Targeted nanoliposomes for precision rheumatoid arthritis therapy: a review on mechanisms and in vivo potential

Rheumatoid arthritis (RA) is an inflammatory immune-triggered disease that causes synovitis, cartilage degradation, and joint injury. In nanotechnology, conventional liposomes were extensively investigated for RA. However, they frequently undergo rapid clearance, reducing circulation time and therapeutic efficacy. Additionally, their stability in the bloodstream is often compromised, resulting in premature drug release. The current review explores the potential of targeted liposomal-based nanosystems in the treatment of RA. It highlights the pathophysiology of RA, explores selective targeting sites, and elucidates diverse mechanisms of novel liposomal types and their applications. Furthermore, the targeting strategies of pH-sensitive, flexible, surface-modified, PEGylated, acoustic, ROS-mediated, and biofunctionalized liposomes are addressed. Targeted nanoliposomes showed potential in precisely delivering drugs to CD44, SR-A, FR-β, FLS, and toll-like receptors through the high affinity of ligands. In vitro studies interpreted stable release profiles and improved stability. Ex vivo studies on skin demonstrated that ultradeformable and glycerol-conjugated liposomes enhanced drug penetrability. In vivo experiments for liposomal types in the arthritis rat model depicted remarkable efficacy in reducing joint swelling, pro-inflammatory cytokines, and synovial hyperplasia. In conclusion, these targeted liposomes represented a significant leap forward in drug delivery, offering effective therapeutic options for RA. In the future, integrating these advanced liposomes with artificial intelligence, immunotherapy, and precision medicine holds great promise.

Protein corona formed on lipid nanoparticles compromises delivery efficiency of mRNA cargo

Lipid nanoparticles (LNPs) are the most clinically advanced nonviral RNA-delivery vehicles, though challenges remain in fully understanding how LNPs interact with biological systems. In vivo , proteins form an associated corona on LNPs that redefines their physicochemical properties and influences delivery outcomes. Despite its importance, the LNP protein corona is challenging to study owing to the technical difficulty of selectively recovering soft nanoparticles from biological samples. Herein, we developed a quantitative, label-free mass spectrometry-based proteomics approach to characterize the protein corona on LNPs. Critically, this protein corona isolation workflow avoids artifacts introduced by the presence of endogenous nanoparticles in human biofluids. We applied continuous density gradient ultracentrifugation for protein-LNP complex isolation, with mass spectrometry for protein identification normalized to protein composition in the biofluid alone. With this approach, we quantify proteins consistently enriched in the LNP corona including vitronectin, C-reactive protein, and alpha-2-macroglobulin. We explore the impact of these corona proteins on cell uptake and mRNA expression in HepG2 human liver cells, and find that, surprisingly, increased levels of cell uptake do not correlate with increased mRNA expression in part likely due to protein corona-induced lysosomal trafficking of LNPs. Our results underscore the need to consider the protein corona in the design of LNP-based therapeutics.

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Effect of Lipid Nanoparticle Physico-Chemical Properties and Composition on Their Interaction with the Immune System

Lipid nanoparticles (LNPs) have shown promise as a delivery system for nucleic acid-based therapeutics, including DNA, siRNA, and mRNA vaccines. The immune system plays a critical role in the response to these nanocarriers, with innate immune cells initiating an early response and adaptive immune cells mediating a more specific reaction, sometimes leading to potential adverse effects. Recent studies have shown that the innate immune response to LNPs is mediated by Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs), which recognize the lipid components of the nanoparticles. This recognition can trigger the activation of inflammatory pathways and the production of cytokines and chemokines, leading to potential adverse effects such as fever, inflammation, and pain at the injection site. On the other hand, the adaptive immune response to LNPs appears to be primarily directed against the protein encoded by the mRNA cargo, with little evidence of an ongoing adaptive immune response to the components of the LNP itself. Understanding the relationship between LNPs and the immune system is critical for the development of safe and effective nucleic acid-based delivery systems. In fact, targeting the immune system is essential to develop effective vaccines, as well as therapies against cancer or infections. There is a lack of research in the literature that has systematically studied the factors that influence the interaction between LNPs and the immune system and further research is needed to better elucidate the mechanisms underlying the immune response to LNPs. In this review, we discuss LNPs' composition, physico-chemical properties, such as size, shape, and surface charge, and the protein corona formation which can affect the reactivity of the immune system, thus providing a guide for the research on new formulations that could gain a favorable efficacy/safety profile.

Breaking the final barrier: Evolution of cationic and ionizable lipid structure in lipid nanoparticles to escape the endosome

In the past decade, nucleic acid therapies have seen a boon in development and clinical translation largely due to advances in nanotechnology that have enabled their safe and targeted delivery. Nanoparticles can protect nucleic acids from degradation by serum enzymes and can facilitate entry into cells. Still, achieving endosomal escape to allow nucleic acids to enter the cytoplasm has remained a significant barrier, where less than 5% of nanoparticles within the endo-lysosomal pathway are able to transfer their cargo to the cytosol. Lipid-based drug delivery vehicles, particularly lipid nanoparticles (LNPs), have been optimized to achieve potent endosomal escape, and thus have been the vector of choice in the clinic as demonstrated by their utilization in the COVID-19 mRNA vaccines. The success of LNPs is in large part due to the rational design of lipids that can specifically overcome endosomal barriers. In this review, we chart the evolution of lipid structure from cationic lipids to ionizable lipids, focusing on structure-function relationships, with a focus on how they relate to endosomal escape. Additionally, we examine recent advancements in ionizable lipid structure as well as discuss the future of lipid design.

Targeting Ligand Independent Tropism of siRNA-LNP by Small Molecules for Directed Therapy of Liver or Myeloid Immune Cells

Hepatic clearance of lipid nanoparticles (LNP) with encapsulated nucleic acids restricts their therapeutic applicability. Therefore, tools for regulating hepatic clearance are of high interest for nucleic acid delivery. To this end, this work employs wild-type (WT) and low-density lipoprotein receptor (Ldlr)-/- mice pretreated with either a leukotriene B4 receptor inhibitor (BLT1i) or a high-density lipoprotein receptor inhibitor (HDLRi) prior to the injection of siRNA-LNP. This work is able to demonstrate significantly increased hepatic uptake of siRNA-LNP by the BLT1i in Ldlr-/- mice by in vivo imaging and discover an induction of specific uptake-related proteins. Irrespective of the inhibitors and Ldlr deficiency, the siRNA-LNP induced RNA-binding and transport-related proteins in liver, including haptoglobin (HP) that is also identified as most upregulated serum protein. This work observes a downregulation of proteins functioning in hepatic detoxification and of serum opsonins. Most strikingly, the HDLRi reduces hepatic uptake and increases siRNA accumulation in spleen and myeloid immune cells of blood and liver. RNA sequencing demonstrates leukocyte recruitment by the siRNA-LNP and the HDLRi through induction of chemokine ligands in liver tissue. The data provide insights into key mechanisms of siRNA-LNP biodistribution and indicate that the HDLRi has potential for extrahepatic and leukocyte targeting.

