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Roberts CT, Beck SK, Prejean CM, Graul LM, Maitland DJ, Grunlan MA. Star-PCL shape memory polymer (SMP) scaffolds with tunable transition temperatures for enhanced utility. J Mater Chem B 2024; 12:3694-3702. [PMID: 38529581 PMCID: PMC11022546 DOI: 10.1039/d4tb00050a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 03/13/2024] [Indexed: 03/27/2024]
Abstract
Thermoresponsive shape memory polymers (SMPs) prepared from UV-curable poly(ε-caprolactone) (PCL) macromers have the potential to create self-fitting bone scaffolds, self-expanding vaginal stents, and other shape-shifting devices. To ensure tissue safety during deployment, the shape actuation temperature (i.e., the melt transition temperature or Tm of PCL) must be reduced from ∼55 °C that is observed for scaffolds prepared from linear-PCL-DA (Mn ∼ 10 kg mol-1). Moreover, increasing the rate of biodegradation would be advantageous, facilitating bone tissue healing and potentially eliminating the need for stent retrieval. Herein, a series of six UV-curable PCL macromers were prepared with linear or 4-arm star architectures and with Mns of 10, 7.5, and 5 kg mol-1, and subsequently fabricated into six porous scaffold compositions (10k, 7.5k, 5k, 10k★, 7.5k★, and 5k★) via solvent casting particulate leaching (SCPL). Scaffolds produced from star-PCL-tetraacrylate (star-PCL-TA) macromers produced pronounced reductions in Tm with decreased Mnversus those formed with the corresponding linear-PCL-diacrylate (linear-PCL-DA) macromers. Scaffolds were produced with the desired reduced Tm profiles: 37 °C < Tm < 55 °C (self-fitting bone scaffold), and Tm ≤ 37 °C (self-expanding stent). As macromer Mn decreased, crosslink density increased while % crystallinity decreased, particularly for scaffolds prepared from star-PCL-TA macromers. While shape memory behavior was retained and radial expansion pressure increased, this imparted a reduction in modulus but with an increase in the rate of degradation.
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Affiliation(s)
- Courteney T Roberts
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, USA.
| | - Sarah K Beck
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, USA.
| | - C Mabel Prejean
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, USA.
| | - Lance M Graul
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, USA.
| | - Duncan J Maitland
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, USA.
| | - Melissa A Grunlan
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, USA.
- Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843, USA
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA
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Pfau MR, McKinzey KG, Roth AA, Graul LM, Maitland DJ, Grunlan MA. Shape memory polymer (SMP) scaffolds with improved self-fitting properties. J Mater Chem B 2021; 9:3826-3837. [PMID: 33979417 DOI: 10.1039/d0tb02987d] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
"Self-fitting" shape memory polymer (SMP) scaffolds prepared as semi-interpenetrating networks (semi-IPNs) with crosslinked linear-poly(ε-caprolactone)-diacrylate (PCL-DA, Mn∼10 kg mol-1) and linear-poly(l-lactic acid) (PLLA, Mn∼15 kg mol-1) [75/25 wt%] exhibited robust mechanical properties and accelerated degradation rates versus a PCL-DA scaffold control. However, their potential to treat irregular craniomaxillofacial (CMF) bone defects is limited by their relatively high fitting temperature (Tfit∼55 °C; related to the Tm of PCL) required for shape recovery (i.e. expansion) and subsequent shape fixation during press fitting of the scaffold, which can be harmful to surrounding tissue. Additionally, the viscosity of the solvent-based precursor solutions, cast over a fused salt template during fabrication, can limit scaffold size. Thus, in this work, analogous semi-IPN SMP scaffolds were formed with a 4-arm star-PCL-tetracryalate (star-PCL-TA) (Mn∼10 kg mol-1) and star-PLLA (Mn∼15 kg mol-1). To assess the impact of a star-polymer architecture, four semi-IPN compositions were prepared: linear-PCL-DA/linear-PLLA (L/L), linear-PCL-DA/star-PLLA (L/S), star-PCL-TA/linear-PLLA (S/L) and star-PCL-TA/star-PLLA (S/S). Two PCL controls were also prepared: LPCL (i.e. 100% linear-PCL-DA) and SPCL (i.e. 100% star-PCL-TA). The S/S semi-IPN scaffold exhibited particularly desirable properties. In addition to achieving a lower, tissue-safe Tfit (∼45 °C), it exhibited the fastest rate of degradation which is anticipated to more favourably permit neotissue infiltration. The radial expansion pressure exerted by the S/S semi-IPN scaffold at Tfit was greater than that of LPCL, which is expected to enhance osseointegration and mechanical stability. The intrinsic viscosity of the S/S semi-IPN macromer solution was also reduced such that larger scaffold specimens could be prepared.
