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Hybrid injectable hydrogels comprising of alginate, gelatin, and nanocrystalline cellulose (NCC) were conceived and processed through adaptation of interpenetrated network of ...alginate-gelatin, ionic crosslinking of alginate, and supramolecular interaction approach. The design of hybrid hydrogels was based on the hypothesis that it provides an environment that is favorable for cell proliferation, exchange of nutrients via porous structure, and are characterized by mechanical properties that closely resemble the native tissue. This aspect is important for the delivery of cells or biomolecules in bone tissue engineering. The hybrid hydrogels exhibited moderate swelling behavior on formation, and the porous structure of hydrogels as imaged via SEM was envisaged to facilitate easy migration of cells and rapid transportation of biomolecules. The hybrid hydrogels exhibited desired mechanical properties and were biocompatible as confirmed though MTT assay of fibroblasts. Interestingly, osteoblasts cultured within hydrogel using bone morphogenetic protein (BMP)-2 demonstrated the capability for encapsulation of cells and induced cell differentiation. The nanocrystalline cellulose significant impacted degradation and interaction between hydrogels and cells.
The study fundamentally explores a hypothesis driven novel hybrid hydrogel that provides an environment for favorable growth and proliferation of cells, exchange of nutrients and mechanical properties that closely match the native tissue.
We describe here a comprehensive study on the effect of cellular structure and melt pool boundary (MPB) condition on the mechanical properties, deformation and failure behavior of AlSi10Mg alloy ...processed by selective laser melting (SLM). The morphology of melt pool (MP) on the load bearing face of tensile samples was significantly different with build directions. It resulted in different mechanical properties of the samples with different build directions. Furthermore, the microstructure analysis revealed that the MP in the SLM AlSi10Mg alloy mainly consisted of columnar α-Al grains which were made of ultra-fine elongated cellular structure. Electron back-scatter diffraction (EBSD) analysis revealed that the long axis of cellular structure and columnar grains were parallel to < 100 >, which resulted in < 100 > fiber texture in SLM AlSi10Mg alloy. However, Schmid factor calculation demonstrated that the anisotropy of mechanical properties of the SLM AlSi10Mg alloy built with different direction was mainly dependent on the distribution of MPB on the load bearing face, and not texture. The defects including pores, residual stress and heat affected zone (HAZ) located at MPB made it the weakest part in the SLM AlSi10Mg. The sample built along horizontal direction exhibited good combination of strength and plasticity and is attributed to the lowest fraction of MPBs that withstand load during tensile. MPB had strong influence on the mechanical properties and failure behavior of SLM AlSi10Mg built with different directions.
We here describe the structure–process–property relationship of graphene oxide-mediated proliferation and growth of osteoblasts in conjunction with the physico-chemical, mechanical, and structural ...properties. Chitosan–graphene network structure scaffolds were synthesized by covalent linkage of the carboxyl groups of graphene oxide with the amine groups of chitosan. The negatively charged graphene oxide in chitosan scaffolds was an important physico-chemical factor influencing cell–scaffold interactions. Furthermore, it was advantageous in enhancing the biocompatibility of the scaffolds and the degradation products of the scaffolds. The high water retention ability, hydrophilic nature, and high degree of interconnectivity of the porous structure of chitosan–graphene oxide scaffolds facilitated cell attachment and proliferation and improved the stability against enzymatic degradation. The cells infiltrated and colonized the pores of the scaffolds and established cell–cell interactions. The interconnectivity of the porous structure of the scaffolds helps the flow of medium throughout the scaffold for even cell adhesion. Moreover, the seeded cells were able to infiltrate inside the pores of chitosan–graphene oxide scaffolds, suggesting that the incorporation of polar graphene oxide in scaffolds is promising for bone tissue engineering.
We describe a comparative assessment of the structure–property–process relationship of three-dimensional chitosan–nanohydroxyapatite (nHA) and pure chitosan scaffolds in conjunction with their ...respective biological response with the aim of advancing our insight into aspects that concern bone tissue engineering. High- and medium-molecular-weight (MW) chitosan scaffolds with 0.5, 1 and 2
wt.% fraction of nHA were fabricated by freezing and lyophilization. The nanocomposites were characterized by a highly porous structure and the pore size (∼50 to 120
μm) was in a similar range for the scaffolds with different content of nHA. A combination of X-ray diffraction, Fourier transform infrared spectroscopy and electron microscopy indicated that nHA particles were uniformly dispersed in chitosan matrix and there was a chemical interaction between chitosan and nHA. The compression modulus of hydrated chitosan scaffolds was increased on the addition of 1
wt.% nHA from 6.0 to 9.2
kPa in high-MW scaffold. The water uptake ability of composites decreased with an increase in the amount of nHA, while the water retention ability was similar to pure chitosan scaffold. After 28 days in physiological condition, nanocomposites indicated about 10% lower degree of degradation in comparison to chitosan scaffold. The biological response of pre-osteoblasts (MC 3T3-E1) on nanocomposite scaffolds was superior in terms of improved cell attachment, higher proliferation, and well-spread morphology in relation to chitosan scaffold. In composite scaffolds, cell proliferation was about 1.5 times greater than pure chitosan after 7 days of culture and beyond, as implied by qualitative analysis via fluorescence microscopy and quantitative study through MTT assay. The observations related to well-developed structure morphology, physicochemical properties and superior cytocompatibility suggest that chitosan–nHA porous scaffolds are potential candidate materials for bone regeneration although it is necessary to further enhance the mechanical properties of the nanocomposite.
