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1.
Eur J Med Res ; 26(1): 121, 2021 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-34641963

RESUMO

BACKGROUND: Percutaneous coronary interventions (PCI) of bifurcation stenoses are both complex and challenging. Stenting strategies share that the stents' side cells must be carefully explored and appropriately prepared using balloons or stents. So far, stent manufacturers have not provided any information regarding side-branch expansion capacity of their stent platforms. AIMS: Given that drug-eluting stent (DES) information regarding their mechanical capacity of side-branch expansion is not available, we aimed to evaluate contemporary DES (Orsiro, BIOTRONIK AG; Xience Sierra, Abbott Vascular; Resolute Integrity, Medtronic; Promus Premier Select, Boston Scientific; Supraflex Cruz, Sahajan and Medical Technologies) by their side-branch expansion behavior using in vitro bench testing. METHODS: In this in vitro study, we analyzed five commercially available DES (diameter 3.0 mm), measuring their side-branch expansion following inflation of different high-pressure non-compliant (NC) balloons (balloon diameter: 2.00-4.00 mm), thereby revealing the morphological characteristics of their side-branch expansion capacities. RESULTS: We demonstrated that all tested contemporary DES platforms could withstand large single-cell deformations, up to 4.0 mm. As seen in our side-branch experiments, DES designs consisting of only two connectors between strut rings did not only result in huge cell areas, but also in larger cell diameters following side-branch expansion compared with DES designs using three or more connectors. Furthermore, the stent cell diameter attained was below the balloon diameter at normal pressure. CONCLUSIONS: We recommend that the expansion capacity of side-branches should be considered in stent selection for bifurcation interventions.

2.
Materials (Basel) ; 13(19)2020 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-32998325

RESUMO

Supplementary cementitious materials (SCM) can reduce the total amount of Portland cement clinker in concrete production. Rice husk ashes (RHA) can be converted from an agricultural by-product to a high-performance concrete constituent due to a high amount of reactive silica with pozzolanic properties if they are burnt under controlled conditions. The way and duration of combustion, the cooling process as well as the temperature have an effect on the silica form and thus, the chemical and physical performance of the RHA. Various studies on the best combustion technique have been published to investigate the ideal combustion techniques. Yet, the process mostly took place under laboratory conditions. Investigating the difference between the performance of RHA produced in a rural environment and laboratory conditions is useful for the assessment and future enhancement of RHA production, and its application both as building material, for example in rural areas where it is sourced in large quantities, and as additive for high performance concrete. Thus, the paper presents a comparison between RHA produced under rudimentary conditions in a self-made furnace in the rural Bagamoyo, Tanzania and under controlled laboratory conditions at the Technical University of Munich, Germany, with different combustion methods and temperatures. In a second step, RHA was ground to reach particle size distributions comparable to cement. In a third step, cement pastes were prepared with 10%, 20% and 40% of cement replacement, and compared to the performance of plain and fly ash blended cement pastes. The results show that controlled burning conditions around 650 °C lead to high reactivity of silica and, therefore, to good performance as SCM. However, also the RHA burnt under less controlled conditions in the field provided reasonably good properties, if the process took place with proper burning parameters and adequate grinding. The knowledge can be implemented in the field to improve the final RHA performance as SCM in concrete.

3.
Eur J Med Res ; 25(1): 28, 2020 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-32727596

RESUMO

BACKGROUND: Percutaneous coronary intervention is among the most common therapeutic interventions in cardiology. This procedure may, however, be associated with a rare, though life-threatening complication: acute coronary perforation (CP). CP is primarily treated using covered stents, which are made of bare metal stents with a polytetrafluoroethylene (PTFE) or polyurethane coating. These stents' major limitations include higher rates of thrombus formation and restenosis. Hence, there is a still unmet need for new stents regarding their design and composition. Or, to test new covered stent designs, the rabbit iliac artery has become the best-established animal model. This study sought to present a preclinical animal approach designed to test covered stents that are utilized following vessel perforation. METHODS: The animal experiments were performed using New Zealand white rabbits, each weighting 3.5-4.5 kg. The animal models described herein relied on the three most common clinical causes for CP, such as guidewire-induced, balloon catheter bursting, and device oversizing. Moreover, the sealing capacity of covered stent grafts was assessed for each of these models by means of angiography. RESULTS: We herein report a rabbit iliac artery perforation model using three different types of vessel perforation that closely mimic the clinical setting, such as guidewire-induced, balloon catheter rupture, and device oversizing. Using the same rabbit iliac perforation model, we additionally assessed the sealing capacity of a covered stent graft for each model. CONCLUSIONS: The novel rabbit iliac artery perforation models, as described in this report, represent promising animal testing approaches. While their setting is very similar to the real-life context encountered in humans, all three models are based on an animal model that is ideally suited for evaluating the sealing capacity and performance of new medical devices for humans.


