Functionalized DNA Hydrogels Produced by Polymerase-Catalyzed Incorporation of Non-Natural Nucleotides as a Surface Coating for Cell Culture Applications

Injectable hydrogels as emerging drug-delivery platforms for tumor therapy

Tumor therapy continues to be a prominent field within biomedical research. The development of various drug carriers has been propelled by concerns surrounding the side effects and targeting efficacy of various chemotherapeutic drugs and other therapeutic agents. These carriers strive to enhance drug concentration at tumor sites, minimize systemic side effects, and improve therapeutic outcomes. Among the reported delivery systems, injectable hydrogels have emerged as an emerging candidate for the in vivo delivery of chemotherapeutic drugs due to their minimal invasive drug delivery properties. This review systematically summarizes the composition and preparation methodologies of injectable hydrogels and further highlights the delivery mechanisms of diverse drugs using these hydrogels for tumor therapy, along with an in-depth discussion on the optimized therapeutic efficiency of drugs encapsulated within the hydrogels. The work concludes by providing a dynamic forward-looking perspective on the potential challenges and possible solutions of the in situ injectable hydrogels for non-surgical and real-time diagnostic applications.

Rational Design of DNA Hydrogels Based on Molecular Dynamics of Polymers

In recent years, DNA has emerged as a fascinating building material to engineer hydrogel due to its excellent programmability, which has gained considerable attention in biomedical applications. Understanding the structure-property relationship and underlying molecular determinants of DNA hydrogel is essential to precisely tailor its macroscopic properties at molecular level. In this review, the rational design principles of DNA molecular networks based on molecular dynamics of polymers on the temporal scale, which can be engineered via the backbone rigidity and crosslinking kinetics, are highlighted. By elucidating the underlying molecular mechanisms and theories, it is aimed to provide a comprehensive overview of how the tunable DNA backbone rigidity and the crosslinking kinetics lead to desirable macroscopic properties of DNA hydrogels, including mechanical properties, diffusive permeability, swelling behaviors, and dynamic features. Furthermore, it is also discussed how the tunable macroscopic properties make DNA hydrogels promising candidates for biomedical applications, such as cell culture, tissue engineering, bio-sensing, and drug delivery.

Dynamic DNA Nanostructures for Cell Manipulation

Dynamic DNA nanostructures are DNA nanostructures with reconfigurable elements that can undergo structural transformations in response to specific stimuli. Thus, anchoring dynamic DNA nanostructures on cell membranes is an attractive and promising strategy for well-controlled cell manipulation. Here, we review the latest progress in dynamic DNA nanostructures for cell manipulation. Commonly used mechanisms for dynamic DNA nanostructures are first introduced. Subsequently, we summarize the anchoring strategies for dynamic DNA nanostructures on cell membranes and list possible applications (including programming cell membrane receptors, controlling ligand activity and drug delivery, capturing and releasing cells, and assembling cells into clusters). Finally, insights into the remaining challenges are presented.

Programmable DNA Hydrogels as Artificial Extracellular Matrix

The cell microenvironment plays a crucial role in regulating cell behavior and fate in physiological and pathological processes. As the fundamental component of the cell microenvironment, extracellular matrix (ECM) typically possesses complex ordered structures and provides essential physical and chemical cues to the cells. Hydrogels have attracted much attention in recapitulating the ECM. Compared to natural and synthetic polymer hydrogels, DNA hydrogels have unique programmable capability, which endows the material precise structural customization and tunable properties. This review focuses on recent advances in programmable DNA hydrogels as artificial extracellular matrix, particularly the pure DNA hydrogels. It introduces the classification, design, and assembly of DNA hydrogels, and then summarizes the state-of-the-art achievements in cell encapsulation, cell culture, and tissue engineering with DNA hydrogels. Ultimately, the challenges and prospects for cellular applications of DNA hydrogels are delivered.

Prospects and challenges of dynamic DNA nanostructures in biomedical applications

The physicochemical nature of DNA allows the assembly of highly predictable structures via several fabrication strategies, which have been applied to make breakthroughs in various fields. Moreover, DNA nanostructures are regarded as materials with excellent editability and biocompatibility for biomedical applications. The ongoing maintenance and release of new DNA structure design tools ease the work and make large and arbitrary DNA structures feasible for different applications. However, the nature of DNA nanostructures endows them with several stimulus-responsive mechanisms capable of responding to biomolecules, such as nucleic acids and proteins, as well as biophysical environmental parameters, such as temperature and pH. Via these mechanisms, stimulus-responsive dynamic DNA nanostructures have been applied in several biomedical settings, including basic research, active drug delivery, biosensor development, and tissue engineering. These applications have shown the versatility of dynamic DNA nanostructures, with unignorable merits that exceed those of their traditional counterparts, such as polymers and metal particles. However, there are stability, yield, exogenous DNA, and ethical considerations regarding their clinical translation. In this review, we first introduce the recent efforts and discoveries in DNA nanotechnology, highlighting the uses of dynamic DNA nanostructures in biomedical applications. Then, several dynamic DNA nanostructures are presented, and their typical biomedical applications, including their use as DNA aptamers, ion concentration/pH-sensitive DNA molecules, DNA nanostructures capable of strand displacement reactions, and protein-based dynamic DNA nanostructures, are discussed. Finally, the challenges regarding the biomedical applications of dynamic DNA nanostructures are discussed.

