Temperature-adaptive hydrogel optical waveguide with soft tissue-affinity for thermal regulated interventional photomedicine

Biopolymer based Fibrous Aggregate Materials for Diagnosis and Treatment: Design, Manufacturing, and Applications

Biopolymer-based fibrous aggregate materials (BFAMs) have gained increasing attention in biomedicine due to their excellent biocompatibility, processability, biodegradability, and multifunctionality. Especially, the medical applications of BFAMs demand advanced structure, performance, and function, which conventional trial-and-error methods struggle to provide. This necessitates the rational selection of materials and manufacturing methods to design BFAMs with various intended functions and structures. This review summarizes the current progress in raw material selection, structural and functional design, processing technology, and application of BFAMs. Additionally, the challenges encountered during the development of BFAMs are discussed, along with perspectives for future research offered.

Advances in Photonic Materials and Integrated Devices for Smart and Digital Healthcare: Bridging the Gap Between Materials and Systems

Recent advances in developing photonic technologies using various materials offer enhanced biosensing, therapeutic intervention, and non-invasive imaging in healthcare. Here, this article summarizes significant technological advancements in materials, photonic devices, and bio-interfaced systems, which demonstrate successful applications for impacting human healthcare via improved therapies, advanced diagnostics, and on-skin health monitoring. The details of required materials, necessary properties, and device configurations are described for next-generation healthcare systems, followed by an explanation of the working principles of light-based therapeutics and diagnostics. Next, this paper shares the recent examples of integrated photonic systems focusing on translation and immediate applications for clinical studies. In addition, the limitations of existing materials and devices and future directions for smart photonic systems are discussed. Collectively, this review article summarizes the recent focus and trends of technological advancements in developing new nanomaterials, light delivery methods, system designs, mechanical structures, material functionalization, and integrated photonic systems to advance human healthcare and digital healthcare.

Effective Antitumor Synergistic Treatment with Fiber-Photothermal Therapy and Heat Shock Protein Inhibitors

Effective treatment of malignant tumors remains a thorny issue in current medicine. As a new type of anticancer strategy, photothermal therapy (PTT) has attracted tremendous attention due to its favorable therapeutic effectiveness, high spatial-temporal controllability, and low occurrence of side effects. However, the efficacy of PTT is significantly reduced due to the limited penetration of light and heat-induced overexpression of heat shock protein (Hsp). Herein, we propose an antitumor synergistic therapy that combines fiber-optic PTT and Hsp inhibitors. A rare-earth-doped optical fiber was used as the PTT actuator, and the Hsp inhibitor AT533 was loaded on the fiber surface by use of a hydrogel layer. PTT fibers can be guided to reach tumor lesions directly without being subject to the light penetration limit. The Hsp inhibitor can be released upon the softening of the hydrogel layer under photoheating to deactivate Hsp in the tumor and thus reduce the resistance of the tumor to PTT. This synergistic treatment enhanced the effect of PTT and successfully eradicated tumors in colorectal cancer (CRC) xenograft mouse models, providing a feasible way to realize antitumor and antirecurrence treatment. More importantly, the success of the synergistic treatment of PTT and Hsp inhibition opens new avenues for the development of multimodal and multitype synergistic fiber-optic treatments, which offer pronounced enhancement of therapeutic effectiveness for treating cancer.

Nerve-Inspired Optical Waveguide Stretchable Sensor Fusing Wireless Transmission and AI Enabling Smart Tele-Healthcare

Flexible strain monitoring of hand and joint muscle movement is recognized as an effective method for the diagnosis and rehabilitation of neurological diseases such as stroke and Parkinson's disease. However, balancing high sensitivity and large strain, improving wearing comfort, and solving the separation of diagnosis and treatment are important challenges for further building tele-healthcare systems. Herein, a hydrogel-based optical waveguide stretchable (HOWS) sensor is proposed in this paper. A double network structure is adopted to allow the HOWS sensor to exhibit high stretchability of the tensile strain up to 600% and sensitivity of 0.685 mV %-1. Additionally, the flexible smart bionic fabric embedding the HOWS sensor, produced through the warp and weft knitting, significantly enhances wearing comfort. A small circuit board is prepared to enable wireless signal transmission of the designed sensor, thereby improving the daily portability. A speech recognition and human-machine interaction system, based on sensor signal acquisition, is constructed, and the convolutional neural network algorithm is integrated for disease assessment. By integrating sensing, wireless transmission, and artificial intelligence (AI), a smart tele-healthcare system based on HOWS sensors is demonstrated to hold great potential for early warning and rehabilitation monitoring of neurological diseases.

