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Objective: To report clinical features and outcomes of cats undergoing either stereotactic radiotherapy (SRT) or surgical excision for the treatment of intracranial meningioma., Animals: 61 client-owned cats., Methods: Medical records were retrospectively reviewed of cats with intracranial meningiomas that were treated with surgical removal and/or SRT between 2005 and 2017. Signalment, clinical signs, duration of clinical signs, diagnostic imaging reports, histopathology reports, treatment protocol, complications, recurrence or progression, and survival time were obtained from the medical record and through follow-up phone calls., Results: Of the 61 patients, 46 had surgery, 14 had SRT, and 1 had surgery followed by SRT for initial treatment. Significantly more cats that underwent surgery had peritreatment complications compared to the SRT group (P < .0001). Cats that received surgery initially had a significantly longer median survival time (MST) of 1,345 days compared to the MST of 339 days for the SRT cats (P = .002). Fourteen (30%) cats in the surgery group and 4 cats in the SRT group (28%) had MRI- or CT-confirmed tumor regrowth or new tumor growth (P = 1.00). Five cases that had SRT for subsequent recurrence had an MST of 700 days (range, 335 to 1,460 days) after the last treatment., Clinical Relevance: SRT proved to be a safe, alternative treatment option for feline patients with intracranial meningiomas; however, the survival times with surgery alone were significantly longer. SRT for the treatment of recurrence following initial surgery may show promising results.

The invasive, locally aggressive nature of feline injection-site sarcomas (FISSs) poses a unique challenge for surgeons to obtain complete margins with surgical excision. Optical coherence tomography (OCT), an imaging technology that uses light waves to generate real-time views of tissue architecture, provides an emerging solution to this dilemma by allowing fast, high-resolution scanning of surgical margins. The purpose of this study was to use OCT to assess surgical margins of FISS and to evaluate the diagnostic accuracy of OCT for detecting residual cancer using six evaluators of varying experience. Five FISSs were imaged with OCT to create a training set of OCT images that were compared with histopathology. Next, 25 FISSs were imaged with OCT prior to histopathology. Six evaluators of varying experience participated in a training session on OCT imaging after which each of the evaluators was given a dataset that included OCT images and videos to score on a scale from cancerous to non-cancerous. Diagnostic accuracy statistics were calculated. The overall sensitivity and specificity for classification of OCT images by evaluators were 78.9% and 77.6%, respectively. Correct classification rate of OCT images was associated with experience, while individual sensitivities and specificities had more variation between experience groups. This study demonstrates the ability of evaluators to correctly classify OCT images with overall low levels of experience and training and also illustrates areas where increased training can improve accuracy of evaluators in interpretation of OCT surgical margin images., (© 2021 John Wiley & Sons Ltd.)

Multi-material polymer scaffolds with multiscale pore architectures were characterized and tested with vascular and heart cells as part of a platform for replacing damaged heart muscle. Vascular and muscle scaffolds were constructed from a new material, poly(limonene thioether) (PLT32i), which met the design criteria of slow biodegradability, elastomeric mechanical properties, and facile processing. The vascular-parenchymal interface was a poly(glycerol sebacate) (PGS) porous membrane that met different criteria of rapid biodegradability, high oxygen permeance, and high porosity. A hierarchical architecture of primary (macroscale) and secondary (microscale) pores was created by casting the PLT32i prepolymer onto sintered spheres of poly(methyl methacrylate) (PMMA) within precisely patterned molds followed by photocuring, de-molding, and leaching out the PMMA. Pre-fabricated polymer templates were cellularized, assembled, and perfused in order to engineer spatially organized, contractile heart tissue. Structural and functional analyses showed that the primary pores guided heart cell alignment and enabled robust perfusion while the secondary pores increased heart cell retention and reduced polymer volume fraction.

