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Pan X, Ishaq MW, Ali MW, Yang J, Li L, Chen Y. Unraveling the conformational properties of comb-like Poly(propargyl acrylate)-graft-poly(2-ethyl-2-oxazoline) chains in dilute solutions. POLYMER 2021. [DOI: 10.1016/j.polymer.2021.124224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Pan X, Ishaq MW, Umair A, Ali MW, Li L. Evolution of Single Chain Conformation for Model Comb-Like Chains with Grafting Density Ranging from 0 to ∼100% in Dilute Solution. ACS Macro Lett 2019; 8:1535-1540. [PMID: 35619382 DOI: 10.1021/acsmacrolett.9b00711] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
This work aims to experimentally clarify how the single chain conformation evolves as a function of grafting density for model comb-like chains in dilute solution in the whole density regime. Via a combination of rational design, precise synthesis and accurate characterization, we obtained four sets of PPANb-g-PS30-σ comb-like samples with well-defined architectures and accurately extracted their molecular parameters by triple detection size exclusion chromatography (TD-SEC). With these samples in hand, we quantified how the excluded volume interaction and chain conformation evolve with the grafting density (σ) in the whole density regime. Three main findings are reported: (i) the graft-graft excluded volume interaction is not ignorable even in the low σ-regime; (ii) contrary to theoretical predictions, both the excluded volume interaction and the chain conformation are found to be Nb-dependent; (iii) both Rg ∼ σ1/3 and [η] ∼ σ0 are experimentally confirmed for comb-like chains from different σ and Nb, signifying a unique 3D mass-size growth pattern and a quasi-3D fractal feature. The obtained results help clarify some long-existed controversial issues in the field.
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Affiliation(s)
- Xuejun Pan
- Department of Chemical Physics, University of Science and Technology of China, Hefei, China 230026
| | - Muhammad Waqas Ishaq
- Department of Chemical Physics, University of Science and Technology of China, Hefei, China 230026
| | - Ahmad Umair
- Department of Chemical Physics, University of Science and Technology of China, Hefei, China 230026
| | - Muhammad Waqas Ali
- Institute for Advanced Study, Shenzhen University, Shenzhen, China 518060
| | - Lianwei Li
- Department of Chemical Physics, University of Science and Technology of China, Hefei, China 230026
- Food Science and Processing Research Center, Shenzhen University, Shenzhen, China 518060
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Mahalik JP, Sumpter BG, Kumar R. Vertical Phase Segregation Induced by Dipolar Interactions in Planar Polymer Brushes. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b01138] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Jyoti P. Mahalik
- Computer
Science and Mathematics
Division and Center for Nanophase Materials
Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Bobby G. Sumpter
- Computer
Science and Mathematics
Division and Center for Nanophase Materials
Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Rajeev Kumar
- Computer
Science and Mathematics
Division and Center for Nanophase Materials
Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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Wu X, Ryder MP, McGuire J, Snider JL, Schilke KF. Sequential and competitive adsorption of peptides at pendant PEO layers. Colloids Surf B Biointerfaces 2015; 130:69-76. [PMID: 25909181 DOI: 10.1016/j.colsurfb.2015.04.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 04/05/2015] [Accepted: 04/06/2015] [Indexed: 11/24/2022]
Abstract
Earlier work provided direction for development of responsive drug delivery systems based on modulation of the structure, amphiphilicity, and surface density of bioactive peptides entrapped within pendant polyethylene oxide (PEO) brush layers. In this work, we describe the sequential and competitive adsorption behavior of such peptides at pendant PEO layers. Three cationic peptides were used for this purpose: the arginine-rich, amphiphilic peptide WLBU2, a peptide chemically identical to WLBU2 but of scrambled sequence (S-WLBU2), and the non-amphiphilic peptide poly-L-arginine (PLR). Optical waveguide lightmode spectroscopy (OWLS) was used to quantify the rate and extent of peptide adsorption and elution at surfaces coated with PEO. UV spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to quantify the extent of peptide exchange during the course of sequential and competitive adsorption. Circular dichroism (CD) was used to evaluate conformational changes after adsorption of peptide mixtures at PEO-coated silica nanoparticles. Results indicated that amphiphilic peptides are able to displace adsorbed, non-amphiphilic peptides in PEO layers, while non-amphiphilic peptides were not able to displace more amphiphilic peptides. In addition, peptides of greater amphiphilicity dominated the adsorption at the PEO layer from mixtures with less amphiphilic or non-amphiphilic peptides.
