Unique Collagen Fibers for Biomedical Applications

Abstract

The challenge to develop grafts for tissue regeneration lies in the need to obtain a scaffold that will promote cell growth in order to form new tissue at a trauma-damaged site. Scaffolds also need to provide compatible mechanical properties that will support the new tissue and facilitate the desired physiological activity. Here, we used natural materials to develop a bio-composite made of unique collagen embedded in an alginate hydrogel material. The collagen fibers used to create the building blocks exhibited a unique hyper-elastic behavior similar to that of natural human tissue. The prominent mechanical properties, along with the support of cell adhesion affects cell shape and supports their proliferation, consequently facilitating the formation of a new tissue-like structure. The current study elaborates on these unique collagen fibers, focusing on their structure and biocompatibility, in an in vitro model. The findings suggest it as a highly appropriate material for biomedical applications. The promising in vitro results indicate that the distinctive collagen fibers could serve as a scaffold that can be adapted for tissue regeneration, in support of healing processes, along with maintaining tissue mechanical properties for the new regenerate tissue formation.

Keywords: marine biomaterials; medical device; scaffold; soft corals; tissue regeneration.

Figure 1

(A) Macro image of Sarcophyton and (B) its torn-apart polypary, revealing collagen fibers pulling from these sections; (C) Auto-fluorescence of collagen fibers observed by fluorescence microscopy; (D) E-SEM micrographs of collagen fibers that feature a coiled structure.

Figure 2

Bio-composite fabrication and mechanical behavior. (A) Sarcophyton collagen fibers aligned on a metal frame; (B) 3% Alginate hydrogel; (C) Fabricated uniaxial bio-composite; (D) Uniaxial bio-composite under tensile test; (E) Mechanical behavior of collagen fibers, alginate matrix, and uniaxial bio-composite. The toe, heel, and linear regions are demonstrated on the Sarcophyton collagen fiber stress-strain curve.

Figure 3

Live imaging and quantification for cells seeded on 3% hydrogel alginate (A) on Sarcophyton collagen fibers; (B) 24 h after seeding cells. Images are at ×100 magnification. (C) Cell circularity was analyzed by ImageJ software. Bio-composite was made of collagen fibers embedded in 3% hydrogel alginate. (D,E) Phase microscopic images of cells seeded on the bio-composite in a tissue culture dish (F), were observed to have a mixed morphology of cells: elongated cells are visualized on the collagen fibers along their orientation. On alginate the cells maintained a rounded shape. (G,H) Cells grown on collagen fibers up to nine weeks formed a tissue-like structure (collagen fibers are shown in green and cell nuclei are DAPI-stained blue). (I) Model of substrate stiffness and cells’ morphology. Cells on the fibers are attached and become elongated with the substrate orientation, while cells on the alginate are rounded as a result of no adhesion and the pressure applied by the alginate matrix.

Figure 4

Illustration of potential use of collagen fibers embedded in a hydrogel bio-composite for medical devices with adjusted mechanical properties that provide support and allow motion and flexibility of the tissue under repair.