Particulate-reinforced titanium composites for orthopaedic implants

In the present study, to enhance the strength of porous pure titanium scaffolds with high porosity, new particulate-reinforced Ti-based composites with the addition of biocompatible oxide particles such as TiO₂, SiO₂, ZrO₂ and Nb₂O₅ were prepared using a powder metallurgical method. The strengths of the new particulate-reinforced titanium composites were found to be significantly higher than that of pure titanium with an excellent biocompatibility. SaOS-2 osteoblast-like cells grew and spread well on the surfaces of the new particulate-reinforced titanium composites. The present study illustrated the feasibility of using the particulate-reinforced titanium composites as an orthopaedic implant material.

Efflux pumps of Mycobacterium tuberculosis play a significant role in antituberculosis activity of potential drug candidates

Active efflux of drugs mediated by efflux pumps that confer drug resistance is one of the mechanisms developed by bacteria to counter the adverse effects of antibiotics and chemicals. To understand these efflux mechanisms in Mycobacterium tuberculosis, we generated knockout (KO) mutants of four efflux pumps of the pathogen belonging to different classes. We measured the MICs and kill values of two different compound classes on the wild type (WT) and the efflux pump (EP) KO mutants in the presence and absence of the efflux inhibitors verapamil and L-phenylalanyl-L-arginyl-β-naphthylamide (PAβN). Among the pumps studied, the efflux pumps belonging to the ABC (ATP-binding cassette) class, encoded by Rv1218c, and the SMR (small multidrug resistance) class, encoded by Rv3065, appear to play important roles in mediating the efflux of different chemical classes and antibiotics. Efflux pumps encoded by Rv0849 and Rv1258c also mediate the efflux of these compounds, but to a lesser extent. Increased killing is observed in WT M. tuberculosis cells by these compounds in the presence of either verapamil or PAβN. The efflux pump KO mutants were more susceptible to these compounds in the presence of efflux inhibitors. We have shown that these four efflux pumps of M. tuberculosis play a vital role in mediating efflux of different chemical scaffolds. Inhibitors of one or several of these efflux pumps could have a significant impact in the treatment of tuberculosis. The identification and characterization of Rv0849, a new efflux pump belonging to the MFS (major facilitator superfamily) class, are reported.

Crosslinking neat ultrathin films and nanofibres of pH-responsive poly(acrylic acid) by UV radiation

Electrospun polyelectrolyte hydrogel nanofibres are being developed for many applications including artificial muscles, scaffolds for tissue engineering, wound dressings and controlled drug release. For electrospun polyelectrolytes, a post-spinning crosslinking process is necessary for producing a hydrogel. Typically, radiation or thermal crosslinking routines are employed that require multifunctional crosslinking molecules and crosslink reaction initiators (free radical producers). Here, ultraviolet subtype-C (UVC) radiation was employed to crosslink neat poly(acrylic acid) (PAA) nanofibres and films to different crosslink densities. Specific crosslink initiators or crosslinking molecules are not necessary in this fast and simple process providing an advantage for biological applications. Scanning probe microscopy was used for the first time to measure the dry and wet dimensions of hydrogel nanofibres. The diameters of the swollen fibres decrease monotonically with increasing UVC radiation time. The fibres could be reversibly swollen/contracted by treatment with solutions of varying pH, demonstrating their potential as artificial muscles. The surprising success of UVC radiation exposure to achieve chemical crosslinks without a specific initiator molecule exploits the ultrathin dimensions of the PAA samples and will not work with relatively thick samples.

Self-assembled peptides : characterisation and in vivo response

The fabrication of tissue engineering scaffolds is a well-established field that has gained recent prominence for the in vivo repair of a variety of tissue types. Recently, increasing levels of sophistication have been engineered into adjuvant scaffolds facilitating the concomitant presentation of a variety of stimuli (both physical and biochemical) to create a range of favourable cellular microenvironments. It is here that self-assembling peptide scaffolds have shown considerable promise as functional biomaterials, as they are not only formed from peptides that are physiologically relevant, but through molecular recognition can offer synergy between the presentation of biochemical and physio-chemical cues. This is achieved through the utilisation of a unique, highly ordered, nano- to microscale 3-D morphology to deliver mechanical and topographical properties to improve, augment or replace physiological function. Here, we will review the structures and forces underpinning the formation of self-assembling scaffolds, and their application in vivo for a variety of tissue types.

Replication of hematopoietic stem cell niche

This thesis models the hematopoietic stem cell (HSC) niche by using decellularized extracellular matrix (ECM) scaffolds prepared by MS-5 cell line. The ECM replicates many of the properties of HSC niches in vivo, providing insights into expansion of HSCs that may have several applications in translational medicine.

Fabrication of Ti14Nb4Sn alloys for bone tissue engineering applications

In this paper, porous Ti14Nb4Sn alloys were fabricated using a space holder sintering method, resulting in a porosity of ~70%. Scanning electron microscopy (SEM) analyses revealed a combination of both macropore and micropore structures. The fabricated titanium alloy scaffolds exhibited a similar structure to that of natural bone, which is expected to improve bone implant longevity. Bacterial cells of Pseudomonas aeruginosa ATCC 9027 were employed for the in vitro test.

