Carbon Dot-Doped Hydrogel Sensor Array for Multiplexed Colorimetric Detection of Wound Healing

Recent advances in fluorescence and afterglow of CDs in matrices

Carbon dots (CDs) are novel nanomaterials with dimensions less than 10 nm that have attracted much attention due to their outstanding optical properties. However, the development of solid-state fluorescence and afterglow methods has been relatively slow, although the properties of these materials under liquid conditions have been extensively studied. In recent years, embedding CDs in a matrix has been shown to prevent aggregation quenching and inhibit nonradiative transitions, thus realizing solid-state fluorescence and afterglow, which has greatly broadened the research and application areas of CDs. In terms of hydrogen bonding, ionic bonding, covalent bonding and spatial confinement, the interactions between CDs and matrices can effectively realize and improve the solid-state fluorescence and afterglow effects of CDs. Recent applications of CDs in matrices in optoelectronics, information security, sensing, biotherapeutics and imaging are also summarized. Finally, we summarize the challenges and developments of CDs in matrices.

An injectable chitosan-based hydrogel incorporating carbon dots with dual enzyme-mimic activities for synergistically treatment of bacteria infected wounds

Bacterial infections pose a serious threat to human health, and the emergence of superbugs and the growing antibiotic resistance phenomenon have made the development of novel antimicrobial products. In this paper, an ultrasmall Cu, N co-doped carbon dots (CDs-Cu-N) with excellent peroxidase mimic activity and enhanced catalase mimic activity was successfully prepared and anchored to an injectable chitosan (CS)-based hybrid hydrogel. As expected, the CDs-Cu-N-H2O2-CS hybrid hydrogel maintains the excellent enzyme-mimicking properties of CDs-Cu-N and shows superior antibacterial property, which has been proven to effectively promote the healing of S. aureus-infected wounds with good biocompatibility. Benefitting from the dual-enzyme-mimic activity of CDs-Cu-N, the hybrid hydrogel not only can catalyze the generation of highly toxic ROS from low concentration of H2O2 to inhibit the bacterial infections, but also can significantly promote the wound tissue repair and regeneration by improving the anoxic microenvironment and promoting neovascularization. In addition, this hybrid hydrogel also possessed excellent injectability and moldability. It can adapt to various the irregular shapes of acute wounds, maintaining a moist and safe microenvironment while prolonging the action time of nanozyme on wounds, thus promoting wound healing. This injectable hybrid hydrogel shows great potential applications in the field of wound infection management.

Injectable Hydrogels with Integrated Ph Probes and Ultrasound-Responsive Microcapsules as Smart Wound Dressings for Visual Monitoring and On-Demand Treatment of Chronic Wounds

Hydrogel dressings capable of infection monitoring and precise treatment administration show promise for advanced wound care. Existing methods involve embedd ingorganic dyes or flexible electronics into preformed hydrogels, which raise safety issues and adaptability challenges. In this study, an injectable hydrogel based smart wound dressing is developed by integrating food-derived anthocyanidin as a visual pH probe for infection monitoring and poly(L-lactic acid) microcapsules as ultrasound-responsive delivery systems for antibiotics into a poly(ethylene glycol) hydrogel. This straightforwardly prepared hydrogel dressing maintains its favorable properties for wound repair, including porous morphology and excellent biocompatibility. In vitro experiments demonstrated that the hydrogel enabled visual assessment of pH within the range of 5 ∼ 9.Meanwhile, the release of antibiotics could be triggered and controlled by ultrasound. In vivo evaluations using infected wounds and diabetic wounds revealed that the wound dressing effectively detected wound infection by monitoring pH levels and achieved antibacterial effects through ultrasound-triggered drug release. This led to significantly enhanced wound healing, as validated by histological analysis and the measurement of inflammatory cytokine levels. This injectable hydrogel-based smart wound dressing holds great potential for use in clinical settings to inform timely and precise clinical intervention and in community to improve wound care management.

A Review of Recent Advances in Microneedle-Based Sensing within the Dermal ISF That Could Transform Medical Testing

Interstitial fluid (ISF) has attracted extensive attention in an extremely wide range of areas due to its unique advantages, such as portability, high precision, comfortable operation, and superior stability. In recent years, the microneedle (MN) technique has been considered to be an excellent tool for extracting ISF because it is painless and noninvasive. Recent reports have shown that MN has good application prospects in ISF extraction. In this review, we provide comprehensive and in-depth insight into integrated MN devices for ISF detection, covering the basic structure as well as the fabrication of integrated MN devices and various applications in ISF extraction. Challenges and prospects are highlighted, with a discussion on how to transition such MN-integrated devices toward personalized healthcare monitoring systems.

