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Donehoo DA, Collier CA, VandenHeuvel SN, Roy S, Solberg SC, Raghavan SA. Degrees of macrophage-facilitated healing in aneurysm occlusion devices. J Biomed Mater Res B Appl Biomater 2024; 112:e35385. [PMID: 38345190 DOI: 10.1002/jbm.b.35385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 12/05/2023] [Accepted: 01/27/2024] [Indexed: 02/15/2024]
Abstract
Insufficient healing of aneurysms following treatment with vascular occlusion devices put patients at severe risk of fatal rupture. Therefore, promoting healing and not just occlusion is vital to enhance aneurysm healing. Following occlusion device implantation, healing is primarily orchestrated by macrophage immune cells, ending with fibroblasts depositing collagen to stabilize the aneurysm neck and dome, preventing rupture. Several modified occlusion devices are available currently on-market. Previous in vivo work demonstrated that modifications of occlusion devices with a shape memory polymer foam had enhanced aneurysm healing outcomes. To better understand cellular response to occlusion devices and improve aneurysm occlusion device design variables, we developed an in vitro assay to isolate prominent interactions between devices and key healing players: macrophages and fibroblasts. We used THP-1 monocyte derived macrophages and human dermal fibroblasts in our cell culture models. Macrophages were allowed device contact with on-market competitor aneurysm occlusion devices for up to 96 h, to allow for any spontaneous device-driven macrophage activation. Macrophage secreted factors were captured in the culture media, in response to device-specific activation. Fibroblasts were then exposed to device-conditioned macrophage media (with secreted factors alone), to determine if there were any device-induced changes in collagen secretion. Our in vitro studies were designed to test the direct effect of devices on macrophage activation, and the indirect effect of devices on collagen secretion by fibroblasts to promote aneurysm healing and stabilization. Over 96 h, macrophages displayed significant migration toward and interaction with all tested devices. As compared to other devices, shape memory polymer foams (SMM, Shape Memory Medical) induced significant changes in gene expression indicating a shift toward an anti-inflammatory pro-healing M2-like phenotype. Similarly, macrophages in contact with SMM devices secreted more vascular endothelial growth factor (VEGF) compared with other devices. Macrophage conditioned media from SMM-contacted macrophages actively promoted fibroblast secretion of collagen, comparable to amounts observed with exogenous stimulation via VEGF supplementation. Our data indicate that SMM devices may promote good aneurysm healing outcomes, because collagen production is an essential step to ultimately stabilize an aneurysm.
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Affiliation(s)
- Del A Donehoo
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
| | - Claudia A Collier
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
| | | | - Sanjana Roy
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
| | - Spencer C Solberg
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
| | - Shreya A Raghavan
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
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2
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Niemann A, Tulamo R, Netti E, Preim B, Berg P, Cebral J, Robertson A, Saalfeld S. Multimodal exploration of the intracranial aneurysm wall. Int J Comput Assist Radiol Surg 2023; 18:2243-2252. [PMID: 36877287 PMCID: PMC10480333 DOI: 10.1007/s11548-023-02850-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 02/02/2023] [Indexed: 03/07/2023]
Abstract
PURPOSE Intracranial aneurysms (IAs) are pathological changes of the intracranial vessel wall, although clinical image data can only show the vessel lumen. Histology can provide wall information but is typically restricted to ex vivo 2D slices where the shape of the tissue is altered. METHODS We developed a visual exploration pipeline for a comprehensive view of an IA. We extract multimodal information (like stain classification and segmentation of histologic images) and combine them via 2D to 3D mapping and virtual inflation of deformed tissue. Histological data, including four stains, micro-CT data and segmented calcifications as well as hemodynamic information like wall shear stress (WSS), are combined with the 3D model of the resected aneurysm. RESULTS Calcifications were mostly present in the tissue part with increased WSS. In the 3D model, an area of increased wall thickness was identified and correlated to histology, where the Oil red O (ORO) stained images showed a lipid accumulation and the alpha-smooth muscle actin (aSMA) stained images showed a slight loss of muscle cells. CONCLUSION Our visual exploration pipeline combines multimodal information about the aneurysm wall to improve the understanding of wall changes and IA development. The user can identify regions and correlate how hemodynamic forces, e.g. WSS, are reflected by histological structures of the vessel wall, wall thickness and calcifications.
