Recent Advances of DNA Hydrogels in Biomedical Applications

Recent Advances in Hydrogel-Based Biosensors for Cancer Detection

Early cancer detection is crucial for effective treatment, but current methods have limitations. Novel biomaterials, such as hydrogels, offer promising alternatives for developing biosensors for cancer detection. Hydrogels are three-dimensional and cross-linked networks of hydrophilic polymers that have properties similar to biological tissues. They can be combined with various biosensors to achieve high sensitivity, specificity, and stability. This review summarizes the recent advances in hydrogel-based biosensors for cancer detection, their synthesis, their applications, and their challenges. It also discusses the implications and future directions of this emerging field.

Hydrogel-Based Biosensors for Effective Therapeutics

Nanotechnology and polymer engineering are navigating toward new developments to control and overcome complex problems. In the last few decades, polymer engineering has received researchers' attention and similarly, polymeric network-engineered structures have been vastly studied. Prior to therapeutic application, early and rapid detection analyses are critical. Therefore, developing hydrogel-based sensors to manage the acute expression of diseases and malignancies to devise therapeutic approaches demands advanced nanoengineering. However, nano-therapeutics have emerged as an alternative approach to tackling strenuous diseases. Similarly, sensing applications for multiple kinds of analytes in water-based environments and other media are gaining wide interest. It has also been observed that these functional roles can be used as alternative approaches to the detection of a wide range of biomolecules and pathogenic proteins. Moreover, hydrogels have emerged as a three-dimensional (3D) polymeric network that consists of hydrophilic natural or synthetic polymers with multidimensional dynamics. The resemblance of hydrogels to tissue structure makes them more unique to study inquisitively. Preceding studies have shown a vast spectrum of synthetic and natural polymer applications in the field of biotechnology and molecular diagnostics. This review explores recent studies on synthetic and natural polymers engineered hydrogel-based biosensors and their applications in multipurpose diagnostics and therapeutics. We review the latest studies on hydrogel-engineered biosensors, exclusively DNA-based and DNA hydrogel-fabricated biosensors.

Highly biocompatible Ag nanocluster-reinforced wound dressing with long-term and synergistic bactericidal activity

Clinical application of antibiotic-free agents like silver nanoparticle-derived materials remains a critical challenge due to their limited long-term antibacterial activity and potential system toxicity. Herein, a highly biocompatible Ag nanocluster-reinforced hydrogel with enhanced synergistic antibacterial ability has been developed. Specifically, bioactive curcumin was incorporated into lysozyme-protected ultrasmall Ag nanoclusters (LC-AgNCs) and further integrated with sodium alginate (Sa) hydrogel (LC-AgNCs@Sa) through multiple interaction forces. Due to the synergistic antibacterial activity, LC-AgNCs could effectively kill both S. aureus and E. coli bacteria with a concentration down to 2.5 μg mL^-1. In-depth mechanism investigations revealed that the bactericidal effect of LC-AgNCs lies in their bacterial membrane destruction, reactive oxygen species (ROS) production, glutathione depletion and prooxidant-antioxidant system disruption ability. Curcumin can mediate the intracellular ROS balance to protect NIH 3T3 cells from oxidative stress and improve the biocompatibility of LC-AgNCs@Sa. LC-AgNCs@Sa with long-term antibacterial ability can effectively protect the wound from bacterial invasion in vivo, and significantly accelerate the wound healing process due to their distinctive functions of inhibiting inflammatory factor (TNF-α) production, promoting collagen deposit and facilitating re-epithelization. This study provides a new, versatile strategy for the design of high-performance antibacterial dressing for broad infectious disease therapy.

