Development of orally-deliverable DNA hydrogel by microemulsification and chitosan coating

Chitosan non-particulate vaccine delivery systems

Chitosan is an extensively used polymer for drug delivery applications in particulate and non-particulate carriers. Chitosan-based particulate, nano-, and microparticle, carriers have been the most extensively studied for the delivery of therapeutics and vaccines. However, chitosan has also been used in vaccine applications for its adjuvant properties in various hydrogels or as a carrier coating material. The focus of this review will be on the usage of chitosan as a vaccine adjuvant based on its intrinsic immunogenicity; the various forms of chitosan-based non-particulate delivery systems such as thermosensitive hydrogels, microneedles, and conjugates; and the advantages of its role as a coating material for vaccine carriers.

Tuning CpG motif position in nanostructured DNA for efficient immune stimulation

It was previously demonstrated that polypod-like nanostructured DNA (polypodna) comprising three or more oligodeoxynucleotides (ODNs) were useful for the delivery of ODNs containing cytosine-phosphate-guanine (CpG) motifs, or CpG ODNs, to immune cells. Although the immunostimulatory activity of single-stranded CpG ODNs is highly dependent on CpG motif sequence and position, little is known about how the position of the motif affects the immunostimulatory activity of CpG motif-containing nanostructured DNAs. In the present study, four series of polypodna were designed, each comprising a CpG ODN with one potent CpG motif at varying positions and 2-5 CpG-free ODNs, and investigated their immunostimulatory activity using Toll-like receptor-9 (TLR9)-positive murine macrophage-like RAW264.7 cells. Polypodnas with the CpG motif in the 5'-overhang induced more tumor necrosis factor-α release than those with the motif in the double-stranded region, even though their cellular uptake were similar. Importantly, the rank order of the immunostimulatory activity of single-stranded CpG ODNs changed after their incorporation into polypodna. These results indicate that the CpG ODN sequence as well as the motif location in nanostructured DNAs should be considered for designing the CpG motif-containing nanostructured DNAs for immune stimulation.

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.

Progress in Programmable DNA-Aided Self-Assembly of the Master Frame of a Drug Delivery System

Every year cancer causes approximately 10 million deaths globally. Researchers have developed numerous targeted drug delivery systems (DDSs) with nanoparticles, polymers, and liposomes, but these synthetic materials have poor degradability and low biocompatibility. Because DNA nanostructures have good degradability and high biocompatibility, extensive studies have been performed to construct DDSs with DNA nanostructures as the molecular-layer master frame (MF) assembled via programmable DNA-aided self-assembly for targeted drug release. To learn the progressing trend of self-assembly techniques and keep pace with their recent rapid advancements, it is crucial to provide an overview of their past and recent progress. In this review article, we first present the techniques to assemble the MF of a DDS with solely DNA strands; to assemble MFs with one or more additional type of construction materials, e.g., polymers (including RNA and protein), inorganic nanoparticle, or metal ions, in addition to DNA strands; and to assemble the more complex DNA nanocomplexes. It is observed that both the techniques used and the MFs constructed have become increasingly complex and that the DDS constructed has an increasing number of advanced functions. From our focused review, we anticipate that DDSs with the MF of multiple building materials and DNA nanocomplexes will attract an increasing number of researchers' interests. On the basis of knowledge about materials and functional components (e.g., targeting aptamers/peptides/antibodies and stimuli for drug release) obtained from previously performed studies, researchers can combine more materials with DNA strands to assemble more powerful MFs and incorporate more components to endow DDSs with improved or additional properties/functions, thereby subsequently contributing to cancer prevention.

Natural Polymeric Composites Derived from Animals, Plants, and Microbes for Vaccine Delivery and Adjuvant Applications: A Review

A key element in ensuring successful immunization is the efficient delivery of vaccines. However, poor immunogenicity and adverse inflammatory immunogenic reactions make the establishment of an efficient vaccine delivery method a challenging task. The delivery of vaccines has been performed via a variety of delivery methods, including natural-polymer-based carriers that are relatively biocompatible and have low toxicity. The incorporation of adjuvants or antigens into biomaterial-based immunizations has demonstrated better immune response than formulations that just contain the antigen. This system may enable antigen-mediated immunogenicity and shelter and transport the cargo vaccine or antigen to the appropriate target organ. In this regard, this work reviews the recent applications of natural polymer composites from different sources, such as animals, plants, and microbes, in vaccine delivery systems.