Assuntos
Doença das Coronárias/terapia , Modelos Animais de Doenças , Traumatismos Cardíacos/prevenção & controle , Intervenção Coronária Percutânea/efeitos adversos , Stents , Animais , Traumatismos Cardíacos/etiologia , Coelhos
4.
Materials (Basel) ; 13(7)2020 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-32218269

RESUMO

The interaction of different charged polymers, namely anionic polycarboxylate superplasticizer (PCE) and neutral polyethylene glycol (PEG) with potassium ions, and their effect on the yield stress of highly concentrated glass bead suspension (GBS), were studied under different concentrations of potassium ions ([K+]). It was found that, compared to the neutral PEG, the negatively charged PCE can be adsorbed on glass beads (GB), and then decreases the yield stress of GBS. The increasing concentration of free polymer in the interstitial liquid phase with the increased polymer dosage leads to the higher yield stress of GBS, which may be caused by the higher depletion force. In addition, this effect is also related to the charge density of the polymer and the [K+] in the solution. Along with the increase in [K+], the yield stress of GBS increases significantly with the addition of PCE, but this cannot be observed with PEG, which indicates that potassium ions can interact with negatively charged PCE instead of the neutral PEG. At last, the interparticle forces between two single GB with adsorbed PCE in solutions containing [K+] and PCE were measured by colloidal probe atomic force microscopy to better understand the interaction of the charged polymer with counterions.

5.
Phys Rev E ; 100(4-1): 043116, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31771024

RESUMO

We revisit the problem of how energy transfer through the turbulent cascade operates in compressible hydrodynamic turbulence. In general, there is no conservative compressible cascade since the kinetic and internal energy reservoirs can exchange energy through pressure dilatation. Moreover, statistically stationary turbulence at high Mach number can only be maintained in nearly isothermal gas, i.e., if excess heat produced by shock compression and kinetic energy dissipation is continuously removed from the system. We mimic this process by a linear cooling term in numerical simulations of turbulence driven by stochastic forcing. This allows us to investigate turbulence statistics for a broad range of Mach numbers. We compute the rate of change of kinetic and internal energy in wave-number shells caused by advective, compressive, and pressure dilatation effects and constrain power-law fits to compressible turbulence energy spectra to a range of wave numbers in which the total energy transfer is close to zero. The resulting scaling exponents are significantly affected by the forcing. Depending on the root mean square Mach number, we find a nearly constant advective component of the cross-scale flux of kinetic energy at intermediate wave numbers for particular mixtures of solenoidal and compressive modes in the forcing. This suggests the existence of a natural, Mach number dependent mixture of forcing modes. Our findings also support an advection-dominated regime at high Mach numbers with specific scaling exponents (Burgers scaling for the pure velocity fluctuation u and Kolmogorov scaling for the mass-weighted variable v=ρ^{1/3}u).

6.
J Endovasc Ther ; 26(4): 578-582, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31060430

RESUMO

Purpose: To evaluate a MicroNet-covered stent designed for the carotid artery with the new ability to adjust to different vessel diameters. Materials and Methods: Thirty consecutive patients (mean age 72.1±7.7 years; 26 men) with symptomatic stenosis (86.3%±6.4%) of the internal carotid artery were treated with the new self-adjusting nitinol stent, which has a self-expanding, open-cell design covered by an outer conformable layer (MicroNet). The only stent used was the "One-Size-Fits-All" CGuard stent with lengths of 30 or 40 mm. In bench testing, the chronic outward force of the One-Size-Fits-All stent was determined with a segmented head radial force test device. The stent was deployed directly into the test device at a diameter of 5.0 mm, and the chronic outward force was measured up to 10.0 mm, the maximum expansion of the stent. Results: The stent was successfully implanted in all 30 patients without periprocedural complications, including no neurological events within 30 days. The chronic outward force normalized by stent length demonstrated a near-equivalent radial force outcome: The stent displayed only a minor difference between the minimal radial force at 9.0 mm (0.195 N/mm) and the maximal radial force at 5.5 mm (0.330 N/mm). Conclusion: The new self-adjusting, MicroNet-covered stent has high conformability combined with an almost equivalent radial force at expansion diameters ranging from 5.5 to 9.0 mm. The first clinical results demonstrate that the new One-Size-Fits-All stent can be safely implanted in internal carotid arteries with reference diameters within this range.


