جستجوی مقالات مرتبط با کلیدواژه "hydroxyapatite" در نشریات گروه "زیست شناسی"

Chondroitinase ABCI is a bacterial lyase that degrades glycosaminoglycans and promotes axonal growth and functional improvement. However the stability and maintenance of this enzyme is very limited. One of the strategies to overcome this limitation is to immobilize the enzyme. In this research, chondroitinase ABCI (cABCI) from Proteus Vulgaris was immobilized on hydroxyapatite nanoparticles. Hydroxyapatite is a non-toxic ceramic biomaterial that has a high surface area, which is beneficial for loading a large amount of enzyme. Therefore, to increase the stability of chondroitinase ABCI, immobilization on hydroxyapatite nanoparticles for 4 hours through physical adsorption in  phosphate buffer pH 5, 6.8, and 8 at 4◦C was carried out. Enzyme immobilization on hydroxyapatite nanoparticles was then confirmed by field emission gun-scanning electron microscopy and UV-spectroscopy, before and after immobilization. Then, in order to obtain the optimal pH and temperature, the activity of the nanosystem was investigated at three pH and temperatures (4°C, 25°C, and 37°C). Results revealed higher activity at pH 5 and temperature 4 ◦C than the other pH and temperatures for the nanosystem. Based on the obtained results, which show the stability of the nanosystem at all three temperatures compared to the free enzyme, this nanosystem could be a potential candidate for clinical applications in future.

In recent years, the focus of researches in the field of tissue engineering has been on the preparation of scaffold materials and methods. 3D printing is an emerging technology that can accurately and quickly prepare bone tissue engineering scaffolds with specific shapes and structures. One of the most common 3D printing methods is fused deposition modeling (FDM), the materials used in this method are polymers such as polycaprolactone (PCL). In this study, 3D printed PCL scaffolds were made and due to the hydrophobic and non-osteogenic nature of PCL, the surface of the scaffolds was coated with a 1% solution of hydroxyapatite (HA) and bioactive glass (BG) bioceramics. Surface modification of PCL scaffolds was done to increase hydrophilicity and improve cell attachment. Field emission scanning electron microscop (FeSEM) images, Energy-dispersive X-ray spectroscopy (EDS) and mapping of the surface elements of the scaffolds confirmed the proper coating of PCL scaffolds with HA and BG bioceramics. The biocompatibility of PCL/HA/BG scaffolds and the cell viability and attachment on the surface of the scaffolds were investigated by seeding of human adipose mesenchymal stem cells (hAMSCs) and using MTT test and FeSEM images. Also, the potential of PCL/HA/BG scaffolds in osteogenic differentiation of hAMSCs was evaluated by alkaline phosphatase activity measurement test and immunocytochemical staining. The results showed that the three-component PCL/HA/BG scaffolds improved the proliferation and osteogenic differentiation of hAMSCs, so the PCL/HA/BG scaffolds can be a suitable candidate for bone tissue engineering applications.

Graphene-based nanomaterials are being investigated for their biocompatibility and bioactivity, as well as their ability to improve osteogenic differentiation. In this research, the base material, reduced graphene oxide (rGO) sheets, were decorated with hydroxyapatite and strontium (rGO / HAp-Sr) to induce osteogenic differentiation in adipose-derived mesenchymal stem cells. Different techniques were used to determine the properties of the nanocomposite such as diffraction analysis techniques (XRD) and transmission electron microscopy (to evaluate the size and morphology of HAp-Sr on rGO plates), FT-IR (to analyze the nanocomposite functional group), Raman spectroscopy (to investigate possible disorders in nanocomposite structure and number of layers), induced dual plasma emission spectroscopy (to assess atomic concentration of Ca and Sr), zeta potential(electrical potential of the nanocomposite) and MTT (nanocomposite cytotoxicity assessment) were used. The ossification potential of the synthesized nanocomposite was investigated and confirmed using the calcium deposition test in dipose-derived mesenchymal stem cells. According to the obtained results, osteogenic differentiation induction is possible using synthesized nanocomposites without the need for chemical inducers.

This study was performed to investigate the chemical composition of the caudal spine in Hemitrygon bennettii (Muller and Henle, 1841) as a source for hydroxyapatite (HA) extraction. Therefore, the chemical structure of caudal spines of fish sampled from the mangrove swamps at Chabahar Bay was determined at calcined (baked at high temperature) and uncalcined conditions. The Raman spectroscopy and ICP-OES were used for structural and elemental analyses, respectively. The sharpest peaks in the Raman were observed at 962cm-1 which was probably due to the symmetric stretching vibrations of apatite phosphates. The adsorbed OH ions also indicated peaks at 3400-3500cm-1 of both calcined and uncalcined samples. The presence of organic residue in uncalcined samples was highlighted by several peaks at 2700-3050 and 1300-1500cm-1 which may be due to both stretching and bending vibrations of CH, CH2 and CH3 groups. Some peaks at 1200-1800cm-1 may also be related to amine residues of proteins. In terms of ion concentrations, high amounts of sodium and magnesium contents in the spine structure (compared to other natural resources of HA extraction) may improve the biocompatibility of extracted HA.

