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PAMAM versus PEI complexation for siRNA delivery: interaction with model lipid membranes and cellular uptake. Pharm Res 2022; 39:1151-1163. [PMID: 35318566 PMCID: PMC9197904 DOI: 10.1007/s11095-022-03229-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 03/08/2022] [Indexed: 11/06/2022]
Abstract
Purpose Cationic polymers have many advantages as vectors for mediated cellular entry and delivery of siRNA. However, toxicity related to their cationic charge has compromised clinical use. It is hypothesized that the siRNA-vector complex composition and properties can be controlled to optimize therapeutic performance. Here we investigate siRNA complexes with branched polyethylenimine (bPEI) versus generation 4 polyamidoamine dendrimers (PAMAM) on interactions with immobilized lipid membranes, and cellular uptake and toxicity. Methods A model siRNA was complexed with either PAMAM or bPEI, and their size and zeta-potential characterized. Interaction of the complexes and parent polymers with lipid bilayers was investigated using atomic force microscopy and correlated with the uptake and toxicity in HeLa cells. Results PAMAM and its siRNA complexes formed circular shaped micron-sized holes in lipid bilayers, while bPEI formed nanoscale holes. Flow cytometry and fluorescence microscopy demonstrated PAMAM-siRNA complexes to have a higher cellular uptake than bPEI-siRNA complexes. bPEI-siRNA complexes did not impact on viability, however PAMAM-siRNA complexes demonstrated increasing cell toxicity as N/P ratio increased. PAMAM-siRNA complexes accumulated around the cell nucleus, while PEI-siRNA complexes were located closer to the cell wall. Conclusion Complexation of PAMAM dendrimer or bPEI with siRNA modified physicochemical properties of the parent polymer, however it did not impact on the mechanism of interaction with model lipid bilayers or how the polymer/siRNA complex interacted and was internalized by HeLa cells. Interaction of siRNA polymer complexes with cells is related to the action of the parent polymer. Graphical abstract ![]()
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Cantini M, Gomide K, Moulisova V, González‐García C, Salmerón‐Sánchez M. Vitronectin as a Micromanager of Cell Response in Material-Driven Fibronectin Nanonetworks. ADVANCED BIOSYSTEMS 2017; 1:1700047. [PMID: 29497701 PMCID: PMC5822048 DOI: 10.1002/adbi.201700047] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 07/05/2017] [Indexed: 01/09/2023]
Abstract
Surface functionalization strategies of synthetic materials for regenerative medicine applications comprise the development of microenvironments that recapitulate the physical and biochemical cues of physiological extracellular matrices. In this context, material-driven fibronectin (FN) nanonetworks obtained from the adsorption of the protein on poly(ethyl acrylate) provide a robust system to control cell behavior, particularly to enhance differentiation. This study aims at augmenting the complexity of these fibrillar matrices by introducing vitronectin, a lower-molecular-weight multifunctional glycoprotein and main adhesive component of serum. A cooperative effect during co-adsorption of the proteins is observed, as the addition of vitronectin leads to increased fibronectin adsorption, improved fibril formation, and enhanced vitronectin exposure. The mobility of the protein at the material interface increases, and this, in turn, facilitates the reorganization of the adsorbed FN by cells. Furthermore, the interplay between interface mobility and engagement of vitronectin receptors controls the level of cell fusion and the degree of cell differentiation. Ultimately, this work reveals that substrate-induced protein interfaces resulting from the cooperative adsorption of fibronectin and vitronectin fine-tune cell behavior, as vitronectin micromanages the local properties of the microenvironment and consequently short-term cell response to the protein interface and higher order cellular functions such as differentiation.