Hydrogel Fibers-Based Biointerfacing

The unique 1D structure of fibers offers intriguing attributes, including a high length-to-diameter ratio, miniatured size, light-weight, and flexibility, making them suitable for various biomedical applications, such as health monitoring, disease treatment, and minimally invasive surgeries. However, traditional fiber devices, typically composed of rigid, dry, and non-living materials, are intrinsically different from the soft, wet, and living essence of biological tissues, thereby posing grand challenges for long-term, reliable, and seamless interfacing with biological systems. Hydrogel fibers have recently emerged as a promising candidate, in light of their similarity to biological tissues in mechanical, chemical and biological aspects, as well as distinct fiber geometry. In this review, a comprehensive overview of recent progress in hydrogel fibers-based biointerfacing technology is provided. It thoroughly summarizes the manufacturing strategy and functional design, especially for hydrogel fibers with distinct optical and electron conductive performance, as well as responsiveness to triggers including thermal, magnetic field and ultrasonic wave, etc. Such unique attributes enable various biomedical applications, which are also examined in detail. Future challenges and potential directions, including biosafety, long-term reliability, sterilization, multi-modalities integration and intelligent therapeutic systems, are raised. This review will serve as a valuable resource for further advancement and implementation as next-generation biointerfacing technology.

Fully Automated and AI-Assisted Optical Fiber Sensing System for Multiplexed and Continuous Brain Monitoring

Continuous and comprehensive brain monitoring is crucial for timely identification of changes or deterioration in brain function, enabling prompt intervention and personalized treatments. However, existing brain monitoring systems struggle to offer continuous and accurate monitoring of multiple brain biomarkers simultaneously. This study introduces a multiplexed optical fiber sensing system for continuous and simultaneous monitoring of six cerebrospinal fluid (CSF) biomarkers using tip-functionalized optical fibers and computational algorithms. Optimized machine learning models are developed and integrated for real-time spectra analysis, allowing for precise and continuous readout of biomarker concentrations. The developed machine learning-assisted fiber optic sensing system exhibits high sensitivity (0.04, 0.38, 0.67, 2.62, 0.0064, 0.33 I/I0 change per units of temperature, dissolved oxygen, glucose, pH, Na+, Ca2+, respectively), reversibility, and selectivity toward target biomarkers with a total diameter less than 2.5 mm. By monitoring brain metabolic and ionic dynamics, this system accurately identified brain physiology deterioration and recovery using ex vivo traumatic brain injury models. Additionally, the system successfully tracked biomarker fluctuations in clinical CSF samples with high accuracy (R2 > 0.93), demonstrating excellent sensitivity and selectivity in reflecting disease progression in real time. These findings underscore the enormous potential of automated and multiplexed optical fiber sensing systems for intraoperative and postoperative monitoring of brain physiologies.

Sandwich Layer-Modified Ω-Shaped Fiber-Optic LSPR Enables the Development of an Aptasensor for a Cytosensing-Photothermal Therapy Circuit

The metastasis of cancer cells is a principal cause of morbidity and mortality in cancer. The combination of a cytosensor and photothermal therapy (PTT) cannot completely eliminate cancer cells at one time. Hence, this study aimed to design a localized surface plasmonic resonance (LSPR)-based aptasensor for a circuit of cytosensing-PTT (COCP). This was achieved by coating a novel sandwich layer of polydopamine/gold nanoparticles/polydopamine (PDA/AuNPs/PDA) around the Ω-shaped fiber-optic (Ω-FO). The short-wavelength peak of the sandwich layer with strong resonance exhibited a high refractive index sensitivity (RIS). The modification with the T-shaped aptamer endowed FO-LSPR with unique characteristics of time-dependent sensitivity enhancement behavior for a sensitive cytosensor with the lowest limit of detection (LOD) of 13 cells/mL. The long-wavelength resonance peak in the sandwich layer appears in the near-infrared region. Hence, the rate of increased localized temperature of FO-LSPR was 160 and 30-fold higher than that of the bare and PDA-coated FO, indicating strong photothermal conversion efficiency. After considering the localized temperature distribution around the FO under the flow environment, the FO-LSPR-enabled aptasensor killed 77.6% of cancer cells in simulated blood circulation after five cycles of COCP. The FO-LSPR-enabled aptasensor improved the efficiency of the cytosensor and PTT to effectively kill cancer cells, showing significant potential for application in inhibiting cancer metastasis.