Influence of ionizable lipid tail length on lipid nanoparticle delivery of mRNA of varying length

RNA-based therapeutics have gained traction for the prevention and treatment of a variety of diseases. However, their fragility and immunogenicity necessitate a drug carrier. Lipid nanoparticles (LNPs) have emerged as the predominant delivery vehicle for RNA therapeutics. An important component of LNPs is the ionizable lipid (IL), which is protonated in the acidic environment of the endosome, prompting cargo release into the cytosol. Currently, there is growing evidence that the structure of IL lipid tails significantly impacts the efficacy of LNP-mediated mRNA translation. Here, we optimized IL tail length for LNP-mediated delivery of three different mRNA cargos. Using C12-200, a gold standard IL, as a model, we designed a library of ILs with varying tail lengths and evaluated their potency in vivo. We demonstrated that small changes in lipophilicity can drastically increase or decrease mRNA translation. We identified that LNPs formulated with firefly luciferase mRNA (1929 base pairs) and C10-200, an IL with shorter tail lengths than C12-200, enhance liver transfection by over 10-fold. Furthermore, different IL tail lengths were found to be ideal for transfection of LNPs encapsulating mRNA cargos of varying sizes. LNPs formulated with erythropoietin (EPO), responsible for stimulating red blood cell production, mRNA (858 base pairs), and the C13-200 IL led to EPO translation at levels similar to the C12-200 LNP. The LNPs formulated with Cas9 mRNA (4521 base pairs) and the C9-200 IL induced over three times the quantity of indels compared with the C12-200 LNP. Our findings suggest that shorter IL tails may lead to higher transfection of LNPs encapsulating larger mRNAs, and that longer IL tails may be more efficacious for delivering smaller mRNA cargos. We envision that the results of this project can be utilized as future design criteria for the next generation of LNP delivery systems for RNA therapeutics.

Artificial protein coronas: directing nanoparticles to targets

The protein corona surrounding nanoparticles (NPs) offers exciting possibilities for targeted drug delivery. However, realizing this potential requires direct evidence of corona-receptor interactions in vivo; a challenge hampered by the limitations of in vitro settings. This opinion proposes that utilizing engineered protein coronas can address this challenge. Artificial coronas made of selected plasma proteins retain their properties in vivo, enabling manipulation for specific receptor targeting. To directly assess corona-receptor interactions mimicking in vivo complexity, we propose testing artificial coronas with recently adapted quartz crystal microbalance (QCM) setups whose current limitations and potential advancements are critically discussed. Finally, the opinion proposes future experiments to decipher corona-receptor interactions and unlock the full potential of the protein corona for NP-based drug delivery.

Looking back, moving forward: protein corona of lipid nanoparticles

Lipid nanoparticles (LNPs) are commonly employed for drug delivery owing to their considerable drug-loading capacity, low toxicity, and excellent biocompatibility. Nevertheless, the formation of protein corona (PC) on their surfaces significantly influences the drug's in vivo fate (such as absorption, distribution, metabolism, and elimination) upon administration. PC denotes the phenomenon wherein one or multiple strata of proteins adhere to the external interface of nanoparticles (NPs) or microparticles within the biological milieu, encompassing ex vivo fluids (e.g., serum-containing culture media) and in vivo fluids (such as blood and tissue fluids). Hence, it is essential to claim the PC formation behaviors and mechanisms on the surface of LNPs. This overview provided a comprehensive examination of crucial aspects related to such issues, encompassing time evolution, controllability, and their subsequent impacts on LNPs. Classical studies of PC generation on the surface of LNPs were additionally integrated, and its decisive role in shaping the in vivo fate of LNPs was explored. The mechanisms underlying PC formation, including the adsorption theory and alteration theory, were introduced to delve into the formation process. Subsequently, the existing experimental outcomes were synthesized to offer insights into the research and application facets of PC, and it was concluded that the manipulation of PC held substantial promise in the realm of targeted delivery.

Nanotherapeutic Heterogeneity: Sources, Effects, and Solutions

Nanomaterials have revolutionized medicine by enabling control over drugs' pharmacokinetics, biodistribution, and biocompatibility. However, most nanotherapeutic batches are highly heterogeneous, meaning they comprise nanoparticles that vary in size, shape, charge, composition, and ligand functionalization. Similarly, individual nanotherapeutics often have heterogeneously distributed components, ligands, and charges. This review discusses nanotherapeutic heterogeneity's sources and effects on experimental readouts and therapeutic efficacy. Among other topics, it demonstrates that heterogeneity exists in nearly all nanotherapeutic types, examines how nanotherapeutic heterogeneity arises, and discusses how heterogeneity impacts nanomaterials' in vitro and in vivo behavior. How nanotherapeutic heterogeneity skews experimental readouts and complicates their optimization and clinical translation is also shown. Lastly, strategies for limiting nanotherapeutic heterogeneity are reviewed and recommendations for developing more reproducible and effective nanotherapeutics provided.

Thiophene-based lipids for mRNA delivery to pulmonary and retinal tissues

Lipid nanoparticles (LNPs) largely rely on ionizable lipids to yield successful nucleic acid delivery via electrostatic disruption of the endosomal membrane. Here, we report the identification and evaluation of ionizable lipids containing a thiophene moiety (Thio-lipids). The Thio-lipids can be readily synthesized via the Gewald reaction, allowing for modular lipid design with functional constituents at various positions of the thiophene ring. Through the rational design of ionizable lipid structure, we prepared 47 Thio-lipids and identified some structural criteria required in Thio-lipids for efficient mRNA (messenger RNA) encapsulation and delivery in vitro and in vivo. Notably, none of the tested lipids have a pH-response profile like traditional ionizable lipids, potentially due to the electron delocalization in the thiophene core. Placement of the tails and localization of the ionizable headgroup in the thiophene core can endow the nanoparticles with the capability to reach various tissues. Using high-throughput formulation and barcoding techniques, we optimized the formulations to select two top lipids-20b and 29d-and investigated their biodistribution in mice. Lipid 20b enabled LNPs to transfect the liver and spleen, and 29d LNP transfected the lung and spleen. Unexpectedly, LNP with lipid 20b was especially potent in mRNA delivery to the retina with no acute toxicity, leading to the successful delivery to the photoreceptors and retinal pigment epithelium in non-human primates.

Impact of Protein Corona Formation on the Thermoresponsive Behavior of Acrylamide-Based Nanogels

The ability to fine-tune the volume phase transition temperature (VPTT) of thermoresponsive nanoparticles is essential to their successful application in drug delivery. The rational design of these materials is limited by our understanding of the impact that nanoparticle-protein interactions have on their thermoresponsive behavior. In this work, we demonstrate how the formation of protein corona impacts the transition temperature values of acrylamide-based nanogels and their reversibility characteristics, in the presence of lysozyme, given its relevance for the ocular and intranasal administration route. Nanogels were synthesized with N-isopropylacrylamide or N-n-propylacrylamide as backbone monomers, methylenebis(acrylamide) (2.5-20 molar %) as a cross-linker, and functionalized with negatively charged monomers 2-acrylamido-2-methylpropanesulfonic acid, N-acryloyl-l-proline, or acrylic acid; characterization showed comparable particle diameter (c.a.10 nm), but formulation-dependent thermoresponsive properties, in the range 28-54 °C. Lysozyme was shown to form a complex with the negatively charged nanogels, lowering their VPTT values; the hydrophilic nature of the charged comonomer controlled the drop in VPTT upon complex formation, while matrix rigidity only had a small, yet significant effect. The cross-linker content was found to play a major role in determining the reversibility of the temperature-dependent transition of the complexes, with only 20 molar % cross-linked-nanogels displaying a fully reversible transition. These results demonstrate the importance of evaluating protein corona formation in the development of drug delivery systems based on thermoresponsive nanoparticles.

