Assessment of the usefulness of bacterial cellulose produced by Gluconacetobacter xylinus E25 as a new biological implant.

Bionanocellulose (BNC) is a clear polymer produced by the bacterium Gluconacetobacter xylinus. In our current study, "Research on the use of bacterial nanocellulose (BNC) in regenerative medicine as a function of the biological implants in cardiac and vascular surgery", we carried out material analysis, biochemical analysis, in vitro tests and in vivo animal model testing. In stage 1 of the project, we carried out physical and biological tests of BNC. This allowed us to modify subsequent samples of bacterial bionanocellulose. Finally, we obtained a sample that was accepted for testing on an animal model. That sample we define BNC1. Patches of BNC1 were then implanted into pigs' vessel walls. During the surgical procedures, we evaluated the technical aspects of sewing in the bioimplant, paying special attention to bleeding control and tightness of the suture line and the BNC1 bioimplant itself. We carried out studies evaluating the reaction of an animal body to an implantation of BNC1 into the circulatory system, including the general and local inflammatory reaction to the bioimplant. These studies allowed us to document the potential usefulness of BNC as a biological implant of the circulatory system and allowed for additional modifications of the BNC to improve the properties of this new implantable biological material.

In vitro hemocompatibility on thin ceramic and hydrogel films deposited on polymer substrate performed in arterial flow conditions.

Hydrogel coatings were stabilized by titanium carbonitride a-C:H:Ti:N buffer layers deposited directly onto the polyurethane (PU) substrate beneath a final hydrogel coating. Coatings of a-C:H:Ti:N were deposited using a hybrid method of pulsed laser deposition (PLD) and magnetron sputtering (MS) under high vacuum conditions. The influence of the buffer a-C:H:Ti:N layer on the hydrogel coating was analysed by means of a multi-scale microstructure study. Mechanical tests were performed at an indentation load of 5 mN using Berkovich indenter geometry. Haemocompatible analyses were performed in vitro using a blood flow simulator. The blood-material interaction was analysed under dynamic conditions. The coating fabrication procedure improved the coating stability due to the deposition of the amorphous titanium carbonitride buffer layer.

Thrombogenicity and biocompatibility studies of reduced graphene oxide modified acellular pulmonary valve tissue.

Current strategies in tissue engineering seek to obtain a functional tissue analogue by either seeding acellular scaffolds with cells ex vivo or repopulating them with cells in vivo, after implantation in patients. To function properly, the scaffold should be non-thrombogenic and biocompatible. Especially for the case of in vivo cell repopulation, the scaffold should be prepared in a manner that protects the tissue against platelet activation and adhesion. Anti-thrombogenicity can be achieved by chemical or physical surface modification. The aim of our study was to evaluate the platelet activation and thrombogenic properties of an acellular tissue scaffold that was surface modified with reduced graphene oxide (rGO). Graphene oxide was prepared by a modified Hummers method. For the study, an acellular pulmonary valve conduit modified with rGO was used. The rGO modified tissue samples were subjected to in vitro testing through interaction with whole blood under simulated laminar flow conditions. The following cellular receptors were then analysed: CD42a, CD42b, CD41a, CD40, CD65P and PAC-1. In parallel, the adhesion of platelets (CD62P positive), leukocytes (CD45 positive) and platelet-leukocyte aggregates (CD62P/CD45 positive) on the modified surface was evaluated. As a reference, non-coated acellular tissue, Poly-l lysine and fibronectin coated tissue were also tested. The rGO surface was also analysed for biocompatibility by performing a cytotoxicity test, TUNEL assay and Cell Cycle analysis. There was no significant difference in platelet activation and adhesion between the study groups. The only significant difference was observed for the PAC-1 receptor between Poly-l lysine group and rGO and the percentage of PAC-1 positive cells was 6% and 18% respectively. The average number of activated platelets (CD62P) in the field of view was 1, while the average number of leukocytes in the field of view was 3. No adherent platelet-leukocyte aggregates were observed. There were no significant differences in the DNA fragmentation. No significant effect of rGO on the amount of cells in different phases of the cell cycle was observed. Cytotoxicity indicates that the rGO can damage cells in direct contact but have no effect on the viability of fibroblasts in indirect contact.