Hyaluronic acid and poly(ethylene glycol) derivatives attract considerable attention as precursors for tissue engineering. In this paper photocuring of biocompatible hyaluronic acid-glycidyl methacrylate (HAGM) and poly(ethylene glycol) diacrylate (PEG-DA) aqueous solutions, using flavin mononucleotide (FMN) as an endogenous photoinitiator, has been studied. The required threshold concentrations of initial macromolecules in water for the strengthening (increase of the Young’s modulus) of irradiated hydrogels have been determined as 57 wt\% for 2D cross-linking of PEG-DA compositions and 16 wt\% for 3D cross-linking of HAGM compositions. These concentrations are in a good agreement with correspondent values derived from the percolation theory for 2D and 3D lattices. It has been demonstrated that cross-linking proceeds predominantly by the radical mechanism and does not require co-initiators. Hydrogel scaffolds with specific and predetermined architectonics for biocompatibility and biomechanical studies have been produced by photopolymerizable micromolding.