Lyocell/silver knitted fabrics for prospective diabetic foot ulcers treatment: effect of knitting structure on bacteria and cell viability

Materials Today Communications 45 (2025) 112389 Available online 31 March 2025 2352-4928/© 2025 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Lyocell/silver knitted fabrics for prospective diabetic foot ulcers treatment: Effect of knitting structure on bacteria and cell viability Tˆ ania D. Tavares a , Artur Ribeiro b,c , Carlos Bengoechea d , Diana Rocha b , Ana Alcudia e , Bel´ en Begines e , Carla Silva b , Joana C. Antunes f , Helena P. Felgueiras a,* a Centre for Textile Science and Technology (2C2T), University of Minho, Campus de Azur´ em, Guimar˜ aes 4800-058, Portugal b Centre of Biological Engineering (CEB), University of Minho, Campus de Gualtar, Braga 4710-057, Portugal c LABELLS, Associate Laboratory, Braga, Guimar˜ aes, Portugal d Departamento de Ingeniería Química, Escuela Polit´ ecnica Superior, Universidad de Sevilla, Seville 41011, Spain e Departamento de Química Org´ anica y Farmac´ eutica, Facultad de Farmacia, Universidad de Sevilla, Seville 41012, Spain f Fibrenamics Association, Institute of Innovation on Fiber-based Materials and Composites, University of Minho, Guimar˜ aes 4800-058, Portugal ARTICLE INFO Keywords: Knitted fabrics Lyocell Silver-plated polyamide Wound dressings Diabetic foot ulcers ABSTRACT Diabetic foot ulcers (DFUs) are a serious complication of diabetes, often resulting in infections and further health deterioration. Thus, the development of an approach combining different therapies in just one formulation to treat DFUs remains very challenging. Silver-plated polyamide fibers offer antimicrobial properties, while lyocell provides biodegradability, biocompatibility and moisture management abilities. In this sense, the present study explores the potential of lyocell/silver-plated polyamide fabrics as part of advanced wound dressings designed to improve DFU treatment. The most common knitting structures, namely single jersey, “false” rib 1 ×1, single pique, and “false” interlock, were selected for combining the yarns and successfully processed using seamless technology. The knitted fabrics were then subjected to a comprehensive analysis of their physical, chemical, and thermomechanical properties, demonstrating that the samples met the criteria for effective wound dressing development. Their antimicrobial efficacy was evaluated against DFU-associated Gram-negative pathogens, Escherichia coli and Pseudomonas aeruginosa, showing strong antimicrobial activity for up to 24 h, with total inhibition in some cases (jersey, pique and interlock structures for E. coli and interlock structure for P. aeruginosa). Antioxidant testing revealed DPPH reduction of 61.7 ±14.4 %. Biocompatibility was assessed using keratinocytes HaCaT cell lines, showing that knitted fabrics with up to 1.46 % silver content did not harm mammalian cells. In general, interlock structure revealed the most promising features, including mechanical performance, and air and water vapor permeability, for promoting optimal wound healing conditions. 1. Introduction The field of medical textiles has been diversifying with new materials and innovative designs. Advances in fiber technology and manufacturing processes allowed the introduction of cost-effective, environmentally friendly and innovative products in the market [1,2]. Knitting, known for its versatile forming technology, is characterized by increased production efficiency, flexible structures and diverse patterns [3], being able to meet different application requirements [1]. The adoption of seamless knitting technology has seen a remarkable growth, enabling the efficient and flexible production of knitted fabrics with desirable properties such as comfortable compression, air permeability, durability and easy care [4]. The use of polymers obtained from natural sources in areas such as biomedicine has had a huge impact in recent decades [5]. Lyocell is a relatively new fiber made from natural cellulose via a sustainable and environmentally friendly process. It is the only regenerated cellulosic fiber in which 99.8 % of its solvent, N-methylmorpholine N-oxide, is recycled [6]. This fiber has exceptional physical properties, such as high tensile strength and tenacity in wet state, good thermal resistance and shape stability, as well as high crystallinity and absorbency. Comfort and softness are also typical traits of this fiber. In addition to their non-toxic, * Corresponding author. E-mail addresses: [email protected] (T.D. Tavares), [email protected] (A. Ribeiro), [email protected] (C. Bengoechea), id9610@alunos. uminho.pt (D. Rocha), [email protected] (A. Alcudia), [email protected] (B. Begines), [email protected] (C. Silva), [email protected] (J.C. Antunes), [email protected] (H.P. Felgueiras). Contents lists available at ScienceDirect Materials Today Communications journal homepage: www.elsevier.com/locate/mtcomm https://doi.org/10.1016/j.mtcomm.2025.112389 Received 11 December 2024; Received in revised form 4 March 2025; Accepted 30 March 2025 Materials Today Communications 45 (2025) 112389 2 non-polluting, and biodegradable nature, lyocell presents great adaptability and processability with other fibers [7]. Polyamide is a synthetic polymer with excellent mechanical features, namely high tenacity and tensile strength. Also, its surface structure possesses small cavities that can be used as chelation points for subsequent metal plating, making it a great substrate for metallization [8]. Silver is renowned for its