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Metal nanoparticles have always attracted attention for applied catalysis in technical fields including sensor applications. Biogenically synthesized nanoparticles are uniquely non-toxic and possess enhanced antimicrobial activity. Eco-friendly palladium nanoparticles (PdNPs) synthesized from plant extracts and/or biopolymers have wide biomedical, environmental, and biosensor applications. The size, shape, stability, and catalytic behavior of PdNPs are influenced by factors such as pH, temperature, concentration of metallic salt, and concentration of plant extract/biopolymer solutions. This review article focuses on the comprehensive synthesis of biogenic PdNPs from phytochemicals/biopolymers and concisely reports their heterogeneous organic catalytic applications. Furthermore, improved catalytic efficiencies, selectivities, and reaction yields of organic coupling reactions catalyzed by biogenic PdNPs are discussed in detail. This review highlights the safety, sustainability, and effective catalytic activity of biogenic PdNPs for organic coupling reactions, which ensures lesser toxic waste generation and reduces hazardous effects on the environment.

The exploration of biocompatible materials has received greater significance in the research area of energy storage tools. In the present work, a composite material consisting of carboxymethyl cellulose (CMC) with CuO@MnO2 is synthesized via thermal reduction protocol. The resulting composite material exhibited unique morphology and excellent electrochemical properties. The electrochemical properties were premeditated by CV, GCD, and spectral impedance analysis. Electrochemical analyses of the composite materials indicated the extraordinary specific capacitance in a three-electrode configuration. The composite displayed the value of ~414 F/g at a current density of 0.5 A g−1 and the electrodes retaining 96.2% capacitance after 5000 cycles. Therefore, our study demonstrated the synergistic effect of CuO@MnO2 nanoparticles with porous CMC network structures show enhanced electrochemical properties in the presence of 3 M KOH as an electrolyte.

Extracellular matrix (ECM) remodeling is necessary for the development and self-healing of tissue, and the process is tissue specific. Matrix metalloproteinases (MMPs) play a role in ECM remodeling by unwinding and cleaving ECM. We hypothesized that ECM remodeling by MMPs is involved in the differentiation of stem cells into specific lineages during self-healing. To prove the hypothesis, we investigated which MMPs are involved in the osteogenic differentiation of human mesenchymal stem cells (hMSCs) grown on a type I collagen (Col I) matrix, and we found that specifically high expression of MMP13 in hMSCs grown on a Col I matirx during osteogenic differentiation. Moreover, knocking down of MMP13 decreased the osteogenic differentiation of hMSCs grown on a Col I matrix. In addition, pre-treatment of recombinant human MMP13 lead to remodeling of Col I matrix and increased the osteogenic differentiation of hMSCs and in vivo bone formation following the upregulation of the expression of runt-related transcription factor 2 (RUNX2), integrin α3 (ITGA3), and focal adhesion kinase. Furthermore, the transcription factor RUNX2 bound to the MMP13 promoter. These results suggest that growth on a remodeled Col I matrix by MMP13 stimulates osteogenic differentiation of hMSCs and self-healing of bone tissue via an MMP13/ITGA3/RUNX2 positive feedback loop. STATEMENT OF SIGNIFICANCE: Self-healing of tissue could be the key to treating diseases that cannot be overcome by present technology. We investigated the mechanism underlying the self-healing of tissue and we found that the osteogenic differentiation was increased in hMSCs grown on a remodeled Col I matrix by the optimized concentration of MMP13 not in hMSCs grown on a Col I fragments cleaved by a high concentration of MMP13. In addition, we found the remodeled Col I matrix by MMP13 increased the osteogenic capacity through a MMP13/integrin α3/RUNX2 positive feedback loop. This result would be able to not only provide a strategy for bone tissue-specific functional materials following strong evidence about the self-healing mechanism of bone through the interaction between stem cells and the ECM matrix. As such, we strongly believe our finding will be of interest to researchers studying biomaterials, stem cell biology and matrix interaction for regenerative medicine and therapy.

A high level of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) upregulates pro-inflammatory cytokines and inhibits the osteogenic differentiation of mesenchymal stem cells (MSCs), which are key factors in bone regeneration. Ursodeoxycholic acid (UDCA), a hydrophilic bile acid, has antioxidant and anti-inflammatory activities and also plays beneficial roles in bone regeneration by stimulating the osteogenic differentiation of MSCs while suppressing their adipogenic differentiation. Despite its remarkable capacity for bone regeneration, multiple injections of UDCA induce adverse side effects such as mechanical stress and contamination in bone defects. To fully exploit the beneficial roles of UDCA, a concept polymeric prodrug was developed based on the hypothesis that removal of overproduced H2O2 will potentiate the osteogenic functions of UDCA. In this work, we report bone regenerative nanoparticles (NPs) formulated from a polymeric prodrug of UDCA (PUDCA) with UDCA incorporated in its backbone through H2O2-responsive peroxalate linkages. The PUDCA NPs displayed potent antioxidant and anti-inflammatory activities in MSCs and induced osteogenic rather than adipogenic differentiation of the MSCs. In rat models of bone defect, the PUDCA NPs exhibited significantly better bone regeneration capacity and anti-inflammatory effects than equivalent amounts of UDCA. We anticipate that PUDCA NPs have tremendous translational potential as bone regenerative agents.

