Development and Characterization of Cellulose/Iron Acetate Nanofibers for Bone Tissue Engineering Applications

Engineered eco-friendly composite membranes with superhydrophobic/hydrophilic dual-layer for DCMD system

Considerable advancements have been made in the development of hydrophobic membranes for membrane distillation (MD). Nonetheless, the environmentally responsible disposal of these membranes poses a critical concern due to their synthetic composition. Herein, an eco-friendly dual-layered biopolymer-based membrane was fabricated for water desalination. The membrane was electrospun from two bio-polymeric layers. The top hydrophobic layer comprises polycaprolactone (PCL) and the bottom hydrophilic layer from cellulose acetate (CA). Additionally, silica nanoparticles (SiO2 NPs) were electrosprayed onto the top layer of the dual-layered PCL/CA membrane to enhance the hydrophobicity. The desalination performance of the modified PCL-SiO2/CA membrane was compared with the unmodified PCL/CA membrane using a direct contact membrane distillation (DCMD) unit. Results revealed that silica remarkably improves membrane hydrophobicity. The modified PCL-SiO2/CA membrane demonstrated a significant increase in water contact angle of 152.4° compared to 119° for the unmodified membrane. In addition, PCL-SiO2/CA membrane has a smaller average pore size of 0.23 ± 0.16 μm and an exceptional liquid entry pressure of water (LEPw), which is 3.8 times higher than that of PCL/CA membrane. Moreover, PCL-SiO2/CA membrane achieved a durable permeate flux of 15.6 kg/m2.h, while PCL/CA membrane showed unstable permeate flux decreasing approximately from 25 to 12 kg/m2.h over the DCMD test time. Furthermore, the modified PCL-SiO2/CA membrane achieved a high salt rejection value of 99.97% compared to a low value of 86.2% for the PCL/CA membrane after 24 h continuous DCMD operation. In conclusion, the proposed modified PCL-SiO2/CA dual-layer biopolymeric-based membrane has considerable potential to be used as an environmentally friendly membrane for the MD process.

Engineering of Multifunctional Nanocomposite Membranes for Wastewater Treatment: Oil/Water Separation and Dye Degradation

Multifunctional membrane technology has gained tremendous attention in wastewater treatment, including oil/water separation and photocatalytic activity. In the present study, a multifunctional composite nanofiber membrane is capable of removing dyes and separating oil from wastewater, as well as having antibacterial activity. The composite nanofiber membrane is composed of cellulose acetate (CA) filled with zinc oxide nanoparticles (ZnO NPs) in a polymer matrix and dipped into a solution of titanium dioxide nanoparticles (TiO2 NPs). Membrane characterization was performed using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR), and water contact angle (WCA) studies were utilized to evaluate the introduced membranes. Results showed that membranes have adequate wettability for the separation process and antibacterial activity, which is beneficial for water disinfection from living organisms. A remarkable result of the membranes' analysis was that methylene blue (MB) dye removal occurred through the photocatalysis process with an efficiency of ~20%. Additionally, it exhibits a high separation efficiency of 45% for removing oil from a mixture of oil-water and water flux of 20.7 L.m-2 h-1 after 1 h. The developed membranes have multifunctional properties and are expected to provide numerous merits for treating complex wastewater.

Crown ether-functionalized cellulose acetate membranes with potential applications in osseointegration

Due to its inherent properties and wide availability, cellulose acetate is an extremely competitive candidate for the production of polymeric membranes. However, for best results in particular applications, membrane modification is required in order to minimize unwanted interactions and introduce novel characteristics to the pristine polymer. In this study, the surface of commercial cellulose acetate membranes was functionalized with 4'-aminobenzo-15-crown-5 ether, using a covalent bonding approach. The main goal was the improvement of the membranes biomineralization ability, thus making them prospective materials for bone regeneration applications. The proposed reaction mechanism was confirmed by XPS and NMR analysis while the presence of the functionalization agents in the membranes structure was showed by ATR FT-IR and Raman spectra. The effects of the functionalization process on the morphology, thermal and mechanical properties of the membranes were studied by SEM, TGA and tensile tests. The obtained results revealed that the cellulose acetate membranes were successfully functionalized with crown ether and provided a good understanding of the interactions that took place between the polymer and the functionalization agents. Moreover, promising results were obtained during the Taguchi biomineralization studies. SEM images, EDX mapping and XRD spectra indicating that the CA-AB15C5 membranes have a superior Ca²⁺ ions retention ability, this causing an accentuated calcium phosphate deposition on the modified polymeric fibers, compared to the neat CA membrane.

