Structural hierarchy of biomimetic materials for tissue engineered vascular and orthopedic grafts

Abstract

Gelatine gels and gelatine/elastin gels have been prepared to be used in tissue engineered vascular grafts. Optical microscopy and AFM revealed that the gelatine formed nanofibrils as in soft collagen tissues. The gelatine/elastin gels were nanocomposites with flat elastin nanodomains embedded in the gelatine matrix mimicking the structure of the tunica media in arteries. Gelatine/"hydroxyapatite" nanocomposites were prepared with the in situ production of "hydroxyapatite" in solution. AFM revealed "hydroxyapatite" solid nanoparticles of about 20 nm size embedded in the gelatine matrix which formed a hierarchical structure similar to that of the collagen matrix in bone. The application of a magnetic field of 9.4 T resulted in the elongation and orientation of gelatine particles and orientation of gelatine microfibrils in a direction perpendicular to that of the magnetic field.3

Electrospinning of Nanocomposite Fibrillar Tubular and Flat Scaffolds with Controlled Fiber Orientation

“…After electrospinning was completed, the fibrillar structures were left under vacuum at room temperature for 24 hours for the evaporation and removal of TFE. The product was then placed in a sealed dessicator with 15 ml 25% glutaraldehyde in a Petri dish for 3 days at room temperature to effect crosslinking of gelatine, so that the fibrillar structure would not dissolve in an aqueous medium if used as scaffold for biomedical applications [15][16]. The crosslinked products were air dried in a fume cupboard for 3 hours for the removal of glutaraldehyde.…”

“…It is most important that the microstructure of the scaffolds mimics that of tissues so that cells in the organism are guided to adhere and proliferate by the appropriate microstructure according to which they have been programmed to respond. Biomimetic architectures include a tailored structural hierarchy [16], a certain fibre orientation depending on organ [16], and a certain pore size so that large human cells, such as osteoblasts, may be able to migrate and are well distributed throughout the structure during tissue engineering in vitro. Gelatine is a key biomaterial used by the authors of this paper, as it is a low cost widely available material based on collagen, the main component of soft tissues and the matrix of bone.…”

“…Gelatine is a key biomaterial used by the authors of this paper, as it is a low cost widely available material based on collagen, the main component of soft tissues and the matrix of bone. Gelatine-elastin nanocomposite gels have been characterised [15,16] and proved to have similar properties as soft tissues, being good candidates for vascular grafts.…”

“…Studies so far [15][16]36] have yielded gelatine nanocomposite gels, which proved highly bioactive in the proliferation of rat smooth muscle cells [36] but less successful in the proliferation of human osteoblasts, mainly because these large cells were not able to migrate needing a porous scaffold. Electrospun PLLA/HA scaffolds of a fibre diameter of about 5 m have been used successfully for the proliferation of osteoblasts [28] where the presence of hydroxyapatite nanoparticles has been seen beneficial for the adhesion of osteoblasts in experiments in rabbits [28].…”

“…Various techniques have been used in the past for the fabrication of porous scaffolds, such as drawing [26], phase separation [31], template synthesis [7], self-assembly [37], particulate leaching [12], foaming [24], freeze-drying [23], and electrospinning [4,20,34,39]. Electrospinning has been used for the fabrication of the fibrous scaffolds in this study, followed by crosslinking of gelatine in glutaldehyde solution [15][16]36].…”