Collagen tissue treated with chitosan solutions in carbonic acid for improved biological prosthetic 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.

Tritium-Labeled Nanodiamonds as an Instrument to Analyze Bioprosthetic Valve Coatings: A Case of Using a Nanodiamond Containing Coating on a Pork Aorta

Coatings with xenogenic materials, made of detonation nanodiamonds, provide additional strength and increase elasticity. A functionally developed surface of nanodiamonds makes it possible to apply antibiotics. Previous experiments show the stability of such coatings; however, studies on stability in the bloodstream and calcification of the material in natural conditions have yet to be conducted. Tritium-labeled nanodiamonds (negative and positive) were obtained by the tritium activation method and used to develop coatings for a pork aorta to analyze their stability in a pig's bloodstream using a radiotracer technique. A chitosan layer was applied from a solution of carbonic acid under high-pressure conditions to prevent calcification. The obtained materials were used to prepare a porcine conduit, which was surgically stitched inside the pig's aorta for four months. The aorta samples, including nanodiamond-coated and control samples, were analyzed for nanodiamond content and calcium, using the radiotracer and ICP-AES methods. A histological analysis of the materials was also performed. The obtained coatings illustrate a high in vivo stability and low levels of calcification for all types of nanodiamonds. Even though we did not use additional antibiotics in this case, the development of infection was not observed for negatively charged nanodiamonds, opening up prospects for their use in developing coatings.

A Study of the Properties of Scaffolds for Bone Regeneration Modified with Gel-like Coatings of Chitosan and Folic Acid

The research has been conducted to obtain scaffolds for cancellous bone regeneration. Polylactide scaffolds were made by the phase inversion method with a freeze-extraction variant, including gelling polylactide in its non-solvent. Substitutes made of polylactide are hydrophobic, which limits cell adhesion. For this reason, the scaffolds were modified using chitosan and folic acid by forming gel-like coatings on the surface. The modification aimed to improve the material's surface properties and increase cell adhesion. Analyses of obtained scaffolds confirmed the effectiveness of performed changes. The presence of chitosan and folic acid was confirmed in the modified scaffolds, while all scaffolds retained high open porosity, which is essential for proper cell growth inside the scaffold and the free flow of nutrients. Hydrostatic weighing showed that the scaffolds have high mass absorbability, allowing them to be saturated with biological fluids. There were also cytotoxicity tests performed on 24 h extracts of the materials obtained, which indicated a lack of cytotoxic effect.

An In Vitro Study of Chitosan-Coated Bovine Pericardium as a Dural Substitute Candidate

Defects in the dura matter can be caused by head injury, and many cases require neurosurgeons to use artificial dura matter. Bovine pericardium is an option due to its abundant availability, adjustable size and characteristics, and because it has more collagen than porcine or equine pericardia. Nevertheless, the drawback of bovine pericardium is that it has a higher inflammatory effect than other synthetic dura matters. Chitosan has been shown to have a strong anti-inflammatory effect and has good tensile strength; thus, the idea was formulated to use chitosan as a coating for bovine pericardium. This study used decellularized bovine pericardial membranes with 0.5% sodium dodecyl sulphate and coatings containing chitosan at concentrations of 0.25%, 0.5%, 0.75%, and 1%. An FTIR test showed the presence of a C=N functional group as a bovine pericardium-chitosan bond. Morphological tests of the 0.25% and 0.5% chitosan concentrations showed standard pore sizes. The highest tensile strength percentage was shown by the membrane with a chitosan concentration of 1%. The highest degradation rate of the membrane was observed on the 7th and 14th days for 0.75% and 1% concentrations, and the lowest swelling ratio was observed for the 0.25% concentration. The highest level of cell viability was found for 0.75% chitosan. The bovine pericardium membrane with a 0.75% concentration chitosan coating was considered the optimal sample for use as artificial dura matter.