numerous benefits, including its high antimicrobial, anti-odor, electrical conductivity and thermo-reflective properties [9]. Furthermore, it is one of the most suitable metals to incorporate into textile yarns, as they retain all their original properties after undergoing metallization. Currently, silver-plated polyamide fibers are being used in a wide range of functional textiles, particularly in the antimicrobial, antistatic, thermal conductive and electromagnetic fields [10]. In the medical sector, these yarns knitted into fabrics serve the purpose of treating burn victims and patients with open wounds [11]. Also, these fibers can be blended and processed with various natural or synthetic materials, increasing their functional range [8]. Worldwide, 10.5 % of the population suffers from diabetes, a disease responsible for imposing significant disruptions in the health care systems’ resources, with annual costs of approximately 918.8 billion euros [12]. One of the most common problems arising from this illness is the development of DFUs, which affect 15–25 % of the diabetic population during their lifetime. DFUs significantly increase the risk of lower extremity amputation and/or patient mortality [13]. Current treatment strategies for DFUs vary depending on the lesion severity and may include debridement of non-viable tissue, infection control, revascularization, wound protection, and ulcer off-loading [14,15]. However, most of these interventions focus on addressing individualized barriers to wound healing without considering other potential events or factors that may also interfere with the healing process. Consequently, developing an integrated therapeutic approach in a single formulation remains a considerable challenge in the field. Here, the objective is to elucidate about the most suitable structural configuration that can significantly enhance the efficiency of knitted products, produced via seamless technology, in the context of chronic wound care. Therefore, to overcome the previously mentioned limitations of DFU treatments, the fabrication of a novel wound dressing from lyocell/silver-plated polyamide based yarns is proposed to generate a clean and moist environment around the injured site, absorb exudates and toxic components from the wound bed, allow gas exchange between the wound and environment, and protect the wound from the penetration of microorganisms and foreign particles. Physical, chemical, and thermomechanical analyses were conducted to confirm these characteristics. Additionally, the knitted fabrics were subjected to antibacterial tests against Gram-negative bacteria, namely Escherichia coli and Pseudomonas aeruginosa, which are amongst the most prevalent bacteria colonizing DFUs and pose significant challenges to wound healing [16]. Antioxidant and cytocompatibility evaluations, to establish the safety of the dressing systems against mammalian cells, were also conducted. To the authors’ knowledge, this is the first report on the production of a knitted fabric combining lyocell with polyamide-silver plated, while also investigating the influence of structural variations on its potential for wound care applications. 2. MAterial AND METHODS 2.1. Materials Lyocell spun yarns (149 dtex) were kindly provided by Risatel, Lda. (Portugal) and silver-plated polyamide 6 multifilament yarns (40 dtex) were purchased from Shieldex® (Germany). Sodium chloride (NaCl, Merck, Germany), potassium chloride (KCl, Merck), sodium phosphate dibasic (Na 2 HPO 4 , Sigma-Aldrich, Germany) and monopotassium phosphate (KH 2 PO 4 , Sigma-Aldrich) were used in the preparation of phosphate buffer saline solution (PBS at 0.01 M: 8.00 g/L of NaCl, 0.20 g/L of KCl, 1.44 g/L of Na 2 HPO 4 and 0.24 g/L of KH 2 PO 4 , adjusted to physiological pH 7.4). Artificial wound exudates were prepared with NaCl (124 ×10 −3 M), magnesium chloride (MgCl 2 , 831 ×10 −6 M, Chem-Lab, Belgium), calcium chloride (CaCl 2 , 2.48 ×10 −3 M, ChemLab), sodium bicarbonate (NaHCO 3 , 36.8 ×10 −3 M, Sigma-Aldrich), glucose (C 6 H 12 O 6 , 5 ×10 −3 M, Sigma-Aldrich), albumin (150 ×10 −6 M, VWR Chemicals, Portugal) and lactic acid 90 % (C 3 H 6 O 3 10 ×10 −6 M, Merck), at pH 6.72 and pH 9 [17]. The bacteria culture media trypticase soy broth (TSB), trypticase soy agar (TSA), nutrient broth (NB) and nutrient agar (NA) were obtained from VWR Chemicals, and Müeller-Hinton broth (MHB) was supplied by Condalab (Spain). Bacterial strains were provided by American Type Culture Collection (ATCC, USA): E. coli ATCC 25922 (grown in TSB/TSA) and P. aeruginosa ATCC 27853 (grown in NB/NA). 1,1-diphenyl-2-picrylhydrazyl (DPPH) and trypan blue were supplied by Merck, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) was acquired from Fisher (India). The antibiotic-antimycotic solution (penicillin/streptomycin), trypsin-EDTA, dimethyl sulfoxide (DMSO) cell culture grade, and resazurin (Xpert blue cell viability assay) were purchased from GRISP (Portugal). Fetal bovine serum (FBS) and cell culture media Dulbecco’s modified Eagle’s medium (DMEM) were acquired from PAN-Biotech (Germany), DKFZ HaCaT adherent cell line (immortalized human keratinocytes) was obtained from Cell Lines Service (CLS, Germany) and provided by DKFZ (Germany). All reagents were used without further purification. 