[en] Nano-sized calcium deficient hydroxyapatite (CDHA) powders with an average particle size less than 100 nm were prepared by a co-precipitation method at low temperature. The initial Ca/P molar ratio was chosen to be less than the stoichiometric ratio of β-TCP (1.5). Additionally, lowering the temperature and pH values accelerated HPO₄^2- incorporation in the CDHA structure. HPO₄^2- is considered as an essential source for β-TCP formation. Sulfate ion doping during the maturation period is proved to be an effective step to eliminate the pyrophosphate P₂O₇^2- phase that results during the calcination of CDHA with Ca/P < 1.5. Furthermore, the heating effect of microwave irradiation resulted in an increase in Ca ion concentration and lowered the CDHA deficiency which affected β-TCP purity despite its ability to reduce the particle size. A purity of 99.32% β-TCP with respect to the P₂O₇^2- phase was achieved by increasing the sulfate ion concentration from 2% to 3% and the calcination temperatures from 900 deg. C to 1100 ⁰C

[en] Miniaturized fluidic systems have been developed in recent years and offer new and novel means of leveraging the domain of microfluidics for the development of micro-total analysis systems (μTAS). Initially, such systems employed closed microchannels in order to facilitate chip-based biochemical assays, requiring very small quantities of sample and/or reagents and furthermore providing rapid and low-cost analysis on a compact footprint. More recently, advancements in the domain of surface microfluidics have suggested that similar low volume sample handling and manipulation capabilities for bioassays can be attained by leveraging the phenomena of liquid dielectrophoresis and droplet dielectrophoresis (DEP), without the need for separate pumps or valves. Some of the key aspects of this surface microfluidic technology and its capabilities are discussed and highlighted in this paper. We, furthermore, examine the integration and utility of liquid DEP and droplet DEP in providing rapid and automated sample handling and manipulation capabilities on a compact chip-based platform

[en] A novel fabrication technique, a combination of slurry dipping and electrospraying, was used to produce hydroxyapatite foams as potential matrices for bone tissue engineering applications. In this study, scaffolds that were slurry dipped and electrosprayed for different time intervals were compared with foams prepared by the individual methods of dipping and electrospraying. Significant differences in the distribution of cracks on the struts, the strut thickness and porosity were observed on the sintered foams prepared under the varied conditions. All the sintered structures had average porosities in the range 84-94% and desirable pore interconnections, while the combined method produced foams of uniform pore distribution, thicker struts and improved mechanical properties. Further improvement of the mechanical properties has also been achieved by altering the sintering conditions

[en] There is an increasing demand for an affordable and easy-to-fabricate material to help patients having a long bone gap. In this paper, we describe the biomimetic synthesis of Hap-Gel in situ nanocomposite powders with varied proportions. Their biocompatibility and bone regeneration abilities were assessed on a rabbit model. The use of Hap crystals and Gel molecule, the soluble form of bone protein, makes the nanocomposites comparable to natural bone in constituents. The application of biomimetic principles improves crystal morphology and the interaction of Hap crystals with the Gel molecules as seen through in vitro characterizations. Out of the various compositions studied, one with 80:20 proportions of Hap to Gel proved to be closest to the characteristics of natural bone. The immunological response to this composite, assessed through intradermal inoculation, did not reveal any reaction. The in vivo implantation studies in the femoral condyle of the animals, as assessed by serial post-operative follow-up radiography and the histological evaluation, revealed a good biocompatibility and bone-regeneration ability of the material. Thus, nanocomposites of Hap-Gel have a great potential for serving as an effective and affordable biomaterial for bone grafting applications

[en] Interest in stimuli-responsive polymers is steadily gaining increasing momentum especially in the fields of controlled and self-regulated drug delivery. Delivery systems based on these polymers are developed to closely resemble the normal physiological process of the diseased state ensuring optimum drug release according to the physiological need. Also termed 'environmental-sensitive' or 'smart', these polymers experience rapid changes in their microstructure from a hydrophilic to a hydrophobic state triggered by small changes in the environment. The changes are reversible; therefore, the polymer is capable of returning to its initial state as soon as the trigger is removed. Stimuli may occur internally (e.g. a change in pH in certain organs or diseased states, a change in temperature or the presence of specific enzymes or antigens). External stimuli include magnetic or electric fields, light, ultrasound, etc. This review will delve into the various internally and externally stimuli-responsive polymers and the drug delivery systems that exploit them. (topical review)

[en] This study investigated the impact of different photo-activation protocols on selected properties of a model composite formulated using bis-GMA/TEGDMA (1:1 mass ratio), camphorquinone/amine (1:2 mass ratio) and 75% of fillers. The protocols tested were: high-intensity continuous (HIC-500 mW cm^-2 for 20 s), medium-intensity continuous (MIC-250 mW cm^-2 for 40 s), low-intensity continuous (LIC-100 mW cm^-2 for 100 s) and pulse-delay-1 min or 3 min (PD-1 min/3 min-100 mW cm^-2 for 5 s + 1 or 3 min interval + 500 mW cm^-2 for 19 s). Degree of conversion (DC) was evaluated using infrared spectroscopy. Flexural strength (FS) and modulus (FM) were measured in three-point bending mode. Cross-link density was estimated by calculating the swelling coefficient (α) after immersion in chloroform. All methods showed similar values for DC except for PD-1 min, which showed lower DC. HIC and MIC showed similar FS, but were both different than all of the other methods. All curing methods showed similar FM, except for HIC, which presented a different modulus. PD-3 min showed a different swelling than all of the remaining groups, while HIC showed the lowest swelling. A significant relationship was observed between swelling and both FS and FM. In conclusion, the HIC activation protocol generated polymers with properties at least similar, and sometimes improved, in comparison with the alternative protocols.

