Abstract
Hydrogels from biopolymers are readily synthesized, can possess various characteristics for different applications, and have been widely used in biomedicine to help with patient treatments and outcomes. Polysaccharides, polypeptides, and nucleic acids can be produced into hydrogels, each for unique purposes depending on their qualities. Examples of polypeptide hydrogels include collagen, gelatin, and elastin, and polysaccharide hydrogels include alginate, cellulose, and glycosaminoglycan. Many different theories have been formulated to research hydrogels, which include Flory-Rehner theory, Rubber Elasticity Theory, and the calculation of porosity and pore size. All these theories take into consideration enthalpy, entropy, and other thermodynamic variables so that the structure and pore sizes of hydrogels can be formulated. Hydrogels can be fabricated in a straightforward process using a homogeneous mixture of different chemicals, depending on the intended purpose of the gel. Different types of hydrogels exist which include pH-sensitive gels, thermogels, electro-sensitive gels, and light-sensitive gels and each has its unique biomedical applications including structural capabilities, regenerative repair, or drug delivery. Major biopolymer-based hydrogels used for cell delivery include encapsulated skeletal muscle cells, osteochondral muscle cells, and stem cells being delivered to desired locations for tissue regeneration. Some examples of hydrogels used for drug and biomolecule delivery include insulin encapsulated hydrogels and hydrogels that encompass cancer drugs for desired controlled release. This review summarizes these newly developed biopolymer-based hydrogel materials that have been mainly made since 2015 and have shown to work and present more avenues for advanced medical applications.
Highlights
Biopolymers are polymers that are made up of many individual monomers, or units, within an organism
Some common examples of biopolymers include nucleic acids which make up deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), polypeptides or proteins are made up of amino acids that are coded by nucleic acids, and polysaccharides which are complex molecules consisting of carbohydrates [4]
The single unit for polysaccharides is the monosaccharides [7]. Both polypeptides and polysaccharides can be used to create biopolymer materials that can be utilized for biomedical applications such as tissue engineering and drug delivery
Summary
Biopolymers are polymers that are made up of many individual monomers, or units, within an organism. A specific example would be a alginate-gum tragacanth hydrogel, a hydrogel composed of a polysaccharide, which released insulin in certain pH levels leading to release of insulin in only desired areas [17] Nucleic acids, such as DNA, can be formulated into hydrogels for other biomedical applications [18]. Different hydrogels will be discussed, including those constructed from both polypeptide and polysaccharide biopolymers Fabrications methods for these hydrogels will be described as well, Fabrication methods that will be reviewed include a batch reactor chamber, 3D printing, physical cross linking, and topological entanglement. These methods all help create biopolymer-based hydrogels that can later be used for major biomedical applications [19]. Quaternary structure, which isn’t necessarily reached in all functional proteins, is the intertwining of multiple separate polypeptide chains to create a new functional protein created via the arrangement of these multiple chains [5,20]
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