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Affiliation(s)
| | - Matthew P Ryder
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, USA
| | - Joseph McGuire
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, USA
| | | | - Karl F Schilke
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, USA.
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McGuire J. Building a working understanding of protein adsorption with model systems and serendipity. Colloids Surf B Biointerfaces 2014; 124:38-48. [DOI: 10.1016/j.colsurfb.2014.08.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 08/19/2014] [Accepted: 08/20/2014] [Indexed: 10/24/2022]
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Wu X, Ryder MP, McGuire J, Schilke KF. Concentration effects on peptide elution from pendant PEO layers. Colloids Surf B Biointerfaces 2014; 118:210-7. [PMID: 24780434 DOI: 10.1016/j.colsurfb.2014.03.056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Revised: 03/28/2014] [Accepted: 03/30/2014] [Indexed: 11/29/2022]
Abstract
In earlier work, we have provided direction for development of responsive drug delivery systems based on modulation of structure and amphiphilicity of bioactive peptides entrapped within pendant polyethylene oxide (PEO) brush layers. Amphiphilicity promotes retention of the peptides within the hydrophobic inner region of the PEO brush layer. In this work, we describe the effects of peptide surface density on the conformational changes caused by peptide-peptide interactions, and show that this phenomenon substantially affects the rate and extent of peptide elution from PEO brush layers. Three cationic peptides were used in this study: the arginine-rich amphiphilic peptide WLBU2, the chemically identical but scrambled peptide S-WLBU2, and the non-amphiphilic homopolymer poly-l-arginine (PLR). Circular dichroism (CD) was used to evaluate surface density effects on the structure of these peptides at uncoated (hydrophobic) and PEO-coated silica nanoparticles. UV spectroscopy and a quartz crystal microbalance with dissipation monitoring (QCM-D) were used to quantify changes in the extent of peptide elution caused by those conformational changes. For amphiphilic peptides at sufficiently high surface density, peptide-peptide interactions result in conformational changes which compromise their resistance to elution. In contrast, elution of a non-amphiphilic peptide is substantially independent of its surface density, presumably due to the absence of peptide-peptide interactions. The results presented here provide a strategy to control the rate and extent of release of bioactive peptides from PEO layers, based on modulation of their amphiphilicity and surface density.
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Affiliation(s)
- Xiangming Wu
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, USA
| | - Matthew P Ryder
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, USA
| | - Joseph McGuire
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, USA
| | - Karl F Schilke
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, USA.
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Ryder MP, Wu X, McKelvey GR, McGuire J, Schilke KF. Binding interactions of bacterial lipopolysaccharide and the cationic amphiphilic peptides polymyxin B and WLBU2. Colloids Surf B Biointerfaces 2014; 120:81-7. [PMID: 24905681 DOI: 10.1016/j.colsurfb.2014.05.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Revised: 05/01/2014] [Accepted: 05/02/2014] [Indexed: 11/26/2022]
Abstract
Passage of blood through a sorbent device for removal of bacteria and endotoxin by specific binding with immobilized, membrane-active, bactericidal peptides holds promise for treating severe blood infections. Peptide insertion in the target membrane and rapid/strong binding is desirable, while membrane disruption and release of degradation products to the circulating blood is not. Here we describe interactions between bacterial endotoxin (lipopolysaccharide, LPS) and the membrane-active, bactericidal peptides WLBU2 and polymyxin B (PmB). Analysis of the interfacial behavior of mixtures of LPS and peptide using air-water interfacial tensiometry and optical waveguide lightmode spectroscopy strongly suggests insertion of intact LPS vesicles by the peptide WLBU2 without vesicle destabilization. In contrast, dynamic light scattering (DLS) studies show that LPS vesicles appear to undergo peptide-induced destabilization in the presence of PmB. Circular dichroism spectra further confirm that WLBU2, which shows disordered structure in aqueous solution and substantially helical structure in membrane-mimetic environments, is stably located within the LPS membrane in peptide-vesicle mixtures. We therefore expect that presentation of WLBU2 at an interface, if tethered in a fashion which preserves its mobility and solvent accessibility, will enable the capture of bacteria and endotoxin without promoting reintroduction of endotoxin to the circulating blood, thus minimizing adverse clinical outcomes. On the other hand, our results suggest no such favorable outcome of LPS interactions with polymyxin B.
