Solid State Phenomena Vol. 339

Abstract: Calcium phosphate is a natural biomineral and the major inorganic constituent of bones and teeth. Therefore, synthetic calcium phosphates that mimic the biogenic ones possess excellent biocompatibility as well as biodegradability and are promising materials for medicine. Due to their unique physiochemical properties, calcium phosphate nanoparticles (CaP NPs) are extensively exploited in nanomedicine as carriers of biomolecules, including peptides, proteins, and nucleic acids. In this regard, peptides are of particular interest as they are exceptionally selective and efficacious for the treatment of a broad range of diseases. Among various peptides for biomedical applications, cardio-specific peptides are particularly interesting since they represent a valuable alternative to conventional treatments. Moreover, they can contribute to overcome important clinical limitations, including drug resistance and non-specific biodistribution of traditional drug products. In this work, we have investigated the loading of a therapeutic mimetic peptide, which was previously shown to improve myocardial contraction and results in the restoration of cardiac function. Peptide-loaded CaP NPs were prepared by exploiting a biomineralization approach, by using a mineralizing solution containing Ca²⁺, Mg²⁺, and PO₄^3- ions. Several experimental conditions were tested by varying the reaction time, as well as the drug concentration. Colloidal stability, morphology, size, as well as drug loading were evaluated to identify the best candidate to be tested in vitro in the future.

Abstract: Self-assembly and mineralization of type I collagen (Col) with nanocrystalline apatite (nAp), by adding a solution of Ca(OH)₂ to a stirred Col-H₃PO₄ solution by fast dripping, allowed the preparation of Col/nAp fibrils with good crystallographic control of the mineral phase. In this work, in addition, we have cross-linked the mineralized fibers by using different reagents, namely glutaraldehyde (GTA), tannic acid (TA), 1-Ethyl-3-(3-dimethyl aminopropyl)-carbodiimide combined with N-Hydroxysuccinimide (EDC/NHS), and genipin (GP), aimed at producing different types of biopolymeric Col/nAp-based drug delivery scaffolds. In parallel, we have investigated two different methods to impregnate the scaffolds with molecules of the cocrystal diclofenac-metformin (DF-MET). The result, when using TA as a crosslinking reagent, shows the sequence of mineralized fibrils impregnation followed by crosslinking leads to maximum cocrystal molecule loading. The impregnated material is expected to be useful in settings with excessive and prolonged inflammation, since they affect negatively the fracture healing/bone repair processes, especially during the early stages of healing.

Abstract: Hydroxyapatite (HA) ceramic scaffolds are commonly used as bone graft substitutes. Design of such scaffolds is a challenge to improve biological properties and extend the applications of HA ceramics in the field of bone tissue engineering. In this work, we investigated the processing and the in vitro properties of HA ceramic scaffolds mimicking human trabecular bone architecture. Samples of human tibial trabecular bone were collected (University Hospital Center of Limoges) and scanned by X-Ray μ-computed tomography (μ-CT) to generate 3D model database. From this computer-aided design, HA ceramic scaffolds were shaped layer-by-layer by additive manufacturing using laser stereolithography (SLA). Then, green parts were sintered to obtain dense ceramic scaffolds. The shaped parts were compared to the model (wall thickness, size, and geometry of the porous network) using image analysis. A good agreement was found. Only small differences were detected due to a light overpolymerization or to some unprinted very small details that were not linked to a polymerized area of the previous layer. Due to part shrinkage during sintering a magnifying factor has to be applied to the scanned CAO model to match the real dimensions of the trabecular bone sample. Human mesenchymal stem cell (hMSC) cultures were performed to investigate the biological properties of these scaffolds (cell attachment and proliferation of hMSC). These preliminary biological evaluations show the good biocompatibility and cell adhesion of the HA substitute. This work evidences the efficiency of SLA to produce ceramic scaffold architectures mimicking that of the natural trabecular bone with promising biological behavior.

