A review of optical methods for ultrasensitive detection and characterization of nanoparticles in liquid media with a focus on the wide field surface plasmon microscopy

Surfactant-shell lipid nanocapsules (LNCs) are promising skin delivery systems. They are composed of an oily core with a stabilising shell of surfactant and phosphatidylcholine. LNCs’ hydrodynamic diameter can be easily tuned by varying the surfactant content in the formulation. Hydrophilic surfactants incorporated into LNCs have shown toxicity in mammalian cells. To date, the toxicity of all published surfactant-shelled LNCs produced by the the phase inverson temperature (PIT) method has been investigated using hydrophilic surfactants, with no studies examining the impact of incorporating hydrophobic surfactants on LNCs’ in vitro behaviour. Span 80 is a hydrophobic surfactant and has been extensively used in manufacturing various ranges of nanoparticles. The present study formulated Span 80-containing LNCs to evaluate their in vitro behaviour in the B16F10 melanoma cell line. LNC-100-S8 of Kolliphor HS15/Span 80 (65/35 w/w%) and original LNC100-0 LNCs of Kolliphor HS15 with a hydrodynamic diameter of 100 nm were prepared using the PIT method. A salt aggregation test confirmed increased surface hydrophobicity of LNC100-S8 compared to LNC100-0. Cytotoxicity assays demonstrated that LNC100-S8 had a three-fold lower cytotoxicity than LNC100-0 (IC80 = 11757 μg/mL vs 3184 μg/mL). Flow cytometry analysis indicated significantly higher cellular uptake of LNC100-S8 compared to LNC100-0, with 1.52-fold, 1.46-fold, and 1.67-fold increase at 1 h, 3 h, and 24 h, respectively . Mechanistic investigations revealed that LNC100-S8 uptake predominantly occured via phosphoinositide 3-kinase (PI3K)-regulated macropinocytosis and actin-dependent endocytosis, whereas LNC100-0 also utilised Na+/H+ exchanger-mediated macropinocytosis. Furthermore, protein corona analysis demonstrated increased interactions between LNC100-S8 and B16F10-conditioned media proteins, leading to bimodal size distribution and elevated polydispersity index (>0.3), which influenced their endocytic pathways. Overall, Our findings revealed the high promise of our Span 80-containing LNCs as a drug delivery system with enhanced cellular uptake and biocompatibility in B16F10 melanoma cells compared to conventional LNCs composed of Kolliphor HS15 surfactant, highlighting their potential uses in topical delivery to melanoma and other skin diseases.

SARS-CoV-2 can infect cells through endocytic uptake, a process that is targeted by inhibition of lysosomal proteases. However, clinically this approach to treat viral infections has afforded mixed results, with some studies detailing an oral regimen of hydroxychloroquine accompanied by significant off-target toxicities. We rationalized that an organelle-targeted approach will avoid toxicity while increasing the concentration of the drug at the target. Here, we describe a lysosome-targeted, mefloquine-loaded poly(glycerol monostearate-co-ε-caprolactone) nanoparticle (MFQ-NP) for pulmonary delivery via inhalation. Mefloquine is a more effective inhibitor of viral endocytosis than hydroxychloroquine in cellular models of COVID-19. MFQ-NPs are less toxic than molecular mefloquine, are 100–150 nm in diameter, and possess a negative surface charge, which facilitates uptake via endocytosis allowing inhibition of lysosomal proteases. MFQ-NPs inhibit coronavirus infection in mouse MHV-A59 and human OC43 coronavirus model systems and inhibit SARS-CoV-2 WA1 and its Omicron variant in a human lung epithelium model. Organelle-targeted delivery is an effective means to inhibit viral infection.

Indocyanine green (ICG) J-aggregates (IJA) are a unique form of aggregation that exhibits superior properties to monomeric ICG. Despite their higher photoacoustic (PA) signals for imaging and heating stability during photothermal therapy (PTT), they exhibit low stability under a biological milieu. Our group previously proposed a simple procedure for in-situ preparation of IJA into liposomes, accelerating their formation and optical properties. To comprehend their potential applications, we systematically investigated the effect of the lipid bilayer composition on ICG J-aggregation and stability. Moreover, their in vitro compatibility and photothermal toxicity in monolayers and cancer spheroids, besides their in vivo biodistribution and clearance were evaluated. Our findings revealed the importance of high cholesterol and PEG-lipid content and low charged lipids (∼ 5 mol %) in liposomes to promote a high IJA/ICG ratio and, thus, high heating stability. More importantly, IJA-liposomes revealed high biocompatibility in monolayer and cancer spheroids with efficient photothermal toxicity. Finally, IJA-liposomes were cleared from the body without toxicity. Interestingly, IJA-liposomes mainly showed lower affinity to the liver than monomeric ICG, resulting in higher renal clearance. Overall, our biodegradable IJA-liposomes could be an excellent alternative to gold-based agents suitable for PA imaging and cancer PTT.