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Affiliation(s)
- Annika Niemann
- Department of Simulation and Graphics, Otto-von-Guericke University, Magdeburg, Germany
- STIMULATE Research Campus, Magdeburg, Germany
| | - Riikka Tulamo
- Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Eliisa Netti
- Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Bernhard Preim
- Department of Simulation and Graphics, Otto-von-Guericke University, Magdeburg, Germany
- STIMULATE Research Campus, Magdeburg, Germany
| | - Philipp Berg
- STIMULATE Research Campus, Magdeburg, Germany
- Department of Medical Engineering, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Juan Cebral
- Computational Hemodynamics Lab, Georg Mason University, Fairfax, USA
| | - Anne Robertson
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, USA
| | - Sylvia Saalfeld
- Department of Simulation and Graphics, Otto-von-Guericke University, Magdeburg, Germany.
- STIMULATE Research Campus, Magdeburg, Germany.
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3
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Karadeli HH, Kuram E. Single Component Polymers, Polymer Blends, and Polymer Composites for Interventional Endovascular Embolization of Intracranial Aneurysms. Macromol Biosci 2023:e2300432. [PMID: 37992206 DOI: 10.1002/mabi.202300432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 11/03/2023] [Indexed: 11/24/2023]
Abstract
Intracranial aneurysm is the abnormal focal dilation in brain arteries. When untreated, it can enlarge to rupture points and account for subarachnoid hemorrhage cases. Intracranial aneurysms can be treated by blocking the flow of blood to the aneurysm sac with clipping of the aneurysm neck or endovascular embolization with embolics to promote the formation of the thrombus. Coils or an embolic device are inserted endovascularly into the aneurysm via a micro-catheter to fill the aneurysm. Many embolization materials have been developed. An embolization coil made of soft and thin platinum wire called the "Guglielmi detachable coil" (GDC) enables safer treatment for brain aneurysms. However, patients may experience aneurysm recurrence because of incomplete coil filling or compaction over time. Unsatisfactory recanalization rates and incomplete occlusion are the drawbacks of endovascular embolization. So, the fabrication of new medical devices with less invasive surgical techniques is mandatory to enhance the long-term therapeutic performance of existing endovascular procedures. For this aim, the current article reviews polymeric materials including blends and composites employed for embolization of intracranial aneurysms. Polymeric materials used in embolic agents, their advantages and challenges, results of the strategies used to overcome treatment, and results of clinical experiences are summarized and discussed.
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Affiliation(s)
- Hasan Hüseyin Karadeli
- Department of Neurology, Istanbul Medeniyet University Göztepe Prof. Dr. Süleyman Yalçın City Hospital, Istanbul, 34722, Turkey
| | - Emel Kuram
- Department of Mechanical Engineering, Gebze Technical University, Kocaeli, 41400, Turkey
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Echeverría D, Rivera R, Giacaman P, Sordo JG, Einersen M, Badilla L. A novel self-expanding shape memory polymer coil for intracranial aneurysm embolization: 1 year follow-up in Chile. J Neurointerv Surg 2023; 15:781-786. [PMID: 35831177 PMCID: PMC10359521 DOI: 10.1136/jnis-2022-018996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 06/21/2022] [Indexed: 11/03/2022]
Abstract
BACKGROUND Aneurysm recurrence remains a challenge when coiling cerebral aneurysms. Development of next generation coils has focused on accelerating thrombus maturation and increasing coil packing density. Ultra low density shape memory polymer is a novel embolic material designed for this purpose. The polymer is crimped over a platinum-tungsten coil for catheter delivery and self-expands to a predefined volume on contact with blood. METHODS This prospective study in humans evaluated aneurysms 5-16 mm (inclusive) in diameter that were indicated for endovascular coil embolization. At least 70% coil volume was required to be shape memory polymer coils. Patients were followed-up according to standard of care for 12 months. RESULTS Nine patients (89% women, mean age 55.8±11.7 years) were treated with shape memory polymer coils and completed 12 months of follow-up. Aneurysms were all unruptured and were in the ophthalmic segment of the internal carotid artery (n=7), posterior communicating artery, and anterior cerebral artery A1-A2 segment. Aneurysms were a mean of 7.8±2.9 mm in diameter (range 5.2-14.9 mm). The mean packing density based on unexpanded polymer was 17±6%. Packing density based on expanded polymer was 43±13%. At 12 months, no recurrence had occurred, and a Raymond-Roy occlusion classification of 1 (n=5) or 2 (n=4) was observed. No serious adverse events related to the study device occurred over the 12 months after the procedure. CONCLUSIONS Shape memory polymer coils were safe and effective in treating intracranial aneurysms over 12 months in this first study in human subjects.