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Affiliation(s)
- Matthew P Ryder
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, United States
| | - Xiangming Wu
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, United States
| | - Greg R McKelvey
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, United States
| | - Joseph McGuire
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, United States
| | - Karl F Schilke
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, United States.
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Auxier JA, Dill JK, Schilke KF, McGuire J. Blood protein repulsion after peptide entrapment in pendant polyethylene oxide layers. Biotechnol Appl Biochem 2014; 61:371-5. [DOI: 10.1002/bab.1201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 12/22/2013] [Indexed: 11/07/2022]
Affiliation(s)
- Julie A. Auxier
- School of Chemical, Biological and Environmental Engineering; Oregon State University; Corvallis OR USA
| | - Justen K. Dill
- School of Chemical, Biological and Environmental Engineering; Oregon State University; Corvallis OR USA
| | - Karl F. Schilke
- School of Chemical, Biological and Environmental Engineering; Oregon State University; Corvallis OR USA
| | - Joseph McGuire
- School of Chemical, Biological and Environmental Engineering; Oregon State University; Corvallis OR USA
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Wu X, Ryder MP, McGuire J, Schilke KF. Adsorption, structural alteration and elution of peptides at pendant PEO layers. Colloids Surf B Biointerfaces 2013; 112:23-9. [PMID: 23939421 PMCID: PMC3818488 DOI: 10.1016/j.colsurfb.2013.07.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 07/12/2013] [Accepted: 07/15/2013] [Indexed: 10/26/2022]
Abstract
An experimentally based, quantitative understanding of the entrapment and function of small peptides within PEO brush layers does not currently exist. Earlier work provided a rationale for expecting that an ordered, compact peptide will enter the PEO phase more readily than a peptide of similar size that adopts a less ordered, less compact form, and that amphiphilicity will promote peptide retention within the hydrophobic region of the PEO brush. Here we more deliberately describe criteria for peptide integration and structural change within the PEO brush, and discuss the reversibility of peptide entrapment with changing solvent conditions. For this purpose, circular dichroism (CD) was used to record the adsorption and conformational changes of (amphiphilic) WLBU2 and (non-amphiphilic) polyarginine peptides at uncoated (hydrophobic) and PEO-coated silica nanoparticles. Peptide conformation was controlled between disordered and α-helical forms by varying the concentration of perchlorate ion. We show an initially more ordered (α-helical) structure promotes peptide adsorption into the PEO layer. Further, a partially helical peptide undergoes an increase in helicity after entry, likely due to concomitant loss of capacity for peptide-solvent hydrogen bonding. Peptide interaction with the PEO chains resulted in entrapment and conformational change that was irreversible to elution with changing solution conditions in the case of the amphiphilic peptide. In contrast, the adsorption and conformational change of the non-amphiphilic peptide was reversible. These results indicate that responsive drug delivery systems based on peptide-loaded PEO layers can be controlled by modulation of solution conditions and peptide amphiphilicity.
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Affiliation(s)
- Xiangming Wu
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331
| | - Matthew P. Ryder
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331
| | - Joseph McGuire
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331
| | - Karl F. Schilke
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331
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