Despite the advantages of stem cell injection to the skin wound site, this technique is limited in terms of the delivery of therapeutically functional stem cells to the wound site. Considering the abnormal microenvironment of a wound site, even a small damage or loss of cell function induced by severe trypsin treatment might lead to decrement of the therapeutic efficacy of stem cells. In this study, we have synthesized pH-responsive polymer mixed poly(amino ester) (mPAE), which can provide the appropriate cell culture condition for cell growth without cytotoxicity along with the maintenance of extracellular matrix after detachment using low pH (6.0) PBS. Human adipose derive stem cells (hADSCs) cultured on and detached from mPAE-coated tissue culture plates (TCPs) showed similar cell adhesion and angiogenic paracrine factor secretion, compared to hADSCs cultured on and detached from TCPs with trypsin. As a result, hADSCs detached with pH 6.0 PBS from mPAE-coated TCPs showed similar therapeutic angiogenesis and wound regeneration, compared to the hADSCs detached with trypsin from TCPs. In conclusion, our pH-responsive polymer, mPAE, might be utilized as an enzyme-free cell detachment system for future tissue engineering.

The controlled synthesis of Fe2O3@N-MWCNT and cellulose nanocrystal composites were followed by hydrothermal reduction process. The composite samples were examined by analytical methods. The Fe2O3@N-MWCNT and Fe2O3@N-MWCNT/CNC composite samples were studied by CV, GCD, and EIS. The Fe2O3@N-MWCNT and Fe2O3@N-MWCNT/CNC composite showed a specific capacitance of 162 F g−1 and 562 F g−1 at the current density of 0.5 A g−1 and 5000 cycle's compromises and increases the active sites to facilitate ion transfer for electrochemical capacitor applications.

Statement of problem Patients with partial tooth loss treated with implant-supported fixed partial dentures (FPDs) have difficulty using conventional mandibular advancement devices (MADs) because of the risk of side effects. Also, which design factors affect biomechanical stability when designing MADs with better stability is unclear. Purpose The purpose of this finite element (FE) analysis study was to analyze the effect of the MAD design on biomechanical behavior and to propose a new design process for improving the stability of MADs. Material and methods Each 3D model consisted of the maxillofacial bones, teeth, and implant-supported FPDs located in the left tooth loss area from the first premolar to the second molar and a MAD. Three types of custom-made MADs were considered: a complete-coverage MAD covering natural tooth-like conventional MADs, a shortened MAD excluding the coverage on the implant-supported FPD, and a newly designed MAD without anterior coverage. For the new MAD design, topology optimization was conducted to reduce the stress exerted on the teeth and to improve retention of the MAD. The new MAD design was finished by excluding the coverage of the maxillary and mandibular central incisors based on the results of the topology optimization. A mandibular posterior restorative force for a protrusion amount of 40% was used as the loading condition. The principal stress and pressure of the cancellous bone and periodontal ligaments (PDLs) were identified. Results Considering the load concentration induced by the complete-coverage MAD, bone resorption risk and root resorption risk were observed at both ends of the mandibular teeth. The shortened MAD resulted in the highest stress concentration and pressure with the worst stability. However, in the case of the complete-coverage MAD, the pressure in the PDLs was reduced to the normal range, and the risk of root resorption was reduced. Conclusions For patients with implant-supported FPDs, MAD designs with different extents of coverage had an influence on biomechanical behavior in terms of stress distribution in cancellous bone and PDLs. A MAD design without anterior coverage provided improved stability compared with complete-coverage or shortened designs. The presented method for MAD design, which combined FE analysis and topology optimization, could be effectively applied in the design of such improved MADs.

Summary Objective Osteoarthritis (OA) is characterized by cartilage degeneration resulting from hypertrophic changes in chondrocytes caused by altered gene expression. The involvement of Ras homolog enriched in brain (RHEB) in OA regulation is unclear. Methods Human knee articular cartilage samples - were analyzed for structural and biological changes by histology, immunohistochemistry, real time PCR and western blotting. OA-mouse model developed by surgical destabilization of the medial meniscus (DMM) were treated with adenovirus harboring Rheb gene to analyze onset and progression of OA. Histological scoring, immunohistochemistry, and TUNEL assay was performed to assess cartilage damage across the entire joint. Results Human and mouse OA cartilage is degenerated and has markedly reduced levels of RHEB. Human OA-degenerated chondrocytes (DC) exhibited a fibroblastic phenotype and 80 % of degenerative cartilage were senescent, with higher levels of reactive oxygen species (ROS). Gene expression analysis of DC revealed almost no COL2A1 expression and reduced SOX9 and RHEB expression. Transient transfection of RHEB rescued the DC phenotype and reduced senescence and ROS levels markedly. RHEB overexpression also increased COL2A1 and SOX9 expression. In an OA-mouse model, the Rheb protein level decreased as the severity of OA increased. Ectopic expression of Rheb using adenovirus in mouse-OA cartilage suppressed surgically-induced OA pathogenesis accompanied by modulation of Adamts5, Mmp 13, Col 10, and Col2a1 expression. Rheb induction significantly reduced apoptosis in OA-cartilage. Conclusion RHEB plays an important role in maintaining the chondrogenic characteristics of chondrocytes, and has potential in preventing progression of OA in the destabilize the medial meniscus (DMM) mouse model of OA.

In this work we studied front electrodes of nickel/silver (Ni/Ag) deposited on Gr/Si solar cell structure using field induced plating. These electrodes also be used as a front electrode on 2D graphene-based devices at very low cost and temperature (

In graphene/silicon (Gr/Si) solar cell antireflection (ARCs) coatings remarkably enhance the power conversion efficiency. Traditionally titanium dioxide and polymethyl methacrylate used an ARC in Gr/Si solar cells. In such cases controlling film thicknesses and smoothness required a lot of efforts. Here we introduced Vanadium Pentoxide (V2O5) as an ARC in Gr/Si solar cells deposited using thermal evaporator. A well smooth controlled thin-film of V2O5 was achieved. It can easily be thermal evaporated because of its low melting temperature. It was observed after V2O5 coating current density of Gr/Si solar cell remarkably increased from 14 mA/cm2 to 28 mA/cm2 without losing the fill factor. It also helps to improve the Voc from 0.41 to 0.44 V. Different layer thickness shows different colors, results show that a 70 nm layer thickness of V2O5 shows the best ARC for single layer Gr/Si solar cell.

