The Development of Indicator Cotton Swabs for the Detection of pH in Wounds

A pH visual sensing platform based on dual-emission chiral carbon dots for discrimination of normal/cancer cells and monitoring food freshness

Accurate detection of pH is important in pathological processes and food freshness. Developing sensors of sensitive response and visualization for pH is highly demanded. In this work, Chiral carbon dots (CCDs) was synthesized via one-pot hydrothermal process using o-phenylenediamine and L-Tryptophan, which displayed circular dichroism (CD) signals at 200-255 nm and 255-300 nm. The CCDs exhibited dual-emission peaks with blue and red emission bands when excited at 360 nm. The ratiometric signals of UV-vis absorption and fluorescence intensity of L-CDs were responsive over the pH range of 2.0-11.0 with significant color changes in solution. Fluorescence imaging of live cells displayed different signals related to pH in both the blue and red channels, allowing accurate measurement of the pH of the cellular environment. Furthermore, the pH test paper based on L-CDs enabled monitoring the freshness of shrimp and pork under 365 nm UV light. Therefore, L-CDs provided a multifunctional visual pH sensing platform for environmental monitoring and biosensing.

Evaluation of smart bi-functional dressing based on polysaccharide hydrogels and Brassica oleracea extract for wound healing and continuous monitoring

Skin wounds can drive global impacts, socially and economically, in parallel with their elevated incidence rate. Therefore, utilizing the dual-activity of Brassica Oleracea (Red Cabbage) extract, of being pH-sensitive and biologically active in designing novel, therapeutic, and pH-sensitive wound dressings with an easily stripped-off feature, is critical. Wound dressings were designed using two separate hydrogels based on chitosan (CS) and hydroxyethylcellulose (HEC), each loaded with RCE. The pH sensitivity of prepared bandages exhibited a noticeable visual change in color during wound treatment. Wound closure has reached 99.69 % for CS/RCE dressings. Results showed that RCE had raised the hydroxyproline and collagen content in the healed skin. Histopathological investigation proves that skin returned to its regular thickness within 10 days of treatment. RCE showed marked improvement in the healing quality by acting as an antioxidant, anti-inflammatory, and antimicrobial agent. Therefore, dual-function dressings are potential candidates to sense and cure skin wounds.

A response surface methodology study on the development of pH-sensitive wound dressings using Rhodamine B-loaded chitosan nanoparticles and sodium alginate-based films

Purpose

This study aimed to develop an innovative, intelligent wound dressing capable of signaling infections through color changes.

Design/methodology/approach

Using response surface methodology, the Rhodamine B fluorescence colorant was encapsulated within colloidal nanoparticles and integrated into a sodium alginate patch at various concentrations. The physical and chemical characteristics of the nanoparticles and the wound dressing were thoroughly analyzed via dynamic light scattering (DLS), zeta potential measurements, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Additionally, the biodegradability, hydrophilicity, swelling behavior, release kinetics, porosity, mechanical properties, biocompatibility, and infection detection capability of the wound dressing were evaluated.

Findings

The results indicated that the average diameter of the synthesized colloidal nanoparticles was 300 nm before loading with Rhodamine B and increased to 400 nm after loading, with zeta potentials of 52 mV and -6 mV, respectively. The Rhodamine B-loaded wound dressing demonstrated adequate levels of swelling and hydrophilicity. Release studies revealed the gradual release of Rhodamine B at low pH. Cytotoxicity assays confirmed the high biocompatibility of the engineered wound dressing with the L929 cell line. Furthermore, bacterial exposure experiments indicated that the color change was activated in the presence of infection, making it visible under UV-A light.

Originality/value

This research presents a novel approach to wound care by developing a smart wound dressing that can detect infections via color changes. These findings underscore the potential of this innovative wound dressing to improve infection management in clinical settings through its responsive and biocompatible design.

