Efficient Cross-Layer Optimization Algorithm for Data Transmission in Wireless Sensor Networks

In this paper, we address the problems of joint design for channel selection, medium access control (MAC), signal input control, and power control with cooperative communication, which can achieve tradeoff between optimal signal control and power control in wireless sensor networks (WSNs). The problems are solved in two steps. Firstly, congestion control and link allocation are separately provided at transport layer and network layer, by supply and demand based on compressed sensing (CS). Secondly, we propose the cross-layer scheme to minimize the power cost of the whole network by a linear optimization problem. Channel selection and power control scheme, using the minimum power cost, are presented at MAC layer and physical layer, respectively. These functions interact through and are regulated by congestion rate so as to achieve a global optimality. Simulation results demonstrate the validity and high performance of the proposed algorithm

Preparation, characterization and in vitro angiogenic capacity of cobalt substituted Beta-tricalcium phosphate ceramics

Divalent cobalt ions (Co2+) have been shown to possess the capacity to induce angiogenesis by activating hypoxia inducible factor-1α (HIF-1α) and subsequently inducing the production of vascular endothelial growth factor (VEGF). However, there are few reports about Co-containing biomaterials for inducing in vitro angiogenesis. The aim of the present work was to prepare Co-containing β-tricalcium phosphate (Co-TCP) ceramics with different contents of calcium substituted by cobalt (0, 2, 5 mol%) and to investigate the effect of Co substitution on their physicochemical and biological properties. Co-TCP powders were synthesized by a chemistry precipitation method and Co-TCP ceramics were prepared by sintering the powder compacts. The effect of Co substitution on phase transition and the sintering property of the β-TCP ceramics was investigated. The proliferation and VEGF expression of human bone marrow mesenchymal stem cells (HBMSCs) cultured with both powder extracts and ceramic discs of Co-TCP was further evaluated. The in vitro angiogenesis was evaluated by the tube-like structure formation of human umbilical vein endothelial cells (HUVECs) cultured on ECMatrix™ in the presence of powder extracts. The results showed that Co substitution suppressed the phase transition from β- to α-TCP. Both the powder extracts and ceramic discs of Co-TCP had generally good cytocompatibility to support HBMSC growth. Importantly, the incorporation of Co into β-TCP greatly stimulated VEGF expression of HBMSCs and Co-TCP showed a significant enhancement of network structure formation of HUVECs compared with pure TCP. Our results suggested that the incorporation of Co into bioceramics is a potential viable way to enhance angiogenic properties of biomaterials. Co-TCP bioceramics may be used for bone tissue regeneration with improved angiogenic capacity

A bifunctional scaffold with CuFeSe2 nanocrystals for tumor therapy and bone reconstruction

Bone tumor is one of major challenging issues clinically. After surgical intervention, a few bone tumor cells still remain around bone defects and then proliferate over days. Fabrication of specific biomaterials with dual functions of bone tumor therapy and bone defect regeneration is of great significance. In order to achieve this aim, we managed to prepare bioactive glass (BG) scaffolds functionalized by the CuFeSe2 nanocrystals (BG-CFS) by combining 3D printing technique with solvothermal method. During the solvothermal reaction process, CuFeSe2 nanocrystals could in situ grow on the strut surface of BG scaffolds and thus endow BG scaffolds excellent photothermal performance. The photothermal performance of BG-CFS scaffolds could be well regulated through altering the content of CuFeSe2 nanocrystals and laser power density when exposed to the near infrared laser (808 nm). The BG-CFS scaffolds could not only effectively ablate the bone tumor cells (Saos-2 cells) in vitro, but also significantly inhibit bone tumor growth in vivo. Moreover, BG-CFS scaffolds could stimulate osteogenic gene expression of rabbit bone marrow stromal cells (rBMSCs) and finally facilitate the formation of new bone in the bone defects. Our study, for the first time, combined the photothermal performance of semiconductor CuFeSe2 nanocrystals with the bone-forming activity of bioactive glass scaffolds, which can offer a more extensive horizon for developing novel biomaterials with dual functions of bone tumor therapy and bone regeneration

Mn-containing bioceramics inhibit osteoclastogenesis and promote osteoporotic bone regeneration via scavenging ROS

Osteoporosis is caused by an osteoclast activation mechanism. People suffering from osteoporosis are prone to bone defects. Increasing evidence indicates that scavenging reactive oxygen species (ROS) can inhibit receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclastogenesis and suppress ovariectomy-induced osteoporosis. It is critical to develop biomaterials with antioxidant properties to modulate osteoclast activity for treating osteoporotic bone defects. Previous studies have shown that manganese (Mn) can improve bone regeneration, and Mn supplementation may treat osteoporosis. However, the effect of Mn on osteoclasts and the role of Mn in osteoporotic bone defects remain unclear. In present research, a model bioceramic, Mn-contained β-tricalcium phosphate (Mn-TCP) was prepared by introducing Mn into β-TCP. The introduction of Mn into β-TCP significantly improved the scavenging of oxygen radicals and nitrogen radicals, demonstrating that Mn-TCP bioceramics might have antioxidant properties. The in vitro and in vivo findings revealed that Mn2+ ions released from Mn-TCP bioceramics could distinctly inhibit the formation and function of osteoclasts, promote the differentiation of osteoblasts, and accelerate bone regeneration under osteoporotic conditions in vivo. Mechanistically, Mn-TCP bioceramics inhibited osteoclastogenesis and promoted the regeneration of osteoporotic bone defects by scavenging ROS via Nrf2 activation. These results suggest that Mn-containing bioceramics with osteoconductivity, ROS scavenging and bone resorption inhibition abilities may be an ideal biomaterial for the treatment of osteoporotic bone defect

