A Novel Nanocomposite Scaffold Based on Polyurethane (PU) Containing Cobalt Nanoparticles (CoNPs) for Bone Tissue Engineering Applications.

BACKGROUND: Bone tissue engineering, as a relatively new approach, has focused on combining biodegradable scaffolds, cells, and biologically active molecules for the recovery of different damaged tissues, such as bone defects. Polyurethane (PU), as a synthetic polymer, benefits from a porous structure which impersonates bone's natural environment. However, PU lacks osteoinduction activities. Cobalt nanoparticles (CoNPs) stimulate angiogenesis and biomineralization, which greatly favors osteogenesis. METHODS: Here, we designed a novel scaffold based on PU and combined it with CoNPs for bone regeneration applications. The composition and structure of PU-CoNPs nanocomposite were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). MTT and AO data showed biocompatibility and enhanced viability and proliferation of fibroblasts on PU-CoNPs scaffold. Ascorbic acid-2-phosphate, ß-glycerophosphate, and dexamethasone-induced osteogenesis for 14 days. RESULTS: The alkaline phosphatase test asserts the increased mineralization of hADSCs cultured on PUCoNPs compared to pure PU scaffold. Further, the results disclosed an elevated osteogenic differentiation at the level of genes and proteins using immunocytochemical analysis (ICC) and quantitative real-time PCR (qPCR). CONCLUSION: These findings provide an evidence that PU-CoNPs nanocomposite might be a promising candidate for bone repair applications.

Nanofibers in Respiratory Masks: An Alternative to Prevent Pathogen Transmission.

Recent global outbreak of COVID-19 has raised serious awareness about our abilities to protect ourselves from hazardous pathogens and volatile organic compounds. Evidence suggests that personal protection equipment such as respiratory masks can radically decrease rates of transmission and infections due to contagious pathogens. To increase filtration efficiency without compromising breathability, application of nanofibers in production of respiratory masks have been proposed. The emergence of nanofibers in the industry has since introduced a next generation of respiratory masks that promises improved filtration efficiency and breathability via nanometric pores and thin fiber thickness. In addition, the surface of nanofibers can be functionalized and enhanced to capture specific particles. In addition to conventional techniques such as melt-blown, respiratory masks by nanofibers have provided an opportunity to prevent pathogen transmission. As the surge in global demand for respiratory masks increases, herein, we reviewed recent advancement of nanofibers as an alternative technique to be used in respiratory mask production.

Decontamination Assessment of Nanofiber-based N95 Masks.

As the world battles with the outbreak of the novel coronavirus, it also prepares for future global pandemics that threaten our health, economy, and survivor. During the outbreak, it became evident that use of personal protective equipment (PPE), specially face masks, can significantly slow the otherwise uncontrolled spread of the virus. Nevertheless, the outbreak and its new variants have caused shortage of PPE in many regions of the world. In addition, waste management of the enormous economical and environmental footprint of single use PPE has proven to be a challenge. Therefore, this study advances the theme of decontaminating used masks. More specifically, the effect of various decontamination techniques on the integrity and functionality of nanofiber-based N95 masks (i.e. capable of at least filtering 95% of 0.3 µm aerosols) were examined. These techniques include 70% ethanol, bleaching, boiling, steaming, ironing as well as placement in autoclave, oven, and exposure to microwave (MW) and ultraviolet (UV) light. Herein, filtration efficiency (by Particle Filtration Efficiency equipment), general morphology, and microstructure of nanofibers (by Field Emission Scanning Electron microscopy) prior and after every decontamination technique were observed. The results suggest that decontamination of masks with 70% ethanol can lead to significant unfavorable changes in the microstructure and filtration efficiency (down to 57.33%) of the masks. In other techniques such as bleaching, boiling, steaming, ironing and placement in the oven, filtration efficiency dropped to only about 80% and in addition, some morphological changes in the nanofiber microstructure were seen. Expectedly, there was no significant reduction in filtration efficiency nor microstructural changes in the case of placement in autoclave and exposure to the UV light. It was concluded that, the latter methods are preferable to decontaminate nanofiber-based N95 masks.

A new nanocomposite scaffold based on polyurethane and clay nanoplates for osteogenic differentiation of human mesenchymal stem cells in vitro.

Bone tissue engineering as an alternative strategy, provides a great opportunity for regeneration of large bone tissue lesions. The use of biodegradable porous scaffolds along with stem cells, cytokines and growth factors improves cell survival, adhesion, proliferation and differentiation. In the present study, clay nanoplates (CNPs) were surface-modified (MCNPs) using phosphoric acid and calcium hydroxide, then porous polyurethane (PU) scaffolds and PU-MCNPs nanocomposite scaffolds were synthesized using solvent evaporation-dissolution technique. Physicochemical and morphological properties of scaffolds and MCNPs were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, thermal behavior of scaffolds was assessed by differential scanning calorimetry (DSC). Degradability, water uptake and mechanical behaviors of scaffolds were evaluated and hydrophilicity properties of them were obtained by contact angle technique. MTT assay and Acridine Orange/Ethidium Bromide (AO/EB) staining were used to assess the biocompatibility of MCNPs and PU scaffolds regarding cell attachment and proliferation support. Osteogenic differentiation of cultured human adipose derived mesenchymal stem cells (hADSCs) on MCNPs, PU and PU-MCNPs scaffolds was evaluated using common osteogenic markers such as alkaline phosphatase (ALP) activity, calcium content assay, Alizarin Red staining, immunocytochemical analysis (ICC) and quantitative real-time PCR (qPCR). According to the results, the surface modification of CNPs and their presence into the PU scaffolds significantly enhanced proliferation and osteogenic differentiation of hADSCs. These results were obtained by higher ALP enzyme activity, biomineralization and expression of osteogenic related proteins and genes in differentiated hADSCs on PU-MCNPs scaffolds. In conclusion, our results revealed that these biocompatible nanocomposites porous scaffolds with proper cell adhesion and proliferation as well as effective osteogenic differentiation and which are able to provide a new and useful matrix for bone tissue engineering purposes.

Neural differentiation of human induced pluripotent stem cells on polycaprolactone/gelatin bi-electrospun nanofibers.

In the present study, for the first time, polycaprolactone (PCL) and gelatin (GEL) were used for neural differentiation of human induced pluripotent stem cells (hiPSCs) in the form of bi-electrospun nanofibers. The electrospun fibers were evaluated by FTIR and tensile analysis. MTT assay was used to evaluate the toxicity on the scaffolds. The hiPSCs were seeded on the fibers and after 14days in neural differentiation medium. To confirm the differentiation, real-time PCR and immunocytochemistry (ICC) analyses were performed. For morphological studies of fibers and cultured cells on them, scanning electron microscopy (SEM) and optical microscopy (OM) were used. Our results indicated that hiPSCs had differentiated to neural cells completely after incubation time. Our study demonstrates that PCL/GEL bi-electrospun nanofibers not only have the capability to support hiPSCs differentiation to neural cells, but they also are able to enhance and improve such process. Overall, PCL/GEL scaffolds seem to be a feasible, reliable and easily accessed composite for further tissue engineering experiments.