Chitosan-Based High-Intensity Modification of the Biodegradable Substitutes for Cancellous Bone

An innovative approach to treating bone defects is using synthetic bone substitutes made of biomaterials. The proposed method to obtain polylactide scaffolds using the phase inversion technique with a freeze extraction variant enables the production of substitutes with morphology similar to cancellous bone (pore size 100-400 µm, open porosity 94%). The high absorbability of the implants will enable their use as platelet-rich plasma (PRP) carriers in future medical devices. Surface modification by dipping enabled the deposition of the hydrophilic chitosan (CS) layer, maintaining good bone tissue properties and high absorbability (850% dry weight). Introducing CS increases surface roughness and causes local changes in surface free energy, promoting bone cell adhesion. Through this research, we have developed a new and original method of low-temperature modification of PLA substitutes with chitosan. This method uses non-toxic reagents that do not cause changes in the structure of the PLA matrix. The obtained bone substitutes are characterised by exceptionally high hydrophilicity and morphology similar to spongy bone. In vitro studies were performed to analyse the effect of morphology and chitosan on cellular viability. Substitutes with properties similar to those of cancellous bone and which promote bone cell growth were obtained.

Current development of bovine jugular vein conduit for right ventricular outflow tract reconstruction

Right ventricular outflow tract (RVOT) reconstruction is a common surgical method to treat congenital cardiac lesions, and bovine jugular vein conduit (BJVC) has become a prevalent candidate of prosthetic material for this procedure since 1999. Although many clinical studies have shown encouraging results on BJVCs, complications such as stenosis, aneurysmal dilatation, valve insufficiency, and infective endocarditis revealed in other clinical outcomes still remain problematic. This review describes the underlying mechanisms causing respective complications, and summarizes the current technological development that may address those causative factors. Novel crosslinking agents, decellularization techniques, conduit coatings, and physical reinforcement materials have improved the performances of BJVCs. The authors expect that the breakthroughs in the clinical application of BJVC may come from new genetic research findings and advanced characterization apparatuses and bioreactors, and are optimistic that the BJVC will in the future provide sophisticated therapies for next-generation RVOT reconstruction.

Natural Polymers in Heart Valve Tissue Engineering: Strategies, Advances and Challenges

In the history of biomedicine and biomedical devices, heart valve manufacturing techniques have undergone a spectacular evolution. However, important limitations in the development and use of these devices are known and heart valve tissue engineering has proven to be the solution to the problems faced by mechanical and prosthetic valves. The new generation of heart valves developed by tissue engineering has the ability to repair, reshape and regenerate cardiac tissue. Achieving a sustainable and functional tissue-engineered heart valve (TEHV) requires deep understanding of the complex interactions that occur among valve cells, the extracellular matrix (ECM) and the mechanical environment. Starting from this idea, the review presents a comprehensive overview related not only to the structural components of the heart valve, such as cells sources, potential materials and scaffolds fabrication, but also to the advances in the development of heart valve replacements. The focus of the review is on the recent achievements concerning the utilization of natural polymers (polysaccharides and proteins) in TEHV; thus, their extensive presentation is provided. In addition, the technological progresses in heart valve tissue engineering (HVTE) are shown, with several inherent challenges and limitations. The available strategies to design, validate and remodel heart valves are discussed in depth by a comparative analysis of in vitro, in vivo (pre-clinical models) and in situ (clinical translation) tissue engineering studies.

Microstructure and Mechanical Strength Properties of Chitosan Sponges Obtained from Polymer Solutions in Carbonic Acid

Abstract

Polymer sponges based on chitosan are first obtained from chitosan solutions in carbonic acid and gels based on these solutions crosslinked by a noncytotoxic agent of natural origin, genipin. A comparative analysis of the structure and mechanical strength properties of sponges prepared from chitosan solutions in carbonic and acetic acids is carried out. It is shown that the addition of genipin in an amount of ~2 wt % to a chitosan solution in carbonic acid leads to a decrease in the average pore size by ~2.5 times and a significant increase in the strength characteristics of the material in comparison with the sponge prepared without genipin.

