Study on preparation and performance of PEG-based polyurethane foams modified by the chitosan with different molecular weight

Enhancing stability of liposomes using high molecular weight chitosan to promote antioxidative stress effects and lipid-lowering activity of encapsulated lutein in vivo and in vitro

Lutein is an antioxidant with multiple beneficial functions. However, its therapeutic potential is hampered by its low water solubility and bioavailability. The goal of this study is to compare the stability of lutein-loaded liposomes (Lu-lip) and low (LC)/high molecular weight (HC) chitosan-coated Lu-lip, along with their antioxidant capacity using H2O2-induced HepG2 cells and their lipid-lowering activity using high-fat diet mice. Both LC and HC reduced the lutein degradation rate by 17.5 % and 26.72 % in a challenging environment at pH 6 and T = 4 °C. Compared to LC, the HC coating improved the size- and zeta-potential-stability of Lu-lip at 5 < pH < 7, with the best performance at pH 6. The HC coating prolonged the lutein release profile, increased the cellular uptake of Lu-lip, and reduced the reactive oxygen species (ROS) levels and the H2O2-induced necrotic cell ratios by increasing the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Animal experiments have shown that oral administration of LC and HC coated Lu-lip can significantly reduce body weight levels, total triglycerides (TG), total cholesterol (TC), and non-high-density lipoprotein (n-HDL-C) in high-fat diet mice while significantly increasing the levels of CAT, SOD and GSH-Px in the liver of mice. LC and HC coated Lu-lip can reduce fat accumulation in the liver and epididymal adipose tissue.

Recent Advances in Tailored Fabrication and Properties of Biobased Self-Healing Polyurethane

With the emergence of challenges in the environmental degradation and resource scarcity fields, the research of biobased self-healing polyurethane (BSPU) has become a prevailing trend in the technology of the polyurethane industry and a promising direction for developing biomass resources. Here, the production of BSPU from lignocellulose, vegetable oil, chitosan, collagen, and coumarin is classified, and the principles of designing polyurethane based on compelling examples using the latest methods and current research are summarized. Moreover, the impact of biomass materials on self-healing and mechanical properties, as well as the tailored performance method, are presented in detail. Finally, the applications of BSPU in biomedicine, sensors, coatings, etc. are also summarized, and the possible challenges and development prospects are explored to helpfully make progress in the development of BSPU. These findings demonstrate valuable references and practical significance for future BSPU research.

Polyols and Polyurethane Foams Based on Water-Soluble Chitosan

At present, majority of polyols used in the synthesis of polyurethane foams are of petrochemical origin. The decreasing availability of crude oil imposes the necessity to convert other naturally existing resources, such as plant oils, carbohydrates, starch, or cellulose, as substrates for polyols. Within these natural resources, chitosan is a promising candidate. In this paper, we have attempted to use biopolymeric chitosan to obtain polyols and rigid polyurethane foams. Four methods of polyol synthesis from water-soluble chitosan functionalized by reactions of hydroxyalkylation with glycidol and ethylene carbonate with variable environment were elaborated. The chitosan-derived polyols can be obtained in water in the presence of glycerol or in no-solvent conditions. The products were characterized by IR, 1H-NMR, and MALDI-TOF methods. Their properties, such as density, viscosity, surface tension, and hydroxyl numbers, were determined. Polyurethane foams were obtained from hydroxyalkylated chitosan. The foaming of hydroxyalkylated chitosan with 4,4′-diphenylmethane diisocyanate, water, and triethylamine as catalysts was optimized. The four types of foams obtained were characterized by physical parameters such as apparent density, water uptake, dimension stability, thermal conductivity coefficient, compressive strength, and heat resistance at 150 and 175 °C. It has been found that the obtained materials had most of the properties similar to those of classic rigid polyurethane foams, except for an increased thermal resistance up to 175 °C. The chitosan-based polyols and polyurethane foams obtained from them are biodegradable: the polyol is completely biodegraded, while the PUF obtained thereof is 52% biodegradable within 28 days in the soil biodegradation oxygen demand test.

