Search Results (34)

The textile industry’s reliance on synthetic dyes contributes significantly to pollution, highlighting the need for sustainable alternatives like biopigments. This study investigates the production and application of the biopigment prodigiosin, which was produced by Pseudomonas putida with a yield of 1.85 g/L. Prodigiosin was prepared under acidic, neutral, and alkaline conditions, resulting in varying protonation states that influenced its affinity for cotton and polyester fibers. Three surfactants (anionic, cationic, non-ionic) were tested, with non-ionic Tween 80 yielding a promising color strength (above 4) and fastness results with neutral prodigiosin at 1.3 g/L. Cotton and polyester demonstrated good washing (color difference up to 14 for cotton, 5 for polyester) and light fastness (up to 15 for cotton, 16 for polyester). Cellulose acetate, used in the conventional printing process as a thickener, produced superior color properties compared to commercial thickeners. Neutral prodigiosin achieved higher color strength, and cotton fabrics displayed halochromic properties, distinguishing them from polyester, which showed excellent fastness. Prodigiosin-printed samples also exhibited strong antimicrobial activity against Pseudomonas aeruginosa and retained halochromic properties over 10 pH cycles. These findings suggest prodigiosin as a sustainable dye alternative and pH sensor, with potential applications in biomedical materials, such as antimicrobial and pH-responsive wound dressings. Full article

Developing innovative, low-cost halochromic materials for diagnosing microbial contamination in wounds and burns can effectively facilitate tissue regeneration. Here, we combine the pH-sensing capability of highly colorful red cabbage anthocyanins (RCAs) with their healing potential within a unique cellulose polymer film that mimics the skin matrix. Biological activities of RCA extract in bacterial cellulose (BC) showed no cytotoxicity and skin-sensitizing potential to human cells at concentrations of RCAs similar to those released from BC/RCA dressings (4.0–40.0 µg/mL). A decrease in cell viability and apoptosis was observed in human cancer cells with RCAs. The invisible eye detection of the early color change signal from RCAs in response to pH alteration by bacteria was recorded with a smartphone application. The incorporation of RCAs into BC polymer has altered the morphology of its matrix, resulting in a denser cellulose microfibril network. The complete coincidence of the vibrational modes detected in the absorption spectra of the cellulose/RCA composite with the modes in RCAs most likely indicates that RCAs retain their structure in the BC matrix. Affordable, sensitive halochromic BC/RCA hydrogels can be recommended for online monitoring of microbial contamination, making them accessible to patients. Full article

The pH level of a wound environment is a crucial biomarker for monitoring wound healing, particularly in chronic wounds, where alkalinity (pH > 7) is linked to bacterial colonization and infection. This study developed and optimized a halochromic sensor film composed of polyvinyl alcohol (PVA), polyethylene glycol (PEG), and bromothymol blue (BTB) to enable rapid and reliable pH-responsive color transitions. Feature selection using Principal Component Analysis (PCA) and the ReliefF algorithm identified Hue, Saturation, and a as key features influencing pH responsivity. Optimization of BTB (0.01–0.05%) and PEG (6–10%) concentrations was conducted using bird-inspired metaheuristic algorithms, including the Parrot Optimizer (PO), Pelican Optimization Algorithm (POA), and Secretary Bird Optimization Algorithm (SBOA). While final fitness values showed negligible variation (188.595647 for GP-PO, 188.595634 for GP-POA, and 188.595634 for GP-SBOA), GP-PO demonstrated superior convergence and stability, efficiently identifying the optimal formulation (0.02% BTB, 6% PEG). The optimized film achieved a complete color transition within 3–5 min, a 23.15% reduction compared to the non-optimized formulation. Statistical analysis revealed that BTB concentration significantly affected response time (p = 0.01), while PEG concentration had no significant effect (p > 0.05). These findings highlight the potential of halochromic films for real-time, non-invasive pH monitoring in chronic wounds. Full article