Recent Advances in Stimuli-Responsive DNA-Based Hydrogels

Stimuli-responsive DNA-based hydrogels are attracting growing interest because of their smart responsiveness, excellent biocompatibility, regulated biodegradability, and programmable design properties. Integration of reconfigurable DNA architectures and switchable supramolecular moieties (as cross-linkers) in hydrogels by responding to external stimuli provides an ideal approach for the reversible tuning structural and mechanical properties of the hydrogels, which can be exploited in the development of intelligent DNA-based materials. This review highlights recent advances in the design of responsive pure DNA hydrogels, DNA-polymer hybrid hydrogels, and autonomous DNA-based hydrogels with transient behaviors. A variety of chemically and physically triggered DNA-based stimuli-responsive hydrogels and their versatile applications in biosensing, biocatalysis, cell culture and separation, drug delivery, shape memory, self-healing, and robotic actuators are summarized. Finally, we address the key challenges that the field will face in the coming years, and future prospects are identified.

DNA Optoelectronics: Versatile Systems for On-Demand Functional Electrochemical Applications

Herein, we propose innovative deoxyribonucleic acid (DNA)-based gels and their applications in diverse optoelectronics. We prepared the optoelectronic DNA-based gels (^OpDNA Gel) through molecular complexation, that is, groove binding and ionic interactions of DNA and 1,1'-diheptyl-4,4'-bipyridinium (DHV). This process is feasible even with sequence-nonspecific DNA extracted from nature (e.g., salmon testes), resulting in the expansion of the application scope of DNA-based gels. ^OpDNA Gel possessed good mechanical characteristics (e.g., high compressibility, thermoplasticity, and outstanding viscoelastic properties) that have not been observed in typical DNA hydrogels. Moreover, the electrochromic (EC) characteristics of DHV were not lost when combined with ^OpDNA Gel. By taking advantage of the facile moldability, voltage-tunable EC behavior, and biocompatibility/biodegradability of ^OpDNA Gel, we successfully demonstrated its applicability in a variety of functional electrochemical systems, including on-demand information coding systems, user-customized EC displays, and microorganism monitoring systems. The ^OpDNA Gel is a promising platform for the application of DNA-based biomaterials in electrochemical optoelectronics.

Designer DNA Hydrogels Stimulate 3D Cell Invasion by Enhanced Receptor Expression and Membrane Endocytosis

DNA has emerged as one of the smartest biopolymers to bridge the gap between chemical science and biology to design scaffolds like hydrogels by physical entanglement or chemical bonding with remarkable properties. We present here a completely new application of DNA-based hydrogels in terms of their capacity to stimulate membrane endocytosis, leading to enhanced cell spreading and invasion for cells in ex vivo 3D spheroids models. Multiscale simulation studies along with DLS data showed that the hydrogel formation was enhanced at lower temperature and it converts to liquid with increase in temperature. DNA hydrogels induced cell spreading as observed by the increase in cellular area by almost two-fold followed by an increase in the receptor expression, the endocytosis, and the 3D invasion potential of migrating cells. Our first results lay the foundation for upcoming diverse applications of hydrogels to probe and program various cellular and physiological processes that can have lasting applications in stem cell programming and regenerative therapeutics.

XT-type DNA hydrogels loaded with VEGF and NGF promote peripheral nerve regeneration via a biphasic release profile

Peripheral nerve injury (PNI) remains an unresolved challenge in the medicine area. With the development of biomaterial science and tissue engineering, a variety of nerve conduits were widely applied for repairing long defect PNI. DNA materials are developing rapidly due to their multiple advantages. In the present study, we aim to combine a DNA hydrogel, vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) to construct a new type of delivery system, which could achieve a biphasic release profile of VEGF and NGF by taking advantage of the different degradation rates between X- and T-type DNA. In vitro results showed that the DNA gel + VEGF/NGF system could promote proliferation, migration and myelination of Rat Schwann cells (RSC) while maintaining cell viability. In vivo results indicated a better effect of DNA gel + VEGF/NGF on promoting repair of long defect PNI than the hollow chitin conduits (CT), DNA gel or VEGF/NGF group. The new technology invention holds promising clinical application prospects for repairing PNI and may be used broadly after step-by-step improvement.