Biofunctionalization and Applications of Polymeric Nanofibers in Tissue Engineering and Regenerative Medicine

The limited ability of most human tissues to regenerate has necessitated the interventions namely autograft and allograft, both of which carry the limitations of its own. An alternative to such interventions could be the capability to regenerate the tissue in vivo.Regeneration of tissue using the innate capacity of the cells to regenerate is studied under the discipline of tissue engineering and regenerative medicine (TERM). Besides the cells and growth-controlling bioactives, scaffolds play the central role in TERM which is analogous to the role performed by extracellular matrix (ECM) in the vivo. Mimicking the structure of ECM at the nanoscale is one of the critical attributes demonstrated by nanofibers. This unique feature and its customizable structure to befit different types of tissues make nanofibers a competent candidate for tissue engineering. This review discusses broad range of natural and synthetic biodegradable polymers employed to construct nanofibers as well as biofunctionalization of polymers to improve cellular interaction and tissue integration. Amongst the diverse ways to fabricate nanofibers, electrospinning has been discussed in detail along with advances in this technique. Review also presents a discourse on application of nanofibers for a range of tissues, namely neural, vascular, cartilage, bone, dermal and cardiac.

Effect of surface structure on the antithrombogenicity performance of poly(-caprolactone)-cellulose acetate small-diameter tubular scaffolds

Small-diameter artificial blood vessels have always faced the problem of thrombosis. In this research, three types of poly(-caprolactone)-cellulose acetate (PCL-CA) composite nanofiber membranes were prepared by various collectors to make into a tubular scaffold with a 4.5-mm diameter. The collector consisted of two sizes of stainless steel wire mesh large-mesh (LM) and small-mesh (SM), respectively. There is also a random flat (RF) that acts as the third type collector. The nanofiber membrane's surface structure mimicked the collectors' surface morphology, they named LM, SM and RF scaffolds. The water contact angles of RF and LM scaffolds are 126.5° and 105.5°, and the distinct square-groove construction greatly improves the contact angle of LM. The tubular scaffolds' radial mechanical property test demonstrated that the large-mesh (LM) tubular scaffold enhanced the strain and tensile strength; the tensile strength and strain are 30 % and 148 % higher than that of the random-flat (RF) tubular scaffold, respectively. The suture retention strength value of the LM tubular scaffold was 103 % higher than that of the RF tubular scaffold. The cytotoxicity and antithrombogenicity performance were also evaluated, the LM tubular scaffold has 88 % cell viability, and the 5-min blood coagulation index (BCI) value was 89 %, which is much higher than other tubular scaffolds. The findings indicate that changing the tubular scaffold's surface morphology cannot only enhance the mechanical and hydrophilic properties but also increase cell survival and antithrombogenicity performance. Thus, the development of a small-diameter artificial blood vessel will be a big step toward solving the problem on thrombosis. Furthermore, artificial blood vessel is expected to be a candidate material for biomedical applications.

Antimicrobial Clothing Based on Electrospun Fibers with ZnO Nanoparticles

There has been a surge in interest in developing protective textiles and clothes to protect wearers from risks such as chemical, biological, heat, UV, pollution, and other environmental factors. Traditional protective textiles have strong water resistance but lack breathability and have a limited capacity to remove water vapor and moisture. Electrospun fibers and membranes have shown enormous promise in developing protective materials and garments. Textiles made up of electrospun fibers and membranes can provide thermal comfort and protection against a wide range of environmental threats. Because of their multifunctional properties, such as semi-conductivity, ultraviolet absorption, optical transparency, and photoluminescence, their low toxicity, biodegradability, low cost, and versatility in achieving diverse shapes, ZnO-based nanomaterials are a subject of increasing interest in the current review. The growing uses of electrospinning in the development of breathable and protective textiles are highlighted in this review.

