A biomatrix layer comprising, consisting essentially of or consisting of • a negatively charged polymer at a concentration in the range of 0.1 μM to 1,000 μM, wherein said NCP is represented by a sulfated oligosaccharide or hyaluronic acid; and • a peptide - polyethylene glycol - conjugate according to general formula: PEG-CW-spacer-R 1 -spacer- n; wherein - said spacer is absent or is a dipeptide, tripeptide or tetrapeptide, wherein said dipeptide, tripeptide or tetrapeptide consists of glycine, aminopropanoic acid, aminobutyric acid, aminopentanoic acid, aminohexanoic acid, aminoheptanoic acid, aminooctanoic acid and 3-aminoacrylic acid or combinations thereof; - CW is absent or is the dipeptide consisting of the amino acids cysteine and tryptophan; - B is lysine or arginine, X is alanine and n is an integer selected from 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20; - R 1 represents a bio-functional peptide, which may be absent or is a peptide comprising 5 to 30 amino acids; - PEG is comprised at a concentration in the range of 0.1 μM to 1,000 μM; - R 1, if present, is comprised at a concentration in the range of 0.1 μM to 4,000 μM; - n is comprised at a concentration in the range of 0.4 μM to 4,000 μM. • a negatively charged polymer at a concentration in the range of 0.1 μM to 1,000 μM, wherein said NCP is represented by a sulfated oligosaccharide or hyaluronic acid; and • a peptide - polyethylene glycol - conjugate according to general formula: PEG-CW-spacer-R 1 -spacer- n; wherein - said spacer is absent or is a dipeptide, tripeptide or tetrapeptide, wherein said dipeptide, tripeptide or tetrapeptide consists of glycine, aminopropanoic acid, aminobutyric acid, aminopentanoic acid, aminohexanoic acid, aminoheptanoic acid, aminooctanoic acid and 3-aminoacrylic acid or combinations thereof; - CW is absent or is the dipeptide consisting of the amino acids cysteine and tryptophan; - B is lysine or arginine, X is alanine and n is an integer selected from 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20; - R 1 represents a bio-functional peptide, which may be absent or is a peptide comprising 5 to 30 amino acids; - PEG is comprised at a concentration in the range of 0.1 μM to 1,000 μM; - R 1, if present, is comprised at a concentration in the range of 0.1 μM to 4,000 μM; - n is comprised at a concentration in the range of 0.4 μM to 4,000 μM. - said spacer is absent or is a dipeptide, tripeptide or tetrapeptide, wherein said dipeptide, tripeptide or tetrapeptide consists of glycine, aminopropanoic acid, aminobutyric acid, aminopentanoic acid, aminohexanoic acid, aminoheptanoic acid, aminooctanoic acid and 3-aminoacrylic acid or combinations thereof; - CW is absent or is the dipeptide consisting of the amino acids cysteine and tryptophan; - B is lysine or arginine, X is alanine and n is an integer selected from 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20; - R 1 represents a bio-functional peptide, which may be absent or is a peptide comprising 5 to 30 amino acids; - PEG is comprised at a concentration in the range of 0.1 μM to 1,000 μM; - R 1, if present, is comprised at a concentration in the range of 0.1 μM to 4,000 μM; - n is comprised at a concentration in the range of 0.4 μM to 4,000 μM.