Upcycling Low-Quality Cotton Fibers into Mulch Gel Films in a Fast Closed Carbon Cycle.

Low-quality cotton fibers, often overlooked as low-value materials, constitute a marginalized waste stream in the cotton industry. This study endeavored to repurpose these fibers into mulch gel films, specifically exploring their efficacy in covering moisture-controlled soil beds. Through a meticulously designed series of processing methods, cellulose/glycerol film was successfully fabricated by regenerating cellulose hydrogels in N,N-dimethylacetamide/lithium chloride solutions, followed by plasticization in glycerol/water solutions and hot pressing. The film was then employed to cover soil beds for a duration of up to 252 days, followed by soil burial assessments. Despite expectations of degradation, the film maintained structural integrity throughout the soil covering period but underwent complete biodegradation after 80 days of soil burial, thereby completing a closed carbon cycle. Intriguingly, both tensile strength and modulus exhibited no diminishment but instead increased after soil covering, contrary to expectations given the usual role of degradation. Mechanistic insights revealed that the removal of glycerol contributed to the mechanical enhancement, while microbial activity predominately decomposed the amorphous regions in soil covering and targeted the crystalline portions in soil burial, elucidating the main biodegradation mechanisms. In summary, this study presents, for the first time, the potential of upcycling low-quality cotton fibers into high-value mulch gel films for agricultural practices within a closed carbon cycle.

Soil burial-induced degradation of cellulose films in a moisture-controlled environment.

In this study, the biodegradability of cellulose films was evaluated in controlled-moisture soil environments. The films were prepared from low-quality cotton fibers through dissolution in DMAc/LiCl, casting, regeneration, glycerol plasticization, and hot-pressing. Two soil burial degradation experiments were conducted in August 2020 (11th August to 13th October) and March 2021 (24th March to 24th July) under controlled moisture conditions to assess the biodegradation behavior of cellulose films. The films were retrieved from soil beds at seven-day intervals, and morphological and physicochemical changes in the films were investigated. The results indicated that the cellulose films exhibited gradual changes starting on Day 7 and major changes after Day 35. Stereomicroscopy images showed the growth and development of fungal mycelia on the surface of the films, and FTIR spectroscopy confirmed the presence of biomolecules originating from microorganisms. The tensile strength and elongation of cellulose films were significantly reduced by 64% and 96% in the first experiment and by 40% and 94% in the second experiment, respectively, during the degradation period. Degradation also significantly impacted the thermal stability (14% and 16.5% reduction, respectively, in the first and second studies) of the films. The cellulose-based films completely degraded within 63 days in late summer and 112 days in spring. This study demonstrates that, unlike synthetic plastics, films prepared from low-quality cotton fibers can easily degrade in the natural environment.

Effect of Microwave Plasma Pre-Treatment on Cotton Cellulose Dissolution.

The utilization of cellulose to its full potential is constrained by its recalcitrance to dissolution resulting from the rigidity of polymeric chains, high crystallinity, high molecular weight, and extensive intra- and intermolecular hydrogen bonding network. Therefore, pretreatment of cellulose is usually considered as a step that can help facilitate its dissolution. We investigated the use of microwave oxygen plasma as a pre-treatment strategy to enhance the dissolution of cotton fibers in aqueous NaOH/Urea solution, which is considered to be a greener solvent system compared to others. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, and Powder X-ray Diffraction analyses revealed that plasma pretreatment of cotton cellulose leads to physicochemical changes of cotton fibers. Pretreatment of cotton cellulose with oxygen plasma for 20 and 40 min resulted in the reduction of the molecular weight of cellulose by 36% and 60% and crystallinity by 16% and 25%, respectively. This reduction in molecular weight and crystallinity led to a 34% and 68% increase in the dissolution of 1% (w/v) cotton cellulose in NaOH/Urea solvent system. Thus, treating cotton cellulose with microwave oxygen plasma alters its physicochemical properties and enhanced its dissolution.

Cryogenic grinding of cotton fiber cellulose: The effect on physicochemical properties.

The study evaluated the effect of cryogrinding, a relatively new, cost-effective, and sustainable mechanical treatment method, on physicochemical properties of two different micronaire (3.6- and 5.3-) cotton fiber cellulose. Native (type I), mercerized (type II), and acidulated cellulose were subjected to cryogrinding for 48 and 96 min, and their physicochemical properties were investigated. The results demonstrated that cryogrinding resulted in partial amorphization of native and mercerized celluloses, particle size decrease, and a slight reduction of T50%. Importantly, degree of polymerization (DP) of native cellulose reduced significantly: more than two-fold after 12 cycles and more than three-fold after 24 cycles of cryogrinding. No difference in properties was found between 3.6- and 5.3-micronaire cellulose. Advantageous impacts of cryogrinding found in this work will help signify the potential of this technique in cellulose processing and enable the identification of areas for future development.