On the Thermochemical Transition Depression of Cellulose Acetate Composite Membranes

Gallic acid (GA) and quercetin (QU) are two important bioactive molecules with increased biomedical interest. Cellulose acetate (CA) is a polymer derived from cellulose and is used in various applications. In this work, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) were used to study the thermal behavior of electrospun CA membranes loaded with quercetin or gallic acid. It was found that gallic acid and quercetin depress the thermochemical transition (simultaneous softening and decomposition) of CA, in a mechanism similar to that of the glass transition depression of amorphous polymers by plasticizers. The extensive hydrogen bonding, besides the well-known effect of constraining polymer's softening by keeping macromolecules close to each other, has a secondary effect on the thermochemical transition, i.e., it weakens chemical bonds and, inevitably, facilitates decomposition. This second effect of hydrogen bonding can provide an explanation for an unexpected observation of this study: CA membranes loaded with quercetin or gallic acid soften at lower temperatures; however, at the same time, they decompose to a higher extent than pure CA. Besides optimization of CA processing, the fundamental understanding of the thermochemical transition depression could lead to the design of more sustainable processes for biomass recycling and conversion.

Enhancement of critical-sized bone defect regeneration using UiO-66 nanomaterial in rabbit femurs

Background

Repair of large-sized bone defects is a challengeable obstacle in orthopedics and evoked the demand for the development of biomaterials that could induce bone repair in such defects. Recently, UiO-66 has emerged as an attractive metal–organic framework (MOF) nanostructure that is incorporated in biomedical applications due to its biocompatibility, porosity, and stability. In addition, its osteogenic properties have earned a great interest as a promising field of research. Thus, the UiO-66 was prepared in this study and assessed for its potential to stimulate and support osteogenesis in vitro and in vivo in a rabbit femoral condyle defect model. The nanomaterial was fabricated and characterized using x-ray diffraction (XRD) and transmission electron microscopy (TEM). Afterward, in vitro cytotoxicity and hemolysis assays were performed to investigate UiO-66 biocompatibility. Furthermore, the material in vitro capability to upregulate osteoblast marker genes was assessed using qPCR. Next, the in vivo new bone formation potential of the UiO-66 nanomaterial was evaluated after induction of bone defects in rabbit femoral condyles. These defects were left empty or filled with UiO-66 nanomaterial and monitored at weeks 4, 8, and 12 after bone defect induction using x-ray, computed tomography (CT), histological examinations, and qPCR analysis of osteocalcin (OC) and osteopontin (OP) expressions.

Results

The designed UiO-66 nanomaterial showed excellent cytocompatibility and hemocompatibility and stimulated the in vitro osteoblast functions. The in vivo osteogenesis was enhanced in the UiO-66 treated group compared to the control group, whereas evidence of healing of the treated bone defects was observed grossly and histologically. Interestingly, UiO-66 implanted defects displayed a significant osteoid tissue and collagen deposition compared to control defects. Moreover, the UiO-66 nanomaterial demonstrated the potential to upregulate OC and OP in vivo.

Conclusions

The UiO-66 nanomaterial implantation possesses a stimulatory impact on the healing process of critical-sized bone defects indicating that UiO-66 is a promising biomaterial for application in bone tissue engineering.

