Atomic Force Microscopy and X-ray Reflectivity Studies of Albumin Adsorbed onto Self-Assembled Monolayers of Hexadecyltrichlorosilane

Sheller, Nina; Petrash, Stanislaw; Foster, Mark D.; Tsukruk, Vladimir V.

doi:10.1021/la970916s

Cited by 120 publications

(148 citation statements)

References 35 publications

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“…Films prepared with TESP generally had more aggregates present on the surface compared to the OTMS films. Water contact angle measurements of the OTMS and TESP films ( Table 2) are consistent with SAMs prepared from octadecyltrichlorosilane and a 4 -6mer oligoethylene glycol grafted silane, respectively (19,22,26). …”

Section: Sam Preparation and Characterizationsupporting

confidence: 67%

“…The concentration of BSA is similar to the concentration of proteins in cell culture sera (~6 mg/mL), which in turn is near physiological protein concentrations (~40 mg/mL). Protein adhesion studies found in the literature (23,24,26,27,29) have typically used concentrations between 1.0 -0.01 mg/mL, which is the concentration range where the protein-surface adsorption isotherm rise is steepest. By employing concentrations at which the adsorption isotherm has the steepest slope, the effect of surface passivation is more distinct.…”

Section: Bsa Adsorption On Sam Coated Siliconmentioning

confidence: 99%

“…Polyethylene glycol (PEG), or polyethyleneoxide (PEO), functionalized surfaces are examples of hydrophilic coatings that offer excellent resistance to protein and cellular adhesion as both grafted polymer and SAM films (19,20,21,22,23,24). In contrast, hydrophobic surfaces, such as octadecyltrichlorosilane SAMs, tend to adsorb proteins as a monolayer thick biofilm (25,26,27). The current understanding of the difference in protein adhesion is related to the interfacial free energy of the coating in water (surface hydrophobicity), steric repulsion of the functionalized surface against protein (entropy losses in chain conformation and solvent expulsion), and conformational changes allowed by the adsorbing protein (28,29,30).…”

Section: Introductionmentioning

confidence: 99%

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Protein Adhesion on SAM Coated Semiconductor Wafers: Hydrophobic versus Hydrophilic Surfaces

Follstaedt¹,

Cheung²,

Gourley³

et al. 2000

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The interface of biology and semiconductor materials has become an important topic of interest as researchers are merging living organisms with microelectromechanical systems (MEMS) in the pursuit of new microfabricated biomedical devices. Biological cells interface with the semiconductor surface through a host of interactions that are mediated by protein adhesion and film formation. To better understand this interface, we have conducted protein adsorption studies of a model system using bovine serum albumin (BSA) and compared it to the adsorption from a complex protein mixture of cell growth serum on uncoated and self-assembled monolayer (SAM) coated silicon wafers. Several characterization techniques -AFM, ellipsometry, water contact angle, and fluorescence microscopy -were used to evaluate the protein-adsorbed layer. An uncoated silicon surface was most attractive to proteins, forming a 70 Å thick film from a solution of BSA at a concentration comparable to that in cell growth serum. Coating with the hydrophobic octadecyltrimethoxysilane (OTMS) SAM reduced protein adhesion by ~15%. In contrast, a hydrophilic N-(triethoxysilylpropyl)-O-polyethyleneoxide urethane (TESP) SAM inhibited protein adhesion by greater than 50%. Protein adhesion studies with cell growth sera containing complex mixtures of proteins paralleled the BSA adsorption studies, clearly identifying the TESP coated surface as a promising biocompatible coating.4

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Section: Sam Preparation and Characterizationsupporting

confidence: 67%

Section: Bsa Adsorption On Sam Coated Siliconmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Protein Adhesion on SAM Coated Semiconductor Wafers: Hydrophobic versus Hydrophilic Surfaces

Follstaedt¹,

Cheung²,

Gourley³

et al. 2000

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“…From the XRR evaluation and CAH, discussed in the next section, layers formed from 15 to 45 min were very difficult to distinguish. Previous XRR studies of silane showed thickness of 2.1 +/ 0.3 nm with a densities ranging from 0.76 -0.87 g/cm 2 for complete monolayer formation [145], [146], consistent with what we observe. Higher densities were shown to correspond to incomplete SAM formations [146].…”