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Affiliation(s)
- Michaela R Pfau
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA.
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Jessen SL, Friedemann MC, Mullen AE, Ginn-Hedman AM, Herting SM, Maitland DJ, Clubb FJ. Micro-CT and histopathology methods to assess host response of aneurysms treated with shape memory polymer foam-coated coils versus bare metal coil occlusion devices. J Biomed Mater Res B Appl Biomater 2020; 108:2238-2249. [PMID: 31961062 PMCID: PMC7379400 DOI: 10.1002/jbm.b.34561] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 12/04/2019] [Accepted: 01/07/2020] [Indexed: 11/06/2022]
Abstract
Recent studies utilizing shape memory polymer foams to coat embolizing coils have shown potential benefits over current aneurysm treatments. In the current study utilizing a rabbit-elastase aneurysm model, the performance of test article (foam-coated coil [FCC]) and control (bare platinum coils [BPCs]) devices were compared at 30, 90, and 180 days using micro-CT and histological assessments. The host response was measured by identifying the cells regionally present within the aneurysm, and assessing the degree of residual debris and connective tissue. The 3D reconstructions of aneurysms provided context for histologic findings, and aided in the overall aneurysm assessment. At all time points, >75% of the cells categorized in each aneurysm were associated with a bioactive yet biocompatible host response (vs. the remainder of cells that were associated with acute inflammation). The extracellular matrix exhibited a transition from residual fibrin at 30 days to a greater degree of connective tissue at 90 and 180 days. Although the control BPC-treated aneurysms exhibited a greater degree of connective tissue at the earliest time point examined (30 days), by 180 days, the FCC-treated aneurysms had more connective tissue and less debris overall than the control aneurysms. When considering cell types and extracellular matrix composition, the overall host response scores were significantly better in FCC-treated aneurysms at the later time point. Based on the results of these metrics, the FCC device may lead to an advanced tissue remodeling response over BPC occlusion devices.
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Affiliation(s)
- Staci L. Jessen
- Department of Veterinary Pathobiology, Texas A&M University, College Station, Texas
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas
| | - Molly C. Friedemann
- Department of Veterinary Pathobiology, Texas A&M University, College Station, Texas
| | - Annmarie E. Mullen
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas
| | | | - Scott M. Herting
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas
| | - Duncan J. Maitland
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas
| | - Fred J. Clubb
- Department of Veterinary Pathobiology, Texas A&M University, College Station, Texas
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas
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Horn JD, Maitland DJ, Hartman J, Ortega JM. A computational thrombus formation model: application to an idealized two-dimensional aneurysm treated with bare metal coils. Biomech Model Mechanobiol 2018; 17:1821-1838. [DOI: 10.1007/s10237-018-1059-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 07/21/2018] [Indexed: 10/28/2022]
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Wierzbicki MA, Raines SB, Gordon SG, Criscione JC, Saunders AB, Birch S, Due B, Keller B, Nash LD, Miller MW, Maitland DJ. An experimental canine patent ductus arteriosus occlusion device based on shape memory polymer foam in a nitinol cage. J Mech Behav Biomed Mater 2017; 75:279-292. [PMID: 28759840 DOI: 10.1016/j.jmbbm.2017.07.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 07/19/2017] [Accepted: 07/24/2017] [Indexed: 12/01/2022]
Abstract
Patent ductus arteriosus (PDA) is a congenital cardiovascular defect in which a fetal connection between the aorta and pulmonary artery does not spontaneously close shortly after birth. If left uncorrected serious complications and even death can occur. Surgical ligation is the traditional treatment method; however, it is an invasive procedure, that motivates development of a minimally invasive option. Shape memory polymer (SMP) foams are unique materials that hold promise in the field of minimally invasive occlusion devices. In this work, a prototype nitinol foam cage (NFC) incorporating SMP foams has been designed and evaluated in multiple mechanical and in vitro verification tests. The NFC demonstrated acceptable fatigue resistance in a preliminary strut integrity test, withstanding one million cycles without complete strut fracture. Radial force analysis of both thick- and thin-walled prototype variations generated less vessel distension and wall tension in a vessel mimic compared to a commercial device. The NFCs exhibited negligible in vitro migration, comparable to that of a commercial device, using simplified, ideal models of PDA. Deployment characteristics of the prototypes were evaluated and compared to that of a commercial device when delivered into physiological models of PDA. During mock deployments, a veterinary cardiologist noted that, while deliverable, the thin-walled NFC prototype exhibited poor deployment characteristics, however the thick-walled NFC had deployment characteristics comparable to that of a commercial device. The promising results of this study warrant further investigation of the NFC device for canine PDA closure.