Mechanical Regulation of Polymer Gels

The mechanical properties of polymer gels devote to emerging devices and machines in fields such as biomedical engineering, flexible bioelectronics, biomimetic actuators, and energy harvesters. Coupling network architectures and interactions has been explored to regulate supportive mechanical characteristics of polymer gels; however, systematic reviews correlating mechanics to interaction forces at the molecular and structural levels remain absent in the field. This review highlights the molecular engineering and structural engineering of polymer gel mechanics and a comprehensive mechanistic understanding of mechanical regulation. Molecular engineering alters molecular architecture and manipulates functional groups/moieties at the molecular level, introducing various interactions and permanent or reversible dynamic bonds as the dissipative energy. Molecular engineering usually uses monomers, cross-linkers, chains, and other additives. Structural engineering utilizes casting methods, solvent phase regulation, mechanochemistry, macromolecule chemical reactions, and biomanufacturing technology to construct and tailor the topological network structures, or heterogeneous modulus compositions. We envision that the perfect combination of molecular and structural engineering may provide a fresh view to extend exciting new perspectives of this burgeoning field. This review also summarizes recent representative applications of polymer gels with excellent mechanical properties. Conclusions and perspectives are also provided from five aspects of concise summary, mechanical mechanism, biofabrication methods, upgraded applications, and synergistic methodology.

Hydrogel for light delivery in biomedical applications

Traditional optical waveguides or mediums are often silica-based materials, but their applications in biomedicine and healthcare are limited due to the poor biocompatibility and unsuitable mechanical properties. In term of the applications in human body, a biocompatible hydrogel system with excellent optical transparency and mechanical flexibility could be beneficial. In this review, we explore the different designs of hydrogel-based optical waveguides derived from natural and synthetic sources. We highlighted key developments such as light emitting contact lenses, implantable optical fibres, biosensing systems, luminating and fluorescent materials. Finally, we expand further on the challenges and perspectives for hydrogel waveguides to achieve clinical applications.

Dual-Function Wearable Hydrogel Optical Fiber for Monitoring Posture and Sweat pH

In recent years, wearable devices have been widely used for human health monitoring. Such monitoring predominantly relies on the principles of optics and electronics. However, electronic detection is susceptible to electromagnetic interference, and traditional optical fiber detection is limited in functionality and unable to simultaneously detect both physical and chemical signals. Hence, a wearable, embedded asymmetric color-blocked optical fiber sensor based on a hydrogel has been developed. Its sensing principle is grounded in the total internal reflection within the optical fiber. The method for posture sensing involves changes in the light path due to fiber bending with color blocks providing wavelength-selective modulation by absorption changes. Sweat pH sensing is facilitated by variations in fluorescence intensity triggered by sweat-induced conformational changes in Rhodamine B. With just one fiber, it achieves both physical and chemical signal detection. Fabricated using a molding technique, this fiber boasts excellent biocompatibility and can accurately discern single and multiple bending points, with a recognition range of 0-90° for a single segment, a detection limit of 0.02 mm-1 and a sweat pH sensing linear regression R2 of 0.993, alongside great light propagation properties (-0.6 dB·cm-1). With its extensive capabilities, it holds promise for applications in medical monitoring.

A Skin-Inspired Self-Adaptive System for Temperature Control During Dynamic Wound Healing

The thermoregulating function of skin that is capable of maintaining body temperature within a thermostatic state is critical. However, patients suffering from skin damage are struggling with the surrounding scene and situational awareness. Here, we report an interactive self-regulation electronic system by mimicking the human thermos-reception system. The skin-inspired self-adaptive system is composed of two highly sensitive thermistors (thermal-response composite materials), and a low-power temperature control unit (Laser-induced graphene array). The biomimetic skin can realize self-adjusting in the range of 35-42 °C, which is around physiological temperature. This thermoregulation system also contributed to skin barrier formation and wound healing. Across wound models, the treatment group healed ~ 10% more rapidly compared with the control group, and showed reduced inflammation, thus enhancing skin tissue regeneration. The skin-inspired self-adaptive system holds substantial promise for next-generation robotic and medical devices.

Oxidized sodium alginate/polyacrylamide hydrogels adhesive for promoting wheat growth

Chemical modification of sodium alginate (SA) polymer chains can increase its functional group species. Sodium periodate (SP) was usually used to oxidize the hydroxyl groups on the chain of SA to aldehyde groups, the preparation of oxidized sodium alginate (OSA) using SP is not only complicated, also limits the variety of functional groups on the chain of OSA. By contrast, we have developed an innovative strategy for OSA, in which ammonium persulfate (APS) was used to oxidize SA, providing a clear elucidation of the oxidizing process and mechanism. OSA/PAM hydrogels were synthesized using OSA, the hydrogels possess excellent adhesion properties to various non-metallic and metallic substrates. Tensile and compression tests show that the cross-linked OSA/PAM hydrogels have superior mechanical properties. We exploit OSA/PAM hydrogels as soil adhesive and water-retaining agents for wheat growth. OSA/PAM hydrogels significantly improve the survival time of wheat grown in brown loam soil under a water-shortage environment, and slow down the wilting of wheat in a water-shortage environment and prolong the survival time of wheat in sandy soils. Our trials should make hydrogels important for wheat cultivation in brown loam soils and the development of desert areas.

