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Attachment of endothelial colony-forming cells onto a surface bearing immobilized anti-CD34 antibodies: Specific CD34 binding versus nonspecific binding. Biointerphases 2022; 17:031003. [PMID: 35589426 DOI: 10.1116/6.0001746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Cardiovascular disease is a leading cause of death worldwide; however, despite substantial advances in medical device surface modifications, no synthetic coatings have so far matched the native endothelium as the optimal hemocompatible surface for blood-contacting implants. A promising strategy for rapid restoration of the endothelium on blood-contacting biomedical devices entails attracting circulating endothelial cells or their progenitors, via immobilized cell-capture molecules; for example, anti-CD34 antibody to attract CD34+ endothelial colony-forming cells (ECFCs). Inherent is the assumption that the cells attracted to the biomaterial surface are bound exclusively via a specific CD34 binding. However, serum proteins might adsorb in-between or on the top of antibody molecules and attract ECFCs via other binding mechanisms. Here, we studied whether a surface with immobilized anti-CD34 antibodies attracts ECFCs via a specific CD34 binding or a nonspecific (non-CD34) binding. To minimize serum protein adsorption, a fouling-resistant layer of hyperbranched polyglycerol (HPG) was used as a "blank slate," onto which anti-CD34 antibodies were immobilized via aldehyde-amine coupling reaction after oxidation of terminal diols to aldehydes. An isotype antibody, mIgG1, was surface-immobilized analogously and was used as the control for antigen-binding specificity. Cell binding was also measured on the HPG hydrogel layer before and after oxidation. The surface analysis methods, x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, were used to verify the intended surface chemistries and revealed that the surface coverage of antibodies was sparse, yet the anti-CD34 antibody grafted surface-bound ECFCs very effectively. Moreover, it still captured the ECFCs after BSA passivation. However, cells also attached to oxidized HPG and immobilized mIgG1, though in much lower amounts. While our results confirm the effectiveness of attracting ECFCs via surface-bound anti-CD34 antibodies, our observation of a nonspecific binding component highlights the importance of considering its consequences in future studies.
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Plasma polymerization of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl in a collisional, capacitively coupled radio frequency discharge. Biointerphases 2020; 15:061007. [PMID: 33218222 DOI: 10.1116/6.0000662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Plasma polymerization of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) yields thin films containing stable nitroxide radicals that have properties analogous to that of nitric oxide (NO) without short lifetimes. This property gives TEMPO films a wide variety of potential applications. Typically, control of the final film chemistry is difficult and the plasma discharge conditions must be tailored to in order to maximize the retention of these nitroxide groups during the polymerization and deposition process. In this study, plasma diagnostics and surface analysis of the deposited films were carried out to determine the optimal plasma conditions for the retention of nitroxide groups. These techniques included energy-resolved mass spectrometry, heated planar probe ion current measurements, deposition rate measurements, and x-ray photoelectron spectroscopy (XPS). Results show that operating the plasma with a combination of low input powers and high pressures produces a collisional discharge in which fragmentation of the TEMPO molecule is suppressed, leading to good retention of nitroxide groups. Ion energy distribution functions and quartz crystal microbalance measurements support the soft landing theory of ion deposition on the substrate within this γ-mode, in which the flux of low energy, soft landed ions form the primary contribution to film growth. XPS analysis of deposited polymers shows 75.7% retention of N-O groups in the polymer films deposited in a 25 Pa 5 W discharge.
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Wang H, Evans D, Voelcker NH, Griesser HJ, Meagher L. Modulation of substrate van der Waals forces using varying thicknesses of polymer overlayers. J Colloid Interface Sci 2020; 580:690-699. [PMID: 32712475 DOI: 10.1016/j.jcis.2020.07.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/02/2020] [Accepted: 07/07/2020] [Indexed: 11/18/2022]
Abstract
Thin polymeric coatings are commonly used for altering surface properties and modulating the interfacial performance of materials. Possible contributions from the substrate to the interfacial forces and effects are, however, usually ignored and are not well understood, nor is it established how the coating thickness modulates and eventually eliminates contributions from substrates to the van der Waals (vdW) interfacial force. In this study we quantified, by colloid-probe atomic force microscope (AFM) and by theoretical calculations, the interfacial vdW contributions from substrates acting through ethanol plasma polymer (EtOHpp) coatings of a range of thicknesses on Au and Si bulk materials. In approach force curves against EtOHpp-coated Au substrates the magnitude of the vdW force decreased as the EtOHpp coating thickness increased to 18 nm and then plateaued with further increases in coating thickness, providing direct evidence for a contribution to the total interfacial vdW force from the Au substrate acting through thin coatings. The experimental observations accord with theoretical calculations of the thickness dependence of Hamaker coefficients derived from rigorous simulation using the Lifshitz theory. In addition, the measured forces agree well with theoretical predictions including correction for finite roughness. Thus, our experimental and theoretical results establish how the thickness of polymer thin film coatings modulates the total interfacial vdW force and how this can be used to tune the net vdW force so as to either contain a large substrate contribution or arise predominantly from the polymeric overlayer. Our findings enable rational design of coating thickness to tailor interfacial interactions and material performance.