Stimuli-Responsive Self-Degradable DNA Hydrogels: Design, Synthesis, and Applications

DNA hydrogels play an increasingly important role in biomedicine and bioanalysis applications. Due to their high programmability, multifunctionality and biocompatibility, they are often used as effective carriers for packing drugs, cells, or other bioactive cargoes in vitro and in vivo. However, the stability of the DNA hydrogels prevents their in-demand rapid release of cargoes to achieve a full therapeutic effect in time. For bioanalysis, the generation of signals sometimes needs the DNA hydrogel to be rapidly degraded when sensing target molecules. To meet these requirements, stimulus-responsive DNA hydrogels are designed. By responding to different stimuli, self-degradable DNA hydrogels can switch from gel to solution for quantitative bioanalysis and precision cargo delivery. This review summarizes the recently developed innovative methods for designing stimuli-responsive self-degradable DNA hydrogels and showed their applications in the bioanalysis and biomedicines fields. Challenges, as well as prospects, are also discussed.

Biodegradable and Antioxidant DNA Hydrogel as a Cytokine Delivery System for Diabetic Wound Healing

Impaired diabetic wound healing is associated with the persistence of chronic inflammation and excessive oxidative stress, which has become one of the most serious clinical challenges. Wound dressings with anti-inflammatory and reactive oxygen species (ROS)-scavenging properties are desirable for diabetic wound treatment. In this study, a shape-adaptable, biodegradable, biocompatible, antioxidant, and immunomodulatory interleukin-33 (IL-33)-cytogel is developed by encapsulating IL-33 into physically cross-linked DNA hydrogels and used as wound dressings to promote diabetic wound healing. The porous microstructures and biodegradable properties of the IL-33-cytogel ensure the local sustained-release of IL-33 in the wound area, where the sustained-release of IL-33 is maintained for at least 7 days. IL-33-cytogel can induce local accumulation of group 2 innate lymphoid cells (ILC2s) and regulatory T cells (Tregs), as well as M1-to-M2 transition at the wound sites. Additionally, the antioxidant and biocompatible characteristics of DNA hydrogels promote the scavenging of intracellular ROS without affecting cell viability. As a result, local inflammation in the diabetic wound area is resolved upon IL-33-cytogel treatment, which is accompanied by improved granulation tissue regeneration and accelerated wound closure. This study demonstrates a promising strategy in tissue engineering and regenerative medicine by incorporating DNA hydrogels and cytokine immunotherapy for promoting diabetic wound healing.

Cancer cell membrane-coated C-TiO2 hollow nanoshells for combined sonodynamic and hypoxia-activated chemotherapy

Sonodynamic therapy (SDT) is a promising strategy for tumor treatment that satisfies all requirements of penetrating deep-seated tissues without causing additional trauma. However, the hypoxic tumor microenvironment impairs the therapeutic effect of SDT. The synergistic treatment of oxygen concentration-dependent SDT and bio-reductive therapy has been proven to be an effective approach to improve the therapeutic efficiency of SDT by exploiting tumor hypoxia. Herein, a biomimetic drug delivery system (C-TiO₂/TPZ@CM) was successfully synthesized for combined SDT and hypoxia-activated chemotherapy, which was composed of tirapazamine (TPZ)-loaded C-TiO₂ hollow nanoshells (HNSs) as the inner cores and cancer cell membrane (CM) as the outer shells. C-TiO₂ HNSs coated with CM achieved tumor targeting via homologous binding. C-TiO₂@CM as a nanocarrier loaded with TPZ in the presence of the trapping ability of CM and the special cavity structure of C-TiO₂ HNSs. Moreover, C-TiO₂ HNSs as sonosensitizers killed cancer cells under ultrasound (US) irradiation. Oxygen depletion during SDT induced a hypoxic environment in the tumor to activate the killing effect of co-delivered TPZ, thereby obtaining satisfactory synergistic therapeutic effects. In addition, C-TiO₂@CM exhibited remarkable biocompatibility without manifest damage and toxicity to the blood and major organs of the mice. The study highlighted that C-TiO₂/TPZ@CM served as a powerful biomimetic drug delivery system for effective SDT by exploiting tumor hypoxia. STATEMENT OF SIGNIFICANCE: • C-TiO₂@CM achieved tumor targeting via homologous binding. • C-TiO₂ hollow nanoshells could be used as a sonosensitizer and drug carrier for synergistic SDT and hypoxia-activated chemotherapy. • C-TiO₂/TPZ@CM showed no obvious toxicity under the injection dose.

