Sorina Dinescu

Synthesis, characterization, and in vitro studies of graphene oxide/chitosan-polyvinyl alcohol films.

Nanocomposites based on chitosan-polyvinyl alcohol (CS-PVA) and graphene oxide (GO) were prepared by casting the stable aqueous mixture of the components. SEM, TEM and X-ray diffraction showed that graphene oxide is largely dispersed on molecular scale within CS-PVA matrix. FTIR investigation indicated the occurrence of some interaction between graphene oxide nanosheets and CS-PVA. The obtained composites are mechanically strong and exhibit improved thermal stability. By addition of 6 wt.% GO within CS-PVA blend, the elastic modulus increased over 200%. The cell viability and proliferation results showed that MC3T3-E1 mouse osteoblastic cells can adhere and developed on the CS-PVA/GO composite films. A significant proliferation potential was displayed by the cells in contact with CS-PVA/GO 6 wt.%. Graphene oxide reinforced CS-PVA with high mechanical and bioactive properties are potential candidates for tissue engineering.

In vitro cytocompatibility evaluation of chitosan/graphene oxide 3D scaffold composites designed for bone tissue engineering

Extensively studied nowadays, graphene oxide (GO) has a benefic effect on cell proliferation and differentiation, thus holding promise for bone tissue engineering (BTE) approaches. The aim of this study was not only to design a chitosan 3D scaffold improved with GO for optimal BTE, but also to analyze its physicochemical properties and to evaluate its cytocompatibility and ability to support cell metabolic activity and proliferation. Overall results show that the addition of GO in the scaffolds composition improved mechanical properties and pore formation and enhanced the bioactivity of the scaffold material for tissue engineering. The new developed CHT/GO 3 wt% scaffold could be a potential candidate for further in vitro and in vivo osteogenesis studies and BTE approaches.

Biocompatibility Assessment of Novel Collagen-Sericin Scaffolds Improved with Hyaluronic Acid and Chondroitin Sulfate for Cartilage Regeneration

Cartilage tissue engineering (CTE) applications are focused towards the use of implantable biohybrids consisting of biodegradable scaffolds combined with in vitro cultured cells. Hyaluronic acid (HA) and chondroitin sulfate (CS) were identified as the most potent prochondrogenic factors used to design new biomaterials for CTE, while human adipose-derived stem cells (ASCs) were proved to display high chondrogenic potential. In this context, our aim was not only to build novel 3D porous scaffolds based on natural compounds but also to evaluate their in vitro biological performances. Therefore, for prospective CTE, collagen-sericin (Coll-SS) scaffolds improved with HA (5% or 10%) and CS (5% or 10%) were used as temporary physical supports for ASCs and were analyzed in terms of structural, thermal, morphological, and swelling properties and cytotoxic potential. To complete biocompatibility data, ASCs viability and proliferation potential were also assessed. Our studies revealed that Coll-SS hydrogels improved with 10% HA and 5% CS displayed the best biological performances in terms of cell viability, proliferation, morphology, and distribution. Thus, further work will address a novel 3D system including both HA 10% and CS 5% glycoproteins, which will probably be exposed to prochondrogenic conditions in order to assess its potential use in CTE applications.

Sericin Enhances the Bioperformance of Collagen-Based Matrices Preseeded with Human-Adipose Derived Stem Cells (hADSCs)

Current clinical strategies for adipose tissue engineering (ATE), including autologous fat implants or the use of synthetic surrogates, not only are failing in the long term, but also can’t face the latest requirements regarding the aesthetic restoration of the resulted imperfections. In this context, modern strategies in current ATE applications are based on the implantation of 3D cell-scaffold bioconstructs, designed for prospective achievement of in situ functional de novo tissue. Thus, in this paper, we reported for the first time the evaluation of a spongious 60% collagen and 40% sericin scaffold preseeded with human adipose-derived stem cells (hADSCs) in terms of biocompatibility and adipogenic potential in vitro. We showed that the addition of the sticky protein sericin in the composition of a classical collagen sponge enhanced the adhesion and also the proliferation rate of the seeded cells, thus improving the biocompatibility of the novel scaffold. In addition, sericin stimulated PPARγ2 overexpression, triggering a subsequent upregulated expression profile of FAS, aP2 and perilipin adipogenic markers. These features, together with the already known sericin stimulatory potential on cellular collagen production, promote collagen-sericin biomatrix as a good candidate for soft tissue reconstruction and wound healing applications.