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Affiliation(s)
- Hongfang Wang
- Future Industries Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
| | - Drew Evans
- Future Industries Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia
| | - Nicolas H Voelcker
- Future Industries Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia; Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800, Australia; Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Hans J Griesser
- Future Industries Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
| | - Laurence Meagher
- Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800, Australia
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Hennekam BE, Al‐Bataineh SA, Michelmore A. Fabrication and characterization of biorenewable plasma polymer films using sandalwood oil precursor. J Appl Polym Sci 2020. [DOI: 10.1002/app.49288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Brent E. Hennekam
- School of Natural Built EnvironmentsUniversity of South Australia Mawson Lakes South Australia Australia
| | - Sameer A. Al‐Bataineh
- Future Industries InstituteUniversity of South Australia Mawson Lakes South Australia Australia
| | - Andrew Michelmore
- Future Industries InstituteUniversity of South Australia Mawson Lakes South Australia Australia
- School of EngineeringUniversity of South Australia Mawson Lakes South Australia Australia
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To be a radical or not to be one? The fate of the stable nitroxide radical TEMPO [(2,2,6,6-Tetramethylpiperidin-1-yl)oxyl] undergoing plasma polymerization into thin-film coatings. Biointerphases 2020; 15:031015. [PMID: 32590900 DOI: 10.1116/6.0000259] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The stable nitroxide radical TEMPO [(2,2,6,6-Tetramethylpiperidin-1-yl)oxyl] has a multitude of applications in fields ranging from energy storage to biomedical applications and many more. However, to date, the processes of incorporating nitroxide radicals into thin-film coatings are laborious and not cost-effective, which hinders their wider use in many applications. In contrast, the authors have recently demonstrated the facile method of plasma polymerization of TEMPO into thin-film coatings that retain the stable nitroxide radicals. In this work, we are using three types of mass spectroscopic methods (plasma-mass spectrometry, time of flight secondary ion mass spectrometry, and high-performance liquid chromatography-mass spectrometry) and electron spin resonance to track the fate of the TEMPO molecule from monomer flask through the plasma and inside the resulting coatings. The results of this study demonstrate that TEMPO is a versatile monomer that can be used across different plasma reactors and reliably retain the stable nitroxide radical in the resulting thin-film coatings if certain process conditions are observed, namely, higher process pressures and lower powers.
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Burzava ALS, Jasieniak M, Cockshell MP, Voelcker NH, Bonder CS, Griesser HJ, Moore E. Surface-Grafted Hyperbranched Polyglycerol Coating: Varying Extents of Fouling Resistance across a Range of Proteins and Cells. ACS APPLIED BIO MATERIALS 2020; 3:3718-3730. [DOI: 10.1021/acsabm.0c00336] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Anouck L. S. Burzava
- Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia
| | - Marek Jasieniak
- Cooperative Research Centre for Cell Therapy Manufacturing, Adelaide, SA 5000, Australia
| | - Michaelia P. Cockshell
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, SA 5000, Australia
| | - Nicolas H. Voelcker
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
- Commonwealth Scientific and Industrial Research Organisation (CSIRO), Clayton, VIC 3168, Australia
| | - Claudine S. Bonder
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, SA 5000, Australia
- Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA 5000, Australia
| | - Hans J. Griesser
- Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia
| | - Eli Moore
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, SA 5000, Australia
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Saboohi S, Short RD, Coad BR, Griesser HJ, Michelmore A. The Physics of Plasma Ion Chemistry: A Case Study of Plasma Polymerization of Ethyl Acetate. J Phys Chem Lett 2019; 10:7306-7310. [PMID: 31710230 DOI: 10.1021/acs.jpclett.9b02855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Deposition chemistry from plasma is highly dependent on both the chemistry of the ions arriving at surfaces and the ion energy. Typically, when measuring the energy distribution of ions arriving at surfaces from plasma, it is assumed that the distributions are the same for all ionic species. Using ethyl acetate as a representative organic precursor molecule, we have measured the ion chemistry and ion energy as a function of pressure and power. We show that at low pressure (<2 Pa) this assumption is valid; however, at elevated pressures ion-molecule collisions close to the deposition surface affect both the energy and chemistry of these ions. Smaller ions are formed close to the surface and have lower energy than larger ionic species which are formed in the bulk of the plasma. The changes in plasma chemistry therefore are closely linked to the physics of the plasma-surface interface.
