Supplementation of GelMA with Minimally Processed Tissue Promotes the Formation of Densely Packed Skeletal-Muscle-Like Tissues

We present a simple and cost-effective strategy for developing gelatin methacryloyl (GelMA) hydrogels supplemented with minimally processed tissue (MPT) to fabricate densely packed skeletal-muscle-like tissues. MPT powder was prepared from skeletal muscle by freeze-drying, grinding, and sieving. Cell-culture experiments showed that the incorporation of 0.5-2.0% (w/v) MPT into GelMA hydrogels enhances the proliferation of murine myoblasts (C2C12 cells) compared to proliferation in pristine GelMA hydrogels and GelMA supplemented with decellularized skeletal-muscle tissues (DCTs). MPT-supplemented constructs also preserved their three-dimensional (3D) integrity for 28 days. By contrast, analogous pristine GelMA constructs only maintained their structure for 14 days or less. C2C12 cells embedded in MPT-supplemented constructs exhibited a higher degree of cell alignment and reached a significantly higher density than cells loaded in pristine GelMA constructs. Our results suggest that the addition of MPT incorporates a rich source of biochemical and topological cues, such as growth factors, glycosaminoglycans (GAGs), and structurally preserved proteins (e.g., collagen). In addition, GelMA supplemented with MPT showed suitable rheological properties for use as bioinks for extrusion bioprinting. We envision that this simple and cost-effective strategy of hydrogel supplementation will evolve into an exciting spectrum of applications for tissue engineers, primarily in the biofabrication of relevant microtissues for in vitro models and cultured meat and ultimately for the biofabrication of transplant materials using autologous MPT.

Controlling cellular organization in bioprinting through designed 3D microcompartmentalization

Controlling cellular organization is crucial in the biofabrication of tissue-engineered scaffolds, as it affects cell behavior as well as the functionality of mature tissue. Thus far, incorporation of physiochemical cues with cell-size resolution in three-dimensional (3D) scaffolds has proven to be a challenging strategy to direct the desired cellular organization. In this work, a rapid, simple, and cost-effective approach is developed for continuous printing of multicompartmental hydrogel fibers with intrinsic 3D microfilaments to control cellular orientation. A static mixer integrated into a coaxial microfluidic device is utilized to print alginate/gelatin-methacryloyl (GelMA) hydrogel fibers with patterned internal microtopographies. In the engineered microstructure, GelMA compartments provide a cell-favorable environment, while alginate compartments offer morphological and mechanical cues that direct the cellular orientation. It is demonstrated that the organization of the microtopographies, and consequently the cellular alignment, can be tailored by controlling flow parameters in the printing process. Despite the large diameter of the fibers, the precisely tuned internal microtopographies induce excellent cell spreading and alignment, which facilitate rapid cell proliferation and differentiation toward mature biofabricated constructs. This strategy can advance the engineering of functional tissues.

Biofabrication of muscle fibers enhanced with plant viral nanoparticles using surface chaotic flows

Multiple human tissues exhibit fibrous nature. Therefore, the fabrication of hydrogel filaments for tissue engineering is a trending topic. Current tissue models are made of materials that often require further enhancement for appropriate cell attachment, proliferation and differentiation. Here we present a simple strategy, based on the use of surface chaotic flows amenable to mathematical modeling, to fabricate continuous, long and thin filaments of gelatin methacryloyl (GelMA). The fabrication of these filaments is achieved by chaotic advection in a finely controlled and miniaturized version of the journal bearing system. A drop of GelMA pregel is injected on a higher-density viscous fluid (glycerin) and a chaotic flow is applied through an iterative process. The millimeter-scale hydrogel drop is exponentially deformed and elongated to generate a meter-scale fiber, which was then polymerized under UV-light exposure. Computational fluid dynamic (CFD) simulations are conducted to determine the characteristics of the flow and design the experimental conditions for fabrication of the fibers. GelMA fibers were effectively used as scaffolds for C2C12 myoblast cells. Experimental results demonstrate an accurate accordance with CFD simulations for the predicted length of the fibers. Plant-based viral nanoparticles (i.e.Turnip mosaic virus; TuMV) were then integrated to the hydrogel fibers as a secondary nano-scaffold for cells for enhanced muscle tissue engineering. The addition of TuMV significantly increased the metabolic activity of the cell-seeded fibers (p* < 0.05), strengthened cell attachment throughout the first 28 d, improved cell alignment, and promoted the generation of structures that resemble natural mammal muscle tissues. Chaotic two-dimensional-printing is proven to be a viable method for the fabrication of hydrogel fibers. The combined use of thin and long GelMA hydrogel fibers enhanced with flexuous virions offers a promising alternative for scaffolding of muscle cells and show potential to be used as cost-effective models for muscle tissue engineering purposes.