Nowadays, bone tissue repair with increasing bone disorders and injuries have special importance. Bone tissue engineering provided specific solutions to these problems. The present study was conducted with the aim of purification of recombinant fusion peptide containing hydroxyapatite affinity tag using the ceramic chromatography column.

In this study, a fusion peptide was designed which at one side comprised the heparin-binding domain sequence, which can be attached to various types of growth factors involved in tissue repair and entrap these factors at the site of the lesion. On the other side, it contained a tag, which included a sequence derived from a laboratory study based on phage expression. The reason for keeping the sequence of this tag is to attach the peptide to the scaffold containing hydroxyapatite and purifying the recombinant peptide by the hydroxyapatite column. Therefore, the gene sequence was optimized and synthesized for expression in the prokaryotic host of E.coli strain BL21. Then the gene sequence was subcloned by double digestion with the SacI and BamHI enzymes into the expression vector of pET-21a(+). The expression of the recombinant peptide was investigated by SDS-PAGE and western blot. In order to optimize the purification conditions, two-step purification was carried out by applying fundamental changes in the main work method of the manufacturer company and was purified with acceptable purity. Finally, the existence of peptide assemblies was investigated by the SLD method.

The results of PCR cloning, enzymatic digestion using SacI and BamHI enzymes and sequencing indicated the accuracy of the cloning process. On the other hand, expression of the fusion peptide was confirmed by SDS-PAGE and Western blot techniques, and its migration onto the gel resulted in a band cleavage of about 12 kDa. Changes made to the manufacturer's workflow allowed the purification process to be optimized and the results of the DLS method showed the purity of the purified peptide.

The results indicate the desirable expression and remarkable purity of the fusion peptide designed in this study.

Infection after the surgery is one of the problems of bone scaffolds implants which is normally treated by systemic administration of antibiotics. But due to the poor blood circulation in bone tissue, large antibiotic doses are needed which lead to further drawbacks to renal and hepatic systems.
Material and In this study, the effect of zinc oxide addition on antibacterial behavior of hydroxyapatite- Poly lactic-co-glycolic acid scaffold was evaluated. The synthesized composite was characterized by X-ray diffraction, scanning electron microscopy equipped with elemental analysis and Fourier transform infrared spectra. In order to determine the antibacterial activity of the fabricated scaffold, Staphylococcus aureus (ATTC 25922) and Escherichia coli (ATTC 25923) were used as test microorganisms.
The results showed that Hydroxyapatite- Poly lactic-co-glycolic acid scaffold did not make inhibition zone in culture medium but the modification of Hydroxyapatite- Poly lactic-co-glycolic acid scaffold’s surface by zinc oxide particles caused Hydroxyapatite- Poly lactic-co-glycolic acid- zinc oxide scaffold to have antibacterial inhibition zone of 12 and 20 mm for Escherichia coli and Staphylococcus aureus, respectively.
Discussion and This study revealed that the addition of antibacterial agent to applicable bone tissue engineering scaffolds could be considered as an appropriate way to prevent the growth of infection at the scaffold site.

The aim of this study is to investigate the relationship between the structure and function of an osteocalcin derived peptide on hydroxyapatite nanocrystal formation. For this purpose،، a natural motif sequence consisting of 13 amino acids present in the first helix of osteocalcin was selected based on its calcium binding ability and synthesized in both acidic and amidic forms using solid phase method. Circular dichroism (CD) and electron microscopy were performed to examine the structure and function of synthesized peptides. Moreover، the effect of these peptides on the viability of osteoblast cells was evaluated. Electron microscopy analysis showed the formation of plate-like HA nanocrystals in the presence of amidic peptide. In contrast، amorphous calcium phosphate was formed in the presence of acidic peptide. CD spectra analysis confirmed the random coil structure with lower molar elipticity for amidic peptide. In addition، the amidic peptide significantly increased the proliferation of osteoblast cells. It is concluded that increased bioactivity، which only occurred in amidic peptide is attributable to C-terminal amidation. It is also proposed that peptides with the ability to promote HA formation have the potential to be utilized in hard tissue regeneration high bioactivity and biocompatibility.