Tannic acid: a versatile polyphenol for design of biomedical hydrogels

Tannic acid (TA), a natural polyphenol, is a hydrolysable amphiphilic tannin derivative of gallic acid with several galloyl groups in its structure. Tannic acid interacts with various organic, inorganic, hydrophilic, and hydrophobic materials such as proteins and polysaccharides via hydrogen bonding, electrostatic, coordinative bonding, and hydrophobic interactions. Tannic acid has been studied for various biomedical applications as a natural crosslinker with anti-inflammatory, antibacterial, and anticancer activities. In this review, we focus on TA-based hydrogels for biomaterials engineering to help biomaterials scientists and engineers better realize TA's potential in the design and fabrication of novel hydrogel biomaterials. The interactions of TA with various natural or synthetic compounds are deliberated, discussing parameters that affect TA-material interactions thus providing a fundamental set of criteria for utilizing TA in hydrogels for tissue healing and regeneration. The review also discusses the merits and demerits of using TA in developing hydrogels either through direct incorporation in the hydrogel formulation or indirectly via immersing the final product in a TA solution. In general, TA is a natural bioactive molecule with diverse potential for engineering biomedical hydrogels.

Injectable DNA Hydrogel-Based Local Drug Delivery and Immunotherapy

Regulated drug delivery is an important direction in the field of medicine and healthcare research. In recent years, injectable hydrogels with good biocompatibility and biodegradability have attracted extensive attention due to their promising application in controlled drug release. Among them, DNA hydrogel has shown great potentials in local drug delivery and immunotherapy. DNA hydrogel is a three-dimensional network formed by cross-linking of hydrophilic DNA strands with extremely good biocompatibility. Benefiting from the special properties of DNA, including editable sequence and specificity of hybridization reactions, the mechanical properties and functions of DNA hydrogels can be precisely designed according to specific applications. In addition, other functional materials, including peptides, proteins and synthetic organic polymers can be easily integrated with DNA hydrogels, thereby enriching the functions of the hydrogels. In this review, we first summarize the types and synthesis methods of DNA hydrogels, and then review the recent research progress of injectable DNA hydrogels in local drug delivery, especially in immunotherapy. Finally, we discuss the challenges facing DNA hydrogels and future development directions.

Ionic co-aggregates (ICAs) based oral drug delivery: Solubilization and permeability improvement

Due to the overwhelming percentage of poorly water-soluble drugs, pharmaceutical industry is in urgent need of efficient approaches for solubilization and permeability improvement. Salts consisting of lipophilic fatty acid anions and hydrophilic choline cations are found to be surface active and able to form ionic co-aggregates (ICAs) in water. Choline oleate-based ICAs significantly enhance oral absorption of paclitaxel (PTX) as compared with cremophor EL-based micelles (MCs). Aggregation-caused quenching probes enable tracking of intact ICAs in in vivo transport and cellular interaction. Prolonged intestinal retention of ICAs than MCs implies stronger solubilizing capability in vivo. Ex vivo imaging of major organs and intestinal tracts suggests transepithelial transport of intact ICAs. Cellular studies support the enhanced absorption of PTX and transmembrane transport of intact ICAs. In conclusion, ICAs, consisting of lipophilic ions and hydrophilic counter-ions, are of great potential in delivery of poorly water-soluble drugs by enhancing solubility and permeability.

Emerging Fabrication Strategies of Hydrogels and Its Applications

Recently, hydrogels have been investigated for the controlled release of bioactive molecules, such as for living cell encapsulation and matrices. Due to their remote controllability and quick response, hydrogels are widely used for various applications, including drug delivery. The rate and extent to which the drugs reach their targets are highly dependent on the carriers used in drug delivery systems; therefore the demand for biodegradable and intelligent carriers is progressively increasing. The biodegradable nature of hydrogel has created much interest for its use in drug delivery systems. The first part of this review focuses on emerging fabrication strategies of hydrogel, including physical and chemical cross-linking, as well as radiation cross-linking. The second part describes the applications of hydrogels in various fields, including drug delivery systems. In the end, an overview of the application of hydrogels prepared from several natural polymers in drug delivery is presented.

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.