2.2. Production of lyocell/silver knitted fabrics Lyocell spun yarns and silver-plated polyamide multifilament yarns were used to produce full Jacquard seamless weft fabrics via knitting machine Santoni model SM08-EVO4J (Sid´ onios Seamless Tech S.A), with a E28 gauge, diameter of 13” and 1152 latch needles. The fabrics were produced with varying percentages of silver content (w/w), specifically 0.00 % (sample 0), 0.31 % (sample 1), 0.65 % (sample 2), 1.03 % (sample 3), and 1.46 % (sample 4), and with four distinct structures, namely single jersey (sample J), “false” rib 1 ×1 (sample R), single pique (sample P), and “false” interlock (sample I). The silver content percentages were carefully selected to optimize processability and ensure structural integrity of the knitted fabrics; higher silvercontaining yarn contents were avoided due to the resulting thin samples with excessively large pores, which were deemed unsuitable for the intended application. Fabrics were washed three times in a 200 mL distilled water (dH 2 O) bath at 50 rpm, 90 ±5 ◦C for 30 min using an Ibelus C-720 machine (Portugal) equipped with infrared heating. The primary objective was to remove the surface treatment (desizing), specifically paraffin wax applied to the yarns. 2.3. Characterization Lyocell/silver and lyocell (control) knitted fabrics were subjected to a comprehensive analysis of their physical, chemical, and thermomechanical properties. In specific examinations, the inherent structure of the knitted fabrics was considered inconsequential (did not influence the outcomes). In such scenarios, consideration was given to samples with a single jersey structure, as this represents the simplest structural arrangement from which the others derive; in those situations, jersey structure may be perceived as a control structure. 2.3.1. Reflectance test The reflectance of the knitted fabrics was evaluated preand postwashing using a Shimadzu UV–VIS spectrophotometer UV-2600 (Japan) in the range between 400 and 700 nm. Data were expressed as percentage of reflectance. 2.3.2. Morphology The morphology of the samples was observed by brightfield T.D. Tavares et al. Materials Today Communications 45 (2025) 112389 3 microscopy using a Leica DM IL LED inverted microscope (Leica Microsystems, Germany). Additionally, images were taken using a Leica EZ4 D magnifier (Leica Microsystems) at a magnification of 30 ×, and these images were collected with a digital camera (OnePlus Nord N10 5 G). 2.3.3. Physical properties The physical properties of the knitted fabrics were characterized by mass per unit area (digital scale), contexture (using a yarn-counting magnifying glass), loop length (based on 10 measurements of the length of the yarn, collected from 10 wales; Artilab Sodemat meter), thickness (10 measurements in random areas of the samples, using a Mitotoyo analog micrometer with a resolution of 0.01 mm, 10 mm of pressure area and 18 Pa of applied pressure), and porosity calculated using the following equation (Eq. 1): Ɛ(%) = (1– ρ a ρ b×t) × 100 (1) where ρ a (g/cm 3 ) is the fabric density (weight per unit area), ρ b (g/cm 3 ) is the fiber density, and t (cm) is fabric thickness [18]. 2.3.4. Fourier-transform infrared spectroscopy in attenuated total reflectance mode (ATR-FTIR) The chemical composition of lyocell/silver and lyocell knitted fabrics (single jersey structure) preand post-washing were analyzed by ATRFTIR using an IRAffinity-1S, Shimadzu spectrophotometer (Japan), coupled with a HATR 10 accessory with a diamond crystal. Spectra were obtained over a range of 4000–400 cm −1 , with 200 scans being performed at a spectral resolution of 4 cm −1 . 2.3.5. Thermal gravimetric analysis (TGA) The knitted fabrics (single jersey structure) thermal degradation behavior preand post-washing was assessed by weight loss monitoring on a STA 7200 Hitachi® (Japan), using aluminum crucibles. The assessment involved increasing the temperature within the range of 25–600 ◦C, at a heating rate of 10 ◦C/min under a dynamic nitrogen atmosphere at a flow rate of 200 mL/min to create an inert environment. Each sample had an initial mass of 6.7 ±0.2 mg. Results were plotted as the percentage of weight loss vs. temperature. 2.3.6. Differential scanning calorimetry (DSC) Thermal properties were also evaluated by DSC analyses using a power compensated DSC equipment PerkinElmer DSC 6000 (USA). Samples weighing 7.2 ±0.6 mg were placed in an aluminum pan and exposed to a heating rate of 10 ◦C/min, from 0 to 445 ◦C, under a dynamic nitrogen atmosphere at 20 mL/min. DSC curves were plotted with heat flow vs. temperature. 2.3.7. Quasi-static mechanical testing The mechanical properties of the knitted fabrics were measured using a uniaxial tensile test on the MTS™ Insight Electromechanical Testing Systems (USA) with a 10 kN load cell, following the ASTM D5035–11(2019) standard. The samples were prepared with dimensions of 2 ×7 cm, gauge length of 50 mm and analyzed at room temperature (RT). The tests were performed with a preload of 0.1 N and a speed of 10 mm/min until reaching the maximum elongation at break. Experiments were conducted on at least five replicates in each direction of the knitted fabric (course and wale). Young’s modulus (MPa), total elongation (%) and ultimate tensile strength (MPa) were obtained from stress-strain curves. 2.3.8. Degree of swelling (DS) The knitted fabrics DS was evaluated in dH 2 O, PBS and artificial wound exudates (pH 6.72 and pH 9) solutions at 37 ◦C. To conduct the assessment, samples with a surface area of 2 cm 2 were weighed and submerged in 2 mL of the respective medium for 1, 2, 4, 6, 24, 48, 72 and 168 h under static conditions. At each specified interval, the samples were collected, and their wet weight was measured. Gauze was used as reference. The DS was calculated using the following equation (Eq. 2): DS (%) = mw−md md×100 (2) where m w (mg) is the weight of the sample after immersion and m d (mg) is the weight of the dried sample before immersion [19]. 