High-Performance, Easy-to-Fabricate, Nanocomposite Heater for Life Sciences and Biomedical Applications.

Microheaters are used in several applications, including medical diagnostics, synthesis, environmental monitoring, and actuation. Conventional microheaters rely on thin-film electrodes microfabricated in a clean-room environment. However, low-cost alternatives based on conductive paste electrodes fabricated using printing techniques have started to emerge over the years. Here, we report a surprising effect that leads to significant electrode performance improvement as confirmed by the thorough characterization of bulk, processed, and conditioned samples. Mixing silver ink and PVA results in the solubilization of performance-hindering organic compounds. These compounds evaporate during heating cycles. The new electrodes, which reach a temperature of 80 °C within 5 min using a current of 7.0 A, display an overall 42% and 35% improvement in the mechanical (hardness) and electrical (resistivity) properties compared to pristine silver ink electrodes. To validate our results, we use the composite heater to amplify and detect parasite DNA from Trypanosoma brucei, associated with African sleeping sickness. Our LAMP test compares well with commercially available systems, confirming the excellent performance of our nanocomposite heaters. Since their fabrication relies on well-established techniques, we anticipate they will find use in a range of applications.

Biomechanical Property and Biocompatibility of a New Silicone Rubber Nasal Retainer (Nostriloo).

Nasal retainers have been utilized to maintain the position of the nose after primary rhinoplasty in cleft lip patients. However, commercial nasal retainers made from silicone are quite expensive. To address this issue, the authors designed an alternative nasal retainer that is affordable, safe, and has similar biomechanical and biocompatibility properties to other commercial nasal retainers. Three types of nasal retainers were tested: our own (Nostriloo), a commercial nasal retainer from Turkey, and another one from Taiwan. There were 3 samples on each group, with a total sample of 9 retainers. Each sample was tested for biomechanical property and biocompatibility. Elasticity modulus, tensile strength, and direct and indirect toxicity were analyzed. Nostriloo had the least durable tensile strength but showed similar elastic modulus (2.76 ± 0.41 MPa) compared with human lower lateral cartilage (2.09 ± 0.81 MPa). On the basis of direct and indirect toxicity tests, Nostriloo is considered nontoxic. Nostriloo can be utilized for small-scale production and use. Further experiment is needed to produce higher-quality nasal retainers.

Effect of Flow Rate Modulation on Alginate Emulsification in Multistage Microfluidics.

The encapsulation of stem cells into alginate microspheres is an important aspect of tissue engineering or bioprinting which ensures cell growth and development. We previously demonstrated the encapsulation of stem cells using the hanging drop method. However, this conventional process takes a relatively long time and only produces a small-volume droplet. Here, an experimental approach for alginate emulsification in multistage microfluidics is reported. By using the microfluidic method, the emulsification of alginate in oil can be manipulated by tuning the flow rate for both phases. Two-step droplet emulsification is conducted in a series of polycarbonate and polydimethylsiloxane microfluidic chips. Multistage emulsification of alginate for stem cell encapsulation has been successfully reported in this study under certain flow rates. Fundamental non-dimensional numbers such as Reynolds and capillary are used to evaluate the effect of flow rate on the emulsification process. Reynolds numbers of around 0.5-2.5 for alginate/water and 0.05-0.2 for oil phases were generated in the current study. The capillary number had a maximum value of 0.018 to ensure the formation of plug flow. By using the multistage emulsification system, the flow rates of each process can be tuned independently, offering a wider range of droplet sizes that can be produced. A final droplet size of 500-1000 µm can be produced using flow rates of 0.1-0.5 mL/h and 0.7-2.4 mL/h for the first stage and second stage, respectively.

Molecularly Imprinted Polymer-Based Sensor for Electrochemical Detection of Cortisol.

As a steroid hormone, cortisol has a close relationship with the stress response, and therefore, can be used as a biomarker for early detection of stress. An electrochemical immunosensor is one of the most widely used methods to detect cortisol, with antibodies as its bioreceptor. Apart from conventional laboratory-based methods, the trend for cortisol detection has seemed to be exploiting antibodies and aptamers. Both can provide satisfactory performance with high selectivity and sensitivity, but they still face issues with their short shelf life. Molecularly imprinted polymers (MIPs) have been widely used to detect macro- and micro-molecules by forming artificial antibodies as bioreceptors. MIPs are an alternative to natural antibodies, which despite demonstrating high selectivity and a low degree of cross-reactivity, often also show a high sensitivity to the environment, leading to their denaturation. MIPs can be prepared with convenient and relatively affordable fabrication processes. They also have high durability in ambient conditions, a long shelf life, and the ability to detect cortisol molecules at a concentration as low as 2 ag/mL. By collecting data from the past five years, this review summarizes the antibody and aptamer-based amperometric sensors as well as the latest developments exploiting MIPs rather than antibodies. Lastly, factors that can improve MIPs performance and are expected to be developed in the future are also explained.

The Use of 3D Polylactic Acid Scaffolds with Hydroxyapatite/Alginate Composite Injection and Mesenchymal Stem Cells as Laminoplasty Spacers in Rabbits.

Several types of laminoplasty spacer have been used to fill bone gaps and maintain a widened canal. A 3D scaffold can be used as an alternative spacer to minimize the risk observed in allografts or autografts. This study aims to evaluate the in vivo biocompatibility and tissue−scaffold integration of a polylactic acid (PLA) scaffold with the addition of alginate/hydroxyapatite (HA) and mesenchymal stem cell (MSc) injections. This is an experimental study with a pretest and post-test control group design. A total of 15 laminoplasty rabbit models were divided into five groups with variations in the autograft, PLA, HA/alginate, and MSc scaffold. In general, there were no signs of inflammation in most samples (47%), and there were no samples with areas of necrosis. There were no significant differences in the histopathological results and microstructural assessment between the five groups. This demonstrates that the synthetic scaffolds that we used had a similar tissue reaction and tissue integration profile as the autograft (p > 0.05). We recommend further translational studies in humans so that this biocompatible fabricated scaffold can be used to fill bone defects.

