1
|
Havens A, El-Shaer E, Garcia L, Godino JL, Thompson RS. Protein Adsorption on Mixed Self-Assembled Monolayers: Influence of Chain Length and Terminal Group. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:16712-16720. [PMID: 37960859 DOI: 10.1021/acs.langmuir.3c01250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Mixed self-assembled monolayers (SAMs) are often used as highly tunable substrates for biomedical and biosensing applications. It is well documented, however, that mixed SAMs can be highly disordered at the molecular level and do not pack as closely or homogeneously as single-component SAMs, particularly when the chain lengths and head groups of the SAM thiol components are significantly different. In this study, we explore the impact of SAM structure and mixing ratio (-OH and -CH3 termini) on the weak physisorption behavior of bovine serum albumin (BSA), which adsorbs more readily to hydrophobic, methyl-terminated SAMs. Our results suggest that once the mixture includes 50% or more of the methyl terminus, the mixing ratio alone is a relatively good predictor of adsorption, regardless of the relative chain lengths of the thiols used in the mixture. This trend persists at any mixing ratio for SAMs where methyl- and hydroxyl-terminated groups are the same length or where the hydroxyl-terminated thiol is longer. The only variance observed is at low mixing ratios (<50% methyl-terminated) for a mixed SAM where the methyl-terminated component has a longer chain length. Relative protein adsorption increases on these mixtures, perhaps due to the disordered exposure of the excess alkane backbone. Taken together, however, we do not find significant evidence that varying chain lengths for mixed SAMs prepared on polycrystalline substrates and analyzed in air have an outsized influence on nanoscopic adsorption behavior, despite molecular-level disorder in the SAM itself.
Collapse
Affiliation(s)
- Alyssa Havens
- Department of Chemistry, St. Edward's University, 3000 S. Congress Avenue, Austin, Texas 78704, United States
| | - Emily El-Shaer
- Department of Chemistry, St. Edward's University, 3000 S. Congress Avenue, Austin, Texas 78704, United States
| | - Liliana Garcia
- Department of Chemistry, St. Edward's University, 3000 S. Congress Avenue, Austin, Texas 78704, United States
| | - John Luke Godino
- Department of Chemistry, St. Edward's University, 3000 S. Congress Avenue, Austin, Texas 78704, United States
| | - Rebecca S Thompson
- Department of Chemistry, St. Edward's University, 3000 S. Congress Avenue, Austin, Texas 78704, United States
| |
Collapse
|
2
|
Yu T, Marquez MD, Lee TR. SAMs on Gold Derived from Adsorbates Having Phenyl and Cyclohexyl Tail Groups Mixed with Their Phase-Incompatible Fluorinated Analogues. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:13488-13496. [PMID: 36287137 DOI: 10.1021/acs.langmuir.2c01991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
This article investigates two types of mixed self-assembled monolayers (SAMs) derived from adsorbates having cyclohexyl and phenyl tail groups mixed with their perfluorinated analogues. The mixed SAMs were characterized using ellipsometry, X-ray photoelectron spectroscopy (XPS), polarization-modulation infrared reflection absorption spectroscopy, and contact angle measurements. The XPS results show preferential adsorption of the nonfluorinated adsorbate in the perfluorocyclohexyl-terminated/cyclohexyl-terminated pair due to the steric bulk of the tail groups. On the other hand, mixed surfaces with a precisely controlled surface composition were achieved with the phenyl-terminated/perfluorophenyl-terminated mixed SAMs, exhibiting a linear relationship between the mole fraction on the surface and the mole fraction in solution. The results suggest that the relative solubility, steric bulk of the tail group moiety, and the interaction between two different adsorbates are the key factors driving the phase phenomena observed in the SAMs. More importantly, this study suggests that the interfacial properties can be controlled with a minimal loss of packing densities with the phenyl-terminated/perfluorophenyl-terminated mixed SAMs.