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Affiliation(s)
- Marco Cantini
- Division of Biomedical EngineeringSchool of EngineeringUniversity of GlasgowOakfield AvenueG128LTGlasgowUK
| | - Karina Gomide
- Division of Biomedical EngineeringSchool of EngineeringUniversity of GlasgowOakfield AvenueG128LTGlasgowUK
| | - Vladimira Moulisova
- Division of Biomedical EngineeringSchool of EngineeringUniversity of GlasgowOakfield AvenueG128LTGlasgowUK
| | - Cristina González‐García
- Division of Biomedical EngineeringSchool of EngineeringUniversity of GlasgowOakfield AvenueG128LTGlasgowUK
| | - Manuel Salmerón‐Sánchez
- Division of Biomedical EngineeringSchool of EngineeringUniversity of GlasgowOakfield AvenueG128LTGlasgowUK
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Zhang H, Komasa S, Mashimo C, Sekino T, Okazaki J. Effect of ultraviolet treatment on bacterial attachment and osteogenic activity to alkali-treated titanium with nanonetwork structures. Int J Nanomedicine 2017; 12:4633-4646. [PMID: 28721040 PMCID: PMC5500560 DOI: 10.2147/ijn.s136273] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Purpose Alkali-treated titanium with nanonetwork structures (TNS) possesses good osteogenic activity; however, the resistance of this material to bacterial contamination remains inadequate. As such, TNS implants are prone to postoperative infection. In this work, we attempted to alter the biological properties of TNS by treatment with short-duration high-intensity ultraviolet (UV) irradiation. Methods TNS discs were treated with UV light (wavelength =254 nm, strength =100 mW/cm2) for 15 minutes using a UV-irradiation machine. We carried out a surface characterization and evaluated the discs for bacterial film formation, protein adsorption, and osteogenic features. Results The superhydrophilicity and surface hydrocarbon elimination exhibited by the treated material (UV-treated titanium with a nanonetwork structure [UV-TNS]) revealed that this treatment effectively changed the surface characteristics of TNS. Notably, UV-TNS also showed reduced colonization by Actinomyces oris during an initial attachment period and inhibition of biofilm formation for up to 6 hours. Moreover, compared to conventional TNS, UV-TNS showed superior osteogenic activity as indicated by increased levels of adhesion, proliferation, alkaline phosphatase activity, osteogenic factor production, and osteogenesis-related gene expression by rat bone marrow mesenchymal stem cells (rBMMSCs). This inverse relationship between bacterial attachment and cell adhesion could be due to the presence of electron–hole pairs induced by high-intensity UV treatment. Conclusion We suggest that simple UV treatment has great clinical potential for TNS implants, as it promotes the osseointegration of the TNS while reducing bacterial contamination, and can be conducted chair-side immediately prior to implantation.
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Affiliation(s)
- Honghao Zhang
- Department of Removable Prosthodontics and Occlusion, Osaka Dental University, Hirakata, Osaka, Japan.,Department of Stomatology, Nanfang Hospital and College of Stomatology, Southern Medical University, Guangzhou, Guangdong, China
| | - Satoshi Komasa
- Department of Removable Prosthodontics and Occlusion, Osaka Dental University, Hirakata, Osaka, Japan
| | - Chiho Mashimo
- Department of Bacteriology, Osaka Dental University, Hirakata
| | - Tohru Sekino
- The Institute of Scientific and Industrial Research, Osaka University, Suita, Osaka, Japan
| | - Joji Okazaki
- Department of Removable Prosthodontics and Occlusion, Osaka Dental University, Hirakata, Osaka, Japan
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Herranz-Diez C, Li Q, Lamprecht C, Mas-Moruno C, Neubauer S, Kessler H, Manero J, Guillem-Martí J, Selhuber-Unkel C. Bioactive compounds immobilized on Ti and TiNbHf: AFM-based investigations of biofunctionalization efficiency and cell adhesion. Colloids Surf B Biointerfaces 2015; 136:704-11. [DOI: 10.1016/j.colsurfb.2015.10.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 09/20/2015] [Accepted: 10/06/2015] [Indexed: 10/22/2022]
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Toromanov G, Gugutkov D, Gustavsson J, Planell J, Salmerón-Sánchez M, Altankov G. Dynamic Behavior of Vitronectin at the Cell–Material Interface. ACS Biomater Sci Eng 2015; 1:927-934. [DOI: 10.1021/acsbiomaterials.5b00147] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Georgi Toromanov
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
| | - Dencho Gugutkov
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
| | - Johan Gustavsson
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
| | - Josep Planell
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
- Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza 50018, Spain
| | - Manuel Salmerón-Sánchez
- School
of Engineering/Division of Biomedical Engineering, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - George Altankov
