Abstract

Background: Algae are widely used for their beneficial properties by food, cosmetic and nutraceutical industry. For nutraceutical and cosmetic (e.g. oral and dermal) application, solubility is a key parameter. Algal extracts are available in sticky and completely dried form and in both cases it is difficult to formulate them due to solubility challenges. Therefore, attempts were made to produce stable algal nanosuspensions. A nano algal suspension could increase the biological activity (due to increased saturation solubility and higher dissolution velocity) and lead to better penetration or absorption profile.

Methods: Dried algae products (N. oculata and Chaetoceros) were obtained from biotechnological cultivation. The algae were dispersed in Tween 80 or in Poloxamer 188 solutions and passed through a piston-gap high pressure homogenizer to produce nano algal suspensions. Production parameters like, number of homogenisation cycles, pressure etc, were optimised. Nanosuspensions were evaluated for particle size, zeta potential and crystallinity. Furthermore, nanosuspensions were converted to solid product using lyophilisation and extrusion-spheronisation technique.

Results: A minimum size of about 226 nm could be achieved after 10 cycles at 1,500 bar. The aqueous nanosuspensions showed highest, but still insufficient stability at refrigeration (4 months data), decreasing stability with increasing temperature, especially at 50°C in the stress storage test and during autoclaving at 121°C. Preservation with Euxyl PE 9010 further decreased the physical stability of the aqueous algae nanosuspensions. Algae as natural material undergoes chemical degradation when in contact with water. For long-term preservation of the size and for chemical stabilization, the algae nanosuspensions were lyophilized. The algae nanoparticles re-dispersed well in water when using trehalose as cryoprotectant. The lyophilizate can be filled in capsules. Pellets were produced using the nanosuspensions as granulation fluid, filled in gelatine capsules for nutraceutical delivery.

Conclusion: Nano-algal suspensions open new perspective for algae products with enhanced bioavailability and penetration profile. The produced nanosuspensions can be used for dermal, nutraceutical or cosmetics purposes.

Keywords: Algae, N. oculata, Chaetoceros, nanocrystals, dermal application, oral delivery, nutraceutical, nanonisation, nanosupensions.

Graphical Abstract