Advances in nanotechnology for sustainable aquaculture and fisheries

The unique properties of dendrimers, such as their high degree of branching, multivalency, globular architecture and well-defined molecular weight, make them promising new scaffolds for drug delivery. In the past decade, research has increased on the design and synthesis of biocompatible dendrimers and their application to many areas of bioscience including drug delivery, immunology and the development of vaccines, antimicrobials and antivirals. Recent progress has been made in the application of biocompatible dendrimers to cancer treatment, including their use as delivery systems for potent anticancer drugs such as cisplatin and doxorubicin, as well as agents for both boron neutron capture therapy and photodynamic therapy.

There are a variety of both natural and synthetic polymeric systems that have been investigated for the controlled release of proteins. Many of the procedures employed to incorporate proteins into a polymeric matrix can be harsh and often cause denaturation of the active agent. Alginate, a naturally occurring biopolymer extracted from brown algae (kelp), has several unique properties that have enabled it to be used as a matrix for the entrapment and/or delivery of a variety of biological agents. Alginate polymers are a family of linear unbranched polysaccharides which contain varying amounts of 1,4'-linked beta-D-mannuronic acid and alpha-L-guluronic acid residues. The residues may vary widely in composition and sequence and are arranged in a pattern of blocks along the chain. Alginate can be ionically crosslinked by the addition of divalent cations in aqueous solution. The relatively mild gelation process has enabled not only proteins, but cells and DNA to be incorporated into alginate matrices with retention of full biological activity. Furthermore, by selection of the type of alginate and coating agent, the pore size, degradation rate, and ultimately release kinetics can be controlled. Gels of different morphologies can be prepared including large block matrices, large beads (>1 mm in diameter) and microbeads (<0.2 mm in diameter). In situ gelling systems have also been made by the application of alginate to the cornea, or on the surfaces of wounds. Alginate is a bioadhesive polymer which can be advantageous for the site specific delivery to mucosal tissues. All of these properties, in addition to the nonimmunogenicity of alginate, have led to an increased use of this polymer as a protein delivery system. This review will discuss the chemistry of alginate, its gelation mechanisms, and the physical properties of alginate gels. Emphasis will be placed on applications in which biomolecules have been incorporated into and released from alginate systems.