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain
- Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza 50018, Spain
- Institució Catalana de Recerca i Estudis Avancats (ICREA), Barcelona 08010, Spain
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Awang Shri DN, Tsuchiya K, Yamamoto A. Cytocompatibility evaluation and surface characterization of TiNi deformed by high-pressure torsion. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2014; 43:411-7. [DOI: 10.1016/j.msec.2014.07.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2013] [Revised: 05/17/2014] [Accepted: 07/02/2014] [Indexed: 11/26/2022]
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Lam ATL, Li J, Chen AKL, Reuveny S, Oh SKW, Birch WR. Cationic surface charge combined with either vitronectin or laminin dictates the evolution of human embryonic stem cells/microcarrier aggregates and cell growth in agitated cultures. Stem Cells Dev 2014; 23:1688-703. [PMID: 24641164 DOI: 10.1089/scd.2013.0645] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The expansion of human pluripotent stem cells (hPSC) for biomedical applications generally compels a defined, reliable, and scalable platform. Bioreactors offer a three-dimensional culture environment that relies on the implementation of microcarriers (MC), as supports for cell anchorage and their subsequent growth. Polystyrene microspheres/MC coated with adhesion-promoting extracellular matrix (ECM) protein, vitronectin (VN), or laminin (LN) have been shown to support hPSC expansion in a static environment. However, they are insufficient to promote human embryonic stem cells (hESC) seeding and their expansion in an agitated environment. The present study describes an innovative technology, consisting of a cationic charge that underlies the ECM coatings. By combining poly-L-lysine (PLL) with a coating of ECM protein, cell attachment efficiency and cell spreading are improved, thus enabling seeding under agitation in a serum-free medium. This coating combination also critically enables the subsequent formation and evolution of hPSC/MC aggregates, which ensure cell viability and generate high yields. Aggregate dimensions of at least 300 μm during early cell growth give rise to ≈15-fold expansion at 7 days' culture. Increasing aggregate numbers at a quasi-constant size of ≈300 μm indicates hESC growth within a self-regulating microenvironment. PLL+LN enables cell seeding and aggregate evolution under constant agitation, whereas PLL+VN requires an intermediate 2-day static pause to attain comparable aggregate sizes and correspondingly high expansion yields. The cells' highly reproducible bioresponse to these defined and characterized MC surface properties is universal across multiple cell lines, thus confirming the robustness of this scalable expansion process in a defined environment.
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Affiliation(s)
- Alan Tin-Lun Lam
- 1 Stem Cell Group, Bioprocessing Technology Institute , Agency for Science, Technology and Research (A*STAR), Singapore , Singapore
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Xing H, Komasa S, Taguchi Y, Sekino T, Okazaki J. Osteogenic activity of titanium surfaces with nanonetwork structures. Int J Nanomedicine 2014; 9:1741-55. [PMID: 24741311 PMCID: PMC3983010 DOI: 10.2147/ijn.s58502] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Background Titanium surfaces play an important role in affecting osseointegration of dental implants. Previous studies have shown that the titania nanotube promotes osseointegration by enhancing osteogenic differentiation. Only relatively recently have the effects of titanium surfaces with other nanostructures on osteogenic differentiation been investigated. Methods In this study, we used NaOH solutions with concentrations of 2.5, 5.0, 7.5, 10.0, and 12.5 M to develop a simple and useful titanium surface modification that introduces the nanonetwork structures with titania nanosheet (TNS) nanofeatures to the surface of titanium disks. The effects of such a modified nanonetwork structure, with different alkaline concentrations on the osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMMSCs), were evaluated. Results The nanonetwork structures with TNS nanofeatures induced by alkali etching markedly enhanced BMMSC functions of cell adhesion and osteogenesis-related gene expression, and other cell behaviors such as proliferation, alkaline phosphatase activity, extracellular matrix deposition, and mineralization were also significantly increased. These effects were most pronounced when the concentration of NaOH was 10.0 M. Conclusion The results suggest that nanonetwork structures with TNS nanofeatures improved BMMSC proliferation and induced BMMSC osteogenic differentiation. In addition, the surfaces formed with 10.0 M NaOH suggest the potential to improve the clinical performance of dental implants.