β-Galactosidase-triggered in situ synthesis of yellow emitting silicon nanoparticle and its application in visual detection of E. coli O157:H7 and drug susceptibility test

The sensitive detection of foodborne pathogenic and rapid antibiotic susceptibility testing (AST) is of great significance. This paper reports the enzyme-triggered in situ synthesis of yellow emitting silicon nanoparticles (SiNPs) and the detection of Escherichia coli (E. coli) O157:H7 in food samples and the rapid AST. The rapid counting of E. coli O157:H7 has been achieved through direct visual observation, equipment detection, and smartphone digitalization. A simple detection platform based on smartphone senses and cotton swabs has been established. Meanwhile, rapid AST based on enzyme-catalyzed SiNPs can intuitively obtain colorimetric samples. This paper established a system for bacterial enzyme-triggered in situ synthesis of SiNPs, with high responsiveness, luminescence ratio, and specificity. The detection limit for E. coli O157:H7 can reach 100 CFU/mL during 5 h, and the recovery efficiency ranges from 90.14% to 110.16%, which makes it a promising strategy for the rapid detection of E. coli O157:H7 and AST.

Dual-crosslinked bioadhesive hydrogel as NIR/pH stimulus-responsiveness platform for effectively accelerating wound healing

Adhesive hydrogels have emerged as promising candidates to solve life-threatening infectious skin injuries. However, the inadequate mechanical characteristics and biological adherence limit the traditional wound dressing unable to adapt to high-frequency movement and real-time monitoring of wound healing, calling for the development of bioadhesive materials guided wound healing. In this work, a multifunctional bioadhesive hydrogel with double colorimetric-integrated of polyethylene glycol (PVA)-dextran (Dex)-borax-bromothymol blue (BTB)-fluorescein thiocyanate (FITC) and functionalization by tungsten disulfide-catechol nanozyme (CL/WS₂) was created. Hydrogel is a perfect biological adhesive, which can achieve repeatable and strong tissue adhesion strength (8.3 ± 0.6 kPa), which is 1.66 times that of commercial dressings. Based on the strong biological adhesion of the hydrogel, a sensor is integrated into the hydrogel to collect visual image of bacterial infection from a smartphone and transform it into an on-site pH signal for remote evaluation of the wound's dynamic status in real time. Ultimately, the adhesiveness hydrogel has high worth in managing the burden related to wound healing and paving the way for intelligent wound management in the future.

Formation of pH-Responsive Cotton by the Adsorption of Methyl Orange Dye

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.

A collagen-based theranostic wound dressing with visual, long-lasting infection detection capability

Continuous wound monitoring is one strategy to minimise infection severity and inform prompt variations in therapeutic care following infection diagnosis. However, integration of this functionality in therapeutic wound dressings is still challenging. We hypothesised that a theranostic dressing could be realised by integrating a collagen-based wound contact layer with previously demonstrated wound healing capability, and a halochromic dye, i.e. bromothymol blue (BTB), undergoing colour change following infection-associated pH changes (pH: 5-6 ➔ >7). Two different BTB integration strategies, i.e. electrospinning and drop-casting, were pursued to introduce long-lasting visual infection detection capability through retention of BTB within the dressing. Both systems had an average BTB loading efficiency of 99 wt% and displayed a colour change within 1 min of contact with simulated wound fluid. Drop-cast samples retained up to 85 wt% of BTB after 96 h in a near-infected wound environment, in contrast to the fibre-bearing prototypes, which released over 80 wt% of BTB over the same time period. An increase in collagen denaturation temperature (DSC) and red shifts (ATR-FTIR) suggest the formation of secondary interactions between the collagen-based hydrogel and the BTB, which are attributed to count for the long-lasting dye confinement and durable dressing colour change. Given the high L929 fibroblast viability in drop-cast sample extracts (92 %, 7 days), the presented multiscale design is simple, cell- and regulatory-friendly, and compliant with industrial scale-up. This design, therefore, offers a new platform for the development of theranostic dressings enabling accelerated wound healing and prompt infection diagnosis.

A Systematic Review on the Advanced Techniques of Wearable Point-of-Care Devices and Their Futuristic Applications

Personalized point-of-care testing (POCT) devices, such as wearable sensors, enable quick access to health monitoring without the use of complex instruments. Wearable sensors are gaining popularity owing to their ability to offer regular and continuous monitoring of physiological data by dynamic, non-invasive assessments of biomarkers in biofluids such as tear, sweat, interstitial fluid and saliva. Current advancements have concentrated on the development of optical and electrochemical wearable sensors as well as advances in non-invasive measurements of biomarkers such as metabolites, hormones and microbes. For enhanced wearability and ease of operation, microfluidic sampling, multiple sensing, and portable systems have been incorporated with materials that are flexible. Although wearable sensors show promise and improved dependability, they still require more knowledge about interaction between the target sample concentrations in blood and non-invasive biofluids. In this review, we have described the importance of wearable sensors for POCT, their design and types of these devices. Following which, we emphasize on the current breakthroughs in the application of wearable sensors in the realm of wearable integrated POCT devices. Lastly, we discuss the present obstacles and forthcoming potentials including the use of Internet of Things (IoT) for offering self-healthcare using wearable POCT.

