Author Correction: Hydrogel mechanical properties in altered gravity
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Ag@polydopamine-functionalized borate ester-linked chitosan hydrogel integrates monitoring with wound healing for epidermal sensor
Flexible sensors are promising candidates in personalized healthcare, while desired sensors that allow implantation for biomedical applications with optimal sensing and favorable biological properties remain challenges. Here, a multifunctional hydrogel sensor was developed with gallic acid-modified chitosan (CSGA) and 3-carboxyphenylboronic acid-modified chitosan (CSPBA) by encapsulating Ag-decorated polydopamine (Ag@PDA) nanoparticles, namely Ag@PDA-(CSPBA/CSGA). The optimized hydrogel sensor showed desired sensitivity (gauge factor = 2.49), a rapid response/recovery time of 263 ms and good durability. Due to the presence of abundant reactive groups within Ag@PDA-(CSPBA/CSGA), the hydrogel sensor exhibited a comprehensive performance of self-healing, tissue adhesiveness, antioxidative activity, and antibacterial effects against Escherichia coli (92.76%) and Staphylococcus aureus (98.08%). Moreover, the hydrogel sensor could be utilized as a wound dressing, facilitating accelerated wound closure and tissue regeneration. Both subtle activities and large-scale movements could be monitored and distinguished by the hydrogel sensor. This study provides a promising epidermal sensor that offers multifunctionality for health monitoring and wound management.
Mussel-inspired thermo-switchable underwater adhesive based on a Janus hydrogel
On-demand underwater adhesives with excellent adhesive and gentle detachment properties enable stable connections to various biomedical devices and biointerfaces and avoid the risk of harmful tissue damage upon detachment. Herein, we present a Janus hydrogel adhesive that can reversibly switch its adhesion strength, which is controlled by temperature, using a thermoresponsive polymer and mussel-inspired molecules. This thermoswitchable adhesive (TSA) hydrogel displays both strong adhesion and gentle detachment with an over 1000-fold gap in underwater adhesion strength onto glass, titanium, aluminum, and Teflon substrates when exposed to temperatures above and below the lower critical solution temperature (LCST). The adhesion switch is possibly caused by the change in toughness of the TSA hydrogels with temperature because the Janus hydrogel possesses gradient crosslinked structures. Moreover, the lowermost surface is sufficiently soft to gently detach from the substrate below the LCST. The electrode-integrated hydrogel remains on human skin, and electrical signals are continuous over 10 min above the LCST. In contrast, commercially available hydrogel electrodes quickly swell and detach from the skin. The thermoswitchability of the TSA hydrogel, with its robust adhesion and gentle detachment, offers significant potential for biomedical applications characterized by minimally invasive procedures.
Photothermal sensitive nanocomposite hydrogel for infectious bone defects
Infectious bone defects represent a substantial challenge in clinical practice, necessitating the deployment of advanced therapeutic strategies. This study presents a treatment modality that merges a mild photothermal therapy hydrogel with a pulsed drug delivery mechanism. The system is predicated on a hydrogel matrix that is thermally responsive, characteristic of bone defect sites, facilitating controlled and site-specific drug release. The cornerstone of this system is the incorporation of mild photothermal nanoparticles, which are activated within the temperature range of 40–43 °C, thereby enhancing the precision and efficacy of drug delivery. Our findings demonstrate that the photothermal response significantly augments the localized delivery of therapeutic agents, mitigating systemic side effects and bolstering efficacy at the defect site. The synchronized pulsed release, cooperated with mild photothermal therapy, effectively addresses infection control, and promotes bone regeneration. This approach signifies a considerable advancement in the management of infectious bone defects, offering an effective and patient-centric alternative to traditional methods. Our research endeavors to extend its applicability to a wider spectrum of tissue regeneration scenarios, underscoring its transformative potential in the realm of regenerative medicine.
Universal in situ supersaturated crystallization enables 3D printable afterglow hydrogel
Stretchable afterglow materials have garnered widespread attention owing to their unique combination of optical properties and mechanical flexibility. However, achieving a crystal environment to suppress the non-radiative transition of triplet excitons poses a challenge in constructing stretchable afterglow materials. Herein, we utilize an in situ supersaturated crystallization strategy to form afterglow microcrystals within a hydrogel matrix. This approach enables afterglow emission with a lifetime of 695 ms while maintaining high stretchability with tensile stress surpassing 398 kPa, extensibility over 400% and a high water content of 65.21%. Moreover, the universal supersaturated crystallization strategy allows for conferring tunable afterglow performance. Successful demonstrations in hydrogel 3D printing and anti-counterfeiting purposes showcase the potential for advanced applications of 3D printable afterglow hydrogels. This investigation provides guidelines for generally designing efficient afterglow hydrogels and addresses the inherent contradiction between flexibility and rigid in stretchable afterglow materials.
Stiff and self-healing hydrogels by polymer entanglements in co-planar nanoconfinement
Many biological tissues are mechanically strong and stiff but can still heal from damage. By contrast, synthetic hydrogels have not shown comparable combinations of properties, as current stiffening approaches inevitably suppress the required chain/bond dynamics for self-healing. Here we show a stiff and self-healing hydrogel with a modulus of 50 MPa and tensile strength up to 4.2 MPa by polymer entanglements in co-planar nanoconfinement. This is realized by polymerizing a highly concentrated monomer solution within a scaffold of fully delaminated synthetic hectorite nanosheets, shear oriented into a macroscopic monodomain. The resultant physical gels show self-healing efficiency up to 100% despite the high modulus, and high adhesion shear strength on a broad range of substrates. This nanoconfinement approach allows the incorporation of novel functionalities by embedding colloidal materials such as MXenes and can be generalized to other polymers and solvents to fabricate stiff and self-healing gels for soft robotics, additive manufacturing and biomedical applications.
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