Characterization of a novel automated microfiltration device for the efficient isolation and analysis of circulating tumor cells from clinical blood samples

The detection and analysis of circulating tumor cells (CTCs) may enable a broad range of cancer-related applications, including the identification of acquired drug resistance during treatments. However, the non-scalable fabrication, prolonged sample processing times, and the lack of automation, associated with most of the technologies developed to isolate these rare cells, have impeded their transition into the clinical practice. This work describes a novel membrane-based microfiltration device comprised of a fully automated sample processing unit and a machine-vision-enabled imaging system that allows the efficient isolation and rapid analysis of CTCs from blood. The device performance was characterized using four prostate cancer cell lines, including PC-3, VCaP, DU-145, and LNCaP, obtaining high assay reproducibility and capture efficiencies greater than 93% after processing 7.5 mL blood samples spiked with 100 cancer cells. Cancer cells remained viable after filtration due to the minimal shear stress exerted over cells during the procedure, while the identification of cancer cells by immunostaining was not affected by the number of non-specific events captured on the membrane. We were also able to identify the androgen receptor (AR) point mutation T878A from 7.5 mL blood samples spiked with 50 LNCaP cells using RT-PCR and Sanger sequencing. Finally, CTCs were detected in 8 out of 8 samples from patients diagnosed with metastatic prostate cancer (mean ± SEM = 21 ± 2.957 CTCs/mL, median = 21 CTCs/mL), demonstrating the potential clinical utility of this device.

High-Throughput Automated Microscopy of Circulating Tumor Cells

Circulating tumor cells (CTCs) have the potential of becoming the gold standard marker for cancer diagnosis, prognosis and monitoring. However, current methods for its isolation and characterization suffer from equipment variability and human operator error that hinder its widespread use. Here we report the design and construction of a fully automated high-throughput fluorescence microscope that enables the imaging and classification of cancer cells that were labeled by immunostaining procedures. An excellent agreement between our machine vision-based approach and a state-of-the-art microscopy equipment was achieved. Our integral approach provides a path for operator-free and robust analysis of cancer cells as a standard clinical practice.

Toward Smaller Aqueous-Phase Plasmonic Gold Nanoparticles: High-Stability Thiolate-Protected ∼4.5 nm Cores

Most applications of aqueous plasmonic gold nanoparticles benefit from control of the core size and shape, control of the nature of the ligand shell, and a simple and widely applicable preparation method. Surface functionalization of such nanoparticles is readily achievable but is restricted to water-soluble ligands. Here we have obtained highly monodisperse and stable smaller aqueous gold nanoparticles (core diameter ∼4.5 nm), prepared from citrate-tannate precursors via ligand exchange with each of three distinct thiolates: 11-mercaptoundecanoic acid, α-R-lipoic acid, and para-mercaptobenzoic acid. These are characterized by UV-vis spectroscopy for plasmonic properties; Fourier transform infrared (FTIR) spectroscopy for ligand-exchange confirmation; X-ray diffractometry for structural analysis; and high-resolution transmission electron microscopy for structure and size determination. Chemical reduction induces a blueshift, maximally +0.02 eV, in the localized surface plasmon resonance band; this is interpreted as an electronic (-) charging of the monolayer-protected cluster (MPC) gold core, corresponding to a -0.5 V change in electrochemical potential.