2.3.9. Knitted fabric degradation profile The degradation profile of knitted fabrics over time was assessed in dH 2 O, PBS and artificial wound exudates (pH 6.72 and pH 9) solutions. Hydrated knitted fabrics, with a surface area of 2 cm 2 , were weighed and incubated in 2 mL of each solution at 37 ◦C, up to 28 days. Experiments were conducted under static conditions, with solutions being exchanged every week. After 1, 3, 7, 14, 21, and 28 days of incubation, the samples were weighed. Gauze was used as reference. Degradation, determined by measuring mass loss, was calculated using the following equation (Eq. 3): mass loss (%) = mwi −mwf mwi ×100 (3) where m wi (mg) represents the weight of the hydrated knitted fabric at day 0, and m wf (mg) corresponds to the weight of the sample after each incubation period [20]. 2.3.10. Moisture and air permeabilities To assess the knitted fabrics’ capacity for moisture retention and air exchange, water/vapor and air permeabilities studies were conducted according to standards BS 7209:1990 and ASTM D 737–96, respectively. Gauze served as reference material in both tests. For the water vapor permeability (WVP) examination, samples (132.7 mm² area) were placed over cylindrical cups containing 46 mL of dH 2 O for 24 h, utilizing an SDL Atlas M261 Shirley water vapor permeability tester (USA). The evaporation of water through the fabric under test was determined by weighing the cup before and after the testing period. An open cup was used as reference. Assessments were performed at 37 ◦C and 50 % of relative humidity within an Aralab FitoClima 150 EDTU chamber (Portugal). Measurements were conducted in triplicate. The water vapor transmission rate (WVTR) was determined using Eq. 4: WVTR =24ΔW AΔt(4) where ΔW is the difference in the water weight (g) before and after the 24 h test, A is the inner area of the cup (m 2 ), and Δt is the exposure time (h). A FX 3300 air permeability tester III (Textest Instruments, Switzerland) was employed to apply an air pressure of 100 Pa on each sample at ten equidistant points of 20 cm 2 . 2.4. Antimicrobial evaluation To assess the antimicrobial efficacy of the knitted fabrics, time-kill kinetics tests were conducted using an adaptation of the ASTM E2149–01 standard. Here, only Gram-negative bacteria were examined due to the greater challenges associated with their effective elimination by antimicrobial wound dressings, compared to Gram-positive. Bacteria inoculums were prepared in TSB (E. coli) and NB (P. aeruginosa) and incubated overnight at 37 ◦C, 120 rpm. Then, bacteria suspensions were adjusted to a concentration of 1 ×10 5 colony forming units (CFUs)/mL in MHB. Samples with a surface area of 1 cm 2 were immersed in 1 mL of bacteria suspension and incubated at 37 ◦C and 120 rpm. At specific time intervals (1, 2, 4, 6 and 24 h), aliquots of the bacterial suspensions were collected and serially diluted in PBS (10 −1 to 10 −5 ), plated on TSA/ T.D. Tavares et al. Materials Today Communications 45 (2025) 112389 4 NA, and further incubated at 37 ◦C for 24 h. Colonies of surviving bacteria were counted, and the results were expressed as log reduction by comparing the control suspensions (without sample) with those exposed to the knitted fabrics. 2.5. Antioxidant activity The free radical scavenging activity of the knitted fabrics was determined using the DPPH assay. Samples with a surface area of 2 cm 2 were incubated in 2 mL of DPPH stock solution (100 µM, 100 % ethanol) at 37 ◦C and 120 rpm. At specific time intervals (1, 2, 4, 6, 24 and 48 h), aliquots were collected, and the absorbance was measured at 515 nm in a microplate reader EZ READ 2000 (Biochrom, UK). Trolox was used as a positive control, and DMSO was used as a negative control. The results were expressed in terms of the percentage of reduced DPPH at steady state (DPPHr) and were calculated following the Eq. 5: DPPHr (%) = Ac−As Ac×100 (5) where A c is the absorbance of control (without sample), and A s is the absorbance of samples registered at steady state. 2.6. Cytocompatibility testing The metabolic activity of human keratinocytes cell line (HaCaT) [21] was assessed through an indirect contact assay conducted on the knitted fabrics identified with the most effective structural characteristics for the foreseen purpose (based on the previous characterization testing). Samples with a surface area of 4 cm 2 were sterilized under ultraviolet light (10 min on each side) and submerged in 4 mL of DMEM medium for 24 h (conditioned media). Cells were thawed and sub-cultured in DMEM medium supplemented with 10 % (v/v) inactivated FBS and 1 % (v/v) penicillin-streptomycin. The cells were kept at 37 ◦C in a humidified atmosphere with 5 % CO 2 until reaching 80–90 % confluence. Thereafter, the cells were chemically detached from the culture flasks using 0.05 % (w/v) trypsin-EDTA solution. Cell counting, facilitated by a Neubauer Chamber and trypan blue (ratio 1:1 v/v) staining for dead cells exclusion, was conducted using a Leica DM IL LED Inverted Laboratory Microscope (Germany). Cells were then seeded in 96-well tissue culture polystyrene plates (TPP®, Switzerland) at a density of 1 ×10 4 cells per well and incubated at 37 ◦C and 5 % CO 2 for 24 h. The experiments were carried out using HaCaT in passages 5–11. After 24 h, the conditioned media were diluted to concentrations of 50 %, 25 % and 10 % (v/v), and subsequently added to the cells for further incubation periods of 24 and 48 h. Following these intervals, 10 % (v/v) resazurin was added to the wells and incubated for 4 h at 37 ◦C and 5 % CO 2 . Then, fluorescence levels were measured (λ ex =560 nm and λ em =590 nm) using a microplate reader (Synergy H1, BioTek Instruments, USA). To establish positive and negative controls, DMEM conditioned media (without samples) and 30 % (v/v) of DMSO were used, respectively. The percentage of cell metabolic activity, used as indicative of cell viability, was calculated using Eq. 6: Metabolic activity (%) = Flus Flupc ×100 (6) where Flu s represents the fluorescence of the samples, and Flu pc is the fluorescence of the positive control. 