Role of Sporopollenin Shell Interfacial Properties in Protein Adsorption.

Sporopollenin shells isolated from natural pollen grains have received attention in translational and applied research in diverse fields of drug delivery, vaccine delivery, and wastewater remediation. However, little is known about the sporopollenin shell's potential as an adsorbent. Herein, we have isolated sporopollenin shells from four structurally diverse pollen species, black walnut, marsh elder, mugwort, and silver birch, to study protein adsorption onto sporopollenin shells. We investigated three major interfacial properties, surface area, surface functional groups, and surface charge, to elucidate the mechanism of protein adsorption onto sporopollenin shells. We showed that sporopollenin shells have a moderate specific surface area (<12 m2/g). Phosphoric acid and potassium hydroxide treatments that were used to isolate sporopollenin shells from natural pollen grains also result in the functionalization of sporopollenin shell surfaces with ionizable groups of carboxylic acid and carboxylate salt. As a result, sporopollenin shells exhibit a negative ζ potential in the range of -75 to -82 mV at pH 10 when dispersed in water. The ζ potentials of sporopollenin shells remain negative in the pH range of 2.5-11, with the absolute value of ζ potential showing a decrease with the decrease in pH. The negative surface charge promotes the adsorption of protein onto the sporopollenin shell via electrostatic interaction. Despite having a moderate surface area, sporopollenin shells adsorb a significant amount of lysozyme (145-340 µg lysozyme per mg of sporopollenin shells). Lysozyme adsorption onto sporopollenin shells alters the surface, and the surface charge becomes positive at acidic pH. Overall, this study demonstrates the potential of sporopollenin shells to adsorb proteins, highlights the critical role of sporopollenin shell's interfacial properties in protein adsorption, and identifies the mechanism of protein adsorption on sporopollenin shells.

Utilization of Cellulose to Its Full Potential: A Review on Cellulose Dissolution, Regeneration, and Applications.

As the most abundant natural polymer, cellulose is a prime candidate for the preparation of both sustainable and economically viable polymeric products hitherto predominantly produced from oil-based synthetic polymers. However, the utilization of cellulose to its full potential is constrained by its recalcitrance to chemical processing. Both fundamental and applied aspects of cellulose dissolution remain active areas of research and include mechanistic studies on solvent-cellulose interactions, the development of novel solvents and/or solvent systems, the optimization of dissolution conditions, and the preparation of various cellulose-based materials. In this review, we build on existing knowledge on cellulose dissolution, including the structural characteristics of the polymer that are important for dissolution (molecular weight, crystallinity, and effect of hydrophobic interactions), and evaluate widely used non-derivatizing solvents (sodium hydroxide (NaOH)-based systems, N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl), N-methylmorpholine-N-oxide (NMMO), and ionic liquids). We also cover the subsequent regeneration of cellulose solutions from these solvents into various architectures (fibers, films, membranes, beads, aerogels, and hydrogels) and review uses of these materials in specific applications, such as biomedical, sorption, and energy uses.

Production and Surface Modification of Cellulose Bioproducts.

Petroleum-based synthetic plastics play an important role in our life. As the detrimental health and environmental effects of synthetic plastics continue to increase, the renewable, degradable and recyclable properties of cellulose make subsequent products the "preferred environmentally friendly" alternatives, with a small carbon footprint. Despite the fact that the bioplastic industry is growing rapidly with many innovative discoveries, cellulose-based bioproducts in their natural state face challenges in replacing synthetic plastics. These challenges include scalability issues, high cost of production, and most importantly, limited functionality of cellulosic materials. However, in order for cellulosic materials to be able to compete with synthetic plastics, they must possess properties adequate for the end use and meet performance expectations. In this regard, surface modification of pre-made cellulosic materials preserves the chemical profile of cellulose, its mechanical properties, and biodegradability, while diversifying its possible applications. The review covers numerous techniques for surface functionalization of materials prepared from cellulose such as plasma treatment, surface grafting (including RDRP methods), and chemical vapor and atomic layer deposition techniques. The review also highlights purposeful development of new cellulosic architectures and their utilization, with a specific focus on cellulosic hydrogels, aerogels, beads, membranes, and nanomaterials. The judicious choice of material architecture combined with a specific surface functionalization method will allow us to take full advantage of the polymer's biocompatibility and biodegradability and improve existing and target novel applications of cellulose, such as proteins and antibodies immobilization, enantiomers separation, and composites preparation.