Abstract: Our current study concerns the structural analysis and mechanical properties under compressive loading of a new developed additive-manufactured hydroxyapatite (HA) scaffolds, designed for bone tissue engineering. Structural evaluation was performed by X-ray computed tomography (X-CT) and the compressive strength was determined by uniaxial testing method to compare the performance of the new structured material with those reported in the literature. The studied scaffolds showed a well-defined periodic structure with a well-controlled interconnected porosity which is about 32 %. The compressive strength was of 60 MPa and the Weibull modulus of 6. These values are higher than those generally obtained on porous scaffolds fabricated by other techniques with the same level of total porosity. These results demonstrate the potential use of this 3D printed scaffolds for load bearing bone tissue.

Abstract: The general term of CAD/CAM technology (i.e., Computer-Aided Design/Compute-Aided Manufacturing) comprises several aspects, such as subtractive manufacturing processes, like milling (soft and hard milling), and additive manufacturing processes, like Selective Laser Melting (SLM), which refers to metallic materials, or Selective Laser Sintering (SLS), which refers to glasses/glass-ceramics/ceramic, or polymeric, or related composite materials produced via powder metallurgy technique. In biomaterials fabrications, the first step in SLM or SLS technology is the digital design of the prosthetic restoration, whereby the patient's individual anatomical and morphological features are precisely described. Afterwards laser-aided melting or sintering is repeated (layer-by-layer) until the complete restoration item is fabricated. A wide range of dental materials can be produced by SLM or SLS technology, e.g., metals and alloys, thermoplastic polymers, glasses/ceramics, waxes, and thermoplastic composites. Thus, it is a promising technology for producing a variety of dental restorations, such as metal-ceramic restorations, all-ceramic restorations, maxillofacial prostheses, functional skeletons, individual scaffolds for tissue engineering, etc. SLM technology is already widely applied for fabricating metal objects for dental (e.g., Co-Cr alloy) and orthopedic prostheses. As a subsequence, in the last decade, researchers' interest has been shifted to SLS of ceramic powders, such as SiO₂, Al₂O₃, SiO₂/Al₂O₃, and ZrO₂/Y₂O₃. This article comprehensively reviews the SLS process and its prospects for producing glasses/glass-ceramic/ceramic materials for biomedical/dental applications. The experimental results clearly show that this very modern additive manufacturing technology does not jeopardize the properties of the ceramic biomaterials' properties.

Abstract: In this study wear behavior of metal matrix nanocomposites covers a distinctive mixture of Al 7075 reinforced through Titanium Carbide (TiC) and Graphene in nanoform. Present work consists of Al7075 base metal is reinforced with nanopowder TiC (2.5 % wt.) and Graphene (0.25% wt.). The samples casted by ultrasonic stir casting technique and machining in accordance with ASTM standards, then tested for wear behavioral characteristics using pin on disc. This method was functional to determine the effect of three factors like sliding velocity, applied load and sliding distance for the above work by using the Taguchi method. By considering three factors, three levels, and the composition of nanoTiC (2.5%) by keeping a constant Graphene (0.25% wt.), the applied load variations in steps are 10 N, 20 N, and 30 N, the sliding velocity is 1.5m/sec, 2.5m/sec, and 3.5 m/sec, and the sliding distances 500m, 1000m, and 1500 m to study the wear behavior.

Abstract: It is pertinent to mention here that the high temperature behaviour of CNT-reinforced NiCrAlY with CNT 3%, 5% and 7% with HVOF on T-SA213-T-11 steel at 600°C temperature in molten salt environment has never been studied. Thus, the present research was conducted to provide useful results for the application of CNT-reinforced composite coatings at high elevated temperatures are underwent low porosity, opaque coatings, they are more viscid in nature and are due to its low porosity, high dense coatings, more adhesive in nature and strong bond. Kinematics hot corrosion, oxidation and erosion are to be analyzed by the attainment of mass gain after each and every progression under thermogravimetric studies (1hour heating and 20 minutes cooling). Results will be achieved by using visual examination, and advanced microscopy like XRD and SEM/EDS analysis. Keywords: High temperature, hot corrosion, Thermal spray coatings HVOF, XRD and SEM/EDS analysis.