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Article: Theoretical error of sectional method for estimation of shape memory polyurethane foam mass loss

Graul, Lance M. / Liu, Shuling / Maitland, Duncan J.

Journal of colloid and interface science. 2022 Nov., v. 625

2022

Abstract: Measuring in vivo degradation for polymeric scaffolds is critical for analysis of biocompatibility. Traditionally, histology has been used to estimate mass loss in scaffolds, allowing for simultaneous evaluation of mass loss and the biologic response to ... ...

Abstract	Measuring in vivo degradation for polymeric scaffolds is critical for analysis of biocompatibility. Traditionally, histology has been used to estimate mass loss in scaffolds, allowing for simultaneous evaluation of mass loss and the biologic response to the implant. Oxidatively degradable shape memory polyurethane (SMP) foams have been implemented in two vascular occlusion devices: peripheral embolization device (PED) and neurovascular embolization device (NED). This work explores the errors introduced when using histological sections to evaluate mass loss. Models of the SMP foams were created to mimic the device geometry and the tetrakaidekahedral structure of the foam pore. These models were degraded in Blender for a wide range of possible degradation amounts and the mass loss was estimated using m sections. As the number of sections (m) used to estimate mass loss for a volume increased the sampling error decreased and beyond m = 5, the decrease in error was insignificant. NED population and sampling errors were higher than for PED scenarios. When m ≥ 5, the averaged sampling error was below 1.5% for NED and 1% for PED scenarios. This study establishes a baseline sampling error for estimating randomly degraded porous scaffolds using a sectional method. Device geometry and the stage of mass loss influence the sampling error. Future studies will use non-random degradation to further investigate in vivo mass loss scenarios.
Keywords	biocompatibility ; foams ; geometry ; histology ; polyurethanes
Language	English
Dates of publication	2022-11
Size	p. 237-247.
Publishing place	Elsevier Inc.
Document type	Article
ZDB-ID	241597-5
ISSN	1095-7103 ; 0021-9797
ISSN (online)	1095-7103
ISSN	0021-9797
DOI	10.1016/j.jcis.2022.06.045
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Theoretical error of sectional method for estimation of shape memory polyurethane foam mass loss.

Graul, Lance M / Liu, Shuling / Maitland, Duncan J

Journal of colloid and interface science

2022 Volume 625, Page(s) 237–247

Abstract: Introduction: Measuring in vivo degradation for polymeric scaffolds is critical for analysis of biocompatibility. Traditionally, histology has been used to estimate mass loss in scaffolds, allowing for simultaneous evaluation of mass loss and the ... ...

Abstract	Introduction: Measuring in vivo degradation for polymeric scaffolds is critical for analysis of biocompatibility. Traditionally, histology has been used to estimate mass loss in scaffolds, allowing for simultaneous evaluation of mass loss and the biologic response to the implant. Oxidatively degradable shape memory polyurethane (SMP) foams have been implemented in two vascular occlusion devices: peripheral embolization device (PED) and neurovascular embolization device (NED). This work explores the errors introduced when using histological sections to evaluate mass loss. Methods: Models of the SMP foams were created to mimic the device geometry and the tetrakaidekahedral structure of the foam pore. These models were degraded in Blender for a wide range of possible degradation amounts and the mass loss was estimated using m sections. Results: As the number of sections (m) used to estimate mass loss for a volume increased the sampling error decreased and beyond m = 5, the decrease in error was insignificant. NED population and sampling errors were higher than for PED scenarios. When m ≥ 5, the averaged sampling error was below 1.5% for NED and 1% for PED scenarios. Discussion/conclusion: This study establishes a baseline sampling error for estimating randomly degraded porous scaffolds using a sectional method. Device geometry and the stage of mass loss influence the sampling error. Future studies will use non-random degradation to further investigate in vivo mass loss scenarios.
MeSH term(s)	Polymers ; Polyurethanes ; Porosity
Chemical Substances	Polymers ; Polyurethanes ; polyurethane foam (9009-54-5)
Language	English
Publishing date	2022-06-11
Publishing country	United States
Document type	Journal Article
ZDB-ID	241597-5
ISSN	1095-7103 ; 0021-9797
ISSN (online)	1095-7103
ISSN	0021-9797
DOI	10.1016/j.jcis.2022.06.045
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Article ; Online: Development and Characterization of Oxidatively Responsive Thiol-Ene Networks for Bone Graft Applications.

