Inter-nanocarrier and nanocarrier-to-cell transfer assays demonstrate the risk of an immediate unloading of dye from labeled lipid nanocapsules

Incorporation of poly(γ-glutamic acid) in lipid nanoparticles for enhanced mRNA delivery efficiency in vitro and in vivo

Messenger RNA (mRNA)-based therapy shows immense potential for broad biomedical applications. However, the development of safe and efficacious mRNA delivery vectors remains challenging due to delivery barriers and inefficient intracellular payload release. Herein, we presented a simple strategy to boost the mRNA intracellular release by incorporation of anionic poly(γ-glutamic acid) (PGA) into an ionizable lipid-based LNP/mRNA. We systematically investigated the impact of PGA incorporation on mRNA transfection both in vitro and in vivo. The molecular weights and formulation ratios of PGA greatly affected the transfection efficacy of LNP/mRNA. From in vitro study, the optimized LNP/mRNA/PGA was formulated by incorporation of PGA with the molecular weight of 80 kDa or 200 kDa and the charge ratio (N/P/C) of 25/1/1. The optimized formulation achieved around 3-fold mRNA expression in HeLa cells compared to the bare LNP/mRNA. The intracellular releasing study using specific DNA probe revealed that this enhancement of transfection efficacy was attributed to the elevated mRNA release into cytoplasm. Moreover, the optimized LNP/mRNA/PGA achieved up to 5-fold or 3-fold increase of luciferase mRNA expression in vivo after being injected into mice systematically or intramuscularly, respectively. In addition, the incorporation of PGA did not significantly alter the biodistribution profile of the complexes on both organ and cellular levels. Therefore, our work provides a simple strategy to boost mRNA delivery, which holds great promise to improve the efficacy of mRNA therapeutics for various biomedical applications. STATEMENT OF SIGNIFICANCE: The process of designing and screening potent mRNA carriers is complicated and time-consuming, while the efficacy is not always satisfying due to the delivery barriers and inefficient mRNA release. This work presented an alternative strategy to boost the mRNA delivery efficacy by incorporating an anionic natural polymer poly(γ-glutamic acid) (PGA) into LNP/mRNA complexes. The optimized LNP/mRNA/PGA achieved up to 3-fold and 5-fold increase in transfection efficacy in vitro and in vivo, respectively. Intracellular releasing analysis revealed that the enhancement of transfection efficacy was mainly attributed to the elevated intracellular release of mRNA. In addition, the incorporation of PGA did not alter the biodistribution or the biosafety profile of the complexes. These findings indicate that PGA incorporation is a promising strategy to improve the efficacy of mRNA therapeutics.

Dual-Labelled Nanoparticles Inform on the Stability of Fluorescent Labels In Vivo

Fluorescent labelling is commonly used to monitor the biodistribution of nanomedicines. However, meaningful interpretation of the results requires that the fluorescent label remains attached to the nanomedicine. In this work, we explore the stability of three fluorophores (BODIPY650, Cyanine 5 and AZ647) attached to polymeric hydrophobic biodegradable anchors. Using dual-labelled poly(ethylene glycol)-b-poly(lactic acid) (PEG-PLA) nanoparticles that are both radioactive and fluorescent, we investigated how the properties of the fluorophores impact the stability of the labelling in vitro and in vivo. Results suggest that the more hydrophilic dye (AZ647) is released faster from nanoparticles, and that this instability results in misinterpretation of in vivo data. While hydrophobic dyes are likely more suitable to track nanoparticles in biological environments, quenching of the fluorescence inside the nanoparticles can also introduce artefacts. Altogether, this work raises awareness about the importance of stable labelling methods when investigating the biological fate of nanomedicines.