A photocurable thiol-ene network polymer, poly(limonene thioether) (PLT32o), is synthesized, characterized, fabricated into tissue engineering scaffolds, and demonstrated in vitro and in vivo. Micromolded PLT32o grids exhibit compliant, elastomeric mechanical behavior similar to grids made of poly(glycerol sebacate) (PGS), an established biomaterial. Multilayered PL32o scaffolds with regular, geometrically defined pore architectures support heart cell seeding and culture in a manner similar to multilayered PGS scaffolds. Subcutaneous implantation of multilayered PLT32o scaffolds with cultured heart cells provides long-term 3D structural support and retains the exogenous cells, whereas PGS scaffolds lose both their structural integrity and the exogenous cells over 31 d in vivo. PLT32o membrane implants retain their dry mass, whereas PGS implants lose 70 percent of their dry mass by day 31. Macrophages are initially recruited to PLT32o and PGS membrane implants but are no longer present by day 31. Facile synthesis and processing in combination with the capability to support heart cells in vitro and in vivo suggest that PLT32o can offer advantages for tissue engineering applications where prolonged in vivo maintenance of 3D structural integrity and elastomeric mechanical behavior are required., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This retrospective report describes perioperative and short-term postoperative complications of gastrointestinal biopsies obtained via a laparoscopic-assisted technique compared with laparotomy in a population of 60 client-owned dogs and cats with naturally occurring gastrointestinal disease. The medical records were examined for patients that underwent surgery for diagnostic gastrointestinal biopsies. Data were collected regarding perioperative complications such as hypotension, hypercarbia, and hypoxemia, and short-term postoperative complications including seroma and incisional infection/inflammation. The perioperative complication rate was 17.6% for the laparoscopically assisted group and 16.6% for the control group. The short-term postoperative complication rate was 5.9% for the laparoscopically assisted group and 0% for the control group. There was a 0% rate of intestinal dehiscence. There were no statistically significant differences in complication rates between the 2 groups, showing that laparoscopic-assisted gastrointestinal biopsies can be performed with acceptable perioperative and short-term postoperative complication rates.

Polyurethane shape memory polymers (SMPs) with tunable thermomechanical properties and advanced processing capabilities are synthesized, characterized, and implemented in the design of a microactuator medical device prototype. The ability to manipulate glass transition temperature (Tg ) and crosslink density in low-molecular weight aliphatic thermoplastic polyurethane SMPs is demonstrated using a synthetic approach that employs UV catalyzed thiol-ene "click" reactions to achieve postpolymerization crosslinking. Polyurethanes containing varying C=C functionalization are synthesized, solution blended with polythiol crosslinking agents and photoinitiator and subjected to UV irradiation, and the effects of number of synthetic parameters on crosslink density are reported. Thermomechanical properties are highly tunable, including glass transitions tailorable between 30 and 105 °C and rubbery moduli tailorable between 0.4 and 20 MPa. This new SMP system exhibits high toughness for many formulations, especially in the case of low crosslink density materials, for which toughness exceeds 90 MJ m(-3) at select straining temperatures. To demonstrate the advanced processing capability and synthetic versatility of this new SMP system, a laser-actuated SMP microgripper device for minimally invasive delivery of endovascular devices is fabricated, shown to exhibit an average gripping force of 1.43 ± 0.37 N and successfully deployed in an in vitro experimental setup under simulated physiological conditions., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Scalable units for building cardiac tissue are fabricated from biodegradable elastomeric polymers by pairwise stacking of heart-cell scaffolds with sinusoidal internal pore architectures and dedicated perfusable microvessels with rapidly degrading porous interfaces in a parallel flow configuration. This platform supports viable heart cells in vitro and, if validated in vivo, may aid in the regenerative repair of vascularized tissues., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Polycarbonate networks derived from the natural product quinic acid that can potentially return to their natural building blocks upon hydrolytic degradation are described herein. Solvent-free thiol-ene chemistry was utilized in the copolymerization of tris(alloc)quinic acid and a variety of multifunctional thiol monomers to obtain poly(thioether-co-carbonate) networks with a wide range of achievable thermomechanical properties including glass transition temperatures from -18 to +65 °C and rubbery moduli from 3.8 to 20 MPa. The network containing 1,2-ethanedithiol expressed an average toughness at 25 and 63 °C of 1.08 and 2.35 MJ/m(3), respectively, and an order-of-magnitude increase in the average toughness at 37 °C of 15.56 MJ/m(3).

