  This article presents a novel computational model to study the selective
filtering of biological hydrogels due to the surface charge and size of
diffusing particles. It is the first model that includes the random 3D fiber
orientation and connectivity of the biopolymer network and that accounts for
elastic deformations of the fibers by means of beam theory. As a key component
of the model, novel formulations are proposed both for the electrostatic and
repulsive steric interactions between a spherical particle and a beam. In
addition to providing a thorough validation of the model, the presented
computational studies yield new insights into the underlying mechanisms of
hindered particle mobility, especially regarding the influence of the
aforementioned aspects that are unique to this model. It is found that the
precise distribution of fiber and thus charge agglomerations in the network
have a crucial influence on the mobility of oppositely charged particles and
gives rise to distinct motion patterns. Considering the high practical
significance for instance with respect to targeted drug release or infection
defense, the provided proof of concept motivates further advances of the model
toward a truly predictive computational tool that allows a case- and
patient-specific assessment for real (biological) systems.