Cellulose-Based Nanofibers Processing Techniques and Methods Based on Bottom-Up Approach-A Review

In the past decades, cellulose (one of the most important natural polymers), in the form of nanofibers, has received special attention. The nanofibrous morphology may provide exceptional properties to materials due to the high aspect ratio and dimensions in the nanometer range of the nanofibers. The first feature may lead to important consequences in mechanical behavior if there exists a particular orientation of fibers. On the other hand, nano-sizes provide a high surface-to-volume ratio, which can have important consequences on many properties, such as the wettability. There are two basic approaches for cellulose nanofibers preparation. The top-down approach implies the isolation/extraction of cellulose nanofibrils (CNFs) and nanocrystals (CNCs) from a variety of natural resources, whereby dimensions of isolates are limited by the source of cellulose and extraction procedures. The bottom-up approach can be considered in this context as the production of nanofibers using various spinning techniques, resulting in nonwoven mats or filaments. During the spinning, depending on the method and processing conditions, good control of the resulting nanofibers dimensions and, consequently, the properties of the produced materials, is possible. Pulp, cotton, and already isolated CNFs/CNCs may be used as precursors for spinning, alongside cellulose derivatives, namely esters and ethers. This review focuses on various spinning techniques to produce submicrometric fibers comprised of cellulose and cellulose derivatives. The spinning of cellulose requires the preparation of spinning solutions; therefore, an overview of various solvents is presented showing their influence on spinnability and resulting properties of nanofibers. In addition, it is shown how bottom-up spinning techniques can be used for recycling cellulose waste into new materials with added value. The application of produced cellulose fibers in various fields is also highlighted, ranging from drug delivery systems, high-strength nonwovens and filaments, filtration membranes, to biomedical scaffolds.

Sustainable Applications of Nanofibers in Agriculture and Water Treatment: A Review

Natural fibers are an important source for producing polymers, which are highly applicable in their nanoform and could be used in very broad fields such as filtration for water/wastewater treatment, biomedicine, food packaging, harvesting, and storage of energy due to their high specific surface area. These natural nanofibers could be mainly produced through plants, animals, and minerals, as well as produced from agricultural wastes. For strengthening these natural fibers, they may reinforce with some substances such as nanomaterials. Natural or biofiber-reinforced bio-composites and nano–bio-composites are considered better than conventional composites. The sustainable application of nanofibers in agricultural sectors is a promising approach and may involve plant protection and its growth through encapsulating many bio-active molecules or agrochemicals (i.e., pesticides, phytohormones, and fertilizers) for smart delivery at the targeted sites. The food industry and processing also are very important applicable fields of nanofibers, particularly food packaging, which may include using nanofibers for active–intelligent food packaging, and food freshness indicators. The removal of pollutants from soil, water, and air is an urgent field for nanofibers due to their high efficiency. Many new approaches or applicable agro-fields for nanofibers are expected in the future, such as using nanofibers as the indicators for CO and NH3. The role of nanofibers in the global fighting against COVID-19 may represent a crucial solution, particularly in producing face masks.

Cellulose Acetate Nanofibers: Incorporating Hydroxyapatite (HA), HA/Berberine or HA/Moghat Composites, as Scaffolds to Enhance In Vitro Osteoporotic Bone Regeneration