Supercritical carbon dioxide decellularization of plant material to generate 3D biocompatible scaffolds.

The use of plant-based biomaterials for tissue engineering has recently generated interest as plant decellularization produces biocompatible scaffolds which can be repopulated with human cells. The predominant approach for vegetal decellularization remains serial chemical processing. However, this technique is time-consuming and requires harsh compounds which damage the resulting scaffolds. The current study presents an alternative solution using supercritical carbon dioxide (scCO2). Protocols testing various solvents were assessed and results found that scCO2 in combination with 2% peracetic acid decellularized plant material in less than 4 h, while preserving plant microarchitecture and branching vascular network. The biophysical and biochemical cues of the scCO2 decellularized spinach leaf scaffolds were then compared to chemically generated scaffolds. Data showed that the scaffolds had a similar Young's modulus, suggesting identical stiffness, and revealed that they contained the same elements, yet displayed disparate biochemical signatures as assessed by Fourier-transform infrared spectroscopy (FTIR). Finally, human fibroblast cells seeded on the spinach leaf surface were attached and alive after 14 days, demonstrating the biocompatibility of the scCO2 decellularized scaffolds. Thus, scCO2 was found to be an efficient method for plant material decellularization, scaffold structure preservation and recellularization with human cells, while performed in less time (36 h) than the standard chemical approach (170 h).

Physical and Biochemical Characterization of Chemically Treated Pollen Shells for Potential Use in Oral Delivery of Therapeutics.

Allergen-free pollen shells obtained from natural pollen grains have recently attracted attention as microcapsules for oral therapeutic delivery. We have recently developed a chemical treatment method that enables successful retrieval of hollow pollen shells from diverse species. A comprehensive characterization is critical to characterize the effects of chemical treatment which will not only benchmark the pollen treatment process but can also lay the foundation of quality control procedures to check allergen-removal efficiency during pollen treatment. Therefore, in this study, we followed the effects of chemical treatment on 4 different pollen species using electron microscopy, elemental analysis, gel electrophoresis, confocal microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. These analyses revealed that acetone treatment removed lipids from the pollen surface. Phosphoric acid treatment removed proteins and nucleic acids from the pollen core and transformed esters into carboxylic acids. Potassium hydroxide hydrolysis changed carbohydrate composition of the pollen wall. Chemically treated pollen shells exhibited hydroxyl and carboxyl functional groups on their surface. Overall, we propose that confocal microscopy could be used as a rapid scanning technique to visualize the removal of biomolecules, whereas Fourier-transform infrared combined with gel electrophoresis could be used as a more objective approach for analysis and benchmarking.

Optimization and validation of cryostat temperature conditions for trans-reflectance mode FTIR microspectroscopic imaging of biological tissues.

In Fourier transform infrared (FTIR) microspectrocopy, the tissue preparation method is crucial, especially how the tissue is cryo-sectioned prior to the imaging requires special consideration. Having a temperature difference between the cutting blade and the specimen holder of the cryostat greatly affects the quality of the sections. Therefore, we have developed an optimal protocol for cryo-sectioning of biological tissues by varying the temperature of both the cutting blade and the specimen holder. Using this protocol, we successfully cryo-sectioned four different difficult-to-section tissues including white adipose tissue (WAT), brown adipose tissue (BAT), lung, and liver. The optimal temperatures that required to be maintained at the cutting blade and the specimen holder for the cryo-sectioning of WAT, BAT, lung, and liver are (-25, -20 °C), (-25, -20 °C), (-17, -13 °C) and (-15, -5 °C), respectively. The optimized protocol developed in this study produced high quality cryo-sections with sample thickness of 8-10 µm, as well as high quality trans-reflectance mode FTIR microspectroscopic images for the tissue sections. •Use of cryostat technique to make thin sections of biological samples for FTIR microspectroscopy imaging.•Optimized cryostat temperature conditions by varying the temperatures at the cutting blade and specimen holder to obtain high quality sections of difficult-to-handle tissues.•FTIR imaging is used to obtain chemical information from cryo-sectioned samples with no interference of the conventional paraffin-embedding agent and chemicals.