The incorporation of biopolymers and natural colorants in smart packaging has garnered significant attention in the food packaging industry. This study investigates the design and characterization of novel fibrous films incorporating betalain extract (BE) from Stenocereus thurberi in poly (lactic acid) (PLA). An electrospinning technique was developed with varying PLA concentrations (2%–12% w/v) and BE concentrations (8%–12% w/v) to create a colorimetric freshness indicator. BE was characterized by quantifying its phytochemical content and assessing its antioxidant capacity. Morphological and structural analyses included scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), polydispersity index (PI), mechanical properties, and functional characteristics such as ammonia sensitivity and total antioxidant activity. The results indicated that the incorporation of BE significantly influenced the average diameter of the nanofibers, ranging from 313 ± 74 nm to 657 ± 99 nm. SEM micrographs showed that PLA12-BE12 films exhibited smooth surfaces without bead formation. The FTIR analysis confirmed effective BE incorporation, revealing intermolecular interactions between the betalain molecules and the PLA matrix, which contributed to enhanced structural and functional stability. The mechanical properties analysis revealed that moderate BE additions (8%–10% w/v) enhanced the Young’s modulus and tensile strength, while higher BE concentrations (12% w/v) disrupted the polymer network, reducing these properties. Additionally, the strain at break decreased significantly with BE incorporation, reflecting limited molecular chain mobility. Increasing BE concentration notably improved antioxidant activity, with the BE concentration of 12% (w/v), the ABTS•+, DPPH•, and FRAP radical scavenging activities at the highest values of 84.28 ± 1.59%, 29.95 ± 0.34%, and 710.57 ± 28.90 µM ET/g, respectively. Ammonia sensitivity tests demonstrated a significant halochromic transition from reddish-pink to yellow, indicating high sensitivity to low ammonia concentrations. The possible mechanism is alkaline pH induces aldimine bond hydrolysis and generates betalamic acid (yellow) and cyclo-DOPA-5-O-ß-glucoside (colorless) The fibrous films also exhibited reversible color changes and maintained good color stability over 30 days, emphasizing their potential for use in smart packaging applications for real-time freshness monitoring and food quality assessment. Full article

Polymer-based dressings deriving from natural biomaterials have advantages such as nontoxicity, biocompatibility, and mechanical stability, which are essential for efficient wound healing and microbial infection diagnostics. Here, we designed a prototype of an intelligent hydrogel dressing on the base of bacterial cellulose (BC) for monitoring wound microbial infection due to the uploaded natural pH dye-sensor, anthocyanins (ANC) of elderberry fruit (Sambucus nigra L.). The highest sensor responses to bacterial metabolites for ANC immobilized to BC were observed at pH 5.0 and 6.0. The detection limit of the sensor signals was 3.45 A.U., as it was evaluated with a smartphone-installed application. The FTIR spectral analysis of the hybrid BC/ANC hydrogel films has proved the presence of anthocyanins within the BC matrix. Hybrid films differed from the control ones by thicker microfibrils and larger pores, as detected with scanning electron microscopy. Halochromic BC/ANC films exhibited antimicrobial activities mainly against gram-positive bacteria and yeast. They showed no cytotoxicity for the in vitro human cell lines and mouse fibroblasts within a selected range of anthocyanin concentrations released from the BC/ANC film/dressing prototype. Compared to the control, the in vitro healing test showed overgrowth of primary mouse fibroblasts after applying 0.024–2.4 µg/mL ANC. Full article