Collapse
Affiliation(s)
- Tianlang Yu
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
- Department of Chemistry, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| | - Maria D Marquez
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
- Department of Chemistry, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| | - T Randall Lee
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
- Department of Chemistry, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| |
Collapse
|
3
|
St Hill LR, Craft JW, Chinwangso P, Tran HV, Marquez MD, Lee TR. Antifouling Coatings Generated from Unsymmetrical Partially Fluorinated Spiroalkanedithiols. ACS APPLIED BIO MATERIALS 2021; 4:1563-1572. [PMID: 35006665 PMCID: PMC8812961 DOI: 10.1021/acsabm.0c01409] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
![]()
Biofouling
negatively impacts modern society on a daily basis,
especially with regard to the important industries of medicine, oil,
and shipping. This manuscript describes the preparation and study
of model antifouling coatings generated from the adsorption of unsymmetrical
partially fluorinated spiroalkanedithiols on gold. The antifouling
properties of the self-assembled monolayers (SAMs) derived from the
spiroalkanedithiols were compared to SAMs derived from analogous monodentate
partially fluorinated and nonfluorinated alkanethiols. The antifouling
properties were evaluated using in situ surface plasmon
resonance spectroscopy (SPR), ex situ electrochemical
quartz crystal microbalance (QCM) measurements, and ex situ ellipsometric thickness measurements. The resistance to nonspecific
protein adsorption of the SAMs was evaluated with proteins having
a wide range of properties and applications including protamine, lysozyme,
bovine serum albumin, and fibrinogen. The results from the SPR and
the QCM measurements demonstrated that in most cases, the SAM coatings
derived from the partially fluorinated spiroalkanedithiols having
mixed hydrocarbon and fluorocarbon tail groups exhibited better antifouling
performance when compared to the SAMs derived from their single-component
monodentate counterparts. The studies also revealed that while the
SPR and the QCM measurements in most cases were able to distinguish
the adsorption trends for the SAMs and proteins examined, the ellipsometric
thickness measurements were markedly less discriminating. On the whole,
these studies validate the use of unsymmetrical partially fluorinated
spiroalkanedithiols for generating effective antifouling coatings
on metal substrates.
Collapse
Affiliation(s)
- Lydia R St Hill
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| | - John W Craft
- Department of Biology and Biochemistry, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5001, United States
| | - Pawilai Chinwangso
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| | - Hung-Vu Tran
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| | - Maria D Marquez
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| | - T Randall Lee
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| |
Collapse
|
4
|
Cheung D. Effect of surface structure on peptide adsorption on soft surfaces. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2020.137929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
5
|
Sakunkaewkasem S, Gonzalez MA, Marquez MD, Lee TR. Olefin-Bridged Bidentate Adsorbates for Generating Self-Assembled Monolayers on Gold. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:10699-10707. [PMID: 32803985 DOI: 10.1021/acs.langmuir.0c01373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A series of custom-designed olefin-bridged bidentate adsorbates composed of an olefin group linking symmetrical hydrocarbon moieties of varying chain lengths was synthesized and used for the preparation of self-assembled monolayers (SAMs) on gold. The structures of the adsorbates are in the form Z-[CH3(CH2)m]2(C═C)[CH2SH]2 (OBCnSH) where m = 12-15 and n = m + 3 (OBC15SH, OBC16SH, OBC17SH, and OBC18SH). The influence of the olefin linker on the structural and interfacial properties of the SAMs was investigated and compared to SAMs formed from analogous n-alkanethiols. Characterization techniques included ellipsometry, X-ray photoelectron spectroscopy (XPS), polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS), and contact angle measurements. The OBCnSH SAMs exhibited ellipsometric thicknesses that were similar to their monodentate counterparts, suggesting that the new olefin-bridged adsorbates pack similarly to the monodentate analogs. Characterization by PM-IRRAS revealed that the OBCnSH SAMs were as conformationally ordered as those derived from the reference n-alkanethiols with the exception of the adsorbate with the shortest chain length OBC15SH, which exhibited low coverage and a liquid-like structure. Unlike the SAMs derived from the n-alkanethiols, the OBCnSH SAMs failed to exhibit "odd-even" effects. However, the OBCnSH SAMs displayed similar hexadecane contact angles as their n-alkanethiol counterparts with the exception of OBC15SH, which exhibited markedly diminished hexadecane contact angles. The similar structural and interfacial properties of the OBCnSH SAMs, when compared to analogous n-alkanethiol SAMs, render the molecular architecture of the olefin-bridged dithiol as a robust platform for the synthesis of adsorbates with two chemically distinct tailgroups for use in the preparation and study of phase-incompatible "conflicted" interfaces.
