Complex microparticles for delivery of low-molecular weight, water-soluble nutrients and pharmaceuticals to marine fish larvae

Most currently available microparticulate artificial diets for rearing marine suspension feeders, including larval fish, are not effective in retaining low-molecular weight, water-soluble (LMWS) nutrients and other materials [Lopez-Alvarado, J., Langdon, C.J., Teshima, S., Kanazawa, A., 1994. Effects of coating and encapsulation of crystalline amino acids on leaching in larval feeds. Aquaculture 122, 335–346; Baskerville-Bridges, B., Kling, L.J., 2000. Development and evaluation of microparticulate diets for early weaning of Atlantic cod, Gadus morhua, larvae. Aquac. Nutr. 6, 171–182]. Rapid leaching losses occur as a result of high surface-to-volume ratios and the porosity of the matrix or walls of the particles [Langdon, C.J., 2003. Microparticle types for delivery nutrients to marine fish larvae. Aquaculture 227, 259–275]. In order to address this problem of high leakage losses, a novel complex particle type was developed consisting of LMWS incorporated in lipid beads that are then bound, with other nutrients, in a matrix of the water-insoluble protein zein.A spray method for preparing lipid beads was developed to increase the concentration of incorporated core material as well as to reduce losses due to leakage from beads suspended in water. It was possible to prepare lipid spray beads (LSB) that delivered 8.5% of their dry weight as glycine after 1-h suspension in water, resulting in free amino acid concentrations similar to those of commonly used live feeds for fish larvae, such as rotifers and Artemia; however, this delivery efficiency was reduced to 1.2% glycine for complex particles made up of 30% w/w glycine-containing LSB and other dietary nutrients. Further experiments are required to determine if complex particles can replace living feeds for the early larval stages of marine fish species.