Lipid nanoparticles for targeted delivery of anticancer therapeutics: Recent advances in development of siRNA and lipoprotein-mimicking nanocarriers

The limitations inherent in conventional cancer treatment methods have stimulated recent efforts towards the design of safe nanomedicines with high efficacy for combating cancer through various promising approaches. A plethora of nanoparticles has been introduced in the development of cancer nanomedicines. Among them, different lipid nanoparticles are attractive for use due to numerous advantages and unique opportunities, including biocompatibility and targeted drug delivery. However, a comprehensive understanding of nano-bio interactions is imperative to facilitate the translation of recent advancements in the development of cancer nanomedicines into clinical practice. In this contribution, we focus on lipoprotein-mimicking nanoparticles, which possess unique features and compositions facilitating drug transport through receptor binding mechanisms. Additionally, we describe potential applications of siRNA lipid nanoparticles in the future design of anticancer nanomedicines. Thus, this review highlights recent progress, challenges, and opportunities of lipid-based lipoprotein-mimicking nanoparticles and siRNA nanocarriers designed for the targeted delivery of anticancer therapeutic agents.

Effect of the Protein Corona Formation on Antibody Functionalized Liquid Lipid Nanocarriers

The main aim of this study is to report basic knowledge on how a protein corona (PC) could affect or modify the way in which multifunctionalized nanoparticles interact with cells. With this purpose, we have firstly optimized the development of a target-specific nanocarrier by coupling a specific fluorescent antibody on the surface of functionalized lipid liquid nanocapsules (LLNCs). Thus, an anti-HER2-FITC antibody (αHER2) has been used, HER2 being a surface receptor that is overexpressed in several tumor cells. Subsequently, the in vitro formation of a PC has been developed using fetal bovine serum supplemented with human fibrinogen. Dynamic Light Scattering (DLS), Nanoparticle Tracking Analysis (NTA), Laser Doppler Electrophoresis (LDE), and Gel Chromatography techniques have been used to assure a complete physico-chemical characterization of the nano-complexes with (LLNCs-αHER2-PC) and without (LLNCs-αHER2) the surrounding PC. In addition, cellular assays were performed to study the cellular uptake and the specific cellular-nanocarrier interactions using the SKBR3 (high expression of HER2) breast cancer cell line and human dermal fibroblasts (HDFa) (healthy cell line without expression of HER2 receptors as control), showing that the SKBR3 cell line had a higher transport rate (50-fold) than HDFa at 60 min with LLNCs-αHER2. Moreover, the SKBR3 cell line incubated with LLNCs-αHER2-PC suffered a significant reduction (40%) in the uptake. These results suggest that the formation of a PC onto LLNCs does not prevent specific cell targeting, although it does have an important influence on cell uptake.

The influence of protein corona on Graphene Oxide: implications for biomedical theranostics

Graphene-based nanomaterials have attracted significant attention in the field of nanomedicine due to their unique atomic arrangement which allows for manifold applications. However, their inherent high hydrophobicity poses challenges in biological systems, thereby limiting their usage in biomedical areas. To address this limitation, one approach involves introducing oxygen functional groups on graphene surfaces, resulting in the formation of graphene oxide (GO). This modification enables improved dispersion, enhanced stability, reduced toxicity, and tunable surface properties. In this review, we aim to explore the interactions between GO and the biological fluids in the context of theranostics, shedding light on the formation of the "protein corona" (PC) i.e., the protein-enriched layer that formed around nanosystems when exposed to blood. The presence of the PC alters the surface properties and biological identity of GO, thus influencing its behavior and performance in various applications. By investigating this phenomenon, we gain insights into the bio-nano interactions that occur and their biological implications for different intents such as nucleic acid and drug delivery, active cell targeting, and modulation of cell signalling pathways. Additionally, we discuss diagnostic applications utilizing biocoronated GO and personalized PC analysis, with a particular focus on the detection of cancer biomarkers. By exploring these cutting-edge advancements, this comprehensive review provides valuable insights into the rapidly evolving field of GO-based nanomedicine for theranostic applications.

Could a Non-Cellular Molecular Interactome in the Blood Circulation Influence Pathogens' Infectivity?

We advance the notion that much like artificial nanoparticles, relatively more complex biological entities with nanometric dimensions such as pathogens (viruses, bacteria, and other microorganisms) may also acquire a biomolecular corona upon entering the blood circulation of an organism. We view this biomolecular corona as a component of a much broader non-cellular blood interactome that can be highly specific to the organism, akin to components of the innate immune response to an invading pathogen. We review published supporting data and generalize these notions from artificial nanoparticles to viruses and bacteria. Characterization of the non-cellular blood interactome of an organism may help explain apparent differences in the susceptibility to pathogens among individuals. The non-cellular blood interactome is a candidate therapeutic target to treat infectious and non-infectious conditions.

Understanding drug nanocarrier and blood-brain barrier interaction based on a microfluidic microphysiological model

As many nanoparticles (NPs) have been exploited as drug carriers to overcome the resistance of the blood-brain barrier (BBB), reliable in vitro BBB models are urgently needed to help researchers to comprehensively understand drug nanocarrier-BBB interaction during penetration, which can prompt pre-clinical nanodrug exploitation. Herein, we developed a microfluidic microphysiological model, allowing the analysis of BBB homeostasis and NP penetration. We found that the BBB penetrability of gold nanoparticles (AuNPs) was size- and modification-dependent, which might be caused by a distinct transendocytosis pathway. Notably, transferrin-modified 13 nm AuNPs held the strongest BBB penetrability and induced the slightest BBB dysfunction, while bare 80 nm and 120 nm AuNPs showed opposite results. Moreover, further analysis of the protein corona showed that PEGylation reduced the protein absorption, and some proteins facilitated the BBB penetration of NPs. The developed microphysiological model provides a powerful tool for understanding the drug nanocarrier-BBB interaction, which is vital for exploiting high-efficiency and biocompatible nanodrugs.

Ionizable lipid nanoparticles deliver mRNA to pancreatic β cells via macrophage-mediated gene transfer

Systemic messenger RNA (mRNA) delivery to organs outside the liver, spleen, and lungs remains challenging. To overcome this issue, we hypothesized that altering nanoparticle chemistry and administration routes may enable mRNA-induced protein expression outside of the reticuloendothelial system. Here, we describe a strategy for delivering mRNA potently and specifically to the pancreas using lipid nanoparticles. Our results show that delivering lipid nanoparticles containing cationic helper lipids by intraperitoneal administration produces robust and specific protein expression in the pancreas. Most resultant protein expression occurred within insulin-producing β cells. Last, we found that pancreatic mRNA delivery was dependent on horizontal gene transfer by peritoneal macrophage exosome secretion, an underappreciated mechanism that influences the delivery of mRNA lipid nanoparticles. We anticipate that this strategy will enable gene therapies for intractable pancreatic diseases such as diabetes and cancer.