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Affiliation(s)
- Solmaz Saboohi
- Future Industries Institute , University of South Australia , Mawson Lakes Campus, Mawson Lakes , Australia , 5095
| | - Robert D Short
- Materials Science Institute and Department of Chemistry , University of Lancaster , City of Lancaster LA1 4YW , U.K
| | - Bryan R Coad
- School of Agriculture, Food and Wine , University of Adelaide , Adelaide , SA 5005 , Australia
| | - Hans J Griesser
- Future Industries Institute , University of South Australia , Mawson Lakes Campus, Mawson Lakes , Australia , 5095
| | - Andrew Michelmore
- Future Industries Institute , University of South Australia , Mawson Lakes Campus, Mawson Lakes , Australia , 5095
- School of Engineering , University of South Australia , Mawson Lakes Campus, Mawson Lakes , Australia , 5095
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Wang H, Evans D, Voelcker NH, Griesser HJ, Meagher L. Interfacial Forces at Layered Surfaces: Substrate Electrical Double-Layer Forces Acting through Ultrathin Polymer Coatings. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:11679-11689. [PMID: 31407904 DOI: 10.1021/acs.langmuir.9b02176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Manipulating the surface properties of materials via the application of coatings is a widely used strategy to achieve desired interfacial interactions, implicitly assuming that the interfacial forces of coated samples are determined exclusively by the surface properties of the coatings. However, interfacial interactions between materials and their environments operate over finite length scales. Thus, the question addressed in this study is whether interactions associated with bulk substrate materials could act through thin coatings or, conversely, how thick a coating needs to be to completely screen subsurface forces contributed by underlying substrates. Plasma polymer layers were deposited on silicon wafer substrates from ethanol vapor, with identical chemical composition, ultrasmooth surfaces, and varying thicknesses. Using colloid-probe atomic force microscopy, electrical double-layer forces were determined in solutions of various ionic strengths and fitted using the Derjaguin-Landau-Verwey-Overbeek theory. For the thicker ethanol plasma polymers, the fitted surface potentials reflected the presence of surface carboxylate groups and were invariant with thickness. In contrast, for coatings <18 nm thick, the surface potentials increased steadily with decreasing film thickness; the measured electrical double-layer forces contained contributions from both the coating and the substrate. Theoretical calculations were in agreement with this model. Thus, our observations indicate that the higher surface potential of the underlying SiO2 surface can influence the interactions between a colloid particle and the multilayer structure if coatings are sufficiently thin. Such superposition needs to be factored into the design of coatings aimed at the control of material interactions via surface forces.
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Affiliation(s)
- Hongfang Wang
- Future Industries Institute , University of South Australia , Mawson Lakes , South Australia 5095 , Australia
| | - Drew Evans
- Future Industries Institute , University of South Australia , Mawson Lakes , South Australia 5095 , Australia
| | - Nicolas H Voelcker
- Future Industries Institute , University of South Australia , Mawson Lakes , South Australia 5095 , Australia
- Department of Materials Science and Engineering , Monash University , Clayton , Victoria 3800 , Australia
- Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade , Parkville , Victoria 3052 , Australia
| | - Hans J Griesser
- Future Industries Institute , University of South Australia , Mawson Lakes , South Australia 5095 , Australia
| | - Laurence Meagher
- Department of Materials Science and Engineering , Monash University , Clayton , Victoria 3800 , Australia
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Macgregor M, Williams R, Downes J, Bachhuka A, Vasilev K. The Role of Controlled Surface Topography and Chemistry on Mouse Embryonic Stem Cell Attachment, Growth and Self-Renewal. MATERIALS (BASEL, SWITZERLAND) 2017; 10:E1081. [PMID: 28906470 PMCID: PMC5615735 DOI: 10.3390/ma10091081] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/12/2017] [Accepted: 09/12/2017] [Indexed: 12/17/2022]
Abstract
The success of stem cell therapies relies heavily on our ability to control their fate in vitro during expansion to ensure an appropriate supply. The biophysical properties of the cell culture environment have been recognised as a potent stimuli influencing cellular behaviour. In this work we used advanced plasma-based techniques to generate model culture substrates with controlled nanotopographical features of 16 nm, 38 nm and 68 nm in magnitude, and three differently tailored surface chemical functionalities. The effect of these two surface properties on the adhesion, spreading, and self-renewal of mouse embryonic stem cells (mESCs) were assessed. The results demonstrated that physical and chemical cues influenced the behaviour of these stem cells in in vitro culture in different ways. The size of the nanotopographical features impacted on the cell adhesion, spreading and proliferation, while the chemistry influenced the cell self-renewal and differentiation.