Hydrogel Nanoarchitectonics: An Evolving Paradigm for Ultrasensitive Biosensing

The integration of nanoarchitectonics and hydrogel into conventional biosensing platforms offers the opportunities to design physically and chemically controlled and optimized soft structures with superior biocompatibility, better immobilization of biomolecules, and specific and sensitive biosensor design. The physical and chemical properties of 3D hydrogel structures can be modified by integrating with nanostructures. Such modifications can enhance their responsiveness to mechanical, optical, thermal, magnetic, and electric stimuli, which in turn can enhance the practicality of biosensors in clinical settings. This review describes the synthesis and kinetics of gel networks and exploitation of nanostructure-integrated hydrogels in biosensing. With an emphasis on different integration strategies of hydrogel with nanostructures, this review highlights the importance of hydrogel nanostructures as one of the most favorable candidates for developing ultrasensitive biosensors. Moreover, hydrogel nanoarchitectonics are also portrayed as a promising candidate for fabricating next-generation robust biosensors.

Smartphone-Based Pure DNAzyme Hydrogel Platform for Visible and Portable Colorimetric Detection of Cell-Free DNA

Cell-free DNA (cfDNA), as a tumor marker, is of great importance for the diagnosis of cancer and targeted therapy. However, the need for huge analytical instruments for cfDNA analysis has restricted its practical applications, especially in rural areas and third-world countries. Herein, a portable and visual smartphone-based DNAzyme hydrogel platform is developed for cfDNA detection. The target cfDNA triggers rolling circle amplification to produce a G-quadruplex-comprised DNA hydrogel with an horseradish peroxidase (HRP)-like catalytic function, which further catalyzes the chromogenic substrate to generate a visible output signal. Notably, the naked-eye detection of cfDNA can be realized by the macroscale visibility and catalytic ability of the DNA hydrogel. The linear range of the DNAzyme hydrogel platform for cfDNA detection is 0.1 pM-1500 nM with a detection limit of 0.042 pM. Moreover, this platform is exploited for the detection of cfDNA in spiked human serum with favorable sensitivity and recovery. Therefore, the DNAzyme hydrogel platform provides highly promising potential for testing other nucleic acid biomarkers.

Current hydrogel advances in physicochemical and biological response-driven biomedical application diversity

Hydrogel is a type of versatile platform with various biomedical applications after rational structure and functional design that leverages on material engineering to modulate its physicochemical properties (e.g., stiffness, pore size, viscoelasticity, microarchitecture, degradability, ligand presentation, stimulus-responsive properties, etc.) and influence cell signaling cascades and fate. In the past few decades, a plethora of pioneering studies have been implemented to explore the cell-hydrogel matrix interactions and figure out the underlying mechanisms, paving the way to the lab-to-clinic translation of hydrogel-based therapies. In this review, we first introduced the physicochemical properties of hydrogels and their fabrication approaches concisely. Subsequently, the comprehensive description and deep discussion were elucidated, wherein the influences of different hydrogels properties on cell behaviors and cellular signaling events were highlighted. These behaviors or events included integrin clustering, focal adhesion (FA) complex accumulation and activation, cytoskeleton rearrangement, protein cyto-nuclei shuttling and activation (e.g., Yes-associated protein (YAP), catenin, etc.), cellular compartment reorganization, gene expression, and further cell biology modulation (e.g., spreading, migration, proliferation, lineage commitment, etc.). Based on them, current in vitro and in vivo hydrogel applications that mainly covered diseases models, various cell delivery protocols for tissue regeneration and disease therapy, smart drug carrier, bioimaging, biosensor, and conductive wearable/implantable biodevices, etc. were further summarized and discussed. More significantly, the clinical translation potential and trials of hydrogels were presented, accompanied with which the remaining challenges and future perspectives in this field were emphasized. Collectively, the comprehensive and deep insights in this review will shed light on the design principles of new biomedical hydrogels to understand and modulate cellular processes, which are available for providing significant indications for future hydrogel design and serving for a broad range of biomedical applications.