Stretchable and biodegradable chitosan-polyurethane-cellulose nanofiber composites as anisotropic materials

Chitosan is a naturally derived biodegradable polymer with abundancy, sustainability, and ease of chemical modification. Polyurethanes are a family of elastic biocompatible polymers, and composites of polyurethanes have versatile properties and applications. Chitosan-polyurethane composites were recently developed but had insufficient strength and limited stretchability. In the current study, cellulose nanofibers (CNFs) were integrated in chitosan-polyurethane composites to prepare stretchable and anisotropic materials. A biodegradable polyurethane was first synthesized, end-capped with aldehyde to become dialdehyde polyurethane (DP) nanoparticles, and added with CNFs to prepare the DP-CNF composite crosslinker (DPF). The waterborne DPF crosslinker was then blended with chitosan solution to make polyurethane-CNF-chitosan (DPFC) composites. After blending, DPFC may form hydrogel in ~33 min at room temperature, which confirmed crosslinking. Composite films cast and dried from the blends showed good elongation (~420.2 %) at 60 °C. Anisotropic films were then generated by tension annealing with pre-strain. The annealed films with 200 % pre-strain exhibited large elastic anisotropy with ~4.9 anisotropic ratio. In situ SAXS/WAXS analyses unveiled that rearrangement and alignment of the microstructure during tension annealing accounted for the anisotropy. The anisotropic composite films had the ability to orient the growth of neural stem cells and showed the potential for biomimetic and tissue engineering applications.

Effects of Neutralization on the Physicochemical, Mechanical, and Biological Properties of Ammonium-Hydroxide-Crosslinked Chitosan Scaffolds

It has been reported that chitosan scaffolds, due to their physicochemical properties, stimulate cell proliferation in different tissues of the human body. This study aimed to determine the physicochemical, mechanical, and biological properties of chitosan scaffolds crosslinked with ammonium hydroxide, with different pH values, to better understand cell behavior depending on the pH of the biomaterial. Scaffolds were either neutralized with sodium hydroxide solution, washed with distilled water until reaching a neutral pH, or kept at alkaline pH. Physicochemical characterization included scanning electron microscopy (SEM), elemental composition (EDX), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), and mechanical testing. In vitro cytotoxicity was assessed via dental-pulp stem cells' (DPSCs') biocompatibility. The results revealed that the neutralized scaffolds exhibited better cell proliferation and morphology. It was concluded that the chitosan scaffolds' high pH (due to residual ammonium hydroxide) decreases DPSCs' cell viability.

Recent advances in the polyurethane-based adsorbents for the decontamination of hazardous wastewater pollutants

The pollution of aquatic systems with noxious organic and inorganic contaminants is a challenging problem faced by most countries. Water bodies are contaminated with diverse inorganic and organic pollutants originating from various diffuse and point sources, including industrial sectors, agricultural practices, and domestic wastes. Such hazardous water pollutants tend to accumulate in the environmental media including living organisms, thereby posing significant environmental health risks. Therefore, the remediation of wastewater pollutants is a priority. Adsorption is considered as the most efficient technique for the removal of pollutants in aqueous systems, and the deployment of suitable adsorbents plays a vital role for the sustainable application of the technique. The present review gives an overview of polyurethane foam (PUF) as an adsorbent, the synthesis approaches of polyurethane, and characterization aspects. Further emphasis is on the preparation of the various forms of polyurethane adsorbents, and their potential application in the removal of various challenging water pollutants. The removal mechanisms, including adsorption kinetics, isotherms, thermodynamics, and electrostatic and hydrophobic interactions between polyurethane adsorbents and pollutants are discussed. In addition, regeneration, recycling and disposal of spent polyurethane adsorbents are reported. Finally, key knowledge gaps on synthesis, characterization, industrial applications, life cycle analysis, and potential health risks of polyurethane adsorbents are discussed.

Two Fascinating Polysaccharides: Chitosan and Starch. Some Prominent Characterizations for Applying as Eco-Friendly Food Packaging and Pollutant Remover in Aqueous Medium. Progress in Recent Years: A Review

The call to use biodegradable, eco-friendly materials is urgent. The use of biopolymers as a replacement for the classic petroleum-based materials is increasing. Chitosan and starch have been widely studied with this purpose: to be part of this replacement. The importance of proper physical characterization of these biopolymers is essential for the intended application. This review focuses on characterizations of chitosan and starch, approximately from 2017 to date, in one of their most-used applications: food packaging for chitosan and as an adsorbent agent of pollutants in aqueous medium for starch.

Application of Shrimp Waste for the Synthesis of Polyurethane–Chitosan Materials with Potential Use in Sorption of Oil Micro-Spills in Water Treatment

Shrimp waste is a common waste in seafood processing. It is used as part of the fish meal which is added to feed. Bearing in mind the Green Deal and sustainability development, it was proposed to use northern prawn shells to obtain chitosan (Ch), which could then be used for polyurethane (PUR) modification. In ports, oil micro-spills often flow into the waters of gulfs and, consequently, into the sea. Systematic chemical and petroleum water pollution may pose a threat to flora and fauna. In this study, chitosan, which was obtained from shrimp shells, was used to synthesize polyurethane–chitosan foams (PUR+Ch) with different chitosan concentrations. Selected physico-chemical and sorption properties in relation to oil and water of these materials were determined. It was found that the amount of Ch added to the foam affected its morphology, hardness, density, and thermal and sorption properties. PUR foam with a 1.5% weight of Ch was characterized as having the highest water and oil sorption. The advantages of the tested material as an innovative product with potentially significant proecological values were estimated using strengths–weaknesses–opportunities–threats (SWOT) analysis. The conducted preliminary research made it possible to demonstrate the use of these materials in the processes of water treatment with the mentioned micropollutants.