2.7. Statistical analysis All experiments were conducted in triplicate unless otherwise referred to in the experimental sections. Numerical data were reported as mean ±standard deviation (SD). Data were treated using GraphPad Prism 8.0.1 Software (GraphPad Software Inc., USA). Normality analysis was performed, and results were analyzed using Tukey’s test. Statistically significant differences were considered at p <0.05. 3. REsults AND Discussion 3.1. Morphology and physical properties The production of the knitted fabrics was highly successful, with no defects detected in any of the structures. After manufacturing, the fabrics underwent a series of washing procedures to eliminate potential paraffin residues from the yarns, and a decrease in water turbidity was observed after each wash. Reflectance tests were conducted to assess the effectiveness of these washes (Figure S1 in the Supporting Information file). Post-washing, the increase in reflectance values confirmed the successful elimination of paraffin, enhancing the surface reflectivity of the samples. Additionally, weighing the samples before and after washing revealed a mass loss of 3.65 ±0.21 %. Brightfield microscopy examinations conducted after washing confirmed the integrity of the yarns, indicating that the fabrics remained intact and undamaged (Figure S2 in the Supporting Information file). Fig. 1 shows the successful production of sample 4 with the desired knitted structures. This sample, which contained the highest percentage of silver-plated polyamide yarns (1.46 %), was selected as the representative sample to illustrate the structural organization of the knitted fabrics. To enhance visualization, loop diagram illustrations and brightfield microscopy images of each structure were included. The presence of the silver-plated yarns was evident by the increased shine and metallization observed. The images display both sides of the knitted fabrics, where the distinct appearance between them is noticeable. The use of seamless technology presents a significant advantage for the intended application, as it enhances the comfort and adaptability of the fabrics to the body, reducing friction and the risk of skin irritation, making it ideal for products where direct skin contact is constant. Additionally, it offers properties such as breathability, durability, and easy care [4]. The rib and interlock structures are classified as “false” because they are produced on a seamless knitting machine, resulting in differing appearances between sides. To the contrary, “true” rib and interlock structures appear identical on both sides. Single jersey was the simplest and most fundamental knitted structure, serving as a basis for more complex patterns. Its technical face features vertical columns of knit stitches forming small V-shaped loops, while the technical back displays horizontal rows of purl stitches, which look like small horizontal loops or bumps (Fig. 1a). The “false” rib 1 ×1 structure exhibits a technical face with alternating columns of knit and purl stiches, and a technical back with more prominent rows of purl stitches, creating a smoother and less textured appearance (Fig. 1b). In the single pique structure, the technical face features small, raised bumps resembling a waffle-like pattern, created by tuck stitches that provide a three-dimensional look. The technical back is more uniform and smoother, with visible horizontal rows of purl stitches (Fig. 1c). Lastly, the “false” interlock structure has a technical face characterized by a smooth, flat surface created by the interlocking of knit stitches. The technical back is more textured, featuring a combination of knit and purl stitches that form a series of raised bumps or ridges (Fig. 1d) [22]. The physical properties of knitted fabrics are detailed in Table 1 (statistical analysis shown in Tables S1 and S2 in the Supporting Information file). Data from Table 1a indicates that an increase in the amount of silver-plated polyamide yarns correlates with a statistically significant decrease in mass per unit area. This observation aligns with expectations, as the dtex of these yarns is significantly smaller than that of the lyocell yarns, resulting in a reduced overall weight. Among the knitted fabric structures, interlock registered the largest weight. Regarding contexture (Table 1a), structures were generally similar, with the exception of the rib structure, which reported smaller values, particularly in the number of wales per cm (p <0.0001). Additionally, this structure displayed greater loop length (Table 1a) and porosity (Table 1b), all indicatives of a more open knit [23]. Table 1b shows that T.D. Tavares et al. Materials Today Communications 45 (2025) 112389 5 the thickness of the samples was relatively constant, regardless of the varying amounts of silver-plated polyamide yarns (not statistically significant, except R4 and P4). The interlock structure