Zeta potential measurement in bioactive collagen

Abstract

The focus of this work is to show the influence of surface charge on the bioactivity of modified collagen fiber surface. Because silica plays an important role on bone mineralization process, silica obtained by a sol-gel process was used as a surface modification agent. Zeta potential (xi) of silica-coated and non-coated samples was measured as a function of pH. It was observed a shift in xi vs. pH. The isoelectric point for silica-coated collagen was 6.8, while that of non-treated sample it was near 10. Pure silica has isoelectric point near 2, and the shift observed indicates that at least part of the silica was incorporated onto the surface during the treatment. The ability of samples exposed to biological simulated fluids (SBF) to form a hydroxyapatite layer has been used to recognize bioactive materials. The pH of these biological solutions is about 7.3. It means that treated samples acquire negative charge when in contact with the biological solution and attract ions like Ca2+, HPO4(2-), and OH- to form HA coatings. Micrographs of chemically treated samples corroborate this assumption. For treated samples, the formation of a coating layer is clear after 5-day immersion in SBF, while pure collagen remains practically unaltered. Fourier Transform Infrared Spectroscopic (FTIR) analyses confirmed that the coating layer has P-O vibration bands near 1060 cm-1 and 600 cm-1 characteristic of hydroxyapatite (HA)

Extraction and characterization of highly purified collagen from bovine pericardium for potential bioengineering applications

“…However, the presence of larger amounts of NaCl, as well as other elements in the collagen product, contributes to the contamination of the material [47]. Other trace elements such as Mg, Al, Si, P, K and Ca were observed in the EDS spectrum of the commercial collagen (Fig.…”

Validation of method for determining the isoelectric point of protein solutions

“…The corresponding pH value is the isoelectric pH of gelatin [17] that must comply with the one found in literature, of 4.7.…”

“…Therefore, a graphical representation of the Zeta potential [16,17], depending on the pH will be positive at low pH and negative at high pH. The point where the graph goes through zero is the Zeta potential.…”

Cerâmicas bioativas: estado da arte

“…Devido ao seu caráter quebradiço, os vidros têm uso limitado a regiões do organismo que não estão sujeitas a grandes demandas de carga mecânica, como na substituição de pequenos ossos do ouvido interno [27][28][29][30] . Domingues et al 31,32 revestiram materiais bioinertes como as fibras de vidro de aluminosilicato e o colágeno com tetraetóxido de silício (TEOS) puro e observaram que estes materiais se tornaram bioativos após o tratamento quími-co. Um aspecto importante deste método de revestimento é o fato dele não ser contínuo, ou seja, apenas as superfícies dos materiais são recobertas, enquanto os espaços vazios entre os mesmos, como no caso de materiais fibrosos, podem ser conservados. A presença desta porosidade é indispensável para o crescimento de novos vasos sanguíneos, o que ocorre apenas em regiões onde há fluxo do plasma sanguíneo.…”

“…Este fosfato de cálcio se transforma espontaneamente em apatita, que é a fase estável no ambiente corporal 81 . Domingues et al 31,32 explicaram a bioatividade de fibras de vidro de aluminosilicato e de fibras de colágeno tratadas quimicamente em TEOS com base nos resultados de potencial zeta. Através desta análise, foi verificado que os materiais não bioativos (não tratados quimicamente) apresentaram um pH no ponto isoelétrico maior que o pH da solução SBF (aproximadamente 8 para a fibra de vidro e 9,6 para o colágeno) e, portanto, desenvolvem uma carga superficial positiva quando imersos nesta solução.…”