Bioadhesive Technology Platforms

Bioadhesives have emerged as transformative and versatile tools in healthcare, offering the ability to attach tissues with ease and minimal damage. These materials present numerous opportunities for tissue repair and biomedical device integration, creating a broad landscape of applications that have captivated clinical and scientific interest alike. However, fully unlocking their potential requires multifaceted design strategies involving optimal adhesion, suitable biological interactions, and efficient signal communication. In this Review, we delve into these pivotal aspects of bioadhesive design, highlight the latest advances in their biomedical applications, and identify potential opportunities that lie ahead for bioadhesives as multifunctional technology platforms.

Recent Insights about the Role of Gels in Organic Photonics and Electronics

This review article provides an in-depth exploration of the role of gels in the fields of organic electronics and photonics, focusing on their unique properties and applications. Despite their remarkable potential, gel-based innovations remain relatively uncharted in these domains. This brief review aims to bridge the knowledge gap by shedding light on the diverse roles that gels can fulfil in the enhancement of organic electronic and photonic devices. From flexible electronics to light-emitting materials, we delve into specific examples of gel applications, highlighting their versatility and promising outcomes. This work serves as an indispensable resource for researchers interested in harnessing the transformative power of gels within these cutting-edge fields. The objective of this review is to raise awareness about the overlooked research potential of gels in optoelectronic materials, which have somewhat diminished in recent years.

Influence of the Degree of Swelling on the Stiffness and Toughness of Microgel-Reinforced Hydrogels

The stiffness and toughness of conventional hydrogels decrease with increasing degree of swelling. This behavior makes the stiffness-toughness compromise inherent to hydrogels even more limiting for fully swollen ones, especially for load-bearing applications. The stiffness-toughness compromise of hydrogels can be addressed by reinforcing them with hydrogel microparticles, microgels, which introduce the double network (DN) toughening effect into hydrogels. However, to what extent this toughening effect is maintained in fully swollen microgel-reinforced hydrogels (MRHs) is unknown. Herein, it is demonstrated that the initial volume fraction of microgels contained in MRHs determines their connectivity, which is closely yet nonlinearly related to the stiffness of fully swollen MRHs. Remarkably, if MRHs are reinforced with a high volume fraction of microgels, they stiffen upon swelling. By contrast, the fracture toughness linearly increases with the effective volume fraction of microgels present in the MRHs regardless of their degree of swelling. These findings provide a universal design rule for the fabrication of tough granular hydrogels that stiffen upon swelling and hence, open up new fields of use of these hydrogels.

Intrinsic Anti-Freezing and Unique Phosphorescence of Glassy Hydrogels with Ultrahigh Stiffness and Toughness at Low Temperatures

Most hydrogels become frozen at subzero temperatures, leading to degraded properties and limited applications. Cryoprotectants are massively employed to improve anti-freezing property of hydrogels; however, there are accompanied disadvantages, such as varied networks, reduced mechanical properties, and the risk of cryoprotectant leakage in aqueous conditions. Reported here is the glassy hydrogel having intrinsic anti-freezing capacity and excellent optical and mechanical properties at ultra-low temperatures. Supramolecular hydrogel of poly(acrylamide-co-methacrylic acid) with moderate water content (≈50 wt.%) and dense hydrogen-bond associations is in a glassy state at room temperature. Since hydrogen bonds become strengthened as the temperature decreases, this gel becomes stronger and stiffer, yet still ductile, with Young's modulus of 900 MPa, tensile strength of 30 MPa, and breaking strain of 35% at -45 °C. This gel retains high transparency even in liquid nitrogen. It also exhibits unique phosphorescence due to presence of carbonyl clusters, which is further enhanced at subzero temperatures. Further investigations elucidate that the intrinsic anti-freezing property is related to a fact that most water molecules are tightly bound and confined in the glassy matrix and become non-freezable. This correlation, as validated in several systems, provides a roadmap to develop intrinsic anti-freezing hydrogels for widespread applications at extreme conditions.