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Li J, Bi L, Musolino SF, Wulff JE, Sask KN. Functionalization of Polydimethylsiloxane with Diazirine-Based Linkers for Covalent Protein Immobilization. ACS APPLIED MATERIALS & INTERFACES 2024; 16:1-16. [PMID: 38149968 DOI: 10.1021/acsami.3c08013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2023]
Abstract
Biomolecule attachment to solid supports is critical for biomedical devices, such as biosensors and implants. Polydimethylsiloxane (PDMS) is commonly used for these applications due to its advantageous properties. To enhance the biomolecule immobilization on PDMS, a novel technique is demonstrated using newly synthesized diazirine molecules for the surface modification of PDMS. This nondestructive process involves a reaction between diazirine molecules and PDMS through C-H insertion with thermal or ultraviolet activation. The success of the PDMS modification is confirmed by various surface characterization techniques. Bovine serum albumin (BSA) and immunoglobulin G (IgG) are strongly attached to the modified PDMS surfaces, and the amount of protein is quantified using iodine-125 radiolabeling. The results demonstrate that PDMS is rapidly functionalized, and the stability of the immobilized proteins is significantly improved with multiple types of diazirine molecules and activation methods. Confocal microscopy provides three-dimensional images of the distribution of immobilized IgG on the surfaces and the penetration of diazirine-based linkers through the PDMS substrate during the coating process. Overall, this study presents a promising new approach for functionalizing PDMS surfaces to enhance biomolecule immobilization, and its potential applications can extend to multimaterial modifications for various diagnostic and medical applications such as microfluidic devices and immunoassays with relevant bioactive proteins.
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Affiliation(s)
- Jie Li
- School of Biomedical Engineering, McMaster University, Hamilton, Ontario L8S 4L2, Canada
| | - Liting Bi
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
| | - Stefania F Musolino
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
| | - Jeremy E Wulff
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
| | - Kyla N Sask
- School of Biomedical Engineering, McMaster University, Hamilton, Ontario L8S 4L2, Canada
- Department of Materials Science & Engineering, McMaster University, Hamilton, Ontario L8S 4L8, Canada
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Baumann HJ, Betonio P, Abeywickrama CS, Shriver LP, Leipzig ND. Metabolomic and Signaling Programs Induced by Immobilized versus Soluble IFN γ in Neural Stem Cells. Bioconjug Chem 2020; 31:2125-2135. [PMID: 32820900 DOI: 10.1021/acs.bioconjchem.0c00338] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Neural stem cells (NSCs) provide a strategy to replace damaged neurons following traumatic central nervous system injuries. A major hurdle to translation of this therapy is that direct application of NSCs to CNS injury does not support sufficient neurogenesis due to lack of proper cues. To provide prolonged spatial cues to NSCs IFN-γ was immobilized to biomimetic hydrogel substrate to supply physical and biochemical signals to instruct the encapsulated NSCs to be neurogenic. However, the immobilization of factors, including IFN-γ, versus soluble delivery of the same factor, has been incompletely characterized especially with respect to activation of signaling and metabolism in cells over longer time points. In this study, protein and metabolite changes in NSCs induced by immobilized versus soluble IFN-γ at 7 days were evaluated. Soluble IFN-γ, refreshed daily over 7 days, elicited stronger responses in NSCs compared to immobilized IFN-γ, indicating that immobilization may not sustain signaling or has altered ligand/receptor interaction and integrity. However, both IFN-γ delivery types supported increased βIII tubulin expression in parallel with canonical and noncanonical receptor-signaling compared to no IFN-γ. Global metabolomics and pathway analysis revealed that soluble and immobilized IFN-γ altered metabolic pathway activities including energy, lipid, and amino acid synthesis, with soluble IFN-γ having the greatest metabolic impact overall. Finally, soluble and immobilized IFN-γ support mitochondrial voltage-dependent anion channel (VDAC) expression that correlates to differentiated NSCs. This work utilizes new methods to evaluate cell responses to protein delivery and provides insight into mode of action that can be harnessed to improve regenerative medicine-based strategies.
