Use of polyvinylpyrrolidone-iodine solution for sterilisation and preservation improves mechanical properties and osteogenesis of allografts.

Allografts eliminate the disadvantages associated with autografts and synthetic scaffolds but are associated with a disease-transmission risk. Therefore, allograft sterilisation is crucial. We aimed to determine whether polyvinylpyrrolidone-iodine (PVP-I) can be used for sterilisation and as a new wet-preservation method. PVP-I-sterilised and preserved allografts demonstrated improved mechanical property, osteogenesis, and excellent microbial inhibition. A thigh muscle pouch model of nude mice showed that PVP-I-preserved allografts demonstrated better ectopic formation than Co60-sterilised allografts (control) in vivo (P < 0.05). Furthermore, the PVP-I-preserved group showed no difference between 24 h and 12 weeks of allograft preservation (P > 0.05). PVP-I-preserved allografts showed more hydrophilic surfaces and PVP-I-sterilised tendons showed higher mechanical strength than Co60-sterilised tendons (P < 0.05). The level of residual PVP-I was higher without washing and with prolonged preservation (P < 0.05). In vitro cellular tests showed that appropriate PVP-I concentration was nontoxic to preosteoblast cells, and cellular differentiation measured by alkaline phosphatase activity and osteogenic gene markers was enhanced (P < 0.05). Therefore, the improved biological performance of implanted allografts may be attributable to better surface properties and residual PVP-I, and PVP-I immersion can be a simple, easy method for allograft sterilisation and preservation.

[Acellular nerve allograft by chemical extraction in humans].

OBJECTIVE: To develop a procedure by which Schwann cells and myelin in the peripheral nerve could be removed while the basal lamina tubes remained intact, and to obtain a thick and long acellular nerve allograft in humans. METHODS: Four ulnar nerves 10.0 cm long and 4.0 - 5.0 mm in diameter were excised from a donated male body and cleaned from external debris. The nerves were treated with a solution of Triton X-100 and a solution of sodium deoxycholate at room temperature. After a final wash in water, the nerves were stored in phosphate-buffered saline (PBS, pH 7.2) at 4 degrees C. HE, luxol fast blue and fibrin staining were performed to visualize cells, myelin and basal membranes respectively and immunohistochemical staining was performed to visualize the presence of laminin, a Schwann cell lamina component, both in fresh and acellular nerve segments. To reveal overall structure better, methylene blue-fuchsin staining was performed in semithin section. The ultrastructure of acellular and fresh nerves were observed and photographed in a transmission electron microscope. RESULTS: The acellular human ulnar nerve was white long cylinder with well elasticity and ductility. HE, myelin and fibrin staining revealed that cells, axons and myelin sheath were removed and basal membrane was preserved after extraction procedure. Staining for the presence of laminin showed that the Schwann cell basal lamina component were present in the nerves after chemical treatment. Methylene blue-fuchsin staining and transmission electron microscopy showed that the myelin sheaths were absent in the extracted nerve segments and empty basal lamina tubes remained in the endoneurium. CONCLUSIONS: We developed an extracted procedure with the detergents of Triton X-100 and deoxycholate, by which cells, axons and myelin sheaths could be removed from a human ulnar nerve while the basal lamina tubes remain intact and a thick long acellular nerve allograft is obtained. The laminin, a Schwann cell basal lamina component, can be preserved in the acellular nerve.

[Growth activity of osteoblast on a novel strontium incorporated calcium sulfate].

OBJECTIVE: To investigate the growth activity of osteoblast on a novel strontium incorporated calcium sulfate and make comparison with normal calcium sulfate material. METHODS: Osteoblast was inoculated on samples and cell proliferation was measured on the 1st, 3rd, 5th days, and the activities of ALP and osteocalcin were observed on the 5th day. And microcosmic morphology of osteoblast was observed by scanning electron microscopy(SEM). RESULTS: Osteoblast grows robustly on tested material. Cell quantity on the surface of novel material was obviously higher than normal calcium sulfate material (P < 0.05). The activity of ALP and osteocalcin on novel material was 57.8% and 40.2% higher than on normal calcium sulfate material respectively (P < 0.05). On strontium incorporated surface, osteoblast spread well. Cells were polygonal with abundant cytoplasm and the morphology was active. CONCLUSION: Strontium incorporated calcium sulfate can sustain robust growth activity of osteoblast, which is promising to be used for bone substitute materials.

Porous allograft bone scaffolds: doping with strontium.

Strontium (Sr) can promote the process of bone formation. To improve bioactivity, porous allograft bone scaffolds (ABS) were doped with Sr and the mechanical strength and bioactivity of the scaffolds were evaluated. Sr-doped ABS were prepared using the ion exchange method. The density and distribution of Sr in bone scaffolds were investigated by inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). Controlled release of strontium ions was measured and mechanical strength was evaluated by a compressive strength test. The bioactivity of Sr-doped ABS was investigated by a simulated body fluid (SBF) assay, cytotoxicity testing, and an in vivo implantation experiment. The Sr molar concentration [Sr/(Sr+Ca)] in ABS surpassed 5% and Sr was distributed nearly evenly. XPS analyses suggest that Sr combined with oxygen and carbonate radicals. Released Sr ions were detected in the immersion solution at higher concentration than calcium ions until day 30. The compressive strength of the Sr-doped ABS did not change significantly. The bioactivity of Sr-doped material, as measured by the in vitro SBF immersion method, was superior to that of the Sr-free freeze-dried bone and the Sr-doped material did not show cytotoxicity compared with Sr-free culture medium. The rate of bone mineral deposition for Sr-doped ABS was faster than that of the control at 4 weeks (3.28 ± 0.23 µm/day vs. 2.60 ± 0.20 µm/day; p<0.05). Sr can be evenly doped into porous ABS at relevant concentrations to create highly active bone substitutes.

Nerve regeneration and functional recovery after a sciatic nerve gap is repaired by an acellular nerve allograft made through chemical extraction in canines.

The purpose of the present study is to test whether chemically extracted acellular nerve segments can be used to repair the sciatic nerve gap. Fifteen canines were divided into acellular nerve allografting group (ANG, six canines), autografting group (AG, six canines), and fresh nerve allografting group (FNG, three canines). The sciatic nerves on the right side of the animals were exposed, and 5-cm-long segments of the nerves were removed from the midthigh level and replaced by the three types of grafts. At 6 months after grafting, all animals in the ANG and AG had similar patterns of right posterior limb gait cycle and right ankle movements. Moreover, the animals in the ANG and AG had similar nerve regeneration, with dense regeneration fibers in the distal tibial nerves and obvious motor end plates in the target muscle. But in FNG, the area surrounding the graft was scarred as the result of inflammation, and there was a brown central area where there was little nerve regeneration. All of the above shows that chemical acellular nerve allografting can be used to repair a gap as long as 5 cm in the continuity of the sciatic nerve in canines and has similar effects to autografting.