Graphene/PVDF Composites for Ni-rich Oxide Cathodes Toward High-Energy Density Li-ion Batteries.

Li-ion batteries (LIBs) employ porous, composite-type electrodes, where few weight percentages of carbonaceous conducting agents and polymeric binders are required to bestow electrodes with electrical conductivity and mechanical robustness. However, the use of such inactive materials has limited enhancements of battery performance in terms of energy density and safety. In this study, we introduced graphene/polyvinylidene fluoride (Gr/PVdF) composites in Ni-rich oxide cathodes for LIBs, replacing conventional conducting agents, carbon black (CB) nanoparticles. By using Gr/PVdF suspensions, we fabricated highly dense LiNi0.85Co0.15Al0.05O2 (NCA) cathodes having a uniform distribution of conductive Gr sheets without CB nanoparticles, which was confirmed by scanning spreading resistance microscopy mode using atomic force microscopy. At a high content of 99 wt.% NCA, good cycling stability was shown with significantly improved areal capacity (Qareal) and volumetric capacity (Qvol), relative to the CB/PVdF-containing NCA electrode with a commercial-level of electrode parameters. The NCA electrodes using 1 wt.% Gr/PVdF (0.9:0.1) delivered a high Qareal of ~3.7 mAh cm-2 (~19% increment) and a high Qvol of ~774 mAh cm-3 (~18% increment) at a current rate of 0.2 C, as compared to the conventional NCA electrode. Our results suggest a viable strategy for superseding conventional conducting agents (CB) and improving the electrochemical performance of Ni-rich cathodes for advanced LIBs.

Spectropolarimetric fluctuations in a sunspot chromosphere.

The instrumental advances made in this new era of 4 m class solar telescopes with unmatched spectropolarimetric accuracy and sensitivity will enable the study of chromospheric magnetic fields and their dynamics with unprecedented detail. In this regard, spectropolarimetric diagnostics can provide invaluable insight into magneto-hydrodynamic (MHD) wave processes. MHD waves and, in particular, Alfvénic fluctuations associated with particular wave modes were recently recognized as important mechanisms not only for the heating of the outer layers of the Sun's atmosphere and the acceleration of the solar wind, but also for the elemental abundance anomaly observed in the corona of the Sun and other Sun-like stars (also known as first ionization potential) effect. Here, we take advantage of state-of-the-art and unique spectropolarimetric Interferometric BIdimensional Spectrometer observations to investigate the relation between intensity and circular polarization (CP) fluctuations in a sunspot chromosphere. Our results show a clear link between the intensity and CP fluctuations in a patch which corresponds to a narrow range of magnetic field inclinations. This suggests the presence of Alfvénic perturbations in the sunspot. This article is part of the Theo Murphy meeting issue 'High-resolution wave dynamics in the lower solar atmosphere'.

Community pharmacy personnel interventions for smoking cessation.

BACKGROUND: Community pharmacists could provide effective smoking cessation treatment because they offer easy access to members of the community. They are well placed to provide both advice on the correct use of smoking cessation products and behavioural support to aid smoking cessation. OBJECTIVES: To assess the effectiveness of interventions delivered by community pharmacy personnel to assist people to stop smoking, with or without concurrent use of pharmacotherapy. SEARCH METHODS: We searched the Cochrane Tobacco Addiction Group Specialised Register, along with clinicaltrials.gov and the ICTRP, for smoking cessation studies conducted in a community pharmacy setting, using the search terms pharmacist* or pharmacy or pharmacies. Date of the most recent search: January 2019. SELECTION CRITERIA: Randomised controlled trials of interventions delivered by community pharmacy personnel to promote smoking cessation amongst their clients who were smokers, compared with usual pharmacy support or any less intensive programme. The main outcome measure was smoking cessation rates at six months or more after the start of the intervention. DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane for study screening, data extraction and management. We conducted a meta-analysis using a Mantel-Haenszel random-effects model to generate risk ratios (RRs) and 95% confidence intervals (CIs). MAIN RESULTS: We identified seven studies including 1774 participants. We judged three studies to be at high risk of bias and four to be at unclear risk. Each study provided face-to-face behavioural support delivered by pharmacy staff, and required pharmacy personnel training. Typically such programmes comprised support starting before quit day and continuing with weekly appointments for several weeks afterwards. Comparators were either minimal or less intensive behavioural support for smoking cessation, typically comprising a few minutes of one-off advice on how to quit. Participants in both intervention and control arms received equivalent smoking cessation pharmacotherapy in all but one study. All studies took place in high-income countries, and recruited participants visiting pharmacies. We pooled six studies of 1614 participants and detected a benefit of more intensive behavioural smoking cessation interventions delivered by community pharmacy personnel compared with less intensive cessation interventions at longest follow-up (RR 2.30, 95% CI 1.33 to 3.97; I2 = 54%; low-certainty evidence). AUTHORS' CONCLUSIONS: Community pharmacists can provide effective behavioural support to people trying to stop smoking. However, this conclusion is based on low-certainty evidence, limited by risk of bias and imprecision. Further research could change this conclusion.