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Affiliation(s)
- Hannah J Baumann
- Department of Chemistry, The University of Akron, Akron, Ohio 44325, United States
| | - Patricia Betonio
- School of Nursing, The University of Akron, Akron, Ohio 44325, United States
| | | | - Leah P Shriver
- Department of Chemistry, The University of Akron, Akron, Ohio 44325, United States
| | - Nic D Leipzig
- Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325, United States
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Christie SM, Ham TR, Gilmore GT, Toth PD, Leipzig ND, Smith AW. Covalently Immobilizing Interferon-γ Drives Filopodia Production through Specific Receptor-Ligand Interactions Independently of Canonical Downstream Signaling. Bioconjug Chem 2020; 31:1362-1369. [PMID: 32329609 PMCID: PMC10243121 DOI: 10.1021/acs.bioconjchem.0c00105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Immobilizing a signaling protein to guide cell behavior has been employed in a wide variety of studies. This approach draws inspiration from biology, where specific, affinity-based interactions between membrane receptors and immobilized proteins in the extracellular matrix guide many developmental and homeostatic processes. Synthetic immobilization approaches, however, do not necessarily recapitulate the in vivo signaling system and potentially lead to artificial receptor-ligand interactions. To investigate the effects of one example of engineered receptor-ligand interactions, we focus on the immobilization of interferon-γ (IFN-γ), which has been used to drive differentiation of neural stem cells (NSCs). To isolate the effect of ligand immobilization, we transfected Cos-7 cells with only interferon-γ receptor 1 (IFNγR1), not IFNγR2, so that the cells could bind IFN-γ but were incapable of canonical signal transduction. We then exposed the cells to surfaces containing covalently immobilized IFN-γ and studied membrane morphology, receptor-ligand dynamics, and receptor activation. We found that exposing cells to immobilized but not soluble IFN-γ drove the formation of filopodia in both NSCs and Cos-7, showing that covalently immobilizing IFN-γ is enough to affect cell behavior, independently of canonical downstream signaling. Overall, this work suggests that synthetic growth factor immobilization can influence cell morphology beyond enhancing canonical cell responses through the prolonged signaling duration or spatial patterning enabled by protein immobilization. This suggests that differentiation of NSCs could be driven by canonical and non-canonical pathways when IFN-γ is covalently immobilized. This finding has broad implications for bioengineering approaches to guide cell behavior, as one ligand has the potential to impact multiple pathways even when cells lack the canonical signal transduction machinery.
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Affiliation(s)
- Shaun M. Christie
- Department of Chemistry, The University of Akron, 190 Buchtel Common, Akron, Ohio, 44325, United States
| | - Trevor R. Ham
- Department of Biomedical Engineering, The University of Akron, Auburn Science and Engineering Center #275, West Tower, Akron, OH 44325, United States
| | - Grant T. Gilmore
- Department of Chemistry, The University of Akron, 190 Buchtel Common, Akron, Ohio, 44325, United States
| | - Paul D. Toth
- Department of Chemistry, The University of Akron, 190 Buchtel Common, Akron, Ohio, 44325, United States
| | - Nic D. Leipzig
- Department of Biomedical Engineering, The University of Akron, Auburn Science and Engineering Center #275, West Tower, Akron, OH 44325, United States
- Department of Chemical, Biomolecular, and Corrosion Engineering, The University of Akron, 302 Buchtel Common, Akron, Ohio, 44325, United States
| | - Adam W. Smith
- Department of Chemistry, The University of Akron, 190 Buchtel Common, Akron, Ohio, 44325, United States
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Subcutaneous priming of protein-functionalized chitosan scaffolds improves function following spinal cord injury. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2020; 110:110656. [PMID: 32076364 DOI: 10.1016/j.msec.2020.110656] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 12/24/2019] [Accepted: 01/07/2020] [Indexed: 12/19/2022]
Abstract
Strategies using neural stem cells (NSCs) to aid regeneration following spinal cord injury (SCI) show much promise, but challenges remain regarding implementation and efficacy. In this work, we explored the use of an NSC-seeded scaffold consisting of covalently immobilized interferon-γ and rat NSCs within a hydrogel matrix (methacrylamide chitosan). We placed the scaffolds within the subcutaneous environment of rats, allowing them to incubate for 4 weeks in order to prime them for regeneration prior to being transplanted into a right lateral hemisection SCI model in the same animal. We found that subcutaneous priming reduced the lineage commitment of encapsulated NSCs, as observed by increased nestin expression and decreased NeuN expression. When combined with intracellular σ peptide administration (which reduces inhibition from the glial scar), subcutaneous maturation improved functional outcomes, which were assessed by BBB score and quantitative gait parameters (fore and hind limb duty factor imbalance, right and left paw placement accuracy). Although we did not observe any direct reconnection of the transplanted cells with the host tissue, we did observe neurofilament fibers extending from the host tissue into the scaffold. Importantly, the mechanism for improved functional outcomes is likely an increase in trophic support from subcutaneously maturing the scaffold, which is enhanced by the administration of ISP.