was found the thickest from the group, while the jersey was the thinnest (p <0.0001). It was anticipated that the small dtex of the silver-plated polyamide yarns would result in a significant increase in porosity as their content augmented in the fabrics (Table 1b). Even though there was a slight increase between 2 % and 5 %, it is likely that the superior elasticity of the silver-plated polyamide yarns (25.04 ±5.11 %) compared to the lyocell yarns (8.04 ±0.55 %) to have facilitated the adaptation of the first to the fabric construct, thus occupying the same spaces as lyocell yarns and slightly constricting their freedom. As can be seen by Fig. 1, silver-plated yarns appear to overlap with lyocell yarns. Fig. 1. Loop diagram, digital and brightfield microscopy images of the (a) jersey, (b) rib, (c) pique and (d) interlock structures, obtained from knitted fabrics containing the largest number of silver-plated yarns (sample 4 – 1.46 %). Scale bars represent 1 mm and 500 µm, for digital and brightfield microscopy images, respectively. Table 1 Physical characterization of the knitted fabrics: (a) mass per unit area, contexture and loop length; (b) thickness and porosity (Ɛ). Data are reported as mean ±SD (n =10). Sample 0 corresponds to 100 % lyocell, while samples 1, 2, 3 and 4 correspond knitted fabrics with silver in their composition at 0.31 %, 0,65 %, 1.03 %, and 1.46 %, respectively. a) Mass per unit area (g/m 2 ) Contexture (courses/wales per cm) Loop length (cm) Sample Jersey Rib Pique Interlock Jersey Rib Pique Interlock Jersey Rib Pique Interlock 0208.6 ±8.3 216.1 ±5.0 219.4 ±3.9 241.1 ±6.6 13/16 13/11 13/15 13/15 33.8 ±0.4 34.0 ±0.2 21.8 ±0.4 22.0 ±0.3 1198.8 ±6.7 221.5 ±4.3 217.0 ±5.6 247.5 ±6.0 13/16 12/11 13/16 13/15  2191.0 ±7.2 210.0 ±3.9 200.9 ±5.7 222.5 ±5.6 13/16 13/11 13/16 13/16  3170.9 ±12.1 203.0 ±3.9 196.8 ±4.1 222.8 ±5.3 13/16 13/11 13/17 14/15  4172.4 ±11.8 182.3 ±3.1 204.0 ±8.1 216.3 ±7.3 14/16 14/11 13/16 14/14  b) Thickness (mm) ƐƐ (%) Sample Jersey Rib Pique Interlock Jersey Rib Pique Interlock 00.58 ±0.03 0.66 ±0.04 0.62 ±0.03 0.67 ±0.02 68.5 ±1.0 72.3 ±1.7 69.1 ±1.0 68.9 ±0.8 10.54 ±0.03 0.63 ±0.06 0.61 ±0.03 0.66 ±0.03 67.8 ±1.4 69.6 ±1.6 68.6 ±0.6 67.0 ±1.3 20.56 ±0.03 0.66 ±0.06 0.61 ±0.04 0.64 ±0.05 70.5 ±1.8 72.3 ±0.9 71.5 ±2.0 70.1 ±0.9 30.56 ±0.02 0.63 ±0.04 0.58 ±0.03 0.66 ±0.04 73.6 ±2.2 72.4 ±1.0 70.0 ±1.5 71.0 ±0.1 40.56 ±0.02 0.62 ±0.04 0.55 ±0.03 0.63 ±0.03 73.6 ±1.5 74.8 ±2.4 72.8 ±0.9 71.6 ±0.5 T.D. Tavares et al. Materials Today Communications 45 (2025) 112389 6 3.2. Chemical analysis ATR-FTIR analyses were performed on knitted fabrics exhibiting a jersey structure, both preand post-washing, with the aim of evaluating the efficacy of paraffin wax layer removal from the yarns (Fig. 2). In Fig. 2a, the presence of paraffin in the fabrics was observed through the detection of two distinct bands at 2916 and 2849 cm −1 , corresponding to the antisymmetric and symmetric stretching vibration of aliphatic hydrocarbons, respectively, which are main components of paraffin wax [24]. Post-washing (Fig. 2b), these paraffin-related bands disappeared, while a distinctive peak at 2896 cm −1 attributed to the CH alkane group in lyocell [25] became more pronounced. Furthermore, both spectra displayed a peak at 3320 cm −1 corresponding to the –OH stretching band of cellulose, alongside notable peaks at 1018 and 895 cm −1 related to the P =O and P-O-C group, respectively [26]. In contrast, no peaks corresponding to polyamide or silver were detected. The absence of polyamide peaks can be attributed to the low mass ratio of silver-plated polyamide yarns to lyocell yarns, which hinders their detection. Additionally, the silver coating presents challenges due to its high electrical conductivity, which limits its spectral response in the infrared range. FTIR is a technique that provides infrared spectral analysis of samples capable of absorbing infrared light. However, the free electrons within the silver’s structure do not engage in the typical vibrational transitions observed in molecules during FTIR Fig. 2. ATR-FTIR spectra of lyocell and lyocell/silver knitted fabrics (a) preand (b) post-washing. Sample J corresponds to the jersey structure with 100 % of lyocell (sample 0), and 0.31 % (sample 1), 0,65 % (sample 2), 1.03 % (sample 3) and 1.46 % (sample 4) represent samples containing silver yarns at various ratios. T.D. Tavares et al. Materials Today Communications 45 (2025) 112389 7 spectroscopy. Consequently, the absorption of infrared radiation, fundamental to FTIR spectroscopy, is not readily observed in metals such as silver [27]. 3.3. Thermal stability The thermal stability of the knitted fabrics (using the jersey structure as example) was evaluated using TGA (Figs. 3a, 3b and Table S3 in the Supporting Information file) and DSC (Figs. 3c, 3d and Table S3 in the Supporting Information file). The thermal degradation steps of the samples, both preand post-washing processes, were comprehensively analyzed using TGA. All samples showed similar thermal behavior. Initially, a distinctive degradation phase was observed up to around 112 ◦C, resulting in a mass loss of ≈8 % associated with the evaporation of water molecules bound to the lyocell structure. The process involves a sequence of depolymerization, hydrolysis, and dehydration reactions [26]. Subsequently, the fabrics maintained a thermal stability up to around 255 ◦C for the pre-washed samples and 280 ◦C for the post-washed samples. This discrepancy in thermal stability can be explained by the presence of paraffin in the unwashed