[en] The attachment, growth behaviour and the genetic effect of human gingival fibroblasts (HGF) cultured on titanium and different zirconia surfaces were investigated. HGF cells were cultured on (1) titanium discs with a machined surface, (2) yttrium-stabilized tetragonal zirconia polycrystals (Y-TZP) with a smooth surface and (3) Y-TZP with 100 μm grooves. The cell proliferation activity was evaluated through a MTT assay at 24 h and 48 h, and the cell morphology was examined by SEM. The mRNA expression of integrin-β1, type I and III collagen, laminin and fibronectin in HGF were evaluated by RT-PCR after 24 h. From the MTT assay, the mean optical density values for the titanium and grooved zirconia surfaces after 48 h of HGF adhesion were greater than the values obtained for the smooth zirconia surfaces. SEM images showed that more cells were attached to the grooves, and the cells appeared to follow the direction of the grooves. The results of RT-PCR suggest that all groups showed comparable fibroblast-specific gene expression. A zirconia ceramic surface with grooves showed biological responses that were comparable to those obtained with HGF on a titanium surface.

[en] Osteogenic maturation of the osteoblast is crucial for bone formation. In this study, multi-walled carbon nanotubes (MWCNTs) and graphite (GP) were pressed as compacts. The greater ability of carbon nanotubes to adsorb proteins, compared with graphite, was shown. Human osteoblast-like SaoS2 cells were cultured and the cell response to the two kinds of compacts was compared in vitro. Meanwhile, we used cell culture on the culture plate as a control. Assays for osteonectin, osteopontin and osteocalcin gene expression, total protein (TP) amount, alkaline phosphatase activity (ALP) and DNA of cells cultured on the samples were done. During the conventional culture, significantly higher osteonectin, osteopontin and osteocalcin gene expression level, ALP/DNA and TP/DNA on carbon nanotubes were found. To confirm the hypothesis that the larger amount of specific proteins adsorbed on the carbon nanotubes was crucial for this, the compacts were pre-soaked in culture medium having additional recombinant human bone morphogenetic protein-2 (rhBMP-2) before cell culture. Compared with GP, osteonectin, osteopontin and osteocalcin gene expression level, ALP/DNA and TP/DNA of the cells tested increased more on the MWCNTs after the compacts were pre-soaked in the culture medium with rhBMP-2. The results indicated that the carbon nanotubes might induce osteogenic maturation of the osteoblast by adsorbing more specific proteins.

[en] The nano-dimensionality of nature has logically given rise to the interest in using nanomaterials in the biomedical field. Currently, a lot of investigations into carbon nanotubes (CNTs), as one of the typical nanomaterials, are being made for biomedical application. In this review, five parts, such as cellular functions induced by CNTs, apatite formation on CNTs, CNT-based tissue engineering scaffold, functionalized CNTs for the delivery of genes and drugs and CNT-based biosensors, are stated, which might indicate that CNTs, with a range of unique properties, appear suited as a biomaterial and may become a useful tool for tissue engineering. However, everything has two parts and CNTs is not an exception. There are still concerns about cytotoxicity and biodegradation of CNTs. Chemical fictionalization may be one of the effective ways to improve the 'disadvantages' and utilize the 'advantages' of CNTs. One of their 'disadvantages', unbiodegradable property, may be utilized by creating monitors in in vivo-engineered tissues or nanosized CNT-based biosensors. Other promising research points, for example proteins adsorbed on CNTs, use of CNTs in combination with other biomaterials to achieve the goals of tissue engineering, mineralization of CNTs and standard toxicological tests for CNTs, are also described in the conclusion and perspectives part. (topical review)

[en] A polyester polycaprolactone-based polyurethane elastomer (PU) and poly-(l-lactide) (PLLA), two common biomaterials, were electrospun to produce membranes with fibres either randomly orientated or aligned. PU was used to produce membranes consisting of smooth fibres. PLLA was used to prepare fibres with a textured surface. Contact angle measurements of the PU and PLLA cast films reveal that they were both below 90 deg. and fully wetted in less than 60 s. These membranes were investigated for the effect of fibre topography and fibre alignment on cell adhesion, using mouse L929 fibroblasts. It was found that the alignment of electrospun fibres controls the directional spreading of fibroblast independent of fibre being smooth or textured.