Nanocomposite polymers are prepared using a new sustainable materials synthesis process in which d-Limonene functions simultaneously both as a solvent for recycling polystyrene (PS) waste and as a monomer that undergoes UV-catalyzed thiol-ene polymerization reactions with polythiol comonomers to afford polymeric products composed of precipitated PS phases dispersed throughout elastomeric poly(thioether) networks. These blended networks exhibit mechanical properties that greatly exceed those of either polystyrene or the poly(thioether) network homopolymers alone., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The purpose of this study was to identify large-breed dogs with intervertebral disc disease (IVDD) in the upper thoracic region (thoracic vertebrae 1-9 [T1-T9]). Medical records of all dogs that were diagnosed with IVDD on MRI between February 2008 and September 2011 were reviewed. Of 723 dogs diagnosed with IVDD based on MRI, 527 (72.9%) were small-breed dogs. There were 21 (10.7%) large-breed dogs with IVDD in the T1-T9 region, whereas no small-breed dogs were identified with lesions in that region. The most common upper thoracic lesion sites were T2-T3 (33.3%) and T4-T5 (25.9%). The majority of dogs with T1-T9 lesions were German shepherd dogs (52.4%). Larger, older dogs were more likely to have T1-T9 lesions and more likely to have multiple regions with IVDD, in particular German shepherd dogs (35.1%). Dogs with T1-T9 IVDD were more likely to have IVDD in another region (66.7%). All large-breed dogs presenting with T3-L3 myelopathy should have diagnostic imaging performed of their entire thoracic and lumbar spine.

Purpose: To evaluate the feasibility of utilizing a system of SMP acrylates for a thrombectomy device by determining an optimal crosslink density that provides both adequate recovery stress for blood clot removal and sufficient strain capacity to enable catheter delivery., Methods: Four thermoset acrylic copolymers containing benzylmethacrylate (BzMA) and bisphenol A ethoxylate diacrylate (Mn~512, BPA) were designed with differing thermomechanical properties. Finite element analysis (FEA) was performed to ensure that the materials were able to undergo the strains imposed by crimping, and fabricated devices were subjected to force-monitored crimping, constrained recovery, and bench-top thrombectomy., Results: Devices with 25 and 35 mole% BPA exhibited the highest recovery stress and the highest brittle response as they broke upon constrained recovery. On the contrary, the 15 mole % BPA devices endured all testing and their recovery stress (5 kPa) enabled successful bench-top thrombectomy in 2/3 times, compared to 0/3 for the devices with the lowest BPA content., Conclusion: While the 15 mole% BPA devices provided the best trade-off between device integrity and performance, other SMP systems that offer recovery stresses above 5 kPa without increasing brittleness to the point of causing device failure would be more suitable for this application.

Neural interfaces provide an electrical connection between computers and the nervous system: current penetrating devices are orders-of-magnitude stiffer than surrounding tissue. In this work, recent efforts in softening electronics and utilize thiol-ene and thiol-epoxy "click" reactions are built upon to incorporate fluid-sensitive hydrogen bonding into smart substrates for high electrode density neural interfaces. The modulus of these substrates drops more than two orders of magnitude in response to physiological conditions, despite fluid uptake of less than 6%, and can be tuned by the covalent crosslink density and degree of hydrogen bonding in the polymer network. Intracortical and intrafascicular electrode arrays are fabricated and characterized with impedance spectroscopy and cyclic voltammetry., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The synthetic design and thermomechanical characterization of shape memory polymers (SMPs) built from a new polyurethane chemistry that enables facile, bulk and tunable cross-linking of low-molecular weight thermoplastics by electron beam irradiation is reported in this study. SMPs exhibit stimuli-induced geometry changes and are being proposed for applications in numerous fields. We have previously reported a polyurethane SMP system that exhibits the complex processing capabilities of thermoplastic polymers and the mechanical robustness and tunability of thermomechanical properties that are often characteristic of thermoset materials. These previously reported polyurethanes suffer practically because the thermoplastic molecular weights needed to achieve target cross-link densities severely limit high-throughput thermoplastic processing and because thermally unstable radiation-sensitizing additives must be used to achieve high enough cross-link densities to enable desired tunable shape memory behavior. In this study, we demonstrate the ability to manipulate cross-link density in low-molecular weight aliphatic thermoplastic polyurethane SMPs ( M w as low as ~1.5 kDa) without radiation-sensitizing additives by incorporating specific structural motifs into the thermoplastic polymer side chains that we hypothesized would significantly enhance susceptibility to e-beam cross-linking. A custom diol monomer was first synthesized and then implemented in the synthesis of neat thermoplastic polyurethane SMPs that were irradiated at doses ranging from 1 to 500 kGy. Dynamic mechanical analysis (DMA) demonstrated rubbery moduli to be tailorable between 0.1 and 55 MPa, and both DMA and sol/gel analysis results provided fundamental insight into our hypothesized mechanism of electron beam cross-linking, which enables controllable bulk cross-linking to be achieved in highly processable, low-molecular weight thermoplastic shape memory polymers without sensitizing additives.