Color changing bioadhesive barrier for peripherally inserted central catheters

Bacteria migration at catheter insertion sites presents a serious complication (bacteraemia) with high mortality rates. One strategy to mediate bacteraemia is a physical barrier at the skin-catheter interface. Herein a colorimetric biosensor adhesive (CathoGlu) is designed and evaluated for both colorimetric detection of bacterial infection and application as a bacteria barrier. The design intent combines viscous, hydrophobic bioadhesive with an organic pH indicator (bromothymol blue). Visual observation can then distinguish healthy skin at pH = ∼5 from an infected catheter insertion site at pH = ∼8. The liquid-to-biorubber transition of CathoGlu formulation occurs via a brief exposure to UVA penlight, providing an elastic barrier to the skin flora. Leachates from CathoGlu demonstrate no genotoxic and skin sensitization effect, assessed by OECD-recommended in vitro and in chemico assays. The CathoGlu formulation was found non-inferior against clinically approved 2-octyl-cyanoacrylate (Dermabond™), and adhesive tape (Micropore™) within an in vivo porcine model. CathoGlu skin adhesive provides new opportunities to prevent sepsis in challenging clinical situations.

Recent advances of hydrogels as smart dressings for diabetic wounds

Chronic diabetic wounds have been an urgent clinical problem, and wound dressings play an important role in their management. Due to the design of traditional dressings, it is difficult to achieve adaptive adhesion and on-demand removal of complex diabetic wounds, real-time monitoring of wound status, and dynamic adjustment of drug release behavior according to the wound microenvironment. Smart hydrogels, as smart dressings, can respond to environmental stimuli and achieve more precise local treatment. Here, we review the latest progress of smart hydrogels in wound bandaging, dynamic monitoring, and drug delivery for treatment of diabetic wounds. It is worth noting that we have summarized the most important properties of smart hydrogels for diabetic wound healing. In addition, we discuss the unresolved challenges and future prospects in this field. We hope that this review will contribute to furthering progress on smart hydrogels as improved dressing for diabetic wound healing and practical clinical application.

A facile, low-cost bimetallic iron-nickel MOF nanozyme-propelled ratiometric fluorescent sensor for highly sensitive and selective uric acid detection and its smartphone application

As a kind of well-known disease biomarker, uric acid (UA) is closely associated with normal metabolism and health. Despite versatile nanozymes facilitating the analysis of UA, most previous works could only generate single-signal outputs with unsatisfactory detection performance. Exploring a novel ratiometric fluorescent UA sensor with high sensitivity, reliability and portable sensing ability based on facile, low-cost nanozymes is still challenging. Herein, we report the first metal-organic-framework (MOF) nanozyme-originated ratiometric fluorescent UA sensor based on Fe3Ni-MOF-NH2 propelled UA/uricase/o-phenylenediamine tandem catalytic reaction. Different from previous reports, the peroxidase-like property and fluorescence of Fe3Ni-MOF-NH2 were simultaneously employed. In the absence of UA, only the MOF's fluorescence at 430 nm (FI430) can be observed, while the addition of UA will initiate UA/uricase catalytic reaction, and the generated H2O2 could oxidize o-phenylenediamine into highly fluorescent 2,3-diaminophenazine (DAP) (emission at 565 nm, FI565) under the catalysis of the MOF nanozyme. Coincidently, MOF's fluorescence can be quenched by DAP via the inner filter effect, resulting in a low FI430 value and high FI565 value, respectively. Therefore, H2O2 and UA can be alternatively detected through monitoring the above contrary fluorescence changes. The limit of detection for UA is 24 nM, which is much lower than those in most previous works, and the lowest among nanozyme-based ratiometric fluorescent UA sensors reported to date. Moreover, the portable sensing of UA via smartphone-based RGB analysis was facilely achieved by virtue of the above nanozyme-propelled tandem catalytic system, and MOF nanozyme-based molecular contrary logic pairs were further implemented accordingly.

Nanophotonic and hydrogel-based diagnostic system for the monitoring of chronic wounds

Chronic wounds present a major healthcare burden, yet most wounds are only assessed superficially, and treatment is rarely based on the analysis of wound biomarkers. This lack of analysis is based on the fact that sampling of wound biomarkers is typically invasive, leading to a disruption of the wound bed while biomarker detection and quantification is performed in a remote laboratory, away from the point of care. Here, we introduce the diagnostic element of a novel theranostic system that can non-invasively sample biomarkers without disrupting the wound and that can perform biomarker quantification at the point of care, on a short timescale. The system is based on a thermally switchable hydrogel scaffold that enhances wound healing through regeneration of the wound tissue and allows the extraction of wound biomarkers non-destructively. We demonstrate the detection of two major biomarkers of wound health, i.e., IL-6 and TNF-α, in human matrix absorbed into the hydrogel dressing. Quantification of the biomarkers directly in the hydrogel is achieved using a chirped guided mode resonant biosensor and we demonstrate biomarker detection within the clinically relevant range of pg/mL to μg/mL concentrations. We also demonstrate the detection of IL-6 and TNF-α at concentration 1 ng/mL in hydrogel dressing absorbed with clinical wound exudate samples. The high sensitivity and the wide dynamic range we demonstrate are both essential for the clinical relevance of our system. Our test makes a major contribution towards the development of a wound theranostic for guided treatment and management of chronic wounds.