Assuntos
Angioplastia com Balão/instrumentação , Artéria Carótida Interna , Estenose das Carótidas/terapia , Stents Metálicos Autoexpansíveis , Idoso , Ligas , Angioplastia com Balão/efeitos adversos , Artéria Carótida Interna/diagnóstico por imagem , Artéria Carótida Interna/fisiopatologia , Estenose das Carótidas/complicações , Estenose das Carótidas/diagnóstico por imagem , Estenose das Carótidas/fisiopatologia , Feminino , Hemodinâmica , Humanos , Masculino , Pessoa de Meia-Idade , Desenho de Prótese , Estresse Mecânico , Fatores de Tempo , Resultado do Tratamento
7.
J Mech Behav Biomed Mater ; 91: 174-181, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30583263

RESUMO

Resorbable magnesium scaffolds are used for the treatment of atherosclerotic coronary vascular disease and furthermore, for vascular restoration therapy. Recently, the first-in-man clinical studies with Magmaris showed promising results regarding the target lesion failure as well as vasomotion properties after 12 and 24 month. The consistency of in vivo degraded magnesium alloys in a cardiovascular environment is qualitatively described in literature, but only little has been disclosed about the actual change in mechanical properties and the behavior of the magnesium alloy degradation products. In the present study, uncoated magnesium scaffolds 3.0 × 20 mm were implanted in coronary arteries of two healthy Goetinnger mini-swine. The scaffolds were explanted to evaluate the mechanical properties of the degraded magnesium scaffolds after 180 days in vivo. Ex vivo sample preparation and test conditions were adapted to a customized compression test setup which was developed to investigate the micro-scale scaffold fragments (width 225 ±â€¯75 µm, thickness 150 µm). As reference bare undegraded magnesium scaffold fragments were tested. Mechanical parameters relating to force as a function of displacement were determined for both sample groups. The undegraded samples showed no fracturing at the maximum applied force of 8 N, whereas the in vivo degraded test samples showed forces of 0.411 ±â€¯0.197 N at the first fracturing and a maximum force of 0.956 ±â€¯0.525 N. The deformation work, calculated as area beneath the force-displacement curve, of the in vivo degraded test samples was reduced by approximately 87-88% compared to the undegraded samples (5.20 mN mm and 40.79 mN mm, both at 7.5% deformation). The indication for a complete loss of structural integrity through a reduction of mechanical properties after a certain degradation time increases the chance to restore vascular function and physiological vasomotion in the stented vessel compartment.


Assuntos
Implantes Absorvíveis , Magnésio/química , Magnésio/metabolismo , Fenômenos Mecânicos , Animais , Vasos Coronários , Teste de Materiais , Suínos
8.
Biosci Rep ; 38(4)2018 08 31.
Artigo em Inglês | MEDLINE | ID: mdl-30061178

RESUMO

To prevent implant failure due to fibrosis is a major objective in glaucoma research. The present study investigated the antifibrotic effects of paclitaxel (PTX), caffeic acid phenethyl ester (CAPE), and pirfenidone (PFD) coated microstent test specimens in a rat model. Test specimens based on a biodegradable blend of poly(4-hydroxybutyrate) biopolymer and atactic poly(3-hydroxybutyrate) (at.P(3HB)) were manufactured, equipped with local drug delivery (LDD) coatings, and implanted in the subcutaneous white fat depot. Postoperatively, test specimens were explanted and analyzed for residual drug content. Fat depots including the test specimens were histologically analyzed. In vitro drug release studies revealed an initial burst for LDD devices. In vivo, slow drug release of PTX was found, whereas it already completed 1 week postoperatively for CAPE and PFD LDD devices. Histological examinations revealed a massive cell infiltration in the periphery of the test specimens. Compact fibrotic capsules around the LDD devices were detectable at 4-36 weeks and least pronounced around PFD-coated specimens. Capsules stained positive for extracellular matrix (ECM) components. The presented model offers possibilities to investigate release kinetics and the antifibrotic potential of drugs in vivo as well as the identification of more effective agents for a novel generation of drug-eluting glaucoma microstents.