Novel electron beam crosslinked polyurethane shape memory polymers with advanced processing capabilities and tunable thermomechanical properties have been synthesized and characterized. We demonstrate the ability to manipulate crosslink density in order to finely tune rubbery modulus, strain capacity, ultimate tensile strength, recovery stress, and glass transition temperature. This objective is accomplished for the first time in a low-molecular-weight polymer system through the precise engineering of thermoplastic resin precursors suitable for mass thermoplastic processing. Neurovascular stent prototypes were fabricated by dip-coating and laser machining to demonstrate processability.

Porous shape memory polymers (SMPs) include foams, scaffolds, meshes, and other polymeric substrates that possess porous three-dimensional macrostructures. Porous SMPs exhibit active structural and volumetric transformations and have driven investigations in fields ranging from biomedical engineering to aerospace engineering to the clothing industry. The present review article examines recent developments in porous SMPs, with focus given to structural and chemical classification, methods of characterization, and applications. We conclude that the current body of literature presents porous SMPs as highly interesting smart materials with potential for industrial use.

The effects of free radical inhibitor on the electron beam crosslinking and thermal processing stabilization of novel radiation crosslinkable polyurethane shape memory polymers (SMPs) blended with acrylic radiation sensitizers have been determined. The SMPs in this study possess novel processing capabilities-that is, the ability to be melt processed into complex geometries as thermoplastics and crosslinked in a secondary step using electron beam irradiation. To increase susceptibility to radiation crosslinking, the radiation sensitizer pentaerythritol triacrylate (PETA) was solution blended with thermoplastic polyurethane SMPs made from 2-butene-1,4-diol and trimethylhexamethylene diisocyanate (TMHDI). Because thermoplastic melt processing methods such as injection molding are often carried out at elevated temperatures, sensitizer thermal instability is a major processing concern. Free radical inhibitor can be added to provide thermal stabilization; however, inhibitor can also undesirably inhibit radiation crosslinking. In this study, we quantified both the thermal stabilization and radiation crosslinking inhibition effects of the inhibitor 1,4-benzoquinone (BQ) on polyurethane SMPs blended with PETA. Sol/gel analysis of irradiated samples showed that the inhibitor had little to no inverse effects on gel fraction at concentrations of 0-10,000 ppm, and dynamic mechanical analysis showed only a slight negative correlation between BQ composition and rubbery modulus. The 1,4-benzoquinone was also highly effective in thermally stabilizing the acrylic sensitizers. The polymer blends could be heated to 150°C for up to five hours or to 125°C for up to 24 hours if stabilized with 10,000 ppm BQ and could also be heated to 125°C for up to 5 hours if stabilized with 1000 ppm BQ without sensitizer reaction occurring. We believe this study provides significant insight into methods for manipulation of the competing mechanisms of radiation crosslinking and thermal stabilization of radiation sensitizers, thereby facilitating further development of radiation crosslinkable thermoplastic SMPs.

Planar electronics processing methods have enabled neural interfaces to become more precise and deliver more information. However, this processing paradigm is inherently 2D and rigid. The resulting mechanical and geometrical mismatch at the biotic-abiotic interface can elicit an immune response that prevents effective stimulation. In this work, a thiol-ene/acrylate shape memory polymer is utilized to create 3D softening substrates for stimulation electrodes. This substrate system is shown to soften in vivo from more than 600 to 6 MPa. A nerve cuff electrode that coils around the vagus nerve in a rat and that drives neural activity is demonstrated.

Triple shape memory polymers (TSMPs) are a growing subset of a class of smart materials known as shape memory polymers, which are capable of changing shape and stiffness in response to a stimulus. A TSMP can change shapes twice and can fix two metastable shapes in addition to its permanent shape. In this work, a novel TSMP system comprised of both permanent covalent cross-links and supramolecular hydrogen bonding cross-links has been synthesized via a one-pot method. Triple shape properties arise from the combination of the glass transition of (meth)acrylate copolymers and the dissociation of self-complementary hydrogen bonding moieties, enabling broad and independent control of both glass transition temperature (T(g)) and cross-link density. Specifically, ureidopyrimidone methacrylate and a novel monomer, ureidopyrimidone acrylate, were copolymerized with various alkyl acrylates and bisphenol A ethoxylate diacrylate. Control of T(g) from 0 to 60 °C is demonstrated: concentration of hydrogen bonding moieties is varied from 0 to 40 wt %; concentration of the diacrylate is varied from 0 to 30 wt %. Toughness ranges from 0.06 to 0.14 MPa and is found to peak near 20 wt % of the supramolecular cross-linker. A widely tunable class of amorphous triple-shape memory polymers has been developed and characterized through dynamic and quasi-static thermomechanical testing to gain insights into the dynamics of supramolecular networks.