Emerging Trends in Micro- and Nanoscale Technologies in Medicine: From Basic Discoveries to Translation

We discuss the state of the art and innovative micro- and nanoscale technologies that are finding niches and opening up new opportunities in medicine, particularly in diagnostic and therapeutic applications. We take the design of point-of-care applications and the capture of circulating tumor cells as illustrative examples of the integration of micro- and nanotechnologies into solutions of diagnostic challenges. We describe several novel nanotechnologies that enable imaging cellular structures and molecular events. In therapeutics, we describe the utilization of micro- and nanotechnologies in applications including drug delivery, tissue engineering, and pharmaceutical development/testing. In addition, we discuss relevant challenges that micro- and nanotechnologies face in achieving cost-effective and widespread clinical implementation as well as forecasted applications of micro- and nanotechnologies in medicine.

Anti-Ebola therapies based on monoclonal antibodies: current state and challenges ahead

The 2014 Ebola outbreak, the largest recorded, took us largely unprepared, with no available vaccine or specific treatment. In this context, the World Health Organization declared that the humanitarian use of experimental therapies against Ebola Virus (EBOV) is ethical. In particular, an experimental treatment consisting of a cocktail of three monoclonal antibodies (mAbs) produced in tobacco plants and specifically directed to the EBOV glycoprotein (GP) was tested in humans, apparently with good results. Several mAbs with high affinity to the GP have been described. This review discusses our current knowledge on this topic. Particular emphasis is devoted to those mAbs that have been assayed in animal models or humans as possible therapies against Ebola. Engineering aspects and challenges for the production of anti-Ebola mAbs are also briefly discussed; current platforms for the design and production of full-length mAbs are cumbersome and costly.

Abstract P4-09-13: Breast cancer recurrence risk: A role for the progesterone receptor isoforms

Progesterone receptor (PR) is currently used as a surrogate marker for functional estrogen receptor activity in breast cancer. Two PR isoforms have been described, PRB and PRA. PRA (94 kDa) is a truncated protein that lacks the first 164 amino acids of the NH2 terminal of PRB (115 kDa), making difficult the development of antibodies that discriminate PRA from PRB by standard immunohistochemistry (IHC). There are few studies describing the expression of PR isoforms in breast cancers. While there is a general consensus that PRA is the prevailing isoform expressed in breast cancer tissues as compared with normal mammary gland, there is controversial data regarding the association between their deregulated expression and endocrine response or aggressiveness. We are currently studying the expression of the PR isoform ratio in breast cancer samples obtained during surgical resection in order to test their antiprogestin responsiveness in tissue cultures. The study has been approved by the IRB (2012-028). Selected samples were studied by RNAseq and the data was used to analyze the PAM50 genes to predict risk of recurrence, and interestingly, almost all the genes related to proliferation were up-regulated in samples categorized as having higher levels of PRB than PRA, being also these patients those with a high risk of recurrence (May and Rojas et al., ASCO Annual Meeting, poster#11016, 2015). These observations are in agreement with data obtained in hormone resistant breast cancer xenografts with higher levels of PRB than PRA (Wargon and Riggio et al, International Journal of Cancer: 2680, 2015). The aim of this study is to evaluate a possible correlation between the PR isoform ratio, proliferation as evaluated by Ki67 or HER2 expression, and clinical outcome in selected breast cancer samples. Ki67 was evaluated by IHC using standard protocols in 80 PR+ samples. The PRA/PRB ratio was also evaluated in nuclear extracts, performed from frozen tissue, from the same patients, by Western Blot. A negative correlation was observed between the Ki67 score and the log2 value of the PRA/PRB ratio (Spearman R:-0.3418; p&lt; 0.0029). Samples were considered PRA+ if PRA/PRB ≥ 1.2 and PRB+, if PRA/PRB ≤ 0.83. Seven out of 62 PRA+ (11.29%), and 7 out of 35 (20%) of PRB+ samples were HER2+. The differences between both groups, although not significant, correlate directly with the Ki67 evaluation. The results of this ongoing project lend support to the hypothesis that the ratio of PRA/PRB is associated with prognosis and highlight the role of PR as key players regulating breast cancer growth.

