group, which significantly increased CASP1 expression. Overall, this study demonstrates that HA doping modulates exosomal composition in a dopant-dependent manner and that exosome-functionalized F/sA membranes constitute a multifunctional periosteal substitute with tunable properties.