How Charge, Size and Protein Corona Modulate the Specific Activity of Nanostructured Lipid Carriers (NLC) against Helicobacter pylori

The major risk factor associated with the development of gastric cancer is chronic infection with Helicobacter pylori. The available treatments, based on a cocktail of antibiotics, fail in up to 40% of patients and disrupt their gut microbiota. The potential of blank nanostructured lipid carriers (NLC) for H. pylori eradication was previously demonstrated by us. However, the effect of NLC charge, size and protein corona on H. pylori-specific bactericidal activity herein studied was unknown at that time. All developed NLC formulations proved bactericidal against H. pylori. Although cationic NLC had 10-fold higher bactericidal activity than anionic NLC, they lacked specificity, since Lactobacillus acidophilus was also affected. Anionic NLC achieved complete clearance in both H. pylori morphologies (rod- and coccoid-shape) by inducing alterations in bacteria membranes and the cytoplasm, as visualized by transmission electron microscopy (TEM). The presence of an NLC protein corona, composed of 93% albumin, was confirmed by mass spectrometry. This protein corona delayed the bactericidal activity of anionic NLC against H. pylori and hindered NLC activity against Escherichia coli. Overall, these results sustain the use of NLC as a promising antibiotic-free strategy targeting H. pylori.

Surface charge influences protein corona, cell uptake and biological effects of carbon dots

Carbon dots are emerging nanoparticles (NPs) with tremendous applications, especially in the biomedical field. Herein is reported the first quantitative proteomic analysis of the protein corona formed on CDs with different surface charge properties. Four CDs were synthesized from citric acid and various amine group-containing passivation reagents, resulting in cationic NPs with increasing zeta (ζ)-potential and density of positive charges. After CD contact with serum, we show that protein corona identity is influenced by CD surface charge properties, which in turn impacts CD uptake and viability loss in macrophages. In particular, CDs with high ζ-potential (>+30 mV) and charge density (>2 μmol mg^-1) are the most highly internalized, and their cell uptake is strongly correlated with a corona enriched in vitronectin, fibulin, fetuin, adiponectin and alpha-glycoprotein. On the contrary, CDs with a lower ζ-potential (+11 mV) and charge density (0.01 μmol mg^-1) are poorly internalized, while having a corona with a very different protein signature characterized by a high abundance of apolipoproteins (APOA1, APOB and APOC), albumin and hemoglobin. These data illustrate how corona characterization may contribute to a better understanding of CD cellular fate and biological effects, and provide useful information for the development of CDs for biomedical applications.

The Yin and Yang of the protein corona on the delivery journey of nanoparticles

Nanoparticles-based drug delivery systems have attracted significant attention in biomedical fields because they can deliver loaded cargoes to the target site in a controlled manner. However, tremendous challenges must still be overcome to reach the expected targeting and therapeutic efficacy in vivo. These challenges mainly arise because the interaction between nanoparticles and biological systems is complex and dynamic and is influenced by the physicochemical properties of the nanoparticles and the heterogeneity of biological systems. Importantly, once the nanoparticles are injected into the blood, a protein corona will inevitably form on the surface. The protein corona creates a new biological identity which plays a vital role in mediating the bio-nano interaction and determining the ultimate results. Thus, it is essential to understand how the protein corona affects the delivery journey of nanoparticles in vivo and what we can do to exploit the protein corona for better delivery efficiency. In this review, we first summarize the fundamental impact of the protein corona on the delivery journey of nanoparticles. Next, we emphasize the strategies that have been developed for tailoring and exploiting the protein corona to improve the transportation behavior of nanoparticles in vivo. Finally, we highlight what we need to do as a next step towards better understanding and exploitation of the protein corona. We hope these insights into the "Yin and Yang" effect of the protein corona will have profound implications for understanding the role of the protein corona in a wide range of nanoparticles.

Amniotic fluid stabilized lipid nanoparticles for in utero intra-amniotic mRNA delivery

Congenital disorders resulting in pathological protein deficiencies are most often treated postnatally with protein or enzyme replacement therapies. However, treatment of these disorders in utero before irreversible disease onset could significantly minimize disease burden, morbidity, and mortality. One possible strategy for the prenatal treatment of congenital disorders is in utero delivery of messenger RNA (mRNA). mRNA is a nucleic acid therapeutic that has previously been investigated as a platform for protein replacement therapies and gene editing technologies. While viral vectors have been explored to induce intracellular expression of mRNA, they are limited in their clinical application due to risks associated with immunogenicity and genomic integration. As an alternative to viral vectors, safe and efficient in utero mRNA delivery can be achieved using ionizable lipid nanoparticles (LNPs). While LNPs have demonstrated potent in vivo mRNA delivery to the liver following intravenous administration, intra-amniotic delivery has the potential to deliver mRNA to cells and tissues beyond those in the liver, such as in the skin, lung, and digestive tract. However, LNP stability in fetal amniotic fluid and how this stability affects mRNA delivery has not been previously investigated. Here, we engineered a library of LNPs using orthogonal design of experiments (DOE) to evaluate how LNP structure affects their stability in amniotic fluid ex utero and whether a lead candidate identified from these stability measurements enables intra-amniotic mRNA delivery in utero. We used a combination of techniques including dynamic light scattering (DLS), transmission electron microscopy (TEM), and chromatography followed by protein content quantification to screen LNP stability in amniotic fluids. These results identified multiple lead LNP formulations that are highly stable in amniotic fluids ranging from small animals to humans, including mouse, sheep, pig, and human amniotic fluid samples. We then demonstrate that stable LNPs from the ex utero screen in mouse amniotic fluid enabled potent mRNA delivery in primary fetal lung fibroblasts and in utero following intra-amniotic injection in a murine model. This exploration of ex utero stability in amniotic fluids demonstrates a means by which to identify novel LNP formulations for prenatal treatment of congenital disorders via in utero mRNA delivery.

On the mechanism of tissue-specific mRNA delivery by selective organ targeting nanoparticles

Lipid nanoparticles (LNPs) are a clinically mature technology for the delivery of genetic medicines but have limited therapeutic applications due to liver accumulation. Recently, our laboratory developed selective organ targeting (SORT) nanoparticles that expand the therapeutic applications of genetic medicines by enabling delivery of messenger RNA (mRNA) and gene editing systems to non-liver tissues. SORT nanoparticles include a supplemental SORT molecule whose chemical structure determines the LNP's tissue-specific activity. To understand how SORT nanoparticles surpass the delivery barrier of liver hepatocyte accumulation, we studied the mechanistic factors which define their organ-targeting properties. We discovered that the chemical nature of the added SORT molecule controlled biodistribution, global/apparent pK_a, and serum protein interactions of SORT nanoparticles. Additionally, we provide evidence for an endogenous targeting mechanism whereby organ targeting occurs via 1) desorption of poly(ethylene glycol) lipids from the LNP surface, 2) binding of distinct proteins to the nanoparticle surface because of recognition of exposed SORT molecules, and 3) subsequent interactions between surface-bound proteins and cognate receptors highly expressed in specific tissues. These findings establish a crucial link between the molecular composition of SORT nanoparticles and their unique and precise organ-targeting properties and suggest that the recruitment of specific proteins to a nanoparticle's surface can enable drug delivery beyond the liver.