In vitro bio-functional performances of the novel superelastic beta-type Ti–23Nb–0.7Ta–2Zr–0.5N alloy

The materials used for internal fracture fixations and joint replacements are mainly made of metals which still face problems ranging from higher rigidity than that of natural bone to leaching cytotoxic metallic ions. Beta (β)-type titanium alloys with low elastic modulus made from non-toxic and non-allergenic elements are desirable to reduce stress shielding effect and enhance bone remodeling. In this work, a new β-type Ti-23Nb-0.7Ta-2Zr-0.5N alloy with a Youngs modulus of approximately 50 GPa was designed and characterized. The behavior of MC3T3-E1 pre-osteoblasts on the new alloy, including adhesion, proliferation and differentiation, was evaluated by examining the cytoskeleton, focal adhesion formation, metabolic activity and extracellular matrix mineralization. Results indicated that the pre-osteoblast cells exhibited a similar degree of attachment and growth on Ti-23Nb-0.7Ta-2Zr-0.5N and Ti-6Al-4V. However, the novel alloy proved to be significantly more efficient in sustaining mineralized matrix deposition upon osteogenic induction of the cells than Ti-6Al-4V control. Further, the analysis of RAW 264.7 macrophages cytokine gene and protein expression indicated no significant inflammatory response. Collectively, these findings suggest that the Ti-23Nb-0.7Ta-2Zr-0.5N alloy, which has an increased mechanical biocompatibility with bone, allows a better osteogenic differentiation of osteoblast precursor cells than Ti-6Al-4V and holds great potential for future clinical prosthetic applications.

Modulation of Adipogenic Conditions for Prospective Use of hADSCs in Adipose Tissue Engineering

Modern strategies in adipose tissue engineering (ATE) take advantage of the easy harvest, abundance and differentiation potential towards mesenchymal lineages of hADSCs. The controlled conversion of hADSCs to committed adipogenic precursors and further mature adipocytes formation is important for good long-term results in soft tissue regeneration. Thus, in this study, we report: (i) the isolation of the processed lipoaspirate (PLA) cells from adipose tissue and sanguine fractions; (ii) the phenotypic characterization of the PLA descendants; (iii) the design of a novel protocol for the modulation of adipogenic conditions in the perspectives of ATE applications. To modulate the differentiation rate through our protocol, we propose to selectively modify the formulation of the adipogenic media in accordance with the evolution of the process. Therefore, we aimed to ensure the long-term proliferation of the precursor cells and to delay the late adipogenic events. The status of differentiation was characterized in terms of intracellular lipid accumulation and reorganization of the cytoskeleton simultaneously with perilipin protein expression. Moreover, we studied the sequential activation of PPARγ2, FAS, aP2 and perilipin genes which influence the kinetics of the adipogenic process. The strategies developed in this work are the prerequisites for prospective 3D regenerative systems.

Gelatin–poly(vinyl alcohol) porous biocomposites reinforced with graphene oxide as biomaterials

The present work aims to develop new biocomposites based on gelatin (Gel) and poly(vinyl alcohol) (PVA) reinforced with graphene oxide (GO). On the one hand, the model is designed with consideration of the high performance of the aforementioned biopolymers as biomaterials; on the other hand, the original component of the system, GO, is expected to improve structural stability and boost mechanical strength. Porous Gel-PVA/GO materials with GO content ranging from 0.5 to 3 wt% are obtained by freeze-drying. Structural analysis by Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed the ability of well-dispersed GO nanosheets to form interactions with the polymers, leading to a unique molecular structuration. 3D analysis by X-ray microtomography (microCT) and scanning electron microscopy (SEM) suggests that GO has an influence on pore adjustment. According to mechanical tests, GO undoubtedly exhibits a beneficial effect on the polymer resistance against compressive stress, improving their compressive strengths by 97-100% with the addition of 0.5-3 wt% GO. Moreover, biological assessment using the MC3T3-E1 preosteoblast murine cell line indicated the fabrication of a cytocompatible composite formula, with potential for further in vivo testing and tissue engineering applications.

