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At least 955 records · Page 53Linked to original sources

PubMed2001

Study of microcontact printed patterns by chemical force microscopy.

Patterned self-assembled monolayers (SAMs) on sputtered gold films prepared by microcontact printing (microCP) were studied by mapping adhesive forces with pulsed-force-mode atomic force microscopy. A stamp for microCP was fabricated by pouring polydimethylsiloxane (PDMS) over a photolithographically prepared master. The patterned SAMs were prepared by two methods. One is called the wet-inking method, in which inking was done by placing a thiol ethanol solution for 30 s on the stamp and then removing the excess ink solution under a stream of nitrogen. The other is called the contact-inking method, in which a pad made of PDMS was dipped overnight in a thiol ethanol solution and then the stamp was placed on the inker pad impregnated with the thiol ethanol solution. The second step for pattern formation was the same for both of the two different microCP methods. Namely, the gold surfaces stamped with alkanethiols were further reacted with a thiol terminating in COOH in ethanol. The resulting patterns with CH3- and COOH-terminated regions were analyzed by imaging the adhesive forces with the chemically modified gold coated AFM tips with a SAM of CH3 or COOH terminal functional groups.

Journal Article↗

PubMed1998

Diffraction-based cell detection using a microcontact printed antibody grating.

An optical detector has been fabricated that is specific for targeted bacterial cells, by stamping an antibody grating pattern on a silicon surface. The antibody grating alone produces insignificant optical diffraction, but upon immunocapture of cells, the optical phase change produces a diffraction pattern. This technique eliminates much of the surface modifications and the secondary immunochemical or enzyme-linked steps that are common in immunoassays. Microcontact printing provides an alternative to previously reported photolithographic-mediated antibody patterning processes and uses a photolithographic process simply to produce the elastomeric stamp. We have stamped antibodies directly onto clean native oxide silicon substrates with no other chemical surface treatments. Direct binding of the antibodies to the silicon occurs in a way that still allows them to function and selectively bind antigen. The performance of the sensor was evaluated by capturing Escherichia coli O157:H7 cells on the antibody-stamped lines and measuring the intensity of the first-order diffraction beam resulting from the attachment of cells. The diffraction intensity increases in proportion to the cell density bound on the surface.

Antibodies↗

PubMed2005

Photopatternable silicon elastomers with enhanced mechanical properties for high-fidelity nanoresolution soft lithography.

Soft lithography has been widely used in stamping and printing processes for microfabrication as a low cost alternative to photolithography. However, conventional poly(dimethyl)siloxane (PDMS) stamp materials have limitations, especially in the submicrometer range, due to their low physical toughness and requirements for thermocuring. A new version of functional stamp materials with adjustable physical toughness has been developed for advanced soft lithography. We thus demonstrate here its photopatternability and nanoresolution soft lithography, which have proven to be difficult using commercial stamp materials.

Journal Article↗

PubMed2004

Molecular transfer and transport in noncovalent microcontact printing.

Microcontact printing is commonly used to create patterned films of molecules covalently bonded to substrates (e.g., thiols on gold). Here we describe microcontact printing of several types of noncovalently bonding molecules on mica. Due to the weaker interaction of the molecules with the substrate, environmental factors such as temperature and relative humidity play an important role. The vapor pressure of the inks also had a large impact on the fidelity of the stamped patterns. Fingering instabilities were observed for monolayers of octadecanol, docosanol, stearylamine, and stearic acid stamped at moderate relative humidity. The fidelity of the stamped pattern generally increased with the headgroup-surface interaction strength. These stamped monolayer films shed light on molecular transfer and two-dimensional spreading mechanisms.

Journal Article↗

PubMed2004

Controlling mammalian cell interactions on patterned polyelectrolyte multilayer surfaces.

A newly discovered class of cell resistant surfaces, specifically engineered polyelectrolyte multilayers, was patterned with varying densities of adhesion ligands to control attachment of mammalian cells and to study the effects of ligand density on cell activity. Cell adhesive patterns were created on cell resistant multilayer films composed of poly(acrylic acid) and polyacrylamide through polymer-on-polymer stamping of poly(allylamine hydrochloride) PAH and subsequent reaction of the amine functional groups with an adhesion ligand containing RGD (Arg-Gly-Asp). These cell patterns demonstrated great promise for long-term applications since they remained stable for over 1 month, unlike ethylene glycol functional surfaces. By changing the stamping conditions of PAH, it was possible to alter the number of available functional groups in the patterned regions, and as a result, control the ligand density. Cell spreading, morphology, and cytoskeletal organization were compared at four different RGD densities. The highest RGD density, approximately 152 000 molecules/microm2, was created by stamping PAH at a pH of 11.0. Lowering the stamping ink pH led to patterns with lower ligand surface densities (83 000 molecules/microm2 for pH 9.0, 53,000 molecules/ microm2 for pH 7.0, and 25 000 molecules/microm2 for pH 3.5). An increasing number of cells attached and spread as the RGD density of the patterns increased. In addition, more cells showed well-defined actin stress fibers and focal adhesions at higher levels of RGD density. Finally, we found that pattern geometry affected cytoskeletal protein organization. Well-formed focal adhesions and cell-spanning stress fibers were only found in cells on wider line patterns (at least 25 microm in width).

