The aim of this work is to develop an efficient synthetic approach to hexahedral cage-like organic–inorganic siloxane core biohybrids containing side chains fully functionalized by methacrylate groups derived from monomers such as 2-hydroxyethyl methacrylate (HEMA) or ethylene glycol dimethacrylate (EGDMA). The resulting hybrids were characterized using spectroscopic methods (FTIR, 1H, 13C, 29Si NMR), thermogravimetric and DSC analyses, and high resolution mass spectrometry (HR-MS). The obtained compounds, after polycondensation/polymerization reactions, were utilized in constructing 3D macroporous scaffolds which were examined using a scanning electron microscope (SEM). Covalent networks created by fully functionalized cubic spherosilicates can mimic certain biomaterials and constitute sophisticated, highly organized building blocks of complex systems.