Hydration of polyethylene glycol-grafted liposomes

Nanotechnology-assisted intracellular delivery of antibody as a precision therapy approach for KRAS-driven tumors

The Kirsten Rat Sarcoma Virus (KRAS) oncoprotein, one of the most prevalent mutations in cancer, has been deemed undruggable for decades. The hypothesis of this work was that delivering anti-KRAS monoclonal antibody (mAb) at the intracellular level could effectively target the KRAS oncoprotein. To reach this goal, we designed and developed tLyP1-targeted palmitoyl hyaluronate (HAC16)-based nanoassemblies (HANAs) adapted for the association of bevacizumab as a model mAb. Selected candidates with adequate physicochemical properties (below 150 nm, neutral surface charge), and high drug loading capacity (>10%, w/w) were adapted to entrap the antiKRASG12V mAb. The resulting antiKRASG12V-loaded HANAs exhibited a bilayer composed of HAC16 polymer and phosphatidylcholine (PC) enclosing a hydrophilic core, as evidenced by cryogenic-transmission electron microscopy (cryo-TEM) and X-ray photoelectron spectroscopy (XPS). Selected prototypes were found to efficiently engage the target KRASG12V and, inhibit proliferation and colony formation in KRASG12V-mutated lung cancer cell lines. In vivo, a selected formulation exhibited a tumor growth reduction in a pancreatic tumor-bearing mouse model. In brief, this study offers evidence of the potential to use nanotechnology for developing anti-KRAS precision therapy and provides a rational framework for advancing mAb intracellular delivery against intracellular targets.

Liposomes with Low Levels of Grafted Poly(ethylene glycol) Remain Susceptible to Destabilization by Anti-Poly(ethylene glycol) Antibodies

Binding of anti-PEG antibodies to poly(ethylene glycol) (PEG) on the surface of PEGylated liposomal doxorubicin (PLD) in vitro and in rats can activate complement and cause the rapid release of doxorubicin from the liposome interior. Here, we find that irinotecan liposomes (IL) and L-PLD, which have 16-fold lower levels of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-PEG2000 in their liposome membrane as compared to PLD, generate less complement activation but remain sensitive to destabilization and drug release by anti-PEG antibodies. Complement activation and liposome destabilization correlated with the theoretically estimated number of antibody molecules bound per liposome. Drug release from liposomes proceeded through the alternative complement pathway but was accelerated by the classical complement pathway. In contrast to PLD destabilization by anti-PEG immunoglobulin G (IgG), which proceeded by the insertion of membrane attack complexes in the lipid bilayer of otherwise intact PLD, anti-PEG IgG promoted the fusion of L-PLD, and IL to form unilamellar and oligo-vesicular liposomes. Anti-PEG immunoglobulin M (IgM) induced drug release from all liposomes (PLD, L-PLD, and IL) via the formation of unilamellar and oligo-vesicular liposomes. Anti-PEG IgG destabilized both PLD and L-PLD in rats, indicating that the reduction of PEG levels on liposomes is not an effective approach to prevent liposome destabilization by anti-PEG antibodies.

The molecular basis for hydrodynamic properties of PEGylated human serum albumin

Polyethylene glycol (PEG) conjugation provides a protective modification that enhances the pharmacokinetics and solubility of proteins for therapeutic use. A knowledge of the structural ensemble of these PEGylated proteins is necessary to understand the molecular details that contribute to their hydrodynamic and colligative properties. Because of the large size and dynamic flexibility of pharmaceutically important PEGylated proteins, the determination of structure is challenging. In addition, the hydration of these conjugates that contain large polymers is difficult to determine with traditional methods that identify only first shell hydration water, which does not account for the complete hydrodynamic volume of a macromolecule. Here, we demonstrate that structural ensembles, generated by coarse-grained simulations, can be analyzed with HullRad and used to predict sedimentation coefficients and concentration-dependent hydrodynamic and diffusion nonideality coefficients of PEGylated proteins. A knowledge of these concentration-dependent properties enhances the ability to design and analyze new modified protein therapeutics. HullRad accomplishes this analysis by effectively accounting for the complete hydration of a macromolecule, including that of flexible polymers.