Challenges and innovations in treating chronic and acute wound infections: from basic science to clinical practice

Acute and chronic wound infection has become a major worldwide healthcare burden leading to significantly high morbidity and mortality. The underlying mechanism of infections has been widely investigated by scientist, while standard wound management is routinely been used in general practice. However, strategies for the diagnosis and treatment of wound infections remain a great challenge due to the occurrence of biofilm colonization, delayed healing and drug resistance. In the present review, we summarize the common microorganisms found in acute and chronic wound infections and discuss the challenges from the aspects of clinical diagnosis, non-surgical methods and surgical methods. Moreover, we highlight emerging innovations in the development of antimicrobial peptides, phages, controlled drug delivery, wound dressing materials and herbal medicine, and find that sensitive diagnostics, combined treatment and skin microbiome regulation could be future directions in the treatment of wound infection.

Development of green and sustainable smart biochromic and therapeutic bandage using red cabbage (Brassica oleracea L. Var. capitata) extract encapsulated into alginate nanoparticles

Novel multifunctional wound dressing with the ability to protect, cure and sense the healing process, was developed. Red-cabbage extract has been reported to exhibit bioactive compounds with the ability to function as antioxidant, antiinflammatory, anticancer, antibacterial, antifungal, and antiviral agent, as well as a natural pH-sensory chromophoric material. An anthocyanin extract was prepared from Red-cabbage (Brassica oleracea L. Var. capitata). The anthocyanins extract was encapsulated into calcium alginate in the presence of potash alum mordant, which was then applied to the surface of the cotton gauze. Red-cabbage based anthocyanin chromophoric extract was encapsulated at different concentrations into alginate-based hydrogel and immobilized into cotton gauze to provide a smart therapeutic pH-responsive wound dress to function as an antimicrobial and biochromic matrix providing a comfortable dress sensor to monitor the wound status. Decreasing the pH of a wound mimic solution caused a blue shift from 579 to 437 nm. The anthocyanin spectroscopic probe's halochromic activity demonstrated a colorimetric change from purple to pink, which was critical to the dyed cotton diagnostic assay's biochromic performance. The colorimetric parameters of the prepared dressing sensor were proved by UV-Vis absorbance and CIE Lab coordinates. Both mechanical and morphological properties of the prepared dressing were studied using different analytical methods. The effect of anthocyanin concentration on the mechanical, water vapor permeability, water absorption and morphological properties of the wound dressing were investigated. No substantial flaws in air-permeability or bend length were detected after dyeing. The colored cotton gauze samples were tested for their high colorfastness. The cytotoxicity and antimicrobial activity of the prepared biochromic cotton gauze were explored. The dyed cotton samples exhibited no cytotoxicity and improved antimicrobial activity with increasing the anthocyanin ratio on cotton surface.

Recent Advances in Wearable Potentiometric pH Sensors

Wearable sensors reflect the real-time physiological information and health status of individuals by continuously monitoring biochemical markers in biological fluids, including sweat, tears and saliva, and are a key technology to realize portable personalized medicine. Flexible electrochemical pH sensors can play a significant role in health since the pH level affects most biochemical reactions in the human body. pH indicators can be used for the diagnosis and treatment of diseases as well as the monitoring of biological processes. The performances and applications of wearable pH sensors depend significantly on the properties of the pH-sensitive materials used. At present, existing pH-sensitive materials are mainly based on polyaniline (PANI), hydrogen ionophores (HIs) and metal oxides (MOx). In this review, we will discuss the recent progress in wearable pH sensors based on these sensitive materials. Finally, a viewpoint for state-of-the-art wearable pH sensors and a discussion of their existing challenges are presented.

