Effects of the Degree of Deacetylation on the Single-Molecule Mechanics of Chitosans

"Biological evaluation of 3D-Printed chitosan-based scaffolds for tissue engineering"

Chitosan is a natural polysaccharide with excellent biocompatibility, biodegradability, and antibacterial capabilities, making it a good candidate for tissue engineering. 3D printing has revolutionized biomaterial fabrication owing to its precision, customization, and ability to create complex structures. This article aims to provide an overview of the current advances in 3D printing techniques for fabricating scaffolds based on chitosan and its derivatives. It also describes various printing methods, including extrusion bioprinting technique, inkjet bioprinting, stereolithography, digital light processing, and indirect 3D printing for controlling porosity, mechanical strength, and biological characteristics of chitosan scaffolds for a variety of tissues, like bone, vascular, cardiac, cartilage, and skin. This review also examines the biological properties of 3D-printed chitosan scaffolds. The advancements in biological performance and 3D printing technology indicate a promising future for developing flexible, customized scaffolds consisting of chitosan.

Pharmaceutical chitosan hydrogels: A review on its design and applications

Chitosan (CS) has become a focal point of extensive research in the pharmaceutical industry due to its remarkable biodegradability, biocompatibility and sustainability. Chitosan hydrogels (CS HGs) are characterized by their viscoelasticity, flexibility and softness. The polar surfaces exhibit properties that mitigate interfacial tension between the hydrogel and body fluids. The inherent compatibility of CS HGs with body tissues and fluids positions them as outstanding polymers for delivering therapeutic proteins, peptides, DNA, siRNA, and vaccines. Designed to release drugs through mechanisms such as swelling-based diffusion, bioerosion, and responsiveness to stimuli, CS HGs offer a versatile platform for drug delivery. CS HGs play pivotal roles in serving purposes such as prolonging the duration of preprogrammed drug delivery, enabling stimuli-responsive smart delivery to target sites, protecting encapsulated drugs within the mesh network from adverse environments, and facilitating mucoadhesion and penetration through cell membranes. This review comprehensively outlines various novel preparation methods of CS HGs, delving into the parameters influencing drug delivery system design, providing a rationale for CS HG utilization in drug delivery, and presenting diverse applications across the pharmaceutical landscape. In synthesizing these facets, the review seeks to contribute to a nuanced understanding of the multifaceted role that CS HGs play in advancing drug delivery methodologies.

Application of chitosan in fruit preservation: A review

Fruit preservation after harvest is one of the key issues in current agriculture, rural areas, and for farmers. Using chitosan to keep fruits fresh, which can reduce the harm caused by chemical preservative residue to human health. It also helps avoid the disadvantages of the high cost of physical preservation and the challenges associated with difficult operation. This review focuses on the application progress of chitosan in fruit preservation. Studies have shown that chitosan inhibits the growth of bacteria and fungi, and delays fruit aging and decay. Furthermore, it can regulate the respiration and physiological metabolism of fruit, helping to maintain its quality and nutritional value. The preservation mechanism of chitosan includes its antibacterial properties, film-forming properties, and its effects on the physiological processes of fruit. However, in practical applications, issues such as determining the optimal concentration and treatment of chitosan still require further research and optimization.

Bio-Based and Biodegradable Polymeric Materials for a Circular Economy

Nowadays, plastic contamination worldwide is a concerning reality that can be addressed with appropriate society education as well as looking for innovative polymeric alternatives based on the reuse of waste and recycling with a circular economy point of view, thus taking into consideration that a future world without plastic is quite impossible to conceive. In this regard, in this review, we focus on sustainable polymeric materials, biodegradable and bio-based polymers, additives, and micro/nanoparticles to be used to obtain new environmentally friendly polymeric-based materials. Although biodegradable polymers possess poorer overall properties than traditional ones, they have gained a huge interest in many industrial sectors due to their inherent biodegradability in natural environments. Therefore, several strategies have been proposed to improve their properties and extend their industrial applications. Blending strategies, as well as the development of composites and nanocomposites, have shown promising perspectives for improving their performances, emphasizing biopolymeric blend formulations and bio-based micro and nanoparticles to produce fully sustainable polymeric-based materials. The Review also summarizes recent developments in polymeric blends, composites, and nanocomposite plasticization, with a particular focus on naturally derived plasticizers and their chemical modifications to increase their compatibility with the polymeric matrices. The current state of the art of the most important bio-based and biodegradable polymers is also reviewed, mainly focusing on their synthesis and processing methods scalable to the industrial sector, such as melt and solution blending approaches like melt-extrusion, injection molding, film forming as well as solution electrospinning, among others, without neglecting their degradation processes.

