Bactericidal effects of nanopatterns: A systematic review.

We systematically reviewed the currently available evidence on how the design parameters of surface nanopatterns (e.g. height, diameter, and interspacing) relate to their bactericidal behavior. The systematic search of the literature resulted in 46 studies that satisfied the inclusion criteria of examining the bactericidal behavior of nanopatterns with known design parameters in absence of antibacterial agents. Twelve of the included studies also assessed the cytocompatibility of the nanopatterns. Natural and synthetic nanopatterns with a wide range of design parameters were reported in the included studies to exhibit bactericidal behavior. However, most design parameters were in the following ranges: heights of 100-1000 nm, diameters of 10-300 nm, and interspacings of  <500 nm. The most commonly used type of nanopatterns were nanopillars, which could kill bacteria in the following range of design parameters: heights of 100-900 nm, diameters of 20-207 nm, and interspacings of 9-380 nm. The vast majority of the cytocompatibility studies (11 out of 12) showed no adverse effects of bactericidal nanopatterns with the only exception being nanopatterns with extremely high aspect ratios. The paper concludes with a discussion on the evidence available in the literature regarding the killing mechanisms of nanopatterns and the effects of other parameters including surface affinity of bacteria, cell size, and extracellular polymeric substance (EPS) on the killing efficiency. STATEMENT OF SIGNIFICANCE: The use of nanopatterns to kill bacteria without the need for antibiotics represents a rapidly growing area of research. However, the optimum design parameters to maximize the bactericidal behavior of such physical features need to be fully identified. The present manuscript provides a systematic review of the bactericidal nanopatterned surfaces. Identifying the effective range of dimensions in terms of height, diameter, and interspacings, as well as covering their impact on mammalian cells, has enabled a comprehensive discussion including the bactericidal mechanisms and the factors controlling the bactericidal efficiency. Overall, this review helps the readers have a better understanding of the state-of-the-art in the design of bactericidal nanopatterns, serving as a design guideline and contributing to the design of future experimental studies.

Chitosan-gelatin porous scaffold incorporated with Chitosan nanoparticles for growth factor delivery in tissue engineering.

Designing scaffolds capable of mimicking the 3D structure of the extracellular matrix (ECM) and deliver signaling factors to affect and control the cell response favorably, is of high importance in the field of tissue engineering. As polymeric nanoparticles are effective vehicles for delivering growth factors, this study aimed to fabricate and characterize a nanocomposite scaffold based on chitosan and gelatin, incorporated with chitosan nanoparticles loaded with basic fibroblast growth factor (bFGF) and bovine serum albumin (BSA). Nanoparticles, prepared by the ionic gelation method, were loaded with BSA-bFGF and introduced into chitosan-gelatin scaffolds to enhance their biological properties. Structural characterizations and biological assays showed that nanoparticles significantly affected the physical properties of the scaffold and could provide a sustained release of growth factor to enhance the proliferation of fibroblast cells significantly. These results are promising for improving the properties of chitosan-gelatin scaffolds in tissue engineering applications, especially where the delivery of angiogenic growth factor such as bFGF is needed.

Immunological compatibility status of placenta-derived stem cells is mediated by scaffold 3D structure.

Placenta-derived amniotic epithelial cells (AECs), a great cell source for tissue engineering and stem cell therapy, are immunologically inert in their native state; however, immunological changes in these cells after culture and differentiation have challenged their applications. The aim of this study was to investigate the effect of 2D and 3D scaffolds on human lymphocyte antigens (HLA) expression by AECs. The effect of different preparation parameters including pre-freezing time and temperature was evaluated on 3D chitosan-gelatine scaffolds properties. Evaluation of MHC class I, HLA-DR and HLA-G expression in AECs after 7 d culture on 2D bed and 3D scaffold of chitosan-gelatine showed that culture of AECs on the 2D substrate up-regulated MHC class I and HLA-DR protein markers on AECs surface and down-regulated HLA-G protein. In contrast, 3D scaffold did not increase protein expression of MHC class I and HLA-DR. Moreover, HLA-G protein expression remained unchanged in 3D culture. These results confirm that 3D scaffold can remain AECs in their native immunological state and modification of physical properties of the scaffold is a key regulator of immunological markers at the gene and protein expression levels; a strategy which circumvents rejection challenge of amniotic stem cells to be translated into the clinic.

Induction of antimicrobial peptides secretion by IL-1ß enhances human amniotic membrane for regenerative medicine.

Due to antibacterial characteristic, amnion has been frequently used in different clinical situations. Developing an in vitro method to augment endogenous antibacterial ingredient of amniotic epithelial and mesenchymal stem cells is desirable for a higher efficacy of this promising biomaterial. In this study, epithelial or mesenchymal side dependent effect of amniotic membrane (AM) on antibacterial activity against some laboratory and clinical isolated strains was investigated by modified disk diffusion method and colony count assay. The effect of exposure to IL-1ß in production and release of antibacterial ingredients was investigated by ELISA assay. The results showed that there is no significant difference between epithelial and mesenchymal sides of amnion in inhibition of bacterial growth. Although the results of disk diffusion showed that the AM inhibitory effect depends on bacterial genus and strain, colony count assay showed that the extract of AM inhibits all investigated bacterial strains. The exposure of AM to IL-1ß leads to a higher level of antibacterial peptides secretion including elafin, HBD-2, HBD-3 and cathelicidic LL-37. Based on these results, amniotic cells possess antibacterial activity which can be augmented by inflammatory signal inducers; a process which make amnion and its epithelial and mesenchymal stem cells more suitable for tissue engineering and regenerative medicine.

The effect of cryopreservation on anti-cancer activity of human amniotic membrane.

Human amniotic membrane (AM) is an appropriate candidate for treatment of cancer due to special properties, such as inhibition of angiogenesis and secretion of pro-apoptotic factors. This research was designed to evaluate the impact of cryopreservation on cancer cell death induction and anti-angiogenic properties of the AM. Cancer cells were treated with fresh and cryopreserved amniotic condition medium during 24 h and cancer cell viability was determined by MTT assay. To evaluate angiogenesis, the rat aorta ring assay was performed for both fresh and cryopreserved AM within 7 days. In addition, four anti-angiogenic factors Tissue Inhibitor of Matrix Metalloproteinase-1 and 2 (TIMP-1 and TIMP-2), Thrombospondin, and Endostatin were measured by ELISA assay before and after cryopreservation. The results showed that the viability of cultured cancer cells dose-dependently decreased after treatment with condition medium of fresh and cryopreserved tissue and no significant difference was observed between the fresh and cryopreserved AM. The results revealed that the amniotic epithelial stem cells inhibit the penetration of fibroblast-like cells and angiogenesis. Moreover, the penetration of fibroblast-like cells in both epithelial and mesenchymal sides of fresh and cryopreserved AM was observed after removing of epithelial cells. The cryopreservation procedure significantly decreased anti-angiogenic factors TIMP-1, TIMP-2, Thrombospondin, and Endostatin which shows that angio-modulatory property is not fully dependent on proteomic and metabolomic profiles of the AM. These promising results demonstrate that cancer cell death induction and anti-angiogenic properties of the AM were maintained within cryopreservation; a procedure which can circumvent limitations of the fresh AM.