Well plates

Primary human dermal fibroblasts were maintained in Dulbecco’s Modified Eagle Medium (DMEM) cell culture medium supplemented with 10% fetal bovine serum (FBS) and 1% penicillin/streptomycin at 37 °C, 5% CO₂ and 95% humidity (standard cell culture conditions). Cell culture medium and supplements were all purchased from Gibco, Invitrogen, Thermo Fisher Scientific Inc, Dreieich, Germany.
For all experiments, the 3D collagen matrices were placed into four well-plates (Thermo Fisher Scientific Inc, Dreieich, Germany). 1 × 10⁵ fibroblast cells were seeded onto 3D collagen matrices and kept at standard cell culture conditions for 2 h to allow for cell attachment. Afterwards, the cell culture medium was removed and biocompatible microvessels were placed onto the well plate, as previously described [37 (link)]. Subsequently, fresh cell culture medium was added into the microvessel. For fibroblast differentiation, cell culture medium was supplemented with 10 ng/mL TGF- β1(Biolegend, San Diego, CA, USA) [21 (link)]. Cells were then cultured for 3 days at 1g or sµG conditions in an incubator at standard cell culture conditions.

Streptavidin-coated ferromagnetic particles (permanent magnetic particles, FMPs, 2–2.9 µm) and streptavidin-coated superparamagnetic particles (no magnetism, SMNPs, 0.1–0.39 µm) were purchased from Spherotech, Lase Forest, IL, USA. SMNPs have no net magnetism at room temperature due to the Néel relaxation time. When there is an absence of an external magnetic field, the net magnetization would be zero. This would be referred to as the “off” state. The sulfo-NHS-biotin (N-Hydroxysulfosuccinimidobiotin) labeling kit, Lipofectamine 2000, Opti-MEM, Fura-2-AM, Pluronic F-127, well plates, and glassware were purchased from Thermo Fisher Scientific (Waltham, MA, USA). All reagents were dissolved in a calcium imaging solution (CIS). The CIS was prepared by mixing 125 mM NaCl, 2 mM MgCl₂, 4.5 mM KCl, 10 mM glucose, 20 mM HEPES, and 2 mM CaCl₂ adjusted to pH 7.4. The CIS was used for all Ca²⁺ imaging experiments.

Cyclic olefin copolymer Topas microscopy slides were obtained from ChipShop, Germany (10-0678-0347-2.0-02). Polycarbonate sheets were obtained from Polycarbo, Russia. The human hepatoma Huh7 cell line (ATCC) was kindly provided by Dr. Mukhatayev, Nazarbayev University, Kazakhstan. Human Albumin ELISA kit (EHALB), Urea Nitrogen Colorimetric detection kit (EIABUN), collagen-coated flasks, and well plates were purchased from ThermoFisher Scientific (Waltham, MA, USA). All other materials and kits were purchased from Sigma-Aldrich (Hamburg, Germany) unless mentioned otherwise.