Directing cell migration and organization via nanocrater-patterned cell-repellent interfaces.

Although adhesive interactions between cells and nanostructured interfaces have been studied extensively, there is a paucity of data on how nanostructured interfaces repel cells by directing cell migration and cell-colony organization. Here, by using multiphoton ablation lithography to pattern surfaces with nanoscale craters of various aspect ratios and pitches, we show that the surfaces altered the cells focal-adhesion size and distribution, thus affecting cell morphology, migration and ultimately localization. We also show that nanocrater pitch can disrupt the formation of mature focal adhesions to favour the migration of cells towards higher-pitched regions, which present increased planar area for the formation of stable focal adhesions. Moreover, by designing surfaces with variable pitch but constant nanocrater dimensions, we were able to create circular and striped cellular patterns. Our surface-patterning approach, which does not involve chemical treatments and can be applied to various materials, represents a simple method to control cell behaviour on surfaces

Porous Titanium Cylinders Obtained by the Freeze-Casting Technique: Influence of Process Parameters on Porosity and Mechanical Behavior

 The discrepancy between the stiffness of commercially pure titanium and cortical bone  tissue compromises its success as a biomaterial. The use of porous titanium has been widely studied,  however, it is still challenging to obtain materials able to replicate the porous structure of the bones  (content, size, morphology and distribution). In this work, the freeze‐casting technique is used to  manufacture cylinders with elongated porosity, using a home‐made and economical device. The  relationship between the processing parameters (diameter and material of the mold, temperature  gradient), microstructural features and mechanical properties is established and discussed, in terms  of ensuring biomechanical and biofunctional balance. The cylinders have a gradient porosity  suitable for use in dentistry, presenting higher Young’s modulus at the bottom, near the cold spot  and, therefore better mechanical resistance (it would be in contact with a prosthetic crown), while  the opposite side, the hot spot, has bigger, elongated pores and walls.  Ministry of Economy and Competitiveness of Spain  grant  MAT2015‐71284‐P  FEDER‐Junta de Andalucía Research  Project (Modeling and implementation of the freeze casting technique: gradients of porosity with a tribomechanical equilibrium and electro‐stimulated cellular behavior).

Preservation of biomaterials and cells by freeze-drying : Change of paradigm

Freeze-drying is the most widespread method to preserve protein drugs and vaccines in a dry form facilitating their storage and transportation without the laborious and expensive cold chain. Extending this method for the preservation of natural biomaterials and cells in a dry form would provide similar benefits, but most results in the domain are still below expectations. In this review, rather than consider freeze-drying as a traditional black box we "break it" through a detailed process thinking approach. We discuss freeze-drying from process thinking aspects, introduce the chemical, physical, and mechanical environments important in this process, and present advanced biophotonic process analytical technology. In the end, we review the state of the art in the freezedrying of the biomaterials, extracellular vesicles, and cells. We suggest that the rational design of the experiment and implementation of advanced biophotonic tools are required to successfully preserve the natural biomaterials and cells by freeze-drying. We discuss this change of paradigm with existing literature and elaborate on our perspective based on our new unpublished results.Peer reviewe

Investigation of the performance of articular cartilage and synthetic biomaterials in multi-directional sliding motion as in orthopedic implants

The performance of several synthetic biomaterials and bovine articular cartilage were investigated in terms of their suitability for use as articulating surfaces in artificial joints. The Dual-Axis Wear Simulator (DAWS), a wear testing machine that simulates conditions in a synovial joint, was designed and fabricated to enable investigators to measure the wear of such materials in multi-directional sliding while immersed in a bovine serum lubricant solution. This machine was used initially to determine the wear mechanisms and wear amounts of ultra-high molecular weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE), polyoxymethylene (POM), and the compliant elastomer Pellethane(TM) 2363-80A. It was found that the compliant material produced lower wear. Dynamic mechanical analysis was used to determine that bovine articular cartilage had a very significant amount of viscoelasticity to support static loads and damp impact loads. Furthermore, the use of a compliant counterface led to lower wear in the cartilage as compared to a rigid counterface. Pt-Zr quasicrystals were used as fillers in UHMWPE, and the wear, stiffness, and impact toughness of the filled polymer were shown to be comparable or better than those of UHMWPE that had been irradiation crosslinked. Crosslinked UHMWPE was investigated for its susceptibility to oxidative degradation and increased wear. It was found that thermal stabilization of the polymer could be eliminated if a mild amount crosslinking was used. Furthermore, there was no degradation in wear resistance of mildly crosslinked and non-stabilized UHMWPE even after accelerated aging. Based on the results of this work and lessons learned about compliance and wear resistance, blends were produced by using surface-activated UHMWPE particles as fillers in elastomeric PUR. The blends showed better wear resistance than UHMWPE, as well as increased stiffness and damping over PUR. The results of this work indicated that there is great potential for the development of new biomaterials and materials treatment methods to produce more durable articulating components in artificial joints

Three-dimensional tissue scaffolds from interbonded poly(e-caprolactone) fibrous matrices with controlled porosity

In this article, we report on the preparation and cell culture performance of a novel fibrous matrix that has an interbonded fiber architecture, excellent pore interconnectivity, and controlled pore size and porosity. The fibrous matrices were prepared by combining melt-bonding of short synthetic fibers with a template leaching technique. The microcomputed tomography and scanning electron microscopy imaging verified that the fibers in the matrix were highly bonded, forming unique isotropic pore architectures. The average pore size and porosity of the fibrous matrices were controlled by the fiber/template ratio. The matrices having the average pore size of 120, 207, 813, and 994 mm, with the respective porosity of 73%, 88%, 96%, and 97%, were investigated. The applicability of the matrix as a three-dimensional (3D) tissue scaffold for cell culture was demonstrated with two cell lines, rat skin fibroblast and Chinese hamster ovary, and the influences of the matrix porosity and surface area on the cell culture performance were examined. Both cell lines grew successfully in the matrices, but they showed different preferences in pore size and porosity. Compared with two-dimensional tissue culture plates, the cell number on 3D fibrous matrices was increased by 97.27% for the Chinese hamster ovary cells and 49.46% for the fibroblasts after 21 days of culture. The fibroblasts in the matrices not only grew along the fiber surface but also bridged among the fibers, which was much different from those on two-dimensional scaffolds. Such an interbonded fibrous matrix may be useful for developing new fiber-based 3D tissue scaffolds for various cell culture applications