Speaker
Description
Hydrogels derived from extracellular matrices (ECM-gels) have been described with promising features to promote tissue regeneration, since they preserve several components of native tissues. However, their weak mechanical properties impair ECM-gels use in load-bearing applications. Previously, we have shown that the incorporation of oxidized forms of graphene, one of the strongest materials in the world, in decellularized arteries, improves their mechanical and biological properties [1]. Herein, we propose the incorporation of graphene-based materials (GBMs) in ECM-gels to surpass their weak mechanical properties, allowing their future use as self-standing scaffolds for different load-bearing tissue engineering applications.
GBMs with different lateral sizes were either purchased or produced by modified Hummers’ method and characterized by TEM, XPS, XRD, and DLS [2]. Human placenta chorion was isolated and decellularized by a freeze-thawing cycle, followed by an osmotic shock and treatments with triton and DNAse. Materials were sterilized and ECM pre-gels were obtained by digesting the decellularized tissues with pepsin. Decellularization efficiency was evaluated by quantified the DNA amount. Different amounts of GBMs (1-4% v/v) powders (freeze-dried) or aqueous dispersions were incorporated in ECM and mixed(ECM/GBMs pre-gels). Pre-gels were put into a mold and left overnight at 37ºC to promote gelation. Surface topography of ECM/GBMs-gels was evaluated by SEM, and rheological properties were evaluated using single frequency strain-controlled tests, with a 1% strain, 1 Hz frequency, and 5 min testing time. Adhesion of Staphylococcus aureus was assessed by SEM and the coagulation time after contact with recalcified human plasma evaluated.
After decellularization ECM-Gels exhibit 2.2% of remaining DNA comparing with original tissue. Oxidized forms of GBMs dispersed better on ECM gels than non-oxidized. Thus, graphene oxide (GO)was chosen to perform the following characterization steps. SEM images showed that the GO can intercalate ECM-gels collagen fibers. Regarding the rheological properties, a higher increase in complex modulus was observed when GO was incorporated in ECM as a dispersion compared with as a powder.This could be explained by the inability of GO to re-disperse in ECM upon the freeze-drying step. For both conditions(powders/dispersion), ECM complex modulus increased exponentially within the amount of GO. For the highest tested concentration of GO dispersion(4% v/v), a remarkable increase of 21768% in complex modulus was observed. Even though GO has been described as antimicrobial and/or being able to decrease bacterial adhesion, our results showed that the number of adherent bacteria is similar in ECM and ECM/GO.This may be explained because GO is not exposed on the surface, as observed for PU/GBMs [3].Incorporation of GO in ECM decreased the clotting time of recalcified Human plasma, suggesting that the ECM-gels are more pro-coagulant.
Overall, GO has an effective role in improving ECM mechanical properties, which is a step forward to enable ECM gels in load-bearing applications.
Acknowledgments:
FCT/FEDER: PD/BD/114156/2016 and PTDC/CTM-COM/32431/2017.
References:
[1] A.T. Pereira, K.H. Schneider, P.C. Henriques, et al., Acs Applied Materials & Interfaces, 13 (2021) 32662-32672
[2] A.T. Pereira, P.C. Henriques, K.H. Schneider, et al., Biomaterials Science, (2021)
[3] I. Borges, P.C. Henriques, R.N. Gomes, et al., Nanomaterials (Basel), 10 (2020)
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