Acrylic Resins↗

PubMed2005

Microcontact printing of proteins inside microstructures.

Microfluidic devices are well suited for the miniaturization of biological assays, in particular when only small volumes of samples and reagents are available, short time to results is desirable, and multiple analytes are to be detected. Microfluidic networks (MFNs), which fill by means of capillary forces, have already been used to detect important biological analytes with high sensitivity and in a combinatorial fashion. These MFNs were coated with Au, onto which a hydrophilic, protein-repellent monolayer of thiolated poly(ethyleneglycol) (HS-PEG) was self-assembled, and the binding sites for analytes were present on a poly(dimethylsiloxane) (PDMS) sealing cover. We report here a set of simple methods to extend previous work on MFNs by integrating binding sites for analytes inside the microstructures of MFNs using microcontact printing (muCP). First, fluorescently labeled antibodies (Abs) were microcontact-printed from stamps onto planar model surfaces such as glass, Si, Si/SiO2, Au, and Au derivatized with HS-PEG to investigate how much candidate materials for MFNs would quench the fluorescence of printed, labeled Abs. Au coated with HS-PEG led to a fluorescence signal that was approximately 65% weaker than that of glass but provided a convenient surface for printing Abs and for rendering the microstructures of the MFNs wettable. Then, proteins were inked from solution onto the surface of PDMS (Sylgard 184) stamps having continuous or discontinuous micropatterns or locally inked onto planar stamps to investigate how the aspect ratio (depth:width) of microstructures and the printing conditions affected the transfer of protein and the accuracy of the resulting patterns. By applying a controlled pressure to the back of the stamp, Abs were accurately microcontact-printed into the recessed regions of MFNs if the aspect ratio of the MFN microstructures was lower than approximately 1:6. Finally, the realization of a simple assay between Abs (used as antigens) microcontact-printed in microchannels and Abs from solution suggests that this method could become useful to pattern proteins in microstructures for advanced bioanalytical purposes.

Antibodies↗

PubMed2005

Microscale plasma-initiated patterning (muPIP).

A novel technique to create biomolecular micropatterns of varying complexity on several types of polymer substrates is presented. This method uses a patterned PDMS stamp to preferentially expose or protect areas of an underlying polymer substrate from oxygen plasma. Following plasma treatment, the substrate is immersed in a biomolecular ink, whereby molecules preferentially adsorb to either the plasma-exposed or plasma-protected substrate regions, depending on the particular substrate/ink combination. Using this method, polyethylene (PE), polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(dimethylsiloxane) (PDMS), and poly(hydroxybutyrate/hydroxyvalerate) (PHBV) were micropatterned with different aqueous-based biomolecular inks (i.e., goat anti-rabbit immunoglobulin G, poly-l-lysine, and bovine serum albumin (BSA)). Water contact angle measurements performed on substrates after oxygen plasma exposure showed that the hydrophilicity of substrate areas exposed to plasma was significantly greater than that of areas protected from plasma by the PDMS stamp. In addition, scanning electron microscopy results demonstrated that substrate areas exposed to plasma were physically modified (e.g., roughened) compared to adjacent, protected areas. Areas in contact with a patterned PDMS stamp during plasma exposure were found to be physically unaffected by plasma treatment, and exhibited spatial features/dimensions consistent with the corresponding features of the patterned stamp. Last, protein patterns of BSA on the polymer substrates were stable and distinct after 4 weeks of incubation at 37 degrees C.

Microscopy, Electron, Scanning↗

PubMed2006

Three-dimensional metallized features on polymeric substrates by microcontact printing.

We demonstrate the formation of 3-D metallized features on a polymeric substrate by microcontact printing. A patterned silicon stamp was "inked" with catalytic particles. Thereafter, particles were selectively removed from the raised regions of the stamp. A molten polymer was embossed against the stamp. Upon cooling and separation, the catalytic particles that were within the recessed areas of the stamp were transferred to the polymer. The polymer was then immersed in an electroless plating bath, and metallization occurred selectively on the areas where the catalytic particles were present. We have achieved 3-D metallized columns as small as 500 nm in diameter and about 1 mum tall.

