Figure 2.

Stabilized collagen-based mats. (A to C) The compression process. (A-Left) Collagen type I was suspended in acetic acid at pH 3.6. The gel-like material (g) was poured into a Petri dish and neutralized. (A-Middle) The gel pad (g) was layered onto a filter paper stack (fp) and overlayed with a nylon mesh filter (mf). (A-Right) The gel-like material was pressed with a weight (w) to an ~1 mm thick collagen mat, the sequential arrangement of the nylon mesh filter (mf) - gel pad (g) - filter paper stack (fp) is only hinted. (B) Stainless steel mat press. Into the cavities the gel-like collagen material was filled in and placed onto a filter paper. The upper side was covered with the mesh filter and a weight of 80 g was put on the punch (p). (C) The pressed 1 mm thick collagen mat (m). (D to H) Change of morphology of the collagen fibrils during the processing phases; SEM. (D) Poorly-formed collagen subfibrils at pH 3.6. (E) Transformation of the subfibrils to mature D-banded collagen fibers at pH 6 to 9 in “Ma/Col”. (F) Pressed collagen fibers in the 1 mm thick mats. (G and H) Surface of “Ma/Col-Ca-polyP-NP” with nanoparticles (NP) that are concentrated on the ridges of the D-banded collagen fibers. (H) Surface appearance of “Ma/Col-Ca-polyP-NP” mats with their NP, which are embedded into the coacervate phase of polyP (Coa).