The effect of moisture absorption on the glass transition temperature (T(g)) and stress/strain behavior of network polyurethane shape memory polymer (SMP) foams has been investigated. With our ultimate goal of engineering polyurethane SMP foams for use in blood contacting environments, we have investigated the effects of moisture exposure on the physical properties of polyurethane foams. To our best knowledge, this study is the first to investigate the effects of moisture absorption at varying humidity levels (non-immersion and immersion) on the physical properties of polyurethane SMP foams. The SMP foams were exposed to differing humidity levels for varying lengths of time, and they exhibited a maximum water uptake of 8.0% (by mass) after exposure to 100% relative humidity for 96 h. Differential scanning calorimetry results demonstrated that water absorption significantly decreased the T(g) of the foam, with a maximum water uptake shifting the T(g) from 67 °C to 5 °C. Samples that were immersed in water for 96 h and immediately subjected to tensile testing exhibited 100% increases in failure strains and 500% decreases in failure stresses; however, in all cases of time and humidity exposure, the plasticization effect was reversible upon placing moisture-saturated samples in 40% humidity environments for 24 h.

Novel urethane shape-memory polymers (SMPs) of significant industrial relevance have been synthesized and characterized. Chemically crosslinked SMPs have traditionally been made in a one-step polymerization of monomers and crosslinking agents. However, these new post-polymerization crosslinked SMPs can be processed into complex shapes by thermoplastic manufacturing methods and later crosslinked by heat exposure or by electron beam irradiation. Several series of linear, olefinic urethane polymers were made from 2-butene-1,4-diol, other saturated diols, and various aliphatic diisocyanates. These thermoplastics were melt-processed into desired geometries and thermally crosslinked at 200°C or radiation crosslinked at 50 kGy. The SMPs were characterized by solvent swelling and extraction, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile testing, and qualitative shape-recovery analysis. Swelling and DMA results provided concrete evidence of chemical crosslinking, and further characterization revealed that the urethanes had outstanding mechanical properties. Key properties include tailorable transitions between 25 and 80°C, tailorable rubbery moduli between 0.2 and 4.2 MPa, recoverable strains approaching 100%, failure strains of over 500% at T(g), and qualitative shape-recovery times of less than 12 seconds at body temperature (37°C). Because of its outstanding thermo-mechanical properties, one polyurethane was selected for implementation in the design of a complex medical device. These post-polymerization crosslinked urethane SMPs are an industrially relevant class of highly processable shape-memory materials.

Objective: To evaluate hip joint laxity in 10 breeds of dogs via 2 radiographic techniques., Animals: 500 clinically normal dogs., Design: Prospective study., Procedure: Radiographs obtained via routine hip joint evaluations performed in sedated dogs of 10 popular breeds were randomly selected from a database. Measurements of distraction index (DI) and hip-extended index (HEI) on 1 hip joint radiograph randomly chosen from each dog were made., Results: Mean age of dogs was 20.7 months. Mean HEI was 0.17 (range, 0.0 to 0.72) and mean DI was 0.44 (range, 0.07 to 0.96). Borzois had uniformly tight hip joints as judged by use of both methods and were considered the gold standard by which hip joint laxity was judged (all Borzois had DI < or = 0.32). Overall, DI was significantly greater than HEI. Within each breed, mean DI was always greater than mean HEI. Significant differences were detected among breeds for HEI; however, compared with DI, the magnitude of differences among breeds was less., Conclusions and Clinical Relevance: Distraction radiography detected the greatest range and magnitude of passive hip laxity in the 10 breeds of dogs. The difference in values between breeds known to have high prevalence of canine hip dysplasia and those in Borzois was greater for DI than for HEI. Breeds must be evaluated individually because of inherent differences in hip joint laxity.