Embracing nanomaterials' interactions with the innate immune system

Immunotherapy has firmly established itself as a compelling avenue for treating disease. Although many clinically approved immunotherapeutics engage the adaptive immune system, therapeutically targeting the innate immune system remains much less explored. Nanomedicine offers a compelling opportunity for innate immune system engagement, as many nanomaterials inherently interact with myeloid cells (e.g., monocytes, macrophages, neutrophils, and dendritic cells) or can be functionalized to target their cell-surface receptors. Here, we provide a perspective on exploiting nanomaterials for innate immune system regulation. We focus on specific nanomaterial design parameters, including size, form, rigidity, charge, and surface decoration. Furthermore, we examine the potential of high-throughput screening and machine learning, while also providing recommendations for advancing the field. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Spotlight on the protein corona of liposomes

Although an established drug delivery platform, liposomes have not fulfilled their true potential. In the body, interactions of liposomes are mediated by the layer of plasma proteins adsorbed on the surface, the protein corona. The review aims to collect the data of the last decade on liposome protein corona, tracing the path from interactions of individual proteins to the effects mediated by the protein corona in vivo. It offers a classification of the approaches to exploitation of the protein corona-rather than elimination thereof-based on the bilayer composition-corona composition-molecular interactions-biological performance framework. The multitude of factors that affect each level of this relationship urge to the widest implementation of bioinformatics tools to predict the most effective liposome compositions relying on the data on protein corona. Supplementing the picture with new pieces of accurately reported experimental data will contribute to the accuracy and efficiency of the predictions. STATEMENT OF SIGNIFICANCE: The review focuses on liposomes as an established nanomedicine platform and analyzes the available data on how the protein corona formed on liposome surface in biological fluids affects performance of the liposomes. The review offers a rigorous account of existing literature and critical analysis of methodology currently applied to the assessment of liposome-plasma protein interactions. It introduces a classification of the approaches to exploitation of the protein corona and tailoring liposome carriers to advance the field of nanoparticulate drug delivery systems for the benefit of patients.

Interplay between nanomedicine and protein corona

Nanomedicine is recognized as a promising agent for diverse biomedical applications; however, its safety and efficiency in clinical practice remains to be enhanced. A priority issue is the protein corona (PC), which imparts unique biological identities to prototype and determines the actual biological functions in biological fluids. Decades of work has already illuminated abundant considerations that influence the composition of the protein corona. Thereinto, the physical assets of nanomedicines (e.g., size and shape, surface properties, nanomaterials) and the biological environment collectively play fundamental roles in shaping the PC, including the types and quantities of plasma proteins. The properties of nanomedicines are dependent on certain factors. This review aims to explore the applications of nanomedicines by regulating their interplay with PC.

In vivo Protein Corona Formation: Characterizations, Effects on Engineered Nanoparticles' Biobehaviors, and Applications

Understanding the basic interactions between engineered nanoparticles (ENPs) and biological systems is essential for evaluating ENPs’ safety and developing better nanomedicine. Profound interactions between ENPs and biomolecules such as proteins are inevitable to occur when ENPs are administered or exposed to biological systems, for example, through intravenous injection, oral, or respiration. As a key component of these interactions, protein corona (PC) is immediately formed surrounding the outlayer of ENPs. PC formation is crucial because it gives ENPs a new biological identity by altering not only the physiochemical properties, but also the biobehaviors of ENPs. In the past two decades, most investigations about PC formation were carried out with in vitro systems which could not represent the true events occurring within in vivo systems. Most recently, studies of in vivo PC formation were reported, and it was found that the protein compositions and structures were very different from those formed in vitro. Herein, we provide an in-time review of the recent investigations of this in vivo PC formation of ENPs. In this review, commonly used characterization methods and compositions of in vivo PC are summarized firstly. Next, we highlight the impacts of the in vivo PC formation on absorption, blood circulation, biodistribution, metabolism, and toxicity of administered ENPs. We also introduce the applications of modulating in vivo PC formation in nanomedicine. We further discuss the challenges and future perspectives.

In vivo protein corona on nanoparticles: does the control of all material parameters orient the biological behavior?

Nanomaterials have a huge potential in research fields from nanomedicine to medical devices. However, surface modifications of nanoparticles (NPs) and thus of their physicochemical properties failed to predict their biological behavior. This requires investigating the "missing link" at the nano-bio interface. The protein corona (PC), the set of proteins binding to the NPs surface, plays a critical role in particle recognition by the innate immune system. Still, in vitro incubation offers a limited understanding of biological interactions and fails to explain the in vivo fate. To date, several reports explained the impact of PC in vitro but its applications in the clinical field have been very limited. Furthermore, PC is often considered as a biological barrier reducing the targeting efficiency of nano vehicles. But the protein binding can actually be controlled by altering PC both in vitro and in vivo. Analyzing PC in vivo could accordingly provide a deep understanding of its biological effect and speed up the transfer to clinical applications. This review demonstrates the need for clarifications on the effect of PC in vivo and the control of its behavior by changing its physicochemical properties. It unfolds the recent in vivo developments to understand mechanisms and challenges at the nano-bio interface. Finally, it reports recent advances in the in vivo PC to overcome and control the limitations of the in vitro PC by employing PC as a boosting resource to prolong the NPs half-life, to improve their formulations and thereby to increase its use for biomedical applications.

Unraveling the In Vivo Protein Corona

Understanding the behavior of nanoparticles upon contact with a physiological environment is of urgent need in order to improve their properties for a successful therapeutic application. Most commonly, the interaction of nanoparticles with plasma proteins are studied under in vitro conditions. However, this has been shown to not reflect the complex situation after in vivo administration. Therefore, here we focused on the investigation of magnetic nanoparticles with blood proteins under in vivo conditions. Importantly, we observed a radically different proteome in vivo in comparison to the in vitro situation underlining the significance of in vivo protein corona studies. Next to this, we found that the in vivo corona profile does not significantly change over time. To mimic the in vivo situation, we established an approach, which we termed “ex vivo” as it uses whole blood freshly prepared from an animal. Overall, we present a comprehensive analysis focusing on the interaction between nanoparticles and blood proteins under in vivo conditions and how to mimic this situation with our ex vivo approach. This knowledge is needed to characterize the true biological identity of nanoparticles.

Enhanced Cancer-targeted Drug Delivery Using Precoated Nanoparticles

While protein coronas (PCs) are an important barrier in the clinical application of nanomedicines, the specific effects of PCs on nanoparticles (NPs) in vivo are unclear. Herein, we demonstrated that PCs from clinical sources greatly influenced the active targeting capacities of transferrin-modified NPs (Tf-NPs). Compared to PCs from healthy volunteers, PCs from the plasma of patients with nonsmall cell lung cancer (NSCLC) decreased the A549 uptake of Tf-NPs to a greater degree. The PC proteome revealed that this difference may be mediated by certain proteins in plasma. To attenuate the negative influence of PCs from patients, precoating Tf-NPs with PCs derived from healthy mice significantly enhanced active targeting capacities. Paclitaxel-loaded Tf-NPs with PCs derived from healthy mice showed the strongest antitumor effects in mice with NSCLC. This work illustrates the influence of PCs of ligand-modified NPs in clinical practice and proposes the use of corona-enabled active targeting for precision nanomedicine.