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Kim SM, Ueki M, Ren X, Akimoto J, Sakai Y, Ito Y. Micropatterned nanolayers immobilized with nerve growth factor for neurite formation of PC12 cells. Int J Nanomedicine 2019; 14:7683-7694. [PMID: 31571871 PMCID: PMC6756831 DOI: 10.2147/ijn.s217416] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 08/08/2019] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Nerve regeneration is important for the treatment of degenerative diseases and neurons injured by accidents. Nerve growth factor (NGF) has been previously conjugated to materials for promotion of neurogenesis. MATERIALS AND METHODS Photoreactive gelatin was prepared by chemical coupling of gelatin with azidobenzoic acid (P-gel), and then NGF was immobilized on substrates in the presence or absence of micropatterned photomasks. UV irradiation induced crosslinking reactions of P-gel with itself, NGF, and the plate for immobilization. RESULTS By adjustment of the P-gel concentration, the nanometer-order height of micropatterns was controlled. NGF was quantitatively immobilized with increasing amounts of P-gel. Immobilized NGF induced neurite outgrowth of PC12 cells, a cell line derived from a pheochromocytoma of the rat adrenal medulla, at the same level as soluble NGF. The immobilized NGF showed higher thermal stability than the soluble NGF and was repeatedly used without loss of biological activity. The 3D structure (height of the formed micropattern) regulated the behavior of neurite guidance. As a result, the orientation of neurites was regulated by the stripe pattern width. CONCLUSION The micropattern-immobilized NGF nanolayer biochemically and topologically regulated neurite formation.
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Affiliation(s)
- Seong Min Kim
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama351-0198, Japan
- Department of Bioengineering, School of Engineering, The University of Tokyo, Tokyo113-8656, Japan
| | - Masashi Ueki
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama351-0198, Japan
| | - Xueli Ren
- Emergent Bioengineering Materials Research Team, RIKEN Center for Emergent Matter Science, Wako, Saitama351-0198, Japan
| | - Jun Akimoto
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama351-0198, Japan
| | - Yasuyuki Sakai
- Department of Bioengineering, School of Engineering, The University of Tokyo, Tokyo113-8656, Japan
| | - Yoshihiro Ito
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama351-0198, Japan
- Emergent Bioengineering Materials Research Team, RIKEN Center for Emergent Matter Science, Wako, Saitama351-0198, Japan
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Ham TR, Cox DG, Leipzig ND. Concurrent Delivery of Soluble and Immobilized Proteins to Recruit and Differentiate Neural Stem Cells. Biomacromolecules 2019; 20:3445-3452. [PMID: 31460746 DOI: 10.1021/acs.biomac.9b00719] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Insufficient endogenous neural stem cell (NSC) migration to injury sites and incomplete replenishment of neurons complicates recovery following central nervous system (CNS) injury. Such insufficient migration can be addressed by delivering soluble chemotactic factors, such as stromal cell-derived factor 1-α (SDF-1α), to sites of injury. However, simply enhancing NSC migration is likely to result in insufficient regeneration, as the cells need to be given additional signals. Immobilized proteins, such as interferon-γ (IFN-γ) can encourage neurogenic differentiation of NSCs. Here, we combined both protein delivery paradigms: soluble SDF-1α delivery to enhance NSC migration alongside covalently tethered IFN-γ to differentiate the recruited NSCs into neurons. To slow the release of soluble SDF-1α, we copolymerized methacrylated heparin with methacrylamide chitosan (MAC), to which we tethered IFN-γ. We found that this hydrogel system could result in soft hydrogels with a ratio of up to 70:30 MAC/heparin by mass, which enabled the continuous release of SDF-1α over a period of 2 weeks. The hydrogels recruited NSCs in vitro over 2 weeks, proportional to their release rate: the 70:30 heparin gels recruited a consistent number of NSCs at each time point, while the formulations with less heparin recruited NSCs at only early time points. After remaining in contact with the hydrogels for 8 days, NSCs successfully differentiated into neurons. CNS regeneration is a complex challenge, and this system provides a foundation to address multiple aspects of that challenge.