T-cell receptor mimic (TCRm) antibody therapeutics against intracellular proteins.

T-cell receptor mimic (TCRm) antibodies combine the capacity of a T cell to target intracellular antigens with other capacities unique to antibodies. Neoantigens are abnormal proteins that arise as a consequence of somatic mutations. Technological advances promote the development of neoantigen-targeting therapies including TCRm antibody therapies. This review summarizes key characteristics of TCRm antibodies, in particular those targeting neoantigens, and further introduces discussion of obstacles that must be overcome to advance TCRm therapeutics.

Development of a method for direct extraction of viral RNA from bivalve molluscs.

The detection of foodborne viruses in bivalve molluscs is a challenging procedure in relation to low virus concentration and to the presence of significant RT-PCR inhibitors. The aim of this study was the development of an efficient direct extraction method for foodborne viral RNA from bivalve molluscs. Using Mengovirus as a surrogate for foodborne viruses, five extraction methods based on RNA release by Trizol were compared on clams and oysters. A procedure consisting of Trizol, PureLink RNA Mini Kit, followed by Cetyltrimethylammonium bromide (CTAB) treatment and LiCl precipitation was found to provide RNA with the highest extraction efficiency and negligible inhibitory effect on real-time RT-PCR. This procedure was further compared to standard extraction method (ISO 15216) using clam, mussel and oyster samples spiked with Hepatitis A virus, Norovirus (NoV) GI and GII as well as bivalve samples naturally contaminated with NoV GI or GII. Results clearly demonstrated that the developed method provided, on average, a recovery 4·3 times higher than the standard reference protocol as well as good repeatability. SIGNIFICANCE AND IMPACT OF THE STUDY: A direct extraction procedure was developed to recover viral RNA from shellfish with improved efficiency in comparison to reference extraction method (ISO 15216). Without the need for specific equipment, this procedure offers an alternative for performing food safety controls and for risk assessment studies. Given the inclusion in this extraction method of several steps for the efficient removal of food components inhibiting PCR reaction, this approach could serve as a general scheme for the extraction of nucleic acids of other enteric viruses and/or from other food categories.

Novel association of DJ-1 with HER3 potentiates HER3 activation and signaling in cancer.