Citation Format: Gass HD, May M, Rojas P, Abba M, Sequeira G, Martinez Vazquez P, Gonzalez PL, Elía A, Alvarez MM, Molinolo A, Lanari CL. Breast cancer recurrence risk: A role for the progesterone receptor isoforms. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-09-13.

Induction of apoptosis in colon cancer cells treated with isorhamnetin glycosides from Opuntia ficus-indica pads

(OFI) contains health-promoting compounds like flavonoids, being the isorhamnetin glycosides the most abundant. We evaluated the effect of OFI extracts with different isorhamnetin glycosides against two different human colon cancer cells (HT-29 and Caco2). The extracts were obtained by alkaline hydrolysis with NaOH at 40 °C during 15, 30 or 60 min. Tri and diglycosides were the most abundant isorhamnetin glycosides, therefore these compounds were isolated to compare their cytotoxic effect with the obtained from the extracts. The OFI extracts and purified isorhamnetin glycosides were more cytotoxic against HT-29 cells than Caco2 cells. OFI-30 exhibited the lowest IC50 value against HT-29 (4.9 ± 0.5 μg/mL) and against Caco2 (8.2 ± 0.3 μg/mL). Isorhamnetin diglycosides IG5 and IG6 were more cytotoxic than pure isorhamnetin aglycone or triglycosides when they were tested in HT-29 cells. Bioluminescent analysis revealed increased activity of caspase 3/7 in OFI extracts-treated cells, particularly for the extract with the highest concentration of isorhamnetin triglycosides. Flow cytometry analysis confirmed that OFI extract and isorhamnetin glycosides induced a higher percentage of apoptosis in HT-29 than in Caco2, while isorhamnetin was more apoptotic in Caco2. This research demonstrated that glycosilation affected antiproliferative effect of pure isorhamnetin glycosides or when they are mixed with other phytochemicals in an extract obtained from OFI.

A baseline process for the production, recovery, and purification of bacterial influenza vaccine candidates

The current commercial system for influenza vaccine production depends on the culture of virus in embryonated eggs--a strategy that is both costly and poorly scalable. Consequently, a sudden pandemic event with a demand for millions of vaccine doses in a short time could readily overwhelm the available world production capacity. In this communication, we present a process that uses Escherichia coli for scalable production of recombinant vaccine candidates against influenza. A monomeric and a dimeric fragment of hemagglutinin of the influenza A H1N1/2009 virus were successfully expressed in a BL21 (DE3) pLysS variety of C41 E. coli. We present results from batch processes where induction is made with isopropyl thiogalactoside and from fed-batch experiments where expression is induced using lactose/glucose pulses. Concentrations in the range of 1.188-0.605 g/L of recombinant protein were observed in 2-L stirred tank bioreactors. The genetic construct included an N-terminal histidine tag sequence that facilitated recovery, purification, and proper refolding of the vaccine candidate by affinity chromatography in columns loaded with Ni(+2) . The proteins produced by this strategy selectively and specifically recognizes antibodies from patients diagnosed as positive to influenza A H1N1/2009. Overall protein recovery yields between 30.0 and 34.7% were typically observed. Based on these yields, a production of 4.6 × 10(3) doses L(-3) day(-1) is feasible.

A biopharmaceutical plant on a chip: continuous micro-devices for the production of monoclonal antibodies

We report a proof-of-principle for the use of micro-devices as continuous bioreactors for the production of monoclonal antibodies. We culture CHO cells on the surface of PMMA "zigzag" channels textured with semi-spherical cavities coated with fibronectin, observing steady-state productivities 100 times higher than those observed in full scale systems.