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Affiliation(s)
- Melanie Macgregor
- School of Engineering, Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
| | - Rachel Williams
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool L7 8TX, UK.
| | - Joni Downes
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool L7 8TX, UK.
| | - Akash Bachhuka
- Institute for Photonics and Advanced Sensing, University of Adelaide, Adelaide, SA 5000, Australia.
| | - Krasimir Vasilev
- School of Engineering, Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
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Saboohi S, Coad BR, Griesser HJ, Michelmore A, Short RD. Synthesis of highly functionalised plasma polymer films from protonated precursor ions via the plasma α–γ transition. Phys Chem Chem Phys 2017; 19:5637-5646. [DOI: 10.1039/c6cp08630f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Functional group retention in plasma polymers is maximised by tuning the pressure/power to the α to γ transition.
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Affiliation(s)
- Solmaz Saboohi
- Future Industries Institute
- University of South Australia
- Mawson Lakes
- Australia
| | - Bryan R. Coad
- Future Industries Institute
- University of South Australia
- Mawson Lakes
- Australia
- School of Agriculture
| | - Hans J. Griesser
- Future Industries Institute
- University of South Australia
- Mawson Lakes
- Australia
| | - Andrew Michelmore
- Future Industries Institute
- University of South Australia
- Mawson Lakes
- Australia
- School of Engineering
| | - Robert D. Short
- Future Industries Institute
- University of South Australia
- Mawson Lakes
- Australia
- Materials Science Institute and Department of Chemistry
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12
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Saboohi S, Coad BR, Michelmore A, Short RD, Griesser HJ. Hyperthermal Intact Molecular Ions Play Key Role in Retention of ATRP Surface Initiation Capability of Plasma Polymer Films from Ethyl α-Bromoisobutyrate. ACS APPLIED MATERIALS & INTERFACES 2016; 8:16493-16502. [PMID: 27304927 DOI: 10.1021/acsami.6b04477] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report a systematic study of the plasma polymerization of ethyl α-bromoisobutyrate (EBIB) to produce thin film coatings capable of serving as ATRP initiation surfaces, for which they must contain α-bromoisobutyryl functional groups. In the deposition of polymeric coatings by plasma polymerization there generally occurs considerable fragmentation of precursor ("monomer") molecules in the plasma; and the retention of larger structural elements is challenging, particularly when they are inherently chemically labile. Empirical principles such as low plasma power and low pressure are usually utilized. However, we show that the α-bromoisobutyryl structural moiety is labile in a plasma gas phase and in low pressure plasma conditions, below the collisional threshold, there is little retention. At higher pressure, in contrast, fragmentation of this structural motif appears to be reduced substantially, and coatings useful for ATRP initiation were obtained. Mass spectrometry analysis of the composition of the plasma phase revealed that the desired structural moiety can be retained through the plasma, if the plasma conditions are steered toward ions of the precursor molecule. Whereas at low pressure the plasma polymer assembles mainly from various neutral (radical) fragments, at higher pressure the deposition occurs from hyperthermal ions, among which the protonated intact molecular ion is the most abundant. At higher pressure, a substantial population of ions has low kinetic energy, leading to "soft landing" and thus less fragmentation. This study demonstrates that relatively complex structural motifs in precursor molecules can be retained in plasma polymerization if the chemical and physical processes occurring in the plasma phase are elucidated and controlled such that desirable larger structural elements play a key role in the film deposition.
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Affiliation(s)
- Solmaz Saboohi
- Future Industries Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia
| | - Bryan R Coad
- Future Industries Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia
| | - Andrew Michelmore
- School of Engineering, University of South Australia , Mawson Lakes, South Australia 5095, Australia
| | - Robert D Short
- Future Industries Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia
| | - Hans J Griesser
- Future Industries Institute, University of South Australia , Mawson Lakes, South Australia 5095, Australia
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