Fluorescently Labeled PLGA Nanoparticles for Visualization In Vitro and In Vivo: The Importance of Dye Properties

Fluorescently labeled nanoparticles are widely used for evaluating their distribution in the biological environment. However, dye leakage can lead to misinterpretations of the nanoparticles' biodistribution. To better understand the interactions of dyes and nanoparticles and their biological environment, we explored PLGA nanoparticles labeled with four widely used dyes encapsulated (coumarin 6, rhodamine 123, DiI) or bound covalently to the polymer (Cy5.5.). The DiI label was stable in both aqueous and lipophilic environments, whereas the quick release of coumarin 6 was observed in model media containing albumin (42%) or liposomes (62%), which could be explained by the different affinity of these dyes to the polymer and lipophilic structures and which we also confirmed by computational modeling (log PDPPC/PLGA: DiI-2.3, Cou6-0.7). The importance of these factors was demonstrated by in vivo neuroimaging (ICON) of the rat retina using double-labeled Cy5.5/Cou6-nanoparticles: encapsulated Cou6 quickly leaked into the tissue, whereas the stably bound Cy.5.5 label remained associated with the vessels. This observation is a good example of the possible misinterpretation of imaging results because the coumarin 6 distribution creates the impression that nanoparticles effectively crossed the blood-retina barrier, whereas in fact no signal from the core material was found beyond the blood vessels.

Halochromic Polymer Nanosensors for Simple Visual Detection of Local pH in Coatings

Replacing metallic structures before critical damage is beneficial for safety and for saving energy and resources. One simple approach consists in visually monitoring the early stage of corrosion, and related change of pH, of coated metals. We prepare smart nanoparticle additives for coatings which act as a pH sensor. The nanoparticles are formed with a terpolymer containing two dyes as side chains, acting as donor and acceptor for a FRET process. Real time monitoring of the extent of localized corrosion on metallic structures is then carried out with a smartphone camera. Colored pH mapping can be then manually retrieved by an operator or automatically recorded by a surveillance camera.

Characterization of Biological Material Adsorption to the Surface of Nanoparticles without a Prior Separation Step: a Case Study of Glioblastoma-Targeting Peptide and Lipid Nanocapsules

Purpose

Current preclinical therapeutic strategies involving nanomedicine require increasingly sophisticated nanosystems and the characterization of the complexity of such nanoassemblies is becoming a major issue. Accurate characterization is often the factor that can accelerate the translational approaches of nanomedicines and their pharmaceutical development to reach the clinic faster. We conducted a case study involving the adsorption of the NFL-TBS.40–63 (NFL) peptide (derived from neurofilaments) to the surface of lipid nanocapsules (LNCs) (a combined nanosystem used to target glioblastoma cells) to develop an analytical approach combining the separation and the quantification in a single step, leading to the characterization of the proportion of free peptide and thus the proportion of peptide adsorbed to the lipid nanocapsule surface.

Methods

LNC suspensions, NFL peptide solution and LNC/NFL peptide mixtures were characterized using a Size-Exclusion Chromatography method (with a chromatographic apparatus). In addition, this method was compared to centrifugal-filtration devices, currently used in literature for this case study.

Results

Combining the steps for separation and characterization in one single sequence improved the accuracy and robustness of the data and led to reproducible results. Moreover the data deviation observed for the centrifugal-filtration devices demonstrated the limits for this increasingly used characterization approach, explained by the poor separation quality and highlighting the importance for the method optimization. The high potential of the technique was shown, proving that H-bond and/or electrostatic interactions mediate adsorption of the NFL peptide to the surface of LNCs.

Conclusions

Used only as a characterization tool, the process using chromatographic apparatus is less time and solvent consuming than classical Size-Exclusion Chromatography columns only used for separation. It could be a promising tool for the scientific community for characterizing the interactions of other combinations of nanosystems and active biological agents.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-021-03034-8.

Recent advances in iron oxide nanoparticles for brain cancer theranostics: from in vitro to clinical applications

Introduction: Today, the development of multifunctional nanoplatforms is more seriously considered in the field of cancer theranostics.Areas covered: In this respect, nanoparticles provide several advantages over the routine, conventional diagnostic methods, and treatments. Due to the expedient properties of iron oxide nanoparticles, such as being readily modified, great payload potential, intrinsic magnetic qualification, considerable biocompatibility, and overwhelming response to targeting strategies, these nanoparticles can be considered good candidates for application as diagnostic contrast agents and drug/gene delivery vehicles, while also being incorporated into hyperthermia-based approaches. Interestingly, these agents are detectable with routine imaging modalities such as magnetic resonance imaging.Expert opinion: Therefore, combining the traditional diagnostics and therapies with nanotechnological approaches may leave a positive impact on the survival rate of patients with cancer. This review summarizes the application of magnetic iron oxide nanoparticles in both in vitro and in vivo models of brain tumors.