Hydrodynamic and thermodynamic analysis of PEGylated human serum albumin

Covalent labeling of therapeutic drugs and proteins with polyethylene glycol (PEGylation) is an important modification for improving stability, solubility, and half-life. PEGylation alters protein solution behavior through its impact on thermodynamic nonideality by increasing the excluded volume, and on hydrodynamic nonideality by increasing the frictional drag. To understand PEGylation's impact, we investigated the thermodynamic and hydrodynamic properties of a model system consisting of PEGylated human serum albumin derivatives using analytical ultracentrifugation (AUC) and dynamic light scattering (DLS). We constructed PEGylated human serum albumin derivatives of single, linear 5K, 10K, 20K, and 40K PEG chains and a single branched-chain PEG of 40K (2 × 20K). Sedimentation velocity (SV) experiments were analyzed using SEDANAL direct boundary fitting to extract ideal sedimentation coefficients so, hydrodynamic nonideality ks, and thermodynamic nonideality 2BM1SV terms. These quantities allow the determination of the Stokes radius Rs, the frictional ratio f/fo, and the swollen or entrained volume Vs/v, which measure size, shape, and solvent interaction. We performed sedimentation equilibrium experiments to obtain independent measurements of thermodynamic nonideality 2BM1SE. From DLS measurements, we determined the interaction parameter, kD, the concentration dependence of the apparent diffusion coefficient, D, and from extrapolation of D to c = 0 a second estimate of Rs. Rs values derived from SV and DLS measurements and ensemble model calculations (see complementary study) are then used to show that ks + kD = theoretical 2B22M1. In contrast, experimental BM1 values from SV and sedimentation equilibrium data collectively allow for similar analysis for protein-PEG conjugates and show that ks + kD = 1.02-1.07∗BM1, rather than the widely used ks + kD = 2BM1 developed for hard spheres. The random coil behavior of PEG dominates the colloidal properties of PEG-protein conjugates and exceeds the sum of a random coil and hard-sphere volume due to excess entrained water.

Bioprinting of Synthetic Cell-like Lipid Vesicles to Augment the Functionality of Tissues after Manufacturing

Bioprinting is an automated bioassembly method that enables the formation of human tissue-like constructs to restore or replace damaged tissues. Regardless of the employed bioprinting method, cells undergo mechanical stress that can impact their survival and function postprinting. In this study, we investigate the use of a synthetic cell-like unit, giant unilamellar vesicles (GUVs), as adjuvants of the cellular function of human cells postprinting, or in future as the complete replacement of human cells. We analyzed the impact of two nozzle-based bioprinting methods (drop-on-demand and extrusion bioprinting) on the structure, stability, and function of GUVs. We showed that over 65% of the GUVs remain intact when printing at 0.5 bar, demonstrating the potential of using GUVs as a synthetic cell source. We further increased the stability of GUVs in a cell culture medium by introducing polyethylene glycol (PEG) into the GUV lipid membrane. The presence of PEG, however, diminished the structural properties of GUVs postprinting, and reduced the interaction of GUVs with human cells. Although the design of PEG-GUVs can still be modified in future studies for better cell-GUV interactions, we demonstrated that GUVs are functional postprinting. Chlorin e6-PEG-GUVs loaded with a fluorescent dye were bioprinted, and they released the dye postprinting only upon illumination. This is a new strategy to deliver carriers, such as growth factors, drugs, nutrients, or gases, inside large bioprinted specimens on a millimeter to centimeter scale. Overall, we showed that printed GUVs can augment the functionality of manufactured human tissues.

