This work presents a computational model to study release profile of proteins grafted on scaffolds surfaces. As a case study we investigated the behaviour of ICOS-Fc, a bioactive protein able to rebalance the osteoblasts and osteoclasts activities , bound to a polyester blend. Then, a three-dimensional (3D) model was implemented to evaluate the release and diffusion of ICOS-Fc, from the pores of a complex scaffold towards an osteoporotic fracture.
The protein release profile was simulated in COMSOL Multiphysics® software implementing the “Transport of Diluted Species” equations. A first simplified model was implemented to study the protein release from the surface of cylindrical pellet incubated in a PBS medium, in order to identify the process parameters. The protein was assumed completely grafted and homogeneously distributed on the pellet surface. Thus, considering the axial-symmetry of the geometry and the problem conditions, a 2D axisymmetric model and a time dependent study were selected to assess the protein release over time. A parametric sweep was added to evaluate the release profile for different diffusion constants(10-9 - 10-8 - 10-7 m2/s ).An initial concentration of 0.2 mol/m3 was set on the layer where the protein is grafted, while 0 mol/m3 on the medium domain. On the basis of the parameters obtained from the simplified study, a 3D problem was modelled for the protein release grafted from a 3D-printed complex scaffold, and its diffusion from the pores towards a fracture. An initial concentration of 0.2 mol/m3 was set on the scaffold internal surface where the protein is grafted. A flux condition was set on the delivering pores to simulate the diffusion of the molecule. In addition, the protein release profile was studied changing the scaffold porous architecture. A time dependent study was chosen to evaluate the release after 7 days.
The amount of protein released from the scaffold, with all and four pores delivering pores over time, was computed. Comparing the release profile of the two cases, in the first one the protein is almost all released after 4 days. Instead, with only four pores delivering, the protein is not all delivered after 7 days. Thus, the second condition is preferred for a controllable release of the protein.
To sum up, the presented study showed a computational model for evaluating the ICOS-Fc protein release over time. With the process parameters studied in the simplified study, the model can be used to optimize the scaffold porous architecture in order to have a controllable release of the protein (e.g., all or only four pores delivering).
This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No814410.
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