Keratin- and VEGF-Incorporated Honey-Based Sponge-Nanofiber Dressing: An Ideal Construct for Wound Healing

To overcome the drawbacks of single-layered wound dressings, bilayer dressings are now introduced as an alternative to achieve effective and long-term treatment. Here, a bilayer dressing composed of electrospun nanofibers in the bottom layer (BL) and a sponge structure as the top layer (TL) is presented. Hydrophilic poly(acrylic acid) (PAAc)-honey (Hny) with interconnected pores of 76.04 μm was prepared as the TL and keratin (Kr), Hny, and vascular endothelial growth factor (VEGF) were prepared as the BL. VEGF indicates a gradual release over 7 days, promoting angiogenesis, as proven by the chick chorioallantoic membrane assay and in vivo tissue histomorphology observation. Additionally, the fabricated dressing material indicated a satisfactory tensile profile, cytocompatibility for human keratinocyte cells, and the ability to promote cell attachment and migration. The in vivo animal model demonstrated that the full-thickness wound healed faster when it was covered with PAAc-Hny/Hny-Kr-VEGF than in other groups. Additionally, faster blood vessel formation, collagen synthetization, and epidermal layer generation were also confirmed, which have proven efficient healing acceleration in wounds treated with synthesized bilayer dressings. Our findings indicated that the fabricated material can be promising as a functional wound dressing.

Establishing a Corrugated Carbon Network with a Crack Structure in a Hydrogel for Improving Sensing Performance

Electronic conductive hydrogels have prompted immense research interest as flexible sensing materials. However, establishing a continuous electronic conductive network within a hydrogel is still highly challenging. Herein, we develop a new strategy to establish a continuous corrugated carbon network within a hydrogel by embedding carbonized crepe paper into the hydrogel with its corrugations perpendicular to the stretching direction using a casting technique. The corrugated carbon network within the as-prepared composite hydrogel serves as a rigid conductive network to simultaneously improve the tensile strength and conductivity of the composite hydrogel. The composite hydrogel also generates a crack structure when it is stretched, enabling the composite hydrogel to show ultrahigh sensitivity (gauge factor = 59.7 and 114 at strain ranges of 0-60 and 60-100%, respectively). The composite hydrogel also shows an ultralow detection limit of 0.1%, an ultrafast response/recovery time of 75/95 ms, and good stability and durability (5000 cycles at 10% strain) when used as a resistive strain sensing material. Moreover, the good stretchability, adhesiveness, and self-healing ability of the hydrogel were also effectively retained after the corrugated carbon network was introduced into the hydrogel. Because of its outstanding sensing performance, the composite hydrogel has potential applications in sensing various human activities, including accurately recording subtle variations in wrist pulse waves and small-/large-scale complex human activities. Our work provides a new approach to develop economical, environmentally friendly, and reliable electronic conductive hydrogels with ultrahigh sensing performance for the future development of electronic skin and wearable devices.

The construction of Fe-porphyrin nanozymes with peroxidase-like activity for colorimetric detection of glucose

As a type of nanomaterials with enzyme-mimetic catalytic properties, nanozymes have attracted wide concern in biological detection. H₂O₂ was the characteristic product of diverse biological reactions, and the quantitative analysis for H₂O₂ was an important way to detect disease biomarkers, such as acetylcholine, cholesterol, uric acid and glucose. Therefore, there is of great significance for developing a simple and sensitive nanozyme to detect H₂O₂ and disease biomarkers by combining with corresponding enzyme. In this work, Fe-TCPP MOFs were successfully prepared by the coordination between iron ions and porphyrin ligands (TCPP). In addition, the peroxidase (POD) activity of Fe-TCPP was proved, in detail, Fe-TCPP could catalyze H₂O₂ to produce ·OH by Fenton reaction. Herein, glucose oxidase (GOx) was chosen as the model to build cascade reaction by combining Fe-TCPP to detect glucose. The results indicated glucose could be detected by this cascade system selectively and sensitively, and the limit of detection of glucose was achieved to 0.12 μM. Furthermore, a portable hydrogel (Fe-TCPP@GEL) was further established, which encapsulated Fe-TCPP MOFs, GOx and TMB in one system. This functional hydrogel could be applied for colorimetric detection of glucose by coupling with a smartphone easily.