Surface functionalization of hydroxyapatite nanoparticles for biomedical applications

This review completely covers the various aspects of hydroxyapatite (HAp) nanoparticles and their role in different biological situations, and provides the surface and interface contents on (i) hydroxyapatite nanoparticles and their hybridization with organic molecules, (ii) surface designing of hydroxyapatite nanoparticles to provide their biocompatibility and photofunction, and (iii) coating technology of hydroxyapatite nanoparticles. In particular, we summarized how the HAp nanoparticles interact with the different ions and molecules and highlighted the potential for hybridization between HAp nanoparticles and organic molecules, which is driven by the interactions of the HAp nanoparticle surface ions with several functional groups of biological molecules. In addition, we highlighted the studies focusing on the interfacial interactions between the HAp nanoparticles and proteins for exploring the enhanced biocompatibility. Such studies focus on how these interactions affect the hydration layers and protein adsorption. However, the hydration layer state involves diverse molecular interactions that can alter the shape of the adsorbed proteins, thereby affecting cell adhesion and spreading on the surfaces. We also summarized the relationship between the surface properties of the HAp nanoparticles and the hydration layer. Furthermore, we spotlighted the cytocompatible photoluminescent probes that can be developed by designing HAp/organic nanohybrid structures. We then emphasized the importance of photofunctionalization in theranostics, which involves the integration of diagnostics and therapy based on the surface design of the HAp nanoparticles. Furthermore, the coating techniques using HAp nanoparticles and HAp nanoparticle/polymer composites were outlined for fusing base biomaterials with biological tissues. The advantages of HAp/biocompatible polymer composite coatings include the ability to effectively cover porous or irregularly shaped surfaces while controlling the thickness of the coating layer, and the addition of HAp nanoparticles to the polymer matrix improves the mechanical properties, increases the roughness, and forms the morphologies that mimic bone nanostructures. Therefore, the fundamental design of hydroxyapatite nanoparticles and their surfaces was suggested from various aspects for biomedical applications.

Engineering a nanoscale liposome-in-liposome for in situ biochemical synthesis and multi-stage release

Soft-matter nanoscale assemblies such as liposomes and lipid nanoparticles have the potential to deliver and release multiple cargos in an externally stimulated and site-specific manner. Such assemblies are currently structurally simplistic, comprising spherical capsules or lipid clusters. Given that form and function are intertwined, this lack of architectural complexity restricts the development of more sophisticated properties. To address this, we have devised an engineering strategy combining microfluidics and conjugation chemistry to synthesize nanosized liposomes with two discrete compartments, one within another, which we term concentrisomes. We can control the composition of each bilayer and tune both particle size and the dimensions between inner and outer membranes. We can specify the identity of encapsulated cargo within each compartment, and the biophysical features of inner and outer bilayers, allowing us to imbue each bilayer with different stimuli-responsive properties. We use these particles for multi-stage release of two payloads at defined time points, and as attolitre reactors for triggered in situ biochemical synthesis.

Quantitative Comparison of the Hydration Capacity of Surface-Bound Dextran and Polyethylene Glycol

We have quantified and compared the hydration capacity (i.e., capability to incorporate water molecules) of the two surface-bound hydrophilic polymer chains, dextran (dex) and poly(ethylene glycol) (PEG), in the form of poly(l-lysine)-graft-dextran (PLL-g-dex) and poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), respectively. The copolymers were attached to a negatively charged silica-titania surface through the electrostatic interaction between the PLL backbone and the surface in neutral aqueous media. While the molecular weights of PLL and PEG were fixed, that of dex and the grafting density of PEG or dex on the PLL were varied. The hydration capacity of the polymer chains was quantified through the combined experimental approach of optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microbalance with dissipation monitoring (QCM-D) to yield a value for areal solvation (Ψ), i.e., mass of associated solvent molecules within the polymer chains per unit substrate area. For the two series of copolymers with comparable stretched chain lengths of hydrophilic polymers, namely, PLL(20)-g-PEG(5) and PLL(20)-g-dex(10), the Ψ values gradually increased as the initial grafting density on the PLL backbone increased or as g decreased. However, the rate of increase in Ψ was higher for PEG than dextran chains, which was attributed to higher stiffness of the dextran chains. More importantly, the number of water molecules per hydrophilic group was clearly higher for PEG chains. Given that the -CH2CH2O- units that make up the PEG chains form a cage-like structure with 2-3 water molecules, these "strongly bound" water molecules can account for the slightly more favorable behavior of PEG compared to dextran in both aqueous lubrication and antifouling behavior of the copolymers.