Journal Article↗

PubMed2006

Control of self-organized contact instability and patterning in soft elastic films.

The surface of a soft elastic film becomes unstable and forms a labyrinth pattern when a rigid flat plate is brought into adhesive contact, without application of any external pressure. These isotropic undulations have a characteristic wavelength, lambda approximately 3H, where H is the film thickness. We present here technique of ordering, aligning, and modulating these micro-labyrinth structures by using a patterned stamp, by varying the stamp-film inter-surface distance, by a lateral confinement of the instability and even by a simple shear motion of a flat stamp. Many complex structures, such as an array of femto-liter beakers and doubly periodic channels, are generated from a simple stamp consisting of parallel channels. The elastic nature of the patterns allows an in-situ tuning, manipulation, and reconfiguration of the microstructures. Regardless of their precise morphology, the structures continue to have the elastic length scale, lambda approximately 3H. The structures can also be made permanent as required by UV-ozone-induced oxidation of the structures. The underlying principles of the elastic contact instability presented here have the potential to develop into a new soft lithography technique-elastic contact lithography (ECL), allowing a simple, rapid and large area patterning of soft solids.

Journal Article↗

PubMed2004

Multicolour micropatterning of thin films of dry gels.

Micropatterning of surfaces with several chemicals at different spatial locations usually requires multiple stamping and registration steps. Here, we describe an experimental method based on reaction-diffusion phenomena that allows for simultaneous micropatterning of a substrate with several coloured chemicals. In this method, called wet stamping (WETS), aqueous solutions of two or more inorganic salts are delivered onto a film of dry, ionically doped gelatin from an agarose stamp patterned in bas relief. Once in conformal contact, these salts diffuse into the gelatin, where they react to give deeply coloured precipitates. Separation of colours in the plane of the surface is the consequence of the differences in the diffusion coefficients, the solubility products, and the amounts of different salts delivered from the stamp, and is faithfully reproduced by a theoretical model based on a system of reaction-diffusion partial differential equations. The multicolour micropatterns are useful as non-binary optical elements, and could potentially form the basis of new applications in microseparations and in controlled delivery.

Chlorides↗

PubMed1999

Paediatrica philatelica.

The world's nations issue postage stamps with themes that their governments regard as being of significant national and international importance. The philatelic record, thus, parallels each nation's history, its themes of contemporary pride and its aspirations for the future. As children's health is one of the most important of all issues of public and political life, it is not surprising that paediatricians are permanently commemorated in many of the world's postage stamps. Hippocrates is portrayed on many of the world's stamps, as are children's illnesses and children's doctors. Paediatricians are portrayed on stamps from New Zealand, Papua New Guinea, Australia, the United States of America, the nations of Africa, Europe and the United Nations. Themes permanently recorded in the philatelic record encompass every discipline within paediatrics, including portraits of Dr Virginia Apgar (of the Apgar score), Dr Truby King (New Zealand) who was responsible for the introduction of universal postnatal nursing visits for every child, and Dr Janusz Korczak (1879-1942), the Polish paediatrician who gave his life at Treblinka in World War II in order that his child patients might not die alone. The paediatric philatelic record is thus an international repository of the chronology of child care.

Child↗

PubMed1999

Smoking status as a vital sign.

OBJECTIVE: We conducted this study to determine if a smoking status stamp would prompt physicians to increase the number of times they ask, advise, assist, and arrange follow-up for African-American patients about smoking-related issues. DESIGN: An intervention study with a posttest assessment (after the physician visit) conducted over four 1-month blocks. The control period was the first 2 weeks of each month, while the following 2 weeks served as the intervention period. SETTING: An adult walk-in clinic in a large inner-city hospital. PARTICIPANTS: We consecutively enrolled into the study 2,595 African-American patients (1,229 intervention and 1, 366 control subjects) seen by a housestaff physician. INTERVENTIONS: A smoking status stamp placed on clinic charts during the intervention period. MAIN RESULTS: Forty-five housestaff rotated through the clinic in 1-month blocks. In univariate analyses, patients were significantly more likely to be asked by their physicians if they smoke cigarettes during the intervention compared with the control period, 78.4% versus 45.6% (odds ratio [OR] 4.28; 95% confidence interval [CI] 3.58, 5.10). Patients were also more likely to be told by their physician to quit, 39.9% versus 26.9% (OR 1.81; 95% CI 1.36, 2.40), and have follow-up arranged, 12.3% versus 6.2% (OR 2.16; 95% CI 1.30, 3.38). CONCLUSIONS: The stamp had a significant effect on increasing rates of asking about cigarette smoking, telling patients to quit, and arranging follow-up for smoking cessation. However, the stamp did not improve the low rate at which physicians offered patients specific advice on how to quit or in setting a quit date.