HER3/ErbB3 has emerged as a new therapeutic target for cancer. Currently, more than a dozen anti-HER3 antibodies are in clinical trials for treatment of various cancers. However, limited understanding of the complex HER3 signaling in cancer and lack of established biomarkers have made it challenging to stratify cancer patients who can benefit from HER3 targeted therapies. In this study, we identified DJ-1/PARK7 (Parkinson Protein 7) as a novel interaction partner of HER3 and demonstrated the potential of DJ-1 as a biomarker for anti-HER3 cancer therapy. DJ-1 association with HER3 protects HER3 from ubiquitination and degradation through the proteasomal pathway in breast cancer cells. However, neuregulin 1 (NRG-1) mediated HER3 activation results in a reduced association of DJ-1 with HER3. DJ-1 shRNA knockdown in cancer cells resulted in decreased levels of HER3 and its downstream signaling through the PI3K/AKT and Ras/Raf/ERK pathways. DJ-1 shRNA knockdown cancer cells significantly reduced cell proliferation and migration in vitro and tumor growth in vivo. Conversely, overexpression of DJ-1 increased HER3 levels and promoted cancer cell proliferation in vitro and tumor growth in vivo. Notably, cancer cells with high DJ-1 expression showed more sensitivity than DJ-1 knockdown cells to anti-HER3 antibody inhibition. In addition, there was a significant co-expression of HER3 and DJ-1 in tumor tissues of breast cancer patients. Taken together, these results suggest that high DJ-1 expression in breast cancer cells predicts elevated HER3 signaling and may therefore serve as a biomarker for HER3 targeted antibody cancer therapies.

Increased Expression of EGR-1 in Diabetic Human Adipose Tissue-Derived Mesenchymal Stem Cells Reduces Their Wound Healing Capacity.

The prevalence of type 2 diabetes mellitus (T2DM), which leads to diabetic complications, has been increasing worldwide. The possible applications of T2DM-derived stem cells in cell therapy are limited because their characteristics are still not fully understood. In this study, we characterized adipose tissue-derived mesenchymal stem cells (AT-MSCs) from diabetic patients (dAT-MSCs) and found that insulin receptor substrate-1 (IRS-1) was highly phosphorylated at serine 636/639 in dAT-MSCs. Moreover, we found that early growth response factor-1 (EGR-1) and its target genes of PTEN and GGPS1 were highly expressed in dAT-MSCs in comparison to healthy donor-derived AT-MSCs (nAT-MSCs). We observed impaired wound healing after the injection of dAT-MSCs in the ischemic flap mouse model. The expressions of EGR-1 and its target genes were diminished by small hairpin RNA-targeted EGR-1 (shEGR-1) and treatment with a mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) inhibitor (PD98059). Importantly, dAT-MSCs with shEGR-1 were able to restore the wound healing ability in the mouse model. Interestingly, under hypoxic conditions, hypoxia-inducible factor-1α (HIF-1α) can bind to the EGR-1 promoter in dAT-MSCs, but not in nAT-MSCs. Together, these results demonstrate that the expression of EGR-1 was upregulated in dAT-MSCs through two pathways: the main regulatory pathway is the MAPK/ERK pathway, the other is mediated by HIF-1α through direct transcriptional activation at the promoter region of the EGR1 gene. Our study suggests that dAT-MSCs may contribute to microvascular damage and delay wound healing through the overexpression of EGR-1. Interrupting the expression of EGR-1 in dAT-MSCs may be a useful treatment for chronic wounds in diabetic patients.

Impaired expression of HIF-2α induces compensatory expression of HIF-1α for the recovery from anemia.

Erythropoiesis is strongly influenced by the interactions between stromal cells and erythroid progenitors, as well as by a key regulatory factor, erythropoietin (EPO). We previously generated mice with a knockdown mutation of Hif-2α (referred to as kd/kd) and found that these kd/kd mice exhibited normocytic anemia, even though the EPO expression was not severely affected. However, the VCAM-1 expression in spleen endothelial cells (EC), which is regulated by HIF-2α, was impaired, resulting in defective erythroid maturation. A deficiency of HIF-2α clearly led to pancytopenia. However, the critical level of HIF-2α required for erythropoiesis has not yet been elucidated. In this study, we generated HIF-2α knockdown/knockout heterozygous mice (kd/null). Strikingly, anemia was observed in the kd/null mice, but the red blood cell indices were significantly improved compared to those of kd/kd mice. In the spleens of kd/null mice, higher HIF-1α activity and expansion of the red pulp area were observed compared to those of kd/kd mice. Importantly, EC isolated from kd/null spleens showed high expression of VEGF receptors, FLK-1 and FLT-1, which are regulated by HIF-1α instead of HIF-2α under hypoxic conditions. We also found higher expression of phosphorylated ERK and higher proliferative activity in the EC isolated from kd/null mice compared to those from kd/kd mice. While the HIF-2α expression was diminished, HIF-1α bound to the HRE region in the promoters of genes that are normally regulated by HIF-2α. These results suggest that there is a compensatory pathway involving HIF-1α that regulates the expression of some HIF-2α target genes.

