Experimental investigation and finite element modelling of PMMA/carbon nanotube nanobiocomposites for bone cement applications.

Multi-walled carbon nanotubes (MWCNTs) are one of the preferred candidates for reinforcing polymeric nanobiocomposites, such as acrylic bone type of cement. In this study, at first, bulk samples of the reinforced polymethylmethacrylate (PMMA) matrix were prepared with 0.1, 0.25, and 0.5 wt per wt% of MWCNTs by the casting method. Tensile and three-point bending tests were performed to determine the essential mechanical properties of bone cement, such as tensile and bending strengths. The tensile fracture surfaces were investigated by scanning electron microscopy (SEM). The commercial software (Abaqus) was used to conduct finite element analysis (FEA) by constructing a representative volume element (RVE) model for numerically computing the tensile and bending parameters of PMMA-MWCNT nanocomposites. Finally, MTT assays were utilized to evaluate the cell viability on the surface of nanobiocomposites. The results show that by increasing the MWCNT amount in the PMMA-based cement, the bending strengths (BS), tensile strength (TS), and elastic modulus (EM) increased considerably. Furthermore, the disparity between the FEA and experimental TS, EM, and BS values was less than 20%. According to MTT viability experiments, adding MWCNTs to PMMA had no influence on PMMA toxicity and resulted in a negative response to interaction with mesenchymal stem cells. The cell density on the nanobiocomposite was more than pristine-PMMA.

Fabrication and characterization of gold nanoparticle-doped electrospun PCL/chitosan nanofibrous scaffolds for nerve tissue engineering.

In the field of nerve tissue engineering, nanofibrous scaffolds could be a promising candidate when they are incorporated with electrical cues. Unique physico-chemical properties of gold nanoparticles (AuNPs) make them an appropriate component for increasing the conductivity of scaffolds to enhance the electrical signal transfer between neural cells. The aim of this study was fabrication of AuNPs-doped nanofibrous scaffolds for peripheral nerve tissue engineering. Polycaprolactone (PCL)/chitosan mixtures with different concentrations of chitosan (0.5, 1 and 1.5) were electrospun to obtain nanofibrous scaffolds. AuNPs were synthesized by the reduction of HAuCl4 using chitosan as a reducing/stabilizing agent. A uniform distribution of AuNPs with spherical shape was achieved throughout the PCL/chitosan matrix. The UV-Vis spectrum revealed that the amount of gold ions absorbed by nanofibrous scaffolds is in direct relationship with their chitosan content. Evaluation of electrical property showed that inclusion of AuNPs significantly enhanced the conductivity of scaffolds. Finally, after 5 days of culture, biological response of Schwann cells on the AuNPs-doped scaffolds was superior to that on as-prepared scaffolds in terms of improved cell attachment and higher proliferation. It can be concluded that the prepared AuNPs-doped scaffolds can be used to promote peripheral nerve regeneration.

Effect of surface modification on physical and cellular properties of PCL thin film.

Lack of suitable surface functional groups is one of the main limitations related to the cell attachment of Polycaprolactone (PCL). The aim of this research was to surface modify the PCL film using gelatin coating, via a simple physical entrapment process. In this regard, after preparation of PCL films using casting, they were immersed in each gelatin solutions. Consequently, chemical crosslinking using glutaraldehyde was performed to improve the stability of the PCL-gelatin film. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Scanning electron microscope (SEM), contact angle measurement, strip tensile test, Dimethylthiazol-diphenyltetrazolium bromide (MTT) assay and Cell seeding were used to evaluate the quality of the coating layer, the thickness of PCL-gelatin film, the surface wettability, their mechanical properties, Cell viability and Cell attachment and proliferation respectively. Results showed that the amount of entrapped gelatin enhanced with increasing acetone in the gelatin solution. Surface modification led to a two-fold increment of mechanical strength, about 50% increase in elastic modulus, 54% in elongation and up to 11% increment in cell viability. Moreover, wettability and cell attachment of PCL film significantly enhanced, after gelatin modification. In conclusion, the simple and cost effective modification of PCL using gelatin entrapment could provide significant mechanical and biological properties making it a promising approach for development of three-dimensional scaffolds for bone tissue engineering.

