Search

The pseudocapacitive performance of MnO2 is intrinsically determined by its electronic structure, especially the spin state. However, the correlation between the electrochemical behavior and the spin state of electrode materials remains ill‐defined, and efficient spin regulation strategies for MnO2 are thus lacking. Herein, the study reports laser thermal shock of electrochemically deposited MnO2 for efficient spin regulation. The combined use of theoretical calculation and experimental investigation indicates that the thermal shock induces oxygen vacancy in MnO2 to reduce spin polarization and delocalize electron distribution. As a result, the electrical conductivity largely increases and the Na+ adsorption is reasonably optimized. By lasering an integrated electrode for only 83 s, a 54% increase of the specific capacitance is observed. For the first time, the pseudocapacitive capability of MnO2 is revealed by in situ electron paramagnetic resonance where the enhanced redox pair is correlated with evolution of Mn2+ during charge/discharge. Moreover, the commercial‐level mass‐loaded electrode also offers a decent performance enhancement after laser treatment, indicating the great prospect of this technology for real applications. This work innovatively correlates the pseudocapacitive performance of MnO2 with its spin state and offers a new avenue to optimize the electrochemical capability through spin regulation. [ABSTRACT FROM AUTHOR]

Efficient low‐temperature hydrodeoxygenation (HDO) of lignin derivatives to produce biofuels and high value‐added chemicals is still of challenge. Here, we have constructed a high active and stable 0.2 wt.% Pd/MS‐HZSM‐5(30) catalyst, and 94.7 % yield of 2‐methoxy‐4‐methylphenol (MMP) can be achieved in HDO of vanillin (VAN, a typical platform molecule of lignin derivatives) under milder reaction conditions (60 °C, 5 h, molar ratio of VAN/Pd=1200, water phase), outperforming the most works reported recently. Detailed experimental and mechanistic studies demonstrated that the superior catalytic performance was due to the rapid hydrogenolysis of generated intermediate (vanillyl alcohol, VAL) to MMP proceeded in an interfacial microenvironmental created by Pd NPs and acidic sites in Pd/MS‐HZSM‐5(30). These new insights will provide potential guidance for the efficient low‐temperature production of biofuels and valuable chemicals from lignin derivatives or raw lignin. [ABSTRACT FROM AUTHOR]

Bioprinting three‐dimensional (3D) tissue equivalents have progressed tremendously over the last decade. 3D bioprinting is currently being employed to develop larger and more physiologic tissues, and it is of particular interest to generate vasculature in biofabricated tissues to aid better perfusion and transport of nutrition. Having an advantage over manual culture systems by bringing together biological scaffold materials and cells in precise 3D spatial orientation, bioprinting could assist in placing endothelial cells in specific spatial locations within a 3D matrix to promote vessel formation at these predefined areas. Hence, in the present study, we investigated the use of bioprinting to generate tissue‐level capillary‐like networks in biofabricated tissue constructs. First, we developed a bioink using collagen type‐1 supplemented with xanthan gum (XG) as a thickening agent. Using a commercial extrusion‐based multi‐head bioprinter and collagen‐XG bioink, the component cells were spatially assembled, wherein the endothelial cells were bioprinted in a lattice pattern and sandwiched between bioprinted fibroblasts layers. 3D bioprinted constructs thus generated were stable, and maintained structural shape and form. Post‐print culture of the bioprinted tissues resulted in endothelial sprouting and formation of interconnected capillary‐like networks within the lattice pattern and between the fibroblast layers. Bioprinter‐assisted spatial placement of endothelial cells resulted in fabrication of patterned prevascularized constructs that enable potential regenerative applications in the future. [ABSTRACT FROM AUTHOR]

Lithium‐sulfur batteries (LSB) are one of the potential candidates for the next generation of electrochemical energy storage technology, due to their advantages of high theoretical capacity and high energy density. However, sluggish redox kinetics and the shuttle effect of polysulfides in the cyclic process lead to low sulfur utilization, severe polarization and poor cyclic stability. Herein, an SnS modified porous carbon nanosheet (SnS/PCNS) hybrid material is synthesized by a simple hydrothermal method and used to modify the separator of the LSB for the first time. Specifically, SnS/PCNS can not only adsorb polysulfides, but also enhance the redox reaction of polysulfides. In addition, SnS/PCNS are shown to promote rapid nucleation and uniform deposition of Li2S, and to improve the discharge capacity and heighten cyclic stability. The initial capacity is 1270 mAh g−1 at 0.5 C, the slow decay rate of each cycle is 0.039% at 1 C. When the sulfur loading is improved to 6 mg cm−2, the high reversible capacity is 955.3 mAh g−1 at 0.5 C. As a new polysulfides adsorbent, SnS provides a potential route for the commercialization of LSBs. [ABSTRACT FROM AUTHOR]