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Affiliation(s)
- Daniel Echeverría
- Neuroradiology, Instituto de Neurocirugía Dr Alfonso Asenjo, Santiago, Chile
- Department of Radiology, Universidad de Valparaíso, Valparaíso, Chile
| | - Rodrigo Rivera
- Neuroradiology, Instituto de Neurocirugía Dr Alfonso Asenjo, Santiago, Chile
- Department of Radiology, Universidad de Valparaíso, Valparaíso, Chile
| | - Pablo Giacaman
- Neurovascular Unit, Imaging Service, Hospital Clínico Regional Guillermo Grant Benavente, Concepción, Chile
| | - Juan Gabriel Sordo
- Neuroradiology, Instituto de Neurocirugía Dr Alfonso Asenjo, Santiago, Chile
- Department of Radiology, Universidad de Valparaíso, Valparaíso, Chile
| | - Martín Einersen
- Neurovascular Unit, Imaging Service, Hospital Clínico Regional Guillermo Grant Benavente, Concepción, Chile
- Faculty of Medicine, Department of Specialties (Imaging), Universidad de Concepción, Concepción, Chile
| | - Lautaro Badilla
- Neuroradiology, Instituto de Neurocirugía Dr Alfonso Asenjo, Santiago, Chile
- Department of Radiology, Universidad de Valparaíso, Valparaíso, Chile
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Vakil AU, Petryk NM, Du C, Howes B, Stinfort D, Serinelli S, Gitto L, Ramezani M, Beaman HT, Monroe MBB. In vitro and in vivo degradation correlations for polyurethane foams with tunable degradation rates. J Biomed Mater Res A 2023; 111:580-595. [PMID: 36752708 DOI: 10.1002/jbm.a.37504] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 12/19/2022] [Accepted: 01/13/2023] [Indexed: 02/09/2023]
Abstract
Polyurethane foams present a tunable biomaterial platform with potential for use in a range of regenerative medicine applications. Achieving a balance between scaffold degradation rates and tissue ingrowth is vital for successful wound healing, and significant in vivo testing is required to understand these processes. Vigorous in vitro testing can minimize the number of animals that are required to gather reliable data; however, it is difficult to accurately select in vitro degradation conditions that can effectively mimic in vivo results. To that end, we performed a comprehensive in vitro assessment of the degradation of porous shape memory polyurethane foams with tunable degradation rates using varying concentrations of hydrogen peroxide to identify the medium that closely mimics measured in vivo degradation rates. Material degradation was studied over 12 weeks in vitro in 1%, 2%, or 3% hydrogen peroxide and in vivo in subcutaneous pockets in Sprague Dawley rats. We found that the in vitro degradation conditions that best predicted in vivo degradation rates varied based on the number of mechanisms by which the polymer degraded and the polymer hydrophilicity. Namely, more hydrophilic materials that degrade by both hydrolysis and oxidation require lower concentrations of hydrogen peroxide (1%) to mimic in vivo rates, while more hydrophobic scaffolds that degrade by oxidation alone require higher concentrations of hydrogen peroxide (3%) to model in vivo degradation. This information can be used to rationally select in vitro degradation conditions that accurately identify in vivo degradation rates prior to characterization in an animal model.