For the reduction of optical loss and contact material cost in silicon heterojunction (SHJ) solar cells, copper plating has been considered as a suitable metallization technique. Usually, a metal seed layer is deposited on an indium tin oxide (ITO) prior to copper plating for adhesive contact between copper and ITO. As a requirement of suitable seed layer material, contact resistivity (ρc) between the seed and the ITO is also important, as well as the adhesion, because high series resistance results in fill factor loss. In this study, we applied alloy seed layers which were deposited by co-evaporating copper with other metals (Cu-X). Contact resistivity values of the samples were extracted by using transfer length method (TLM). Also, tape tests were carried out to simply confirm the adhesion of contacts with different seed layers. Among the Cu-X alloy seed materials, the Cu-Ni alloy film resulted in good adhesion to the ITO as well as low average contact resistivity under 1 mΩ cm2.

Artificial scaffolds made up of various synthetic biodegradable polymers have been reported to have many advantages including cheap manufacturing, easy scale up, high mechanical strength, convenient manipulation, and molding into an unlimited variety of shapes. However, the synthetic biodegradable polymers still have the insufficiency for cartilage regeneration owing to their acidic degradation products. To reduce acidification by degradation of synthetic polymers, we incorporated magnesium hydroxide (MH) nanoparticles into porous polymer scaffold not only to effectively neutralize the acidic hydrolysate but also to minimize the structural disturbance of scaffolds. The neutralization effect of poly(D,L-lactic-co-glycolic acid; PLGA)/MH scaffold was confirmed with the maintenance of neutral pH, contrary to a PLGA scaffold with low pH. Further, the scaffolds were applied to evaluate the chondrogenic differentiation of the human bone marrow mesenchymal stem cells. In in vitro study, the PLGA/MH scaffold enhanced the chondrogenesis markers and reduced the calcification, compared to the PLGA scaffold. Additionally, the PLGA/MH scaffold reduced the release of inflammatory cytokines, compared to the PLGA scaffold, as the cell death decreased. Moreover, the addition of MH reduced necrotic cell death at the early stage of chondrogenic differentiation. Further, the necrotic cell death by the PLGA scaffold was mediated by cleavage of caspase-1, the so-called interleukin 1-converting enzyme, and MH alleviated it as well as nuclear factor kappa B expression. Furthermore, the PLGA/MH scaffold highly supported chondrogenic healing of rat osteochondral defect sites in in vivo study. Therefore, it was suggested that a synthetic polymer scaffold containing MH could be a novel healing tool to support cartilage regeneration and further treatment of orthopedic patients. Statement of Significance Synthetic polymer scaffolds have been widely utilized for tissue regeneration. However, they have a disadvantage of releasing acidic products through degradation. This paper demonstrated a novel type of synthetic polymer scaffold with pH-neutralizing ceramic nanoparticles composed of magnesium hydroxide for cartilage regeneration. This polymer showed pH-neutralization property during polymer degradation and significant enhancement of chondrogenic differentiation of mesenchymal stem cells. It reduced not only chondrogenic calcification but also release of proinflammatory cytokines. Moreover, it has an inhibitory effect on necrotic cell death, particularly caspase-1-mediated necrotic cell death (pyroptosis). In in vivo study, it showed higher healing rate of the damaged cartilage in a rat osteochondral defect model. We expected that this novel type of scaffold can be effectively applied to support cartilage regeneration and further treatment of orthopedic patients.

Hydrogen passivation, such as forming gas annealing and alneal (aluminum anneal) process, has been investigated for high efficient crystalline silicon solar cell structures, because the hydrogen atoms can reduce the surface recombination velocity. However, hydrogen could not diffuse deeply to passivate various defects within the silicon bulk. Further investigations into the properties of hydrogen in the silicon lead to the control of hydrogen atoms’ charge states for their high diffusivity and reactivity. Also, research of the hydrogenated amorphous silicon nitride (a-SiNx:H) as a hydrogen source induced an ‘advanced hydrogen passivation’. This paper provides a review of advanced hydrogen passivation applied on p-type, n-type and upgraded metallurgical grade crystalline silicon solar cells, respectively. Especially, the regeneration of boron-oxygen related defects, which cause carrier induced degradation, will be closely discussed since most of industrial solar cells are fabricated by boron-doped p-type silicon wafer. Moreover, laser-induced hydrogen passivation, which can locally recover defective area on the solar cells, will be addressed. In the conclusion, proper conditions of advanced hydrogen passivation for the successful improvement of minority carrier lifetime will be summarized.