Turmeric has been widely studied as a color indicator for pH variations due to its halochromic properties. It has been tested in solution or included in some polymeric matrices. Some studies have demonstrated that its change in color is due to the tautomeric species of curcumin, and this property can be observed even if turmeric is assimilated in a film or nanofiber. Chitosan/polyethylene oxide (PEO) polymers have been tested in previous studies. Polyvinyl alcohol (PVA) nanofibers are used as potential carriers of drugs once they are insolubilized. The aim of this work is to cross-link PVA with citric acid (CA) to insolubilize the nanofibers and determine the effect on turmeric’s halochromic properties. The nanofibers were treated with a sodium hydroxide (NaOH) solution, and a chromatic study was undertaken to determine color change. The change in color was assessed by eye (subjective) and by spectroscopy (objective). The nanofibers were characterized, in addition to the colorimetric study, by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) as well. The results demonstrate how thermal treatment induces cross-linking between the nanofibers, allowing them to keep their shape once the NaOH solution is applied to them. The opposite effect (solubilization) can be observed for non-cross-linked (NCL) samples. Although the final color varied, the cross-linked (CL) nanofibers’ halochromic behavior was maintained. It was demonstrated that during cross-linking, ester groups are formed from the free carboxyl group in the cross-linked CA and the ketones present in the curcumin under acid conditions. So, CA acts as an acid catalyst to bond turmeric to the cross-linked PVA nanofibers. Full article

Thanks to the intensive development of textronics, textronic applications are already visible in many areas of everyday life. Many researchers around the world have focused on the invention of textronic systems to increase security, create technological innovations and make everyday life easier and more interesting. Due to the wide use of chemical textile sensors, this review article lists scientific publications covering all types of wearable chemical sensors along with their latest developments. The latest developments from the last few years in moisture, pH, sweat and biomolecules sensors are described. In this review, greatest emphasis and detail was placed on textile gas sensors and their production methods. The use of, among others, graphene and zinc oxide grown on cotton fabric, colorimetric textiles based on halochromic dye, electronic graphene fabric based on lotus fibers and graphene oxide and zinc oxide nanorods were considered. Finally, this article summarizes our current knowledge on gas sensors, compares the detection properties of the presented projects and indicates future directions of development. Full article

Petroleum-derived polymers, such as polyethylene and polypropylene, are commonly used in food packing industries knowing the fact that these polymers cause serious threats to the ecosystem. Therefore, the development of low-cost, environmentally friendly, and biodegradable polymers to address this issue is an urgent need of the hour. Bacterial nanocellulose (BNC), with its extraordinary and differentiated properties, is gaining special attention in the food packaging industry. To reduce the cost, several low-cost substrates are utilized for the production of BNC. Therefore, the present study is focused on the production of low-cost BNC and its subsequent functionalization for smart packaging applications. Full article

Chemical protective clothing (CPC) has become mandatory when performing various tasks to ensure user protection and prevent chemicals from contacting the skin and causing severe injuries. In addition to protection, there is a need to develop a simple mechanism that can be attached to CPC and be capable of detecting and alerting the user to the presence of harmful chemical agents. In this study, a double-sensor strategy was investigated, using six different pH indicators stamped on cotton and polyester knits to detect acidic and alkaline substances, both liquid and gaseous. Functionalized knits underwent microscopic characterization, air permeability and contact angle evaluation. All samples exhibited hydrophobic behavior (contact angle > 90°) and air permeability values above 2400 L/min/cm²/bar, with the best condition demonstrating a contact angle of 123° and an air permeability of 2412.5 L/min/cm²/bar when the sensor methyl orange and bromocresol purple (MO:BP) was stamped on polyester. The performed tests proved the functionality of the sensors and showed a visible response of all knits when contacting with different chemicals (acids and bases). Polyester functionalized with MO:BP showed the greatest potential, due to its preeminent color change. Herein, the fiber coating process was optimized, enabling the industrial application of the sensors via a stamping method, an alternative to other time- and resource-consuming techniques. Full article