Assuntos
Ácidos Cafeicos/administração & dosagem , Sistemas de Liberação de Medicamentos/instrumentação , Stents Farmacológicos , Paclitaxel/administração & dosagem , Álcool Feniletílico/análogos & derivados , Piridonas/administração & dosagem , Animais , Ácidos Cafeicos/farmacocinética , Ácidos Cafeicos/uso terapêutico , Fibrose , Glaucoma/terapia , Masculino , Paclitaxel/farmacocinética , Paclitaxel/uso terapêutico , Álcool Feniletílico/administração & dosagem , Álcool Feniletílico/farmacocinética , Álcool Feniletílico/uso terapêutico , Piridonas/farmacocinética , Piridonas/uso terapêutico , Ratos , Ratos Wistar
9.
Eur J Med Res ; 23(1): 2, 2018 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-29310720

RESUMO

BACKGROUND: Drug-eluting stents (DES) compared to bare metal stents (BMS) have shown superior clinical performance, but are considered less suitable in complex cases. Most studies do not distinguish between DES and BMS with respect to their mechanical performance. The objective was to obtain mechanical parameters for direct comparison of BMS and DES. METHODS: In vitro bench tests evaluated crimped stent profiles, crossability in stenosis models, elastic recoil, bending stiffness (crimped and expanded), and scaffolding properties. The study included five pairs of BMS and DES each with the same stent platforms (all n = 5; PRO-Kinetic Energy, Orsiro: BIOTRONIK AG, Bülach, Switzerland; MULTI-LINK 8, XIENCE Xpedition: Abbott Vascular, Temecula, CA; REBEL Monorail, Promus PREMIER, Boston Scientific, Marlborough, MA; Integrity, Resolute Integrity, Medtronic, Minneapolis, MN; Kaname, Ultimaster: Terumo Corporation, Tokyo, Japan). Statistical analysis used pooled variance t tests for pairwise comparison of BMS with DES. RESULTS: Crimped profiles in BMS groups ranged from 0.97 ± 0.01 mm (PRO-Kinetic Energy) to 1.13 ± 0.01 mm (Kaname) and in DES groups from 1.02 ± 0.01 mm (Orsiro) to 1.13 ± 0.01 mm (Ultimaster). Crossability was best for low profile stent systems. Elastic recoil ranged from 4.07 ± 0.22% (Orsiro) to 5.87 ± 0.54% (REBEL Monorail) including both BMS and DES. The bending stiffness of crimped and expanded stents showed no systematic differences between BMS and DES neither did the scaffolding. CONCLUSIONS: Based on in vitro measurements BMS appear superior to DES in some aspects of mechanical performance, yet the differences are small and not class uniform. The data provide assistance in selecting the optimal system for treatment and assessment of new generations of bioresorbable scaffolds. TRIAL REGISTRATION: not applicable.


Assuntos
Stents Farmacológicos/normas , Stents Metálicos Autoexpansíveis/normas , Stents Farmacológicos/efeitos adversos , Fenômenos Mecânicos , Stents Metálicos Autoexpansíveis/efeitos adversos
10.
Biomed Microdevices ; 19(4): 78, 2017 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-28844120

RESUMO

Within this paper we analyzed the technical feasibility of a novel microstent for glaucoma therapy. For lowering of intraocular pressure, the flexible polyurethane (PUR) implant is designed to drain aqueous humour from the anterior chamber of the eye into subconjunctival, or alternatively suprachoroidal, space. The microstent includes a biodegradable, flow resisting polymer membrane serving as temporary flow resistance for the prevention of early postoperative hypotony. A biodegradable local drug delivery (LDD)-device was designed to prevent fibrous encapsulation. Biodegradable components were made of flexible, nonwoven membranes of Poly(4-hydroxybutyrate) (P(4HB)). Polymer samples and microstent prototypes were manufactured by means of dip coating, electrospinning and femtosecond-laser micromachining and characterized in vitro with regard to structural and fluid mechanical properties, degradation behavior and drug release. Bending stiffness of PUR-tubing (62.53 ± 7.57 mN mm2) is comparable to conventional glaucoma drainage devices in a tube-plate design. Microstent prototypes yield a flow resistance of 2.4 ± 0.6 mmHg/µl min-1 which is close to the aspired value corresponding to physiological pressure (15 mmHg) and aqueous humour flow (2 µl min-1) conditions inside the eye. Degradation of electrospun P(4HB) specimens was found to be almost completely finished after six months in vitro. Within this time frame, flow capacity of the microstent increases, which is beneficial to compensate potentially increasing flow resistance of fibrous tissue in vivo. Fast drug release of the LDD-device was found. One microstent prototype was implanted into a porcine eye ex vivo. Future preclinical studies will allow further information about Microstent performance.