Screen Printing of pH-Responsive Dye to Textile

The development of pH-responsive textile sensors has attracted much interest in recent decades. Therefore, the aim of this study was to show that screen printing could be one of the possible techniques for development of pH-responsive textile. Several parameters that could influence the pH sensitivity and responsivity of a screen-printed textile with bromocresol green dye were studied, such as textile substrate (cotton, polyamide), printing paste composition, and type of fixation (heat and steaming). The change in mechanical and physical properties of the printed fabrics was tested according to the valid ISO, EN, or ASTM standards. The responsiveness of the printed samples to different pH values with the change in colour was evaluated spectrophotometrically. In addition, the colour fastness of the printed textiles to rubbing, washing, and light was also investigated. The results show that the textile responsiveness to pH change was successfully developed by flat screen-printing technique, which proves that the printing process could be one of the methods for the application of indicator dye to textiles. The application of the printing paste to cotton and polyamide fabrics resulted in an expected change in the mechanical and physical properties of the fabrics studied. The responsiveness of printed fabrics to the change of pH value depends on the type of fibres, the strength of dye-fibre interactions, and the wettability of the fabric with buffer solutions. The colour fastness of the printed fabrics to dry and wet rubbing is excellent. Printed polyamide fabric is more resistant to washing than printed cotton fabric. Both printed fabrics have poor colour fastness to light.

Preparation and characterization of smart therapeutic pH-sensitive wound dressing from red cabbage extract and chitosan hydrogel

Developing a multifunctional wound dressing that protects, cures and indicates the healing progress, is a new approach of investigation. Red cabbage extract (RCE), consisting of bioactive compounds that have antioxidant, anti-inflammatory, anti-carcinogenic, bactericidal, antifungal, and antiviral activities, was utilized as a natural pH-sensitive indicator. Chitosan-based hydrogel, encapsulating RCE, was developed to obtain a smart therapeutic pH-sensitive wound dressing as antimicrobial bio-matrix provides a comfortable cushion for wound bed and indicates its status. Methacrylated-chitosan was crosslinked by different concentrations of methylenebisacrylamide (MBAA) by which hydrogel mechanical and morphological properties were tuned. The proposed mechanism for hydrogel formation was confirmed by FT-IR. The coloristic properties of the RCE and the changes in color intensity as a function of pH were confirmed by UV-Vis spectroscopy. The effect of MBAA on the mechanical, swelling, release and morphological properties of hydrogel were investigated. MBAA (2.5% wt/v) in 2% wt/v chitosan showed preferable mechanical (20 KPa), swelling (1294% at pH 8 ± 0.2), and release (prolonged up to 5 days) properties. Hydrogel matrices, loaded on cotton gauze submerged in different pH buffer solutions, showed explicit color changes from green to red as pH changed from 9 to 4.

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

This is the first comprehensive review on methods and materials for use in optical sensing of pH values and on applications of such sensors. The Review starts with an introduction that contains subsections on the definition of the pH value, a brief look back on optical methods for sensing of pH, on the effects of ionic strength on pH values and pKa values, on the selectivity, sensitivity, precision, dynamic ranges, and temperature dependence of such sensors. Commonly used optical sensing schemes are covered in a next main chapter, with subsections on methods based on absorptiometry, reflectometry, luminescence, refractive index, surface plasmon resonance, photonic crystals, turbidity, mechanical displacement, interferometry, and solvatochromism. This is followed by sections on absorptiometric and luminescent molecular probes for use pH in sensors. Further large sections cover polymeric hosts and supports, and methods for immobilization of indicator dyes. Further and more specific sections summarize the state of the art in materials with dual functionality (indicator and host), nanomaterials, sensors based on upconversion and 2-photon absorption, multiparameter sensors, imaging, and sensors for extreme pH values. A chapter on the many sensing formats has subsections on planar, fiber optic, evanescent wave, refractive index, surface plasmon resonance and holography based sensor designs, and on distributed sensing. Another section summarizes selected applications in areas, such as medicine, biology, oceanography, bioprocess monitoring, corrosion studies, on the use of pH sensors as transducers in biosensors and chemical sensors, and their integration into flow-injection analyzers, microfluidic devices, and lab-on-a-chip systems. An extra section is devoted to current challenges, with subsections on challenges of general nature and those of specific nature. A concluding section gives an outlook on potential future trends and perspectives.

