Cancer is a major health issue concerning to all of us. Current treatment options are still limited due to notselective action. Encapsulation is contemplated as an innovative approach to address systemic toxicity and
tumor resistance caused by traditional therapies, while increasing encapsulated compounds bioavailability.
The coating material of capsules strongly determines the success of the system. Since alginate has been proved non-toxic, biocompatible and biodegradable, it is considered a potential vehicle for therapeutic factors encapsulation. Besides, it has the particular ability to form hydrogels, which hold a high-water content and greatly resemble to natural soft tissues. The present review exposes the state-of-the-art and the most sophisticated alginate-based systems for cancer therapy and research. It begins with an overview of alginate hydrogels and the qualities that make them especially suitable for biomedical applications. In the following section, the application of alginate hydrogels as pioneering strategies for cancer treatment is described. Several examples of
alginate-based delivery systems of therapeutic drugs, proteins and nucleic acids are provided. Significant emphasis is placed in both oral delivery systems and colorectal cancer therapy.
Moreover, the role of alginate 3-D scaffolds for both cell culture and delivery is explained. Lastly, other applications of alginate-based hydrogels such as tumor biomarkers immunosensing and fluorescent surgical marker are included.
Alginate is the generic nomenclature that refers to a family of linear
polysaccharides such as alginic acid and alginate salts, composed by
β(1→4) linked β-D-mannuronic acid (M) residues and its C-5 epimer
α-L-guluronic acid (G). These monomers are arranged in a nonregular block-wise pattern consisting of homosequences of consecutive
M or G residues (M- or G-blocks) alternated with G/M heterosequences
(Fig. 2) [42–44]. The composition, molecular weights and hence, material properties of alginate depends on the source of extraction [42–44].
Sources and extraction
Alginates are found in a wide range of brown algae such as Macrocystis pyrifera, Laminaria hyperborea, Laminaria digitate, Laminaria japonica, Durvillaea Antarctica, Ecklonia maxima, Lessonia nigrescens, Sargassum spp. and Ascophyllum nodosum [43,45]. Its molecular weight goes from 32 to 400 kg/mol [43]. Variability is mainly due to the specie and algae age.
Alginate biosynthesis is as well performed by two bacterial genera:
both Pseudomonas and Azotobacter synthesize alginate as an
exopolysaccharide.
In P. aeruginosa, alginate has a vital role in the configuration of biofilms. Besides, Azotobacter employs high G-content alginates as a part of the resistant desiccation structure of cysts .
Generally, bacterial biosynthesis provides high quality alginate with
better characterized structures and properties.
Nowadays, more than 200 types of alginate are commercially available. In spite of the heterogeneous composition, most of themcome from farmed brown seaweeds.
