Alginate is a naturally occurring anionic biopolymer derived from brown algae. It is readily available, biocompatible and non-toxic. Wound dressings made from alginate provide a moist environment and reduce bacterial infection, which are important factors in wound healing. Alginate is derived from Phaeophyceae, vine, seaweed, Japanese kelp, macrocystis and digitata. It is composed of glutarate and manuronate in varying proportions depending on the source. It is composed of (1,4) linked β-d-manuronate (M) and α-l-glutarate (G) residues. Its blocks are composed of consecutive G and M residues and alternating M and G residues (GMGMGM). Alginates contain sequences of M and G residues in different proportions, which determine their physical properties and molecular weight. Studies have shown that the gelling properties of alginate are due to the presence of calcium ions. These calcium ions play an important role in the formation of a slowly degrading cross-linked polymer gel of alginate. When the dressing comes into contact with an exuding wound, the calcium ions in the alginate undergo an ion exchange reaction with the sodium ions in the serum or wound fluid. When most of the calcium ions on the fibres are replaced by sodium ions, the fibres swell and partially dissolve to form a gel-like substance. This gel is highly hydrophilic, which can restrict the flow of wound secretions and minimise bacterial contamination. Mannuronic acid-containing alginates form soft gels, whereas guluronic acid-containing alginates form harder gels that are more absorbent of exudate.
Figure 1. In vitro phagocytic uptake of Rhodamine B-labeled alginate sealed GP (Rd-GP) by J774 cells.(Upadhyay TK, et al. 2017)
Calcium alginate dressings may have a stimulatory effect on the production of fibroblasts, thereby supporting tissue regeneration and healing processes in vitro and in vivo. Fibroblasts are widely believed to play an important role in tissue regeneration and healing. Studies have shown that calcium alginate can activate human macrophages to produce tumor necrosis factor alpha (TNFα), which is involved in inflammatory signaling and thus the wound healing process. Calcium alginate may also improve the coagulation mechanism in the early stages of wound healing. Studies comparing hydrocolloid dressings with calcium alginate gels have shown that calcium alginate gels stay on the wound longer and have better durability than hydrocolloids. In addition, calcium alginate has the advantages of early use as a haemostatic agent and wound dressing, and its relative lack of toxicity. This makes calcium alginate a potential treatment option that can be used to manage wounds and promote the healing process. Alginate dressings are suitable for moderate to heavily exuding wounds. Alginate is fixed in the wound in the form of fibres, is readily biodegradable and can be removed by saline irrigation. As a result, the granulation tissue is not destroyed when the dressing is changed and there is virtually no pain. This biodegradable convenience is also used to make alginate sutures for surgical wound closure. However, because alginate dressings require moisture to work effectively, they cannot be used on dry wounds or wounds covered by hard, necrotic tissue. This is one of their major disadvantages, as they can cause wound dehydration and delay healing. In addition, the alginate-formed coagulation can also be used as a nanodrug carrier to deliver drugs in vivo for targeted sustained release.
Alginate rhodamine is a material composed of alginate and rhodamine dye. It is widely used in the biomedical field, especially in the development of imaging, drug delivery and biosensors. As mentioned above, alginate has good biocompatibility, biodegradability and low toxicity. Rhodamine is a class of dyes with strong fluorescent properties. Because the dye can emit bright fluorescent signals at specific wavelengths, it is often used in biological imaging. Alginate labeled with rhodamine not only retains the biocompatibility and adjustable physical properties of alginate, but also has the fluorescent properties of rhodamine. Nanodrug carriers composed of this material can provide visual feedback in cells, tissues or in vivo environments, thereby monitoring the distribution and effect of drugs in the body. This is particularly important for the development of drug delivery systems, because researchers can track the release and distribution of drugs in the body by observing fluorescent signals. Existing studies have shown that the viscosity of alginate is usually related to its concentration and molecular weight. Low viscosity alginate means that the material can still form a stable hydrogel at a lower concentration without affecting its biocompatibility. This property gives low-viscosity alginate rhodamine unique advantages in areas such as cell encapsulation, 3D bioprinting, and microfluidic chips. They can be easily injected or sprayed to ensure precise distribution in complex structures or tiny spaces. In addition, the low viscosity property also makes this material easier to combine with other biomaterials or drugs, thereby enhancing its potential for application in tissue engineering or regenerative medicine.