Assuntos
Implantes Absorvíveis , Implantes de Medicamento , Glaucoma/terapia , Teste de Materiais , Poliésteres , Stents , Animais , Implantes de Medicamento/química , Implantes de Medicamento/farmacologia , Glaucoma/metabolismo , Glaucoma/fisiopatologia , Humanos , Poliésteres/química , Poliésteres/farmacologia , Suínos
11.
Phys Rev E ; 95(3-1): 033206, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28415265

RESUMO

Large-eddy simulations (LES) are a powerful tool in understanding processes that are inaccessible by direct simulations due to their complexity, for example, in the highly turbulent regime. However, their accuracy and success depends on a proper subgrid-scale (SGS) model that accounts for the unresolved scales in the simulation. We evaluate the applicability of two traditional SGS models, namely the eddy-viscosity (EV) and the scale-similarity (SS) models, and one recently proposed nonlinear (NL) SGS model in the realm of compressible magnetohydrodynamic (MHD) turbulence. Using 209 simulations of decaying, supersonic (initial sonic Mach number M_{s}≈3) MHD turbulence with a shock-capturing scheme and varying resolution, SGS model, and filter, we analyze the ensemble statistics of kinetic and magnetic energy spectra and structure functions. Furthermore, we compare the temporal evolution of lower- and higher-order statistical moments of the spatial distributions of kinetic and magnetic energy, vorticity, current density, and dilatation magnitudes. We find no statistical influence on the evolution of the flow by any model if grid-scale quantities are used to calculate SGS contributions. In addition, the SS models, which employ an explicit filter, have no impact in general. On the contrary, both the EV and NL models change the statistics if an explicit filter is used. For example, they slightly increase the dissipation on the smallest scales. We demonstrate that the nonlinear model improves higher-order statistics already with a small explicit filter, i.e., a three-point stencil. The results of, e.g., the structure functions or the skewness and kurtosis of the current density distribution are closer to the ones obtained from simulations at higher resolution. In addition, no additional regularization to stabilize the model is required. We conclude that the nonlinear model with a small explicit filter is suitable for application in more complex scenarios when higher-order statistics are important.

12.
Biomed Tech (Berl) ; 62(4): 349-355, 2017 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-28076296

RESUMO

Embolic protection devices were developed to reduce the risk of stroke during carotid artery stenting. The aim of this study was to test the capture efficiency of five embolic protection devices under reproducible in vitro conditions. The setup consisted of silicone tubes representing the vessel modeling round and oval cross sections. Spherical polystyrene particles (150 µm, COOH-coating) were used to simulate the plaque. The particles were inserted in a clean water circuit and either captured by the device or collected in a glass filter. The missed particles were counted by laser obscuration as a measure of device leakage. The systems Angioguard RX, RX Accunet, FiberNet, FilterWire EZ and EmboshieldNAV were analyzed. At the round cross section, FilterWire EZ demonstrated the highest capture efficiency (0% of missed particles) and RX Accunet the lowest, at 34%. The amount of leaked particles increased to 22% for FilterWire EZ and 89% for Angioguard RX during the test with the oval cross profile.


Assuntos
Artéria Carótida Interna/fisiopatologia , Estenose das Carótidas/fisiopatologia , Dispositivos de Proteção Embólica , Stents/normas , Acidente Vascular Cerebral/fisiopatologia , Humanos , Resultado do Tratamento
13.
J Endovasc Ther ; 24(1): 130-137, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27733689

RESUMO

PURPOSE: To report early clinical outcomes with a novel double-layer stent for the internal carotid artery (ICA) and the in vitro investigation of the stent's mechanical properties. METHODS: A prospective single-center study enrolled 30 consecutive patients (mean age 73.1±6.3 years; 21 men) with symptomatic (n=25) or high-grade (n=5) ICA stenosis treated with the new double-layer carotid CGUARD Embolic Prevention System (EPS) stent, which has an inner open-cell nitinol design with an outer closed-cell polyethylene terephthalate layer. The average stenosis of the treated arteries was 84.1%±7.9% with a mean lesion length of 16.6±2.1 mm. In the laboratory, 8×40-mm stents where tested in vitro with respect to their radial force during expansion, the bending stiffness of the stent system and the expanded stent, as well as the collapse pressure in a thin and flexible sheath. The wall adaptation was assessed using fluoroscopy after stent release in step and curved vessel models. RESULTS: The stent was successfully implanted in all patients. No peri- or postprocedural complications occurred; no minor or major stroke was observed in the 6-month follow-up. The bending stiffness of the expanded stent was 63.1 N·mm2 and (not unexpectedly) was clearly lower than that of the stent system (601.5 N·mm2). The normalized radial force during expansion of the stent to 7.0 mm, consistent with in vivo sizing, was relatively high (0.056 N/mm), which correlates well with the collapse pressure of 0.17 bars. Vessel wall adaptation was harmonic and caused no straightening of the vessel after clinical application. CONCLUSION: Because of its structure, the novel CGUARD EPS stent is characterized by a high flexibility combined with a high radial force and very good plaque coverage. These first clinical results demonstrate a very safe implantation behavior without any stroke up to 6 months after the procedure.