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Affiliation(s)
- Trevor R Ham
- Department of Biomedical Engineering, Auburn Science and Engineering Center 275, West Tower , The University of Akron , Akron , Ohio 44325 , United States
| | - Dakotah G Cox
- Department of Chemical and Biomolecular Engineering, Whitby 211 , The University of Akron , Akron , Ohio 44325 , United States
| | - Nic D Leipzig
- Department of Biomedical Engineering, Auburn Science and Engineering Center 275, West Tower , The University of Akron , Akron , Ohio 44325 , United States.,Department of Chemical and Biomolecular Engineering, Whitby 211 , The University of Akron , Akron , Ohio 44325 , United States
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7
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Affiliation(s)
- Yoshihiro Ito
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Emergent Bioengineering Materials Research Team, RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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Li X, Ma W, Shestopalov AA. Vapor-Phase Carbenylation of Hard and Soft Material Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:11386-11394. [PMID: 27759398 DOI: 10.1021/acs.langmuir.6b02471] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This study describes the formation of functional organic monolayers on hard and soft interfaces via a vapor-phase carbene insertion into Si-H and C-H bonds. We demonstrate that functional diazirine molecules can be used to form monomolecular coatings on silicon, silicon nitride, and urethane-acrylate polymers under mild vacuum conditions and exposure to UV light. We investigate the molecular coverage and the long-term stability of the resulting monolayers in air, isopropanol, and water. Our results suggest that vapor-phase carbenylation can be used as a complementary technology to the traditional self-assembly, permitting functionalization of various passivated substrates with stable and functional molecular coatings under mild and scalable conditions.
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Affiliation(s)
- Xunzhi Li
- Department of Chemical Engineering, University of Rochester , Rochester, New York 14627, United States
| | - Wenchuan Ma
- Department of Chemical Engineering, University of Rochester , Rochester, New York 14627, United States
| | - Alexander A Shestopalov
- Department of Chemical Engineering, University of Rochester , Rochester, New York 14627, United States
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9
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Trimaille T, Pertici V, Gigmes D. Recent advances in synthetic polymer based hydrogels for spinal cord repair. CR CHIM 2016. [DOI: 10.1016/j.crci.2015.03.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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McCormick AM, Jarmusik NA, Leipzig ND. Co-immobilization of semaphorin3A and nerve growth factor to guide and pattern axons. Acta Biomater 2015; 28:33-44. [PMID: 26391495 DOI: 10.1016/j.actbio.2015.09.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 07/27/2015] [Accepted: 09/17/2015] [Indexed: 12/25/2022]
Abstract
Immobilization of axon guidance cues offers a powerful tissue regenerative strategy to control the presentation and spatial location of these biomolecules. We use our previously developed immobilization strategy to specifically tether recombinant biotinylated nerve growth factor (bNGF) and biotinylated semaphorin3A (bSema3A) to chitosan films as an outgrowth and guidance platform. DRG neurite length and number for a range of single cues of immobilized bNGF or bSema3A were examined to determine a concentration response. Next single and dual cues of bNGF and bSema3A were immobilized and DRG guidance was assessed in response to a step concentration change from zero. Overall, immobilized groups caused axon extension, retraction and turning depending on the ratio of bNGF and bSema3A immobilized in the encountered region. This response indicated the exquisite sensitivity of DRG axons to both attractive and repulsive tethered cues. bSema3A concentrations of 0.10 and 0.49 ng/mm(2), when co-immobilized with bNGF (at 0.86 and 0.43 ng/mm(2) respectively), caused axons to turn away from the co-immobilized region. Immunocytochemical analysis showed that at these bSema3A concentrations, axons inside the co-immobilized region display microtubule degradation and breakdown of actin filaments. At the lowest bSema3A concentration (0.01 ng/mm(2)) co-immobilized with a higher bNGF concentration (2.16 ng/mm(2)), neurite lengths are shorter in the immobilized area, but bNGF dominates the guidance mechanism as neurites are directed toward the immobilized region. Future applications can pattern these cues in various geometries and gradients in order to better modulate axon guidance in terms of polarity, extension and branching. STATEMENT OF SIGNIFICANCE Nervous system formation and regeneration requires key molecules for guiding the growth cone and nervous system patterning. In vivo these molecules work in conjunction with one another to modulate axon guidance, and often they are tethered to limit spatial distribution. The novelty of this research is that we provide a specific attachment method to immobilize an attractive signal, nerve growth factor, along with an inhibitory cue, semaphorin3A, to a substrate in order to analyze the interplay of these proteins on axon guidance responses. The scientific impact of this manuscript is that we show that dual-cued platforms are necessary in order to finetune and tailor specific axon responses for varying neuronal regenerative purposes.