Alternate Names:
Rhodamine-labeled alginate
Rhodamine-conjugated alginate
Rhodamine-modified alginate
Alginate-rhodamine conjugate
Alginate-rhodamine derivative
Rhodamine alginate complex
References:
1. Upadhyay TK, et al. Preparation and characterization of beta-glucan particles containing a payload of nanoembedded rifabutin for enhanced targeted delivery to macrophages. EXCLI J. 2017, 16:210-228.
2. Rastogi P, Kandasubramanian B. Review of alginate-based hydrogel bioprinting for application in tissue engineering. Biofabrication. 2019, 11(4):042001.
Synthesis of silica-alginate nanoparticles and their potential application as pH-responsive drug carriers
J Solgel Sci Technol.
Authors: Fan X, Domszy RC, Hu N, Yang AJ, Yang J, David AE.
Abstract
Composite silica-alginate nanoparticles were prepared via silica sol-gel technique using a water-in-oil microemulsion system. In our system, cyclohexane served as the bulk oil phase into which aqueous solutions of sodium alginate were dispersed as droplets that confined nanoparticle formation after addition of tetraethylorthosilicate (TEOS). Our studies showed that much of the particle growth is completed within the first 24 hours and reaction times up to 120 hours only resulted in an additional 5% increase in particle diameter. Average particle size was found to decrease with increasing water-to-surfactant molar ratio (R) and with increasing cocentration of alginate in the aqueous phase. The potential for drug loading during particle formation was demonstrated using rhodamine B as a model drug. In vitro release studies showed that particles incubated in pH 2.5 phosphate buffer released only about 7% of the drug load in 27 days, while 42% was released in pH 7.5 phosphate buffer over the same period. Analysis of the release profile suggested that rhodamine B was homogeneously distributed throughout the particle and that the drug diffusivity was 40-fold greater in pH 7.5 buffer compared to that at pH 2.5. These results suggest that silica-alginate nanoparticles could be used as a pH-responsive drug carrier for controlled drug release.
Preparation and Properties of Self-Cross-Linking Hydrogels Based on Chitosan Derivatives and Oxidized Sodium Alginate
ACS Omega.
Authors: Yu G, Niu C, Liu J, Wu J, Jin Z, Wang Y, Zhao K.
Abstract
A self-cross-linking and biocompatible hydrogel has wide application potential in the field of tissue engineering. In this work, an easily available, biodegradable, and resilient hydrogel was prepared using a self-cross-linking method. This hydrogel was composed of N-2-hydroxypropyl trimethyl ammonium chloride chitosan (HACC) and oxidized sodium alginate (OSA). A stable and reversible cross-linking network was formed by the Schiff base self-cross-linked and hydrogen bonding. The addition of a shielding agent (NaCl) may weaken the intense electrostatic effect between HACC and OSA and solve the problem of flocculation caused by the rapid formation of ionic bonds, which provided an extended time for the Schiff base self-cross-linked reaction for forming a homogeneous hydrogel. Interestingly, the shortest time for the formation of the HACC/OSA hydrogel was within 74 s and the hydrogel had a uniform porous structure and enhanced mechanical properties. The HACC/OSA hydrogel withstood large compression deformation due to improved elasticity. What's more, this hydrogel possessed favorable swelling property, biodegradation, and water retention. The HACC/OSA hydrogels have great antibacterial properties against Staphylococcus aureus and Escherichia coli and demonstrated good cytocompatibility as well. The HACC/OSA hydrogels have a good sustained release effect on rhodamine (model drug). Thus, the obtained self-cross-linked HACC/OSA hydrogels in this study have potential applications in the field of biomedical carriers.
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