The specific objective of this study was to stabilize a simple valid method to prepare pure nanorod hydroxyapatite (HA) mixed with berberine chloride (BER) and Moghat water extract (ME) as composites for incorporation into cellulose acetate (CA) nanofibers to be used as novel bone scaffolds and to determine their efficacy in bone regeneration process In Vitro. Preparation of HA/BER and HA/ME composites were performed by mixing powders using the ball-milling machine. The HA, HA/BER, and HA/ME composites at a concentration of 6.25, 12.5, 25, 50, 100, and 200 mg were mixed with CA solution (13%), then the fiber was formed using electrospinning technique. The properties of the obtained CA fibers were investigated (SEM, TEM, EDX, FTIR, TGA, water uptake, porosity, and mechanical tests). The efficacy of HA and HA composites loaded into CA nanofiber on osteoblast and osteoclast differentiation were measured by tacking ALP, osteocalcin, TRAcP, calcium, and total protein concentration. Moreover, their effects on cell differentiation (CD90 and PARP- ɣ) and death markers (GSK3b, MAPK, Wnt-5 and β-catenin) were evaluated by using ELISA and qPCR. The obtained TEM results indicated that the continuous CA and CA/HA composites electrospun fibers have ultrafine fiber diameters of about 200 nm and uniform distribution of discrete n-HA clusters throughout. In addition, hydrocortisone (HCT) was found to increase the formation of adipocytes and osteoclastic markers CD90 and p38-MAPK which indicated the bone lose process take placed. Treatment with CA loaded with HA, HA/BER or HA/ME decreased CD90, Wnt-5, PARP- ɣ, GSK3b and p38-MAPK associated elevation of osteogenic markers: ALP and osteocalcin. Moreover, HCT overexpressed RANKL and down expressed Osterix gene. Treatment with CA/HA/BER or CA/HA/ME downregulated RANKL and upregulated Osterix associated with a reduction in RANKL/OPG ratio, at p < 0.05. In conclusion, novel CA composite nanofibers (CA/HA/BER and CA/HA/ME) reversed the HCT adverse effect on osteoblast cell death through canonical and non-canonical pathways regulated by Wnt/β-catenin and Wnt/Ca(²⁺) pathways. Furthermore, our data confirmed that the novel scaffolds create a crosstalk between RUNX-2, RANKL, p38-MAPK, and Wnt signals which positively impact bone regeneration process. Treatment with CA/HA/BER is better compared to the treatment with CA/HA/ME. Nevertheless, both are considered as alternative biomaterial scaffolds with a potential for biomedical applications in the field of bone tissue engineering.

Biomimetic Strontium Substituted Calcium Phosphate Coating for Bone Regeneration

Cellulose acetate (CA)/strontium phosphate (SrP) hybrid coating has been proposed as an effective strategy to build up novel bone-like structures for bone healing since CA is soluble in most organic solvents. Strontium (Sr2+) has been reported as a potential agent to treat degenerative bone diseases due to its osteopromotive and antibacterial effects. Herein, bioactive hybrid composite SrP-based coatings (CASrP) were successfully produced for the first time. CASrP was synthesized via a modified biomimetic method (for 7—CA7dSrP, and 14 days—CA14dSrP), in which the metal ion Sr2+ was used in place of Ca2+ in the simulated body fluid. Energy-dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR) analysis confirmed the SrP incorporation chemically in the CASrP samples. Atomic absorption spectroscopy (AAS) supported EDX data, showing Sr2+ adsorption into CA, and its significant increase with the augmentation of time of treatment (ca. 92%—CA7dSrP and 96%—CA14dSrP). An increment in coating porosity and the formation of SrP crystals were evidenced by scanning electron microscopy (SEM) images. X-ray diffraction (XRD) evidenced a greater crystallinity than CA membranes and a destabilization of CA14dSrP structure compared to CA7dSrP. The composites were extremely biocompatible for fibroblast and osteoblast cells. Cell viability (%) was higher either for CA7dSrP (48 h: ca. 92% and 115%) and CA14dSrP (48 h: ca. 88% and 107%) compared to CA (48 h: ca. 70% and 51%) due to SrP formation and Sr2+ presence in its optimal dose in the culture media (4.6–9 mg·L−1). In conclusion, the findings elucidated here evidence the remarkable potential of CA7dSrP and CA14dSrP as bioactive coatings on the development of implant devices for inducing bone regeneration.

Design and Development of Cellulosic Bionanocomposites from Forestry Waste Residues for 3D Printing Applications

This paper deals with the development of cellulose nanofibres (CNFs) reinforced biopolymers for use in packaging applications. Cellulose nanofibres were extracted from sawdust by a combination of chemical and mechanical treatments. The extracted cellulose nanofibres were chemically modified (fCNFs) and characterised by Fourier Transform Infrared Spectroscopy (FTIR). Bionanocomposites were prepared from biopolymers polylactic acid/polybutylene succinate (PLA/PBS) and cellulose nanofibres by compounding in a twin-screw extruder followed by injection moulding. The developed bionanocomposites were subjected to mechanical and thermal characterisation. As part of product development, CNF-biopolymer pellets were also extruded into filaments which were then 3D printed into prototypes. This work is a successful demonstration of conversion of waste residues into value-added products, which is aligned to the principles of circular economy and sustainable development.