Influence of Cell Membrane Wrapping on the Cell-Porous Silicon Nanoparticle Interactions

Biohybrid nanosystems represent the cutting-edge research in biofunctionalization of micro- and nano-systems. Their physicochemical properties bring along advantages in the circulation time, camouflaging from the phagocytes, and novel antigens. This is partially a result of the qualitative differences in the protein corona, and the preferential targeting and uptake in homologous cells. However, the effect of the cell membrane on the cellular endocytosis mechanisms and time has not been fully evaluated yet. Here, the effect is assessed by quantitative flow cytometry analysis on the endocytosis of hydrophilic, negatively charged porous silicon nanoparticles and on their membrane-coated counterparts, in the presence of chemical inhibitors of different uptake pathways. Principal component analysis is used to analyze all the data and extrapolate patterns to highlight the cell-specific differences in the endocytosis mechanisms. Furthermore, the differences in the composition of static protein corona between naked and coated particles are investigated together with how these differences affect the interaction with human macrophages. Overall, the presence of the cell membrane only influences the speed and the entity of nanoparticles association with the cells, while there is no direct effect on the endocytosis pathways, composition of protein corona, or any reduction in macrophage-mediated uptake.

The Biomolecular Corona of Lipid Nanoparticles for Gene Therapy

Gene therapy holds great potential for treating almost any disease by gene silencing, protein expression, or gene correction. To efficiently deliver the nucleic acid payload to its target tissue, the genetic material needs to be combined with a delivery platform. Lipid nanoparticles (LNPs) have proven to be excellent delivery vectors for gene therapy and are increasingly entering into routine clinical practice. Over the past two decades, the optimization of LNP formulations for nucleic acid delivery has led to a well-established body of knowledge culminating in the first-ever RNA interference therapeutic using LNP technology, i.e., Onpattro, and many more in clinical development to deliver various nucleic acid payloads. Screening a lipid library in vivo for optimal gene silencing potency in hepatocytes resulted in the identification of the Onpattro formulation. Subsequent studies discovered that the key to Onpattro's liver tropism is its ability to form a specific "biomolecular corona". In fact, apolipoprotein E (ApoE), among other proteins, adsorbed to the LNP surface enables specific hepatocyte targeting. This proof-of-principle example demonstrates the use of the biomolecular corona for targeting specific receptors and cells, thereby opening up the road to rationally designing LNPs. To date, however, only a few studies have explored in detail the corona of LNPs, and how to efficiently modulate the corona remains poorly understood. In this review, we summarize recent discoveries about the biomolecular corona, expanding the knowledge gained with other nanoparticles to LNPs for nucleic acid delivery. In particular, we address how particle stability, biodistribution, and targeting of LNPs can be influenced by the biological environment. Onpattro is used as a case study to describe both the successful development of an LNP formulation for gene therapy and the key influence of the biological environment. Moreover, we outline the techniques available to isolate and analyze the corona of LNPs, and we highlight their advantages and drawbacks. Finally, we discuss possible implications of the biomolecular corona for LNP delivery and we examine the potential of exploiting the corona as a targeting strategy beyond the liver to develop next-generation gene therapies.

Nanotechnology-based Drug Delivery, Metabolism and Toxicity

BACKGROUND

Nanoparticles (NPs) are being used extensively owing to their increased surface area, targeted delivery and enhanced retention. NPs have the potential to be used in many disease conditions. Despite widespread use, their toxicity and clinical safety still remain a major concern.

OBJECTIVE

The purpose of this study was to explore the metabolism and toxicological effects of nanotherapeutics.

METHODS

Comprehensive, time-bound literature search was done covering the period from 2010 till date. The primary focus was on the metabolism of NP including their adsorption, degradation, clearance, and bio-persistence. This review also focuses on updated investigations on NPs with respect to their toxic effects on various in vitro and in vivo experimental models.

RESULTS

Nanotechnology is a thriving field of biomedical research and an efficient drug delivery system. Further their applications are under investigation for diagnosis of disease and as medical devices.

CONCLUSION

The toxicity of NPs is a major concern in the application of NPs as therapeutics. Studies addressing metabolism, side-effects and safety of NPs are desirable to gain maximum benefits of nanotherapeutics.

Construction a Long-Circulating Delivery System of Liposomal Curcumin by Coating Albumin

Although the bioavailability and stability of curcumin can be greatly improved by liposomes encapsulation, its application is still limited due to the short circulating time. In this present work, we aim to construct a long-circulating delivery system of liposomal curcumin (Cur-Lips) by coating bovine serum albumin (BSA), namely, BSA-coated liposomal curcumin (BSA-Cur-Lips). The effects of coating albumin on the physicochemical properties of Cur-Lips were investigated. It was found that BSA-Cur-Lips was more spherical, more homogeneous in size, and significantly larger than Cur-Lips. Combining sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Coomassie bright blue staining, and X-ray photoelectron spectroscopy analysis (XPS), we confirmed that albumin molecules were stably located on the surface of BSA-Cur-Lips. In addition, the impacts of the coating albumin on the Cur-Lips release and phagocytosis by mouse macrophages Raw264.7 in vitro were investigated. We found that no significant initial burst drug release effect was observed for both Cur-Lips and BSA-Cur-Lips and the presence of albumin can enhance the liposome structure stability and slow down the release of Cur. More importantly, the macrophage phagocytosis of Cur-Lips was significantly reduced after coating albumin. In conclusion, coating albumin is a promising approach for developing a long-circulating delivery system of liposomal curcumin, and its properties including low phagocytosis, slow drug release, enhanced stability, and nontoxicity give this system great prospects for practical use.

Blood circulation of soft nanomaterials is governed by dynamic remodeling of protein opsonins at nano-biointerface

Nanomaterials in the blood must mitigate the immune response to have a prolonged vascular residency in vivo. The composition of the protein corona that forms at the nano-biointerface may be directing this, however, the possible correlation of corona composition with blood residency is currently unknown. Here‚ we report a panel of new soft single molecule polymer nanomaterials (SMPNs) with varying circulation times in mice (t_1/2β ~ 22 to 65 h) and use proteomics to probe protein corona at the nano-biointerface to elucidate the mechanism of blood residency of nanomaterials. The composition of the protein opsonins on SMPNs is qualitatively and quantitatively dynamic with time in circulation. SMPNs that circulate longer are able to clear some of the initial surface-bound common opsonins, including immunoglobulins, complement, and coagulation proteins. This continuous remodelling of protein opsonins may be an important decisive step in directing elimination or residence of soft nanomaterials in vivo.

The blood circulation time is important to the biomedical application of nanomaterials. Here, the authors explore the effect of protein corona formation on the blood residency of nanomaterials and show circulation times are governed by the dynamic remodelling of protein opsonins in vivo.

