The invention relates to the field of medicine and biology. A new product is described that is a sterile clear viscous preparation of a purified collagen dissolved in a 0.1 mM-20 mM aqueous acidic solution, the molecules of said collagen retaining the native triple helix structure in the solution at a temperature of +4° C. to +25° C. A concentrated solution of the collagen forms stable polymeric structures (hydrogels) under physiological conditions and can be used for manufacturing biomedical cell based products and three-dimensional tissue-engineered structures without using chemical and/or photochemical cross-linking. These structures can be heterogeneous density, including structures with a detail resolution of no larger than 0.3 mm, obtained by 3D printing, thus allowing incorporating living cells or cell aggregates used in medical practice in the structure. The disclosed collagen solution will be also useful as a material for forming hydrogels used for cell cultures. The invention also describes a process for the preparation of a sterile clear concentrated solution of biocompatible collagen, and possible uses thereof.