Green approach for fabrication of bacterial cellulose-chitosan composites in the solutions of carbonic acid under high pressure CO2

The functionalization of the bacterial cellulose (BC) surface with a chitosan biopolymer to expand the areas of possible applications of the modified BC is an important scientific task. The creation of such composites in the carbonic acid solutions that were performed in this work has several advantages in terms of being biocompatible and eco-friendly. Quantitative analysis of chitosan content in the composite was conducted by tritium-labeled chitosan radioactivity detection method and this showed three times increased chitosan loading. Different physicochemical methods showed successful incorporation of chitosan into the BC matrix and interaction with it through hydrogen bonds. Microscopy results showed that the chitosan coating with a thickness of around 10 nm was formed in the bulk of BC, covering each microfibril. It was found that the inner specific surface area increased 1.5 times on deposition of chitosan from the solutions in carbonic acid.

Structural and mechanical characteristics of collagen tissue coated with chitosan in a liquid CO2/water system at different pressures

Chitosan coatings of biological heart-valve prostheses enhance their biocompatibility, resistance to pathogenic microflora and lifetime. Collagen tissues can be coated with chitosan in aqueous solution acidified, to make chitosan soluble, with H₂CO₃ formed from a coexisting liquid CO₂ phase under pressure. The advantage of H₂CO₃ is that it can be easily removed after the coating procedure. This study assessed the effects of 6-50 MPa CO₂ pressure during the coating procedure on the structure and mechanical properties of the resulting biocomposite matrices. The dependence of chitosan adsorption on CO₂ pressure was bell-shaped, reaching a maximum adsorption of 0.8 mass % at 40 MPa. Tissue surface became highly porous upon pressure treatment. At 50 MPa, the pores merged to form furrows with lengths of several hundred micrometers, accompanied by collagen fibril reorganisation. Chitosan coating did not affect tissue tensile strength in the axial direction, but increased it by 75% in the radial direction in the tissue coated at 50 MPa pressure. Strain at break, a measure of elasticity, increased in both directions by up to 100% upon coating with chitosan. CO₂ pressure of 30-50 MPa seems thus optimal in terms of chitosan incorporation and tissue mechanical properties.

Inferring anatomical therapeutic chemical (ATC) class of drugs using shortest path and random walk with restart algorithms

The anatomical therapeutic chemical (ATC) classification system is a widely accepted drug classification scheme. This system comprises five levels and includes several classes in each level. Drugs are classified into classes according to their therapeutic effects and characteristics. The first level includes 14 main classes. In this study, we proposed two network-based models to infer novel potential chemicals deemed to belong in the first level of ATC classification. To build these models, two large chemical networks were constructed using the chemical-chemical interaction information retrieved from the Search Tool for Interactions of Chemicals (STITCH). Two classic network algorithms, shortest path (SP) and random walk with restart (RWR) algorithms, were executed on the corresponding network to mine novel chemicals for each ATC class using the validated drugs in a class as seed nodes. Then, the obtained chemicals yielded by these two algorithms were further evaluated by a permutation test and an association test. The former can exclude chemicals produced by the structure of the network, i.e., false positive discoveries. By contrast, the latter identifies the most important chemicals that have strong associations with the ATC class. Comparisons indicated that the two models can provide quite dissimilar results, suggesting that the results yielded by one model can be essential supplements for those obtained by the other model. In addition, several representative inferred chemicals were analyzed to confirm the reliability of the results generated by the two models. This article is part of a Special Issue entitled: Accelerating Precision Medicine through Genetic and Genomic Big Data Analysis edited by Yudong Cai & Tao Huang.