Dual functions of hypoxia-inducible factor 1 alpha for the commitment of mouse embryonic stem cells toward a neural lineage.

Embryonic stem (ES) cells are useful for elucidating the molecular mechanisms of cell fate decision in the early development of mammals. It has been shown that aggregate culture of ES cells efficiently induces neuroectoderm differentiation. However, the molecular mechanism that leads to selective neural differentiation in aggregate culture is not fully understood. Here, we demonstrate that the oxygen-sensitive hypoxia-inducible transcription factor, Hif-1α, is an essential regulator for neural commitment of ES cells. We found that a hypoxic environment is spontaneously established in differentiating ES cell aggregates within 3 days, and that this time window coincides with Hif-1α activation. In ES cells in adherent culture under hypoxic conditions, Hif-1α activation was correlated with significantly greater expression of neural progenitor-specific gene Sox1 compared with ES cells in adherent culture under normoxic conditions. In contrast, Hif-1α-depleted ES cell aggregates showed severe reduction in Sox1 expression and maintained high expression of undifferentiated ES cell marker genes and epiblast marker gene Fgf5 on day 4. Notably, chromatin immune precipitation assay and luciferase assay showed that Hif-1α might directly activate Sox1 expression. Of additional importance is our finding that attenuation of Hif-1α resulted in an increase of BMP4, a potent inhibitor of neural differentiation, and led to a high level of phosphorylated Smad1. Thus, our results indicate that Hif-1α acts as a positive regulator of neural commitment by promoting the transition of ES cell differentiation from the epiblast into the neuroectoderm state via direct activation of Sox1 expression and suppressing endogenous BMP signaling.

Clusterin regulates ß-amyloid toxicity via Dickkopf-1-driven induction of the wnt-PCP-JNK pathway.

Although the mechanism of Aß action in the pathogenesis of Alzheimer's disease (AD) has remained elusive, it is known to increase the expression of the antagonist of canonical wnt signalling, Dickkopf-1 (Dkk1), whereas the silencing of Dkk1 blocks Aß neurotoxicity. We asked if clusterin, known to be regulated by wnt, is part of an Aß/Dkk1 neurotoxic pathway. Knockdown of clusterin in primary neurons reduced Aß toxicity and DKK1 upregulation and, conversely, Aß increased intracellular clusterin and decreased clusterin protein secretion, resulting in the p53-dependent induction of DKK1. To further elucidate how the clusterin-dependent induction of Dkk1 by Aß mediates neurotoxicity, we measured the effects of Aß and Dkk1 protein on whole-genome expression in primary neurons, finding a common pathway suggestive of activation of wnt-planar cell polarity (PCP)-c-Jun N-terminal kinase (JNK) signalling leading to the induction of genes including EGR1 (early growth response-1), NAB2 (Ngfi-A-binding protein-2) and KLF10 (Krüppel-like factor-10) that, when individually silenced, protected against Aß neurotoxicity and/or tau phosphorylation. Neuronal overexpression of Dkk1 in transgenic mice mimicked this Aß-induced pathway and resulted in age-dependent increases in tau phosphorylation in hippocampus and cognitive impairment. Furthermore, we show that this Dkk1/wnt-PCP-JNK pathway is active in an Aß-based mouse model of AD and in AD brain, but not in a tau-based mouse model or in frontotemporal dementia brain. Thus, we have identified a pathway whereby Aß induces a clusterin/p53/Dkk1/wnt-PCP-JNK pathway, which drives the upregulation of several genes that mediate the development of AD-like neuropathologies, thereby providing new mechanistic insights into the action of Aß in neurodegenerative diseases.

Current and emerging pharmacotherapeutic options for smoking cessation.

