Permeability of Three-Dimensional Fibrin Constructs Corresponds to Fibrinogen and Thrombin Concentrations

Abstract

Research in the last few years have focused on the use of three-dimensional (3D) fibrin construct to deliver growth factors and cells. Three-dimensional construct permeability and porosity are important aspects for proper nutrient uptake, gas exchange, and waste removal—factors that are critical for cell growth and survival. We have previously reported that the mechanical strength (stiffness) of 3D fibrin constructs is dependent on the fibrinogen and thrombin concentration. In this study, we established two new in vitro models to examine how fibrin composition affects the final 3D fibrin construct permeability and pore size; thereby, influencing the diffusivity of macromolecules throughout the network of fibrin fibrils. Flow measurements of both liquid and fluoresceinated-dextran microparticles are conducted to calculate the permeability and pore size of 3D fibrin constructs of different fibrinogen and thrombin concentrations. Similarly, the diffusivity of liquid and fluoresceinated-dextran microparticles through these 3D fibrin constructs are determined through diffusion models. Data from these studies show that the structural permeability and pore size of 3D fibrin constructs directly correlate to fibrinogen and thrombin concentration in the final 3D fibrin construct. More specifically, at a constant thrombin concentration of 2 or 5 μ/mL, pore size of the 3D fibrin constructs is dependent on fibrinogen if the concentration is 5 mg/mL and to a lesser extent if the concentration is 10–15 mg/mL. These findings suggest that fibrin's diffusive property can be manipulated to fabricate 3D constructs that are optimized for cellular growth, protein transport, and for the controlled delivery of bioactive molecules such as growth factors.

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“…Studies have shown how gelatin or elastin can be incorporated to decrease biodegradability and improve structural strength [35]. Additionally, growth factors and enzyme-specific peptides can also be incorporated to influence biodegradability and matrix permeability in a similar way to previously discussed natural scaffolds [36,39,40] (Figure 2). This ability to control and manipulate the architecture of synthetic scaffolds, as well as tune biodegradability and strength, has made synthetic scaffolds more favorable over natural ones in many applications [35,36,40] (Table 2).…”

“…A better solution comes in the form of other naturally-occurring matrices that can be created in the laboratory [36]. Fibrin scaffolds serve as a common favorable matrix for tissue engineering as they satisfy most of the key requirements [39]. Fibrin acts as a perfect natural matrix for cell proliferation that can be easily tuned by adjusting the concentrations of the thrombin and fibrinogen co-factors [39].…”

“…Fibrin scaffolds serve as a common favorable matrix for tissue engineering as they satisfy most of the key requirements [39]. Fibrin acts as a perfect natural matrix for cell proliferation that can be easily tuned by adjusting the concentrations of the thrombin and fibrinogen co-factors [39]. However, while natural scaffolds offer great versatility and biocompatibility, they are limited in structural strength and longevity [36].…”

Fibrin structural and diffusional analysis suggests that fibers are permeable to solute transport

“…Novel experimental setups have been developed to probe the diffusion of insulin-like growth factor I (IGF-I) and ribonuclease through fibrin hydrogels of low density (2.25 mg/mL) and low volume fraction (0.27 vol% of a dry hydrogel), yielding diffusivity values comparable to that in water and pointing to a negligible influence of the open, fibrous network [41]. Moreover, variations in fibrinogen (5-20 mg/mL) and thrombin (2-20 U/mL) concentrations have been shown to affect the permeability of fibrin hydrogels and the release of dextran solutes (3 and 70 kDa) [42]. However, to the best of our knowledge, a quantitative analysis assessing the effect of specific fibrin hydrogel architectures on solute diffusivity over a wide range of pore sizes has not been tested so far.…”

Home-Grown Kidneys: Challenges and Mechanisms Behind Tissue Engineering for the Treatment of Chronic Kidney Disease

“…36 Fibrin scaffolds serve as a common favorable matrix for tissue engineering as they satisfy most of the key requirements. 39 Fibrin acts as a perfect natural matrix for cell proliferation that can be easily tuned by adjusting the concentrations of the thrombin and fibrinogen co-factors. 39 However, while natural scaffolds offer great versatility and biocompatibility, they are limited in structural strength and longevity.…”