Photovoltaic (PV) electric power generation has the potential to account for a major portion of power generation in the global power market. Currently, the PV market is dominated by crystalline silicon (c-Si) solar cells which accounts for more than 80% of the share. Lower cost, optimized process parameters and improved PV cell efficiencies are required to reduce the overall cost per watt peak (W). In this regard, PV cell manufacturers are currently adopting thinner wafers, which tends to increase the surface recombination velocity (SRV). Excellent surface passivation at the front and rear of the PV cell becomes imperative for realizing superior efficienciy on c-Si substrates. In this article, our focus is to discuss the role of the surface passivation process for improving the PV cell efficiency. The fundamentals and strategies to improve the surface passivation for c-Si solar cells are discussed. Surface passivation schemes and materials with the ability to offer field effect passivation with dielectric charges (positive/negative) present in the passivation films were reviewed. Moreover, we discuss the use of a thin-dielectric passivation layer with a properly selected work function and band offsets for tunneling contacts, facilitating a higher efficiency potential. Finaly, the front/rear surface passivation schemes required for thinner wafers to maintain higher bulk lifetime and higher efficiencies for c-Si solar cells are presented.

Tauroursodeoxycholic acid (TUDCA) has a role in the regulation of the differentiation of mesenchymal stem cells. In this study, TUDCA was demonstrated to increase osteogenic differentiation at a low concentration (25 μM) and chondrogenic differentiation at a high concentration (2500 μM). We investigated the regeneration of osteochondral defects in a rat model using a bilayer plug loaded with two different concentration of TUDCA-PLGA microspheres (TUDCA-MS bilayer plug). The TUDCA-MS bilayer plug successfully regenerated cartilage and subchondral bone layer. Therefore, we suggest that the TUDCA-MS bilayer plug as a new treatment method for simultaneous regeneration of cartilage and subchondral bone layer.

We used porous membranes for co-culturing adipose-derived stem cells (ASCs) with nucleus pulposus cells (NPCs) to investigate whether repeated co-cultures restored the chondrogenic properties of degenerative NPCs (dNPCs). Human dNPCs were co-cultured with ASCs for 1 week and co-cultured again with new ASCs for 1 week. The expression levels of chondrogenic genes and GAGs were significantly higher in second co-cultured dNPCs than those in the first co-cultured dNPCs and in dNPCs cultured alone, respectively. After six weeks of in vivo transplantation, compared to first co-cultured dNPCs, second co-cultured dNPCs showed a significantly higher cartilage tissue formation.

Cancer is a leading cause of death worldwide. The use of nanocarriers (NCs) has generated significant interest to improve cancer therapy by targeted delivery. However, conventional NCs in general lack specificity and have poor biodistribution, resulting in low efficacy in cancer therapy. To circumvent this problem, there has been an increasing focus on cancer cell membrane-coated NCs (CCMCNCs), which can deliver therapeutics directly to tumor cells. CCMCNCs comprise active cancer cell surface adhesive molecules combined with other functional proteins, and offer extended blood circulation with robust cell-specific targeting, ensuring enhanced intratumoral penetration and higher tumor-specific accumulation of NCs. In this review, we discuss the preparation, homologous targeting mechanisms, and application of CCMCNCs in targeted cancer therapy.

Human skin is made up of multiple layers and is designed to protect the human body. The stratum corneum (SC), specifically, is a keratinized layer of skin through which molecules heavier than 500 Da cannot penetrate. Traditional methods of transdermal drug delivery through the SC, such as hypodermic needles, are less than ideal because their size and appearance can cause fear and pain, creating hesitation, limiting self-administration, and preventing their use in some patients altogether. A new technology has been developed to address these limitations, in which an array of needles, each microns in diameter and length, called microneedles, are able to pierce the skin’s SC to deliver therapeutic agents without stimulating the proprioceptive pain nerves. These needles provide a strong advantage because they are capable of being incorporated into patches that can be conveniently self-administered by patients, while also offering the same bioabsorption and bioavailability currently provided by hypodermic needles. There have been many advancements in microneedle fabrication, and there are currently many variations of microneedle technology. Therefore, the purpose of this review is to provide a broad, introductory summary of current microneedle technology.

In recent years, graphene (Gr) based solar cells have attracted extensive interest because of their ability to produce low cost and highly efficient solar cells. Conventional Gr/Si Schottky junction based solar cells are mostly fabricated by transfer of graphene on silicon substrate. In current work the direct growth of graphene by using the Plasma Enhanced Chemical Vapor Deposition (PECVD) technique was demonstrated to make fabrication more practical on a large scale. Firstly Gr/Si Schottky junction based solar cells were fabricated, and by optimizing the growth process, power conversion efficiency (PCE) of about 3.5% was achieved. Additionally, we demonstrated a metal insulator semiconductor (MIS) structure by introducing hafnium oxide (HfO2), and an enriched efficiency of 6.68% was reached. Furthermore, the chemical doping of Gr grown on top of HfO2 passivated Si was done and the efficiency was further enhanced by 8.5%. This study also suggests that the Voc of the Gr/HfO2/Si solar cells strongly depends on the thickness of the HfO2 interfacial layer. These solar cells proved reliable as their efficiency was still consistent even after four months. The current study envisions the use of graphene based solar cells for commercial application.

Biological barriers, such as phagocytosis and nonspecific distribution, are major factors limiting the clinical translation of nanomedicine. Biomimetic and bioengineering strategies have been used to overcome these challenges. In particular, natural cell membrane-based biofunctionalized nanoparticles (CMFNPs) have gained widespread attention owing to their cell surface mimetic characteristics and tailored nanomaterial features. These hybrid nanocarriers show strong potential for the delivery of myriad therapeutic agents. Herein, we highlight the most recent advances in CMFNP-based drug delivery systems and address the challenges and opportunities in the field.

