Surface-bound collagen 4 is significantly more stable than collagen 1

Collagen 1 (C1) is commonly used to improve biological responses to implant surfaces. Here the stability of C1 was compared with collagen 4 (C4) on a mixed macrodiol polyurethane, both adsorbed and covalently bound via acetaldehyde glow discharge polymerisation and reductive amination. Substrate specimens were incubated in solutions of C1 and C4. The strength of conjugation was tested by incubation in 8 M urea followed by enzyme linked immunosorbent assays to measure residual C1 and C4. The basal lamina protein, laminin-332 (L332) was superimposed via adsorption on C4-treated specimens. Keratinocytes were grown on untreated, C1-treated, C4-treated, and C4 + L332-treated specimens, followed by measurement of cell area, proliferation, and focal adhesion density. Adsorbed C4 was shown to be significantly more stable than C1 and covalent conjugation conferred even greater stability, with no degradation of C4 over twenty days in 8 M urea. Cell growth was similar for C1 and C4, with no additional benefit conferred by superimposition of L332. The greater resistance of C4 to degradation may be consequent to cysteine residues and disulphide bonds in its non-collagenous domains. The use of C4 on implants, rather than C1, may improve their long-term stability in tissues.