The overview describes the synergy between biological sciences and cellular structures processed by additive manufacturing to elucidate the significance of cellular structured implants in eliminating ...stress shielding and in meeting the bio-mechanical property requirements of elastic modulus, impact resistance, and fatigue strength in conjunction with the biological functionality. The convergence of additive manufacturing, computer-aided design, and structure-property relationships is envisaged to provide the solution to the current day challenges in the biomedical arena. The traditional methods of fabrication of biomedical devices including casting and mechanical forming have limitations because of the mismatch in micro/microstructure, mechanical, and physical properties with the host site. Additive manufacturing of cellular structured alloys via electron beam melting and laser powder bed fusion has benefits of fabricating patient-specific design that is obtained from the computed tomography scan of the defect site. The discussion in the overview consists of two aspects – the first one describes the underlying reason that motivated 3D printing of implants from the perspective of minimising stress shielding together with the mechanical property requirements, where the mechanical properties of cellular structured implants depend on the cellular architecture and percentage cellular porosity. The second aspect focuses on the biological response of cellular structured devices.
The objective of the study described here is to evaluate the effect of temperature, strain rate, and strain on the microstructure of dynamically recrystallized nickel–chromium alloy (800H) subjected ...to hot compression over a wide range of strain rates. The microstructural evolution was studied by electron backscattered diffraction (EBSD) and the effect of adiabatic heating on hot deformation was analyzed to correct the flow curves at high strains. The grain orientation spread (GOS) approach was used to distinguish the dynamic recrystallization (DRX) grains from the deformed matrix. The nucleation mechanism of DRX and the role of Σ3n CSL boundaries during DRX were explored. Additionally, the influence of carbides on the DRX behavior was studied within the temperature of 850–950°C. The results indicated that the DRX can be stimulated by adiabatic heating and strong dislocation–dislocation interaction occurring with increase in the strain rate in the range of 1–30s−1. The threshold value of GOS (1.2°) separated the DRX grains from the deformed matrix. The recrystallized grains nucleated at pre-existing grain boundaries by extensive bulging associated with grain fragmentation. The Σ3n CSL boundaries play an important role in DRX and they can be generated through interaction among them after the initiation of DRX. The precipitation of Cr23C6 and Ti(C, N) at the parent grain boundary could restrain or even inhibit the occurrence of DRX in the temperature range of 850–950°C.
A novel magnetic drug-targeting carrier consisting of magnetic nanoparticles encapsulated with a smart polymer with characteristics of controlled drug release is described. The carrier is ...characterized by functionalized magnetite (Fe
3O
4) and conjugated therapeutic agent doxorubicin, which is encapsulated with the thermosensitive polymer, dextran-
g-poly(
N-isopropylacrylamide-
co-
N,
N-dimethylacrylamide) dextran-
g-poly(NIPAAm-
co-DMAAm). The surface of magnetite nanoparticles was functionalized by chemical bonding with 3-mercaptopropionic acid hydrazide (HSCH
2CH
2CONHNH
2) via Fe–S covalent bonds. The anticancer therapeutic drug, doxorubicin, was attached to the surface of the functionalized magnetic nanoparticles through an acid-labile hydrazone-bond, formed by the reaction of hydrazide group of HSCH
2CH
2CONHNH
2 with the carbonyl group of doxorubicin. The dextran-
g-poly(NIPAAm-
co-DMAAm) smart polymer exhibits a lower critical solution temperature (LCST) of ∼38
°C, which is representative of a phase transition behavior. This behavior allows for an on–off trigger mechanism. At an experimental temperature lower than LCST, the drug release was very low. However, at a temperature greater than LCST, there was an initially rapid drug release followed by a controlled released in the second stage, especially, in the mild acidic buffer solution of pH 5.3. The release of drug is envisaged to occur by the collapse of the encapsulated thermosensitive polymer and cleavage of the acid-labile hydrazone linkage. The proposed carrier is appropriately suitable for magnetic targeting drug delivery system with longer circulation time, reduced side effects and controlled drug release in response to the change in external temperature.
The structure–property relationship in 0.06C–5.5Mn steel subjected to different annealing temperatures and time was studied. Mn played a stronger effect on stabilizing austenite in comparison with ...Ni, and low-C medium-Mn steel possessed excellent hardenability. The reverse transformation of martensite to austenite occurred during intercritical annealing, and the volume fraction was first increased and then decreased on increasing annealing temperature or prolonging annealing time, indicative of change in thermal stability by element partitioning and coarsening of grain size. Correspondingly, the elongation was first increased and then decreased, consistent with the variation in the stability of reverted austenite. The yield strength was gradually decreased because of several factors, including recrystallization of
α
′ martensite, decreased stability of reverted austenite, and coarse grain size. The maximum product of strength and ductility was obtained on annealing at 650 °C for 10 min, which was attributed to the optimal stability of reverted austenite rather than the highest volume fraction, and tensile strength and elongation were 1120 MPa and 23.3%. The strain partitioning behavior of two phases was elucidated by analyzing Lüders straining and continuous work hardening after yield point elongation, and the deformation mechanism was strongly related to the stability of reverted austenite.