The chemistry of transition‐metal complexes with unusually high coordination numbers has been of interest because of their application in catalytic and biological systems. Deprotonation of the ionogenic tetradentate ligand 6,6′‐bis(1H‐tetrazol‐5‐yl)‐2,2′‐bipyridine [H2bipy(ttr)2] in the presence of iron(III) and tetra‐n‐butylammonium bromide, [n‐Bu4N]Br, in solution resulted in the synthesis of a rare octacoordinated anionic mononuclear complex, tetra‐n‐butylammonium bis[6,6′‐bis(tetrazol‐1‐id‐5‐yl)‐2,2′‐bipyridine]iron(III) methanol hemisolvate dihydrate, (C16H36N)[Fe(C12H6N10)2]·0.5CH3OH·2H2O or [n‐Bu4N][Fe{bipy(ttr)2}2]·0.5CH3OH·2H2O (1), which has been structurally characterized by elemental analysis, powder X‐ray diffraction (PXRD) and single‐crystal X‐ray diffraction. In 1, the coordination sphere of the iron(III) ion is a distorted bis‐disphenoid dodecahedron, in which the eight coordination positions are occupied by eight N atoms from two independent tetradentate [bipy(ttr)2]2− anionic ligands, therefore forming the anionic [Fe{bipy(ttr)2}2]− unit, with the negative charge balanced by a free [n‐Bu4N]+ cation. An investigation of the magnetic properties of 1 revealed a gradual incomplete spin‐crossover behaviour below 150 K. [ABSTRACT FROM AUTHOR]

With the new semi‐rigid V‐shaped bidentate pyridyl amide compound 5‐methyl‐N,N′‐bis(pyridin‐4‐yl)benzene‐1,3‐dicarboxamide (L) as an auxiliary ligand and the FeII ion as the metal centre, one mononuclear complex, bis(methanol‐κO)bis[5‐methyl‐N,N′‐bis(pyridin‐4‐yl)benzene‐1,3‐dicarboxamide‐κN]bis(thiocyanato‐κN)iron(II), [Fe(SCN)2(C19H16N4O2)2(CH3OH)2] (1), and one two‐dimensional coordination polymer, catena‐poly[[[bis(thiocyanato‐κN)iron(II)]‐bis[μ‐5‐methyl‐N,N′‐bis(pyridin‐4‐yl)benzene‐1,3‐dicarboxamide‐κ2N:N′]] methanol disolvate dihydrate], {[Fe(SCN)2(C19H16N4O2)2]·2CH3OH·2H2O}n (2), were prepared by slow evaporation and H‐tube diffusion methods, respectively, indicating the effect of the method of crystallization on the structure type of the target product. Both complexes have been structurally characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray crystallography. The single‐crystal X‐ray diffraction analysis shows that L functions as a monodentate ligand in mononuclear 1, while it coordinates in a bidentate manner to two independent Fe(SCN)2 units in complex 2, with a different conformation from that in 1 and the ligands point in two almost orthogonal directions, therefore leading to a two‐dimensional grid‐like network. Investigation of the magnetic properties reveals the always high‐spin state of the FeII centre over the whole temperature range in 1 and a gradual thermally‐induced incomplete spin crossover (SCO) behaviour below 150 K in 2, demonstrating the influence of the different coordination fields on the spin properties of the metal ions. The current results provide useful information for the rational design of functional complexes with different structure dimensionalities by employing different conformations of the ligand and different crystallization methods. [ABSTRACT FROM AUTHOR]