Chitosan-Based Coacervate Polymers for Propolis Encapsulation: Release and Cytotoxicity Studies

Chitosan-DNA (CS-DNA) and Chitosan-Pectin (CS-P) hydrogels were formulated as a sustained drug delivery carrier for drug delivery. For this, hydrogels were prepared by emulsion technique: mixing aqueous phase of the CS and DNA or P solution with benzyl alcohol using a high-performance dispersing instrument. Green Propolis (GP) was incorporated by imbibition: hydrogels were placed in GP aqueous solution (70 µg/mL) for 2 h. The specimens were freeze-dried and then characterized using different techniques. In vitro cell viability and morphology were also performed using the MG63 cell line. The presence of P was evidenced by the occurrence of a strong band at 1745 cm-1, also occurring in the blend. DNA and CS-DNA showed a strong band at 1650 cm-1, slightly shifted from the chitosan band. The sorption of GP induced a significant modification of the gel surface morphology and some phase separation occurs between chitosan and DNA. Drug release kinetics in water and in saliva follow a two-step mechanism. Significant biocompatibility revealed that these hydrogels were non-toxic and provided acceptable support for cell survival. Thus, the hydrogel complexation of chitosan with DNA and with Pectin provides favorable micro-environment for cell growth and is a viable alternative drug delivery system for Green Propolis.

Tailoring DNA Self-assembly to Build Hydrogels

DNA hydrogels are crosslinked polymeric networks in which DNA is used as the backbone or the crosslinker. These hydrogels are novel biofunctional materials that possess the biological character of DNA and the framed structure of hydrogels. Compared with other kinds of hydrogels, DNA hydrogels exhibit not only high mechanical strength and controllable morphologies but also good recognition ability, designable responsiveness, and programmability. The DNA used in this type of hydrogel acts as a building block for self-assembly or as a responsive element due to its sequence recognition ability and switchable structural transitions, respectively. In this review, we describe recent developments in the field of DNA hydrogels and discuss the role played by DNA in these hydrogels. Various synthetic strategies for and a range of applications of DNA hydrogels are detailed.

Current and New Approaches for Mucosal Vaccine Delivery

Mucosal surfaces are the interface between the host’s internal milieu and the external environment, and they have dual functions, serving as physical barriers to foreign antigens and as accepting sites for vital materials. Mucosal vaccines are more favored to prevent mucosal infections from the portal of entry. Although mucosal vaccination has many advantages, licensed mucosal vaccines are scarce. The most widely studied mucosal routes are oral and intranasal. Licensed oral and intranasal vaccines are composed mostly of whole cell killed or live attenuated microorganisms serving as both delivery systems and built-in adjuvants. Future mucosal vaccines should be made with more purified antigen components, which will be relatively less immunogenic. To induce robust protective immune responses against well-purified vaccine antigens, an effective mucosal delivery system is an essential requisite. Recent developments in biomaterials and nanotechnology have enabled many innovative mucosal vaccine trials. For oral vaccination, the vaccine delivery system should be able to stably carry antigens and adjuvants and resist harsh physicochemical conditions in the stomach and intestinal tract. Besides many nano/microcarrier tools generated by using natural and chemical materials, the development of oral vaccine delivery systems using food materials should be more robustly researched to expand vaccine coverage of gastrointestinal infections in developing countries. For intranasal vaccination, the vaccine delivery system should survive the very active mucociliary clearance mechanisms and prove safety because of the anatomical location of nasal cavity separated by a thin barrier. Future mucosal vaccine carriers, regardless of administration routes, should have certain common characteristics. They should maintain stability in given environments, be mucoadhesive, and have the ability to target specific tissues and cells.

Nanostructured DNA for the delivery of therapeutic agents

DNA and RNA, the nucleic acids found in every living organism, are quite crucial, because not only do they store the genetic information, but also they are used as signals through interaction with various molecules within the body. The nature of nucleic acids, especially DNA, to form double-helix makes it possible to design nucleic acid-based nanostructures with various shapes. Because the shapes as well as the physicochemical properties determine their interaction with proteins or cells, nanostructured DNAs will have different features in the interaction compared with single- or double-stranded DNA. Some of these unique features of nanostructured DNA make ways for efficient delivery of therapeutic agents to specific targets. In this review, we begin with the factors affecting the properties of nanostructured DNA, followed by summarizing the methods for the development of nanostructured DNA. Further, we discuss the characteristics of nanostructured DNA and their applications for the delivery of bioactive compounds.