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Affiliation(s)
- Anand Utpal Vakil
- Department of Biomedical and Chemical Engineering and BioInspired Syracuse, Institute for Material and Living Systems, Syracuse University, Syracuse, New York, USA
| | - Natalie Marie Petryk
- Department of Biomedical and Chemical Engineering and BioInspired Syracuse, Institute for Material and Living Systems, Syracuse University, Syracuse, New York, USA
| | - Changling Du
- Department of Biomedical and Chemical Engineering and BioInspired Syracuse, Institute for Material and Living Systems, Syracuse University, Syracuse, New York, USA
| | - Bryanna Howes
- Department of Chemistry, Le Moyne College, Syracuse, New York, USA
| | | | | | - Lorenzo Gitto
- SUNY Upstate Medical University, Syracuse, New York, USA
| | - Maryam Ramezani
- Department of Biomedical and Chemical Engineering and BioInspired Syracuse, Institute for Material and Living Systems, Syracuse University, Syracuse, New York, USA
| | - Henry T Beaman
- Department of Biomedical and Chemical Engineering and BioInspired Syracuse, Institute for Material and Living Systems, Syracuse University, Syracuse, New York, USA
| | - Mary Beth Browning Monroe
- Department of Biomedical and Chemical Engineering and BioInspired Syracuse, Institute for Material and Living Systems, Syracuse University, Syracuse, New York, USA
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6
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Pineda-Castillo SA, Stiles AM, Bohnstedt BN, Lee H, Liu Y, Lee CH. Shape Memory Polymer-Based Endovascular Devices: Design Criteria and Future Perspective. Polymers (Basel) 2022; 14:polym14132526. [PMID: 35808573 PMCID: PMC9269599 DOI: 10.3390/polym14132526] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/13/2022] [Accepted: 06/17/2022] [Indexed: 12/12/2022] Open
Abstract
Devices for the endovascular embolization of intracranial aneurysms (ICAs) face limitations related to suboptimal rates of lasting complete occlusion. Incomplete occlusion frequently leads to residual flow within the aneurysm sac, which subsequently causes aneurysm recurrence needing surgical re-operation. An emerging method for improving the rates of complete occlusion both immediately after implant and in the longer run can be the fabrication of patient-specific materials for ICA embolization. Shape memory polymers (SMPs) are materials with great potential for this application, owing to their versatile and tunable shape memory properties that can be tailored to a patient’s aneurysm geometry and flow condition. In this review, we first present the state-of-the-art endovascular devices and their limitations in providing long-term complete occlusion. Then, we present methods for the fabrication of SMPs, the most prominent actuation methods for their shape recovery, and the potential of SMPs as endovascular devices for ICA embolization. Although SMPs are a promising alternative for the patient-specific treatment of ICAs, there are still limitations that need to be addressed for their application as an effective coil-free endovascular therapy.
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Affiliation(s)
- Sergio A. Pineda-Castillo
- Biomechanics and Biomaterials Design Laboratory (BBDL), The University of Oklahoma, Norman, OK 73019, USA; (S.A.P.-C.); (A.M.S.)
- Stephenson School of Biomedical Engineering, The University of Oklahoma, Norman, OK 73019, USA
| | - Aryn M. Stiles
- Biomechanics and Biomaterials Design Laboratory (BBDL), The University of Oklahoma, Norman, OK 73019, USA; (S.A.P.-C.); (A.M.S.)
- School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA;
| | - Bradley N. Bohnstedt
- Department of Neurological Surgery, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
| | - Hyowon Lee
- Laboratory of Implantable Microsystems Research (LIMR), Weldon School of Biomedical Engineering, Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA;
| | - Yingtao Liu
- School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA;
| | - Chung-Hao Lee
- Biomechanics and Biomaterials Design Laboratory (BBDL), The University of Oklahoma, Norman, OK 73019, USA; (S.A.P.-C.); (A.M.S.)
