Optimization of Inlet Valve Leaflet Shape Using Metamodel and Fluid-Structure Interaction

Cardiac assist devices like continuous flow ventricular assist devices (CF-VAD) provide several benefits, including improved durability or higher energy efficiency. This paper presents the shape optimization for the inlet valve geometry of the pulsatile VAD using a metamodeling framework and fluid-structure interaction (FSI). The main task of the inlet valve is preventing the backflow to occur and keep proper valve washing as well as low hemolysis, induced by high shear stress. The finite element (FE) model of the valve was generated using a parametric model. The FE model was associated with a fluid flow analysis environment. The shear stress at wall leaflet structures was observed for all design points. For selected design variables, the minimization of the leaflet's wall shear stresses was carried out. As a result of optimization, the optimal valve leaflet shape was found. The developed modeling methodology can be easily adapted to investigate biomedical problems especially in the process of creating devices supporting cardiac circulation

In vitro and in vivo testing of stereolithography (SLA)-manufactured haemocompatible photopolymers for blood pump

A major medical problem of state-of-the-art heart ventricular assist devices (LVADs) is device-induced thrombus formation due to inadequate blood-flow dynamics generated by the blood pump rotor. The latter is a highly complex device, with difficulties during conventional manufacturing through milling or casting. Therefore, the additive manufacturing technology relying on stereo-lithography (SLA) capable of producing parts of significantly increased freedom for a blood-flow-compatible, thrombus-risk-free design was chosen as novel and flexible technology for that type of application. However, as yet state-of-the-art SLA is not suitable to produce fully safe blood-contacting devices. Therefore, the present experiment covered chemical, mechanical, rheological, tribological, and complex biocompatibility characterization in accordance with i.a. ISO 10993 standards, including hemolysis and an acute thrombogenicity blood test on fresh animal blood (both as innovative laboratory tests to avoid animal usage in preclinical studies) with a special focus on testing demonstrators of miniaturized blood pump rotors. The conducted tests indicated acceptable biocompatibility of the material and a slight improvement in biocompatibility with surface modification. Additionally, a high biocompatibility of the tested materials was confirmed. Based on studies and simulations, stereolithography (SLA) as an additive manufacturing technology with significantly increased freedom for a blood-flow-compatible, thrombus-risk-free design was chosen as a novel and flexible technology basis in the 4DbloodROT project to enable future manufacturing of rotors with exceptional biomimetic complexity

Production, characterization and application of oxide nanotubes on Ti-6Al-7Nb alloy as a potential drug carrier

This work concerns the development of a method of functionalization of the surface of the biomedical Ti–6Al–7Nb alloy by producing oxide nanotubes (ONTs) with drug-eluting properties. Shaping of the morphology, microstructure, and thickness of the oxide layer was carried out by anodization in an aqueous solution of 1 M ethylene glycol with the addition of 0.2 M NH4F in the voltage range 5–100 V for 15–60 min at room temperature. The characterization of the physicochemical properties of the obtained ONTs was performed using SEM, XPS, and EDAX methods. ONTs have been shown to be composed mainly of TiO2, Al2O3, and Nb2O5. Single-walled ONTs with the largest specific surface area of 600 cm2 cm−2 can be obtained by anodization at 50 V for 60 min. The mechanism of ONT formation on the Ti–6Al–7Nb alloy was studied in detail. Gentamicin sulfate loaded into ONTs was studied using FTIR, TG, DTA, and DTG methods. Drug release kinetics was determined by UV–Vis spectrophotometry. The obtained ONTs can be proposed for use in modern implantology as carriers for drugs delivered locally in inflammatory conditions

Acoustic system for the estimation of the temporary blood chamber volume of the POLVAD heart supporting prosthesis

