Glucomannan based polyurethanes: A critical short review of recent advances and future perspectives

Konjac glucomannan: A comprehensive review of its extraction, health benefits, and pharmaceutical applications

Konjac glucomannan (KG) is a dietary fiber hydrocolloid derived from Amorphophallus konjac tubers and is widely utilized as a food additive and dietary supplement. As a health-conscious choice, purified KG, along with konjac flour and KG-infused diets, have gained widespread acceptance in Asian and European markets. An overview of the chemical composition and structure of KG is given in this review, along with thorough explanations of the processes used in its extraction, production, and purification. KG has been shown to promote health by reducing glucose, cholesterol, triglyceride levels, and blood pressure, thereby offering significant weight loss advantages. Furthermore, this review delves into the extensive health benefits and pharmaceutical applications of KG and its derivatives, emphasizing its prebiotic, anti-inflammatory, and antitumor activities. This study highlights how these natural polysaccharides can positively influence health, underscoring their potential in various biomedical applications.

Recent Advances in Environment-Friendly Polyurethanes from Polyols Recovered from the Recycling and Renewable Resources: A Review

Polyurethane (PU) is among the most universal polymers and has been extensively applied in many fields, such as construction, machinery, furniture, clothing, textile, packaging and biomedicine. Traditionally, as the main starting materials for PU, polyols deeply depend on petroleum stock. From the perspective of recycling and environmental friendliness, advanced PU synthesis, using diversified resources as feedstocks, aims to develop versatile products with excellent properties to achieve the transformation from a fossil fuel-driven energy economy to renewable and sustainable ones. This review focuses on the recent development in the synthesis and modification of PU by extracting value-added monomers for polyols from waste polymers and natural bio-based polymers, such as the recycled waste polymers: polyethylene terephthalate (PET), PU and polycarbonate (PC); the biomaterials: vegetable oil, lignin, cashew nut shell liquid and plant straw; and biomacromolecules: polysaccharides and protein. To design these advanced polyurethane formulations, it is essential to understand the structure-property relationships of PU from recycling polyols. In a word, this bottom-up path provides a material recycling approach to PU design for printing and packaging, as well as biomedical, building and wearable electronics applications.

Lignocellulosic Materials for the Production of Biofuels, Biochemicals and Biomaterials and Applications of Lignocellulose-Based Polyurethanes: A Review

The present review is devoted to the description of the state-of-the-art techniques and procedures concerning treatments and modifications of lignocellulosic materials in order to use them as precursors for biomaterials, biochemicals and biofuels, with particular focus on lignin and lignin-based products. Four different main pretreatment types are outlined, i.e., thermal, mechanical, chemical and biological, with special emphasis on the biological action of fungi and bacteria. Therefore, by selecting a determined type of fungi or bacteria, some of the fractions may remain unaltered, while others may be decomposed. In this sense, the possibilities to obtain different final products are massive, depending on the type of microorganism and the biomass selected. Biofuels, biochemicals and biomaterials derived from lignocellulose are extensively described, covering those obtained from the lignocellulose as a whole, but also from the main biopolymers that comprise its structure, i.e., cellulose, hemicellulose and lignin. In addition, special attention has been paid to the formulation of bio-polyurethanes from lignocellulosic materials, focusing more specifically on their applications in the lubricant, adhesive and cushioning material fields. High-performance alternatives to petroleum-derived products have been reported, such as adhesives that substantially exceed the adhesion performance of those commercially available in different surfaces, lubricating greases with tribological behaviour superior to those in lithium and calcium soap and elastomers with excellent static and dynamic performance.

Multiscale structures and rheology of bisurea-loaded resins for anti-sagging applications

Four representative bisurea molecules (HDI-BA, MDI-BA, TDI-BA, and IPDI-BA) were synthesized and dispersed simultaneously by reacting benzylamine (BA) with various types of diisocyanates in a polyester/ortho-xylene resin medium to produce bisurea-loaded resins (BLRs) for anti-sagging application with paints and coating materials. These bisurea molecules are symmetric and differ only in the central spacer unit, thereby presenting an ideal and simplest model system to delve into the structure-performance relationship. The multiscale structural features arising from self-assembly in each of the BLRs were scrutinized using the combination of multi-angular dynamic light scattering (DLS), small-angle light/X-ray scattering (SALS/SAXS), rheology, and scanning electron/optical microscopy (SEM/OM) characterization. All four BLRs were revealed to foster micron-sized, mostly sphere-like agglomerates, with distinct hierarchical structures that correlate well with their thixotropic and anti-sagging performances. Three BLRs (HDI-BA, MDI-BA, and TDI-BA) produce similar rod-like packing units (10 × 1 × 1 nm³), with only one exception (IPDI-BA) that produces a spherical packing unit (2 nm in diameter). However, the bulk feature of the agglomeration state, which dictates the thixotropic and anti-sagging properties, cannot be readily foreseen from the chemical structure or elementary packing unit of a bisurea. The present findings, while confirming the importance of optimum molecular design that controls the early-stage self-assembly behavior of a bisurea in resin media, highlight the necessity of resolving detailed (multiscale) structural features in order to establish the full structure-performance relationship imperatively needed for like material systems and applications.

