[ review on different approaches for improving cell infiltration in electrospun nanofibrous scaffolds]

In recent years, electrospinning that has the capability to form polymeric nano-microfibers has gained substantial attention for fabrication of tissue engineering scaffolds. The morphological resemblance to native extracellular matrix [ECM], high surface to volume ratio, high porosity, and pore interconnectivity are amongst the brilliant features of electrospun structures. The high surface area to volume ratio and interconnected pores of these fibrous meshes confer desirable cell attachment and growth. However, due to small pore sizes and high packing density of electrospun nanofibers, cell penetration into a conventional electrospun mat is completely restrained. Scarce cell infiltration in turn prohibit cell migration into internal parts of the scaffold, cause inhomogeneous cell distribution throughout the structure, limit vascularization, and impede tissue ingrowth. In fact, traditional electrospun nanofibrous scaffolds in practice act as two-dimensional [2D] surfaces rather than three-dimensional [3D] microenvironments. Thus far, a number of approaches have been employed to solve this problem, which range from simple variations in electrospinning parameters to intricate post-processing modifications. Some efforts directly manipulate the electrospun mat characteristics to enhance cell penetration, while others combine cells with scaffolds or encourage cells to migrate into internal parts with different stimuli. In the present study, we have attempted to provide an overview of different approaches offered for improving cell infiltration in electrospun scaffolds

Study of Collagen Immobilization on a Novel Nanocomposite to Enhance Cell Adhesion and Growth

Surface properties of a biomaterial could be critical in determining biomaterial's biocompatibility due to the fact that the first interactions between the biological environment and artificial materials are most likely occurred at material's surface. In this study, the surface properties of a new nanocomposite [NC] polymeric material were modified by combining plasma treatment and collagen immobilization in order to enhance cell adhesion and growth. Methods: NC films were plasma treated in reactive O[2] plasma at 60 W for 120 s. Afterward, type I collagen was immobilized on the activated NC by a safe, easy, and effective one-step process. The modified surfaces of NC were characterized by water contact angle measurement, water uptake, scanning electron microscopy [SEM], and Fourier transformed infrared spectroscopy in attenuated total reflection mode [ATR-FTIR]. Furthermore, the cellular behaviors of human umbilical vascular endothelial cells [HUVEC] such as attachment, growth and proliferation on the surface of the NC were also evaluated in vitro by optical microscopy and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide test. Results: The outcomes indicated that plasma treatment and collagen immobilization could improve hydrophilicity of NC. SEM micrograph of the grafted film showed a confluent layer of collagen with about 3-5 jum thicknesses. In vitro tests showed that collagen-grafted and plasma-treated surfaces both resulted in higher cell adhesion and growth state compared with untreated ones. Conclusion: Plasma surface modification and collagen immobilization could enhance the attachment and proliferation of HUVEC onto NC, and the method would be usefully applied to enhance its biocompatibility

Development of an allogeneic cultured dermal substitute using a standard human fibroblast bank

Fibroblasts are mesenchymal cells that can be readily cultured in the laboratory and play a significant role in epithelialmesenchymal interactions, secreting various growth factors and cytokines that have a direct effect on epidermal proliferation, differentiation and formation of extracellular matrix. They have been incorporated into various tissue-engineered and used for a variety of clinical applications, including the treatment of burns, chronic venous ulcers and several other clinical applications in dermatology and plastic surgery. Isolated fibroblasts by the enzymatic process from foreskin were cultivated successively in a culture medium to establish cell banking. Foreskin and the last subcultured cells were checked for HBV, HCV, HIV, HSV I, HSV II, HTLV I, HTLV II, EBV, CMV, Treponema Pallidum, Mycoplasma sp. and Clamydia. The 1[st], 5[th] and 10[th] subcultured cells were processed for immunocytochemistry studies using a panel of monoclonal antibodies including antibodies to MHC class I and II antigens for ensuring the elimination of superficial cell antigens during cultivation. Subcultured cells were karyotyped to find any chromosomal abnormalities. The best passages were chosen for culturing on silicone sheets provided by the Iran Polymer and Petrochemical Institute. Evaluation for bacteria and viruses by molecular methods was negative. Karyotyping of cultured fibroblasts after the 10[th] passage showed some abnormalities. HLA expression was imperceptible in the cells obtained from the 10[th] sub-culture. The best passages were from 5th to 10[th] for banking and culturing on silicone sheets. Expression of HLA on fibroblast surfaces was diminished during subculturing. To prevent chromosomal abnormalities in fibroblast passaging, we should select the best colony that is expected to be chromosomally stable with the least antigenicity. In our study, the 5[th] to 10[th] sub-cultures were the best cells for the purpose of grafting and acceleration of the wound healing