Bone scaffolds

Another solution proposed for the low-temperature deposit process for fluorhy-droxyapatite onto porous zirconia bone scaffold was reported by Kim et al. [161], It is based on the immersion of the scaffold in a slurry of dispersed HA-FA powders in polyvinylbutyl for several hours, followed by drying and subsequent heat treatments at 800°C and 1200°C for binder (polyvinylbutyl) burnout. The process can be repeated fora multilayer film deposit. 

Meechaisue, C., Wutticharoenmongkol, P., Waraput, R., Huangjing, T., Ketbumrung, N., Pavasant, P., and Supaphol, P. "Preparation of electrospun silk fibroin fiber mats as bone scaffolds A preliminary study". Biomed. Mater. 2(3), 181-188 (2007). 

Ceramics Hydroxyapatite Bone cavity fillings, ear implants, vertebrae replacement, hip implant coatings, bone scaffolds Bioactive Cao and Hench (1996) and Lobel and Hench (1998)... 

Garcia-Alonso, D. (2009) Plasma spray deposition of hydroxyapatite-based composites as a step towards bone scaffolds. Unpublished PhD thesis. Dublin City University, Dublin, Ireland. 

Kim, H.E., Kim, H.M., and Ko, J.S. (2003a) Porous Zr02 bone scaffold coated with hydroxyapatite with fluorapatite intermediate layer. Biomaterials, 24, 3277-3284. 

Reves B (2008) Preliminary investigation of lyophilization to improve drug delivery of chitosan-calcium phosphate bone scaffold construct. MS Thesis, Biomedical Engineering, University of Memphis... 

Reves BT et al (2009) Lyophilization to improve drug delivery for chitosan-calcium phosphate bone scaffold construct a preliminary investigation. J Biomed Mater Res B Appl Biomater 90(1) 1-10... 

Hariraksapitak and Supaphol [45] prepared functional bone scaffolds capable of enhanced physical, mechanical, and biological performances. The materials used to fabricate the porous scaffolds were hyaluronan and gelatin (1 1 w/w blend), and the reinforcing filler was nanochitin obtained from acid-hydrolyzed a-chitin. 

Liao, S.S. et al.. Hierarchically biomimetic bone scaffold materials nano-HA/collagen/PLA composite. /. Biomed. Mater. Res., 2004,69B 158-65. 

Wang, X., Schroder, H.C., Muller, W.E., 2014. Enzymatically synthesized inorganic polymers as morphogenetically active bone scaffolds application in regenerative medicine. Int. Rev. Cell Mol. Biol. 27. 

Besides the mere structural design of bone scaffolds, the use of proteins or peptides guiding cellular behavior is also widely applied due to the large clinical information from therapies of bone fractures. For example, lin et al. investigated the effect of a BMP-2-related peptide incorporated in a PLGA-(PEG-ASP)n copolymer on bone formation in vitro using BMSCs and in vivo ectopic bone formation in Wistar rats. The modified composites showed much better in vitro results compared to tmmodified controls in terms of cell attachment, proliferation. 

Due to the inherent problems associated with allografts, autografts, and inert synthetic materials, research has moved towards the development of synthetic bioactive materials that mimic the natural structure and function of native bone tissue. In order to develop an ideal synthetic bone scaffold, the following attributes must be considered (Fig. 5) [36] ... 

Kedong, S., Wenfang, L., Yanxia, Z., Hong, W., Ze, Y, Mayasari, L., Tianqing, L., 2014. Dynamic fabrication of tissue-engineered bone substitutes based on derived cancellous bone scaffold in a spinner flask bioreactor system. Appl. Biochem. Biotechnol. 174, 1331-1343. 

Marcos-Campos, L, Marolt, D., Petridis, P., Bhumiratana, S., Schmidt, D., Vunjak-Novakovic, G., 2012. Bone scaffold architecture modulates the development of mineralized bone matrix by human embryonic stem cells. Biomaterials 33, 8329-8342. 

Inorganic particles have also been used to produce electrospun scaffolds. Hydroxyapatite (HA) is a calcium phosphate-based ceramic present in natural bone, which has been evaluated for the production of bone scaffolds. Electrospun scaffolds were produced from a blend of PLGA and nanosized HA. When MSC were cultivated on the scaffolds, their osteogenic differentiation was favored. 

Killeen D, Frydrych M, Chen B (2012) Porous poly(vinyl alcohol)/sepiolite bone scaffolds preparation, stracture and mechanical properties. Mater Sci Eng C Biomimetic Supramol Syst 32 749-757... 

Fig. 3.11 Examples of FDM/3D printed products from the Wake Forest Institute for Regenerative Medieine. Shown are ear, nose and bone scaffolds that can be coated with cells to grow body parts. Source Laurie Rubin, Smithsonian Magazine, http //www.smithsonianmag.com/seience-nature/ what-lies-ahead-for-3-d-printing-37498558/ o2oFcIJ14BJlIwDX.99...

Abstract The mechanical and biological properties and applicability of the most important polymers for bone regeneration are described. Fabrication techniques for improving applicability of the the polymers are examined with particular attention to tissue engineering, bone scaffold and drug delivery. 

Key words synthetic polymers, tissue engineering, bone scaffold, hydrogels, drug delivery. 

The chemistry of polyurethane scaffolds for tissue regeneration has been reviewed [5,12]. In this section, polyurethane chemistry relevant to bone scaffolds will be presented. 

This new knowledge could be applied to the design of rigid polyurethanes for bone scaffolds with antibacterial properties. 

Blaker JJ, Nazhat SN, Maquet V, Boccaccini AR. Long-term in vitro degradation of PDLLA/Bioglass (R) bone scaffolds in acellular simulated body fluid. Acta Biomater 2011 7 829-40. 

Agglomeration of chitosan microspheres was used as a technique for fabrication of bone scaffolds by a complex process of chitosan spheres extrusion, scaffold formation by compression followed by the spheres agglomeration and bonding with crosslinking agent (STPP, sodium tripolyphosphate) [117]. 

Sombatmankhong, K., Sanchavanakit, P. Pavasant, and P. Supaphol (2007). Bone scaffolds from electrospun fiber mats of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and their blend. Polymer 48(5) 1419-1427. 

The slow degradation rate of polycarbonates has led to its investigation in orthopaedic tissue engineering applications. Additionally, P(DTR carbonate) elicits a response for bone ingrowth at the bone-polymer implant interface, supporting the use of P(DTR carbonate) as a bone scaffold [84]. Recent studies have shown that osteoblast cells do attach to the surface of P(DTR carbonate). Results indicate that these osteoblasts maintained their phenotype and rounded cell morphology [85]. 

Common long bone defect models include the rabbit radial model (most popular), rat femoral model, and the dog radial model. A composite bone scaffold consisting of nano-hydroxyapatite, collagen, and PLA was found to integrate the rabbit radial defect after 12 weeks [49]. The effect of bone morphogenetic protein was evaluated in the rat femoral defect model [4]. It should be noted that the rat model requires either internal or external fixation. In the dog model, ulnae fractures may occur, resulting in unexpected loss. 

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