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Affiliation(s)
- Aleesha M McCormick
- Department of Chemical and Biomolecular Engineering, The University of Akron, OH, USA
| | - Natalie A Jarmusik
- Department of Chemical and Biomolecular Engineering, The University of Akron, OH, USA
| | - Nic D Leipzig
- Department of Chemical and Biomolecular Engineering, The University of Akron, OH, USA.
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Kador KE, Alsehli HS, Zindell AN, Lau LW, Andreopoulos FM, Watson BD, Goldberg JL. Retinal ganglion cell polarization using immobilized guidance cues on a tissue-engineered scaffold. Acta Biomater 2014; 10:4939-4946. [PMID: 25194930 PMCID: PMC4254021 DOI: 10.1016/j.actbio.2014.08.032] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 07/28/2014] [Accepted: 08/27/2014] [Indexed: 12/30/2022]
Abstract
Cell transplantation therapies to treat diseases related to dysfunction of retinal ganglion cells (RGCs) are limited in part by an inability to navigate to the optic nerve head within the retina. During development, RGCs are guided by a series of neurotrophic factors and guidance cues; however, these factors and their receptors on the RGCs are developmentally regulated and often not expressed during adulthood. Netrin-1 is a guidance factor capable of guiding RGCs in culture and relevant to guiding RGC axons toward the optic nerve head in vivo. Here we immobilized Netrin-1 using UV-initiated crosslinking to form a gradient capable of guiding the axonal growth of RGCs on a radial electrospun scaffold. Netrin-gradient scaffolds promoted both the percentage of RGCs polarized with a single axon, and also the percentage of cells polarized toward the scaffold center, from 31% to 52%. Thus, an immobilized protein gradient on a radial electrospun scaffold increases RGC axon growth in a direction consistent with developmental optic nerve head guidance, and may prove beneficial for use in cell transplant therapies for the treatment of glaucoma and other optic neuropathies.
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Affiliation(s)
- Karl E Kador
- Shiley Eye Center and Institute of Engineering in Medicine, University of California San Diego, La Jolla, CA 92093, USA; Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, FL 33136, USA
| | - Haneen S Alsehli
- Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, FL 33136, USA; Department of Biomedical Sciences, Barry University, Miami Shores, FL 33161, USA
| | - Allison N Zindell
- Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, FL 33136, USA; Department of Biomedical Engineering, University of Miami, Coral Gables, FL 33136, USA
| | - Lung W Lau
- Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, FL 33136, USA
| | - Fotios M Andreopoulos
- Department of Biomedical Engineering, University of Miami, Coral Gables, FL 33136, USA; Department of Surgery, Miller School of Medicine, University of Miami, FL 33136, USA
| | - Brant D Watson
- Department of Biomedical Engineering, University of Miami, Coral Gables, FL 33136, USA; Department of Neurology, Miller School of Medicine, University of Miami, FL 33136, USA
| | - Jeffrey L Goldberg
- Shiley Eye Center and Institute of Engineering in Medicine, University of California San Diego, La Jolla, CA 92093, USA; Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, FL 33136, USA.
