Influence of carboxymethyl cellulose and calcium-crosslinked CMC coating of 3D-Printed hydroxyapatite scaffolds on the early hemostatic performance and osteoblastic compatibility

Successfully managing bl eeding bone defects relies on biomaterials capable of promoting early hemostasis alongside osteogenesis. While 3D-printed hydroxyapatite (3DP-HA) scaffolds possess osteoconductivity, their clinical utility can be limited by poor blood stability and inadequate initial hemostatic properties. To address these challenges, this preliminary study investigates the surface modification of 3DP-HA scaffolds using carboxymethyl cellulose (CMC) and its calcium-crosslinked derivative (CMC-Ca).

Scaffolds were coated with either 1% or 2% CMC, or a CMC-Ca complex at varying formulations (1:1, 1:2, and 2:1). Total porosity and mean pore diameter were evaluated via micro-computed tomography (micro-CT). Surface morphology and elemental properties were characterized via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Early in vitro hemostatic tendencies were evaluated through blood absorption and whole-blood clotting index (BCI) assays. Preliminary cytocompatibility and early osteogenic response were assessed by observing cell attachment via SEM and measuring alkaline phosphatase (ALP) activity at Day 7 using a human fetal osteoblast cell line (hFOB 1.19).

All modified formulations maintained total porosity ranging from 54.08% to 61.85%. Blood absorption capacity was comparable among all groups without statistically significant differences. For the in vitro clotting assay, the 2:1 CMC-Ca formulation exhibited a lower blood clotting index value than the other scaffold groups, suggesting a favorable initial coagulation response under the tested conditions. In vitro biological assays provided early descriptive evidence that the coatings permitted cell attachment and spreading by Day 7. Furthermore, ALP activity remained comparable across all groups, indicating that the surface modifications did not inherently suppress early-stage osteogenic signaling at the investigated time point.

This preliminary study demonstrates that surface-modified 3DP-HA scaffolds maintained macro-porosity while the addition of CMC and CMC-Ca coatings provided early indications of in vitro hemostatic potential and early osteogenic compatibility. In particular, the 2:1 CMC-Ca formulation showed a positive initial blood clotting tendency without descriptive impairment of osteoblastic function. While further comprehensive, higher-powered quantification and mechanistic assays are required, these initial results offer a potential baseline strategy for developing surface-modified bone grafts.