Programmable, self-assembled DNA nanodevices for cellular programming and tissue engineering

DNA-based nanotechnology has evolved into an autonomous, highly innovative, and dynamic field of research at the nexus of supramolecular chemistry, nanotechnology, materials science, and biotechnology. DNA-based materials, including origami nanodevices, have started to emerge as an ideal scaffold for use in cellular programming, tissue engineering, and drug delivery applications. We cover herein the applications for DNA as a scaffold for interfacing with, and guiding, the activity of biological systems like cells and tissues. Although DNA is a highly programmable molecular building block, it suffers from a lack of functional capacity for guiding and modulating cells. Coupling DNA to biologically active molecules can bestow bioactivity to these nanodevices. The main goal of such nanodevices is to synthesize systems that can bind to cells and mimic the extracellular environment, and serve as a highly promising toolbox for multiple applications in cellular programming and tissue engineering. DNA-based programmable devices offer a highly promising approach for programming collections of cells, tissue engineering, and regenerative medicine applications.

Putting DNA to Work as Generic Polymeric Materials

DNA is a true polymer that stores the genetic information of an organism. With its amazing biological and polymeric characteristics, DNA has been regarded as a universal building block for the construction of diverse materials for real-world applications. Through various approaches including ligation, polymerization, chemical crosslinking, and physical crosslinking, both pure and hybrid DNA gels have been developed as generic materials. This Review discusses recent advances in the construction of DNA-based networks without considering any of DNA's genetic properties. In addition, we highlight the biomedical and non-biomedical applications of DNA as generic materials. Owing to the superb molecular recognition, self-assembly, and responsiveness of DNA, a mushrooming number of DNA materials with various properties have been developed for general utilization.

Non-invasive Regulation of Cellular Morphology Using a Photoswitchable Mechanical DNA Polymer

The extracellular matrix (ECM) in which the cells reside provides a dynamic and reversible environment. Spatiotemporal cues are essential when cells are undergoing morphogenesis, repair and differentiation. Emulation of such an intricate system with reversible presentation of nanoscale cues can help us better understand cellular processes and can allow the precise manipulation of cell function in vitro. Herein, we formulated a photoswitchable DNA mechanical nanostructure containing azobenzene moieties and dynamically regulated the spatial distance between adhesion peptides using a photoswitchable DNA polymer with photoirradiation. We found that the DNA polymer reversibly forms two different structures, a relaxed linear and shrunken compact form, observed by AFM. Using the mechanical properties of this DNA polymer, UV and visible light irradiation induced a significant morphology change of the cells between a round shape and spindle shape, thus providing a tool to decipher the language of the ECM better.

Smart and Functionalized Development of Nucleic Acid-Based Hydrogels: Assembly Strategies, Recent Advances, and Challenges

Nucleic acid-based hydrogels that integrate intrinsic biological properties of nucleic acids and mechanical behavior of their advanced assemblies are appealing bioanalysis and biomedical studies for the development of new-generation smart biomaterials. It is inseparable from development and incorporation of novel structural and functional units. This review highlights different functional units of nucleic acids, polymers, and novel nanomaterials in the order of structures, properties, and functions, and their assembly strategies for the fabrication of nucleic acid-based hydrogels. Also, recent advances in the design of multifunctional and stimuli-responsive nucleic acid-based hydrogels in bioanalysis and biomedical science are discussed, focusing on the applications of customized hydrogels for emerging directions, including 3D cell cultivation and 3D bioprinting. Finally, the key challenge and future perspectives are outlined.

Functional DNA-based hydrogel intelligent materials for biomedical applications

Multifunctional intelligent DNA hydrogels have been reviewed for many biomedical applications.

The influence of structural gradients in large pore organosilica materials on the capabilities for hosting cellular communities

Cells exist in the so-called extracellular matrix (ECM) in their native state, and numerous future applications require reliable and potent ECM-mimics. A perspective, which goes beyond ECM emulation, is the design of a host-material with features which are not accessible in the biological portfolio. Such a feature would, for instance, be the creation of a structural or chemical gradient, and to explore how this special property influences the biological processes. First, we wanted to test if macroporous organosilica materials with appropriate surface modification can act as a host for the implementation of human cells like HeLa or LUHMES. It was possible to use a commercially available polymeric foam as a scaffold and coat it with a thiophenol-containing organosilica layer, followed by biofunctionalization with biotin using click chemistry and the subsequent coupling of streptavidin–fibronectin to it. More importantly, deformation of the scaffold allowed the generation of a permanent structural gradient. In this work, we show that the structural gradient has a tremendous influence on the capability of the described material for the accommodation of living cells. The introduction of a bi-directional gradient enabled the establishment of a cellular community comprising different cell types in spatially distinct regions of the material. An interesting perspective is to study communication between cell types or to create cellular communities, which can never exist in a natural environment.

Chemical and structural gradients in biofunctionalized organosilica–polymer nanocomposites control cell adhesion properties and open perspectives for artificial cellular community systems.