/pdf/self-assembled-monolayers-of-thiolates-on-metals-as-a-form-1neb0hj3k4.pdf

Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

This paper describes a procedure that makes it possible to design and fabricate (including sealing) microfluidic systems in an elastomeric materialpoly(dimethylsiloxane) (PDMS)in less than 24 h. A network of microfluidic channels (with width >20 μm) is designed in a CAD program. This design is converted into a transparency by a high-resolution printer; this transparency is used as a mask in photolithography to create a master in positive relief photoresist. PDMS cast against the master yields a polymeric replica containing a network of channels. The surface of this replica, and that of a flat slab of PDMS, are oxidized in an oxygen plasma. These oxidized surfaces seal tightly and irreversibly when brought into conformal contact. Oxidized PDMS also seals irreversibly to other materials used in microfluidic systems, such as glass, silicon, silicon oxide, and oxidized polystyrene; a number of substrates for devices are, therefore, practical options. Oxidation of the PDMS has the additional advantage that it ...

Rapid prototyping of microfluidic systems in poly(dimethylsiloxane)

In recent years, numerous large-scale seawater desalination plants have been built in water-stressed countries to augment available water resources, and construction of new desalination plants is expected to increase in the near future. Despite major advancements in desalination technologies, seawater desalination is still more energy intensive compared to conventional technologies for the treatment of fresh water. There are also concerns about the potential environmental impacts of large-scale seawater desalination plants. Here, we review the possible reductions in energy demand by state-of-the-art seawater desalination technologies, the potential role of advanced materials and innovative technologies in improving performance, and the sustainability of desalination as a technological solution to global water shortages.

http://science.sciencemag.org/content/sci/333/6043/712.full.pdf

The Future of Seawater Desalination: Energy, Technology, and the Environment

5.1. Detection Formats 475 5.2. Food Quality and Safety Analysis 477 5.2.1. Pathogens 477 5.2.2. Toxins 479 5.2.3. Veterinary Drugs 479 5.2.4. Vitamins 480 5.2.5. Hormones 480 5.2.6. Diagnostic Antibodies 480 5.2.7. Allergens 481 5.2.8. Proteins 481 5.2.9. Chemical Contaminants 481 5.3. Medical Diagnostics 481 5.3.1. Cancer Markers 481 5.3.2. Antibodies against Viral Pathogens 482 5.3.3. Drugs and Drug-Induced Antibodies 483 5.3.4. Hormones 483 5.3.5. Allergy Markers 483 5.3.6. Heart Attack Markers 484 5.3.7. Other Molecular Biomarkers 484 5.4. Environmental Monitoring 484 5.4.1. Pesticides 484 5.4.2. 2,4,6-Trinitrotoluene (TNT) 485 5.4.3. Aromatic Hydrocarbons 485 5.4.4. Heavy Metals 485 5.4.5. Phenols 485 5.4.6. Polychlorinated Biphenyls 487 5.4.7. Dioxins 487 5.5. Summary 488 6. Conclusions 489 7. Abbreviations 489 8. Acknowledgment 489 9. References 489

Surface Plasmon Resonance Sensors for Detection of Chemical and Biological Species

Hydrophilic polymers are the center of research emphasis in nanotechnology because of their perceived “intelligence”. They can be used as thin films, scaffolds, or nanoparticles in a wide range of biomedical and biological applications. Here we highlight recent developments in engineering uncrosslinked and crosslinked hydrophilic polymers for these applications. Natural, biohybrid, and synthetic hydrophilic polymers and hydrogels are analyzed and their thermodynamic responses are discussed. In addition, examples of the use of hydrogels for various therapeutic applications are given. We show how such systems’ intelligent behavior can be used in sensors, microarrays, and imaging. Finally, we outline challenges for the future in integrating hydrogels into biomedical applications.

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Hydrogels in Biology and Medicine: From Molecular Principles to Bionanotechnology†

This paper describes the use of surface plasmon resonance (SPR) spectroscopy and self-assembled monolayers (SAMs) to determine the characteristics of functional groups that give surfaces the ability to resist the nonspecific adsorption of proteins from solution. Mixed SAMs presenting different functional groups were prepared for screening using a synthetic protocol based on the reaction of organic amines with a SAM terminated by interchain carboxylic anhydride groups. Surfaces that presented derivatives of oligo(sarcosine), N-acetylpiperazine, and permethylated sorbitol groups were particularly effective in resisting the adsorption of proteins. Incorporation of these groups into single-component SAMs resulted in surfaces that are comparable to (but slightly less good than) single-component SAMs that present oligo(ethylene glycol) in their ability to resist the adsorption of proteins. In the group of surfaces examined, those that resisted the adsorption of proteins had the following properties:  they were ...

A Survey of Structure−Property Relationships of Surfaces that Resist the Adsorption of Protein

This paper describes the use of surface plasmon resonance spectroscopy and self-assembled monolayers (SAMs) of alkanethiols on gold to evaluate the ability of surfaces terminating in different combinations of charged groups to resist the nonspecific adsorption of proteins from aqueous buffer. Mixed SAMs formed from a 1:1 combination of a thiol terminated in a trimethylammonium group and a thiol terminated in a sulfonate group adsorbed less than 1% of a monolayer of two proteins with different characteristics:  fibrinogen and lysozyme. Single-component SAMs formed from thiols terminating in groups combining a positively charged moiety and a negatively charged moiety were also capable of resisting the adsorption of proteins. Single-component SAMs presenting single charges adsorbed nearly a full monolayer of protein. The amount of protein that adsorbed to mixed zwitterionic SAMs did not depend on the ionic strength or the pH of the buffer in which the protein was dissolved. The amount of protein that adsorbe...

