Ana Paula Gomes

Aim: To compare the geometric, metallurgical and mechanical characteristics of NiTi endodontic instruments with the same nominal design and dimensions but manufactured under three different single heat‐treatment conditions and one Dual Wire heat‐treatment configuration. Methodology: A total of 240 NiTi instruments were divided into four groups ( n = 60): GOLD, PURPLE, BLUE, each subjected to a distinct single heat‐treatment condition, and DUAL WIRE, incorporating two different heat treatments within the same instrument. Geometric and surface characteristics were assessed by optical and scanning electron microscopy. Elemental composition was evaluated by energy‐dispersive X‐ray spectroscopy, and phase‐transformation temperatures by differential scanning calorimetry using coronal and tip segments. Mechanical performance was assessed by cyclic fatigue, torsional, bending, buckling and cutting tests. Data were analysed using one‐way ANOVA and Tukey's post hoc test ( α = 5%). Results: The four groups showed comparable geometric and surface characteristics, including working‐part length, spiral number and density, spiral orientation and symmetry, tip design and machining marks. SEM‐EDS identified near‐equiatomic Ni‐to‐Ti ratios, with no major differences among groups. DSC revealed broadly similar phase‐transformation temperature ranges. BLUE showed greater cyclic fatigue resistance than all other groups ( p ≤ 0.001), whereas DUAL WIRE showed greater cyclic fatigue resistance than PURPLE ( p = 0.035). PURPLE exhibited higher maximum torque than DUAL WIRE ( p = 0.049), while the angle of rotation did not differ among groups ( p = 0.186). BLUE was more flexible than PURPLE ( p = 0.001) but showed lower buckling resistance than GOLD, PURPLE and DUAL WIRE ( p ≤ 0.012). GOLD exhibited greater buckling resistance than DUAL ( p < 0.001), whereas DUAL WIRE showed greater cutting ability than BLUE ( p = 0.036). Conclusion: Despite comparable nominal design, elemental composition and phase‐transformation temperature ranges, different heat‐treatment configurations were associated with distinct mechanical behaviours. BLUE was characterised by greater flexibility and cyclic fatigue resistance but lower buckling resistance, whereas DUAL WIRE showed greater cutting ability than BLUE and greater cyclic fatigue resistance than PURPLE. The Dual Wire heat‐treatment configuration did not confer a generalised mechanical advantage across the properties assessed.

Bacterial cellulose (BC) is a versatile biopolymer prized for its remarkable water absorption, nanoscale fiber architecture, mechanical robustness, and biocompatibility, making it suitable for diverse applications. Despite its potential, the high cost of conventional fermentation media limits BC’s scalability and wider commercial use. This study investigates an economical solution by utilizing fractions from fruit processing wastewater, refined through sequential membrane fractionation, as a supplement to commercial HS medium for BC production. BC films were thoroughly characterized using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and assessments of mechanical properties and water holding capacity (WHC). FTIR confirmed the BC structure, while TEM validated its nanofibrillar 3D network. XRD analysis revealed a slight increasing trend in crystallinity with the addition of wastewater fractions, and DSC revealed a slight increase in thermal stability for F#6. Adding these fractions notably improved the BC films’ tensile strength, Young’s modulus, and WHC. Overall, the results underscore that fruit processing wastewater fractions can serve as a cost-efficient, eco-friendly alternative to traditional fermentation media. This approach supports circular economy principles by lowering reliance on intensive wastewater treatments, promoting waste valorization, and advancing sustainable production methods for high-value biopolymers.

Bacterial cellulose (BC) is a versatile biopolymer prized for its remarkable water absorption, nanoscale fiber architecture, mechanical robustness, and biocompatibility, making it suitable for diverse applications. Despite its potential, the high cost of conventional fermentation media limits BC’s scalability and wider commercial use. This study investigates an economical solution by utilizing fractions from fruit processing wastewater, refined through sequential membrane fractionation, as a supplement to commercial HS medium for BC production. BC films were thoroughly characterized using Fourier transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and assessments of mechanical properties and water holding capacity (WHC). FTIR confirmed the BC structure, while SEM and TEM validated its nanofibrillar 3D network. XRD showed increased crystallinity with the wastewater fractions, and DSC revealed a slight increase in thermal stability for F#6. Adding these fractions notably improved the BC films' tensile strength, Young's modulus, and WHC. Overall, the results underscore that fruit processing wastewater fractions can serve as a cost-efficient, eco-friendly alternative to traditional fermentation media. This approach supports circular economy principles by lowering reliance on intensive wastewater treatments, promoting waste valorization, and advancing sustainable production methods for high-value biopolymers.

[This corrects the article DOI: 10.3389/fpls.2022.999252.].