Touchet, Tyler / Briggs, Samuel / Graul, Lance / Maitland, Duncan J

ACS applied bio materials

2022 Volume 5, Issue 6, Page(s) 2633–2642

Abstract: First metatarsophalangeal joint (MPJ) arthroplasty procedures are a common podiatric procedure. However, almost one-third of cases require revision surgeries because of nonunions. Revision or salvage surgery requires more extensive hardware and bone ... ...

Abstract	First metatarsophalangeal joint (MPJ) arthroplasty procedures are a common podiatric procedure. However, almost one-third of cases require revision surgeries because of nonunions. Revision or salvage surgery requires more extensive hardware and bone grafts to recreate the first metatarsal. Unfortunately, salvage surgeries have a similar rate of failure attributed to delayed healing, bone graft dissolution, and the lack of bone ingrowth. Furthermore, patients who suffer from neuropathic comorbidities such as diabetes suffer from a diminished healing capacity. An increase in proinflammatory factors and the high presence of reactive oxygen species (ROS) present in diabetics are linked to lower fusion rates. To this end, there is a need for a clinically relevant bone graft to promote bone fusions in patients with neuropathic comorbidities. Incorporating thiol-ene networks for bone scaffolds has demonstrated increased osteogenic biomarkers over traditional polymeric materials. Furthermore, thiol-ene networks can act as antioxidants. Sulfide linkages within the network have an inherent ability to consume radical oxygen to create sulfoxide and sulfone groups. These unique properties of thiol-ene networks make them a promising candidate as bone grafts for diabetic patients. In this work, we propose a thiol-ene biomaterial to address the current limitations of MPJ fusion in diabetics by characterizing mechanical properties, degradation rates under accelerated conditions, and oxidative responsiveness under pathophysiologic conditions. We also demonstrated that thiol-ene-based materials could reduce the number of hydroxyl radicals associated with neuropathic comorbidities.
MeSH term(s)	Humans ; Materials Testing ; Polymers ; Sulfhydryl Compounds
Chemical Substances	Polymers ; Sulfhydryl Compounds
Language	English
Publishing date	2022-06-06
Publishing country	United States
Document type	Journal Article
ISSN	2576-6422
ISSN (online)	2576-6422
DOI	10.1021/acsabm.2c00103
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Article ; Online: Controlling Morphology and Physio-Chemical Properties of Stimulus-Responsive Polyurethane Foams by Altering Chemical Blowing Agent Content.

Hasan, Sayyeda Marziya / Touchet, Tyler / Jayadeep, Aishwarya / Maitland, Duncan J

Polymers

2022 Volume 14, Issue 11

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 ... ...

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.
Language	English
Publishing date	2022-06-04
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2527146-5
ISSN	2073-4360 ; 2073-4360
ISSN (online)	2073-4360
ISSN	2073-4360
DOI	10.3390/polym14112288
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Article ; Online: Star

Roberts, Courteney T / Beck, Sarah K / Prejean, C Mabel / Graul, Lance M / Maitland, Duncan J / Grunlan, Melissa A

Journal of materials chemistry. B

2024 Volume 12, Issue 15, Page(s) 3694–3702

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 ...

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 (
MeSH term(s)	Tissue Scaffolds ; Polyesters ; Transition Temperature ; Bone and Bones ; Temperature
Chemical Substances	Polyesters
Language	English
Publishing date	2024-04-17
Publishing country	England
Document type	Journal Article
ZDB-ID	2702241-9
ISSN	2050-7518 ; 2050-750X
ISSN (online)	2050-7518
ISSN	2050-750X
DOI	10.1039/d4tb00050a
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Article ; Online: Technical note: The design and validation of a multi-modality lung phantom.

Bowen, Donald L / Touchet, Tyler J / Maitland, Duncan J / McDougall, Mary P

Medical physics

2023 Volume 50, Issue 8, Page(s) 4809–4815

Abstract: Background: Clinically relevant models that enable certain tasks such as calibration of medical imaging devices or techniques, device validation, training healthcare professionals, and more are vital to research throughout the medical field and are ... ...