Assuntos
Angioplastia com Balão/instrumentação , Artéria Carótida Interna , Estenose das Carótidas/terapia , Dispositivos de Proteção Embólica , Stents , Idoso , Angiografia Digital , Angioplastia com Balão/efeitos adversos , Artéria Carótida Interna/diagnóstico por imagem , Artéria Carótida Interna/fisiopatologia , Estenose das Carótidas/diagnóstico por imagem , Estenose das Carótidas/fisiopatologia , Feminino , Alemanha , Humanos , Masculino , Teste de Materiais , Estudos Prospectivos , Desenho de Prótese , Falha de Prótese , Índice de Gravidade de Doença , Fatores de Tempo , Resultado do Tratamento
14.
Cardiovasc Revasc Med ; 17(6): 375-83, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27266902

RESUMO

BACKGROUND/PURPOSE: Biodegradable polymers are the main materials for coronary scaffolds. Magnesium has been investigated as a potential alternative and was successfully tested in human clinical trials. However, it is still challenging to achieve mechanical parameters comparative to permanent bare metal (BMS) and drug-eluting stents (DES). As such, in vitro tests are required to assess mechanical parameters correlated to the safety and efficacy of the device. METHODS/MATERIALS: In vitro bench tests evaluate scaffold profiles, length, deliverability, expansion behavior including acute elastic and time-dependent recoil, bending stiffness and radial strength. The Absorb GT1 (Abbott Vascular, Temecula, CA), DESolve (Elixir Medical Corporation, Sunnyvale, CA) and the Magmaris (BIOTRONIK AG, Bülach, Switzerland) that was previously tested in the BIOSOLVE II study, were tested. RESULTS: Crimped profiles were 1.38±0.01mm (Absorb GT1), 1.39±0.01mm (DESolve) and 1.44±0.00mm (Magmaris) enabling 6F compatibility. Trackability was measured depending on stiffness and force transmission (pushability). Acute elastic recoil was measured at free expansion and within a mock vessel, respectively, yielding results of 5.86±0.76 and 5.22±0.38% (Absorb), 7.85±3.45 and 9.42±0.21% (DESolve) and 5.57±0.72 and 4.94±0.31% (Magmaris). Time-dependent recoil (after 1h) was observed for the Absorb and DESolve scaffolds but not for the Magmaris. The self-correcting wall apposition behavior of the DESolve did not prevent time-dependent recoil under vessel loading. CONCLUSIONS: The results of the suggested test methods allow assessment of technical feasibility based on objective mechanical data and highlight the main differences between polymeric and metallic bioresorbable scaffolds.


Assuntos
Implantes Absorvíveis , Angioplastia Coronária com Balão/instrumentação , Doença da Artéria Coronariana/terapia , Metais/química , Polímeros/química , Stents , Tecidos Suporte , Força Compressiva , Doença da Artéria Coronariana/diagnóstico por imagem , Elasticidade , Análise de Falha de Equipamento , Humanos , Teste de Materiais , Pressão , Desenho de Prótese , Falha de Prótese , Resistência à Tração , Fatores de Tempo
15.
J Endovasc Ther ; 22(4): 634-9, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26187981

RESUMO

PURPOSE: To evaluate the in vitro mechanical and clinical implant behavior of a next-generation double-layer stent designed for the carotid artery. METHODS: The new double-layer CASPER-RX stent was implanted in 12 patients (median age 69 years; 8 men) with high-grade symptomatic internal carotid artery stenoses (mean 82%). In the in vitro experiments, the CASPER-RX stent (8-×40-mm model) was investigated with respect to its radial force on expansion and the bending stiffness of the stent system and of the stent in its expanded state, as well as the collapse pressure in a thin, flexible sleeve. The wall adaptation of the expanded stents was assessed by fluoroscopy after release in a step and curve model. RESULTS: Technical success was achieved in all patients without complications; there was no peri- or postinterventional stroke and no stroke or restenosis after 6 months. In the experimental studies, the bending stiffness of the stent on the delivery system (154.9 N mm(2)) was significantly lower than when expanded in a 7-mm flexible tube (467.4 N mm(2)). The radial force on expansion of the stent to 7 mm was low (0.011 N/mm). The collapse pressure was relatively high (0.56 bar) as a result of the stent's particular stent structure. The stent exhibited significant foreshortening of 27.6%. The conformability to the wall in the step model was relatively smooth; in the curve model, straightening occurred with consecutive slight stenosis. CONCLUSION: The first clinical results showed a safe implantation behavior without the occurrence of any ischemia. The structure of the new CASPER-RX stent creates an acceptable flexibility, low radial force, and high collapse pressure. The large foreshortening during implantation should be considered as well as the higher bending stiffness, especially when used in elongated carotid arteries.