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Affiliation(s)
- Helin Xing
- Department of Prosthetic Dentistry, School of Stomatology, The Fourth Military Medical University, Xi'an, People's Republic of China ; Graduate School of Dentistry (Removable Prosthodontics and Occlusion), Osaka Dental University, Hirakata, Osaka, Japan
| | - Satoshi Komasa
- Department of Removable Prosthodontics and Occlusion, Osaka Dental University, Hirakata, Osaka, Japan
| | - Yoichiro Taguchi
- Department of Periodontology, Osaka Dental University, Hirakata, Osaka, Japan
| | - Tohru Sekino
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Aoba-ku, Sendai, Japan
| | - Joji Okazaki
- Department of Removable Prosthodontics and Occlusion, Osaka Dental University, Hirakata, Osaka, Japan
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Macromolecule–semiconductor interfaces: From enzyme immobilization to photoelectrocatalytical applications. J Electroanal Chem (Lausanne) 2011. [DOI: 10.1016/j.jelechem.2011.05.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Yap LYW, Li J, Phang IY, Ong LT, Ow JZE, Goh JCH, Nurcombe V, Hobley J, Choo ABH, Oh SKW, Cool SM, Birch WR. Defining a threshold surface density of vitronectin for the stable expansion of human embryonic stem cells. Tissue Eng Part C Methods 2010; 17:193-207. [PMID: 20726687 DOI: 10.1089/ten.tec.2010.0328] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Current methodology for pluripotent human embryonic stem cells (hESCs) expansion relies on murine sarcoma basement membrane substrates (Matrigel™), which precludes the use of these cells in regenerative medicine. To realize the clinical efficacy of hESCs and their derivatives, expansion of these cells in a defined system that is free of animal components is required. This study reports the successful propagation of hESCs (HES-3 and H1) for > 20 passages on tissue culture-treated polystyrene plates, coated from 5 μg/mL of human plasma-purified vitronectin (VN) solution. Cells maintain expression of pluripotent markers Tra1-60 and OCT-4 and are karyotypically normal after 20 passages of continuous culture. In vitro and in vivo differentiation of hESC by embryoid body formation and teratoma yielded cells from the ecto-, endo-, and mesoderm lineages. VN immobilized on tissue culture polystyrene was characterized using a combination of X-ray photoemission spectroscopy, atomic force microscopy, and quantification of the VN surface density with a Bradford protein assay. Ponceau S staining was used to measure VN adsorption and desorption kinetics. Tuning the VN surface density, via the concentration of depositing solution, revealed a threshold surface density of 250 ng/cm², which is required for hESCs attachment, proliferation, and differentiation. Cell attachment and proliferation assays on VN surface densities above this threshold show the substrate properties to be equally viable.
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Affiliation(s)
- Lynn Y W Yap
- Stem Cells and Tissue Repair Group, Institute of Medical Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
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Toromanov G, González-García C, Altankov G, Salmerón-Sánchez M. Vitronectin activity on polymer substrates with controlled –OH density. POLYMER 2010. [DOI: 10.1016/j.polymer.2010.03.041] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Sogo Y, Ito A, Onoguchi M, Li X, Oyane A, Ichinose N. Formation of cytochrome C–apatite composite layer on NaOH- and heat-treated titanium. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2009. [DOI: 10.1016/j.msec.2008.07.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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13
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Bernards MT, Jiang S. pH-induced conformation changes of adsorbed vitronectin maximize its bovine aortic endothelial cell binding ability. J Biomed Mater Res A 2008; 87:505-14. [DOI: 10.1002/jbm.a.31778] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Knöner G, Rolfe BE, Campbell JH, Parkin SJ, Heckenberg NR, Rubinsztein-Dunlop H. Mechanics of cellular adhesion to artificial artery templates. Biophys J 2006; 91:3085-96. [PMID: 16861267 PMCID: PMC1578459 DOI: 10.1529/biophysj.105.076125] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We are using polymer templates to grow artificial artery grafts in vivo for the replacement of diseased blood vessels. We have previously shown that adhesion of macrophages to the template starts the graft formation. We present a study of the mechanics of macrophage adhesion to these templates on a single cell and single bond level with optical tweezers. For whole cells, in vitro cell adhesion densities decreased significantly from polymer templates polyethylene to silicone to Tygon (167, 135, and 65 cells/mm(2)). These cell densities were correlated with the graft formation success rate (50%, 25%, and 0%). Single-bond rupture forces at a loading rate of 450 pN/s were quantified by adhesion of trapped 2-microm spheres to macrophages. Rupture force distributions were dominated by nonspecific adhesion (forces <40 pN). On polystyrene, preadsorption of fibronectin or presence of serum proteins in the cell medium significantly enhanced adhesion strength from a mean rupture force of 20 pN to 28 pN or 33 pN, respectively. The enhancement of adhesion by fibronectin and serum is additive (mean rupture force of 43 pN). The fraction of specific binding forces in the presence of serum was similar for polystyrene and polymethyl-methacrylate, but specific binding forces were not observed for silica. Again, we found correlation to in vivo experiments, where the density of adherent cells is higher on polystyrene than on silica templates, and can be further enhanced by fibronectin adsorption. These findings show that in vitro adhesion testing can be used for template optimization and to substitute for in-vivo experiments.