Adult↗

PubMed1999

A behaviour study on the potential for direct transmission of tuberculosis from possums (Trichosurus vulpecula) to alpacas (Lama pacos), and the converse from alpacas to possums.

AIMS: To evaluate the potential for the direct transmission of tuberculosis from possums to alpacas, and vice versa. METHODS: A field study was conducted on an alpaca farm in Northland, New Zealand on 7 January 1999. Observations were recorded on the interaction of one group of male alpacas with a simulated dead possum, one male and one female alpaca group with a simulated terminally tuberculous possum, and one group of male alpacas with a normal possum in an enclosure from which the animals could not escape. The possum was sedated with ketamine as hydrochloride to simulate death (inactive; no movement), and terminal illness (active, inco-ordinated movement around the paddock). The observations were based on the focal animal sampling technique, they were un-replicated, and recorded visually and manually with intermittent still photography. RESULTS: Both male and female alpacas showed strongly inquisitive interaction with the possum. They clustered around the possum (focal animal) very soon after it was observed by the first member of the group. The interest of the majority of both sex groups remained high for the observation periods of approximately 30 minutes, and most individuals remained within 5 metres of the possum for that time. Approximately 50% of the alpacas were within possible aerosol transmission distance of 2 metres from the sedated, erratically mobile possum with their heads towards it for approximately 50% of the two observation periods. Aggressive behaviour was recorded for a young male with stamping on the moving possum. Similar, but more vigorous and prolonged stamping behaviour was recorded for a female with a young (<1 week) offspring (cria). The stamping behaviour was accompanied by very close nose to nose contact of the alpaca and possum. At one point the female threw the possum approximately 1.5 metres in the air with her teeth. The group of male alpacas placed in an enclosure with an unsedated normal possum generally moved away from the possum during its rapid active attempts to escape. When it became inactive their approaches were cautious and only once elicited a defence reaction from the possum, from which they recoiled. One male made one attempt to stamp on the active possum. Soon after the possum became inactive in a small loose hay pile, the alpacas lost interest in it. CONCLUSIONS: The alpaca / possum behavioural interactions show there is potential for direct aerosol transmission of tuberculosis from possums to alpacas, but probably not from alpacas to possums.

Journal Article↗

PubMed2004

A multicenter international evaluation of single-tube amplification protocols for sequencing-based typing of HLA-DRB1 and HLA-DRB3,4,5.

We have described previously a novel single-tube polymerase chain reaction (PCR) amplification (STAmp) protocol for the efficient sequencing-based typing (SBT) of human leukocyte antigen (HLA)-DRB1. The PCR amplification mix includes primers to each of seven allele group-sequence motifs. We have applied this principle to the simultaneous SBT of HLA-DRB3, -DRB4, and -DRB5 using locus specific primers. We report here a multicenter international evaluation of the STAmp protocols performed as a component of the 13th International Histocompatibility Workshop. Identical amplification primer mixes, sequencing primers, and DNA were sent to participating laboratories. The primer mixes contained the amplification primers and the PCR buffer. Each laboratory was requested to amplify the DNA with the primer mixes and perform SBT on the resulting PCR protocols, using their own protocols, and return the typing results for analysis. The reported results indicated that the expected sequence could be obtained with a variety of PCR amplification and sequencing platforms and protocols. There were difficulties but these seemed unrelated to STAmp reagents and suggest that optimal SBT results can be obtained if bi-directional sequencing is performed and software is used for sequence verification and editing. This indicates that SBT by STAmp can be applied in many laboratories for high-throughput HLA-DRB1 and HLA-DRB3,4,5 SBT.

Alleles↗

PubMed2000

Micropatterning of organic electronic devices by cold-welding

A simple and general postdeposition electrode patterning technique for active organic electronic devices is demonstrated and is applied to patterning the metal cathodes of organic light-emitting devices. Selective lift-off of the metal cathode layer is achieved by pressing a prepatterned, metal-coated silicon stamp on the unpatterned device layers. Under pressure, the metal coating on the stamp cold-welds to the metal cathode coating the underlying organic films. Subsequent separation of the stamp from the substrate results in removal of the cathode metal in the regions contacted by the stamp, resulting in submicrometer feature definition. A 17x17 passive matrix display, with a pixel size of 440 micrometers by 320 micrometers, was fabricated with this process. Cold-welding followed by lift-off of the cathode metal allows simple, cost-effective, and high-throughput large-area fabrication of organic electronic devices.