Advances in Injectable and Self-healing Polysaccharide Hydrogel Based on the Schiff Base Reaction

Injectable hydrogel possesses great application potential in disease treatment and tissue engineering, but damage to gel often occurs due to the squeezing pressure from injection devices and the mechanical forces from limb movement, and leads to the rapid degradation of gel matrix and the leakage of the load material. The self-healing injectable hydrogels can overcome these drawbacks via automatically repairing gel structural defects and restoring gel function. The polysaccharide hydrogels constructed through the Schiff base reaction own advantages including simple fabrication, injectability, and self-healing under physiological conditions, and therefore have drawn extensive attention and investigation recently. In this short review, the preparation and self-healing properties of the polysaccharide hydrogels that is established on the Schiff base reaction are focused on and their biological applications in drug delivery and cell therapy are discussed.

Gamma radiation-induced grafting of poly(2-aminoethyl methacrylate) onto chitosan: A comprehensive study of a polyurethane scaffold intended for skin tissue engineering

A novel brush-like poly(2-aminoethyl methacrylate) (PAEMA) was grafted onto chitosan (CS) through gamma radiation-induced polymerization. The copolymer (CS-g-PAEMA) was used to prepare a sodium acetate leached poly(urethane-urea) scaffold. The above derivatives were developed, synthesized, and characterized to meet the specific characteristics of biomaterials. The results revealed that this method is an easy and successful route for grafting PAEMA onto CS. The feasibility of preparing a CS-g-PAEMA polyurethane foam was confirmed by mechanical, morphometric, spectroscopic, and cytotoxic studies. The scaffold showed high biocompatibility both in vitro and in vivo. The first experiment proved that CS-based polyurethane efficiently allows the dynamic culturing of human fibroblast cells. Additionally, an in vivo study in a murine model indicated a complete integration of the scaffold to surrounding subcutaneous tissue as supported by the histological and histochemical assessments. The aforementioned results support the use of CS-g-PAEMA poly(saccharide-urethane) as a model of in vitro-engineered skin.

The Effect of Chitosan on the Chemical Structure, Morphology, and Selected Properties of Polyurethane/Chitosan Composites

Materials science is an interdisciplinary area of studies. This science focuses on the influence of the physico-chemical properties of materials on their application in human everyday lives. The materials’ synthesis should be developed in accordance with sustainable development. Polyurethanes (PUR) represent a significant consumption of plastic in the world. Modification of PUR, e.g., with polysaccharide of natural origin (chitosan, Chit), should have a positive effect on their functional properties and degradability in the natural environment. The basic parameters affecting the scope and direction of changes are the size and quantity of the chitosan particles. The impact assessment of chitosan on the chemical structure, morphology, thermal properties, crystallinity, mechanical properties, flammability, water sorption, adsorption properties, degradability, and biological activity of PUR/Chit composites (without other additives) is discussed in this article. To the best of our knowledge, recent literature does not contain a study discussing the direct impact of the presence of chitosan in the structure of PUR/Chit composite on its properties, regardless of the intended uses. This paper provides an overview of publications, which presents the results of a study on the effect of adding chitosan in polyurethane/chitosan composites without other additives on the properties of polyurethane.

Predicted Studies of Branched and Cross-Linked Polyurethanes Based on Polyhydroxybutyrate with Polycaprolactone Triol in Soft Segments

The number of cross-links in the non-linear polyurethane structure is the basic factor affecting its properties. Selected properties of aliphatic polyurethanes with soft segments made of different amounts of polycaprolactonetriol, polycaprolactonediol and synthetic, telechelic poly([R,S]-3-hydroxybutyrate) were determined. On the basis of changes in polyurethane properties, the correlation between these properties and the construction of soft segments was found. The structure of polyurethanes, their morphology, hydrophilicity, thermal and mechanical properties were examined. These properties were changed linearly up to 15% content of polycaprolactonetriol in soft segments. A further increase in the amount of triol causes that these properties are mainly determined by the high number of cross-links.