Development of Drug Delivery Systems for Fish Larvae Reared in Aquaculture

Abstract

3SparosLda – CRIA, UniversityofAlgarve, Portugal M marine fish larvae reared in aquaculture hatch withimmaturedigestive and immune systems, being extremely susceptible to diseases.Thus, sub-optimal rearing conditions are often associated with high larval mortalities, leading to high production losses. This work aimed to develop microencapsulated carriersof bioactive compounds to reduce disease susceptibility and increase fish larval survival. For this purpose, spraydrying and emulsification techniqueswere used to produce gelatin, chitosan, carrageenan and alginatemicrocarriers, where twomodel compounds were encapsulated: protein hydrolysateand a vitamins/minerals mixture, both with bioactive properties.Several techniques were used to characterise the carriers’ size, morphology and release profile. In addition, the first prototypes of alginate and carrageenanproduced by emulsification were tested for digestibility in Senegalese sole (Soleasenegalensis) larvae, a species targeted for aquaculture in Southern-European countries.Results showed that spraydrying produced delivery systems of adequate size (2-8 μm) fora subsequent inclusion infish larvae diets.Chitosan was electeda good matrix-forming material for these carriers, allowing40-70% of model drugs to be released according to aninitial controlledreleaseprofile.This is an important featureto prevent saturation of intestinal transporters in fish larvae. Water-in-oil emulsions produced microcarrierswithan adequate size for direct ingestion by fish larvae (50-250 μm). However, results also showed thatalginate and carrageenan carrierswere poorly digestedby sole larvae, suggesting that digestibility and release profile of chitosan and gelatin microcarriers produced by emulsion should be further investigated.