Journal Article↗

PubMed2006

Targeted killing of Streptococcus mutans by a pheromone-guided "smart" antimicrobial peptide.

Within the repertoire of antibiotics available to a prescribing clinician, the majority affect a broad range of microorganisms, including the normal flora. The ecological disruption resulting from antibiotic treatment frequently results in secondary infections or other negative clinical consequences. To address this problem, our laboratory has recently developed a new class of pathogen-selective molecules, called specifically (or selectively) targeted antimicrobial peptides (STAMPs), based on the fusion of a species-specific targeting peptide domain with a wide-spectrum antimicrobial peptide domain. In the current study, we focused on achieving targeted killing of Streptococcus mutans, a cavity-causing bacterium that resides in a multispecies microbial community (dental plaque). In particular, we explored the possibility of utilizing a pheromone produced by S. mutans, namely, the competence stimulating peptide (CSP), as a STAMP targeting domain to mediate S. mutans-specific delivery of an antimicrobial peptide domain. We discovered that STAMPs constructed with peptides derived from CSP were potent against S. mutans grown in liquid or biofilm states but did not affect other oral streptococci tested. Further studies showed that an 8-amino-acid region within the CSP sequence is sufficient for targeted delivery of the antimicrobial peptide domain to S. mutans. The STAMPs presented here are capable of eliminating S. mutans from multispecies biofilms without affecting closely related noncariogenic oral streptococci, indicating the potential of these molecules to be developed into "probiotic" antibiotics which could selectively eliminate pathogens while preserving the protective benefits of a healthy normal flora.

Anti-Bacterial Agents↗

PubMed2004

Maternal depression, changing public assistance, food security, and child health status.

OBJECTIVE: To examine the association of positive report on a maternal depression screen (PDS) with loss or reduction of welfare support and foods stamps, household food insecurity, and child health measures among children aged < or =36 months at 6 urban hospitals and clinics. METHODS: A convenience sample of 5306 mothers, whose children <36 months old were being seen in hospital general clinics or emergency departments (EDs) at medical centers in 5 states and Washington, District of Columbia, were interviewed from January 1, 2000 until December 31, 2001. Questions included items on sociodemographic characteristics, federal program participation and changes in federal benefits, child health status rating, child's history of hospitalizations since birth, household food security status, and a 3-question PDS. For a subsample interviewed in the ED, whether the child was admitted to the hospital that day was recorded. RESULTS: PDS status was associated with loss or reduction of welfare support and food stamps, household food insecurity, fair/poor child health rating, and history of child hospitalization since birth but not low child growth status measures or admission to the hospital at the time of ED visit. After controlling for study site, maternal race, education, and insurance type as well as child low birth weight status, mothers with PDS were more likely to report fair/poor child health (adjusted odds ratio [AOR]: 1.58; 95% confidence interval [CI]: 1.33-1.88) and hospitalizations during the child's lifetime (AOR: 1.20; 95% CI: 1.03-1.39), compared with mothers without PDS. Controlling for the same variables, mothers with PDS were more likely to report decreased welfare support (AOR: 1.52; 95% CI: 1.03-2.25), to have lost food stamps (AOR: 1.56; 95% CI: 1.06-2.30), and reported more household food insecurity (AOR: 2.69; 95% CI: 2.33-3.11) than mothers without PDS. CONCLUSION: Positive maternal depression screen status noted in pediatric clinical samples of infants and toddlers is associated with poorer reported child health status, household food insecurity, and loss of federal financial support and food stamps. Although the direction of effects cannot be determined in this cross-sectional survey, child health providers and policy makers should be aware of the potential impact of maternal depression on child health in the context of welfare reform.

Body Weight↗

PubMed1987

The long-term effects of a token economy on safety performance in open-pit mining.

A token economy that used trading stamps as tokens was instituted at two dangerous open-pit mines. Employees earned stamps for working without lost-time injuries, for being in work groups in which all other workers had no lost-time injuries, for not being involved in equipment-damaging accidents, for making adopted safety suggestions, and for unusual behavior which prevented an injury or accident. They lost stamp awards if they or other workers in their group were injured, caused equipment damage, or failed to report accidents or injuries. The stamps could be exchanged for a selection of thousands of items at redemption stores. Implementation of the token economy was followed by large reductions in the number of days lost from work because of injuries, the number of lost-time injuries, and the costs of accidents and injuries. The reductions in costs far exceeded the costs of operating the token economy. All improvements were maintained over several years.

Accident Prevention↗