The Effect of Mesenchymal Stem Cell-Enriched Scaffolds on MMP-8 and TGF-ß Levels of Vertebrae Postlaminoplasty in Rabbit Model.

INTRODUCTION: Some laminoplasty procedures still have restenosis because of bony-bridging failure of the laminar hinge. The present study aimed to determine the effect of mesenchymal stem cell (MSC)-enriched scaffolds on vertebral regeneration after laminoplasty on the basis of the number of osteoblasts, matrix metalloproteinase-8 (MMP-8), and transforming growth factor-beta (TGF-ß) levels. METHODS: Laminoplasty procedure using the Hirabayashi technique was conducted at the lumbar level in 32 rabbits that were divided into four and three groups of the control (C) and treatment groups, respectively, with different types of laminoplasty spacer (T1, autograft; T2, scaffold; and T3, scaffold with MSCs). Histopathological studies were conducted to calculate the number of osteoblasts and enzyme-linked immunosorbent assay tests to detect MMP-8 and TGF-ß 4 weeks after the surgery. RESULTS: The results showed a significant decrease in MMP-8 level in the T3 group compared with that in the control group (p < 0.05). A significant difference exists between the average number of newly formed osteoblasts in the control group compared with that in the T3 group (p < 0.05) with a higher mean blood TGF-ß level of all experimental groups compared with that of the control group (p = 0.58). CONCLUSION: The significant decrease in MMP-8 levels, increase in TGF-ß levels, and increased number of osteoblasts on MSC-seeded polylactic acid scaffolds could be useful to support the laminoplasty procedure to prevent restenosis because it was biocompatible and promoted the bone healing process.

Low-Cost Microfabrication Tool Box.

Microsystems are key enabling technologies, with applications found in almost every industrial field, including in vitro diagnostic, energy harvesting, automotive, telecommunication, drug screening, etc. Microsystems, such as microsensors and actuators, are typically made up of components below 1000 microns in size that can be manufactured at low unit cost through mass-production. Yet, their development for commercial or educational purposes has typically been limited to specialized laboratories in upper-income countries due to the initial investment costs associated with the microfabrication equipment and processes. However, recent technological advances have enabled the development of low-cost microfabrication tools. In this paper, we describe a range of low-cost approaches and equipment (below £1000), developed or adapted and implemented in our laboratories. We describe processes including photolithography, micromilling, 3D printing, xurography and screen-printing used for the microfabrication of structural and functional materials. The processes that can be used to shape a range of materials with sub-millimetre feature sizes are demonstrated here in the context of lab-on-chips, but they can be adapted for other applications. We anticipate that this paper, which will enable researchers to build a low-cost microfabrication toolbox in a wide range of settings, will spark a new interest in microsystems.

Realisation and characterization of conductive hollow fibers for neuronal tissue engineering.

In this article, conductive hollow fibers have been fabricated using melt spinning technique. Multiwalled carbon nanotubes (MWNTs) and poly(3-hexylthiophene-2,5-diyl) (P3HT) have been used to fabricate conductive poly-caprolactone (PCL) composites. The hollow fibers have inner and outer diameter in the range of 300 µm and 500 µm, respectively. Critical parameters to tune the dimension of hollow fibers have been defined following two-dimensions mathematical model. Evaluation of the mechanical properties showed that the incorporation of 1-3 wt % MWNTs and 5-8 wt % P3HT increased Young Modulus of 10% and 20% respectively, compared with pure PCL. The electrical property assessment demonstrated that a minimum incorporation of 3 wt % MWNT and 8 wt % P3HT in PCL matrix transformed composite materials into conductive materials. In addition, SH-SY5Y human neuroblastoma cells were seeded on the fabricated samples an their adhesion, proliferation and neurite length growth were analysed. In particular we observed that these materials promoted cell activities and in particular on MWNT/PCL composites there was a significant increase of neurite growth.

Electrical and mechanical characterisation of single wall carbon nanotubes based composites for tissue engineering applications.

This paper presents the realisation of conductive matrices for application to tissue engineering research. We used poly(L-lactide (PLLA)), poly(epsilon-caprolactone) (PCL), and poly(lactide-co-glycolide) (PLGA) as polymer matrix, because they are biocompatible and biodegradable. The conductive property was integrated to them by adding single wall carbon nanotubes (SWNTs) into the polymer matrix. Several SWNTs concentrations were introduced aiming to understand how they influence and modulate mechanical properties, impedance features and electric percolation threshold of polymer matrix. It was observed that a concentration of 0.3% was able to transform insulating matrix into conductive one. Furthermore, a conductive model of the SWNT/polymer was developed by applying power law of percolation threshold.

Sensing scaffolds to monitor cellular activity using impedance measurements.

Scaffolds are cell adhesive matrices for the realisation of tissue constructs. Here we describe how scaffolds for tissue engineering can also be used as sensors for monitoring cellular activity such as adhesion and spreading. Carbon nanotube polymer composites were fabricated into membranes and scaffolds with electro-conductive properties. Impedance techniques were used to measure the effects of media and cell cultures on composite membranes and the results were analysed using lumped parameter models. We show that protein adhesion can be distinguished from cell adhesion as the impedance changes are much smaller for the latter (5%). In the presence of cells, impedance changes are of the order of 40% and can be correlated with adhesion, spreading and changes in cell density.