- School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA;
- Correspondence:
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7
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Hasan SM, Touchet T, Jayadeep A, Maitland DJ. Controlling Morphology and Physio-Chemical Properties of Stimulus-Responsive Polyurethane Foams by Altering Chemical Blowing Agent Content. Polymers (Basel) 2022; 14:polym14112288. [PMID: 35683960 PMCID: PMC9183079 DOI: 10.3390/polym14112288] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 05/25/2022] [Accepted: 06/01/2022] [Indexed: 12/16/2022] Open
Abstract
Amorphous shape memory polymer foams are currently used as components in vascular occlusion medical devices such as the IMPEDE and IMPEDE-FX Embolization Plugs. Body temperature and moisture-driven actuation of the polymeric foam is necessary for vessel occlusion and the rate of expansion is a function of physio-chemical material properties. In this study, concentrations of the chemical blowing agent for the foam were altered and the resulting effects on morphology, thermal and chemical properties, and actuation rates were studied. Lower concentration of chemical blowing agent yielded foams with thick foam struts due to less bubble formation during the foaming process. Foams with thicker struts also had high tensile modulus and lower strain at break values compared to the foams made with higher blowing agent concentration. Additionally, less blowing agent resulted in foams with a lower glass transition temperature due to less urea formation during the foaming reaction. This exploratory study provides an approach to control thermo-mechanical foam properties and morphology by tuning concentrations of a foaming additive. This work aims to broaden the applications of shape memory polymer foams for medical use.
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Affiliation(s)
- Sayyeda Marziya Hasan
- Shape Memory Medical Inc., Santa Clara, CA 95054, USA
- Correspondence: ; Tel.: +281-745-8366
| | - Tyler Touchet
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA; (T.T.); (D.J.M.)
| | - Aishwarya Jayadeep
- Materials Science and Engineering, University of California, Berkeley, CA 94720, USA;
| | - Duncan J. Maitland
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA; (T.T.); (D.J.M.)
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8
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Chau SM, Herting SM, Noltensmeyer DA, Ahmed H, Maitland DJ, Raghavan S. Macrophage activation in response to shape memory polymer foam-coated aneurysm occlusion devices. J Biomed Mater Res B Appl Biomater 2022; 110:1535-1544. [PMID: 35090200 DOI: 10.1002/jbm.b.35015] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 12/17/2021] [Accepted: 01/19/2022] [Indexed: 01/30/2023]
Abstract
Brain aneurysms can be treated with embolic coils using minimally invasive approaches. It is advantageous to modulate the biologic response of platinum embolic coils. Our previous studies demonstrated that shape memory polymer (SMP) foam coated embolization coils (FCC) devices demonstrate enhanced healing responses in animal models compared with standard bare platinum coil (BPC) devices. Macrophages are the most prevalent immune cell type that coordinate the greater immune response to implanted materials. Hence, we hypothesized that the highly porous SMP foam coatings on embolic coils activate a pro-regenerative healing phenotype. To test this hypothesis, we analyzed the number and type of infiltrating macrophages in FCC or BPC devices implanted in a rabbit elastase aneurysm model. FCC devices elicited a great number of infiltration macrophages, skewed significantly to a pro-regenerative M2-like phenotype 90 days following implantation. We devised an in vitro assay, where monocyte-derived macrophages were placed in close association with FCC or BPC devices for 6-72 h. Macrophages encountering SMP FCC-devices demonstrated highly mixed activation phenotypes at 6 h, heavily skewing toward an M2-like phenotype by 72 h, compared with macrophages encountering BPC devices. Macrophage activation was evaluated using gene expression analysis, and secreted cytokine evaluation. Together, our results demonstrate that FCC devices promoted a pro-regenerative macrophage activation phenotype, compared with BPC devices. Our in vitro findings corroborate with in vivo observations that SMP-based modification of embolic coils can promote better healing of the aneurysm site, by sustaining a pro-healing macrophage phenotype.