Preparation of CaO-SiO2-CuO bioactive glasses-embedded anodic alumina with improved biological activities

To improve bone cell cytocompatibility properties of porous anodic alumina (PAA) and implement anti-bacterial properties, amorphous CaO-SiO2-CuO materials were loaded into PAA nano-pores (termed CaO-SiO2- CuO/PAA) by a facile ultrasonic-assisted sol-dipping strategy. The surface features and chemistry of the obtained CaO-SiO2-CuO/PAA were investigated by a field emission scanning microscope (FESEM), an energy-dispersive Xray spectrometer (EDS) and an X-ray photoelectron spectroscopy (XPS). The ability of the CaO-SiO2-CuO/PAA specimens to form apatite via a bio-mineralization processwas evaluated by soaking them in simulated body fluid (SBF) in vitro. The surface microstructure and chemical properties after soaking in SBFwere characterized. The release of ions into the SBF was also measured. In addition, rat osteoblasts and two types of bacterial were cultured on the samples to determine their cytocompatibility and antibacterial properties. The results showed that the amorphous CaO-SiO2-CuO materials were successfully decorated into PAA nano-pores and at the same time maintained their nano-featured surfaces. The CaO-SiO2-CuO/PAA samples induced apatite-mineralization in SBF. Meanwhile, the CaO-SiO2-CuO/PAA samples demonstrated great potential for promoting the proliferation of osteoblasts and inhibiting Escherichia coli (E. coli) as well as Staphylococcus. aureus (S. aureus) growth. Specifically, there was an 86.5±4.1% reduction in E. coli, an 88.0 ± 2.2% reduction in S. aureus for the CaO-SiO2-CuO/PAA surfaces compared to PAA controls. The capability to promote osteoblast proliferation and better antibacterial activity of CaO-SiO2- CuO/PAA may be attributed to the fact that Cu ions can be slowly and constantly released from the samples. Importantly, this was achieved without the use of antibiotics or any pharmaceutical agent. Ultimately, these results suggest that the CaO-SiO2-CuO/PAA substrates possessed improved bone cell cytocompatibility and high antibacterial properties leading to a promising bioactive coating candidate for enhanced orthopedic applications

3D printing of metal-organic framework nanosheets-structured scaffolds with tumor therapy and bone construction

After surgical resection for a bone tumor, the uncleared bone tumor cells can multiply and causerecurrence of the bone tumor. It is worthwhile to design a scaffold that kills the remaining bone tumorcells and repairs bone defects that were given rise to by surgical resection. Additionally, it is extremelyimportant to consider the function of angiogenesis in the process of bone regeneration because thenewly formed blood vessels can offer the nutrients for bone regeneration. In this work, a novel metalorganicframework Cu-TCPP nanosheets interface-structured β-tricalcium phosphate (TCP)(Cu-TCPP-TCP) scaffold was successfully prepared through integrating a 3D-printing technique withan in-situ growth method in a solvothermal system. Owing to the excellent photothermal effect ofCu-TCPP nanosheets, Cu-TCPP-TCP scaffolds that were illuminated by near-infrared (NIR) lightdemonstrated photothermal performance, which was well regulated through varying the contents ofCu-TCPP nanosheets, and the ambient humidity and power density of NIR light. When cultured withosteosarcoma cells, Cu-TCPP-TCP scaffolds killed a significant quantity of osteosarcoma cellsthrough released heat energy after exposure to NIR light with power density 1.0Wcm−2 and duration10 min. Similarly, Cu-TCPP-TCP scaffolds ablated subcutaneous bone tumor tissues on the backs ofnaked mice and suppressed their growth because of the heat energy transformed from NIR light. Invitrostudies found that Cu-TCPP-TCP scaffolds ably supported the attachments of both human bonemarrow stromal cells (HBMSCs) and human umbilical vein endothelial cells (HUVECs), andsignificantly stimulated expressions of osteogenesis differentiation-related genes in HBMSCs andangiogenesis differentiation-related genes in HUVECs. After implanting Cu-TCPP-TCP scaffoldsinto the bone defects of rabbits, they effectively promoted bone regeneration. Thus, the integration ofthe bone-forming bioactivity of TCP scaffolds with the photothermal properties of Cu-TCPPnanosheets and angiogenesis activity of Cu ions makes Cu-TCPP-TCP scaffolds multifunctional,representing a new horizon to develop biomaterials for simultaneously curing bone tumors andrepairing bone defects