Liposomes delivery systems of functional substances for precision nutrition

Natural bioactive compounds with antioxidant, antimicrobial, anticancer, and other biological activities are vital for maintaining the body's physiological functions and enhancing immunity. These compounds have great potential as nutritional therapeutic agents, but they can be limited due to their poor flavor, color, unstable nature, and poor water solubility, and degradation by gastrointestinal enzymes. Liposomes, as ideal carriers, can encapsulate both water-soluble and fat-soluble nutrients, enhance the bioavailability of functional substances, promote the biological activity of functional substances, and control the release of nutrients. Despite their potential, liposomes still face obstacles in nutrient delivery. Therefore, the design of liposomes for special needs, optimization of the liposome preparation process, enhancement of liposome encapsulation efficiency, and industrial production are key issues that must be addressed in order to develop food-grade liposomes. Moreover, the research on surface-targeted modification and surface functionalization of liposomes is valuable for expanding the scope of application of liposomes and achieving the release of functional substances from liposomes at the appropriate time and site. The establishment of in vivo and in vitro digestion models of nutrient-loaded liposomes, in-depth study of gastrointestinal digestive behavior after liposome ingestion, targeted nutrient release, and deciphering the nutritional intervention of human diseases and positive health promotion are promising fields with broad development prospects.

Engineering aspects of lipid-based delivery systems: In vivo gene delivery, safety criteria, and translation strategies

Defects in the genome cause genetic diseases and can be treated with gene therapy. Due to the limitations encountered in gene delivery, lipid-based supramolecular colloidal materials have emerged as promising gene carrier systems. In their non-functionalized form, lipid nanoparticles often demonstrate lower transgene expression efficiency, leading to suboptimal therapeutic outcomes, specifically through reduced percentages of cells expressing the transgene. Due to chemically active substituents, the engineering of delivery systems for genetic drugs with specific chemical ligands steps forward as an innovative strategy to tackle the drawbacks and enhance their therapeutic efficacy. Despite intense investigations into functionalization strategies, the clinical outcome of such therapies still needs to be improved. Here, we highlight and comprehensively review engineering aspects for functionalizing lipid-based delivery systems and their therapeutic efficacy for developing novel genetic cargoes to provide a full snapshot of the translation from the bench to the clinics. We outline existing challenges in the delivery and internalization processes and narrate recent advances in the functionalization of lipid-based delivery systems for nucleic acids to enhance their therapeutic efficacy and safety. Moreover, we address clinical trials using these vectors to expand their clinical use and principal safety concerns.

A dilute nematic gel produced by intramicellar segregation of two polyoxyethylene alkyl ether carboxylic acids

MOTIVATION

Surfactants like C8E8CH2COOH have such bulky headgroups that they cannot show the common sphere-to-cylinder transition, while surfactants like C18:1E2CH2COOH are mimicking lipids and form only bilayers. Mixing these two types of surfactants allows one to investigate the competition between intramicellar segregation leading to disc-like bicelles and the temperature dependent curvature constraints imposed by the mismatch between heads and tails.

EXPERIMENTS

We establish phase diagrams as a function of temperature, surfactant mole ratio, and active matter content. We locate the isotropic liquid-isotropic liquid phase separation common to all nonionic surfactant systems, as well as nematic and lamellar phases. The stability and rheology of the nematic phase is investigated. Texture determination by polarizing microscopy allows us to distinguish between the different phases. Finally, SANS and SAXS give intermicellar distances as well as micellar sizes and shapes present for different compositions in the phase diagrams.