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Affiliation(s)
- Sarah M Chau
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
- TAMU Master of Biotechnology Program, Texas A&M University, College Station, Texas, USA
| | - Scott M Herting
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
| | - Dillon A Noltensmeyer
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
| | - Hamzah Ahmed
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
| | - Duncan J Maitland
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
| | - Shreya Raghavan
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, Texas, USA
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9
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Pisani S, Genta I, Modena T, Dorati R, Benazzo M, Conti B. Shape-Memory Polymers Hallmarks and Their Biomedical Applications in the Form of Nanofibers. Int J Mol Sci 2022; 23:1290. [PMID: 35163218 DOI: 10.3390/ijms23031290] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 01/20/2022] [Accepted: 01/20/2022] [Indexed: 12/28/2022] Open
Abstract
Shape-Memory Polymers (SMPs) are considered a kind of smart material able to modify size, shape, stiffness and strain in response to different external (heat, electric and magnetic field, water or light) stimuli including the physiologic ones such as pH, body temperature and ions concentration. The ability of SMPs is to memorize their original shape before triggered exposure and after deformation, in the absence of the stimulus, and to recover their original shape without any help. SMPs nanofibers (SMPNs) have been increasingly investigated for biomedical applications due to nanofiber’s favorable properties such as high surface area per volume unit, high porosity, small diameter, low density, desirable fiber orientation and nanoarchitecture mimicking native Extra Cellular Matrix (ECM). This review focuses on the main properties of SMPs, their classification and shape-memory effects. Moreover, advantages in the use of SMPNs and different biomedical application fields are reported and discussed.
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10
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Herting SM, Monroe MBB, Weems AC, Briggs ST, Fletcher GK, Blair SE, Hatch CJ, Maitland DJ. In vitro cytocompatibility testing of oxidative degradation products. J BIOACT COMPAT POL 2021. [DOI: 10.1177/08839115211003115] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Implantable medical devices must undergo thorough evaluation to ensure safety and efficacy before use in humans. If a device is designed to degrade, it is critical to understand the rate of degradation and the degradation products that will be released. Oxidative degradation is typically modeled in vitro by immersing materials or devices in hydrogen peroxide, which can limit further analysis of degradation products in many cases. Here we demonstrate a novel approach for testing the cytocompatibility of degradation products for oxidatively-degradable biomaterials where the materials are exposed to hydrogen peroxide, and then catalase enzyme is used to convert the hydrogen peroxide to water and oxygen so that the resulting aqueous solution can be added to cell culture media. To validate our results, expected degradation products are also synthesized then added to cell culture media. We used these methods to evaluate the cytocompatibility of degradation products from an oxidatively-degradable shape memory polyurethane designed in our lab and found that the degradation of these polymers is unlikely to cause a cytotoxic response in vivo based on the guidance provided by ISO 10993-5. These methods may also be applicable to other biocompatibility tests such as tests for mutagenicity or systemic toxicity, and evaluations of cell proliferation, migration, or gene and protein expression.
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Affiliation(s)
- Scott M Herting
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
| | - Mary Beth B Monroe
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
| | - Andrew C Weems
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
| | - Sam T Briggs
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
| | - Grace K Fletcher
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
| | - Samuel E Blair
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
| | - Christopher J Hatch
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
| | - Duncan J Maitland
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
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11
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Boire TC, Himmel LE, Yu F, Guth CM, Dollinger BR, Werfel TA, Balikov DA, Duvall CL. Effect of pore size and spacing on neovascularization of a biodegradble shape memory polymer perivascular wrap. J Biomed Mater Res A 2021; 109:272-288. [PMID: 32490564 PMCID: PMC8270373 DOI: 10.1002/jbm.a.37021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 04/11/2020] [Accepted: 04/19/2020] [Indexed: 12/13/2022]
Abstract
Neointimal hyperplasia (NH) is a main source of failures in arteriovenous fistulas and vascular grafts. Several studies have demonstrated the promise of perivascular wraps to reduce NH via promotion of adventitial neovascularization and providing mechanical support. Limited clinical success thus far may be due to inappropriate material selection (e.g., nondegradable, too stiff) and geometric design (e.g., pore size and spacing, diameter). The influence of pore size and spacing on implant neovascularization is investigated here for a new biodegradable, thermoresponsive shape memory polymer (SMP) perivascular wrap. Following an initial pilot, 21 mice were each implanted with six scaffolds: four candidate SMP macroporous designs (a-d), a nonporous SMP control (e), and microporous GORETEX (f). Mice were sacrificed after 4 (N = 5), 14 (N = 8), and 28 (N = 8) days. There was a statistically significant increase in neovascularization score between all macroporous groups compared to nonporous SMP (p < .023) and microporous GORETEX (p < .007) controls at Day 28. Wider-spaced, smaller-sized pore designs (223 μm-spaced, 640 μm-diameter Design c) induced the most robust angiogenic response, with greater microvessel number (p < .0114) and area (p < .0055) than nonporous SMPs and GORETEX at Day 28. This design also produced significantly greater microvessel density than nonporous SMPs (p = 0.0028) and a smaller-spaced, larger-sized pore (155 μm-spaced, 1,180 μm-sized Design b) design (p = .0013). Strong neovascularization is expected to reduce NH, motivating further investigation of this SMP wrap with controlled pore spacing and size in more advanced arteriovenous models.
