Besides their best-known uses in the food and fermentation industry, yeasts have also found application as microcapsules. In the encapsulation process, exogenous and most typically hydrophobic compounds diffuse and end up being passively entrapped in the cell body, and can be released upon application of appropriate stimuli. Yeast cells can be employed either living or dead, intact, permeabilized, or even emptied of all their original cytoplasmic contents. The main selling points of this set of encapsulation technologies, which to date has predominantly targeted food and—to a lesser extent—pharmaceutical applications, are the low cost, biodegradability and biocompatibility of the capsules, coupled to their sustainable origin (e.g., spent yeast from brewing). This review aims to provide a broad overview of the different kinds of yeast-based microcapsules and of the main physico-chemical characteristics that control the encapsulation process and its efficiency.

Introduction: Ischaemia-reperfusion injury (IRI) results in the pathophysiological generation of reactive oxygen species (ROS) with concurrent activation of the complement cascade. This manifests as delayed graft function, which has a significant impact on the longevity of the graft. We aimed to evaluate if ROS scavenging nanoparticles can be used to mitigate IRI related injury during normothermic machine perfusion (NMP). Methods: A randomised, two-stage, preclinical trial was used to assess the impact of poly(propylene sulfide) (polysulfide) nanoparticles (PPS-NPs) on parameters associated with IRI in a renal NMP system (experiment 1, n=6 vs 6). Paired porcine kidneys were randomised to receive either an NP-preservation flush followed by 6 hours of NMP with NP-perfusate, or control preservation flush and standard NMP. Following this, an allogeneic transplant- reperfusion model was used to evaluate if treatment with PPS-NPs improved renal haemodynamics post-transplantation (experiment 2, n=6 vs 6). Kidneys were perfused for 3 hours with or without NP, before being reperfused on a circuit primed with matched blood from genetically different donor pigs for 6 hours, without immunosuppression. Results: In experiment 1, all kidneys perfused well for 6 hours with physiological renal haemodynamics and biochemistry. Kidneys perfused with PPS-NPs had improved regional tissue perfusion on infra-red imaging. In experiment 2, renal haemodynamics were significantly improved during allogeneic reperfusion (post-transplant) after treatment with NP. Complement activation remained significantly lower in treated kidneys with a diminished TNF-a response. This translated into an improvement in tissue integrity. Conclusion: IRI was ameliorated following treatment with NPs during preservation and NMP. This was evidenced by an improvement in renal haemodynamics and diminished inflammatory markers upon reperfusion with allogeneic blood.