Assuntos
Estenose das Carótidas/cirurgia , Desenho de Prótese , Stents , Idoso , Feminino , Humanos , Masculino , Estresse Mecânico , Resultado do Tratamento
16.
Transl Vis Sci Technol ; 4(3): 14, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26175960

RESUMO

PURPOSE: A novel glaucoma drainage device (GDD) with local drug delivery (LDD) system was created and characterized for safety and effectiveness after implantation into the suprachoroidal space (SCS) of rabbit eyes. METHODS: Thin films of two different polymers, Poly(3-hydroxybutyrate) (P(3HB)) and Poly(4-hydroxybutyrate) (P(4HB)), containing the drugs mitomycin C (MitC) or paclitaxel (PTX) were attached to silicone-tubes to create LDD devices. The release kinetics of these drugs were explored in vitro using high performance liquid chromatography (HPLC). Twenty-four New Zealand white rabbits, randomly divided into eight groups, were implanted with different kinds of microstents into SCS. The intraocular pressure (IOP) was monitored noninvasively. After 6 weeks, rabbits were sacrificed and enucleated eyes were used for anterior segment optical coherence tomography (OCT), micro magnetic resonance imaging (MRI), and histology. RESULTS: In vitro, faster drug release from both polymers was observed for MitC compared to PTX. Comparing polymers, the release from P(3HB) matrix was slower for both drugs. MRI and OCT showed all implants maintained a proper location. An effective IOP reduction was observed for up to 6 weeks in eyes with microstents combined with a drug-releasing LDD system. Overall, the surrounding tissue revealed mild-to-moderate inflammation. No pronounced fibrosis was observed in any of the groups. However, both drugs caused damage to the neighboring retina. CONCLUSIONS: The suprachoroidal microstent reduced IOP with mild inflammation in rabbit eyes. To avoid negative effects on the retina, it is necessary to identify novel drugs with less cytotoxicity. Future studies are needed to explore the fibrotic process over the long-term. TRANSLATIONAL RELEVANCE: The presented data serve as a proof of principle study for the concept of a suprachoroidal drug eluting microstent. Future device improvements will be focused on the design of LDD systems and the use of specific anti-inflammatory or antifibrotic agents with less cytotoxicity compared to MitC or PTX. Long-term animal studies using a reliable glaucoma model will be a further step towards clinical application and improvement of surgical glaucoma therapy.

17.
PLoS One ; 10(3): e0116080, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25734818

RESUMO

Drug-coated balloons (DCB), which have emerged as a therapeutic alternative to drug-eluting stents in percutaneous cardiovascular intervention, are well described with regard to clinical efficacy and safety within a number of clinical studies. In vitro studies elucidating the correlation between coating additive and DCB performance are however rare but considered important for the understanding of DCB requirements and the improvement of established DCB. In this regard, we examined three different DCB-systems, which were developed in former studies based on the ionic liquid cetylpyridinium salicylate, the body-own hydrogel hyaluronic acid and the pharmaceutically well-established hydrogel polyvinylpyrrolidone, considering coating morphology, coating thickness, drug-loss, drug-transfer to the vessel wall, residual drug-concentration on the balloon surface and entire drug-load during simulated use in an in vitro vessel model. Moreover, we investigated particle release of the different DCB during simulated use and determined the influence of the three coatings on the mechanical behavior of the balloon catheter. We could show that coating characteristics can be indeed correlated with the performance of DCB. For instance, paclitaxel incorporation in the matrix can reduce the drug wash-off and benefit a high drug transfer. Additionally, a thin coating with a smooth surface and high but delayed solubility can reduce drug wash-off and decrease particle burden. As a result, we suggest that it is very important to characterize DCB in terms of mentioned properties in vitro in addition to their clinical efficacy in order to better understand their function and provide more data for the clinicians to improve the tool of DCB in coronary angioplasty.


