Poly(propylene fumarate) reinforced dicalcium phosphate dihydrate cement composites for bone tissue engineering

Authors

Daniel L. Alge, Jeffrey Bennett, Trevor Treasure, Sherry Voytik-Harbin, W. Scott Goebel, Tien-Min Gabriel Chu

Abstract

Calcium phosphate cements have many desirable properties for bone tissue engineering, including osteoconductivity, resorbability, and amenability to rapid prototyping-based methods for scaffold fabrication. In this study, we show that dicalcium phosphate dihydrate (DCPD) cements, which are highly resorbable but also inherently weak and brittle, can be reinforced with poly(propylene fumarate) (PPF) to produce strong composites with mechanical properties suitable for bone tissue engineering. Characterization of DCPD–PPF composites revealed significant improvements in mechanical properties for cements with a 1.0 powder to liquid ratio. Compared with nonreinforced controls, flexural strength improved from 1.80 ± 0.19 MPa to 16.14 ± 1.70 MPa, flexural modulus increased from 1073.01 ± 158.40 MPa to 1303.91 ± 110.41 MPa, maximum displacement during testing increased from 0.11 ± 0.04 mm to 0.51 ± 0.09 mm, and work of fracture improved from 2.74 ± 0.78 J/m2 to 249.21 ± 81.64 J/m2. To demonstrate the utility of our approach for scaffold fabrication, 3D macroporous scaffolds were prepared with rapid prototyping technology. Compressive testing revealed that PPF reinforcement increased scaffold strength from 0.31 ± 0.06 MPa to 7.48 ± 0.77 MPa. Finally, 3D PPF–DCPD scaffolds were implanted into calvarial defects in rabbits for 6 weeks. Although the addition of mesenchymal stem cells to the scaffolds did not significantly improve the extent of regeneration, numerous bone nodules with active osteoblasts were observed within the scaffold pores, especially in the peripheral regions. Overall, the results of this study suggest that PPF–DCPD composites may be promising scaffold materials for bone tissue engineering.

Link to Articles

http://dx.doi.org/10.1002/jbm.a.34130

Biofunctionalization of the implant surface with different concentrations of a synthetic peptide (P-15)

Authors

R. Lutz, C. Prechtl, J. Nonhoff, T. Weisel, C. J. Damien, K. A. Schlegel

Abstract

This study aimed at identifying the ideal concentration of a biofunctional surface coating of dental implants with a synthetic peptide (P-15). In a previous study, P-15 was shown to enhance osseointegration parameters. Implants (modified ANKYLOS® A8; FRIADENT Plus® surface) with five different concentrations (0–400 μg/ml) of a P-15 coating as well as uncoated controls were inserted in the frontal bone of 45 adult domestic pigs. The histomorphometric and microradiographic findings for the coated implants were compared to those for the uncoated ones after 7, 14, and 30 days. No significant differences were observed comparing the peri-implant bone density between the coated and uncoated implants The bone-to-implant contact, as the primary histological parameter for osseointegration, showed high rates for all surfaces investigated (between 73.3 ± 17.9% for the control and 81.9 ± 15.2% for P15 20 μg/ml after 30 days). No significant benefit on osseointegration of a biofunctional P-15 coating of dental implants could be displayed in the present study.

Link to Article

http://dx.doi.org/10.1111/j.1600-0501.2012.02455.x

Beta-tricalcium phosphate particles as a controlled release carrier of osteogenic proteins for bone tissue engineering

Authors

Junli Hu, Yaping Hou, Hyejin Park, Min Lee

Abstract

Beta-tricalcium phosphate (β-TCP) has been widely used as bone substitutes and delivery carriers of osteogenic proteins. However, low protein carrying capacity and agent burst release profiles of β-TCP limit their usage. This study investigates strategies to enhance protein carrying capacity of β-TCP particles with reduced initial burst by surface etching in citric acid solution or by creating apatite coatings with the simulate body fluid immersion approach. The release kinetics of protein from the modified β-TCP particles was investigated using Nel-like molecule-1 (Nell-1), a novel osteogenic protein, as a model protein. Although chemical etching treatments reduced the initial burst release of protein from the particles, a rapid burst release was observed with high protein dose. In contrast, the burst release of protein was significantly reduced by the apatite coating and a high protein dose was successfully delivered over a prolonged period from the apatite-coated particles. Protein release was further modulated by simultaneously delivering proteins from two different substrates: acid-etched and apatite-coated particles. The bioactivity of the protein was preserved during the loading procedure onto the particles. In addition, protein-loaded particles maintained biological activity in the lyophilized state over 4 weeks. These findings suggest that the protein carrying capacity of β-TCP can be modulated by surface modification, which has a potential for use as a protein carrier with controlled release.

