A Biomechanical and Microstructural Analysis of Bovine and Porcine Pericardium for Use in Bioprosthetic Heart Valves

Coating based on chitosan/vancomycin nanoparticles: Patterns of formation in a water-carbon dioxide biphase system and in vivo stability

The patterns of formation of chitosan nanoparticles doped with vancomycin and coatings based on them in carbonate solutions have been investigated for the first time in this study. Using a technique of radioactive indicators, it was found that at a CO2 pressure of 30 MPa, the yield of the nanoparticles was ∼85 %, and a maximum antibiotic encapsulation efficiency of ∼30 % was achieved. By spectrophotometric and high-resolution microscopy, it was found that the coating of stabilized xenopericardial tissue of bioprosthetic heart valve, based on chitosan nanoparticles doped with vancomycin with a zeta potential |ζ| ∼20 mV completely covers collagen fibers by depositing about 60 nm nanoparticles onto them under direct deposition from carbonic acid at a pressure of 30 MPa CO2. The coating preserves the mechanical strength characteristics of collagen tissue and completely suppresses the growth of S. aureus pathogenic biofilm. This is consistent with the observed increase in antibiotic release of 15 % when the medium was acidified. Histological study demonstrated that the structure of pericardial tissues was not significantly altered by the deposition nanoparticles from carbonic acid. It was found that the rate of biodegradation of polymers and vancomycin in the coating differs by half (16 weeks for the rat model). A significantly lower degradation rate of antibiotics (∼50 % of vancomycin total remaining mass and ∼25 % of chitosan) was associated with its reliable encapsulation into nanoparticles.

Effect of mechanical fatigue on commercial bioprosthetic TAVR valve mechanical and microstructural properties

Valvular structural deterioration is of particular concern for transcatheter aortic valve replacements due to their suspected shorter longevity and increasing use in younger patient populations. In this work we investigated the mechanical and microstructural changes in commercial TAVR valves composed of both glutaraldehyde fixed bovine and porcine pericardium (GLBP and GLPP) following accelerated wear testing (AWT) as outlined in ISO 5840 standards. This provided greater physiological relevance to the loading compared to previous studies and by utilizing digital image correlation we were able to obtain strain contours for each leaflet pre and post fatigue and identify sites of fatigue damage. The areas of greatest change in mechanical strain for each leaflet were then further probed using biaxial tensile testing, confocal microscopy, and electron microscopy. It was observed that overall strain decreased in the GLPP valves following AWT of 200 million cycles while the GLBP valve showed an increase in overall strain. Biaxial tensile testing showed a statistically significant reduction in stress for GLPP while no significant changes were seen for GLBP. Both confocal and electron microscopy showed a disruption to the gross collagen organization and fibrillar structure, including fragmentation, for GLPP but only the former for GLBP. However, further test data is required to confirm these findings and to provide a better understanding of this fatigue pathway is required such that it can be incorporated into both valve design and selection processes to improve overall longevity for both GLPP and GLBP devices.

The Measurement of Bovine Pericardium Density and Its Implications on Leaflet Stress Distribution in Bioprosthetic Heart Valves

PURPOSE

Bioprosthetic Heart Valves (BHVs) are widely used in clinical practice, showing promising outcomes. Computational modeling offers a valuable tool for quantitatively characterizing BHVs. To ensure the accuracy of computational models, it is crucial to consider precise leaflet properties, including mechanical properties and density. Bovine pericardium (BP) serves as a common material for BHV leaflets. Previous computational studies often assume BP density to approximate that of water or blood. Given that BP leaflets undergo various treatments, such as tissue fixation and anti-calcification, this study aims to measure the density of BP used in BHVs and assess its impact on leaflet stress distribution.

METHODS

Eight square BP samples were laser cut from Edwards BP patches and their density was determined. Specimen weight was measured using an A&D Analytical Balance, while volume was assessed through high-resolution imaging. Additionally, finite element models resembling a BHV, like the Carpentier-Edwards PERIMOUNT Magna, were constructed in ABAQUS.

RESULTS

The average density of the BP samples was found to be 1,410 kg/m3. During the acceleration phase of a cardiac cycle, the maximum stress reached 1.89 MPa for a density of 1,410 kg/m3 and 2.47 MPa for a density of 1,000 kg/m3 (a 30.7% difference). In the deceleration phase, the maximum stress reached 713 kPa and 669 kPa, respectively.

CONCLUSION

Leaflet stress distribution and motion in BHVs are influenced by density variations. Establishing an accurate density value for BHV leaflets is imperative for enhancing the computational models, which can ultimately contribute to improved BHV design and outcomes.

Profitability of Chemically Cross-Linked Collagen Scaffold Production Using Bovine Pericardium: Revaluing Waste from the Meat Industry for Biomedical Applications

The meat industry generates a large amount of waste that can be used to create useful products such as bio-implants, which are usually expensive. In this report, we present an economic analysis of a continuous process for large-scale chemically cross-linked collagen scaffold (CCLCS) production in a Mexican context. For this purpose, three production capacities were simulated using SuperPro Designer^® v 12.0: 5, 15, and 25 × 10³ bovine pericardium units (BPU) per month as process feedstock. Data indicated that these capacities produced 2.5, 7.5, and 12.5 kg of biomesh per batch (per day), respectively. In addition, Net Unit Production Costs (NUPC) of 784.57, 458.94, and 388.26 $USD.kg^-1 were obtained, correspondingly, with selling prices of 0.16 ± 0.078 USD.cm^-2, 0.086 ± 0.043 USD.cm^-2, and 0.069 ± 0.035 USD.cm^-2, in the same order. We found that these selling prices were significantly lower than those in the current market in Mexico. Finally, distribution of costs associated with the process followed the order: raw materials > facility-dependent > labor > royalties > quality analysis/quality control (QA/QC) > utilities. The present study showed the feasibility of producing low-cost and highly profitable CCLCS with a relatively small investment. As a result, the circular bioeconomy may be stimulated.

Polymeric Heart Valves Will Displace Mechanical and Tissue Heart Valves: A New Era for the Medical Devices

The development of a novel artificial heart valve with outstanding durability and safety has remained a challenge since the first mechanical heart valve entered the market 65 years ago. Recent progress in high-molecular compounds opened new horizons in overcoming major drawbacks of mechanical and tissue heart valves (dysfunction and failure, tissue degradation, calcification, high immunogenic potential, and high risk of thrombosis), providing new insights into the development of an ideal artificial heart valve. Polymeric heart valves can best mimic the tissue-level mechanical behavior of the native valves. This review summarizes the evolution of polymeric heart valves and the state-of-the-art approaches to their development, fabrication, and manufacturing. The review discusses the biocompatibility and durability testing of previously investigated polymeric materials and presents the most recent developments, including the first human clinical trials of LifePolymer. New promising functional polymers, nanocomposite biomaterials, and valve designs are discussed in terms of their potential application in the development of an ideal polymeric heart valve. The superiority and inferiority of nanocomposite and hybrid materials to non-modified polymers are reported. The review proposes several concepts potentially suitable to address the above-mentioned challenges arising in the R&D of polymeric heart valves from the properties, structure, and surface of polymeric materials. Additive manufacturing, nanotechnology, anisotropy control, machine learning, and advanced modeling tools have given the green light to set new directions for polymeric heart valves.