Effect of Environmental pH on the Mechanics of Chitin and Chitosan: A Single-Molecule Study

Chitin and chitosan are important structural macromolecules for most fungi and marine crustaceans. The functions and application areas of the two molecules are also adjacent beyond their similar molecular structure, such as tissue engineering and food safety where solution systems are involved. However, the elasticities of chitin and chitosan in solution lack comparison at the molecular level. In this study, the single-molecule elasticities of chitin and chitosan in different solutions are investigated via atomic force microscope (AFM) based single-molecule spectroscopy (SMFS). The results manifest that the two macromolecules share the similar inherent elasticity in DOSM due to their same chain backbone. However, obvious elastic deviations can be observed in aqueous conditions. Especially, a lower pH value (acid environment) is helpful to increase the elasticity of both chitin and chitosan. On the contrary, the tendency of elastic variation of chitin and chitosan in a larger pH value (alkaline environment) shows obvious diversity, which is mainly determined by the side groups. This basic study may produce enlightenment for the design of intelligent chitin and chitosan food packaging and biomedical materials.

Exploring Novel Sensor Design Ideas through Concentration-Induced Conformational Changes in PEG Single Chains

Polyethylene glycol (PEG) is an artificial polymer with good biocompatibility and a low cost, which has a wide range of applications. In this study, the dynamic response of PEG single chains to different ion concentrations was investigated from a microscopic point of view based on single-molecule force spectroscopy, revealing unique interactions that go beyond the traditional sensor-design paradigm. Under low concentrations of potassium chloride, PEG single chains exhibit a gradual reduction in rigidity, while, conversely, high concentrations induce a progressive increase in rigidity. This dichotomy serves as the cornerstone for a profound understanding of PEG conformational dynamics under diverse ion environments. Capitalizing on the remarkable sensitivity of PEG single chains to ion concentration shifts, we introduce innovative sensor-design ideas. Rooted in the adaptive nature of PEG single chains, these sensor designs extend beyond the traditional applications, promising advancements in environmental monitoring, healthcare, and materials science.

Wetting and swelling behaviour of N-acetylated thin chitosan coatings in aqueous media

Chitosan nanocoatings (thickness range of 120-540 nm) were produced on glass, zinc and silicon substrates with dip-coating and spin coating techniques to study their pH-dependent wetting and swelling behaviour. The coatings were N-acetylated with the methanolic solution of acetic anhydride to increase the degree of acetylation from 36 % to 100 % (according to ATR-FTIR studies). The measured contact angles of Britton-Robinson (BR) buffer solutions (pH 6.0, 7.4 and 9.0) were lower on the acetylated surfaces (ca. 50°), than that of their native counterparts (ca. 70°) and does not depend on the pH. Contrary, contact angles on the native coating deteriorated 10°-15° with increasing the pH. In addition, for native coatings, the decrease of the contact angles over time also showed a pH dependence: at pH 9.0 the contact angle decreased by 7° in 10 min, while at pH 6.0 it decreased by 13° and at a much faster rate. The constraint swelling of the coatings in BR puffer solutions was studied in situ by scanning angle reflectometry. The swelling degree of the native coatings increased significantly with decreasing pH (from 250 % to 500 %) due to the increased number of protonated amino groups, while the swelling degree of acetylated coatings was ca. 160 % regardless of the pH. The barrier properties of the coatings were studied by electrochemical tests on zinc substrates. The analysis of polarization curves showed the more permeable character of the acetylated coatings despite the non-polar character of the bulk coating matrix. It can be concluded that in the case of native coatings, 49 % of the absorbed water is in bound form, which does not assist ion transport, while in the case of acetylated coatings, this value is only 33 %.