Cyclosporine Lipid Nanocapsules as Thermoresponsive Gel for Dry Eye Management: Promising Corneal Mucoadhesion, Biodistribution and Preclinical Efficacy in Rabbits

An ophthalmic cyclosporine (CsA) formulation based on Lipid nanocapsules (LNC) was developed for dry eye management, aiming to provide targeting to ocular tissues with long-term drug levels and maximum tolerability. CsA-LNC were of small particle size (41.9 ± 4.0 nm), narrow size distribution (PdI ≤ 0.1), and high entrapment efficiency (above 98%). Chitosan (C) was added to impart positive charge. CsA-LNC were prepared as in-situ gels using poloxamer 407 (P). Ex vivo mucoadhesive strength was evaluated using bovine cornea, while in vivo corneal biodistribution (using fluorescent DiI), efficacy in dry eye using Schirmer tear test (STT), and ocular irritation using Draize test were studied in rabbits compared to marketed ophthalmic CsA nanoemulsion (CsA-NE) and CsA in castor oil. LNC incorporation in in-situ gels resulted in an increase in mucoadhesion, and stronger fluorescence in corneal layers seen by confocal microscopy, compared to the other tested formulations. Rate of recovery (days required to restore corneal baseline hydration level) assessed over 10 days, showed that CsA-LNC formulations produced complete recovery by day 7 comparable to CsA-NE. No Ocular irritation was observed by visual and histopathological examination. Based on data generated, CsA-LNC-CP in-situ gel proved to be a promising effective nonirritant CsA ophthalmic formulation for dry eye management.

Dye-Loaded Nanoemulsions: Biomimetic Fluorescent Nanocarriers for Bioimaging and Nanomedicine

Lipid nanoemulsions (NEs), owing to their controllable size (20 to 500 nm), stability and biocompatibility, are now frequently used in various fields, such as food, cosmetics, pharmaceuticals, drug delivery, and even as nanoreactors for chemical synthesis. Moreover, being composed of components generally recognized as safe (GRAS), they can be considered as "green" nanoparticles that mimic closely lipoproteins and intracellular lipid droplets. Therefore, they attracted attention as carriers of drugs and fluorescent dyes for both bioimaging and studying the fate of nanoemulsions in cells and small animals. In this review, the composition of dye-loaded NEs, methods for their preparation, and emerging biological applications are described. The design of bright fluorescent NEs with high dye loading and minimal aggregation-caused quenching (ACQ) is focused on. Common issues including dye leakage and NEs stability are discussed, highlighting advanced techniques for their characterization, such as Förster resonance energy transfer (FRET) and fluorescence correlation spectroscopy (FCS). Attempts to functionalize NEs surface are also discussed. Thereafter, biological applications for bioimaging and single-particle tracking in cells and small animals as well as biomedical applications for photodynamic therapy are described. Finally, challenges and future perspectives of fluorescent NEs are discussed.

Facile Hydrophobication of Glutathione-Protected Gold Nanoclusters and Encapsulation into Poly(lactide-co-glycolide) Nanocarriers

We report a simple surface functionalization of glutathione-capped gold nanoclusters by hydrophobic ion pairing with alkylamine followed by a complete phase transfer to various organic solvents with maintained colloidal stability and photoluminescence properties. The described surface hydrophobication enables efficient encapsulation of gold nanoclusters into PLGA nanocarriers allowing their visualization inside cultured cells using confocal fluorescent microscopy. The simplicity and efficiency of the described protocols should extend the biomedical applications of these metallic nanoclusters as a fluorescent platform to label hydrophobic polymeric nanocarriers beyond conventional organic dyes.