Unbiased Identification of the Liposome Protein Corona using Photoaffinity-based Chemoproteomics

Protein adsorption to the surface of a nanoparticle can fundamentally alter the character, behavior, and fate of a nanoparticle in vivo. Current methods to capture the protein corona rely on physical separation techniques and are unable to resolve key, individual protein-nanoparticle interactions. As a result, the precise link between the "synthetic" and the "biological" identity of a nanoparticle remains unclear. Herein, we report an unbiased photoaffinity-based approach to capture, characterize, and quantify the protein corona of liposomes in their native state. Compared to conventional methods, our photoaffinity approach reveals markedly different interacting proteins as well as reduced total protein binding to liposome surfaces. Identified proteins do not follow protein abundancy patterns of human serum, as has been generally reported, but are instead dominated by soluble apolipoproteins-endogenous serum proteins that have evolved to recognize the lipidic surface of circulating lipoproteins. We believe our findings are the most accurate characterization of a liposome's biological identity but, more fundamentally, reveal liposome-protein binding is, in many cases, significantly less complex than previously thought.

Albumin-driven disassembly of lipidic nanoparticles: the specific case of the squalene-adenosine nanodrug

In the field of nanomedicine, nanostructured nanoparticles (NPs) made of self-assembling prodrugs emerged in the recent years with promising properties. In particular, squalene-based drug nanoparticles have already shown their efficiency through in vivo experiments. However, a complete pattern of their stability and interactions in the blood stream is still lacking. In this work we assess the behavior of squalene-adenosine (SQAd) nanoparticles - whose neuroprotective effect has already been demonstrated in murine models - in the presence of fetal bovine serum (FBS) and of bovine serum albumin (BSA), the main protein of blood plasma. Extensive physicochemical characterizations were performed using Small Angle Neutron Scattering (SANS), cryogenic transmission electron microscopy (Cryo-TEM), circular dichroism (CD), steady-state fluorescence spectroscopy (SSFS) and isothermal titration calorimetry (ITC) as well as in silico by means of ensemble docking simulations with human serum albumin (HSA). Significant changes in the colloidal stability of the nanoparticles in the presence of serum albumin were observed. SANS, CD and SSFS analyses demonstrated an interaction between SQAd and BSA, with a partial disassembly of the nanoparticles in the presence of BSA and the formation of a complex between SQAd and BSA. The interaction free energy of SQAd nanoparticles with BSA derived from ITC experiments, is about -8 kcal mol^-1 which is further supported in silico by ensemble docking simulations. Overall, our results show that serum albumin partially disassembles SQAd nanoparticles by extracting individual SQAd monomers from them. As a consequence, the SQAd nanoparticles would act as a circulating reservoir in the blood stream. The approach developed in this study could be extended to other soft organic nanoparticles.

In situ analysis of liposome hard and soft protein corona structure and composition in a single label-free workflow

Methodological constraints have limited our ability to study protein corona formation, slowing nanomedicine development and their successful translation into the clinic. We determined hard and soft corona structural properties along with the corresponding proteomic compositions on liposomes in a label-free workflow: surface plasmon resonance and a custom biosensor for in situ structure determination on liposomes and corona separation, and proteomics using sensitive nanoliquid chromatography tandem mass spectrometry with open-source bioinformatics platforms. Undiluted human plasma under dynamic flow conditions was used for in vivo relevance. Proof-of-concept is presented with a regular liposome formulation and two light-triggered indocyanine green (ICG) liposome formulations in preclinical development. We observed formulation-dependent differences in corona structure (thickness, protein-to-lipid ratio, and surface mass density) and protein enrichment. Liposomal lipids induced the enrichment of stealth-mediating apolipoproteins in the hard coronas regardless of pegylation, and their preferential enrichment in the soft corona of the pegylated liposome formulation with ICG was observed. This suggests that the soft corona of loosely interacting proteins contributes to the stealth properties as a component of the biological identity modulated by nanomaterial surface properties. The workflow addresses significant methodological gaps in biocorona research by providing truly complementary hard and soft corona compositions with corresponding in situ structural parameters for the first time. It has been designed into a convenient and easily reproducible single-experiment format suited for preclinical development of lipid nanomedicines.

Ultrastructural Assessment of the Anterolateral Ligament

Background:

The anterolateral ligament (ALL) has been identified as a structure on the lateral side of the knee, but debate exists regarding whether it is a capsular thickening or a ligament.

Hypothesis:

A detailed ultrastructural characterization of the ALL and its ultrastructure collagen arrangement will reveal it more closely resembles ligamentous tissue than joint capsule.

Study Design:

Descriptive laboratory study.

Methods:

Eight paired knee samples from 4 fresh-frozen male cadavers were used for this study. Samples were harvested from the ALL, the joint capsule, and the medial collateral ligament (MCL). All samples were evaluated with light microscopy (LM), transmission electron microscopy (TEM), and variable pressure scanning electron microscopy (VP-SEM). With LM, the 3 tissues were analyzed and their morphology described. With TEM, the ultrastructure and collagen characteristics were quantified and compared among specimens. Then, the 3-dimensional characteristics were compared with VP-SEM.

Results:

Ultrastructure analysis demonstrated similar morphology between the ALL and MCL, with significant differences in these 2 structures as compared with the joint capsule. On LM, the ALL and MCL were characterized by the presence of a dense collagen fiber oriented in the longitudinal and transversal directions of the fiber bundles, while the joint capsule was found to have a more disorganized architecture. On TEM, the collagen fibers of the ALL and MCL demonstrated similar ultrastructural morphology, with both having collagen fibers in parallel, longitudinal alignment. A quantitative analysis was also performed, with the mean (± SD) diameter of fibrils in the ALL and MCL being 80 ± 2.66 nm and 150 ± 3.35 nm, respectively (all P < .001). The VP-SEM highlighted that ALL and MCL morphology demonstrated arrangements of fiber bundles that are densely packed and organized, in contrast to the disorganized fibers of the joint capsule.

Conclusion:

The ALL and MCL have comparable ultrastructures that are distinctly different from the joint capsule, as visualized on LM, TEM, and VP-SEM.

Clinical Relevance:

The ALL should be considered a distinctive structure of the knee, although strictly connected to the surrounding capsule.

A comprehensive analysis of liposomal biomolecular corona upon human plasma incubation: The evolution towards the lipid corona

When drug nanocarriers enter a physiological environment, their surface gets coated by a dynamic biomolecular corona (BMC) mainly constituted by proteins. Although a deep investigation has been performed on the composition of BMC in terms of proteins, scarce attention has been posed to low molecular weight metabolites present in human plasma. In this work, for the first time, the investigation of the BMC of liposomal nanoparticles (NPs) constituted by 1,2-dioleoyl-3-trimethylammonium-propane polar lipid has been carried out by an ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry based untargeted metabolomics approach. Compounds were tentatively identified based on matches with online databases and comparison of MS/MS spectra with available spectral libraries. Moreover, a comparison of three metabolite extraction strategies, including an ultrafiltration membrane based protocol, a methanol extraction based protocol, and Wessel & Flügge protocol, was performed. Methanol extraction procedure resulted in the widest metabolic coverage of liposomal NP BMC. A total of 193 metabolites has been tentatively identified, 166 of which belonged to the class of lipids including phospholipids, steroids, carnitines, fatty alcohols, diglycerides and fatty acids. The high abundance of lipids in the BMC can be explained by the adsorption of plasma lipoproteins onto liposome surface, confirming previous works on other kinds of NPs. Lipids are important bioactive molecules, which could impact NP circulation and uptake by cells. Extending the investigation of BMC beyond the protein corona and towards the "lipid corona" may be the keystone of a better understanding and control of NP fate in human body.

