Description

A novel functional material known as micro-nano hydrogel has received a lot of attention across a variety of fields. The micronano hydrogels are regarded as promising agents in tissue repair engineering due to their ability to achieve minimally invasive repair, high water content, and high specific surface area. The most recent advancements in the use of microgels for local drug delivery, bone tissue repair, soft tissue repair, and immunomodulation, as well as the most recent advancements in the use of nanohydrogels for cartilage repair, antibacterial, antitumor/cancer nerve repair, and disease prevention and diagnosis, are described in detail. Additionally, the most important future research directions for micro-nano hydrogel preparation technologies are made clear. Hydrogel is a profoundly hydrophilic delicate material, because of its inside 3D cross-connected network structure like extracellular framework, and simultaneously has the qualities of high enlarging, fantastic biocompatibility and exceptional shape pliancy. Numerous applications for hydrogel include wound dressings, scaffolds for tissue engineering, tissue patches, and drug delivery systems. However, because of the risk of infection posed by implantation trauma, conventional bulk hydrogels are increasingly limited in clinical use, particularly when specific sizes are required. Because injectable hydrogels have excellent self-healing properties and can even gel in situ, point-based implantation of irregular threedimensional structures can be accomplished with minimal invasiveness.

Principles and Techniques of Micro-Nano Hydrogel Preparation

In any case, there are still a few undeniable burdens here, most importantly, because of the lopsided shape and huge size of the hydrogel, a somewhat high and lopsided infusion force is definitely created during infusion. In addition, bulk injectable gels' difficult-to-manage release rate of encapsulated drugs frequently results in rapid drug activity failure. Because of quicker gelation, the interaction might prompt bundle disappointment and spillage preceding delivery we explore the super biomedical uses of microgels, including skin drug conveyance, bone tissue fix, delicate tissue fix, and immunomodulation, as well as nanogels for tissue fix, including ligament fix, hostile to contamination, against growth/disease, nerve fix and anticipation and determination of infections. In a nutshell, the purpose of this review is to present the potential applications of micro-nano hydrogels in biomedicine and to present new opportunities for the design and development of advanced biomaterials in the future. To that end, the principles and techniques of micro-nano hydrogel preparation are summarized. A rich library of polymers have been utilized for the plan and creation of biomedical hydrogels. Natural and synthetic polymers are the two main types of these polymers. The chemical method includes covalent crosslinking and dynamic covalent crosslinking, as well as free radical polymerization, Schiff base reaction, and other similar processes. The physical method, on the other hand, is primarily divided into chemical and physical methods depending on the preparation method and mechanism. Peptide self-assembly, host-guest left-and-right, polymer chain entanglement, hydrogen bonding, and other physical methods are examples. Cellulose is a linear polysaccharide made up of repeating D-glucose units that are linked by a linkage of less than 1, 4. Cellulose is the principal part of plant cell wall and is viewed as the most bountiful natural polymer on the planet. Chitin is a key component not only of crustacean exoskeletons but also of the arthropod cuticle as a whole. Hyaluronic corrosive (HA) is a Glycosaminoglycan (GAG) that is comprised of exchanging disaccharide units of dglucuronic corrosive and N-acetyl-d-glucosamine, associated explicitly by β-linkages. Blocks of (1,4)-linked -d-mannuronate (M) and -l-guluronate (G) residues make up alginate. A block typically consists of three distinct types of polymer segments, each of which is derived from another: G residues that never change, M residues that never change, and alternating MG residues. Hydrolyzed collagen yields gelatin, a fibrous protein with a distinctive amino acid sequence. The majority of connective tissue, including skin, tendons, and bones, is collagen. Polyvinyl Alcohol (PVA) is a linear synthetic polymer made by hydrolyzing ethyl polyacetate either partially or completely. One of the few vinyl polymers that are soluble in water but almost insoluble in organic solvents is PVA, which is well-known. Polyethylene Glycol (PEG) is a synthetic, water-soluble, viscous, amphiphilic polymer that is typically made by polymerizing ethylene oxide in an anionic or cationic manner.

An Advanced Method of Liquid Atomization

Microgels can either self-assemble in situ to form irregular structures or encapsulate a variety of active factors for tissue regeneration. Their typical diameter is between 1 and 1000 m. Spray drying, electrohydrodynamic spraying, microfluidics, and 3D-bioprinting are just a few of the common approaches to making micro hydrogels that are discussed in this section. A spray dryer, which typically consists of an atomizer and a drying chamber, is used in the spray drying method. Drugs, polymers, and particle solutions and suspensions are atomized into fine droplets. In the drying chamber, a stream of hot air causes the solvent to quickly evaporate from the droplets, resulting in the formation of microspheres or microgels with a diameter of one to ten micrometers. An advanced method of liquid atomization called electrohydrodynamic spraying uses a high electric field to overcome the liquid's surface tension. Simply put, the polymer solution is extruded through a high-voltage metal needle tip or nozzle. Under the influence of a strong electrostatic field, the droplets in the needle that is connected to the high-voltage generator become Taylor cones and then cross-link to form micron-sized capsules. Based on emulsion techniques, droplet microfluidics is an ideal platform for the synthesis of hydrogel microspheres. Geometric channels, such as T-shaped and Yshaped connections, connect two or more immiscible fluids in the microfluidic emulsion system and afterward beads are shaped. Micro-nano hydrogels overcome the drawbacks of conventional hydrogels to make it possible to deliver drugs or biomolecules to a wider area and further away. A whole new world of possibilities for tissue repair engineering have emerged as a result of significant advancements in the technical methods and engineering design of micro-nano hydrogel preparation over the past two decades. Although numerous studies have fully demonstrated the numerous advantages of micro-nano hydrogels in biomedical applications, there are still significant issues to be resolved, particularly with regard to scale and industrialization, structural design diversity and richness, and the interaction between biomaterials and cells.