Sulfated Polysaccharides from Marine Algae as a Basis of Modern Biotechnologies for Creating Wound Dressings: Current Achievements and Future Prospects

Wound healing involves a complex cascade of cellular, molecular, and biochemical responses and signaling processes. It consists of successive interrelated phases, the duration of which depends on a multitude of factors. Wound treatment is a major healthcare issue that can be resolved by the development of effective and affordable wound dressings based on natural materials and biologically active substances. The proper use of modern wound dressings can significantly accelerate wound healing with minimum scar mark. Sulfated polysaccharides from seaweeds, with their unique structures and biological properties, as well as with a high potential to be used in various wound treatment methods, now undoubtedly play a major role in innovative biotechnologies of modern natural interactive dressings. These natural biopolymers are a novel and promising biologically active source for designing wound dressings based on alginates, fucoidans, carrageenans, and ulvans, which serve as active and effective therapeutic tools. The goal of this review is to summarize available information about the modern wound dressing technologies based on seaweed-derived polysaccharides, including those successfully implemented in commercial products, with a focus on promising and innovative designs. Future perspectives for the use of marine-derived biopolymers necessitate summarizing and analyzing results of numerous experiments and clinical trial data, developing a scientifically substantiated approach to wound treatment, and suggesting relevant practical recommendations.

Continuous pH monitoring in wounds using a composite indicator dressing - A feasibility study

PURPOSE

Modern burn care strives for new means to guarantee optimised wound healing. Several studies have shown a correlation between the pH value in a (burn) wound and successful wound healing. A multitude of devices to monitor pH is available, all requiring direct wound contact and removal of the dressing for pH monitoring. The aim of this feasibility study was to create a sterile and easy to handle method for pH monitoring while simultaneously using an advanced wound dressing.

MATERIALS AND METHODS

Dressing sheets of biotechnologically generated nanofibrillar cellulose (epicite^hydro) were chemically functionalised with the indicator dye GJM-534. pH-donors with increasing pH were subsequently applied to the created indicator dressing. To investigate temporal resolution and continuous monitoring we used circular pH-donors with different pH (7 and 10) and decreasing diameters that were placed on another dressing sheet. Clinically relevant spatial resolution was checked by a wound bed simulation with small areas (8 mm) of higher pH (10) on a field of lower pH (7) and vice versa.

RESULTS

The indicator dressing showed a gradual colouring from yellow to dark orange with increasing pH in steps of 0.3. After conversion of digital pictures to greyscale values, a sigmoidal distribution with a pK_a-value of 8.4 was obtained. A ring-like pattern with alternating colour change corresponding to the pH was observed in the continuous monitoring experiment and the wound bed simulation delivered excellent local resolution.

CONCLUSION

Since the pH of a (burn) wound can have a significant influence on wound healing, a pH indicator was successfully linked to an advanced, temporary, alloplastic wound dressing material. We were able to show the possibility of pH monitoring by the dressing itself. Additional testing, including studies with large case numbers for optimisation are necessary before clinical implementation.

Two-layer Electrospun System Enabling Wound Exudate Management and Visual Infection Response

The spread of antimicrobial resistance calls for chronic wound management devices that can engage with the wound exudate and signal infection by prompt visual effects. Here, the manufacture of a two-layer fibrous device with independently-controlled exudate management capability and visual infection responsivity was investigated by sequential free surface electrospinning of poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) and poly(acrylic acid) (PAA). By selecting wound pH as infection indicator, PMMA-co-MAA fibres were encapsulated with halochromic bromothymol blue (BTB) to trigger colour changes at infection-induced alkaline pH. Likewise, the exudate management capability was integrated via the synthesis of a thermally-crosslinked network in electrospun PAA layer. PMMA-co-MAA fibres revealed high BTB loading efficiency (>80 wt.%) and demonstrated prompt colour change and selective dye release at infected-like media (pH > 7). The synthesis of the thermally-crosslinked PAA network successfully enabled high water uptake (WU = 1291 ± 48 - 2369 ± 34 wt.%) and swelling index (SI = 272 ± 4 - 285 ± 3 a.%), in contrast to electrospun PAA controls. This dual device functionality was lost when the same building blocks were configured in a single-layer mesh of core-shell fibres, whereby significant BTB release (~70 wt.%) was measured even at acidic pH. This study therefore demonstrates how the fibrous configuration can be conveniently manipulated to trigger structure-induced functionalities critical to chronic wound management and monitoring.