Abstract	Background: Clinically relevant models that enable certain tasks such as calibration of medical imaging devices or techniques, device validation, training healthcare professionals, and more are vital to research throughout the medical field and are referred to as phantoms. Phantoms range in complexity from a vile of water to complex designs that emulate in vivo properties. Purpose: Specific phantoms that model the lungs have focused on replication of tissue properties but lack replication of the anatomy. This limits the use across multiple imaging modalities and for device testing when anatomical considerations as well as tissue properties are needed. This work reports a lung phantom design utilizing materials that accurately mimic the ultrasound and magnetic resonance imaging (MRI) properties of in vivo lungs and includes relevant anatomical equivalence. Methods: The tissue mimicking materials were selected based on published studies of the materials, through qualitative comparisons of the materials with ultrasound imaging, and quantitative MRI relaxation values. A PVC ribcage was used as the structural support. The muscle/fat combined layer and the skin layer were constructed with various types of silicone with graphite powder added as a scattering agent where appropriate. Lung tissue was mimicked with silicone foam. The pleural layer was replicated by the interface between the muscle/fat layer and the lung tissue layer, requiring no additional material. Results: The design was validated by accurately mimicking the distinct tissue layers expected with in vivo lung ultrasound while maintaining tissue-mimicking relaxation values in MRI as compared to reported values. Comparisons between the muscle/fat material and in vivo muscle/fat tissue demonstrated a 1.9% difference in T1 relaxation and a 19.8% difference in T2 relaxation. Conclusions: Qualitative US and quantitative MRI analysis verified the proposed lung phantom design for accurate modeling of the human lungs.
MeSH term(s)	Humans ; Thorax ; Phantoms, Imaging ; Muscles ; Adipose Tissue ; Silicones
Chemical Substances	Silicones
Language	English
Publishing date	2023-05-18
Publishing country	United States
Document type	Journal Article
ZDB-ID	188780-4
ISSN	2473-4209 ; 0094-2405
ISSN (online)	2473-4209
ISSN	0094-2405
DOI	10.1002/mp.16462
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Article: Mechanical and Shape Memory Properties of Electrospun Polyurethane with Thiol-Ene Crosslinking.

Briggs, Sam / Herting, Scott / Fletcher, Grace / Gruenbaum, Rachel / Maitland, Duncan J

Nanomaterials (Basel, Switzerland)

2022 Volume 12, Issue 3

Abstract: The ability to treat complex medical issues often requires dynamic and versatile materials. Electrospinning is a fabrication technique which produces nano-/microfibers that can mimic the extracellular matrix of many biological tissues while shape memory ... ...

Abstract	The ability to treat complex medical issues often requires dynamic and versatile materials. Electrospinning is a fabrication technique which produces nano-/microfibers that can mimic the extracellular matrix of many biological tissues while shape memory polymers allow for geometric changes in devices upon implantation. Here, we present the fabrication of electrospun polyurethane which exhibits the shape memory effect. To improve the mechanical and shape memory properties of this system, we incorporate vinyl side chains in the polymer backbone which enable crosslinking via thiol-ene click chemistry post fabrication. We also discuss a novel technique to improve photoinitiated crosslinking for electrospun materials. A material with these properties is potentially beneficial for various medical applications, such as vascular anastomosis, and the characterization of this material will be valuable in directing those applications.
Language	English
Publishing date	2022-01-26
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2662255-5
ISSN	2079-4991
ISSN	2079-4991
DOI	10.3390/nano12030406
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Article ; Online: Macrophage activation in response to shape memory polymer foam-coated aneurysm occlusion devices.

Chau, Sarah M / Herting, Scott M / Noltensmeyer, Dillon A / Ahmed, Hamzah / Maitland, Duncan J / Raghavan, Shreya

Journal of biomedical materials research. Part B, Applied biomaterials

2022 Volume 110, Issue 7, Page(s) 1535–1544

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 ... ...

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.
MeSH term(s)	Animals ; Blood Vessel Prosthesis ; Embolization, Therapeutic ; Intracranial Aneurysm/surgery ; Macrophage Activation ; Platinum ; Rabbits ; Smart Materials
Chemical Substances	Smart Materials ; Platinum (49DFR088MY)
Language	English
Publishing date	2022-01-28
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
ZDB-ID	2099992-6
ISSN	1552-4981 ; 1552-4973 ; 0021-9304
ISSN (online)	1552-4981
ISSN	1552-4973 ; 0021-9304
DOI	10.1002/jbm.b.35015
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Article ; Online: Development of Biopsy Tract Sealants Based on Shape Memory Polymer Foams.