FINDINGS

In a defined mole ratio between the two components, intramicellar segregation wins and a viscoelastic discotic nematic phase is present at low temperature. Partial intramicellar mixing upon heating leads to disc growth and eventually to a pseudo-lamellar phase. Further heating leads to complete random mixing and an isotropic phase, showing the common liquid-liquid miscibility gap. This uncommon phase sequence, bicelles, lamellar phase, micelles, and water-poor packed micelles, is due to temperature induced mixing combined with dehydration of the headgroups. This general molecular mechanism explains also why a metastable water-poor lamellar phase quenched by cooling can be easily and reproducibly transformed into a nematic phase by gentle hand shaking at room temperature, as well as the entrapment of air bubbles of any size without encapsulation by bilayers or polymers.

Development of Biotinylated Liposomes Encapsulating Metformin for Therapeutic Targeting of Inflammation-Based Diseases

Inflammation is a physiological response to a damaging stimulus but sometimes can be the cause of the onset of neurodegenerative diseases, atherosclerosis, and cancer. These pathologies are characterized by the overexpression of inflammatory markers like endothelial adhesion molecules, such as Vascular Cell Adhesion Molecule-1 (VCAM-1). In the present work, the development of liposomes for therapeutic targeted delivery to inflamed endothelia is described. The idea is to exploit a three-step pretargeting system based on the biotin-avidin high-affinity interaction: the first step involves a previously described biotin derivative bearing a VCAM-1 binding peptide; in the second step, the avidin derivative NeutrAvidinTM, which strongly binds to the biotin moiety, is injected; the final step is the administration of biotinylated liposomes that would bind to NeutravidinTM immobilized onto VCAM-1 overexpressing endothelium. Stealth biotinylated liposomes, prepared via the thin film hydration method followed by extrusion and purification via size exclusion chromatography, have been thoroughly characterized for their chemico-physical and morphological features and loaded with metformin hydrochloride, a potential anti-inflammatory agent. The three-step system, tested in vitro on different cell lines via confocal microscopy, FACS analysis and metformin uptake, has proved its suitability for therapeutic applications.

Protein-Based Patterning to Spatially Functionalize Biomimetic Membranes

The bottom-up reconstitution of proteins for their modular engineering into synthetic cellular systems can reveal hidden protein functions in vitro. This is particularly evident for the bacterial Min proteins, a paradigm for self-organizing reaction-diffusion systems that displays an unexpected functionality of potential interest for bioengineering: the directional active transport of any diffusible cargo molecule on membranes. Here, the MinDE protein system is reported as a versatile surface patterning tool for the rational design of synthetically assembled 3D systems. Employing two-photon lithography, microswimmer-like structures coated with tailored lipid bilayers are fabricated and demonstrate that Min proteins can uniformly pattern bioactive molecules on their surface. Moreover, it is shown that the MinDE system can form stationary patterns inside lipid vesicles, which allow the targeting and distinctive clustering of higher-order protein structures on their inner leaflet. Given their facile use and robust function, Min proteins thus constitute a valuable molecular toolkit for spatially patterned functionalization of artificial biosystems like cell mimics and microcarriers.

Addressing the in vivo delivery of nucleic-acid nanostructure therapeutics

DNA and RNA nanostructures are being investigated as therapeutics, vaccines, and drug delivery systems. These nanostructures can be functionalized with guests ranging from small molecules to proteins with precise spatial and stoichiometric control. This has enabled new strategies to manipulate drug activity and to engineer devices with novel therapeutic functionalities. Although existing studies have offered encouraging in vitro or pre-clinical proof-of-concepts, establishing mechanisms of in vivo delivery is the new frontier for nucleic-acid nanotechnologies. In this review, we first provide a summary of existing literature on the in vivo uses of DNA and RNA nanostructures. Based on their application areas, we discuss current models of nanoparticle delivery, and thereby highlight knowledge gaps on the in vivo interactions of nucleic-acid nanostructures. Finally, we describe techniques and strategies for investigating and engineering these interactions. Together, we propose a framework to establish in vivo design principles and advance the in vivo translation of nucleic-acid nanotechnologies.

