Banca de QUALIFICAÇÃO: LISZT YELTSIN COUTINHO MADRUGA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : LISZT YELTSIN COUTINHO MADRUGA
DATA : 22/07/2019
HORA: 14:30
LOCAL: Auditório do LAPET
TÍTULO:

Synthesis and characterization of carboxymethyl-kappa-carrageenan nanofibers for application in wound dressings

PALAVRAS-CHAVES:

Carboxymethyl-kappa-carrageenan; antioxidant activity; antibacterial activity; biomaterial; nanofiber.

PÁGINAS: 60
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Orgânica
ESPECIALIDADE: Polímeros e Colóides
RESUMO:

Chemical modifications of polysaccharides are important routes to increase, develop or change the properties of these polymers. The sulfation and carboxymethylation of polysaccharides has attracted great interest, since the modified polysaccharides present a variety of biological activities and increasing application in the production of biomaterials. However, sulfation methods generate toxic waste due to the use of strongly hydrolytic sulfating agents. In this study kappa-carrageenan (KC), a naturally sulfated polymer, was modified by carboxymethylation reaction with monochloroacetic acid in order to obtain different degrees of substitution (DS). The DS was calculated from the ¹H NMR spectra and ranged from 0.8 to 1.6. The chemical structure of carboxymethyl-kappa-carrageenan (CMKC) was characterized by infrared (FT-IR) and ¹H and ¹³C NMR spectra, which confirmed carboxymethylation. The chemical modification increased the relative viscosity of KC in water and decreased the relative viscosity in saline solution. CMKCs showed higher moisture absorption and retention as well as superior antioxidant activity when compared to KC. In the tests for antibacterial activity in solution, CMKCs with DS 0.8, 1.0 and 1.2 exhibited growth inhibition against Staphylococcus aureus, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa. Thus, in order to apply to biomaterials the synthesized polymer, nanofibers were formed through the electrospinning technique using an aqueous solution blend of polyvinyl alcohol (PVA) and 25 to 75% CMKC with DS 1.1 and posterior cross-linking by temperature. The fiber manufacturing process was completely green, with no hazardous waste produced. The nanofibers were characterized by FT-IR, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The characterization showed the presence of the carboxylate and sulfate groups in all the fibers, which proved the presence of CMKC. Cytocompatibility, cell growth and adhesion and differentiation in osteoblasts through stem cells derived from human adipose tissue (ADSC) were evaluated. The results showed that nanofibers with CMKC are cytocompatible and promote increased cell growth, adhesion and differentiation in osteoblasts. Adhesion and platelet activation assays and blood coagulation in contact with the material were performed with plasma and human blood samples. Antibacterial activity in solution and on the surface of the nanofibers were performed at 6 h and 24 h with strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Nanofibers with higher percentage of CMKC have more pronounced coagulant activity, as well as higher antibacterial activity in contact with the surface. Based on the obtained data, the biomaterial formed is a strong candidate for application in wound dressings.

MEMBROS DA BANCA:
Externa à Instituição - ELIZABETH CRISTINA GOMES DOS SANTOS - FANEC
Interna - 2212519 - JULIANA DE SOUZA NUNES
Presidente - 1149440 - ROSANGELA DE CARVALHO BALABAN