A protein aqueous solution for use in the treatment of the human or animal body by promoting granulation tissue formation or epithelization, the protein aqueous solution being in the form of a gel and comprising a material for tissue regeneration comprising a synthetic protein polymer, wherein the synthetic protein polymer comprises at least one polypeptide chain and/or at least one polypeptide chain (Y'), and has a hydrophobic scale of 0.2 to 1.2, the total number of the polypeptide chains and (Y') in the synthetic protein polymer is 1 to 100, the polypeptide chain consists of 2 to 200 consecutive units of one amino acid sequence selected from VPGVG, GVGVP, GPP, GAP, and GAHGPAGPK the polypeptide chain (Y') is a polypeptide chain wherein 1 to 100 amino acid residues in the polypeptide chain are independently replaced with a lysine or arginine residue, wherein the hydrophobic scale of the synthetic protein polymer is defined by the following formula: Hydrophobic scale = ∑ M α × N α / M T wherein M α = the number of residues of each amino acid in the synthetic protein polymer molecule; N α = the hydrophobic scale of each amino acid; M T = the total number of amino acid residues in the synthetic protein polymer molecule; wherein the hydrophobic scales of the respective amino acid residues are as follows: A (alanine): 1.8 R (arginine): -4.5 N (asparagine): -3.5 D (aspartic acid): -3.5 C (cysteine): 2.5 Q (glutamine): -3.5 E (glutamic acid): -3.5 G (glycine): -0.4 H (histidine): -3.2 I (isoleucine): 4.5 L (leucine): 3.8 K (lysine): -3.9 M (methionine): 1.9 F (phenylalanine): 2.8 P (proline): -1.6 S (serine): -0.8 T (threonine): -0.7 W (tryptophan): -0.9 Y (tyrosine): -1.3 V (valine): 4.2. a material for tissue regeneration comprising a synthetic protein polymer, wherein the synthetic protein polymer comprises at least one polypeptide chain and/or at least one polypeptide chain (Y'), and has a hydrophobic scale of 0.2 to 1.2, the total number of the polypeptide chains and (Y') in the synthetic protein polymer is 1 to 100, the polypeptide chain consists of 2 to 200 consecutive units of one amino acid sequence selected from VPGVG, GVGVP, GPP, GAP, and GAHGPAGPK the polypeptide chain (Y') is a polypeptide chain wherein 1 to 100 amino acid residues in the polypeptide chain are independently replaced with a lysine or arginine residue, wherein the hydrophobic scale of the synthetic protein polymer is defined by the following formula: Hydrophobic scale = ∑ M α × N α / M T wherein M α = the number of residues of each amino acid in the synthetic protein polymer molecule; N α = the hydrophobic scale of each amino acid; M T = the total number of amino acid residues in the synthetic protein polymer molecule; M α = the number of residues of each amino acid in the synthetic protein polymer molecule; N α = the hydrophobic scale of each amino acid; M T = the total number of amino acid residues in the synthetic protein polymer molecule; A (alanine): 1.8 R (arginine): -4.5 N (asparagine): -3.5 D (aspartic acid): -3.5 C (cysteine): 2.5 Q (glutamine): -3.5 E (glutamic acid): -3.5 G (glycine): -0.4 H (histidine): -3.2 I (isoleucine): 4.5 L (leucine): 3.8 K (lysine): -3.9 M (methionine): 1.9 F (phenylalanine): 2.8 P (proline): -1.6 S (serine): -0.8 T (threonine): -0.7 W (tryptophan): -0.9 Y (tyrosine): -1.3 V (valine): 4.2.