Fusion dynamics of cubosome nanocarriers with model cell membranes

Drug delivery with nanocarriers relies on the interaction of individual nanocarriers with the cell surface. For lipid-based NCs, this interaction uniquely involves a process of membrane fusion between the lipid bilayer that makes up the NC and the cell membrane. Cubosomes have emerged as promising fusogenic NCs, however their individual interactions had not yet been directly observed due to difficulties in achieving adequate resolution or disentangling multiple interactions with common characterization techniques. Moreover, many studies on these interactions have been performed under static conditions which may not mimic the actual transport of NCs. Herein we have observed fusion of lipid cubosome NCs with lipid bilayers under flow. Total internal reflection microscopy has allowed visualisation of the fusion event which was sensitive to the lipid compositions and rationalized by lipid diffusion. The fusion event in supported lipid bilayers has been compared with those in cells, revealing a distinct similarity in kinetics.

Bioinspired Liposomes for Oral Delivery of Colistin to Combat Intracellular Infections by Salmonella enterica

Bacterial invasion into eukaryotic cells and the establishment of intracellular infection has proven to be an effective means of resisting antibiotic action, as anti-infective agents commonly exhibit a poor permeability across the host cell membrane. Encapsulation of anti-infectives into nanoscaled delivery systems, such as liposomes, is shown to result in an enhancement of intracellular delivery. The aim of the current work is, therefore, to formulate colistin, a poorly permeable anti-infective, into liposomes suitable for oral delivery, and to functionalize these carriers with a bacteria-derived invasive moiety to enhance their intracellular delivery. Different combinations of phospholipids and cholesterol are explored to optimize liposomal drug encapsulation and stability in biorelevant media. These liposomes are then surface-functionalized with extracellular adherence protein (Eap), derived from Staphylococcus aureus. Treatment of HEp-2 and Caco-2 cells infected with Salmonella enterica using colistin-containing, Eap-functionalized liposomes resulted in a significant reduction of intracellular bacteria, in comparison to treatment with nonfunctionalized liposomes as well as colistin alone. This indicates that such bio-invasive carriers are able to facilitate intracellular delivery of colistin, as necessary for intracellular anti-infective activity. The developed Eap-functionalized liposomes, therefore, present a promising strategy for improving the therapy of intracellular infections.

Interplay of protein corona and immune cells controls blood residency of liposomes

In vivo liposomes, like other types of nanoparticles, acquire a totally new 'biological identity' due to the formation of a biomolecular coating known as the protein corona that depends on and modifies the liposomes' synthetic identity. The liposome-protein corona is a dynamic interface that regulates the interaction of liposomes with the physiological environment. Here we show that the biological identity of liposomes is clearly linked to their sequestration from peripheral blood mononuclear cells (PBMCs) of healthy donors that ultimately leads to removal from the bloodstream. Pre-coating liposomes with an artificial corona made of human plasma proteins drastically reduces capture by circulating leukocytes in whole blood and may be an effective strategy to enable prolonged circulation in vivo. We conclude with a critical assessment of the key concepts of liposome technology that need to be reviewed for its definitive clinical translation.

The role of surface chemistry in serum protein corona-mediated cellular delivery and gene silencing with lipid nanoparticles

Delivery of genetic medicines, such as small interfering RNA (siRNA), by lipid nanoparticles (LNPs) is a promising approach towards the treatment of diseases, such as solid tumors. However, in vitro and in vivo nanoparticle delivery efficiency is influenced by the formation of a protein corona in biological media. In this study, we have formulated four types of EnCore nanoparticles (F1 to F4) with a similar composition, but different polyethylene glycol (PEG) conjugated lipid chain lengths (carbon 14 vs. carbon 18) and molar ratios (6% vs. 3%). These LNPs showed dramatic differences in cellular delivery and transfection in hepatocellular carcinoma (HepG2) cells in the absence and presence of fetal bovine serum (FBS). The presence of proteins inhibited the cellular uptake of C18 (3%) nanoparticles, while it facilitated the cellular uptake of C14 nanoparticles. Among the adsorbed proteins from FBS, apolipoprotein E, but not apolipoprotein A1, affected the cellular uptake of the carbon 14 LNPs. Additionally, surface PEG was one of the determinants for the protein corona amount and composition. Finally, different serum to LNP volume ratios resulted in different protein enrichment patterns. Overall, the results showed a correlation between surface chemistry of LNPs and the protein corona composition suggesting a potential use for targeted delivery.

Ligand density on nanoparticles: A parameter with critical impact on nanomedicine

Nanoparticles modified with ligands for specific targeting towards receptors expressed on the surface of target cells are discussed in literature towards improved delivery strategies. In such concepts the ligand density on the surface of the nanoparticles plays an important role. How many ligands per nanoparticle are best for the most efficient delivery? Importantly, this number may be different for in vitro and in vivo scenarios. In this review first viruses as "biological" nanoparticles are analyzed towards their ligand density, which is then compared to the ligand density of engineered nanoparticles. Then, experiments are reviewed in which in vitro and in vivo nanoparticle delivery has been analyzed in terms of ligand density. These results help to understand which ligand densities should be attempted for better targeting. Finally synthetic methods for controlling the ligand density of nanoparticles are described.

Brain Targeting by Liposome-Biomolecular Corona Boosts Anticancer Efficacy of Temozolomide in Glioblastoma Cells

Temozolomide (TMZ) is the current first-line chemotherapy for treatment of glioblastoma multiforme (GBM). However, similar to other brain therapeutic compounds, access of TMZ to brain tumors is impaired by the blood-brain barrier (BBB) leading to poor response for GBM patients. To overcome this major hurdle, we have synthesized a set of TMZ-encapsulating nanomedicines made of four cationic liposome (CL) formulations with systematic changes in lipid composition and physical-chemical properties. The targeting nature of this nanomedicine is provided by the recruitment of proteins, with natural targeting capacity, in the biomolecular corona (BC) layer that forms around CLs after exposure to human plasma (HP). TMZ-loaded CL-BC complexes were thoroughly characterized by dynamic light scattering (DLS), electrophoretic light scattering (ELS), and nanoliquid chromatography tandem mass spectrometry (nano-LC MS/MS). BCs were found to be enriched of typical BC fingerprints (BCFs) (e.g., Apolipoproteins, Vitronectin, and vitamin K-dependent protein), which have a substantial capacity in binding to receptors that are overexpressed at the BBB (e.g., scavenger receptor class B, type I and low-density lipoprotein receptor). We found that the CL formulation exhibiting the highest levels of targeting BCFs had larger uptake in human umbilical vein endothelial cells (HUVECs) that are commonly used as an in vitro model of the BBB. This formulation could also deliver TMZ to the human glioblastoma U-87 MG cell line and thus substantially enhance their antitumor efficacy compared to corona free CLs. Thus, we propose that the BC-based nanomedicines may pave a more effective way for efficient treatment of GBM.