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McCormick AM, Maddipatla MVSN, Shi S, Chamsaz EA, Yokoyama H, Joy A, Leipzig ND. Micropatterned coumarin polyester thin films direct neurite orientation. ACS APPLIED MATERIALS & INTERFACES 2014; 6:19655-19667. [PMID: 25347606 DOI: 10.1021/am5044328] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Guidance and migration of cells in the nervous system is imperative for proper development, maturation, and regeneration. In the peripheral nervous system (PNS), it is challenging for axons to bridge critical-sized injury defects to achieve repair and the central nervous system (CNS) has a very limited ability to regenerate after injury because of its innate injury response. The photoreactivity of the coumarin polyester used in this study enables efficient micropatterning using a custom digital micromirror device (DMD) and has been previously shown to be biodegradable, making these thin films ideal for cell guidance substrates with potential for future in vivo applications. With DMD, we fabricated coumarin polyester thin films into 10×20 μm and 15×50 μm micropatterns with depths ranging from 15 to 20 nm to enhance nervous system cell alignment. Adult primary neurons, oligodendrocytes, and astrocytes were isolated from rat brain tissue and seeded onto the polymer surfaces. After 24 h, cell type and neurite alignment were analyzed using phase contrast and fluorescence imaging. There was a significant difference (p<0.0001) in cell process distribution for both emergence angle (from the body of the cell) and orientation angle (at the tip of the growth cone) confirming alignment on patterned surfaces compared to control substrates (unpatterned polymer and glass surfaces). The expected frequency distribution for parallel alignment (≤15°) is 14% and the two micropatterned groups ranged from 42 to 49% alignment for emergence and orientation angle measurements, where the control groups range from 12 to 22% for parallel alignment. Despite depths being 15 to 20 nm, cell processes could sense these topographical changes and preferred to align to certain features of the micropatterns like the plateau/channel interface. As a result this initial study in utilizing these new DMD micropatterned coumarin polyester thin films has proven beneficial as an axon guidance platform for future nervous system regenerative strategies.
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Affiliation(s)
- Aleesha M McCormick
- Chemical and Biomolecular Engineering and ‡Department of Polymer Science, The University of Akron , Akron, Ohio 44325, United States
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Li H, Koenig AM, Sloan P, Leipzig ND. In vivo assessment of guided neural stem cell differentiation in growth factor immobilized chitosan-based hydrogel scaffolds. Biomaterials 2014; 35:9049-57. [DOI: 10.1016/j.biomaterials.2014.07.038] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 07/21/2014] [Indexed: 01/01/2023]
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McCormick AM, Jarmusik NA, Endrizzi EJ, Leipzig ND. Expression, isolation, and purification of soluble and insoluble biotinylated proteins for nerve tissue regeneration. J Vis Exp 2014:e51295. [PMID: 24513608 PMCID: PMC4089494 DOI: 10.3791/51295] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Recombinant protein engineering has utilized Escherichia coli (E. coli) expression systems for nearly 4 decades, and today E. coli is still the most widely used host organism. The flexibility of the system allows for the addition of moieties such as a biotin tag (for streptavidin interactions) and larger functional proteins like green fluorescent protein or cherry red protein. Also, the integration of unnatural amino acids like metal ion chelators, uniquely reactive functional groups, spectroscopic probes, and molecules imparting post-translational modifications has enabled better manipulation of protein properties and functionalities. As a result this technique creates customizable fusion proteins that offer significant utility for various fields of research. More specifically, the biotinylatable protein sequence has been incorporated into many target proteins because of the high affinity interaction between biotin with avidin and streptavidin. This addition has aided in enhancing detection and purification of tagged proteins as well as opening the way for secondary applications such as cell sorting. Thus, biotin-labeled molecules show an increasing and widespread influence in bioindustrial and biomedical fields. For the purpose of our research we have engineered recombinant biotinylated fusion proteins containing nerve growth factor (NGF) and semaphorin3A (Sema3A) functional regions. We have reported previously how these biotinylated fusion proteins, along with other active protein sequences, can be tethered to biomaterials for tissue engineering and regenerative purposes. This protocol outlines the basics of engineering biotinylatable proteins at the milligram scale, utilizing a T7 lac inducible vector and E. coli expression hosts, starting from transformation to scale-up and purification.
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