The new species Macromtrium longipapillosum D. D. Li, J. Yu, T. Cao & S. L. Guo from Japan is described and illustrated by line drawings and photographs. The new species can be distinguished from all congeners by the combination of the following features: 1) lanceolate to oblong-lanceolate leaves with obtuse, acute to broadly acuminate apices; 2) upper and median laminal cells with thin and inflated walls, with a single, large, occasionally forked papilla, 7-14 μm, occasionally up to 18 μm, 3) basal cells near costae forming a 'cancellina region', 4) inner perichaetial leaves ovate lanceolate, abruptly narrowed to a long acuminate upper part; 5) short and left-twisted seta; and 6) obloid capsules with well-developed exostome teeth. We also revise the circumscription of Macromitrium comatum Mitt. and discuss the relationships of M. comatum with M. longipapillosum and other relevant species. [ABSTRACT FROM AUTHOR]

The advent of technology has led to an established range of engineered nanoparticles that are used in diverse applications, such as cell-cell interactions, cell-material interactions, medical therapies and the target modulation of cellular processes. The exponential increase in the utilization of nanomaterials and the growing number of associated criticisms has highlighted the potential risks of nanomaterials to human health and the ecosystem. The existing in vivo and in vitro platforms show limitations, with fluctuations being observed in the results of toxicity assessments. Pluripotent stem cells (PSCs) are viable source of cells that are capable of developing into specialized cells of the human body. PSCs can be efficiently used to screen new biomaterials/drugs and are potential candidates for studying impairments of biophysical morphology at both the cellular and tissue levels during interactions with nanomaterials and for diagnosing toxicity. Three-dimensional in vitro models obtained using PSC-derived cells would provide a realistic, patient-specific platform for toxicity assessments and in drug screening applications. The current review focuses on PSCs as an alternative in vitro platform for assessing the hazardous effects of nanomaterials on health systems and highlights the importance of PSC-derived in vitro platforms. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Calcyclin-binding protein or Siah-1-interacting protein (CacyBP/SIP) was previously reported to promote the proliferation of glioma cells. However, the effect of CacyBP/SIP on apoptosis of glioma is poorly understood. Here, our study shows that CacyBP/SIP plays a role in inhibiting doxorubicin (DOX) induced apoptosis of glioma cells U251 and U87. Overexpression of CacyBP/SIP obviously suppressed the DOX-induced cell apoptosis. On the contrary, silencing of CacyBP/SIP significantly promoted it. Further investigation indicated that inhibition of apoptosis by CacyBP/SIP was relevant to its nuclear translocation in response to the DOX treatment. Importantly, we found that the level of p-ERK1/2 in nuclei was related to the nuclear accumulation of CacyBP/SIP. Finally, the role of CacyBP/SIP was confirmed in vivo in a mouse model with the cell line stably silencing CacyBP/SIP. Taken together, our results suggest that CacyBP/SIP plays an important role in inhibiting apoptosis of glioma cells which might be mediated by ERK1/2 signaling pathway, which will provide some guidance for the treatment of glioma. © 2016 IUBMB Life, 68(3):211-219, 2016 [ABSTRACT FROM AUTHOR]

Objective The role of subcutaneous adipose tissue (SAT) in the pathogenesis of type 2 diabetes is still under controversy. In this study, the metabolic effects of inducing adipocyte hyperplasia in SAT depots in obese mice were investigated. Methods High fat diet was used to induce obesity and type 2 diabetes symptoms in C57BL6/J mice. To induce SAT expansion through hyperplasia, acellular adipogenic cocktails were injected around the SAT depots in high fat diet-induced obese mice. Results Ten weeks after injections, significant neoadipogenesis was induced, which not only obviously expanded the volume of SATs but also significantly increased the adipocyte density within the whole SAT depots. Importantly, these mice exhibited improved glucose tolerance and insulin sensitivity (homeostatic model assessment) when compared to control group. Further studies suggested that these beneficial metabolic effects were associated with elevation of serum high-molecular-weight adiponectin level and reduction of ectopic lipid accumulation in liver. Conclusions These findings not only further supported the protective role of SAT in the pathogenesis of type 2 diabetes but also highlighted the importance of adipocyte hyperplasia in this protective effect. [ABSTRACT FROM AUTHOR]