Preparation and characterization of guar gum based polyurethanes

Guar gum (plant-based polysaccharide) is a promising candidate with immense potential. It is used as emulsifier, thickener, stabilizer, and as binding agent in many industries. In the present project, it was planned to synthesize guar gum based polyurethanes by varying the amount of guar gum. Guar gum (GG) was used along with hydroxyl-terminated polybutadiene (HTPB) as soft segment, which was then reacted with isophorone diisocyanate (IPDI) to form PU pre-polymers. In last step, these -NCO terminated pre-polymers were extended with 1,4 butane diol as chain extender. The prepared polyurethane samples were then characterized by using FTIR, solid-state ¹HNMR and X-ray diffraction (XRD). Thermal behavior of the samples was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results indicated that the incorporation of guar gum in PU backbone improved its thermal behavior and crystallinity.

Mannan-Based Nanodiagnostic Agents for Targeting Sentinel Lymph Nodes and Tumors

Early detection of metastasis is crucial for successful cancer treatment. Sentinel lymph node (SLN) biopsies are used to detect possible pathways of metastasis spread. We present a unique non-invasive diagnostic alternative to biopsy along with an intraoperative imaging tool for surgery proven on an in vivo animal tumor model. Our approach is based on mannan-based copolymers synergistically targeting: (1) SLNs and macrophage-infiltrated solid tumor areas via the high-affinity DC-SIGN (dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin) receptors and (2) tumors via the enhanced permeability and retention (EPR) effect. The polymer conjugates were modified with the imaging probes for visualization with magnetic resonance (MR) and fluorescence imaging, respectively, and with poly(2-methyl-2-oxazoline) (POX) to lower unwanted accumulation in internal organs and to slow down the biodegradation rate. We demonstrated that these polymer conjugates were successfully accumulated in tumors, SLNs and other lymph nodes. Modification with POX resulted in lower accumulation not only in internal organs, but also in lymph nodes and tumors. Importantly, we have shown that mannan-based polymer carriers are non-toxic and, when applied to an in vivo murine cancer model, and offer promising potential as the versatile imaging agents.

Recent advances in tissue engineering scaffolds based on polyurethane and modified polyurethane

Organ repair, regeneration, and transplantation are constantly in demand due to various acute, chronic, congenital, and infectious diseases. Apart from traditional remedies, tissue engineering (TE) is among the most effective methods for the repair of damaged tissues via merging the cells, growth factors, and scaffolds. With regards to TE scaffold fabrication technology, polyurethane (PU), a high-performance medical grade synthetic polymer and bioactive material has gained significant attention. PU possesses exclusive biocompatibility, biodegradability, and modifiable chemical, mechanical and thermal properties, owing to its unique structure-properties relationship. During the past few decades, PU TE scaffold bioactive properties have been incorporated or enhanced with biodegradable, electroactive, surface-functionalised, ayurvedic products, ceramics, glass, growth factors, metals, and natural polymers, resulting in the formation of modified polyurethanes (MPUs). This review focuses on the recent advances of PU/MPU scaffolds, especially on the biomedical applications in soft and hard tissue engineering and regenerative medicine. The scientific issues with regards to the PU/MPU scaffolds, such as biodegradation, electroactivity, surface functionalisation, and incorporation of active moieties are also highlighted along with some suggestions for future work.

Protective effect of three glucomannans from different plants against DSS induced colitis in female BALB/c mice

Glucomannans (GMs) from diverse natural plants have great potentiality in enhancing the host immune system.

Degradability of cross-linked polyurethanes based on synthetic polyhydroxybutyrate and modified with polylactide

In many areas of application of conventional non-degradable cross-linked polyurethanes (PUR), there is a need for their degradation under the influence of specific environmental factors. It is practiced by incorporation of sensitive to degradation compounds (usually of natural origin) into the polyurethane structure, or by mixing them with polyurethanes. Cross-linked polyurethanes (with 10 and 30%wt amount of synthetic poly([R,S]-3-hydroxybutyrate) (R,S-PHB) in soft segments) and their physical blends with poly([d,l]-lactide) (PDLLA) were investigated and then degraded under hydrolytic (phosphate buffer solution) and oxidative (CoCl₂/H₂O₂) conditions. The rate of degradation was monitored by changes of samples mass, morphology of surface and their thermal properties. Despite the small weight losses of samples, the changes of thermal properties of polymers and topography of their surface indicated that they were susceptible to gradual degradation under oxidative and hydrolytic conditions. Blends of PDLLA and polyurethane with 30 wt% of R,S-PHB in soft segments and PUR/PDLLA blends absorbed more water and degraded faster than polyurethane with low amount of R,S-PHB.

Manufacture and Properties of Glucomannans and Glucomannooligosaccharides Derived from Konjac and Other Sources

Glucomannans (GM) are polymers that can be found in natural resources, such as tubers, bulbs, roots, and both hard- and softwoods. In fact, mannan-based polysaccharides represent the largest hemicellulose fraction in softwoods. In addition to their structural functions and their role as energy reserve, they have been assessed for their healthy applications, including their role as new source of prebiotics. This paper summarizes the scientific literature regarding the manufacture and functional properties of GM and their hydrolysis products with a special focus on their prebiotic activity.