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Affiliation(s)
- Mark A Wierzbicki
- Department of Biomedical Engineering, Texas A&M University, MS 3120, 5045 Emerging Technologies Building, College Station, TX 77843, USA
| | - Sarah B Raines
- Department of Electrical Engineering, Texas A&M University, USA
| | - Sonya G Gordon
- Department of Small Animal Clinical Sciences of Veterinary Medicine and Biomedical Sciences, Texas A&M University, USA
| | - John C Criscione
- Department of Biomedical Engineering, Texas A&M University, MS 3120, 5045 Emerging Technologies Building, College Station, TX 77843, USA
| | - Ashley B Saunders
- Department of Small Animal Clinical Sciences of Veterinary Medicine and Biomedical Sciences, Texas A&M University, USA
| | - Scott Birch
- The Center for Educational Technologies, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, USA
| | - Bradley Due
- Department of Biomedical Engineering, Texas A&M University, MS 3120, 5045 Emerging Technologies Building, College Station, TX 77843, USA
| | - Brandis Keller
- Department of Biomedical Engineering, Texas A&M University, MS 3120, 5045 Emerging Technologies Building, College Station, TX 77843, USA
| | - Landon D Nash
- Department of Biomedical Engineering, Texas A&M University, MS 3120, 5045 Emerging Technologies Building, College Station, TX 77843, USA
| | - Matthew W Miller
- Texas Institute for Preclinical Studies, Texas A&M University, MS 4478, College Station, TX 77845, USA
| | - Duncan J Maitland
- Department of Biomedical Engineering, Texas A&M University, MS 3120, 5045 Emerging Technologies Building, College Station, TX 77843, USA.
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Saunders A, Keefe L, Birch S, Wierzbicki M, Maitland D. Perceptions of transcatheter device closure of patent ductus arteriosus in veterinary cardiology and evaluation of a canine model to simulate device placement: a preliminary study. J Vet Cardiol 2017; 19:268-275. [DOI: 10.1016/j.jvc.2017.04.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 03/23/2017] [Accepted: 04/17/2017] [Indexed: 10/19/2022]
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Chan BQY, Low ZWK, Heng SJW, Chan SY, Owh C, Loh XJ. Recent Advances in Shape Memory Soft Materials for Biomedical Applications. ACS APPLIED MATERIALS & INTERFACES 2016; 8:10070-10087. [PMID: 27018814 DOI: 10.1021/acsami.6b01295] [Citation(s) in RCA: 176] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Shape memory polymers (SMPs) are smart and adaptive materials able to recover their shape through an external stimulus. This functionality, combined with the good biocompatibility of polymers, has garnered much interest for biomedical applications. In this review, we discuss the design considerations critical to the successful integration of SMPs for use in vivo. We also highlight recent work on three classes of SMPs: shape memory polymers and blends, shape memory polymer composites, and shape memory hydrogels. These developments open the possibility of incorporating SMPs into device design, which can lead to vast technological improvements in the biomedical field.
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Affiliation(s)
- Benjamin Qi Yu Chan
- Institute of Materials Research and Engineering (IMRE) , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
- Department of Materials Science and Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117576, Singapore
| | - Zhi Wei Kenny Low
- Institute of Materials Research and Engineering (IMRE) , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
- Department of Materials Science and Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117576, Singapore
| | - Sylvester Jun Wen Heng
- Institute of Materials Research and Engineering (IMRE) , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
- Department of Materials Science and Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117576, Singapore
| | - Siew Yin Chan
- Institute of Materials Research and Engineering (IMRE) , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
- School of Science, Monash University Malaysia , Bandar Sunway, 47500 Selangor Darul Ehsan, Malaysia
| | - Cally Owh
- Institute of Materials Research and Engineering (IMRE) , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
| | - Xian Jun Loh
- Institute of Materials Research and Engineering (IMRE) , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
- Department of Materials Science and Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117576, Singapore
- Singapore Eye Research Institute , 11 Third Hospital Avenue, Singapore 168751, Singapore
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