Banca de QUALIFICAÇÃO: AUGUSTO MONTEIRO DE SOUZA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : AUGUSTO MONTEIRO DE SOUZA
DATE: 05/10/2022
TIME: 14:00
LOCAL: https://meet.google.com/gbw-jhvh-vjn
TITLE:

BIOLOGICAL STUDIES WITH MODIFIED HYDROXYAPATITE FOR APPLICATION IN BONE REGENERATION

KEY WORDS:

Cytotoxicity; eenotoxicity; embryotoxicity; modified hydroxyapatite.

PAGES: 92
BIG AREA: Ciências Biológicas
AREA: Genética
SUMMARY:

Hydroxyapatite (HA) is a biomaterial widely used in clinical and pharmaceutical applications. Many studies have shown that various ionic substituents can be incorporated into HA. This modification may produce a mineral composition more similar to natural bone tissue with promising biological characteristics for use in bone regeneration. However, these substitutions can change the physicochemical characteristics of these biomaterials, being important to evaluate the biosafety before the production and commercialization on large scale. The present study aimed to evaluate the cytotoxicity, genotoxicity, mutagenicity, and embryotoxicity of nanostructured HA-based biomaterials with and without the addition of bioactive ions of CO32-, Zn2+ and Sr2+. The biomaterials were prepared and characterized by a group from the REGENERA-INCT network. A crude extract prepared at a concentration of 100 mg/mL, as recommended by ISO 10993-5, was used for cytotoxicity and genotoxicity analysis. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was used to measure cell viability after 24 hours of exposure to HA samples in the Chinese hamster ovary cell line. (CHO-K1). The cytokinesis-blocking micronucleus assay (CBMN) was performed to evaluate the mutagenicity of HAs after 24 hours of exposure, 3000 binucleated cells were evaluated per treatment in CHO-K1 cells. The bacterial reverse mutation was performed using the Salmonella Typhimurium (TA98) strain, with and without exogenous metabolism; all tests were performed in triplicate. The embryotoxicity test was performed on zebrafish (Danio rerio) according to OECD guideline number 236. Zebrafish embryos were exposed to 1 or 3 microspheres of different modified HA from 4 to 120 hours post-fertilization (hpf). Lethality and developmental outcomes were evaluated. In addition to developmental effects, larval behavior at 168 hpf was analyzed to verify whether the biomaterials have a neurotoxic action by measuring optomotor and avoidance responses. In in vitro tests, none of the HA samples induced cytotoxic effects about the negative control, nor did it affect the proliferative capacity of the cell culture. HA samples were also not able to generate nuclear alterations such as micronucleus, nucleoplasmic bridge, and sprouts. In the Ames test, no increase in the rate of revertant colonies was observed, and therefore, the tested biomaterials did not show mutagenic potential. After 120h of exposure to HA, CHA, SrHA, and ZnHA microspheres, there was no mortality higher than 20%, indicating the non- embryotoxic character of the tested biomaterials. All experimental groups showed positive optomotor and avoidance responses, which means that exposure of the embryo to the tested biomaterials did not present neurotoxic effects. Therefore, the results present excellent data on the biosafety of these modified HA-based nanostructured biomaterials for application in the bone regeneration process. Future studies are being carried out to assess changes at the molecular level and the assessment of osteogenic potential in human stromal/mesenchymal stem cells.

COMMITTEE MEMBERS:
Presidente - 2085604 - SUSANA MARGARIDA GOMES MOREIRA
Externa à Instituição - MARIA LUCILA HERNÁNDEZ MACEDO - UNIT
Externo à Instituição - FABIANO PERES MENEZES - UFRN