Bioinspired Device Improves The Cardiogenic Potential of Cardiac Progenitor Cells.

OBJECTIVE: Functional cardiac tissue engineering holds promise as a candidate approach for myocardial infarction. Tissue engineering has emerged to generate functional tissue constructs and provide an alternative means to repair and regenerate damaged heart tissues. MATERIALS AND METHODS: In this experimental study, we fabricated a composite polycaprolactone (PCL)/gelatine electrospun scaffold with aligned nanofibres. The electrospinning parameters and optimum proportion of the PCL/ gelatine were tested to design a scaffold with aligned and homogenized nanofibres. Using scanning electron microscopy (SEM) and mechanophysical testes, the PCL/gelatine composite scaffold with a ratio of 70:30 was selected. In order to simulate cardiac contraction, a developed mechanical loading device (MLD) was used to apply a mechanical stress with specific frequency and tensile rate to cardiac progenitor cells (CPCs) in the direction of the aligned nanofibres. Cell metabolic determination of CPCs was performed using real-time polymerase chain reaction(RT-PCR). RESULTS: Physicochemical and mechanical characterization showed that the PCL/gelatine composite scaffold with a ratio of 70:30 was the best sample. In vitro analysis showed that the scaffold supported active metabolism and proliferation of CPCs, and the generation of uniform cellular constructs after five days. Real-time PCR analysis revealed elevated expressions of the specific genes for synchronizing beating cells (MYH-6, TTN and CX-43) on the dynamic scaffolds compared to the control sample with a static culture system. CONCLUSION: Our study provides a robust platform for generation of synchronized beating cells on a nanofibre patch that can be used in cardiac tissue engineering applications in the near future.

Biodegradable MRI Visible Drug Eluting Stent Reinforced by Metal Organic Frameworks.

Metal-organic frameworks (MOFs) have applications in numerous fields. However, the development of MOF-based "theranostic" macroscale devices is not achieved. Here, heparin-coated biocompatible MOF/poly(ε-caprolactone) (PCL) "theranostic" stents are developed, where NH2 -Materials of Institute Lavoisier (MIL)-101(Fe) encapsulates and releases rapamycin (an immunosuppressive drug). These stents also act as a remarkable source of contrast in ex vivo magnetic resonance imaging (MRI) compared to the invisible polymeric stent. The in vitro release patterns of heparin and rapamycin respectively can ensure a type of programmed model to prevent blood coagulation immediately after stent placement in the artery and stenosis over a longer term. Due to the presence of hydrolysable functionalities in MOFs, the stents are shown to be highly biodegradable in degradation tests under various conditions. Furthermore, there is no compromise of mechanical strength or flexibility with MOF compositing. The system described here promises many biomedical applications in macroscale theranostic devices. The use of MOF@PCL can render a medical device MRI-visible while simultaneously acting as a carrier for therapeutic agents.

Antibiotics drug release controlling and osteoblast adhesion from Titania nanotubes arrays using silk fibroin coating.

Bacterial infection, wide inflammation, and osteoporosis are the most common factors in the failure of orthopedic implants. The present study aims to design an orthopedic implant based on Titania nanotubes (TiO2-NTs) which not only have a high biocompatibility but also are characterized by anti-bacterial property. In order to improve the osseointegration of the TiO2-NTs structures (110-120 nm in diameter, 40 µm in length), they were used to coat the Titania implant by electrochemical anodizing. Vancomycin, which is soluble in water, was loaded as a main clinical drug to control intensive infections caused by positive gram bacteria. For the first time, Silk Fibroin (SF) Nanofibers coating was used to control drug release by the implementation of electrospinning on the TiO2-NTs surface. In order to investigate the anti-bacterial activities, S. aureus bacterium culture test was used. The cell culture of MG63 was conducted for both coated and non-coated samples of TiO2-NTs. The results showed that the SF Nanofibers coating not only controls the drug being freely released from TiO2-NTs but also effects adhesion and development of osteoblast cells. In this regard, this coating inhibits biofilm formation and development, as well as bacteria colonization due to anti-bacterial drug release. Therefore, this system can be considered as a promising alternative for orthopedic implants, preventing bone infection, osteomyelitis, bone cancer treatment, and other orthopedic diseases.