Aluminum-induced crystallization (AIC) is usually used for making silicon seed layer. In this paper, we investigated the AIC process varied with different diffusion barrier materials. The barrier materials were native Al oxide, directly deposited Al 2 O 3 , and SiO 2 in AIC process. The effects of these diffusion barrier materials were analyzed by using electron backscatter diffraction (EBSD), Raman spectroscopy, field emission scanning electron microscope (FE-SEM). The results showed that the case of native Al oxide showed diffusion-limited aggregation which usually resulted in polycrystalline structure. On the other hand, the case of SiO 2 layer showed kinetic-limited aggregation, which generally resulted in the mono-crystalline structure. Therefore, we introduced the novel AIC process with SiO 2 layers.

Hollow porous poly( d , l -lactide-co-glycolide) microspheres (HP-PLGA-MS) were manufactured using the water-in-oil-in-water double emulsion solvent evaporation method with sucrose as a novel porogen. Dexamethasone (DEX) was dissolved in the oil phase and loaded during the preparation of the HP-PLGA-MS. Bone morphogenetic protein-2 (BMP2) with type I collagen (Col1) was incorporated into HP-PLGA-MS using a simple immersion method. The release rate of BMP2 could be controlled by the amount of Col1. DEX and BMP2 showed a sustained release profile. These results showed that the HP-PLGA-MS could be fabricated successfully using sucrose and showed great potential as a controlled dual drug delivery system.

Antiproliferative drug (sirolimus or propolis) loaded lipid polymer hybrid nanospheres (LPHNSs) were prepared by single step method. The effects of different lipids on properties of nanocarrier were investigated. Furthermore, anti proliferative efficiency and cytotoxicity of LPHHNSs-propolis or sirolimus were investigated on human aortic smooth muscle cells (HASMCs), and human aortic endothelial primary cells (HAECs) respectively. The characterization of LPHNSs revealed that the lipids used in the formulation influence physiochemical parameters. In vitro studies showed that the encapsulated sirolimus and propolis significantly reduced the proliferation of HASMCs, while maintaining high HAECs viability.

It is known that osteogenic differentiation of mesenchymal stem cells (MSCs) can be promoted by suppression of adipogenesis of MSCs. We have recently found that the chemical chaperone tauroursodeoxycholic acid (TUDCA) significantly reduces adipogenesis of MSCs. In the present study, we examined whether TUDCA can promote osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMMSCs) by regulating Integrin 5 (ITGA5) associated with activation of ERK1/2 signal pathway and thereby enhance bone tissue regeneration by reducing apoptosis and the inflammatory response. TUDCA treatment promoted in vitro osteogenic differentiation of BMMSCs and in vivo bone tissue regeneration in a calvarial defect model, as confirmed by micro-computed tomography, histological staining, and immunohistochemistry for osteocalcin. In addition, TUDCA treatment significantly decreased apoptosis and the inflammatory response in vivo and in vitro, which is important to enhance bone tissue regeneration. These results indicate that TUDCA plays a critical role in enhancing osteogenesis of BMMSCs, and is therefore a potential alternative drug for bone tissue regeneration.

Summary Adult articular chondrocytes undergo slow senescence and dedifferentiation during in vitro expansion, restricting successful cartilage regeneration. A complete understanding of the molecular signaling pathways involved in the senescence and dedifferentiation of chondrocytes is essential in order to better characterize chondrocytes for cartilage tissue engineering applications. During expansion, cell fate is determined by the change in expression of various genes in response to aspects of the microenvironment, including oxidative stress, mechanical stress, and unsuitable culture conditions. Rapid senescence or dedifferentiation not only results in the loss of the chondrocytic phenotype but also enhances production of inflammatory mediators and matrix-degrading enzymes. This review focuses on the two groups of genes that play direct and indirect roles in the induction of senescence and dedifferentiation. Numerous degenerative signaling pathways associated with these genes have been reported. Upregulation of the genes interleukin 1 beta ( IL-1β ), p53 , p16 , p21 , and p38 mitogen-activated protein kinase ( MAPK ) is responsible for the direct induction of senescence, whereas downregulation of the genes transforming growth factor-beta ( TGF-β ), bone morphogenetic protein-2 ( BMP-2 ), SRY (sex determining region Y)-box 9 ( SOX9 ), and insulin-like growth factor-1 ( IGF-1 ), indirectly induces senescence. In senescent and dedifferentiated chondrocytes, it was found that TGF - β , BMP - 2 , SOX9 , and IGF-1 are downregulated, while the levels of IL - 1β , p53 , p16 , p21 , and p38 MAPK are upregulated followed by inhibition of the normal molecular functioning of the chondrocytes. This review helps to elucidate the underlying mechanism in degenerative cartilage disease, which may help to improve cartilage tissue regeneration techniques.

In this work the copper (Cu) conducting electrode was appraised as an alternative to standard screen printed silver (Ag) front contacts. Laser ablation and photolithography based wet chemical etching were adapted to pattern and analyze adhesion for reliable crystalline silicon (C-Si) solar cell technology. Nickel (Ni) surface treatment after the sintering process contributed to an improved Cu plating with an adhesive Ni–Cu interface. The soldering process for the pull tab adhesion test has an impact on adhesion strength and could reduce the overall value. Smoother surfaces resulted in lower adhesion values in comparison to rough surfaces. Excellent adhesion greater than wafer breakage force with an average value of 1.72 N/mm and maximum adhesion strength of 4.6 N/mm on laser-ablated surfaces were achieved.