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Affiliation(s)
- Timothy C Boire
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Lauren E Himmel
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Fang Yu
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Christy M Guth
- Department of Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Bryan R Dollinger
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Thomas A Werfel
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Biomedical Engineering Program, University of Mississippi, Oxford, Mississippi, USA
| | - Daniel A Balikov
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Craig L Duvall
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
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Christmas N, Vakil AU, Hatch CJ, Dong S, Fikhman D, Beaman HT, Monroe MBB. Characterization of shape memory polymer foam hemostats in in vitro hemorrhagic wound models. J Biomed Mater Res B Appl Biomater 2020; 109:681-692. [PMID: 32969163 DOI: 10.1002/jbm.b.34732] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/19/2020] [Accepted: 09/15/2020] [Indexed: 11/05/2022]
Abstract
Shape memory polymer foam hemostats are a promising option for future hemorrhage control in battlefield wounds. To enable their use as hemostatic devices, they must be optimized in terms of formulation and architecture, and their safety and efficacy must be characterized in animal models. Relevant in vitro models can be used for device optimization to help mitigate the excess use of animals and reduce costs of clinical translation. In this work, a simplified gunshot wound model and a grade V liver injury model were constructed. The models were used to characterize the effects of shape memory polymer foam hemostat geometry on wall pressures, application/removal times, hemorrhage (fluid loss), and fluid absorption in comparison with clinical controls. It was found that there is no benefit in over-sizing the hemostatic device relative to wound volume and that geometry effects are dependent upon the wound type. These models provide a rapid means for elucidation of promising hemostat geometries and formulations for use in future in vivo testing.
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Affiliation(s)
- Nakira Christmas
- Department of Biomedical and Chemical Engineering, Syracuse Biomaterials Institute, and BioInspired Syracuse, Syracuse University, Syracuse, New York, USA
| | - Anand Utpal Vakil
- Department of Biomedical and Chemical Engineering, Syracuse Biomaterials Institute, and BioInspired Syracuse, Syracuse University, Syracuse, New York, USA
| | - Christopher J Hatch
- Department of Biomedical Engineering, California Polytechnic State University, San Luis Obispo, California, USA
| | - Shi Dong
- Department of Biomedical and Chemical Engineering, Syracuse Biomaterials Institute, and BioInspired Syracuse, Syracuse University, Syracuse, New York, USA
| | - David Fikhman
- Department of Biomedical and Chemical Engineering, Syracuse Biomaterials Institute, and BioInspired Syracuse, Syracuse University, Syracuse, New York, USA
| | - Henry T Beaman
- Department of Biomedical and Chemical Engineering, Syracuse Biomaterials Institute, and BioInspired Syracuse, Syracuse University, Syracuse, New York, USA
| | - Mary Beth B Monroe
- Department of Biomedical and Chemical Engineering, Syracuse Biomaterials Institute, and BioInspired Syracuse, Syracuse University, Syracuse, New York, USA
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