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Affiliation(s)
- Gregor Knöner
- Centre for Biophotonics and Laser Science, and Centre for Research in Vascular Biology, The University of Queensland, Brisbane, Australia
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Miller DC, Haberstroh KM, Webster TJ. Mechanism(s) of increased vascular cell adhesion on nanostructured poly(lactic-co-glycolic acid) films. J Biomed Mater Res A 2005; 73:476-84. [PMID: 15880725 DOI: 10.1002/jbm.a.30318] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Studies have shown that poly(lactic-co-glycolic acid) (PLGA) films with nanometer surface features promote vascular endothelial and smooth muscle cell adhesion. The objective of this in vitro research was to begin to understand the mechanisms behind this observed increase in vascular cell adhesion. Results provided evidence that nanostructured PLGA adsorbed significantly more vitronectin and fibronectin from serum compared to conventional (or those not possessing nanometer surface features) PLGA. When separately preadsorbing both vitronectin and fibronectin, increased vascular smooth muscle and endothelial cell density was observed on nanostructured (compared to conventional) PLGA. Additionally, blocking of cell-binding epitopes of fibronectin and vitronectin significantly decreased vascular cell adhesion on nanostructured (compared to conventional) PLGA. For this reason, results of the present in vitro study demonstrated that cell adhesive proteins adsorbed in different quantities and altered bioactivity on nanostructured compared to conventional PLGA topographies, which (at least in part) may account for the documented increased vascular cell adhesion on nanostructured PLGA. In this manner, this study continues to provide evidence for the promise of nanostructured PLGA in vascular tissue engineering applications.
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Affiliation(s)
- Derick C Miller
- Weldon School of Biomedical Engineering, Purdue University, 500 Central Drive, West Lafayette, IN 47907-2022, USA
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Bhushan B, Tokachichu DR, Keener MT, Lee SC. Morphology and adhesion of biomolecules on silicon based surfaces. Acta Biomater 2005; 1:327-41. [PMID: 16701811 DOI: 10.1016/j.actbio.2005.01.002] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Revised: 01/25/2005] [Accepted: 01/26/2005] [Indexed: 11/28/2022]
Abstract
Biomolecules such as proteins, on silicon based surfaces are of extreme importance in various applications including microfabricated silicon implants, in the fabrication of microdevices with protein compounds (e.g., biosensors), and therapeutics. Morphology of silicon based surfaces with and without biomolecules and their adhesion with the substrate govern performance and reliability of the biological application. In this research, step by step morphological changes of silicon as well as adhesion during its surface modification have been studied using atomic force microscopy. To improve adhesion between biomolecules and the silicon based surfaces, chemical conjugation as well as surface patterning have been used. Changes in adhesion as a result of surface modification have been analyzed with the help of contact angle measurements. Phase imaging technique was used to confirm the presence of biomolecules on the surface. To understand the relationship between morphology and local values of adhesion, adhesion mapping and local stiffness mapping were carried out.
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Affiliation(s)
- Bharat Bhushan
- Nanotribology Laboratory for Information storage and MEMS/NEMS, The Ohio State University, 650 Ackerman Road, Suite 255, Columbus, OH 43202, USA.
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Zhang H, Bremmell KE, Smart RSC. Direct measurement of interactions between adsorbed vitronectin layers: The influence of ionic strength and pH. J Biomed Mater Res A 2005; 74:59-68. [PMID: 15909285 DOI: 10.1002/jbm.a.30364] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Vitronectin (Vn) is an adhesive protein in the plasma serum and plays an important role in cell attachment, spreading, and proliferation. The interactions between protein bovine vitronectin layers adsorbed onto a silica probe and a mica surface have been investigated with the use of atomic force microscopy (AFM). Adsorption of vitronectin was confirmed by XPS surface analysis. The force-separation curves and pull-off forces were measured as a function of ionic strength and solution pH. The pull-off force (adhesion force) decreased as the salt concentration increased, which suggests that some binding domains of this protein may associate with the ionic species and reduce its binding ability. Discrete jumps, or discontinuities, in the separation force curve were observed to extend to a maximum of 300 nm, evidence that the protein molecules bridge between the surfaces. As a function of pH, the adhesion force on separation of the protein-coated surfaces showed a maximum at pH 5 (i.e.p. of vitronectin), decreasing in magnitude at lower and higher pH values. At pH 5, the approaching curves illustrated a jump-in force; whereas for pH values away from 5, the approaching force curves were repulsive. Correlation of the interaction forces with Vn conformational changes in different pH environments, directly visualized with the use of AFM imaging, was developed. In its i.e.p. region, the Vn molecular conformation appeared to be dense and compact. Significantly, at wounds/injured sites the pH is low (approximately 5) which this study discovered to facilitate adsorption and formation of vitronectin aggregates, known to trigger their subsequent biological functions.
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Affiliation(s)
- Hailong Zhang
- Ian Wark Research Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia
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