Jafar Javadpour

The development of hydrogel scaffolds with enhanced mechanical strength, controlled degradation behavior, and excellent biocompatibility remains a significant challenge in tissue engineering. In this study, composite hydrogel samples based on gelatin and chitosan were synthesized using a freeze‐drying technique to obtain a porous structure. Glutaraldehyde was used as a chemical crosslinker, and hydroxyapatite particles (HA; 1wt.%, 2wt.%, and 3wt.%) and functionalized multiwalled carbon nanotubes (f‐MWCNTs; 0.2wt.%, 0.3wt.%, and 0.4wt.%) were incorporated into this porous structure to improve both structural integrity and biological properties. Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray diffraction analyses confirmed the successful incorporation and interaction of the fillers within the polymer matrix. Increasing the HA and f‐MWCNTs content led to a reduction in pore size and significantly enhanced compressive strength and Young's modulus. Furthermore, the swelling capacity and degradation rate were effectively reduced with increasing HA and f‐MWCNT concentrations, leading to improved structural stability. In vitro evaluations using MC3T3‐E1 preosteoblasts revealed that scaffolds containing 1wt.% HA and 0.2wt.%–0.3wt.% f‐MWCNTs maintained cell viability above 70% and promoted cell adhesion and proliferation. These findings demonstrate the potential application of the developed chitosan/gelatin hydrogels as bioactive scaffolds in the field of tissue engineering.

It is well established that surface topography can affect cell functions. However, finding a reproducible and reliable method for regulating stem cell behavior is still under investigation. It has been shown that cell imprinted substrates contain micro- and nanoscale structures of the cell membrane that serve as hierarchical substrates, can successfully alter stem cell fate. This study investigated the effect of the overall cell shape by fabricating silicon wafers containing pit structure in the average size of spherical-like chondrocytes using photolithography technique. We also used chondrocyte cell line (C28/I2) with spindle-like shape to produce cell imprinted substrates. The effect of all substrates on the differentiation of adipose-derived mesenchymal stem cells (ADSCs) has been studied. The AFM and scanning electron microscopy images of the prepared substrates demonstrated that the desired shapes were successfully transferred to the substrates. Differentiation of ADSCs was investigated by immunostaining for mature chondrocyte marker, collagen II, and gene expression of collagen II, Sox9, and aggrecan markers. C28/I2 imprinted substrate could effectively enhanced chondrogenic differentiation compared to regular pit patterns on the wafer. It can be concluded that cell imprinted substrates can induce differentiation signals better than engineered lithographic substrates. The nanostructures on the cell-imprinted patterns play a crucial role in harnessing cell fate. Therefore, the patterns must include the nano-topographies to have reliable and reproducible engineered substrates.

3 mol% yttria-stabilized zirconia ceramics have been gaining attention as promising restorative materials that are extensively used in dental implant applications. However, implant failure due to bacterial infection and its bioinert surface slow osseointegration in vivo, which are significant issues in clinical applications. In this work, surface modification was achieved using a continuous wave carbon dioxide laser at a wavelength of 10.6 µm in an air atmosphere. Changes in the surface characteristics were evaluated using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and 2D roughness and hardness tests. The bioactivity of the laser-treated samples was studied by examining their behavior when immersed in the SBF solution. The formation of the hydroxyapatite phase on the laser-treated sample was much more uniform than that of its untreated counterparts. The antibacterial properties of surface-treated zirconia ceramics against Streptococcus mutans and Escherichia coli bacteria were rigorously examined. These results indicate that the laser-induced nanoscale grooves significantly improved antibacterial activity by creating hydrophobic surfaces. The cellular response was evaluated for 7 days on microtextures on the zirconia surfaces and an untreated sample with MC3T3-E1 pre-osteoblast cell line cultured under basal conditions. Surface topography was revealed to improve the cellular response with increased metabolic activity compared to the untreated sample and showed modulation of cell morphology for the entire time. These results suggest that laser modification can be an appropriate non-contact method for designing nanoscale microtextures to improve the biological response and antibacterial behavior of zirconia ceramics in restorative dentistry.

Taking the advantage of a novel magnesium phosphate precursor containing Na and Ca, the cementation rate of the cement, including only Mg/Mg–Na–Ca, was studied. Besides, two effective parameters, that is, calcination temperature, 650 °C and 800 °C, and powder-to-cement liquid ratio, 1 and 1.5 g/mL, were assessed. X-ray diffraction, scanning electron microscopy, ion chromatography, particle size analyser, Vicat needle and compression test were used to characterize the powders and obtained cements. The sample containing Mg–Na–Ca, calcined at 800 °C with powder-to-cement liquid ratio of 1.5, obtained the highest compressive strength, 20 MPa, but set fast. To control the kinetics of cementation, the powder containing Mg–Na–Ca calcined at 950 °C with powder-to-cement liquid ratio of 1.5 and 2 g/mL was assessed and the one with 2 g/mL set in 9 min possessing 22 MPa compressive strength was selected as optimal condition to be used as a candidate, injectable bone cement.

Introduction: The biological and mechanical properties of substances are relevant to their application as biomaterials and there are many efforts to enhance biocompatibility and mechanical properties of bio-medical materials. Objectives: In this stud

A handful of work focused on improving the intrinsic low mechanical properties of hydroxyapatite (HA) by various reinforcing agents. However, the big challenge regarding improving mechanical properties is maintaining bioactivity. To address this issue, we report fabrication of apatite-based composites by incorporation of alumina nanoparticles (n-Al2O3). Although numerous studies have used micron or submicron alumina for reinforcing hydroxyapatite, only few reports are available about the use of n-Al2O3. In this study, spark plasma sintering (SPS) method was utilized to develop HA-nAl2O3 dense bodies. Compared to the conventional sintering, decomposition of HA and formation of calcium aluminates phases are restricted using SPS. Moreover, n-Al2O3 acts as a bioactive agent while its conventional form is an inert bioceramics. The addition of n-Al2O3 resulted in 40% improvement in hardness along with a 110% increase in fracture toughness, while attaining nearly full dense bodies. The in-vitro characterization of nanocomposite demonstrated improved bone-specific cell function markers as evidenced by cell attachment and proliferation, alkaline phosphatase activity, calcium and collagen detection and nitric oxide production. Specifically, Gene expression analysis demonstrated that introduction of n-Al2O3 in HA matrix resulted in accelerated osteogenic differentiation of osteoblast and mesenchymal stem cells, as expression of Runx-2 and OSP showed 2.5 and 19.6 fold increase after 2 weeks (p<0.05). Moreover, protein adsorption analysis showed enhanced adsorption of plasma proteins to HA-nAl2O3 sample compared to HA. These findings suggest that HA-nAl2O3 could be a prospective candidate for orthopedic applications due to its improved mechanical and osteogenic properties.