Tobacco smoking remains the single most preventable cause of morbidity and mortality in developed countries and poses a significant threat across developing countries where tobacco use prevalence is increasing. Nicotine dependence is a chronic disease often requiring multiple attempts to quit; repeated interventions with pharmacotherapeutic aids have become more popular as part of cessation therapies. First-line medications of known efficacy in the general population include varenicline tartrate, bupropion hydrochloride, nicotine replacement therapy products, or a combination thereof. However, less is known about the use of these products in marginalized groups such as the indigenous, those with mental illnesses, youth, and pregnant or breastfeeding women. Despite the efficacy and safety of these first line pharmacotherapies, many smokers continue to relapse and alternative pharmacotherapies and cessation options are required. Thus, the aim of this review is to summarize the existing and developing pharmacotherapeutic and other options for smoking cessation, to identify gaps in current clinical practice, and to provide recommendations for future evaluations and research.

Umbilical cord blood-derived mesenchymal stem cells inhibit, but adipose tissue-derived mesenchymal stem cells promote, glioblastoma multiforme proliferation.

Mesenchymal stem cells (MSCs) possess self-renewal and multipotential differentiation abilities, and they are thought to be one of the most reliable stem cell sources for a variety of cell therapies. Recently, cell therapy using MSCs has been studied as a novel therapeutic approach for cancers that show refractory progress and poor prognosis. MSCs from different tissues have different properties. However, the effect of different MSC properties on their application in anticancer therapies has not been thoroughly investigated. In this study, to characterize the anticancer therapeutic application of MSCs from different sources, we established two different kinds of human MSCs: umbilical cord blood-derived MSCs (UCB-MSCs) and adipose-tissue-derived MSCs (AT-MSCs). We used these MSCs in a coculture assay with primary glioblastoma multiforme (GBM) cells to analyze how MSCs from different sources can inhibit GBM growth. We found that UCB-MSCs inhibited GBM growth and caused apoptosis, but AT-MSCs promoted GBM growth. Terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick-end labeling assay clearly demonstrated that UCB-MSCs promoted apoptosis of GBM via tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL was expressed more highly by UCB-MSCs than by AT-MSCs. Higher mRNA expression levels of angiogenic factors (vascular endothelial growth factor, angiopoietin 1, platelet-derived growth factor, and insulin-like growth factor) and stromal-derived factor-1 (SDF-1/CXCL12) were observed in AT-MSCs, and highly vascularized tumors were developed when AT-MSCs and GBM were cotransplanted. Importantly, CXCL12 inhibited TRAIL activation of the apoptotic pathway in GBM, suggesting that AT-MSCs may support GBM development in vivo by at least two distinct mechanisms-promoting angiogenesis and inhibiting apoptosis. The opposite effects of AT-MSCs and UCB-MSCs on GBM clearly demonstrate that differences must be considered when choosing a stem cell source for safety in clinical application.

Review of biophysical factors affecting osteogenic differentiation of human adult adipose-derived stem cells.

Developing bone is subject to the control of a broad variety of influences in vivo. For bone repair applications, in vitro osteogenic assays are routinely used to test the responses of bone-forming cells to drugs, hormones, and biomaterials. Results of these assays are used to predict the behavior of bone-forming cells in vivo. Stem cell research has shown promise for enhancing bone repair. In vitro osteogenic assays to test the bone-forming response of stem cells typically use chemical solutions. Stem cell in vitro osteogenic assays often neglect important biophysical cues, such as the forces associated with regular weight-bearing exercise, which promote bone formation. Incorporating more biophysical cues that promote bone formation would improve in vitro osteogenic assays for stem cells. Improved in vitro osteogenic stimulation opens opportunities for "pre-conditioning" cells to differentiate towards the desired lineage. In this review, we explore the role of select biophysical factors-growth surfaces, tensile strain, fluid flow and electromagnetic stimulation-in promoting osteogenic differentiation of stem cells from human adipose. Emphasis is placed on the potential for physical microenvironment manipulation to translate tissue engineering and stem cell research into widespread clinical usage.