Link to Article

http://dx.doi.org/10.1002/jbm.a.34115

A Novel Calcium Aluminate-Melatonin Scaffold Enhances Bone Regeneration Within A Calvarial Defect

Authors

William P. Clafshenkel, James L. Rutkowski, Rachelle N. Palchesko, Jared D. Romeo, Ken A. McGowan, Ellen S. Gawalt, Paula A. Witt-Enderby

Abstract

Over 500,000 bone graft or bio-implant procedures are performed annually in the United States. It has been reported that osseous autograft procurement may result in donor site complications and bio-implant allografts have been associated with disease transmission. Ceramic scaffolds are only osteoconductive, limiting their clinical use. The objective of this study was to create a bone filler substitute with regenerating properties similar to natural bone. Therefore, melatonin and platelet-rich plasma (PRP) were utilized for their known osteoinductive properties. It was hypothesized that melatonin and/or PRP would enhance the osteoinductive and osteoconductive properties of calcium aluminate (CA) scaffolds to promote bone regeneration in a model of calvarial defects. The biocompatibility of CA and CA-Mel scaffolds were tested in vitro and in vivo. Data show that CA-Mel scaffolds, in comparison to CA scaffolds, enhanced the adhesion, viability and proliferation of normal human osteoblasts (NHost) cells but not that of NIH 3T3 fibroblasts. Data also showed that human adult mesenchymal stem cells grown on CA or CA-Mel scaffolds showed a time-dependent induction into osteoblasts over 14 days revealed through scanning electron microscopy and by alkaline phosphatase analyses. Implantation of CA-Mel scaffolds into critical size calvarial defects in female, ovariectomized rats showed that the CA-Mel scaffolds were biocompatible, allowed for tissue infiltration and showed evidence of scaffold biodegradation by 3 and 6 months. Bone regeneration, assessed using fluorochrome labeling at 3 and 6 months, was greatest in animals implanted with the CA-Mel scaffold. Overall, results from this study show that CA-Mel scaffolds were osteoconductive and osteoinductive.

Link to Article

http://dx.doi.org/10.1111/j.1600-079X.2012.00989.x

PEG matrix enables cell-mediated local BMP-2 gene delivery and increased bone formation in a porcine critical size defect model of craniofacial bone regeneration

Authors

Falk Wehrhan, Kerstin Amann, Aart Molenberg, Rainer Lutz, Friedrich W. Neukam, Karl A. Schlegel

Abstract

This study addressed the suitability of a polyethylene glycol (PEG) matrix as scaffold for cell-mediated local BMP-2 gene transfer in a calvarial critical size defect (CSD) model. PEG matrix (degradation time 10 days) and PEG membrane (degradation time 120 days) were used in the pig calvarial model. Cylindrical (1 × 1 cm) CSD (9 per animal; 20 animals) were filled with: (i) HA/TCP, covered by PEG membrane (group 1); (ii) HA/TCP, mixed with PEG matrix (group 2); and (iii) HA/TCP mixed with BMP-2 transfected osteoblasts and PEG matrix (group 3). BMP-2/4 gene transfer: liposomal in vitro transfection of BMP-2/V5-tag fusion-protein. Quantitative histomorphometry (toluidine blue staining) after 2, 4 and 12 weeks assessed bone formation. Semiquantitative immunohistochemistry estimated the expression of BMP-2 and V5-tag. Group 3 showed significantly higher new bone formation than groups 1, 2 at 4 (P < 0.05) and 12 (P < 0.02) weeks. BMP-2-V5-tag was detected for 4 weeks. BMP-2 expression in group 3 was higher compared to all other groups after 2 and 4 (P < 0.02) weeks. The PEG matrix serves as scaffold for cell-mediated BMP-2 gene delivery in guided bone regeneration facilitating cell survival and protein synthesis for at least 4 weeks. Local BMP-2 gene delivery by PEG matrix-embedded cells leads to increased bone formation during critical size defect regeneration.

Link to Article

http://dx.doi.org/10.1111/j.1600-0501.2011.02223.x

Effect of Guided Tissue Regeneration on Newly Formed Bone and Cementum in Periapical Tissue Healing after Endodontic Surgery: An In Vivo Study in the Cat

Authors

Zvi Artzi, Nadav Wasersprung, Miron Weinreb, Marius Steigmann, Hari S. Prasad, Igor Tsesis

Abstract

The purpose of this study was to evaluate the influence of anorganic bovine bone as a grafted biomaterial on newly formed bone and cementum in periapical regions after surgical endodontic treatment in cats. After inducing apical periodontitis in 9 cats, root canal and surgical endodontic treatment were performed on 72 roots of first and second maxillary premolars. Bone defects were treated with biomaterial particles + a membrane, biomaterial only, a membrane only, or left unfilled (control). Histomorphometry on nondecalcified sections were performed at 3 and 6 months after surgery. Analysis of variance with repeated measures was used within 2 and 3 subject factors to analyze newly formed bone, cementum, biomaterial conduction, and resorption. At each time period, bone formation was greater at the grafted membrane-protected sites than in the grafted-unprotected sites. At 6 months, the bone area fraction at membrane nongrafted sites was greater than in the grafted-protected sites. The new cementum was significantly greater at 6 months than at 3 months and greater at the grafted membrane-protected sites over the unprotected ones at 6 months. Statistically, the grafted biomaterial, the membrane, and the time contributed significantly to the amount of new bone (P < .05) with no significant interaction. Biomaterial osteoconduction was significantly affected by the time. All 3 variables showed a significant interaction on new cementum. There was significantly more bone formation after surgical endodontic treatment when membrane and bone grafts were used as compared with bone grafts only or unfilled control sites. However, it appears that the key factor to the enhanced tissue regeneration is the membrane and not the grafted biomaterial.

Link to Article

http://dx.doi.org/10.1016/j.joen.2011.10.002