TGF‐β1‐enhanced TCP‐coated sensate scaffolds can detect bone bonding

Abstract

Porous polybutylene terephthalate (PBT) scaffold systems were tested as orthopedic implants to determine whether these scaffolds could be used to detect strain transfer following bone growth into the scaffold. Three types of scaffold systems were tested: porous PBT scaffolds, porous PBT scaffolds with a thin β-tricalcium phosphate coating (LC-PBT), and porous PBT scaffolds with the TCP coating vacuum packed into the scaffold pores (VI-PBT). In addition, the effect of applying TGF-β1 to scaffolds as an enhancement was examined. The scaffolds were placed onto the femora of rats and left in vivo for 4 months. The amount of bone ingrowth and the strain transfer through various scaffolds was evaluated by using scanning electron microscopy, histology, histomorphometry, and cantilever bend testing. The VI-PBT scaffold showed the highest and most consistent degree of mechanical interaction between bone and scaffold, providing strain transfers of 68.5% (±20.6) and 79.2% (±8.7) of control scaffolds in tension and compression, respectively. The strain transfer through the VI-PBT scaffold decreased to 29.1% (±24.3) and 30.4% (±25.8) in tension and compression when used with TGF-β1. TGF-β1 enhancement increased the strain transfer through LC-PBT scaffolds in compression from 9.4% (±8.7) to 49.7% (±31.0). The significant changes in mechanical strain transfer through LC-PBT and VI-PBT scaffolds correlated with changes in bone ingrowth fraction, which was increased by 39.6% in LC-PBT scaffolds and was decreased 21.3% in VI-PBT scaffolds after TGF-β1 enhancement. Overall, the results indicate that strain transfer through TCP-coated PBT scaffolds correlate with bone ingrowth after implantation, making these instrumented scaffolds useful for monitoring bone growth by monitoring strain transfer.

An instrumented scaffold can monitor loading in the knee joint

“…As expected from previous studies,18 this scaffold system encourages bone growth around and into the pores of these scaffolds. The increased bone volume in the periscaffold region provides an indication that bone has anchored these scaffolds to the surrounding native tissue.…”

“…Polybutylene terephthalate (PBT) scaffolds were manufactured using an extrusion freeform fabrication rapid prototyping process, which has previously been reported 17. A grid pattern formed with PBT, which had been noted to develop good bone ingrowth in a previous study,18 was modified slightly so that strands within the scaffold were rotated 45° between layers (Figure 1). This pattern provided an interconnected porous structure, which was expected to insure rapid bone ingrowth in vivo .…”

“…Scaffolds were cleaned with ethanol and deionized water prior to coating the interior pores with β‐tricalcium phosphate (TCP) particles, using a published latexing procedure 18. This procedure utilized polycaprolactone (PCL) mixed with sodium dodecylsulfate (Fluka Chemika, Switzerland) in deionized water.…”

Implantable sensor technology: measuring bone and joint biomechanics of daily life in vivo

“…These measurements provided a useful record of how the process of integration of calcium phosphate ceramic-coated strain gages to bone and progression of spinal fusion affected early postoperative strains. While these results appear to be specific to the individual tested, this approach may be valuable as a more sensitive, quantitative, and biomechanically relevant method of monitoring fusion than serial radiographs [14]. …”

Trabecular scaffolds created using micro CT guided fused deposition modeling

“…Several investigators [4,50–52] have used fused deposition modeling to produce porous polymer scaffolds with interconnected pore structures. In this study, FDM was utilized to produce scaffolds made of polybutylene terephthalate (PBT), a semi-crystalline polyester that has been used in copolymer formulations in other biomedical applications [52] and which can be readily formed into a suitable filament for the modeler used. Hutmacher et al [4], Cao et al [50], and Darling and Sun [51] used fused deposition modeling to produce polycaprolactone (PCL) scaffolds.…”