To improve bone growth and to imitate the function of natural extracellular matrix for sustained release of multiple growth factors, a scaffold of porous gelatin nanofibers were electrospun, coated with hydroxyapatite using a simulated body fluid solution, and surface-functionalized with avidin to facilitate binding with biotinylated growth factors, namely bone morphogenetic protein-2 (BMP-2) and fibroblast growth factor-2 (FGF-2) at different ratios. Scanning electron microscopy was used for structure characterization and Fourier-transform infrared spectroscopy and calcium assay were performed to evaluate the calcium composition. Immunostaining techniques confirmed the conjugation of multiple growth factors. The effects of the two growth factors and hydroxyapatite on osteogenic cell differentiation were studied using quantitative polymerase chain reaction analysis. Multiple growth factors were successfully conjugated onto the functionalized surface by controlling the FGF-2/BMP-2 ratio. Comparisons of the factor release profiles with those of the physical adsorption showed that avidin-biotin conjugation was more effective for sustained release. Bone regeneration was enhanced via synergism between multiple growth factor delivery and the hydroxyapatite nanofiber coating, as confirmed by the increased expression of osteogenic gene markers. The nanofibers thus provide a promising osteoconductive scaffold with controlled multiple growth factor delivery for bone tissue engineering.

The epithelium-specific ETS transcription factor-1 (ESE-1) is physiologically important in the pathogenesis of various diseases. Recently, OCT4, a transcription factor involved in stem cell pluripotency, has been implicated in tumorigenesis. In this study, we invested the molecular mechanism by which ESE-1 regulates transcription of OCT4 in NCCIT human embryonic carcinoma cells. Real-time PCR analysis revealed that OCT4 levels were high in undifferentiated NCCIT cells but significantly decreased upon retinoic acid-mediated differentiation, concomitant with up-regulation of ESE-1 expression. OCT4 mRNA level rose following shRNA-mediated knockdown of ESE-1, but declined when ESE-1 was overexpressed, suggesting that the expression levels of OCT4 and ESE-1 may be coordinated in an opposite manner. Promoter-reporter assays revealed that induced OCT4 promoter activity in NCCIT cells was significantly down-regulated by ESE-1 overexpression in a dose-dependent manner. The inhibitory effect of ESE-1 on OCT4 promoter activity was relieved by co-expression of an ESE-1 mutant lacking the transactivation domain, but not by mutants lacking other domains. Serial deletion and site-directed mutagenesis of the OCT4 promoter revealed that a potential ETS binding site (EBS) is present in the conserved region 2 (CR2). ESE-1 interacted with the EBS element in CR2 and enrichment of CR2 significantly increased upon RA-mediated differentiation of NCCIT cells, suggesting that this binding is likely to be involved in ESE-1-mediated repression of OCT4 promoter activity upon differentiation. Taken together, the results of this study reveal the molecular details of the mechanism by which the oncogenic factor ESE-1 regulates expression of the stem cell transcription factor OCT4 in pluripotent NCCIT cells.

In this study, our focus is prior to the single step selective emitter for the plated Ni/Cu solar cell. Here, the light induced plating (LIP) technology is used to fabricate the Cu plated solar cell. The purpose of using electroless Ni plating is to prevent the diffusion of Cu into Si and to improve adhesion on the Si substrate as a seed layer for better electrical quality of the solar cell. The characteristics of solar cells such as short-circuit current density have also been analyzed. Throughout the experiment, we have obtained a selective emitter cell of its conversion efficiency of 17.90%, fill factor of 75.14%, V OC of 614 mV and J SC of 38.8 mA/cm 2 , while the conversion efficiency of 17.13%, fill factor of 73.21%, V OC of 614 mV, J SC of 38.1 mA/cm 2 are obtained for a non-selective emitter Ni/Cu solar cell. The efficiency of the selective emitter cell improves about 0.77% compared to that of the reference cell.

Obtaining a sufficient number of cells ex vivo for tissue regeneration, which are appropriate for cartilage repair, requires improved techniques for the continuous expansion of chondrocytes in a manner that does not change their innate characteristics. Rapid senescence or dedifferentiation during in vitro expansion results in loss of chondrocyte phenotype and the formation of fibrous cartilage replacement tissue, rather than hyaluronic cartilage, after transplantation. As demonstrated in the current study, wild-type p53-inducible phosphatase (Wip1), a well-established stress modulator, was highly expressed in early-passage chondrocytes, but declined rapidly during in vitro expansion. Stable Wip1-expressing chondrocytes generated by microporation were less susceptible to the onset of senescence and dedifferentiation, and were more resistant to oxidative stress. The increased resistance of Wip1 chondrocytes to oxidative stress was due to modulation of p38 mitogen-activated protein kinase (MAPK) activity. Importantly, chondrocytes expressing Wip1 maintained their innate chondrogenic properties for a longer period of time, resulting in improvements in cartilage regeneration after transplantation. Chondrocytes from Wip1 knockout (Wip1(-/-)) mice were defective in cartilage regeneration compared with those from wild-type mice. Thus, Wip1 expression represents a potentially useful mechanism by which a chondrocyte phenotype can be retained during in vitro expansion through modulation of cellular stress responses.

The process conditions for high efficiency industrial crystalline Si solar cells with selective emitter were optimized. In the screen printed solar cells, the sheet resistance must be 50–60 Ω/sq. because of metal contact resistance. But the low sheet resistance causes the increase of the recombination and blue response at the short wavelength. Therefore, the screen printed solar cells with homogeneous emitter have limitations of efficiency, and this means that the selective emitter must be used to improve cell efficiency. This work demonstrates the feasibility of a commercially available selective emitter process, based on screen printing and conventional diffusion process. Previous work, we announced about 18.5% efficient selective emitter solar cell by variation of heavy emitter pattern width. Now, we improved cell efficiency from 18.5% to 19% by transition of heavy emitter pattern and shallow emitter doping condition. A maximum cell efficiency of 19.05% is obtained on a 156 mm × 156 mm crystalline silicon solar cell.