Assuntos
Antineoplásicos Fitogênicos/química , Materiais Revestidos Biocompatíveis/química , Stents Farmacológicos , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Líquidos Iônicos/química , Paclitaxel/química , Angioplastia Coronária com Balão , Materiais Revestidos Biocompatíveis/síntese química , Ácido Hialurônico/química , Líquidos Iônicos/síntese química , Microscopia Confocal , Microscopia Eletrônica de Varredura , Modelos Biológicos , Povidona/química , Propriedades de Superfície
18.
J Biomed Mater Res B Appl Biomater ; 101(8): 1560-70, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23687096

RESUMO

Intracoronary stents have markedly improved the outcomes of catheter-based coronary interventions. Intracoronary stent implantation rates of over 90% during coronary angioplasty are common. Stent implantations are associated with a small but statistically significant number of adverse outcomes including restenosis, thrombosis, strut malapposition, incomplete strut endothelialization, and various types of stenting failure. Better matching of biomechanical properties of stents and lesions could further improve the clinical outcome of intracoronary stenting. Thus, in this article, we assess the need for advanced intracoronary stent-lesion matching. We reviewed the data on biomechanics of coronary stents and lesions to develop knowledge-based rationale for optimum intracoronary stent selection. The available technical information on marketed intracoronary stents and the current understanding of the biomechanical properties of coronary lesions at rest and under stress are limited, preventing the development of knowledge-based rationale for optimum intracoronary stent selection at present. Development of knowledge-based selection of intracoronary stents requires standardization of mechanical stent testing, communication of the nonproprietary technical data on stents by the industry and dedicated research into procedural stent-lesion interactions.


Assuntos
Angioplastia Coronária com Balão/instrumentação , Vasos Coronários/cirurgia , Stents , Angioplastia Coronária com Balão/métodos , Fenômenos Biomecânicos , Pressão Sanguínea , Cateterismo , Elasticidade , Desenho de Equipamento , Humanos , Teste de Materiais , Polímeros/química , Trombose , Resultado do Tratamento
19.
Curr Pharm Biotechnol ; 14(1): 98-111, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23092262

RESUMO

Glaucoma is a common cause of blindness in industrialized countries and is the most frequent cause of irreversible blindness worldwide. Since raised intraocular pressure (IOP) has been implicated as the major risk factor, the main goal of all glaucoma treatment is to reduce IOP sufficiently to prevent continuous irreversible retinal ganglion cell damage and progression of visual field loss. Pharmacological reduction of IOP is first-line therapy, followed by laser treatment of the trabecular meshwork and filtering glaucoma surgery, and cyclophotocoagulation of the ciliary body or allogenic implants. The most important glaucoma implants are presented (MOLTENO, AHMED, BAERVELDT, KRUPIN) together with more recent developments (Ex-Press, Eyepass, iStent, Gold micro shunt). Drainage into the suprachoroidal space is a promising option, but is also limited by scarring of the new created outflow route due to proliferation and adhesion of fibroblasts. A deeper understanding of fibroblasts in the related eye compartments is required. Characterization of scleral, choroidal, and, as a reference, Tenon fibroblast subtypes, is possible based on gene expression patterns. Alongside mitomycin C and 5-fluorouracil, newer drugs to prevent fibrosis have been proposed, offering effects that are more specific and more physiological. Effectors involved in wound healing phases and signaling pathways are potential targets for pharmaceutical intervention. Downregulation of growth factors like TGF-ß and their downstream effectors may suppress proliferation and differentiation of fibroblasts, extracellular matrix deposition, wound contraction, and neovascularization. Furthermore, current approaches to local drug delivery in glaucoma implant technology are briefly summarized.


Assuntos
Implantes para Drenagem de Glaucoma , Glaucoma/cirurgia , Animais , Sistemas de Liberação de Medicamentos , Fibroblastos/citologia , Fibrose/prevenção & controle , Humanos , Complicações Pós-Operatórias/prevenção & controle , Cicatrização
20.
J Biomater Appl ; 28(2): 219-31, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22492201

RESUMO

Due to improved tissue regeneration and the enabling of post-operative minimally invasive interventions in the same vessel segment, biodegradable polymeric scaffolds represent a competitive approach to permanent metallic stents in vascular applications. Despite these advantages some challenges, such as the improvement of the scaffold mechanics and enhancement of scaffold visibility during the implantation procedure, are persisting. Therefore, the scope of our studies was to investigate the potential of gold, silver and magnetite nanoparticles incorporated in a polymeric blend of poly(L-lactide)/poly(4-hydroxybutyrate) for image enhancement in X-ray, magnetic resonance or near-infrared imaging. Their impact on mechanical properties of such modified scaffold materials was also evaluated.


Assuntos
Implantes Absorvíveis , Ouro/análise , Nanopartículas de Magnetita/análise , Nanopartículas/análise , Poliésteres/análise , Prata/análise , Prótese Vascular , Imageamento por Ressonância Magnética , Nanopartículas de Magnetita/ultraestrutura , Teste de Materiais , Nanopartículas/ultraestrutura , Espectroscopia de Luz Próxima ao Infravermelho , Microtomografia por Raio-X
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