Exopolysaccharides (EPSs) are a diverse class of biopolymers synthesized by microorganisms under environmental stress conditions, such as pH, temperature, light intensity, and salinity. They offer biodegradable and environmentally friendly alternatives to synthetic polymers. Their structural versatility and functional properties make them unique in various industries, including food, pharmaceuticals, biomedicine, cosmetics, textiles, petroleum, and environmental remediation. In this way, among the well-known EPSs, homopolysaccharides like dextran, bacterial cellulose, curdlan, and levan, as well as heteropolysaccharides like xanthan gum, alginate, gellan, and kefiran, have found widespread applications in numerous fields. However, recent attention has focused on the potential role of extremophile bacteria in producing EPSs with novel and unusual protective and biological features under extreme conditions. Therefore, this review provides an overview of the functional properties and applications of the commonly employed EPSs. It emphasizes their importance in various industries and scientific endeavors while highlighting the raised interest in exploring EPSs with novel compositions, structures, and properties, including underexplored protective functionalities. Nevertheless, despite the potential benefits of EPSs, challenges persist. Hence, this review discusses these challenges, explores opportunities, and outlines future directions, focusing on their impact on developing innovative, sustainable, and functional materials.

The escalating incidence of Candida spp. infections among individuals with compromised immune systems is attributed to various factors, including broad-spectrum antibiotic usage, common health issues, and inadequate undergarments, requiring novel preventive measures. While the pathogenic mechanisms of Candida spp. infections remain incompletely understood, their virulence attributes and opportunistic nature challenge host defenses. In response, this research study introduces an innovative nanobiotechnological approach employing L-cysteine to develop nontoxic anti- Candida spp. textile materials. Cotton, an ideal material for women’s underwear, was functionalized with L-cysteine through an exhaustion procedure following activation with 2,2,6,6-tetramethylpiperidinyl-1-oxy free radical. The results demonstrated increased energy dispersive X-ray peaks corresponding to sulfur atoms in the functionalized cotton fabric, confirming that L-cysteine remained attached to the cotton surface even after washing cycles. Moreover, the cotton containing L-cysteine displayed morphology and mechanical properties similar to the nonfunctionalized cotton, indicating that the incorporation of L-cysteine did not impact the cotton properties. In addition, cotton functionalized with L-cysteine exhibited a significant reduction in yeast growth – 87.04 ± 1.90% for Candida albicans and 65.28 ± 3.03% for Candida parapsilosis – highlighting its potential as a class I medical device, particularly for preventing candidiasis in women’s medical underwear.

Natural fibers have attracted increasing interest as an alternative to produce environmentally friendly and sustainable materials. Particularly, hemp fibers have been widely used in various industrial applications due to their extremely unique properties. However, hemp can generate a large amount of agro-waste, and it results in an attractive source of biopolymers for the development of low-cost materials as an alternative to the raw materials and conventional petroleum-based plastics. In addition, deep eutectic solvents (DESs), a new type of truly green solvents, have been shown to remove gums, lignin, and other non-cellulosic components from hemp fibers. Reusing these components dissolved into the DESs to fabricate new materials directly by electrospinning is a very attractive but still unexplored endeavor. Thus, this innovative research to venture new upcycling pathways is focused on the fabrication of composite nanofibers by electrospinning of a gel-based blend of Poly(vinyl alcohol) (PVA) and hemp agro-waste (HW) dissolved into choline chloride (ChCl):Glycerol (1:2) and ChCl:Urea (1:2) DES mixtures. The results obtained revealed that the produced nanofibers displayed uniform appearance with diameters ranging from 257.7 ± 65.6 nm to 380.8 ± 134.0 nm. In addition, the mechanical properties of the electrospun composite nanofibers produced from the gel-based blends of HW dissolved in DESs and PVA (HW-DESs_PVA) were found to be superior, resulting in an enhanced tensile strength and Young’s modulus. Furthermore, the incorporation of HW into the nanofibers was able to provide bioactive antioxidant and antibacterial properties. Overall, this study demonstrated a promising, more sustainable, and eco-friendly way to produce electrospun composite nanofibers using HW in a circular economy perspective.

Natural fibers have attracted increasing interest as an alternative to produce environmentally friendly and sustainable materials. Particularly, hemp fibers have revealed to be widely used in various industrial applications due to their extremely unique properties. However, hemp can generate a large amount of agro-waste, and results in an attractive source of biopolymers for the development of low-cost materials in alternative to the raw materials and conventional petroleum-based plastics. In addition, deep eutectic solvents (DESs), a new type of truly green solvents, have been tested to remove gums, lignin, and other non-cellulosic components from hemp fibers. Reusing these components dissolved into the DESs to fabricate new materials directly by electrospinning is a very attractive but still unexplored endeavor. Thus, this innovative research to venture new upcycling pathways is focused on the fabrication of composite nanofibers by electrospinning of a gel-based blend of Poly(vinyl alcohol) (PVA) and hemp agro-waste (HW) dissolved into choline chloride (ChCl) : Glycerol (1:2) and ChCl : Urea (1:2) DES mixtures. The results obtained revealed that the produced nanofibers displayed uniform appearance with diameters ranging from 257.72 ± 65.63 nm to 380.78 ± 133.98 nm. In addition, the mechanical properties of the electro-spun composite nanofibers produced from the gel-based blends of HW dissolved in DESs and PVA (HW-DESs_PVA) were found to be superior, resulting in an enhanced tensile strength and Young’s modulus. Furthermore, the incorporation of HW into the nanofibers was able to provide bioactive antioxidant and antibacterial properties. Overall, this study demonstrated a promising, more sustainable, and eco-friendly way to produce electrospun composite nanofibers using HW in a circular economy perspective.