samples, which volatilizes at low temperatures, primarily contributing to the earlier onset of degradation [28]. The start of the second degradation stage, extending up to around 368 ◦C, was marked by a substantial mass loss of ≈67 %. This significant degradation stems predominantly from the decomposition of lyocell, which constitutes the primary component of the studied samples. During this stage, the breakdown of the crystalline structure of lyocell occurs, leading to the generation of L-glucose [26]. Following the extensive degradation of lyocell, a third weigh loss stage was observed, characterized by a slight mass loss of ≈9 %, attributed to the gradual decomposition of char residues originating from the lyocell yarns (residue from the prior degradation steps) [29]. Additionally, this stage may involve the thermal degradation of polyamide components present within the silver-containing knitted fabrics [30]. Thermal analysis using TGA highlights the thermal resistance of the fabrics, and its main polymeric components, which exceed typical body temperatures. Thus, this thermal stability supports potential applications of these fabrics in wound dressings, guaranteeing their integrity and performance under physiological conditions. Correlation between TGA and DSC thermograms facilitates the comprehension of the thermal phenomena occurring during the heat treatment of the samples. The initial broad endothermic event, featuring peaks within the temperature range of 100 – 116 ◦C with a high thermal energy of ≈1383.27 mJ, is attributed to the desorption of absorbed water molecules from cellulose [31]. Subsequent to moisture evaporation, a well-defined endothermic event, characterized by a peak at 258 – 261 ◦C, is exhibited only in samples containing silver-plated polyamide yarns; the peak area increases with the augment in number of silver-containing yarns within the samples. Upon further heating at 349 – 353 ◦C, another endothermic event becomes apparent due to structural transformations of cellulose, encompassing decomposition and depolymerization reactions, followed by an exothermic event associated with the subsequent decomposition of the resultant complex products [32]. The influence of paraffin was insignificant and was not detected by DSC, as its thermal decomposition occurs at around 60 – 70 ◦C [33], being likely masked by the significant water loss registered from lyocell yarns. This is corroborated by a small fabric weight loss observed after washing (3.65 ±0.21 %), thus indicating its minimal contribution to the samples. Similar results were observed in the interlock structure containing the largest number of silver-plated yarns (sample 4–1.46 %), thereby confirming that the findings are independent of the knitted fabric structure (Figure S3 in the Supporting Information file). 3.4. Mechanical performance The mechanical resistance of the knitted fabrics was assessed in the course and wale directions, using parameters such as Young’s modulus, elongation at break, and ultimate tensile strength (Fig. 4; statistical analysis shown in Table S4 in the Supporting Information file). Young’s Fig. 3. TGA and DSC spectra of lyocell and lyocell/silver knitted fabrics (a and c) preand (b and d) post-washing, respectively. Sample J corresponds to the jersey structure with 100 % of lyocell (sample 0), and 0.31 % (sample 1), 0,65 % (sample 2), 1.03 % (sample 3) and 1.46 % (sample 4) represent samples containing silver yarns at various ratios. T.D. Tavares et al. Materials Today Communications 45 (2025) 112389 8 modulus quantifies the relationship between stress (applied force) and strain (resultant deformation) in the linear region in the knitted fabrics. Elongation at break and tensile strength are particularly important for wound dressings: a high elongation at break indicates flexibility, aiding in skin application (adaptability to injured site), while high tensile strength ensures the fabric’s integrity during wound placement or removal, minimizing patient discomfort and preventing damage to sensitive tissue [34,35]. Anisotropic behavior was observed in the sample’s structures, characterized by distinct responses along the course and wale directions. Specifically, the wale direction exhibited higher Young’s modulus and elongation at break for the jersey, rib, and pique structures, at the expense of a reduced strength. This suggests that these structures, while more flexible in this direction, may be more prone to rupture under excessive mechanical stress. Conversely, the interlock structure demonstrated a more uniform mechanical response between directions, with similar Young’s modulus and elongation at break and a slightly higher tensile strength in the wale direction. These findings indicate that interlock structures may offer enhanced isotropy, which can be beneficial for applications requiring balanced mechanical properties. For a clearer comparison between directions, representative stress-strain curves of tested structures, namely those composed of 100 % lyocell and the highest number of silver-plated yarns (sample 4), are provided in Figure S4 in the Supporting Information file. Analysis of these curves reveals that the wale direction generally exhibited a more abrupt rupture with lower overall deformation, indicating reduced ductility. This behavior suggests that, despite offering greater stiffness and elongation capacity, the wale direction may be more susceptible to sudden failure under tensile loading. These insights are crucial for optimizing the mechanical properties of knitted fabrics in biomedical applications, where