Zwitterionic SAMs that Resist Nonspecific Adsorption of Protein from Aqueous Buffer

This paper examines the hypothesis that surfaces resistant to protein adsorption should also be resistant to the adhesion of bacteria (Staphylococcus aureus, Staphylococcus epidermidis) and the attachment and spreading of mammalian cells (bovine capillary endothelial (BCE) cells). The surfaces tested were those of self-assembled monolayers (SAMs) terminated with derivatives of tri(sarcosine) (Sarc), N-acetylpiperazine, permethylated sorbitol, hexamethylphosphoramide, phosphoryl choline, and an intramolecular zwitterion (−CH2N+(CH3)2CH2CH2CH2SO3-) (ZW); all are known to resist the adsorption of proteins. There seems to be little or no correlation between the adsorption of protein (fibrinogen and lysozyme) and the adhesion of cells. Surfaces terminated with derivatives of Sarc and N-acetylpiperazine resisted the adhesion of S. aureus and S. epidermidis as well as did surfaces terminated with tri(ethylene glycol). A surface that presented Sarc groups was the only one that resisted the adhesion of BCE cells a...

Self-assembled monolayers that resist the adsorption of proteins and the adhesion of bacterial and mammalian cells

This contribution describes an experimentally straightforward procedure for preparing and screening surfaces for their ability to resist the adsorption of proteins from solution. For brevity, we call surfaces “protein resistant” when they are resistant to the adsorption of proteins from solution. We have used this procedure to identify several functional groups that had not previously been recognized as protein resistant. This work both identifies a number of functional groups that will be useful in designing resistance to the adsorption of biomolecules into devices used in sensing and in cell biology,1-3 and contributes to an understanding of the mechanism of action of protein resistant surfaces by correlating this property with molecular-scale structure.4-6 We combined self-assembled monolayers (SAMs)7,8 and surface plasmon resonance (SPR) spectroscopy9 into a system that enabled us to screen a number of functional groups rapidly for their ability to resist the adsorption of proteins. The surfaces were prepared by the “anhydride method” (Figure 1).10,11 This reaction generates a “mixed” SAM that comprises an ∼1:1 mixture of -CONRR′ and CO2H/CO2 groups.10,12 (We have not defined the state of the ionization of the CO2H groups in these SAMs.) The ease with which this class of mixed SAMs can be prepared by the anhydride method (relative to the synthesis of the functionalized alkanethiols HS(CH2)nR′ normally used for the preparation of singlecomponent SAMs) makes this route efficient for exploratory and screening work.11,13 We have examined the adsorption of two proteins to these surfaces: fibrinogen, a large (340 kD) blood plasma protein that adsorbs strongly to hydrophobic surfaces, and lysozyme, a small protein (14 kD, pI ) 12) that is positively charged under the conditions of our experiment (phosphate buffered saline, PBS, pH 7.4). Fibrinogen is used as a model for “sticky” serum proteins;11,14,15 lysozyme is often used in model studies of electrostatic adsorption of proteins to surfaces.16,17 Since lysozyme has a substantial net positive charge (Zp ) + 7.5 at pH 7.4, 100 mM KCl),18 it allowed us to examine attractive electrostatic interactions with CO2 groups on the surface. We have prepared more than 50 surfaces, each presenting a different functional group, using the anhydride procedure, and surveyed them for protein resistance.19 Table 1 summarizes selected results from this survey. The amount of protein adsorbed (∆RU ) change in response units) as measured by SPR was determined by subtracting the value of RU prior to the injection of protein from the value of RU measured 10 min after the completion of the protein injection; for clarity, these points are each labeled with a vertical dashed line in Figure 2. The value of ∆RU was used to calculate the percentage of a monolayer (%Monolayer) of that protein using eq 1.11,20 We define “%ML” according to eq 1 strictly to simplify the comparison between surfaces.

Surveying for Surfaces that Resist the Adsorption of Proteins

This paper describes the design and preparation of thin polymeric films that resist the adsorption of proteins and the adhesion of bacteria to an extent comparable to, or better than, self-assembled monolayers (SAMs) that present tri(ethylene glycol) groups. These polymeric films were prepared by the reaction of a polyamine, for example, poly(ethylenimine), with a SAM that presented interchain carboxylic anhydride groups, and by the subsequent conversion of the amino groups of the polymer to amido groups on reaction with acyl chlorides. Polyamines functionalized with acetyl chloride produced films that resisted the adsorption of protein and the adhesion of bacteria to a useful extent. Functionalization of the polyamine with acyl chlorides that were derivatives of oligo(ethylene glycol) resulted in films that were 1−10 times more resistant than those obtained by acetylation. The removal of hydrogen bond donor groups from the surface of the polyamines upon acylation seems to be important for the generation ...

Robert G. Chapman

Papers

A Survey of Structure−Property Relationships of Surfaces that Resist the Adsorption of Protein

Zwitterionic SAMs that Resist Nonspecific Adsorption of Protein from Aqueous Buffer

Self-assembled monolayers that resist the adsorption of proteins and the adhesion of bacterial and mammalian cells

Surveying for Surfaces that Resist the Adsorption of Proteins

Polymeric Thin Films That Resist the Adsorption of Proteins and the Adhesion of Bacteria