A record in laser doped selective emitter (LDSE) solar cells with an efficiency η=19.2% is reported. In this study, we investigate the effect of SiNx films for laser doped selective emitter solar cells with plated front contacts. It is observed that the condition of processes such as silicon nitride and laser doping (LD) is of critical importance prior to light induced plating. If these processes are not performed optimally, localized shunts may form during the light induced plating (LIP) process that then inhibit plating in the surrounding areas. In the previous work an efficiency of 18.3% has been achieved, even though the fill factor was only 74.2% and the cell suffered from additional shunting and shading losses due to overplating. However, in this work, we demonstrate that with the optimization of the PECVD SiNx and metallization processes, cells have reached efficiencies of more than 19% on commercial grade p-type CZ Si substrates.

For clinical application of human embryonic stem cells (hESCs), it is critical to develop hESC culture techniques that completely exclude the use of animal feeder cells, mitotic inhibition, and enzyme treatments used in conventional hESC culture systems. Toward this goal, we attempted to maintain hESCs and induced pluripotent stem (iPS) cells on porous membranes (PMs) with proliferative human adipose-derived stromal cells (ASCs) seeded on the bottom surface of inverted PMs. This culture condition will ensure that the two cell types are separate from each other, yet retain the ability to interact through the pores of the membrane. We found that hESCs and iPS cells can be maintained stably and mechanically transferred without the need for enzyme treatment. In addition, the pluripotency of hESCs and iPS cells was stably maintained, as evidenced by immunostaining of Oct4, SSEA3/4 and TRA-1-60 as well as RT-PCR analyses of Nanog, Oct4 and Sox2 expression. Furthermore, hESCs cultured on PMs showed a normal karyotype and in vivo teratoma formation containing all three germ layers.

Adipose tissue contains multipotent mesenchymal stem cells (MSCs) that are able to differentiate into various tissues. Bone morphogenetic protein 2 (BMP2) is known as one of the key osteogenesis induction factors in MSCs. Recently, several new transcription factors that contribute to osteogenic differentiation have been reported, among them Runx2, Osterix, and Dlx5. We hypothesized that adipose-derived stromal cells (ASCs) could be induced to efficiently differentiate into osteocytes by the co-expression of the BMP2 and Runx2 genes. To prove this hypothesis, we constructed a bicistronic vector encoding the BMP2 and Runx2 genes linked to the 'self-cleaving' 2A peptide sequence. BMP2/Runx2-ASCs showed a gradual increase in alkaline phosphatase activity for two weeks. RT-PCR analysis and alizarin red staining revealed a high expression of osteogenesis-related markers (osteopontin, osteocalcin and collagen type I) and increased mineralization in BMP2/Runx2-ASCs compared to BMP2-ASCs. Six weeks after in vivo transplantation, BMP2/Runx2-ASCs also showed a significant increase in bone formation compared to ASCs and BMP2-ASCs. These findings demonstrate that the co-transfection of two osteogenic lineage-determining genes can enhance osteogenic differentiation of ASCs.

Micropatterning techniques that control three-dimensional (3D) arrangement of biomolecules and cells at the microscale will allow development of clinically relevant tissues composed of multiple cell types in complex architecture. Although there have been significant developments to regulate spatial and temporal distribution of biomolecules in various materials, most micropatterning techniques are applicable only to two-dimensional patterning. We report here the use of two-photon laser scanning (TPLS) photolithographic technique to micropattern cell adhesive ligand (RGDS) in hydrogels to guide cell migration along pre-defined 3D pathways. The TPLS photolithographic technique regulates photo-reactive processes in microscale focal volumes to generate complex, free form microscale patterns with control over spatial presentation and concentration of biomolecules within hydrogel scaffolds. The TPLS photolithographic technique was used to dictate the precise location of RGDS in collagenase-sensitive poly(ethylene glycol-co-peptide) diacrylate hydrogels, and the amount of immobilized RGDS was evaluated using fluorescein-tagged RGDS. When human dermal fibroblasts cultured in fibrin clusters were encapsulated within the micropatterned collagenase-sensitive hydrogels, the cells underwent guided 3D migration only into the RGDS-patterned regions of the hydrogels. These results demonstrate the prospect of guiding tissue regeneration at the microscale in 3D scaffolds by providing appropriate bioactive cues in highly defined geometries.

We have previously reported the efficient osteogenic differentiation of human embryonic stem cells (hESCs) by co-culture with primary human bone-derived cells (hPBDs) without the use of exogenous factors. In the present study, we explored whether osteogenic cells derived from hESCs (OC-hESCs) using the previously reported method would be capable of regenerating bone tissue in vivo. A three-dimensional porous poly(d,l-lactic-co-glycolic acid)/hydroxyapatite composite scaffold was used as a cell delivery vehicle. In vivo implantation of OC-hESC-seeded scaffolds showed significant bone formation in the subcutaneous sites of immunodeficient mice at 4 and 8 weeks after implantation (n=5 for each time point). Meanwhile, implantation of the control no cell-seeded scaffolds or human dermal fibroblast-seeded scaffolds did not show any new bone formation. In addition, the presence of BMP-2 (1 microg/scaffold) enhanced new bone tissue formation in terms of mineralization and the expression of bone-specific genetic markers. According to FISH analysis, implanted OC-hESCs remained in the regeneration sites, which suggested that the implanted cells participated in the formation of new bone. In conclusion, OC-hESCs successfully regenerated bone tissue upon in vivo implantation, and this regeneration can be further enhanced by the administration of BMP-2. These results suggest the clinical feasibility of OC-hESCs as a good alternative source of cells for bone regeneration.