a balance between flexibility and strength is essential for functional performance. Overall, the samples displayed low Young’s modulus (Fig. 4a), indicating a high degree of flexibility suitable for the intended purposes. The samples with the highest silver content (sample 4) exhibited the lowest stiffness in wale direction. All samples showed considerable deformability (Fig. 4b), with maximum elongation at break ranging from ≈75–184 %, notably higher in the interlock structure in the wale direction (p <0.0001) and in the jersey structure in the course direction Fig. 4. (a) Young’s modulus, (b) total elongation, and (c) ultimate tensile strength of the knitted fabrics in course and wale directions. Data are reported as mean ±SD (n =5). Sample 0 corresponds to 100 % lyocell, while samples 1, 2, 3 and 4 correspond knitted fabrics with silver in their composition at 0.31 %, 0,65 %, 1.03 %, and 1.46 %, respectively. T.D. Tavares et al. Materials Today Communications 45 (2025) 112389 9 (p <0.0001). The rib structure demonstrated minimal deformation compared to other structures (Fig. 4c), and, consequently, the lowest strength (p <0.0001). In general, the analyzed knitted fabrics possess mechanical properties that meet the criteria required for effective wound dressing development. However, the interlock structure can be deemed the most suitable for dressings intended for wounds in highly mobile body areas, such as DFUs, due to its lower anisotropic behavior, which may contribute to an improved conformability and mechanical stability in dynamic conditions. 3.5. Degree of swelling and degradation profile Ensuring optimal wound healing requires the use of dressings with adequate moisture absorption and retention capabilities. This guarantees that the dressing not only absorbs excess exudates proficiently, preventing desiccation, but also maintains a moist environment in the wound, conducive to tissue repair and regeneration, essential for the progression of the healing process [36]. The swelling capacity of knitted fabrics under various conditions (dH 2 O, PBS, and artificial wound exudates at pH 6.72 and pH 9) was monitored over a period of 7 days. Fig. 5 presents the measurements on the 7th day of incubation (statistical analysis shown in Tables S5 and S6 in the Supporting Information file), while the measurements monitored up until day 7 of incubation are illustrated in Figure S5 in the Supporting Information file. PBS was chosen due to its physiological similarity to human biological fluids in terms of osmotic and ionic conditions [37]. Artificial wound exudate solutions were prepared according to the characteristic environmental pH of chronic wounds, which typically falls within the range of 7.15–8.9 [38]. Additionally, dH 2 O was included for comparative purposes, to assess the influence of the presence of salts in the media. After the first hour, the knitted samples exhibited a significant DS, with an average weight increase ranging from ≈161–236 %, while gauze, the control group, reached a DS above 328 %. This difference underscores the distinct absorption behaviors of knitted fabric compared to gauze, which possesses a more open and loosely packed structure, allowing for rapid liquid uptake. Similar trends were observed after 7 days of incubation, with DS values stabilizing in the range of ≈137–227 %, demonstrating the sustained absorption capacity of the samples over time. A slight reduction in absorption capacity (≈36 %) was observed in the knitted fabrics when immersed in dH 2 O after 6 h (jersey and rib structures) and 24 h (pique and interlock structures; Figure S5 in the Supporting Information file). This decrease can be attributed to the saturation of hydrogen bonding interactions between the water molecules and the hydroxyl groups of the lyocell celluloses [29]. Notably, a similar trend was observed in the presence of PBS, where a ≈27 % decrease in absorption capacity was recorded after 24 h (jersey and rib structures) and 48 h (pique and interlock structures). This reduction is possibly due to the competitive interaction of PBS salts with hydroxyl groups, altering the fabric’s ability to retain free water molecules. The variation in saturation times between different structures is primarily related to their morphological characteristics; jersey, with its lower thickness values (Table 1b), saturates more quickly, while rib, with its denser architecture and compact arrangement, also reaches saturation sooner than pique and interlock structures (Fig. 1). When exposed to artificial wound exudates, all knitted structures exhibited comparable swelling behavior, maintaining an equilibrium DS (averaging 197 %) over the 7-day period at pH 6.72. On the other hand, exposure to alkaline exudates (pH 9) led to a moderate increase in absorption capacity (≈13 %) after 6 h (Figure S5 in the Supporting Information file). The hydrophilicity of knitted fabrics is positively correlated with their absorption capacity, as higher hydrophilicity generally leads to increased fluid uptake. Despite multiple attempts, wettability data could not be obtained for any sample due to the extreme hydrophilicity of lyocell, facilitated by its high content of carboxylic groups [39]. An ideal wound dressing typically exhibits an absorbency range between 100 % and 900 % [40], positioning the engineered samples within the appropriate threshold for this application. Among the tested structures, the interlock exhibited the highest absorption ratings, on average, across all tested solutions. 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