Diamond Dialogue method for the evaluation of personal well-being after a maternal health intervention in Lao PDR

This paper follows the genesis of an evolving tool to measure the impact of development interventions on personal well-being in non-literate and non-numerate communities. The Diamond Dialogue was adapted to evaluate the impact on women of the establishment of 17 one stop maternity waiting home/health promotion/income generating centres (Silk Homes) in Southern Lao PDR. The tool elicited data not accessible by research methods which assume literacy and numeracy and revealed that 86% of women who used the Silk Homes experienced substantial improvements in quality of life. The Diamond Dialogue can be modified to assess the outcomes of development interventions in a myriad of contexts.

A controllable simple method for production of polymeric nanofiberous composite via single nozzle jet electrospinning

A special Micro-Nano fiberous composite structure composed of nano- and micro-scale fiber of Polycaprolactone (PCL) and Gelatin produced by using single nozzle electrospinning instrument. By controlling the solution (polymer concentration and polymer composition percent) and processing parameters of electrospinning (feed rate and electrostatic field), different portion of nano and micro fibers in the structure is achieved. This method can result a one-stage method of fabrication of Micro-Nano fiberous composite structure instead of previously used twostage process or using additional facility to produce structure near-similar to this composite structure. The resulting materials finely mingle nano- and micro fibers together, rather than simply juxtaposing them, as is commonly found in the literature. The results obtained from SEM, Flow Porosimetry, and DMA led the authors to confirm that the structure has very versatile and improved properties for many applications like cell culture scaffolds. These favourable mechanical and structural properties can provide easier opening of spaces for cell penetration to deeper levels of the scaffold and withstand to tensions during to clinical handling.

The application of Cd Se/ZnS quantum dots and confocal laser scanning microscopy for three-dimensional imaging of nanfibrous structures

This paper reports a fast, accurate, and non-destructive three-dimensional imaging approach based on using quantum dots and confocal laser scanning microscopy to get three-dimensional images of internal pore structure of the nanofibrous materials. A practical method of making the fiber fluorescent using quantum dots was applied before three-dimensional imaging by confocal laser scanning microscopy. Fibrous scaffolds with different porosity parameters produced by electrospinning and their three-dimensional pore structure was evaluated by this approach. Furthermore, the introduced approach can be used to measure the pore interconnectivity of the scaffold

Positron annihilation lifetime spectroscopy of mechanically milled protein fibre powders and their free volume aspects

The present study reports the fabrication of ultra-fine powders from animal protein fibres such as cashmere guard hair, merino wool and eri silk along with their free volume aspects. The respectively mechanically cleaned, scoured and degummed cashmere guard hair, wool and silk fibres were converted into dry powders by a process sequence: Chopping, Attritor Milling, and Spray Drying. The fabricated protein fibre powders were characterised by scanning electron microscope, particle size distribution and positron annihilation lifetime spectroscopy (PALS). The PALS results indicated that the average free volume size in protein fibres increased on their wet mechanical milling with a decrease in the corresponding intensities leading to a resultant decrease in their fractional free volumes.

Wild silkworm cocoon as a natural tough biological composite structure

Silk cocoons are biological composites with intriguing characteristics that have evolved through a long natural selection process. Knowledge of structure-property-function relationship of multilayered composite silk cocoon shells gives insight into the design of next-generation protection materials. The current investigation studied the composite structure and mechanical performance of a wild silkworm cocoon (Chinese tussah silkworm cocoon, Antheraea pernyi) in comparison with the domestic counterpart (Mulberry silkworm cocoon, Bombyx mori). 180º peel and tensile tests were performed on the cocoon walls to understand both their interlaminar and in-plane mechanical properties. The fracture surfaces were investigated under SEM. The wild cocoon showed substantially higher toughness over the domestic cocoon, which explains their unique capability to tackle severe environmental adversaries.

Tuning the amino acid sequence of minimalist peptides to present biological signals via charge neutralised self assembly

Nanofibrous materials yielded by the self-assembly of peptides are rich in potential; particularly for the formation of scaffolds that mimic the landscape of the host environment of the cell. Here, we report a novel methodology to direct the formation of supramolecular structures presenting desirable amino acid sequences by the self-assembly of minimalist peptides which cannot otherwise yield the desired scaffold structures under biologically relevant conditions. Through the rational modification of the pK?, we were able to optimise ordered charge neutralised assembly towards in vivo conditions.

Tri-component bio-composite materials prepared using an eco-friendly processing route

We report on the blending of three natural polymers, raw cotton, silk and wool, using ionic liquids as the dissolving media. We find that with increased content of wool and silk the thermal degradation temperature of the new bio films increases. This is due to an increase in the hydrogen bond network between the blended polymers. We also investigated the role of the coagulating solvent by coagulating the bio films using water, methanol or isopropanol. Again, we find the coagulating solvent impacts the final properties of the bio films with water shown to coagulated films with the best material properties.