Touchet, Tyler J / Brinson, Braeden / Jones, McKenzie / Byju, Achu / Fletcher, Grace / Hasan, Sayyeda Marziya / Nash, Landon D / Maitland, Duncan J

Biomedical materials & devices (New York, N.Y.)

2023 Volume 1, Issue 2, Page(s) 853–860

Abstract: Lung biopsies are often used to aid in the diagnosis of cancers. However, the procedure carries the dual risk of air (pneumothorax) or blood (hemothorax) filling the pleural cavity, increasing the risk of a collapsed lung and chest intubation. This work ... ...

Abstract	Lung biopsies are often used to aid in the diagnosis of cancers. However, the procedure carries the dual risk of air (pneumothorax) or blood (hemothorax) filling the pleural cavity, increasing the risk of a collapsed lung and chest intubation. This work demonstrates the effectiveness of a polyurethane-based shape memory polymer foam as a biopsy tract sealant. The impact of diameter, length, pore size, and shape memory effect was evaluated to determine the ideal device design for tract sealing. Characterization in an
Language	English
Publishing date	2023-02-08
Publishing country	United States
Document type	Journal Article
ISSN	2731-4820
ISSN (online)	2731-4820
DOI	10.1007/s44174-023-00064-1
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Article ; Online: Fabrication and In Vivo Assessment of Oxidatively Responsive PolyHIPE Scaffolds for Use in Diabetic Orthopedic Applications.

Touchet, Tyler J / Horelica, Madeleine / Gruenbaum, Rachel / Lewy, Keith / Hines, Elizabeth / Stranahan, Lauren / Saunders, W Brian / Maitland, Duncan J

Macromolecular bioscience

2023 Volume 24, Issue 3, Page(s) e2300393

Abstract: Achieving surgical success in orthopedic patients with metabolic disease remains a substantial challenge. Diabetic patients exhibit a unique tissue microenvironment consisting of high levels of reactive oxygen species (ROS), which promotes osteoclastic ... ...

Abstract	Achieving surgical success in orthopedic patients with metabolic disease remains a substantial challenge. Diabetic patients exhibit a unique tissue microenvironment consisting of high levels of reactive oxygen species (ROS), which promotes osteoclastic activity and leads to decreased bone healing. Alternative solutions, such as synthetic grafts, incorporating progenitor cells or growth factors, can be costly and have processing constraints. Previously, the potential for thiol-methacrylate networks to sequester ROS while possessing tunable mechanical properties and degradation rates has been demonstrated. In this study, the ability to fabricate thiol-methacrylate interconnected porous scaffolds using emulsion templating to create monoliths with an average porosity of 97.0% is reported. The average pore sizes of the scaffolds range from 27 to 656 µm. The scaffolds can sequester pathologic levels of ROS via hydrogen peroxide consumption and are not impacted by sterilization. Subcutaneous implantation shows no signs of acute toxicity. Finally, in a 6-week bilateral calvarial defect model in Zucker diabetic fatty rats, ROS scaffolds increase new bone volume by 66% over sham defects. Histologic analysis identifies woven bone infiltration throughout the scaffold and neovascularization. Overall, this study suggests that porous thiol-methacrylate scaffolds may improve healing for bone grafting applications where high levels of ROS hinder bone growth.
MeSH term(s)	Humans ; Rats ; Animals ; Tissue Scaffolds ; Tissue Engineering ; Reactive Oxygen Species ; Rats, Zucker ; Porosity ; Diabetes Mellitus ; Methacrylates ; Sulfhydryl Compounds ; Polymers ; Styrenes
Chemical Substances	polyHIPE ; Reactive Oxygen Species ; Methacrylates ; Sulfhydryl Compounds ; Polymers ; Styrenes
Language	English
Publishing date	2023-11-14
Publishing country	Germany
Document type	Journal Article
ZDB-ID	2039130-4
ISSN	1616-5195 ; 1616-5187
ISSN (online)	1616-5195
ISSN	1616-5187
DOI	10.1002/mabi.202300393
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