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.

A novel method to fabricate monetite granules for bone graft applications.

Monetite granules were reported to be able to balance osteoclastic resorption and new bone formation. However, to date, the dehydration of preset brushite has been the well-known method for preparing monetite granules. In the present study, for the first time, monetite granules could be prepared from the phase transformation of calcium sulfate dihydrate (CSD) granules through immersion in NaH2PO4 solution under hydrothermal conditions. CSD granules could be fully transformed into monetite granules at a reaction temperature of 125°C for 24 h. The obtained monetite granules were eight times more soluble in acetate buffer than in Tris-HCl buffer. Furthermore, monetite granules were two times more soluble in acetate buffer but comparable in Tris-HCl buffer compared to xenograft HA. The initial cytotoxicity test indicated that the novel monetite granules were nontoxic. In short, novel monetite granules were successfully prepared, exhibited better solubility in osteoclastic simulation than xenograft HA and were nontoxic.

Compressive Strength of Newly Developed Nonsintered Hydroxyapatite Blocks for Bone Graft Applications.

OBJECTIVE: This study aimed to fabricate and evaluate the phase purity and compressive strength of the nonsintered hydroxyapatite (HA) block obtained via phase transformation of set calcium sulfate dihydrate (CSD) block under hydrothermal conditions at different temperatures. MATERIALS AND METHODS: Nonsintered HA block was prepared by immersion CSD block (4 mm in diameter and 8 mm in height) in a 1 mol/L sodium phosphate (Na3PO4) solution under hydrothermal conditions at 100°C, 140°C, and 180°C for 48 hours. X-ray diffraction was used to determine the crystalline phase of the obtained blocks. The mechanical strength of the blocks was measured using a compressive strength test. RESULTS: The result shows that the CSD block could be fully transformed into a HA block at 180°C for 48 hours without changing its macroscopic shape. The compressive strength of the obtained blocks was lower compared with the CSD block. CONCLUSION: The current method has successfully produced a nonsintered HA block at 180°C for 48 hours. The compressive strength of the HA block decreased compared with the gypsum block used as a precursor. However, the compressive strength of the HA block that was produced still falls within the range of cancellous bone.

Effect of hydrothermal treatment of titanium in high concentration of AgNO 3 solution on surface morphology and roughness.

Development of silver (Ag) modified titanium (Ti) as an antibacterial dental implant has recently been growing. Ag demonstrated an excellent antibacterial property without the risk of bacterial resistance. Hydrothermal treatment using AgNO 3 solution is one of the facile and promising methods to modify Ti surface with Ag. However, the effect of high AgNO 3 concentration and the absent of a toxic reduction agent has not been clearly studied. In this study, Ti surface was hydrothermally treated in 0.01 mol/L and 0.1 mol/L AgNO 3 solutions at 150 oC for 24 hours. Analysis of surface morphology using scanning electron microscopy with energy dispersive X-ray analysis suggested the formation of non-homogenous Ag coating with a tendency to be aggregated and thicken with the increase of AgNO 3 concentration. The Ag coating deposited on Ti surface were composed of mainly metallic and some oxide forms. Surface roughness of all AgNO 3 treated Ti surface was comparable based on the analysis of surface roughness parameter. In conclusion, hydrothermal treatment of Ti surface in solely AgNO 3 solution at high concentration produced non-homogenous Ag coating on its surface without significantly changed surface roughness. Keywords: Silver nitrate, titanium, hydrothermal, surface morphology, roughness.

Improvement of Mechanical Strength of Tissue Engineering Scaffold Due to the Temperature Control of Polymer Blend Solution.

Polymeric scaffolds made of PCL/PLCL (ratio 1:3, respectively) blends have been developed by using the Thermally Induced Phase Separation (TIPS) process. A new additional technique has been introduced in this study by applying pre-heat treatment to the blend solution before the TIPS process. The main objective of this study is to evaluate the influence of the pre-heat treatment on mechanical properties. The mechanical evaluation showed that the mechanical strength of the scaffolds (including tensile strength, elastic modulus, and strain) improved as the temperature of the polymer blend solution increased. The effects on the microstructure features were also observed, such as increasing strut size and differences in phase separation morphology. Those microstructure changes due to temperature control contributed to the increasing of mechanical strength. The in vitro cell study showed that the PCL/PLCL blend scaffold exhibited better cytocompatibility than the neat PCL scaffold, indicated by a higher proliferation at 4 and 7 days in culture. This study highlighted that the improvement of the mechanical strength of polymer blends scaffolds can be achieved using a very versatile way by controlling the temperature of the polymer blend solution before the TIPS process.

Development and characterization of hybrid tubular structure of PLCL porous scaffold with hMSCs/ECs cell sheet.

Tissue engineering offers an alternate approach to providing vascular graft with potential to grow similar with native tissue by seeding autologous cells into biodegradable scaffold. In this study, we developed a combining technique by layering a sheet of cells onto a porous tubular scaffold. The cell sheet prepared from co-culturing human mesenchymal stem cells (hMSCs) and endothelial cells (ECs) were able to infiltrate through porous structure of the tubular poly (lactide-co-caprolactone) (PLCL) scaffold and further proliferated on luminal wall within a week of culture. Moreover, the co-culture cell sheet within the tubular scaffold has demonstrated a faster proliferation rate than the monoculture cell sheet composed of MSCs only. We also found that the co-culture cell sheet expressed a strong angiogenic marker, including vascular endothelial growth factor (VEGF) and its receptor (VEGFR), as compared with the monoculture cell sheet within 2 weeks of culture, indicating that the co-culture system could induce differentiation into endothelial cell lineage. This combined technique would provide cellularization and maturation of vascular construct in relatively short period with a strong expression of angiogenic properties.

Characterization of Tensile Mechanical Behavior of MSCs/PLCL Hybrid Layered Sheet.

A layered construct was developed by combining a porous polymer sheet and a cell sheet as a tissue engineered vascular patch. The primary objective of this study is to investigate the influence of mesenchymal stem cells (MSCs) sheet on the tensile mechanical properties of porous poly-(l-lactide-co-ε-caprolactone) (PLCL) sheet. The porous PLCL sheet was fabricated by the solid-liquid phase separation method and the following freeze-drying method. The MSCs sheet, prepared by the temperature-responsive dish, was then layered on the top of the PLCL sheet and cultured for 2 weeks. During the in vitro study, cellular properties such as cell infiltration, spreading and proliferation were evaluated. Tensile test of the layered construct was performed periodically to characterize the tensile mechanical behavior. The tensile properties were then correlated with the cellular properties to understand the effect of MSCs sheet on the variation of the mechanical behavior during the in vitro study. It was found that MSCs from the cell sheet were able to migrate into the PLCL sheet and actively proliferated into the porous structure then formed a new layer of MSCs on the opposite surface of the PLCL sheet. Mechanical evaluation revealed that the PLCL sheet with MSCs showed enhancement of tensile strength and strain energy density at the first week of culture which is characterized as the effect of MSCs proliferation and its infiltration into the porous structure of the PLCL sheet. New technique was presented to develop tissue engineered patch by combining MSCs sheet and porous PLCL sheet, and it is expected that the layered patch may prolong biomechanical stability when implanted in vivo.