The controlled growth of single metallic and conducting polymer nanowires via gate-assisted electrochemical deposition.

The fabrication of nanowires with well-controlled lengths and diameters is the basis of the application of one-dimensional nanostructures in more sophisticated electronic and biomolecular device systems. A wide variety of materials, including metals and conducting polymers, have been utilized in nanowire arrays as building blocks for chemical or biomolecular sensors. Thus far, the cheapest and most effective way of nanowire synthesis is electrochemical deposition. In this work, we investigate a new method of electrochemical deposition using two-dimensional electric fields instead of the conventional one-directional electric field between working electrodes. Reproducible fabrication of metallic (palladium) and conducting polymer (polypyrrole) single nanowires with diameters down to 30-50 nm is achieved by application of a vertical gate electric field in addition to the lateral one between the two working electrodes. Diameters and lengths of the nanowires can be easily controlled by varying the dimensions of the nanochannels in which the nanowires are grown. A good ohmic contact between the nanowire and gold electrodes is also obtained, indicating the feasibility of electronic devices based on the single nanowires synthesized via this method. In conjunction with experimental findings of nanowire growth mechanism under two-dimensional electric field, molecular dynamic simulations are employed to further understand the deposition process. This improved electrochemical deposition is applicable for controlled and simple fabrication of a wide range of metallic and conducting polymeric nanowires with small diameters.

[Disproportionately high left ventricular myocardial mass in patients with arterial hypertension].

BACKGROUND: Increase of myocardial mass of left ventricle (MMLV) to a greater extent than required by hemodynamic load by elevated arterial pressure (AP) is reflected in concepts of " disproportionately " high (DH) MMLV and resistant to antihypertensive treatment LV hypertrophy (LVH). AIM: To study in patients with arterial hypertension (AH) frequency of DH MMLV and factors associated with it. MATERIAL AND METHODS: Patients (n=170, 70 men, age 57.6+/-5.9 years) with previously untreated or irregularly treated uncontrollable AH. Proportionality of MMLV was assessed by coefficient of disproportionality (CD) defined as ratio of actual to expected MMLV. RESULTS: DH MMLV was found in 140 patients (82.4%). Frequency of ECHOCG LVH among patients with DH MMLV was 49.3%. There were no cases of LVH among patients with proportional MMLV. Frequency of LVH depended on severity of disproportionality of MMLV elevation and was 18.9% at CD 128-155.9% and 82.2% at CD 184%. Patients with DH MMLV were characterized by greater body mass index, higher rate of disturbances of carbohydrate and lipid metabolism. Patients with DH MMLV without compared with those with LVH were characterized by significantly higher rate of concentric variant of LV geometry (66.2 vs 40.6%, p<0.05) and diastolic dysfunction (57.7 vs 36.2%, p<0.05), lower values of parameters of systolic LV function and higher rate of combination of concentric remodelling and diastolic LV dysfunction. CONCLUSION: DH MMLV is frequent among patients with previously untreated or irregularly treated uncontrollable AH. Calculation of disproportionality of MMLV allows to give additional characteristic of morphofunctional state of the myocardium in patients with AH. DH MMLV is associated with complex of subclinical structurally-functional disturbances of the myocardium and unfavourable changes of carbohydrate and lipid metabolism.

Characterization of the laser-based release of micropallets from arrays.

The micropallet array system uses a pulsed laser to release pallets tens of microns to hundreds of micrometers in size from a larger array, enabling selective isolation of single cells adherent to the pallets. We characterize the laser-based release of pallets with respect to pallet array and laser parameters. The threshold laser energy required for pallet release increases linearly with the area of the pallet in contact with the underlying glass substrate. The spacing of the pallets within an array as well as the thickness or height of the pallet does not impact the energy required to release a pallet. Delivery of multiple laser pulses decreases the energy/pulse required for pallet release when the pallets were 100 microm or greater on a side. In addition to the square pallets, complex structures such as cantilevers and spirals could be released without damage using the pulsed laser. Identification of the pallet-array variables influencing the energy required for pallet release as well as strategies to minimize this energy will prove critical in optimizing the release of pallets with cells on the arrays.