3D Biofabrication of Thermoplastic Polyurethane (TPU)/Poly-l-lactic Acid (PLLA) Electrospun Nanofibers Containing Maghemite (γ-Fe₂O₃) for Tissue Engineering Aortic Heart Valve

Valvular dysfunction as the prominent reason of heart failure may causes morbidity and mortality around the world. The inability of human body to regenerate the defected heart valves necessitates the development of the artificial prosthesis to be replaced. Besides, the lack of capacity to grow, repair or remodel of an artificial valves and biological difficulty such as infection or inflammation make the development of tissue engineering heart valve (TEHV) concept. This research presented the use of compound of poly-l-lactic acid (PLLA), thermoplastic polyurethane (TPU) and maghemite nanoparticle (γ-Fe₂O₃) as the potential biomaterials to develop three-dimensional (3D) aortic heart valve scaffold. Electrospinning was used for fabricating the 3D scaffold. The steepest ascent followed by the response surface methodology was used to optimize the electrospinning parameters involved in terms of elastic modulus. The structural and porosity properties of fabricated scaffold were characterized using FE-SEM and liquid displacement technique, respectively. The 3D scaffold was then seeded with aortic smooth muscle cells (AOSMCs) and biological behavior in terms of cell attachment and proliferation during 34 days of incubation was characterized using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and confocal laser microscopy. Furthermore, the mechanical properties in terms of elastic modulus and stiffness were investigated after cell seeding through macro-indentation test. The analysis indicated the formation of ultrafine quality of nanofibers with diameter distribution of 178 ± 45 nm and 90.72% porosity. In terms of cell proliferation, the results exhibited desirable proliferation (109.32 ± 3.22% compared to the control) of cells over the 3D scaffold in 34 days of incubation. The elastic modulus and stiffness index after cell seeding were founded to be 22.78 ± 2.12 MPa and 1490.9 ± 12 Nmm², respectively. Overall, the fabricated 3D scaffold exhibits desirable structural, biological and mechanical properties and has the potential to be used in vivo.

Globular chitosan treatment of bovine jugular veins: evidence of anticalcification efficacy in the subcutaneous rat model

Vascular xenografts are widely used in cardiovascular surgery as an alternative to autologous vessels and vascular allografts. Calcification is one of the main drawbacks of vascular grafts, especially among young patients and children. Among different anticalcification approaches, chitosan emerges as a highly promising candidate due to its versatility, natural origin, and biocompatibility. We investigated the anticalcification efficacy of globular chitosan ("Chitozol") as it demonstrated the improved rate of water solubility as compared with conventional linear macromolecules of chitosan. In addition, we supposed that compact globular form of "Chitozol" molecules could provide effective penetration of extracellular matrix of bovine jugular veins (BJVs). Our results revealed that "Chitozol" treatment mitigated calcification in the experimental groups as compared to the control groups (without any treatment, conventional treatment with glutaraldehyde, and commercially available Contegra conduit). Different concentrations of "Chitozol" (0.3% and 3%), as well as different incubation times (15 and 30min), were equally effective in the prevention of calcification. In addition, "Chitozol" treatment with decellularization of BJVs demonstrated slightly improved stress-strain properties of unimplanted samples. Thus, the filling of fresh BJV with globular chitosan is proposed as a promising emerging treatment for the mitigation of calcific degeneration in BJVs xenografts.

Optimization and development of Maghemite (γ-Fe2O3) filled poly-l-lactic acid (PLLA)/thermoplastic polyurethane (TPU) electrospun nanofibers using Taguchi orthogonal array for tissue engineering heart valve

