Tricalcium phosphate and glutaraldehyde crosslinked gelatin incorporating bone morphogenetic protein—A viable scaffold for bone tissue engineering

Abstract

Bone defects caused by various etiologies must be filled with suitable substances to promote bone repair. Autogenous iliac crest graft is most frequently used, but is often associated with morbidities. Several bone graft substitutes have been developed to provide osteoconductive matrices as well as to enhance osteoinductivity. A tricalcium phosphate and glutaraldehyde crosslinked gelatin (GTG) scaffold, incorporated with bone morphogenetic proteins (BMPs), was developed to provide an alternative mean of bone tissue engineering. This study investigated differences between GTG and BMP-4 immobilized GTG (GTG-BMP) scaffolds on neonatal rat calvaria osteoblast activities. The GTG scaffold possessed an average pore size of 200 microm and a porosity of 75%. HE staining revealed uniform cell distribution throughout the scaffold 24 h post cell seeding. Alkaline phosphatase (ALP) activity of the GTG samples increased initially and then stabilized at 3 weeks postseeding. ALP activity of the GTG-BMP samples was similar to that of the GTG samples in the second and third weeks, but it continued increasing and became significantly greater than that of the GTG samples by the fourth week. Gla-type osteocalcin (Gla-OC) activity of the GTG-BMP samples was initially lower, but also became significantly greater than that of the GTG samples by the fourth week. An HE stain revealed greater numbers of attached cells and a richer matrix deposits in the GTG-BMP samples. A von Kossa stain showed larger mineralizing nodules, in greater numbers, after 4 weeks of in vitro cultivation. These findings suggest that the GTG scaffold provides an excellent porous structure, conductive to greater cell attachment and osteoblast differentiation, and that utility can be significantly enhanced by the inclusion of BMPs. A GTG-BMP scaffold holds promise as a superior bioactive material for bone tissue engineering.

Calcium orthophosphate-based biocomposites and hybrid biomaterials

“…An in vitro study with primary rat calvarial osteoblasts showed an increased cellular activity in the BMP-loaded samples [392]. Other researchers investigated BMP-2-loaded porous b-TCP/gelatin biocomposites (porosity 95%, average pore size 180-200 lm) [402] and confirmed the precious study.…”

“…Besides, they are faster resorbed in vivo. 5 Therefore, these calcium orthophosphates were used instead of HA to prepare completely biodegradable biocomposites [376][377][378][379][380][381][382][383][384][385][386][387][388][389][390][391][392][393][394]. For example, a biodegradable and osteoconductive biocomposite made of b-TCP particles and gelatin was proposed [385].…”

“…Another research group prepared biocomposites of crosslinked gelatin with b-TCP; they found both a good biocompatibility and bone formation upon subcutaneous implantation in rats [387]. Yang et al [392] extended this to porous (porosity about 75%) b-TCP/ gelatin biocomposites those also contained BMP-4. Besides, cell-compatible and possessive some osteoinductive properties porous b-TCP/alginate-gelatin hybrid scaffolds were prepared and successfully tested in vitro [389].…”

“…Thermogravimetric and infrared analysis demonstrated that the polymers were chemically bonded to the HA particles through the isocyanate groups, making it a suitable approach to improve the adhesion [910]. Other researchers used glutaraldehyde as a crosslinked reagent in various calcium orthophosphate-based biocomposites [388,392,500,502,503,520,525,585,621,646,649,917]. The interfacial bonding between calcium orthophosphates and other components might be induced by using various coupling agents and surface modifiers, such as silanes [192,234,337,540,[918][919][920][921][922][923], zirconates [225,337,339,914,924], titanates [225,337,924], phosphoric acid [543], alkaline pretreatment [722,725], polyacids [115,116,234], and other chemicals.…”

Biocomposites and hybrid biomaterials based on calcium orthophosphates

“…Another research group prepared biocomposites of cross-linked gelatin with β-TCP, and both a good biocompatibility and bone formation upon subcutaneous implantation in rats were found. 469 Yang et al 474 extended this to porous (porosity ~75%) β-TCP/gelatin biocomposites that also contained BMP-4. Porous β-TCP/ alginate-gelatin hybrid scaffolds that were cell-compatible and possessing some osteoinductive properties were aso prepared and successfully tested in vitro.…”