Physical and Biological Characterization of Ferromagnetic Fiber Networks: Effect of Fibrin Deposition on Short-Term In Vitro Responses of Human Osteoblasts

Abstract

Ferromagnetic fiber networks have the potential to deform in vivo imparting therapeutic levels of strain on ingrowing periprosthetic bone tissue. 444 Ferritic stainless steel provides a suitable material for this application due to its ability to support cultures of human osteoblasts (HObs) without eliciting undue inflammatory responses from monocytes in vitro. In the present article, a 444 fiber network, containing 17 vol% fibers, has been investigated. The network architecture was obtained by applying a skeletonization algorithm to three-dimensional tomographic reconstructions of the fiber networks. Elastic properties were measured using low-frequency vibration testing, providing globally averaged properties as opposed to mechanical methods that yield only local properties. The optimal region for transduction of strain to cells lies between the ferromagnetic fibers. However, cell attachment, at early time points, occurs primarily on fiber surfaces. Deposition of fibrin, a fibrous protein involved in acute inflammatory responses, can facilitate cell attachment within this optimal region at early time points. The current work compared physiological (3 and 5 g$L -1 ) and supraphysiological fibrinogen concentrations (10 g$L -1 ), using static in vitro seeding of HObs, to determine the effect of fibrin deposition on cell responses during the first week of cell culture. Early cell attachment within the interfiber spaces was observed in all fibrin-containing samples, supported by fibrin nanofibers. Fibrin deposition influenced the seeding, metabolic activity, and early stage differentiation of HObs cultured in the fibrin-containing fiber networks in a concentration-dependant manner. While initial cell attachment for networks with fibrin deposited from low physiological concentrations was similar to control samples without fibrin deposition, significantly higher HObs attached onto high physiological and supraphysiological concentrations. Despite higher cell numbers with supraphysiological concentrations, cell metabolic activities were similar for all fibrinogen concentrations. Further, cells cultured on supraphysiological concentrations exhibited lower cell differentiation as measured by alkaline phosphatase activity at early time points. Overall, the current study suggests that physiological fibrinogen concentrations would be more suitable than supraphysiological concentrations for supporting early cell activity in porous implant coatings.

The Elastic Behaviour of Sintered Metallic Fibre Networks: A Finite Element Study by Beam Theory

“…The dominantly in-plane fibre orientation of the network samples (see [ 36 , 73 ] for detailed analyses) influences the mechanical behaviour to a great extent when the remaining load cases i = 3 to 6 (see Fig 7 for sample 316L-20%-No.2) are obtained. It can be described as transversely isotropic.…”

A review of fibrin and fibrin composites for bone tissue engineering

“…18,19 Variations in experimental design, implantation site, and animal models as well as fibrinogen and thrombin concentrations are other parameters that make direct comparison of the research findings difficult. Moreover, to achieve the desired biological and/or physical properties for bone tissue engineering applications, fibrin must be reinforced, and there is a board range of nano-and other materials such as autogenous bone grafts, 20,21 allogenic bone grafts, 22,23 xenogeneic bone grafts, 24 metals, [25][26][27] ceramics, [28][29][30] …”

“…These improvements in cell behavior were attributed to the creation of a 3D fibrin network on Ti surfaces and/or the release of cytokines that were embedded within the platelets in the fibrin matrix. 115 Spear et al 25 showed that fibrin deposition on porous networks composed of 444 ferromagnetic stainless steel fibers significantly influenced infiltration of human osteoblasts within the scaffolds. For control samples without fibrin, cells with well-spread morphologies were observed only on the metallic fiber surfaces and junctions, while fibrin-containing samples showed cell attachment over and between the fibers.…”

“…For control samples without fibrin, cells with well-spread morphologies were observed only on the metallic fiber surfaces and junctions, while fibrin-containing samples showed cell attachment over and between the fibers. 25 In another work, BMP-2 containing fibrin gels were used to fill porous Ti implants and repair critical-sized segmental femoral bone defects in rats. It is important to note that bone regeneration did not occur in control groups wherein defects were filled with empty Ti or fibrin-filled scaffolds.…”

Mechanical bone growth stimulation by magnetic fibre networks obtained through a competent finite element technique

“…Nodes defining network medial axis location are referred to as network nodes in the following. Their total number per sample is known to increase for greater f 17 , 18 and is given in Table 1 for the three network samples.…”