Cannabidiol Enhances the Passage of Lipid Nanocapsules across the Blood-Brain Barrier Both in Vitro and in Vivo

Diseases affecting the central nervous system (CNS) should be regarded as a major health challenge due to the current lack of effective treatments given the hindrance to brain drug delivery imposed by the blood-brain barrier (BBB). Since efficient brain drug delivery should not solely rely on passive targeting, active targeting of nanomedicines into the CNS is being explored. The present study is devoted to the development of lipid nanocapsules (LNCs) decorated with nonpsychotropic cannabinoids as pioneering nonimmunogenic brain-targeting molecules and to the evaluation of their brain-targeting ability both in vitro and in vivo. Noticeably, both the permeability experiments across the hCMEC/D3 cell-based in vitro BBB model and the biodistribution experiments in mice consistently demonstrated that the highest brain-targeting ability was achieved with the smallest-sized cannabinoid-decorated LNCs. Importantly, the enhancement in brain targeting achieved with the conjugation of cannabidiol to LNCs outperformed by 6-fold the enhancement observed for the G-Technology (the main brain active strategy that has already entered clinical trials for the treatment of CNS diseases). As the transport efficiency across the BBB certainly determines the efficacy of the treatments for brain disorders, small cannabinoid-decorated LNCs represent auspicious platforms for the design and development of novel therapies for CNS diseases.

BODIPY-loaded polymer nanoparticles: chemical structure of cargo defines leakage from nanocarrier in living cells

Hydrophobicity of a fluorescent cargo loaded into PLGA nanoparticles is crucial for minimizing its leakage in biological media.

Dissociation of fluorescently labeled lipids from liposomes in biological environments challenges the interpretation of uptake studies

Within nanomedicine, liposomes are investigated for their ability to deliver drug cargoes specifically into subcellular compartments of target cells. Such studies are often based on flow cytometry or microscopy, where researchers rely on fluorescently labeled lipids (FLLs) incorporated into the liposomal membrane to determine the localization of the liposomes within cells. These studies assume that the FLLs stay embedded in the liposomal membrane throughout the duration of the experiment. Here, we used size exclusion chromatography (SEC) to investigate the validity of this assumption by quantitatively determining the propensity of various widely used FLLs to dissociate from liposomes during incubation in human plasma. For certain commonly used off-the-shelf FLLs, up to 75% of the dye dissociated from the liposomes, while others dissociated less than 10%. To investigate the implications of this finding, we measured the peripheral blood leukocyte uptake of liposomes formulated with different FLLs using flow cytometry, and observed a significant difference in uptake correlating with the FLL's dissociation tendencies. Consequently, the choice of FLL can dramatically influence the conclusions drawn from liposome uptake and localization studies due to uptake of dissociated FLLs. The varying dissociation propensities for the FLLs were not reflected when incubating in buffer, showing that non-biological environments are unsuitable to mimic liposomal stability in a drug delivery context. Overall, our findings suggest that it is crucial for researchers to evaluate the stability of their FLL-labeled liposomes in biological environments, and the simplicity of the SEC assay put forward here makes it very applicable for the purpose.

Lipid nanocapsules maintain full integrity after crossing a human intestinal epithelium model

Lipid nanocapsules (LNCs) have demonstrated great potential for the oral delivery of drugs having very limited oral bioavailability (BCS class II, III and IV molecules). It has been shown previously that orally-administered LNCs can permeate through mucus, increase drug absorption by the epithelial tissue, and finally, increase drug bioavailability. However, even if transport mechanisms through mucus and the intestinal barrier have already been clarified, the preservation of particle integrity is still not known. The aim of the present work is to study in vitro the fate of LNCs after their transportation across an intestinal epithelium model (Caco-2 cell model). For this, two complementary techniques were employed: Förster Resonance Energy Transfer (FRET) and Nanoparticle Tracking Analysis (NTA). Results showed, after 2h, the presence of nanoparticles in the basolateral side of the cell layer and a measurable FRET signal. This provides very good evidence for the transcellular intact crossing of the nanocarriers.