To understand, in greater detail, the molecular mechanisms regulating the complex relationship between mechanical strain and alveolar bone metabolism during orthodontic treatment, passive cross-arch palatal springs were bonded to the maxillary molars of 6-wk-old rats, which were killed after 4 and 8 d. Outcome measures included serum assays for markers of bone formation and resorption and for the multifunctional hormone leptin, and histomorphometry of the inter-radicular bone. The concentration of the bone-formation marker alkaline phosphatase ( ALP) was significantly reduced at both time points in the appliance group, accompanied by a 50% reduction in inter-radicular bone volume; however, osteocalcin (bone Gla protein) levels remained unaffected. Bone collagen deoxypyridinoline ( DPD) crosslinks increased 2.3-fold at 4 d only, indicating a transient increase in bone resorption; in contrast, the level of the osteoclast-specific marker, tartrate-resistant acid phosphatase 5b ( TRACP 5b), was unchanged. Leptin levels closely paralleled ALP reductions at both time points, suggesting an important role in the mechanostat negative-feedback loop required to normalize bone mass. These data suggest that an orthodontic appliance, in addition to remodeling the periodontal ligament ( PDL)-bone interface, may exert unexpected side-effects on the tooth-supporting alveolar bone, and highlights the importance of recognizing that bone strains can have negative, as well as positive, effects on bone mass. [ABSTRACT FROM AUTHOR]

Background The innate immune response ( IMR) is critical for the oral mucosa due to their continuous exposure to various oral pathogens. Keratinocytes play important role in IMR. Therefore, to date, keratinocytes from different sources have been used as in vitro research model for the study of IMR. However, current keratinocyte research models are hampered by the limited supply, patients' dependency and batch to batch variation. Therefore, in this study, we demonstrated the use of human embryonic stem cells (h ESCs) derived keratinocytes ( H9- Kert) as an alternative research model for the study of IMR. Methods The expression kinetics of toll-like receptor ( TLR) 2, TLR 4, interleukin ( IL) -6, IL-8, inducible nitric oxide synthase (i NOS) and tumour necrosis factor-alpha ( TNF-α), in H9- Kert and immortalized human keratinocyte cell line ( Ha Ca T) were analysed at m RNA levels by both reverse transcription polymerase chain reaction ( RT- PCR) and quantitative real-time RT- PCR. The activation of the inflammatory transcription factor nuclear factor kappa-b ( NFĸ B) was assayed in these cells by transiently transfecting the cells with NFĸ B reporter plasmid. Activation of NFĸ B following treatment with heat-killed Porphyromonas gingivalis ( P. gingivalis), an oral pathogen, was determined by assaying for the reporter, secreted alkaline phosphatase activity. Results The expression of TLRs, cytokines and activation of NFĸ B following bacterial stimulation showed in both H9- Kert and the widely used Ha Ca T keratinocyte cell line was similar. Conclusion Overall, our results support the potential application of h ESCs as an alternative limitless cell source for primary keratinocytes which can be used as consistent and dependable research tool with minimum variations and no donor's dependency. [ABSTRACT FROM AUTHOR]

Macromitrium ousiense is a neglected Chinese moss species, differing from other taxa of the genus in its leaves with smooth laminal cells and gymnostomus capsules with hairy calyptrae. We found that M. heterodictyon Dixon is a new synonym of M. ousiense, and Japan is a new distribution record for the species. [ABSTRACT FROM AUTHOR]

Antioxidative enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX)), as well as lipid peroxidation and proline were studied in moss Brachythecium piligerum Card. collected from different sites in Shanghai, China, to validate the physiological parameters as biomarkers of atmospheric heavy metal pollution. Results demonstrated that the responses of POD and CAT activities, as well as MDA and proline contents were in accordance with the heavy metal contents in mosses. That is, POD activity, MDA, and proline content were activated and CAT activity was inhibited in heavier polluted sites, indicating that POD and CAT activities, and MDA and proline contents could be used as biomarkers for biomonitoring atmospheric heavy metal pollution. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2010. [ABSTRACT FROM AUTHOR]