Today, smart indicators especially based on pigments and natural biopolymers have developed significantly in laboratory and industrial scale. In addition to tracking the freshness and spoilage of the product, these intelligent systems inform the consumer about the quality of the packaged product without opening the package. On the other hand, they reduce food waste and minimize food poisoning. In this study, two halochromic smart indicators were constructed by encapsulating saffron petal and barberry anthocyanins in gelatin/chitin nanofiber films for indication of the freshness/spoilage of fish fillets. Insights into the molecular, structural, and optical properties of these indicators were obtained using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy, and colorimetry analyses. The results showed that the indicators had smooth surfaces and that the pigments were evenly distributed throughout the biopolymer network. The barberry and saffron anthocyanin solutions underwent color changes from reddish to yellow for barberry and reddish to pink to violet to greenish and yellow for saffron anthocyanin after being exposed to different pH values (1–14). The change in appearance of halochromic indicators was quantified by measuring their color coordinates (L*, a*, b*). When applied for estimating fish spoilage, the color of the G/ChNF/BA and G/ChNF/SPA indicators turned from pink to yellow and from violet to green, respectively. After 3 days of storage, the pH and total volatile basic nitrogen of fish fillets reached 8.0 and 49.06 mg N/100 g, respectively. Therefore, a direct relationship between the increase in pH values, the increase in volatile nitrogen bases content, and the changes in the color of the smart indicator applied to monitor the fish was observed. The simulation tests showed that pH-responsive smart indicators can reveal visually fish fillets freshness in real time prior to the point of consumption. Full article

The interest in pH-sensitive textile sensors is growing in the global market. Due to their low-cost production, mechanical stability, flexibility, air-permeability, washability, and reusability, they are more suitable than electronic sensor systems. The research tailored the pH-sensitive textile by applying the pH indicator methyl orange to the cotton fabric during conventional dyeing. Adsorption of methyl orange dye to cotton fabric is hindered due to electrostatic repulsive forces between dye anions and negatively charged cotton fibre. To overcome this problem, chemical modification of cotton fabric using a commercial product was performed. The pH sensitivity of the dyed fabric was spectrophotometrically evaluated. In addition, the colour fastness of dyed cotton fabric to washing, light, hot pressing and rubbing was investigated according to valid SIST EN ISO standards. The research results show that the pH-responsive cotton fabric was successfully developed. The chemical modification of cotton fabric is crucial for the increased adsorption of methyl orange dye. The halochromic effect was not only perceived spectrophotometrically but also with the naked eye. The developed halochromic cotton fabric showed poor colour fastness to light and good colour fastness to hot pressing and rubbing, while no significant improvement in colour fastness to washing was observed, even though the fabric was after-treated with a cationic fixing agent. Higher adsorption of the methyl orange dye to the cotton fabric during the dyeing process leads to less wastewater pollution after dyeing with unfixed dye and, thus, a reduction in wastewater treatment costs. Full article

Textiles are important components for the development of lightweight and flexible displays useful in smart materials. In particular, halochromic textiles are fibrous materials with a color-changing ability triggered by pH variations mainly based on pH-sensitive dye molecules. Recently, a novel class of 2-aminoimidazole azo dyes was developed with distinct substituent patterns. In this work, silk fabric was functionalized through exhaustion for the first time with one of these dyes (AzoIz.Pip). The halochromic properties of the dye were assessed in an aqueous solution and after silk functionalization. The solutions and the fabrics were thoroughly analyzed by ultraviolet-visible (UV-vis) spectra, color strength (K/S), color difference (∆E), CIE L*a*b* coordinates, and the ultraviolet protection factor (UPF). The dyeing process was optimized, and the halochromic performance (and reversibility) was assessed in universal Britton–Robinson buffers (ranging from pH 3 to 12) and artificial body fluids (acid and alkaline perspiration, and wound exudate). AzoIz.Pip showed vibrant colors and attractive halochromic properties with a hypsochromic shift from blue (557 nm) to magenta (536 nm) in aqueous buffered solutions. Similarly, the functionalized silk showed a shift in wavelength of the maximum K/S value from 590 nm to 560 nm when pH increases. The silk fabric showed a high affinity to AzoIz.Pip, and promoted additional color stabilization of the dye, avoiding color loss as observed when the dye is in solution at alkaline pH after 24 h. The color reversibility was effective up to the fourth cycle and the fastness tests denoted suitable results, except washing fastness. The cytotoxicity of the silk fabric extracts was assessed, depicting reduced viability of HaCaT cells to <70% only when the dye concentration in the fabric is higher or equal to 64 μg·mL⁻¹. Nevertheless, lower concentrations were also very effective for the halochromic performance in silk. These materials can thus be a helpful tool for developing sensors in several sectors such as biomedicine, packaging, filtration, agriculture, protective apparel, sports, camouflage, architecture, and design. Full article

