Evaluation of particle recovery from microalgae

Coccoliths are micro-structured biomineral particles found in cell protective covering layers of coccolithophore species. They are mainly composed of CaCO₃ and their individual crystal entities are arranged in such a way that they construct complex and unique structures. This complexity is found down to the individual particle level and appears to have promising properties to offer. This study focuses on the essential step prior to any kind of implementation, which is the recovery of the material. It summarizes cleaning protocols found in literature, compares them for the first time for the same freshly cultivated material and addresses challenges that still need to be overcome. Further, it highlight the advantages and disadvantages of the best cleaning protocols, suggests optimizations with promising results and uses size distribution measurements to analyse the recovery efficiency. To that end, further characterization techniques, new for coccoliths, are introduced and used to improve our current knowledge of the particles behaviour.     

A microfluidic approach for development of hybrid collagen-chitosan extracellular matrix-like membranes for on-chip cell cultures

To advance organ-on-a-chip development and other areas befitting from physiologically-relevant biomembranes,a microfluidic platform is presented for synthesis of biomembranes during gelation and investigation into their role as extracellular matrix supports.In this work,high-throughput studies of collagen,chitosan,and collagen-chitosan hybrid biomembranes were carried out to characterize and compare key properties as a function of the applied hydrodynamic conditions during gelation.Specifically,depending on the biopolymer material used,varying flow conditions during biomembrane gelation caused width,uniformity,and swelling ratio to be differently affected and controllable.Finally,cell viability studies of seeded fibroblasts were conducted,thus showing the potential for biological applications.     

Controlling Corrosion Resistance of a Biodegradable Mg–Y–Zn Alloy with LPSO Phases via Multi-pass ECAP Process

Mg-RE(rear earth) alloys with long period stacking(LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y_1 Zn_(0.5) alloys with 18 R LPSO structure after equal channel angular pressing(ECAP). The results showed that the ECAP process changed the grain size and the distribution of LPSO particles thus controlled the total corrosion rates of Mg 98.5 Y_1 Zn_(0.5) alloys. During the ECAP process from 0 p to 12 p, the grain size reduced from 160–180 μm(as-cast) to 6–8 μm(12 p). The LPSO structures became kinked(4 p), then started to be broken into smaller pieces(8 p), and at last comminuted to fine particles and redistributed uniformly inside the matrix(12 p). The improvement in the corrosion resistance for ECAP samples was obtained from 0 p to 8 p, with the corrosion rate reduced from 3.24 mm/year(0 p) to 2.35 mm/year(8 p) in simulated body fluid, and the 12 p ECAP alloy exhibited the highest corrosion rate of 4.54 mm/year.     

Current advances concerning the most cited metal ions doped bioceramics and silicate-based bioactive glasses for bone tissue engineering

Studies related to biomaterials that stimulate the repair of living tissue have increased considerably, improving the quality of many people's lives that require surgery due to traumatic accidents, bone diseases, bone defects, and reconstructions. Among these biomaterials, bioceramics and bioactive glasses (BGs) have proved to be suitable for coating materials, cement, scaffolds, and nanoparticles, once they present good biocompatibility and degradability, able to generate osteoconduction on the surrounding tissue. However, the role of biomaterials in hard tissue engineering is not restricted to a structural replacement or for guiding tissue regeneration. Nowadays, it is expected that biomaterials develop a multifunctional role when implanted, orchestrating the process of tissue regeneration and providing to the body the capacity to heal itself. In this way, the incorporation of specific metal ions in bioceramics and BGs structure, including magnesium, silver, strontium, lithium, copper, iron, zinc, cobalt, and manganese are currently receiving enhanced interest as biomaterials for biomedical applications. When an ion is incorporated into the bioceramic structure, a new category of material is created, which has several unique properties that overcome the disadvantages of primitive material and favors its use in different biomedical applications. The doping can enhance handling properties, angiogenic and osteogenic performance, and antimicrobial activity. Therefore, this review aims to summarize the effect of selected metal ion dopants into bioceramics and silicate-based BGs in bone tissue engineering. Furthermore, new applications for doped bioceramics and BGs are highlighted, including cancer treatment and drug delivery.     

Deepening our understanding of bioactive glass crystallization using TEM and 3D nano-CT

One key issue influencing a broader application of Bioglass 45S5 in tissue engineering is its inherent crystallization tendency, severely limiting the mechanical strength of 3D porous scaffolds. Despite numerous studies, Bioglass 45S5 crystallization is not yet fully understood with regard to the mechanisms involved or morphology of the crystal phases forming. Here we show how two cutting-edge imaging techniques, state-of-the-art transmission electron microscopy (TEM) with image correction including energy dispersive X-ray spectroscopy and X-ray nano-computed tomography (nano-CT), allowed us to visualize changes in microstructure from near-nucleation to almost full crystallization in bulk Bioglass 45S5. At early times of heat treatment at 660 °C the formation of phase-separated nano-droplets within the glassy matrix was observed. Later, besides surface crystallization, bulk crystallization of combeite spheres was predominant. The formation of the first combeite spheres, their coarsening with time and finally their merging at near full crystallization were recorded by in situ high-temperature optical microscopy videos. The 3D nature of these spheres was confirmed by nano-CT, while TEM showed that their internal structure was composed of sub-micron grains. X-ray diffraction analysis at early time points showed a much higher crystalline fraction in bulk samples compared to powder samples, highlighting the influence of processing and sample morphology. These results show the importance of using complementary techniques for gaining insight into the crystallization process in the volume. In addition, we show that TEM and nano-CT are suitable characterization techniques to visualize the crystallization even in fast crystallizing systems, such as bioactive glasses.     