A simple eccentric stirred tank mini-bioreactor: mixing characterization and mammalian cell culture experiments

In industrial practice, stirred tank bioreactors are the most common mammalian cell culture platform. However, research and screening protocols at the laboratory scale (i.e., 5-100 mL) rely primarily on Petri dishes, culture bottles, or Erlenmeyer flasks. There is a clear need for simple-easy to assemble, easy to use, easy to clean-cell culture mini-bioreactors for lab-scale and/or screening applications. Here, we study the mixing performance and culture adequacy of a 30 mL eccentric stirred tank mini-bioreactor. A detailed mixing characterization of the proposed bioreactor is presented. Laser induced fluorescence (LIF) experiments and computational fluid dynamics (CFD) computations are used to identify the operational conditions required for adequate mixing. Mammalian cell culture experiments were conducted with two different cell models. The specific growth rate and the maximum cell density of Chinese hamster ovary (CHO) cell cultures grown in the mini-bioreactor were comparable to those observed for 6-well culture plates, Erlenmeyer flasks, and 1 L fully instrumented bioreactors. Human hematopoietic stem cells were successfully expanded tenfold in suspension conditions using the eccentric mini-bioreactor system. Our results demonstrate good mixing performance and suggest the practicality and adequacy of the proposed mini-bioreactor.

Seroprevalence of antibodies to influenza A/H1N1/2009 among transmission risk groups after the second wave in Mexico, by a virus-free ELISA method

OBJECTIVE

No serological studies have been performed in Mexico to assess the seroprevalence of influenza A/H1N1/2009 in groups of people according to the potential risk of transmission. The aim of this study was to determine the seroprevalence of antibodies against influenza A/H1N1/2009 in subjects in Mexico grouped by risk of transmission.

METHODS

Two thousand two hundred and twenty-two subjects were categorized into one of five occupation groups according to the potential risk of transmission: (1) students, (2) teachers, (3) healthcare workers, (4) institutional home residents aged >60 years, and (5) general population. Seroprevalence by potential transmission group and by age grouped into decades was determined by a virus-free ELISA method based on the recombinant receptor-binding domain of the hemagglutinin of influenza A/H1N1/2009 virus as antigen (85% sensitivity; 95% specificity). The Wilson score, Chi-square test, and logistic regression models were used for the statistical analyses.

RESULTS

Seroprevalence for students was 47.3%, for teachers was 33.9%, for older adults was 36.5%, and for the general population was 33.0%, however it was only 24.6% for healthcare workers (p=0.011). Of the students, 56.6% of those at middle school, 56.4% of those at high school, 52.7% of those at elementary school, and 31.1% of college students showed positive antibodies (p<0.001). Seroprevalence was 44.6% for college teachers, 31.6% for middle school teachers, and 29.8% for elementary school teachers, but was only 20.3% for high school teachers (p=0.002).

CONCLUSIONS

The student group was the group most affected by influenza A/H1N1/2009, while the healthcare worker group showed the lowest prevalence. Students represent a key target for preventive measures.

An influenza A/H1N1/2009 hemagglutinin vaccine produced in Escherichia coli

Background

The A/H1N1/2009 influenza pandemic made evident the need for faster and higher-yield methods for the production of influenza vaccines. Platforms based on virus culture in mammalian or insect cells are currently under investigation. Alternatively, expression of fragments of the hemagglutinin (HA) protein in prokaryotic systems can potentially be the most efficacious strategy for the manufacture of large quantities of influenza vaccine in a short period of time. Despite experimental evidence on the immunogenic potential of HA protein constructs expressed in bacteria, it is still generally accepted that glycosylation should be a requirement for vaccine efficacy.

Methodology/Principal Findings

We expressed the globular HA receptor binding domain, referred to here as HA_63–286-RBD, of the influenza A/H1N1/2009 virus in Escherichia coli using a simple, robust and scalable process. The recombinant protein was refolded and purified from the insoluble fraction of the cellular lysate as a single species. Recombinant HA_63–286-RBD appears to be properly folded, as shown by analytical ultracentrifugation and bio-recognition assays. It binds specifically to serum antibodies from influenza A/H1N1/2009 patients and was found to be immunogenic, to be capable of triggering the production of neutralizing antibodies, and to have protective activity in the ferret model.