Mechanisms of pulsed laser microbeam release of SU-8 polymer "micropallets" for the collection and separation of adherent cells.

The release of individual polymer micropallets from glass substrates using highly focused laser pulses has been demonstrated for the efficient separation, collection, and expansion of single, adherent cells from a heterogeneous cell population. Here, we use fast-frame photography to examine the mechanism and dynamics of micropallet release produced by pulsed laser microbeam irradiation at lambda = 532 nm using pulse durations ranging between 240 ps and 6 ns. The time-resolved images show the laser microbeam irradiation to result in plasma formation at the interface between the glass coverslip and the polymer micropallet. The plasma formation results in the emission of a shock wave and the ablation of material within the focal volume. Ablation products are generated at high pressure due to the confinement offered by the polymer adhesion to the glass substrate. The ablation products expand underneath the micropallet on a time scale of several hundred nanoseconds. This expansion disrupts the polymer-glass interface and accomplishes the release of the pallet from its glass substrate on the microsecond time scale (approximately 1.5 micros). Our experimental investigation demonstrates that the threshold energy for pallet release is constant (approximately 2 microJ) over a 25-fold range of pulse duration spanning the picosecond to nanosecond domain. Taken together, these results implicate that pallet release accomplished via pulsed laser microbeam irradiation is an energy-driven plasma-mediated ablation process.

Micropallet arrays with poly(ethylene glycol) walls.

Arrays of releasable micropallets with surrounding walls of poly(ethylene glycol) (PEG) were fabricated for the patterning and sorting of adherent cells. PEG walls were fabricated between the SU-8 pallets using a simple, mask-free strategy. By utilizing the difference in UV-transmittance of glass and SU-8, PEG monomer was selectively photopolymerized in the space surrounding the pallets. Since the PEG walls are composed of a cross-linked structure, the stability of the walls is independent of the pallet array geometry and the properties of the overlying solution. Even though surrounded with PEG walls, the individual pallets were detached from the array by the mechanical force generated by a focused laser pulse, with a release threshold of 6 microJ. Since the PEG hydrogels are repellent to protein adsorption and cell attachment, the walls localized cell growth to the pallet top surface. Cells grown in the microwells formed by the PEG walls were released by detaching the underlying pallet. The released cells/pallets were collected, cultured and clonally expanded. The micropallet arrays with PEG walls provide a platform for performing single cell analysis and sorting on chip.

Photoresist with low fluorescence for bioanalytical applications.

The negative photoresist SU-8 has found widespread use as a material in the fabrication of microelectrical-mechanical systems (MEMS). Although SU-8 has been utilized as a structural material for biological MEMS, a number of SU-8 properties limit its application in these bioanalytical devices. These attributes include its brittleness, nonspecific adsorption of biomolecules, and high fluorescence in the visible wavelengths. In addition, native SU-8 is a poor substrate for cellular adhesion. Photoresists composed of resins with epoxide side groups and photoacids were screened for their ability to serve as a low-fluorescence photoresist with sufficient resolution to generate microstructures with dimensions of 5-10 microm. The fluorescence of structures formed from 1002F photoresist (1002F resin combined with triarylsulfonium hexafluoroantimonate salts) was as much as 10 times less fluorescent than similar SU-8 microstructures. The absorbance of 1002F in the visible wavelengths was also substantially lower than that of SU-8. Microstructures or pallets with an aspect ratio as high as 4:1 could be formed permitting 1002F to be used as a structural material in the fabrication of arrays of pallets for sorting adherent cells. Several different cell types were able to adhere to native 1002F surfaces, and the viability of these cells was excellent. As with SU-8, 1002F has a weak adhesion to glass, a favorable attribute when the pallet arrays are used to sort adherent cells. A threshold, laser pulse energy of 3.5 microJ was required to release individual 50 microm, 1002F pallets from an array. Relative to SU-8, 1002F photoresist offers substantial improvements as a substrate in bioanalytical devices and is likely to find widespread use in BioMEMS.