Microalgae harvesting using flocculation and dissolved air flotation: Selecting the right vessel for lab-scale experiments.

Flocculation combined with dissolved air flotation (DAF) is a promising technology for harvesting microalgae; therefore, optimisation of flocculant-DAF operating conditions are frequently explored in laboratory experiments. DAF systems have jars of differing volumes, height to diameter ratios, shapes and materials used to manufacture the jars; thus, the harvesting efficiency (η) may differ between these jars. The aim was to systematically compare η between different types of benchtop DAF jars. Evaluation of 30 different types of DAF jars revealed that η was not influenced by the volume of the jars, but was impacted by the height to diameter ratio, with optimal η at a ratio ranging between 1.6 and 2.05. There was no difference in η between cylindrical and cuboid jars, but jars made of hydrophobic (polypropylene) plastic resulted in a lower η. Overall, these results are useful to guide the design of lab-scale DAF microalgae harvesting experiments.

Polyethylene glycol-drug ester conjugates for prolonged retention of small inhaled drugs in the lung.

Typically, inhaled drugs are rapidly absorbed into the bloodstream, which results in systemic side effects and a brief residence time in the lungs. PEGylation was evaluated as a novel strategy for prolonging the retention of small inhaled molecules in the pulmonary tissue. Hydrolysable ester conjugates of PEG1000, PEG2000, 2000, PEG3400 and prednisolone, a model drug cleared from the lungs within a few minutes, were synthesised and thoroughly characterised. The conjugates were stable in buffers with hydrolysis half-lives ranging from 1h to 70 h, depending on the pH and level of substitution. With the exception of PEG3400-prednisolone, conjugates did not induce a significant lactate dehydrogenase (LDH) release from Calu-3 cells after a 20 h exposure. Following nebulisation to isolated perfused rat lungs (IPRL), the PEG2000 and mPEG2000 conjugates reduced the maximum prednisolone concentration in the perfusate (Cmax) by 3.0 and 2.2 fold, respectively. Moreover, while prednisolone was undetectable in the perfusion solution beyond 20 min when the free drug was administered, prednisolone concentrations were still quantifiable after 40 min following delivery of the conjugates. This study is the first to demonstrate hydrolysable PEG drug ester conjugates are a promising approach for optimising the pharmacokinetic profile of small drugs delivered by inhalation.