Conclusions/Significance

Projections based on our production/purification data indicate that this strategy could yield up to half a billion doses of vaccine per month in a medium-scale pharmaceutical production facility equipped for bacterial culture. Also, our findings demonstrate that glycosylation is not a mandatory requirement for influenza vaccine efficacy.

Specific recognition of influenza A/H1N1/2009 antibodies in human serum: a simple virus-free ELISA method

Background

Although it has been estimated that pandemic Influenza A H1N1/2009 has infected millions of people from April to October 2009, a more precise figure requires a worldwide large-scale diagnosis of the presence of Influenza A/H1N1/2009 antibodies within the population. Assays typically used to estimate antibody titers (hemagglutination inhibition and microneutralization) would require the use of the virus, which would seriously limit broad implementation.

Methodology/Principal Findings

An ELISA method to evaluate the presence and relative concentration of specific Influenza A/H1N1/2009 antibodies in human serum samples is presented. The method is based on the use of a histidine-tagged recombinant fragment of the globular region of the hemagglutinin (HA) of the Influenza A H1N1/2009 virus expressed in E. coli.

Conclusions/Significance

The ELISA method consistently discerns between Inf A H1N1 infected and non-infected subjects, particularly after the third week of infection/exposure. Since it does not require the use of viral particles, it can be easily and quickly implemented in any basic laboratory. In addition, in a scenario of insufficient vaccine availability, the use of this ELISA could be useful to determine if a person has some level of specific antibodies against the virus and presumably at least partial protection.

Production of probiotic biomass (Lactobacillus casei) in goat milk whey: comparison of batch, continuous and fed-batch cultures

This contribution examines the technical feasibility of producing high added value probiotic biomass from deproteinized and non-supplemented milk whey. The kinetics of growth of Lactobacillus casei in deproteinized goat milk whey was analyzed. Experiments in batch, continuous and fed-batch conditions were conducted in a 3 L fully instrumented bioreactor. Final substrate and biomass concentrations, yields and productivities are reported for different culture strategies. A kinetic analysis was conducted to characterize biomass production, product inhibition effects, and substrate consumption rates. Due to the strong product inhibition, fed-batch cultures at high biomass concentration rendered higher productivity (0.45 g L(-1) h(-1)) than batch and continuous cultures (0.11 g L(-1) h(-1)), complete lactose conversions (<1.0 g of lactose/L at the end of each fed-batch cycle), and a product with higher viable cell counts (2 x 10(10) cell/g of freeze-dried product). Based on our result, high-cell density fed-batch strategies are recommended for commercial production of probiotic L. casei biomass.

Effect of mixing during fermentation in yogurt manufacturing

In traditional yogurt manufacturing, the yogurt is not agitated during fermentation. However, stirring could be beneficial, particularly for improving heat and mass transport across the fermentation tank. In this contribution, we studied the effect of low-speed agitation during fermentation on process time, acidity profile, and microbial dynamics during yogurt fermentation in 2 laboratory-scale fermenters (3 and 5 L) with different heat-transfer characteristics. Lactobacillus bulgaricus and Streptococcus thermophilus were used as fermenting bacteria. Curves of pH, lactic acid concentration, lactose concentration, and bacterial population profiles during fermentation are presented for static and low-agitation conditions during fermentation. At low-inoculum conditions, agitation reduced the processing time by shortening the lag phase. However, mixing did not modify the duration or the shape of the pH profiles during the exponential phase. In fermentors with poor heat-transfer characteristics, important differences in microbial dynamics were observed between the agitated and nonagitated fermentation experiments; that is, agitation significantly increased the observable specific growth rate and the final microbial count of L. bulgaricus.

Mixing of non-Newtonian fluids in steadily forced systems

We investigate mixing in a viscoelastic and shear-thinning fluid-a very common combination in polymers and suspensions. We find that competition between elastic and viscous forces generates self-similar mixing, lobe transport, and other characteristics of chaos. The mechanism by which chaos is produced is evaluated both in experiments and in a simple model. We find that chaotic flow is generated by spontaneous oscillations, the magnitude and frequency of which govern the extent of chaos and mixing.

