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Cryptococcus neoformans is a yeast-like fungus that can cause the life-threatening disease cryptococcal meningitis. Numerous reports have shown increased resistance of this fungus against antifungal treatments, such as fluconazole (Fluc), contributing to an 80% global mortality rate. This work presents a novel approach to improve the delivery of the antifungal agent Fluc and increase the drug's targetability and availability at the infection site. Exploiting the acidic environment surrounding a C. neoformans infected site, we have developed pHsensitive lipid nanoparticles (LNP) encapsulating Fluc to inhibit the growth of resistant C. neoformans. The LNP-Fluc delivery system consists of a neutral lipid monoolein (MO) and a novel synthetic ionizable lipid 2-morpholinoethyl oleate (O2ME). At neutral pH, because of the presence of O2ME, the nanoparticles are neutral and exhibit a liquid crystalline hexagonal nanostructure (hexosomes). At an acidic pH, they are positively charged with a cubic nanostructure (cubosomes), which facilitates the interaction with the negatively charged fungal cell wall. This interaction results in the MIC50 and MIC90 values of the LNP-Fluc being significantly lower than that of the free-Fluc control. Confocal laser scanning microscopy and scanning electron microscopy further support the MIC values, showing fungal cells exposed to LNP-Fluc at acidic pH were heavily distorted, demonstrating efflux of cytoplasmic molecules. In contrast, fungal cells exposed to Fluc alone showed cell walls mostly intact. This current study represents a significant advancement in delivering targeted antifungal therapy to combat fungal antimicrobial resistance.

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pH-responsive nanoparticles enable the selective delivery of a chemotherapeutic agent to tumours while reducing adverse effects. Herein we synthesised four novel aminolipids and developed pH-responsive nanostructured lipid nanoparticles (LNP), which exhibited a slow-releasing hexagonal structure (H2) at physiological pH and quick release bicontinuous cubic phase (Q2) at the acidic tumour pH. The nanoparticles were used to encapsulate and control the release of the chemotherapeutic agent SN-38. High-throughput formulation techniques were employed to fabricate LNP by mixing various amounts of aminolipid with monoolein (MO). The effect of aminolipids on MO self-assembled structures was studied using small-angle X-ray scattering (SAXS) at various pH values. Out of the four studied aminolipid-MO LNP systems, the nanoparticles containing N-(Pyridin-4-ylmethyl) oleamide (OAPy-4) or N-(2(piperidin-1yl)ethyl) oleamide (OAPi-1) exhibited a pH-induced H2 to Q2 phase transition in a tumour-relevant pH range (pH 5.5–7.0). SN-38 is 1000 times more efficacious than the commercially available prodrug irinotecan. However, low solubility in water and instability at physiological pH makes it unsuitable for clinical use. SN-38 was loaded into LNP containing MO and aminolipid OAPy-4. The drug loading and entrapment efficiency were determined, and the results indicated that the aqueous solubility of SN-38 loaded in LNP dispersions was ~100 times higher compared to the solubility of the pure drug in aqueous solution. Furthermore, we demonstrated that the in vitro SN-38 release rate from LNPs was faster at lower pH (pH 5) than at neutral pH. Therefore, pH-responsive LNPs developed in this study can potentially be employed in delivering and controlling the release of the potent drug SN-38 to tumour sites.

Production of large-scale batches is one of the bottlenecks in nanoscience translation, and there is a significant gap between academic and industrial production settings. There is a great need and urgency to develop methods that can easily and quickly scale up nanomaterial laboratory production processes at a large scale. In this study, we report for the first time a fast and easily scalable methodology for the fabrication of lipid-based liquid-crystal (LLC) nanoparticles. We have shown that large volume solutions of cubosomes, liposomes, and hexosomes can be produced (500 mL at 60 mg/mL lipid concentration) in a matter of minutes without the need for any cosolvents. Straightforward synthesis from 5 to 500 mL has been exemplified using resonant acoustic mixing to produce these LLC nanoparticles. The technique is amenable to various container types and may eliminate the need to use cosolvents for the production of such materials due to the excellent mixing potential. We have found that when compared to traditional sonication-based methods, the use of resonant acoustic mixing allows for large-scale synthesis of nanoparticle solutions and the formation of LLC nanoparticles of desirable sizes. We believe this new technique will facilitate the development of lyotropic mesophase materials and new methodologies for the fabrication of nanoparticles. The technique will have a significant impact in shaping the future of nanoscience, providing a rapid and efficient mixing/fabrication platform for a range of materials from cosmetics to therapeutics to vaccines.