Processing and mechanical properties of hydroxyapatite–polysulfone laminated composites

Designing biocomposites that mimic bone with specific mechanical properties of toughness and elastic modulus is a long-standing challenge in the biomaterials field. Traditional biocomposites comprise polymer matrices reinforced with ceramic particles. Laminated composites are structures also found in nature that can offer improved mechanical properties such as strength, elastic modulus and toughness. Hydroxyapatite/polysulfone laminated composites were fabricated to develop biologically compatible, toughened composites that would match the elastic modulus of bone. Multilayered composites were successfully designed with improved toughness measured by the work of fracture. Toughness measurements were more than an order of magnitude greater than monolithic hydroxyapatite. The toughness and modulus values of hydroxyapatite/polysulfone were within the range of cortical bone.     

Fabrication and Characterization of Nanopillar-Like HA Coating on Porous Ti6Al4V Scaffold by a Combination of Alkali–Acid-Heat and Hydrothermal Treatments

Porous titanium scaffold with suitable porous architecture exhibits enormous potentials for bone defect repairs. However,insufficient osteointegration and osteoinduction still remain to open as one of the major problems to achieve satisfactory therapeutic effect. To solve this problem, many studies have been carried out to improve the bioactivity of porous titanium scaff old by surface modifications. In this study, porous Ti6Al4V scaff olds were fabricated using additive manufacturing technique. Porous architectures were built up based on a diamond pore structure unit. Alkali–acid-heat(AH) treatment was applied to create a TiO_2 layer on the porous Ti6Al4V scaff old(AH-porous Ti6Al4V). Subsequently, a hydrothermal treatment was employed to enable the formation of HA coating with nanopillar-like morphology on the alkali–acid-heat-treated surface(HT/AH-porous Ti6Al4V). The effects of surface modifications on apatite-forming ability, protein adsorption,cell attachment, cell proliferation and osteogenic gene expression were studied using apatite-forming ability test, protein adsorption assay and in vitro cell culture assay. It was found that the HT/AH-porous Ti6Al4V exhibited the highest apatite formation ability and best affinity to fibronectin and vitronectin. In vitro studies indicated that the mesenchymal stem cells(MSCs) cultured on the HT/AH-porous Ti6Al4V presented improved adhesion and differentiation compared with the porous Ti6Al4V and AH-porous Ti6Al4V.     

Application of polymeric nanofibers in medical designs,part IV: Drug and biological materials delivery

Nanotechnology has potential applications in different sciences, especially in the biological sciences and medicine. The development of nanofibers has greatly enhanced the scope for fabricating designs that can potentially use in medical sciences. Nanofibers mimic the porous topography of natural extracellular matrix, and are advantageous for tissue regeneration and also sustained release of encapsulated drug or growth factor. In part IV the author summarizes the currently available applications of nanofibers in drug and biological materials delivery.     

In vitro ageing and wear behaviour of ceria stabilized zirconia toughened alumina (CSZ-TA) bio-ceramic

15–25 wt% zirconia (stabilized with 14 mol% ceria) toughened alumina was synthesized by co-precipitation technique. The synthesized powders were calcined at different temperatures, compacted and conventionally sintered following two steps sintering process. Uniformly distributed submicron sized grains with Vickers' hardness value up to 1730±6HV20 were achieved after conventional sintering. In order to assess the ageing behaviour, samples were hydrothermally treated (in vitro) at 134 °C under 0.2 MPa in presence of simulated body fluid. Rietveld refinement of the X-ray diffraction patterns was carried out to estimate the phase content after calcination, sintering and after different stages of hydrothermal treatment. No significant phase change (only ∼3%) was observed even after 100 h of hydrothermal treatment. Very few bulged grains (resulted from the tetragonal to monoclinic phase transformation) on the surface and slight decrease in hardness value were observed after hydrothermal treatment. Fretting wear in dry condition was carried out taking ball on flat geometry for 10⁵ cycles at different loads before and after hydrothermal treatment. Wear volumes were directly estimated from the surface scanning of the wear scar using profilometer. Transition of wear and its related mechanisms at different loads along with the effect of ageing on wear were discussed.     

Prilling process applied to collagen solutions

Abstract

The present work concerns the preparation of microbeads of collagen by a prilling process.

Collagen is one of the main components of vertebrate proteins, especially in. such tissues as skin, tendons, placenta, … Furthermore, it has some properties which makes it interesting to use as a biomaterial: biocompatibility, biodegradability, high tensile strength, hemostatic power, participation to the wound healing.

The patented process which is developped in this paper combines two techniques :

? breaking of a capillary flow by prilling

and

? reticulation of collagen after oxydation with periodic acid.

It uses neither organic solvents, nor variation of temperature and allows the production of microbeads which can be utilized for many different medical applications.