Tissue engineering (TE) is an advanced principle to develop a neotissue that can resemble the original tissue characteristics with the capacity to grow, to repair and to remodel in vivo. This research proposed the optimization and development of nanofiber based scaffold using the new mixture of maghemite (γ-Fe₂O₃) filled poly-l-lactic acid (PLLA)/thermoplastic polyurethane (TPU) for tissue engineering heart valve (TEHV). The chemical, structural, biological and mechanical properties of nanofiber based scaffold were characterized in terms of morphology, porosity, biocompatibility and mechanical behaviour. Two-level Taguchi experimental design (L8) was performed to optimize the electrospun mats in terms of elastic modulus using uniaxial tensile test where the studied parameters were flow rate, voltage, percentage of maghemite nanoparticles in the content, solution concentration and collector rotating speed. Each run was extended with an outer array to consider the noise factors. The signal-to-noise ratio analysis indicated the contribution percent as follow; Solution concentration>voltage>maghemite %>rotating speed>flow rate. The optimum elastic modulus founded to be 28.13±0.37MPa in such a way that the tensile strain was 31.72% which provided desirability for TEHV. An empirical model was extracted and verified using confirmation test. Furthermore, an ultrafine quality of electrospun nanofibers with 80.32% porosity was fabricated. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and cell attachment using human aortic smooth muscle cells exhibited desirable migration and proliferation over the electrospun mats. The interaction between blood content and the electrospun mats indicated a mutual adaption in terms of clotting time and hemolysis percent. Overall, the fabricated scaffold has the potential to provide the required properties of aortic heart valve.

Chitosan coatings with enhanced biostability in vivo

In this article, we study the stability of chitosan coatings applied on glutaraldehyde-stabilized bovine pericardium when exposed to biodegradation in vivo in the course of model subcutaneous tests on rats. The coatings were deposited from carbonic acid solutions, that is, H₂ O saturated with CO₂ at high pressure. Histological sections of treated pericardium samples demonstrated that the structure of pericardial connective tissues was not significantly altered by the coating application method. It was revealed that the dynamics of biodegradation depended on the total mass of chitosan applied as well as on the DDA of chitosan used. As long as the amount of chitosan did not exceed a certain threshold limit, no detectable degradation occurred within the time of the tests (12 weeks for the rat model). For higher chitosan amounts, we detected a ∼20% reduction of the mass after the in vivo exposition. The presumed mechanism of such behavior is discussed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 270-277, 2018.

Sulfonated chitosan and dopamine based coatings for metallic implants in contact with blood

Thrombosis and calcification constitute the main clinical problems when blood-interacting devices are implanted in the body. Coatings with thin polymer layers represent an acknowledged strategy to modulate interactions between the material surface and the blood environment. To ensure the implant success, at short-term the coating should limit platelets adhesion and delay the clot formation, and at long-term it should delay the calcification process. Sulfonated chitosan, if compared to native chitosan, shows the unique ability to reduce proteins adsorption, decrease thrombogenic properties and limit calcification. In this work, stainless steel surfaces, commonly used for cardiovascular applications, were coated with sulfonated chitosan, by using dopamine and PEG as anchors, and the effect of these grafted surfaces on platelet adhesion, clot formation as well as on calcification were investigated. Surface characterization techniques evidenced that the coating formation was successful, and the sulfonated chitosan grafted sample exhibited a higher roughness and hydrophilicity, if compared to native chitosan one. Moreover, sulfonated surface limited platelet activation and the process of clot formation, thus confirming its high biological performances in blood. Calcium deposits were also lower on the sulfonated chitosan sample compared to the chitosan one, thus showing that calcification was minimal in presence of sulfonate groups. In conclusion, this sulfonated-modified surface has potential to be as blood-interacting material.

Current applications of nanoparticles in infectious diseases

For decades infections have been treated easily with drugs. However, in the 21st century, they may become lethal again owing to the development of antimicrobial resistance. Pathogens can become resistant by means of different mechanisms, such as increasing the time they spend in the intracellular environment, where drugs are unable to reach therapeutic levels. Moreover, drugs are also subject to certain problems that decrease their efficacy. This requires the use of high doses, and frequent administrations must be implemented, causing adverse side effects or toxicity. The use of nanoparticle systems can help to overcome such problems and increase drug efficacy. Accordingly, there is considerable current interest in their use as antimicrobial agents against different pathogens like bacteria, virus, fungi or parasites, multidrug-resistant strains and biofilms; as targeting vectors towards specific tissues; as vaccines and as theranostic systems. This review begins with an overview of the different types and characteristics of nanoparticles used to deliver drugs to the target, followed by a review of current research and clinical trials addressing the use of nanoparticles within the field of infectious diseases.