Endothelial progenitors derived from human embryonic stem cells (hESCs) hold much promise in clinical therapy. Conventionally, lineage-specific differentiation of hESCs is achieved through supplementation of various cytokines and chemical factors within the culture milieu. Nevertheless, this is a highly inefficient approach that is often limited by poor replicability. An alternative is through genetic modulation with recombinant DNA. Hence, this study investigated whether transduction of hESCs with an adenoviral vector expressing the human VEGF165 gene (Ad-hVEGF165) can enhance endothelial-lineage differentiation. The hESCs were induced to form embryoid bodies (EBs) by culturing them within low-attachment plates for 7 days, and were subsequently trypsinized into single cells, prior to transduction with Ad-hVEGF165. Optimal transduction efficiency with high cell viability was achieved by 4-h exposure of the differentiating hESCs to viral particles at a ratio of 1 : 500 for three consecutive days. ELISA results showed that Ad-hVEGF165-transduced cells secreted human vascular endothelial growth factor (hVEGF) for more than 30 days post-transduction, peaking on day 8, and the conditioned medium from the transduced cells stimulated extensive proliferation of HUVEC. Real-time PCR analysis showed positive upregulation of VEGF, Ang-1, Flt-1, Tie-2, CD34, CD31, CD133 and Flk-1 gene expression in Ad-hVEGF165-transduced cells. Additionally, flow cytometric analysis of CD133 cell surface marker revealed an approximately 5-fold increase in CD133 marker expression in Ad-hVEGF165-transduced cells compared to the non-transduced control. Hence, this study demonstrated that transduction of differentiating hESCs with Ad-hVEGF165 facilitated expression of the VEGF transgene, which in turn significantly enhanced endothelial differentiation of hESCs. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copyright of Cell Biochemistry & Function is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Presents a letter to the editor regarding co-transplantation of autologous adult stem cells and derivatives of human embryonic stem cells in connection with strategies to enhance the efficacy of autologous cell transplantation therapy.

This study attempted to investigate whether different levels of mitotic activity exist within different physical regions of a human embryonic stem (hES) cell colony. Incorporation of 5-bromo-2-deoxyuridine (BrdU) within newly-synthesized DNA, followed by immunocytochemical staining was used as a means of detecting mitotically-active cells within hES colonies. The results showed rather surprisingly that the highest levels of mitotic activity are primarily concentrated within the central regions of hES colonies, whereas the peripheral regions exhibited reduced levels of cellular proliferation. Two hypothetical mechanisms are therefore proposed for hES colony growth and expansion. Firstly, it is envisaged that the less mitotically-active hES cells at the periphery of the colony are continually migrating outwards, thereby providing space for newly-divided daughter cells within the more mitotically-active central region of the hES colony. Secondly, it is proposed that the newly-divided hES cells within the central region of the colony somehow migrate to the outer periphery. This could possibly explain why the periphery of hES colonies are less mitotically-active, since there would obviously be an extended time-lag before newly-divided daughter cells are ready again for the next cell division. Further investigations need to be carried out to characterize the atypical mechanisms by which hES colonies grow and expand in size. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the association between loss of ovarian function and bone mineral density changes in the mandibles of ovariectomized rabbits using peripheral quantitative computed tomography. Twenty-four adult female Japanese white rabbits were used in this experiment. The mandibular incisors were initially extracted to create implant bone. Twelve animals were bilaterally ovariectomized and the other twelve sham-ovariectomized 12 weeks after tooth extraction. All rabbits were sacrificed at 4 and 12 weeks after ovariectomy and sham-ovariectomy, with 6 rabbits in each of the four resultant groups. The edentulous parts of distal mandibular bodies were measured by peripheral quantitative computed tomography. There were significant decreases in total bone mineral density and trabecular bone mineral density in the mandibles of rabbits at 12 weeks post-ovariectomy. The results demonstrate the mineralized bone loss in the mandibles of ovariectomized rabbits. [ABSTRACT FROM AUTHOR]

Human embryonic stem cells (hESCs) are considered as useful tools for pre-clinical studies in regenerative medicine. Although previous reports have shown direct chondrogenic differentiation of mouse and hESCs, low yield and cellular heterogenicity of the resulting cell population impairs the generation of sufficient numbers of differentiated cells for further testing and applications. Based on our previously established high-density micromass model system to study hESC chondrogenesis, we evaluated the effects of transforming growth factor (TGF)-beta(1) and bone morphogenetic protein-2 on early stages of chondrogenic differentiation and commitment by hESCs. Significant chondrogenic induction of hESCs, as determined by quantitative measurements of cartilage-related gene expression and matrix protein synthesis, was achieved in the presence of TGF-beta(1). By means of selective growth factor combination (TGF-beta(1), FGF-2 and platelet-derived growth factor-bb) and plating on extracellular matrix substratum, we report here the reproducible isolation of a highly expandable, homogenous and unipotent chondrogenic cell population, TC1, from chondrogenically committed hESCs. Like primary chondrocytes, TC1 rapidly dedifferentiates upon isolation and monolayer expansion but retains the chondrogenic differentiation potential and responds to TGF-beta(1) for cartilaginous tissue formation both in vitro and in vivo. In addition, TC1 displays a somatic cell cycle kinetics, a normal karyotype and does not produce teratoma in vivo. Thus, TC1 may provide a potential source of chondrogenic cells for drug testing, gene therapy and cell-based therapy.