Collapse
Affiliation(s)
- Siwakorn Sakunkaewkasem
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| | - Mario A Gonzalez
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| | - Maria D Marquez
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| | - T Randall Lee
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States
| |
Collapse
|
6
|
Ortiz de la Morena R, Asyuda A, Lu H, Aitchison H, Turner K, Francis SM, Zharnikov M, Buck M. Shape controlled assembly of carboxylic acids: formation of a binary monolayer by intercalation into molecular nanotunnels. Phys Chem Chem Phys 2020; 22:4205-4215. [PMID: 32043099 DOI: 10.1039/c9cp06724h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Binary self-assembled monolayers (SAMs) combining a Y-shaped aromatic carboxylic acid (1,3,5-benzenetribenzoic acid, H3BTB) and a cage-type alicyclic carboxylic acid (adamantane carboxylic acid, AdCA) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The SAMs, prepared by molecular adsorption from solution on Au substrates modified by underpotential deposition of Ag, exhibit a pronounced dependence of their structure on the assembly protocol. Exposing an H3BTB SAM to AdCA, the highly regular row structure of the native H3BTB layer persists and STM imaging does not show signs of AdCA adsorption. This is in striking contrast to the disordered arrangements of H3BTB and the presence of AdCA employing the inverted adsorption sequence or coadsorption of the two molecules. However, spectroscopic analysis of the H3BTB SAM exposed to AdCA reveals the presence also of the latter, suggesting that the AdCA molecules are hidden in the nanotunnels of the H3BTB monolayer. Direct evidence for the intercalation of AdCA is obtained by STM manipulation experiments which lay bare areas of AdCA molecules upon local removal of H3BTB. Surprisingly, these are densely packed and arranged into a highly ordered monolayer. Formation of such a compact AdCA layer is explained by expulsion of AdCA from the H3BTB nanotunnels of the surrounding intact mixed SAM, driven by release of stress in the nanotunnels built up when AdCA is intercalated.
Collapse
Affiliation(s)
| | - Andika Asyuda
- Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
| | - Hao Lu
- Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
| | - Hannah Aitchison
- EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK.
| | - Kelly Turner
- EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK.
| | - Stephen M Francis
- EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK.
| | - Michael Zharnikov
- Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
| | - Manfred Buck
- EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK.
| |
Collapse
|
7
|
Chinwangso P, St Hill LR, Marquez MD, Lee TR. Unsymmetrical Spiroalkanedithiols Having Mixed Fluorinated and Alkyl Tailgroups of Varying Length: Film Structure and Interfacial Properties. Molecules 2018; 23:E2632. [PMID: 30322175 PMCID: PMC6222720 DOI: 10.3390/molecules23102632] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 09/19/2018] [Accepted: 09/25/2018] [Indexed: 02/01/2023] Open
Abstract
A custom-designed series of unsymmetrical spiroalkanedithiols having tailgroups comprised of a terminally fluorinated chain and a hydrocarbon chain of varying lengths were synthesized and used to prepare self-assembled monolayers (SAMs) on gold substrates. The specific structure of the adsorbates was of the form [CH₃(CH₂)n][CF₃(CF₂)₇(CH₂)₈]C[CH₂SH]₂, where n = 7, 9, and 15 (designated as F8H10-C10, F8H10-C12, and F8H10-C18, respectively). The influence of the length of the hydrocarbon chain in the bidentate dithiol on the structure and interfacial properties of the monolayer was explored. A structurally analogous partially fluorinated monodentate alkanethiol and the corresponding normal alkanethiols were used to generate appropriate SAMs as reference systems. Measurements of ellipsometric thickness showed an unexpectedly low film thickness for the SAMs derived from the bidentate adsorbates, possibly due to disruptions in interchain packing caused by the fluorocarbon chains (i.e., phase-incompatible fluorocarbon-hydrocarbon interactions), ultimately giving rise to loosely packed and disordered films. Analysis by X-ray photoelectron spectroscopy (XPS) were also consistent with a model in which the films were loosely packed; additionally, the XPS spectra confirmed the attachment of the sulfur headgroups of the bidentate adsorbates onto the gold substrates. Studies of the SAMs by polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS) suggested that as the length of the hydrocarbon chain in the adsorbates was extended, a more ordered surface was achieved by reducing the tilt of the fluorocarbon segment. The wettability data indicated that the adsorbates with longer alkyl chains were less wettable than those with shorter alkyl chains, likely due to an increase in interchain van der Waals forces in the former.
Collapse
Affiliation(s)
- Pawilai Chinwangso
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, TX 77204-5003, USA.
| | - Lydia R St Hill
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, TX 77204-5003, USA.
| | - Maria D Marquez
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, TX 77204-5003, USA.
| | - T Randall Lee
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, TX 77204-5003, USA.
| |
Collapse
|