The effect of cross-linking density of hyaluronic acid (HA) hydrogels on mechanical properties and degradation behaviors has been investigated. HA hydrogels were prepared by the covalent cross-linking of HA with poly(ethylene glycol)-diamine with two different molecular weights at various cross-linking densities. The elastic modulus increased gradually as the theoretical cross-linking density of HA hydrogels increased from 0% to 20%. However, as the theoretical cross-linking density increased above 20%, the elastic modulus decreased. At a theoretical cross-linking density of 20%, the elastic modulus increased as the molecular weight of the cross-linking molecule decreased. In vitro degradation rates of HA hydrogels decreased as the molecular weight of the cross-linking molecule decreased at a theoretical cross-linking density of 20%. The degradation rate of the cross-linked HA hydrogels decreased with increases in the theoretical cross-linking density from 0% to 20%. However, there was no significant difference in the degradation rate as the theoretical cross-linking density increased above 30%. With controllable mechanical properties and degradation rates, the developed HA hydrogels would be further investigated for various medical applications.

In this paper, the making of polycrystalline silicon thin films as a seed layer for thicker polycrystalline thin film Si solar cells was investigated. The seed layer was crystallized using Aluminum-induced crystallization (AIC) in various process conditions in order to determine the optimized process parameters of AIC. The layer exchange process and the a-Si crystallization during AIC (annealing at 500 °C, 1 h) were observed. The crystallized and continuous poly-Si thin films were formed with the same thickness as Al layers. However, as the thickness of Al decreased, a continuous film became thinner and more protrusions were observed at film surface. The grain size of crystallized Si thin films ranged from 2000 A to more than 1 μm. The hole concentration, Hall mobility, and resistivity were 3.79–7.00×1018 cm−3, 19.9–36.5 cm2/Vs, and 0.037–0.045 Ω cm , respectively. These results indicate that the fabrication of poly-Si thin films using AIC is an industrially relevant techniques because of low-temperature process and short processing time. The crystallized film with grains more than 2000 A will be a good candidate of seed layers for liquid phase epitaxy.

Since the first introduction of rapid prototyping in 1986, several techniques have been developed and successfully commercialized in the market. However, most commercial systems currently use resins or waxes as the raw materials. Thus, the limited mechanical strength for functional testing is regarded as an obstacle towards broader application of rapid prototyping techniques. To overcome this problem, direct metal deposition methods are being investigated worldwide for rapid prototyping and even for rapid tooling applications. As a contribution to this development, a fundamental study on a process combination of wire welding technology using CO2 laser radiation with milling was carried out and is reported in this paper. Laser welding enables accurate deposition of metals and the subsequent milling increases the surface quality and accuracy to machining standard. Compared to powder, the use of wire is of advantage in terms of a simple feeding mechanism as well as a higher deposition rate. The main focus of the experimental investigation is to find the basic process characteristics. For this purpose, basic parts were fabricated as a function of process parameters such as laser power, welding speed and bead distance. The microstructure, hardness and tensile strength are then examined as a function of these process parameters. In conclusion, the advantages and disadvantages of this process are discussed in comparison with other direct metal fabrication techniques.

As printing machines attain higher operating speeds, paper feeding mechanisms are more prone to problems such as vibration, noise, and paper jams. To design reliable paper feeding mechanisms, designers first use heuristic knowledge to decide the basic specifications of the printer according to the user's requirements. In the preliminary design stage, the design process is represented hierarchically and the characteristics of each part are determined. Conceptually, the process is analogous to the methodology used in configuration design. In this research, the design process has been analyzed systematically by the OMT (object modeling technique) method, which integrates the object, functional, and dynamic models. The physical parts of the paper feeding mechanism are represented as objects, and the design knowledge and design constraints are represented by rules and methods. A commercial expert system shell, Nexpert Object, is adapted for the implementation. The inferred results are converted to create the BOM (bill of materials) data and are saved in a database for the detailed design and production stage.

Block assembly in shipbuilding is mainly concerned with cutting and welding operations to construct a block. A block is composed of several steel plates and sections with various sizes and shapes. Process planning for block assembly is to generate cutting and bending operation plans, assembly processes and sequences, and welding operation plans to construct a block. This paper deals with the development of an automatic process planning system for block assembly in shipbuilding. Part assembly graph that is a semantic network type of representation scheme for block structure is proposed and used to represent block information. The approaches adopted are case-based reasoning for block assembly process planning and rule-based reasoning for process planning of cutting and welding operations. The prototype system has been implemented and verified using real blocks in the block assembly shop.

Summary A fixture planning module is being developed as part of a computational system for concurrent product and process design. In general, three kinds of constraints such as geometric, kinematic, force constraints are considered to provide an appropriate fixturing for a given machining process. Since many fixture arrangements rely on friction to hold a part, the ability to reason about friction is an important component of fixture planning. Limit surface in force/moment space are introduced as a convenient formalism to check whether parts will slip and to help in specifying clamping forces. In this paper, the use of limit surfaces obtained either by scanning over the space of possible motions or by Minkowski sums is compared with other four approaches to establishing the relationships among applied forces and moments and the corresponding direction of sliding motion. Since the other approaches in the literature have only been applied to planar examples, the discussion in this paper will be confined to the case of a planar pressure distribution.

Uniform silicon epitaxial layers have been grown reproducibly over large areas on polished (111) silicon substrates at temperatures as low as 380–450°C. The layers were grown using a novel gold-bismuth alloy as solvent which was shown to have a higher silicon solubility than previous low-temperature solvents. This allowed significantly lower doping in the grown layer to be achieved.