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A Pre-Set Calcium Sulfate/Hydroxyapatite Biomaterial as an Antibiotic-Eluting Bone Extender and a Carrier for BMP-2 : A Pilot Study in a Rabbit Posterolateral Spinal Fusion Model

Huang, Jintian LU ; Lukoševičiūtė, Gintarė ; Mrkonjic, Filip LU ; Alidadi, Hadis LU ; Jakstas, Domantas ; Sebastian, Sujeesh LU orcid ; Lidgren, Lars LU ; Tägil, Magnus LU and Raina, Deepak Bushan LU (2026) In Journal of Functional Biomaterials 17(3).
Abstract

Synthetic biomaterials used as bone graft extenders (BGE) in spinal fusion surgery can supplement but do not replace autologous bone. This pilot study evaluated a calcium sulfate/hydroxyapatite (CaS/HA) material as an antibiotic-eluting BGE and a carrier for bone morphogenetic protein-2 (BMP-2) in a rabbit posterolateral lumbar (L4–L5) spinal fusion model (PLF). Pre-set CaS/HA beads were loaded with tobramycin (TOB) and tested for in vitro antibiotic release and antibacterial activity against Staphylococcus aureus. For the in vivo PLF study, CaS/HA beads were used in two treatment strategies: (1) CaS/HA + TOB + autograft (left side) and (2) CaS/HA + BMP-2 (right side). Serum levels of TOB were quantified and spinal fusion was evaluated... (More)

Synthetic biomaterials used as bone graft extenders (BGE) in spinal fusion surgery can supplement but do not replace autologous bone. This pilot study evaluated a calcium sulfate/hydroxyapatite (CaS/HA) material as an antibiotic-eluting BGE and a carrier for bone morphogenetic protein-2 (BMP-2) in a rabbit posterolateral lumbar (L4–L5) spinal fusion model (PLF). Pre-set CaS/HA beads were loaded with tobramycin (TOB) and tested for in vitro antibiotic release and antibacterial activity against Staphylococcus aureus. For the in vivo PLF study, CaS/HA beads were used in two treatment strategies: (1) CaS/HA + TOB + autograft (left side) and (2) CaS/HA + BMP-2 (right side). Serum levels of TOB were quantified and spinal fusion was evaluated after 12 weeks. TOB exhibited a rapid initial release, followed by a decline below detectable levels after 6 h in vitro and 48 h in vivo. TOB-loaded CaS/HA beads demonstrated in vitro antibacterial activity for 19 days. In the PLF study, 5/6 and 6/6 specimens were fused radiologically in the TOB and BMP groups, respectively, and 100% using mechanical testing. Micro-CT analysis showed no significant difference in bone volume between the TOB and BMP-2 groups (364 ± 84 vs. 479 ± 95 mm3). Histology verified continuous bone bridging in both groups. Our in vitro findings indicate that locally added TOB could protect the CaS/HA material from bacterial colonization and did not adversely impact the CaS/HA material negatively to act as BGE. The addition of low-dose BMP-2 to the CaS/HA material proved effective in building bone without the need to harvest autologous bone. In summary, this pilot PLF study demonstrates that the tested CaS/HA material combined with BMP-2 could replace autologous bone harvesting in spinal fusion surgery. Addition of TOB could potentially protect the material from bacterial colonization during the early post-operative period but further studies in infection models are warranted.

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author
; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
BMP-2, bone graft extender, ceramic material, infection, spinal fusion
in
Journal of Functional Biomaterials
volume
17
issue
3
article number
118
publisher
MDPI AG
external identifiers
  • scopus:105034269462
  • pmid:41893174
ISSN
2079-4983
DOI
10.3390/jfb17030118
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2026 by the authors.
id
4a7a92c7-1cf8-4b89-af49-a3627067edb0
date added to LUP
2026-05-27 14:57:46
date last changed
2026-05-28 03:00:03
@article{4a7a92c7-1cf8-4b89-af49-a3627067edb0,
  abstract     = {{<p>Synthetic biomaterials used as bone graft extenders (BGE) in spinal fusion surgery can supplement but do not replace autologous bone. This pilot study evaluated a calcium sulfate/hydroxyapatite (CaS/HA) material as an antibiotic-eluting BGE and a carrier for bone morphogenetic protein-2 (BMP-2) in a rabbit posterolateral lumbar (L4–L5) spinal fusion model (PLF). Pre-set CaS/HA beads were loaded with tobramycin (TOB) and tested for in vitro antibiotic release and antibacterial activity against Staphylococcus aureus. For the in vivo PLF study, CaS/HA beads were used in two treatment strategies: (1) CaS/HA + TOB + autograft (left side) and (2) CaS/HA + BMP-2 (right side). Serum levels of TOB were quantified and spinal fusion was evaluated after 12 weeks. TOB exhibited a rapid initial release, followed by a decline below detectable levels after 6 h in vitro and 48 h in vivo. TOB-loaded CaS/HA beads demonstrated in vitro antibacterial activity for 19 days. In the PLF study, 5/6 and 6/6 specimens were fused radiologically in the TOB and BMP groups, respectively, and 100% using mechanical testing. Micro-CT analysis showed no significant difference in bone volume between the TOB and BMP-2 groups (364 ± 84 vs. 479 ± 95 mm<sup>3</sup>). Histology verified continuous bone bridging in both groups. Our in vitro findings indicate that locally added TOB could protect the CaS/HA material from bacterial colonization and did not adversely impact the CaS/HA material negatively to act as BGE. The addition of low-dose BMP-2 to the CaS/HA material proved effective in building bone without the need to harvest autologous bone. In summary, this pilot PLF study demonstrates that the tested CaS/HA material combined with BMP-2 could replace autologous bone harvesting in spinal fusion surgery. Addition of TOB could potentially protect the material from bacterial colonization during the early post-operative period but further studies in infection models are warranted.</p>}},
  author       = {{Huang, Jintian and Lukoševičiūtė, Gintarė and Mrkonjic, Filip and Alidadi, Hadis and Jakstas, Domantas and Sebastian, Sujeesh and Lidgren, Lars and Tägil, Magnus and Raina, Deepak Bushan}},
  issn         = {{2079-4983}},
  keywords     = {{BMP-2; bone graft extender; ceramic material; infection; spinal fusion}},
  language     = {{eng}},
  number       = {{3}},
  publisher    = {{MDPI AG}},
  series       = {{Journal of Functional Biomaterials}},
  title        = {{A Pre-Set Calcium Sulfate/Hydroxyapatite Biomaterial as an Antibiotic-Eluting Bone Extender and a Carrier for BMP-2 : A Pilot Study in a Rabbit Posterolateral Spinal Fusion Model}},
  url          = {{http://dx.doi.org/10.3390/jfb17030118}},
  doi          = {{10.3390/jfb17030118}},
  volume       = {{17}},
  year         = {{2026}},
}