This work is focused on the age-old challenge of developing optical sensors for acidity measurements in low-pH aqueous solutions (pH < 5). We prepared halochromic (3-aminopropyl)amino-substituted quinoxalines QC1 and QC8 possessing different hydrophilic–lipophilic balance (HLB) and investigated them as molecular components of pH sensors. Embedding the hydrophilic quinoxaline QC1 into the agarose matrix by sol-gel process allows for fabrication of pH responsive polymers and paper test strips. The emissive films thus obtained can be used for a semi-quantitative dual-color visualization of pH in aqueous solution. Being exposed to acidic solutions with pH in the range of 1–5, they rapidly give different color changes when the analysis is performed in daylight or under irradiation at 365 nm. Compared with classical non-emissive pH indicators, these dual-responsive pH sensors allow for an increase in the accuracy of pH measurements, particularly in complex environmental samples. pH indicators for quantitative analysis can be prepared by the immobilization of amphiphilic quinoxaline QC8 using Langmuir–Blodgett (LB) and Langmuir–Schäfer (LS) techniques. Compound QC8 possessing two long alkyl chains (n-C₈H₁₇) forms stable Langmuir monolayers at the air–water interface, and these monolayers can be successfully transferred onto hydrophilic quartz and hydrophobic polyvinylchlorid (PVC) substrates using LB and LS techniques, respectively. The 30-layer films thus obtained are emissive, reveal excellent stability, and can be used as dual-responsive pH indicators for quantitative measurements in real-world samples with pH in the range of 1–3. The films can be regenerated by immersing them in basic aqueous solution (pH = 11) and can be reused at least five times. Full article

In this study, the antioxidant, antimicrobial, mechanical, optical, and barrier attributes of Solanum lycocarpum starch bio-based edible films incorporated with a phenolic extract from jaboticaba peel were investigated. Aiming to determine the effect of the polymers and the phenolic extract on the properties of the films, a three-factor simplex-lattice design was employed, and the formulation optimization was based on the produced films’ antioxidant potential. The optimized formulation of the starch-PEJP film showed a reddish-pink color with no cracks or bubbles and 91% antioxidant activity against DPPH radical. The optimized starch-PEJP film showed good transparency properties and a potent UV-blocking action, presenting color variation as a function of the pH values. The optimized film was also considerably resistant and highly flexible, showing a water vapor permeability of 3.28 × 10⁻⁶ g m⁻¹ h⁻¹ Pa⁻¹. The microbial permeation test and antimicrobial evaluation demonstrated that the optimized starch-PEJP film avoided microbial contamination and was potent in reducing the growth of Escherichia coli, Staphylococcus aureus, and Salmonella spp. In summary, the active starch-PEJP film showed great potential as an environmentally friendly and halochromic material, presenting antioxidant and antimicrobial properties and high UV-protecting activity. Full article

Xanthylium derivatives are curcumin analogs showing photochromic properties. Similarly, to anthocyanins, they follow the same multistate network of chemical species that are reversibly interconverted by external stimuli. In the present work, two new asymmetric monocarbonyl analogues of curcumin, 4-(4-hydroxy-3-metoxybenzylidene)-1,2,3,4-tetrahydroxanthylium chloride (compound 3) and 4-(4-hydroxybenzylidene)-6-methoxy-1,2,3,4-tetrahydroxanthylium chloride (compound 4) were synthesized, and their photochromic and biological properties were investigated. The UV-Vis spectroscopy and the direct and reverse pH-jumps studies confirmed the halochromic properties and the existence of different molecular species. A network of chemical reactions of these species was proposed. Furthermore, the antiproliferative properties of both compounds were evaluated using P19 murine embryocarcinoma cells and compared with each other. The results demonstrate that both new xanthylium derivatives modify the progression through the cell cycle of P19 cells, which translates into a significant antiproliferative effect. The effect of the methoxy group position is discussed and several checkpoint proteins are advanced as putative targets. Full article