Micro-to-Nano Biomechanical Modeling for Assisted Biological Cell Injection

Cell manipulation is a prevalent process in the field of molecular biology. This process plays an important role in intracytoplasmic sperm injection (ICSI), pronuclei deoxyribonucleic acid (DNA) injection, therapeutic and regenerative medicine, and other biomedical areas. ICSI has progressively replaced all other micro-injection procedures for overcoming intractable male-factor infertility and has emerged in a relatively short time as a routine procedure for many in-vitro procedures. Nevertheless, injections are currently performed manually and technicians are required to be skillful enough to not destruct the cell structure of the ovum during the ICSI process. To facilitate training of biological cell injection operations, we are developing an interactive virtual environment to simulate needle insertion into biological cells. This paper presents methodologies for dynamic modeling, visual/haptic display and model validation of cell injection. We first investigate the challenging issues in the modeling of the biomechanical properties of living cells. We propose two dynamic models to simulate cell deformation and puncture. The first approach is based on the assumptions that the mechanical response of living cells is mainly determined by the cytoskeleton and that the cytoskeleton is organized as a tensegrity structure including microfilaments, microtubules and intermediate filaments. Equivalent microtubules struts are represented with a linear mass-tensor finite element model and equivalent microfilaments and intermediate filaments with viscoelastic Kelvin-Voigt elements. The second modeling method assumes the overall cell as an homogeneous hyperelastic model (St-Venant-Kirchhoff). Both graphic and haptic rendering are provided in real-time to the operator through a 3D virtual environment. Simulated responses are compared to experimental data to show the effectiveness of the proposed physically-based model.