Section: Sam Formationsupporting

confidence: 92%

“…Previous XRR studies of silane showed thickness of 2.1 +/ 0.3 nm with a densities ranging from 0.76 -0.87 g/cm 2 for complete monolayer formation [145], [146], consistent with what we observe. Higher densities were shown to correspond to incomplete SAM formations [146]. Additionally, the AFM scan of the anodized tantalum oxide substrate showed a RMS roughness of 0.612 nm, the same as found from the XRR measurement.…”

Section: Sam Formationsupporting

confidence: 92%

Low Voltage Electrowetting-on-Dielectric for Microfluidic Systems

Mibus¹

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Manipulating fluids in micro to nano-liter volumes poses significant challenges, due to the dominance of surface forces with increasingly large surface to volume ratios. Commonly, external pumps or precisely micromachined on-chip pumps were used to generate pressure gradients to induce fluid motion. Alternatively, the wettability of a surface can be manipulated by an applied electric field. This phenomenon, known as electrowetting, consists in the spread of a liquid drop placed on an electrode upon application of a voltage. Electrowetting based devices flourished upon the discovery that an added dielectric layer between the drop and a conductive electrode would tolerate the application of large voltages, allowing for significant contact angle change. Several current commercial devices exploiting this effect include electro-optic displays, electronic paper, and variable focus lenses.Additionally, electrowetting has achieved particular prominence in lab-on-a-chip applications, controlling drop transport across patterned electrode structures.Initially, polymers were utilized as the dielectric layer preventing current flow between the fluid and electrode, while providing a hydrophobic surface to minimize the resistance of drop movement.However, these layers were typically in excess of one micron thickness. As a consequence, these layers required over 100 Volts to achieve appreciable contact angle change. This dissertation aims to reduce the voltage dependence for contact angle change by optimization of a dual layer structure utilizing a dielectric and hydrophobic layer. The dielectric layer uses aluminum and tantalum oxides (15-44 nm thick) formed by electrochemical anodization. The electronic and ionic conduction, breakdown characteristics, and dielectric properties of these films were studied in detail, achieving a comprehensive understanding of the charge transport and failure mechanisms. Three hydrophobic layer were investigated: a commercial fluoropolymer Cytop, and two self-assembled monolayers 3

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Preparation, morphological characterization, and activity of thin films of horseradish peroxidase

Vianello

Zennaro

Paolo

et al. 2000

Biotechnol. Bioeng.

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Active uniform films of horseradish peroxidase (HRP) have been prepared by covalent binding on Si/SiO2 or glass supports previously activated by silanization and succinylation. Labeling by fluorescent or by Electron Spin Resonance (ESR) probes was used to quantify the surface density of active groups and of horseradish peroxidase. Atomic Force Microscopy (AFM) imaging was used to characterize the surface morphology. We observed that a non‐uniform protein adsorption due to physical interactions was present when the supports were not activated for covalent binding and was, in large part, removed by washing. The enzyme deposited by covalent binding formed homogeneous layers with a height in the range 60–90 Å. By using a fluorescent label, we calculated a protein density of 3.6 × 1012 molecules cm−2 on Si/SiO2, corresponding to an estimated area per molecule of 2800 Å2 which is in agreement with the value expected on the basis of the crystallographic data considering the formation of a monomolecular layer. The protein density of the layer immobilized on glass was similar (1.9 ×1012 molecules cm−2). The enzyme immobilized on both supports showed a kcat/KM being of the order of 3–5×105 M−1s−1 that is 1/20th of free HRP. The half‐life time of the activity of the enzyme immobilized by covalent binding was longer than 40 days at 6°C. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 68: 488–495, 2000.

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Atomic Force Microscopy and X-ray Reflectivity Studies of Albumin Adsorbed onto Self-Assembled Monolayers of Hexadecyltrichlorosilane

Cited by 120 publications

References 35 publications

Protein Adhesion on SAM Coated Semiconductor Wafers: Hydrophobic versus Hydrophilic Surfaces

Protein Adhesion on SAM Coated Semiconductor Wafers: Hydrophobic versus Hydrophilic Surfaces

Low Voltage Electrowetting-on-Dielectric for Microfluidic Systems

Preparation, morphological characterization, and activity of thin films of horseradish peroxidase

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