Abstract Background The paper presents a newly researched acoustic system for blood volume measurements for the developed family of Polish ventricular assist devices. The pneumatic heart-supporting devices are still the preferred solution in some cases, and monitoring of their operation, especially the temporary blood volume, is yet to be solved. Methods The prototype of the POLVAD-EXT prosthesis developed by the Foundation of Cardiac Surgery Development, Zabrze, Poland, is equipped with the newly researched acoustic blood volume measurement system based on the principle of Helmholtz’s acoustic resonance. The results of static volume measurements acquired using the acoustic sensor were verified by measuring the volume of the liquid filling the prosthesis. Dynamic measurements were conducted on the hybrid model of the human cardiovascular system at the Foundation, with the Transonic T410 (11PLX transducer - 5% uncertainty) ultrasound flow rate sensor, used as the reference. Results The statistical analysis of a series of static tests have proved that the sensor solution provides blood volume measurement results with uncertainties (understood as a standard mean deviation) of less than 10%. Dynamic tests show a high correlation between the results of the acoustic system and those obtained by flow rate measurements using an ultrasound transit time type sensor. Conclusions The results show that noninvasive, online temporary blood volume measurements in the POLVAD-EXT prosthesis, making use of the newly developed acoustic system, provides accurate static and dynamic measurements results. Conducted research provides the preliminary view on the possibility of reducing the additional sensor chamber volume in future.</p

In-Vitro Biocompatibility and Hemocompatibility Study of New PET Copolyesters Intended for Heart Assist Devices

(1) Background: The evaluation of ventricular assist devices requires the usage of biocompatible and chemically stable materials. The commonly used polyurethanes are characterized by versatile properties making them well suited for heart prostheses applications, but simultaneously they show low stability in biological environments. (2) Methods: An innovative material-copolymer of poly(ethylene-terephthalate) and dimer linoleic acid&mdash;with controlled and reproducible physico-mechanical and biological properties was developed for medical applications. Biocompatibility (cytotoxicity, surface thrombogenicity, hemolysis, and biodegradation) were evaluated. All results were compared to medical grade polyurethane currently used in the extracorporeal heart prostheses. (3) Results: No cytotoxicity was observed and no significant decrease of cells density as well as no cells growth reduction was noticed. Thrombogenicity analysis showed that the investigated copolymers have the thrombogenicity potential similar to medical grade polyurethane. No hemolysis was observed (the hemolytic index was under 2% according to ASTM 756-00 standard). These new materials revealed excellent chemical stability in simulated body fluid during 180 days aging. (4) Conclusions: The biodegradation analysis showed no changes in chemical structure, molecular weight distribution, good thermal stability, and no changes in surface morphology. Investigated copolymers revealed excellent biocompatibility and great potential as materials for blood contacting devices

Semi-Quantitative Method of Assessing the Thrombogenicity of Biomaterials Intended for Long-Term Blood Contact

Biomaterials used in cardiosurgical implants and artificial valves that have long-term contact with blood pose a great challenge for researchers due to the induction of thrombogenicity. So far, the assessment of the thrombogenicity of biomaterials has been performed with the use of highly subjective descriptive methods, which has made it impossible to compare the results of various experiments. The aim of this paper was to present a new semi-quantitative method of thrombogenicity assessment based on scanning electron microscope (SEM) images of an adhered biological material deposited on the surfaces of prepared samples. The following biomaterials were used to develop the proposed method: Bionate 55D polyurethane, polyether-ether ketone, Ti6Al7Nb alloy, sintered yttria-stabilized zirconium oxide (ZrO2 + Y2O3), collagen-coated glass, and bacterial cellulose. The samples were prepared by incubating the biomaterials with platelet-rich plasma. In order to quantify the thrombogenic properties of the biomaterials, a TR parameter based on the fractal dimension was applied. The obtained results confirmed that the use of the fractal dimension enables the quantitative assessment of thrombogenicity and the proper qualification of samples in line with an expert’s judgment. The polyurethanes showed the best thrombogenic properties of the tested samples: Bionate 55D (TR = 0.051) and PET-DLA 65% (average TR = 0.711). The ceramics showed the worst thrombogenic properties (TR = 1.846). All the tested materials were much less thrombogenic than the positive control (TR = 5.639)