Dry granular flows can generate surface features resembling those seen in Martian gullies

Over the past decade or more, contradictory evidence of Martian climate, indicating that surface temperatures seldom if ever approach the melting point of water at midlatitudes, and geomorphic features, consistent with liquid flows at these same latitudes, have proven difficult to reconcile. In this article, we demonstrate that several features of liquid-erosional flows can be produced by dry granular materials when individual particle settling is slower than characteristic debris flow speeds. Since the gravitational acceleration on Mars is about one-third that on Earth, and since particle settling speeds scale with gravity, we propose that some (although perhaps not all) Martian geomorphological features attributed to liquid flows may in fact be associated with dry granular flows in the presence of reduced gravity.

Attraction of minute particles to invariant regions of volume preserving flows by transients

We find that tracer material can be concentrated into invariant regions of flows due exclusively to transient effects, as are produced when tracers temporarily become more buoyant than the surrounding fluid. This can occur either as a single event, e.g., if the tracer is initially weakly buoyant, or under periodic forcing, e.g., when external effects (such as solar heating) change the tracer density periodically. We study both cases in experiments, in a model, and in direct numerical simulations of laminar flow in a stirred tank. Focusing occurs for very small tracer size and inertia in flows that are instantaneously strictly volume conserving.

Gold nanoelectrodes of varied size: transition to molecule-like charging

A transition from metal-like double-layer capacitive charging to redox-like charging was observed in electrochemical ensemble Coulomb staircase experiments on solutions of gold nanoparticles of varied core size. The monodisperse gold nanoparticles are stabilized by short-chain alkanethiolate monolayers and have 8 to 38 kilodaltons core mass (1.1 to 1.9 nanometers in diameter). Larger cores display Coulomb staircase responses consistent with double-layer charging of metal-electrolyte interfaces, whereas smaller core nanoparticles exhibit redox chemical character, including a large central gap. The change in behavior is consistent with new near-infrared spectroscopic data showing an emerging gap between the highest occupied and lowest unoccupied orbitals of 0.4 to 0.9 electron volt.

Fullerene Isomerism: Isolation of C2v,-C78 and D3-C78

Early reports on the formation of the higher fullerenes C(76), C(78), C(84), C(90), and C(94) by resistive heating of graphite stimulated theoretical calculations of possible cage structures for these all-carbon molecules. Among the five fullerene structures with isolated pentagons found for C(78), a closed-shell D3h-isomer was predicted to form preferentially. Two distinct C(78)-isomers were formed in a ratio of approximately 5:1 and could be separated by high-performance liquid chromatography. The carbon-13 nuclear magnetic resonance (NMR) spectrum of the major isomer is uniquely consistent with a C2v-structure. The NMR data also support a chiral D(3)-structure for the minor isomer. The isolation of specifically these two isomers of C(78) provides insight into the stability of higher fullerene structures and into the mechanism for fullerene formation in general.

Atomic Force Microscope Studies of Fullerene Films: Highly Stable C 60 fcc (311) Free Surfaces

Atomic force microscopy and x-ray diffractometry were used to study 1500 A-thick films of pure C(60) grown by sublimation in ultrahigh vacuum onto a CaF(2) (111) substrate. Topographs of the films did not reveal the expected close-packed structures, but they showed instead large regions that correspond to a face-centered cubic (311) surface and distortions of this surface. The open (311) structure may have a relatively low free energy because the low packing density contributes to a high entropy of the exposed surface.

Play and play areas for hospitalized children

Play is critical to children's development in social, cognitive, and affective domains. Children actively construct meaning through playful interaction with people and objects. Play materials and environments in turn, affect the level, structure and content of children's play. The following article discusses these issues and the application of contemporary architectural design and current research findings on play environments to the special problems of hospitalized children. Concerns related to separation from family and routine, unfamiliar hospital personnel and procedure, institutionalization, and temporary immobility can be constructively dealt with by thoughtful planning for children's play. Specific suggestions with respect to designing play spaces in hospitals are offered based on current theory and research.