Current bone disease therapy with bone marrow-derived mesenchymal stromal cells (MSC) is hampered by low efficiency. Advanced allogeneic studies on well-established mouse genetic and disease models are hindered by difficulties in isolating murine MSC (mMSC). And mMSC prepared from different laboratories exhibit significant heterogeneity. Hence, this study aimed to identify and isolate a sub-population of mMSC at an early passage number with high osteogenic potential. Enrichment of mMSC was achieved by 1-hr silica incubation and negative selection. Approximately 96% of these cells synthesized osteocalcin after 28 days of osteogenic induction in vitro, and displayed a complete dynamic alteration of alkaline phosphatase (ALP) activity with increasing osteogenic maturation and strong mineralization. Moreover, the cells displayed uniform and stable surface molecular profile, long-term survival, fast proliferation in vitro with maintenance of normal karyotype and distinct immunological properties. CD73 was found to be expressed exclusively in osteogenesis but not in adipogenesis. These cells also retained high osteogenic potential upon allogeneic transplantation in an ectopic site by the detection of bone-specific ALP, osteopontin, osteocalcin and local mineralization as early as 12 days after implantation. Hence, these cells may provide a useful source for improving current strategies in bone regenerative therapy, and for characterizing markers defining the putative MSC population.

Because hESC (human embryonic stem cells) are 'social cells' that require co-operative interactions and intimate physical contact with each other, it is absolutely essential to dissociate hESC colonies into cellular clumps rather than into a single-cell suspension during serial passage. The present study compared two commonly used protocols for dissociating hESC colonies. The first protocol involved mild enzymatic treatment with collagenase type IV (1 mg/ml) for approx. 5-10 min, prior to mechanical dissociation into cellular clumps through manual scraping with a plastic pipette tip. The second protocol involved a short duration of exposure (2-3 min) to low concentrations of trypsin (0.05%), followed by gentle pipetting. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay was used to compare the recovery of viable cells after dissociating hESC colonies with these two protocols, before and after conventional freeze-thawing with 10% (v/v) DMSO. Besides undifferentiated hESC, the randomly differentiated fibroblastic progenies of hESC at various passages (P0-P4), together with an immortalized cell line (CRL-1486), were also utilized to compare the two protocols. The results demonstrated that the second protocol (trypsinization with gentle pipetting) is much less detrimental to cellular viability than is the first protocol (collagenase treatment with scratching). This in turn translated to higher freeze-thaw survival rates. It is hypothesized that scratching after collagenase treatment (first protocol) somehow induces physical damage to the cells, thereby leading to a lower recovery of viable cells, both before and after freeze-thawing.

hES (human embryonic stem) cells hold tremendous potential in the newly emerging field of regenerative medicine, in addition to being a useful tool in basic scientific research and for pharmacological and cytotoxicity screening. However, an essential prerequisite for the future widespread application of hES cells are the development of efficient cryopreservation protocols to facilitate their storage and transportation. This review summarizes the current state of progress in the field of hES cell cryopreservation, by critically examining and comparing the various cryopreservation protocols that have been developed. These can be classified into two categories: (1) conventional slow-cooling protocols and (2) vitrification protocols. Previously, the application of slow-cooling cryopreservation protocols to freely-suspended hES cell clumps yielded extremely dismal results. However, a recent study demonstrated that post-thaw survivability was markedly improved when slow-cooling protocols were applied instead to adherent hES colonies. Vitrification protocols have been shown to be much better than the standard slow-cooling protocol for the cryopreservation of freely suspended hES cell clumps. However, no study has yet attempted to apply vitrification protocols to adherent hES colonies. It must be noted that vitrification protocols are extremely labour-intensive and tedious to perform manually. Additionally, the use of cryostraws in vitrification protocols is unsuited for handling bulk quantities of hES cells, in addition to posing serious technical difficulties in developing machine automation for cryopreservation. These are some of the major challenges that have to be overcome if further progress is to be made in this field.