Chitosan-Graphene Oxide 3D scaffolds as Promising Tools for Bone Regeneration in Critical-Size Mouse Calvarial Defects

Limited self-regenerating capacity of human skeleton makes the reconstruction of critical size bone defect a significant challenge for clinical practice. Aimed for regenerating bone tissues, this study was designed to investigate osteogenic differentiation, along with bone repair capacity of 3D chitosan (CHT) scaffolds enriched with graphene oxide (GO) in critical-sized mouse calvarial defect. Histopathological/histomorphometry and scanning electron microscopy(SEM) analysis of the implants revealed larger amount of new bone in the CHT/GO-filled defects compared with CHT alone (p < 0.001). When combined with GO, CHT scaffolds synergistically promoted the increase of alkaline phosphatase activity both in vitro and in vivo experiments. This enhanced osteogenesis was corroborated with increased expression of bone morphogenetic protein (BMP) and Runx-2 up to week 4 post-implantation, which showed that GO facilitates the differentiation of osteoprogenitor cells. Meanwhile, osteogenesis was promoted by GO at the late stage as well, as indicated by the up-regulation of osteopontin and osteocalcin at week 8 and overexpressed at week 18, for both markers. Our data suggest that CHT/GO biomaterial could represent a promising tool for the reconstruction of large bone defects, without using exogenous living cells or growth factors.

A 3D Porous Gelatin-Alginate-Based-IPN Acts as an Efficient Promoter of Chondrogenesis from Human Adipose-Derived Stem Cells

Cartilage has limited regeneration potential. Thus, there is an imperative need to develop new strategies for cartilage tissue engineering (CTE) amenable for clinical use. Recent CTE approaches rely on optimal cell-scaffold interactions, which require a great deal of optimization. In this study we attempt to build a novel gelatin- (G-) alginate- (A-) polyacrylamide (PAA) 3D interpenetrating network (IPN) with superior performance in promoting chondrogenesis from human adipose-derived stem cells (hADSCs). We show that our G-A-PAA scaffold is capable of supporting hADSCs proliferation and survival, with no apparent cytotoxic effect. Moreover, we find that after exposure to prochondrogenic conditions a key transcription factor known to induce chondrogenesis, namely, Sox9, is highly expressed in our hADSCs/G-A-PAA bioconstruct, along with cartilage specific markers such as collagen type II, CEP68, and COMP extracellular matrix (ECM) components. These data suggest that our G-A-PAA structural properties and formulation might enable hADSCs conversion towards functional chondrocytes. We conclude that our novel G-A-PAA biomatrix is a good candidate for prospective in vivo CTE applications.

Comparative study of leptin and leptin receptor gene expression in different swine breeds

Leptin is an important regulator of appetite, energy metabolism, and reproduction and is mainly synthesized in the adipocytes and then secreted into the bloodstream. The leptin receptor was classified as type I cytokine receptor due to its structural homology with IL-6 receptors and the signaling pathways in which they are both involved. The aim of our study is to comparatively assess the gene expression levels of leptin (lep) and leptin receptor (lepr) in different swine breeds specialized either in meat production (Duroc, Belgian Landrace, Large White, Synthetic Lines LS-345, and LSP-2000) or fat production (Mangalitsa) in order to correlate them with morphological and productivity characteristics. Additionally, lepr pattern of expression was evaluated comparatively between different tissue types in the Mangalitsa breed. Our results revealed high expression of the lep gene in Mangalitsa compared to those of all the other breeds, while for the lepr gene, average/medium levels were registered in Mangalitsa and increased pattern of expression was found in the synthetic lines LS-345 and LSP-2000. Regarding the comparative analysis of lepr gene expression in various tissues in the Mangalitsa breed, elevated levels were found in the liver and kidney, while the lowest expression was identified in the brain and muscles. Our results suggest that the Mangalitsa population exhibits leptin resistance, which might be correlated with atypical morpho-productive characteristics for this breed, such as below-average prolificacy and a strong tendency to accumulate fat.