SEDNTERP: a calculation and database utility to aid interpretation of analytical ultracentrifugation and light scattering data

Proper interpretation of analytical ultracentrifugation (AUC) data for purified proteins requires ancillary information and calculations to account for factors such as buoyancy, buffer viscosity, hydration, and temperature. The utility program SEDNTERP has been widely used by the AUC community for this purpose since its introduction in the mid-1990s. Recent extensions to this program (1) allow it to incorporate data from diffusion as well as AUC experiments; and (2) allow it to calculate the refractive index of buffer solutions (based on the solute composition of the buffer), as well as the specific refractive increment (dn/dc) of proteins based on their composition. These two extensions should be quite useful to the light scattering community as well as helpful for AUC users. The latest version also adds new terms to the partial specific volume calculations which should improve the accuracy, particularly for smaller proteins and peptides, and can calculate the viscosity of buffers containing heavy isotopes of water. It also uses newer, more accurate equations for the density of water and for the hydrodynamic properties of rods and disks. This article will summarize and review all the equations used in the current program version and the scientific background behind them. It will tabulate the values used to calculate the partial specific volume and dn/dc, as well as the polynomial coefficients used in calculating the buffer density and viscosity (most of which have not been previously published), as well as the new ones used in calculating the buffer refractive index.

Efficient transfected liposomes co-loaded with pNrf2 and pirfenidone improves safe delivery for enhanced pulmonary fibrosis reversion

Pulmonary fibrosis (PF) is an interstitial lung disease with complex pathological mechanism, and there is currently a lack of therapeutics that can heal it completely. Using gene therapy with drugs provides promising therapeutic strategies for synergistically reversing PF. However, improving the intracellular accumulation and transfection efficiency of therapeutic nucleic acids is still a critical issue that urgently needs to be addressed. Herein, we developed lipid nanoparticles (PEDPs) with high transfection efficiency coloaded with pDNA of nuclear factor erythroid 2-related factor 2 (pNrf2) and pirfenidone (PFD) for PF therapy. PEDPs can penetrate biological barriers, accumulate at the target, and exert therapeutic effects, eventually alleviating the oxidative stress imbalance in type II alveolar epithelial cells (AECs II) and inhibiting myofibroblast overactivation through the synergistic effects of Nrf2 combined with PFD, thus reversing PF. In addition, we systematically engineered various liposomes (LNPs), demonstrated that reducing the polyethylene glycol (PEG) proportion could significantly improve the uptake and transfection efficiency of the LNPs, and proposed a possible mechanism for this influence. This study clearly reveals that controlling the composition ratio of PEG in PEDPs can efficiently deliver therapeutics into AECs II, improve pNrf2 transfection, and synergize with PFD in a prospective strategy to reverse PF.

PEGylated Lipid Nanoparticle Formulations: Immunological Safety and Efficiency Perspective

Lipid nanoparticles (LNPs) have been recognized as efficient vehicles to transport a large variety of therapeutics. Currently in the spotlight as important constituents of the COVID-19 mRNA vaccines, LNPs play a significant role in protecting and transporting mRNA to cells. As one of their key constituents, polyethylene glycol (PEG)-lipid conjugates are important in defining LNP physicochemical characteristics and biological activity. PEGylation has proven particularly efficient in conferring longer systemic circulation of LNPs, thus greatly improving their pharmacokinetics and efficiency. Along with revealing the benefits of PEG conjugates, studies have revealed unexpected immune reactions against PEGylated nanocarriers such as accelerated blood clearance (ABC), involving the production of anti-PEG antibodies at initial injection, which initiates accelerated blood clearance upon subsequent injections, as well as a hypersensitivity reaction referred to as complement activation-related pseudoallergy (CARPA). Further, data have been accumulated indicating consistent yet sometimes controversial correlations between various structural parameters of the PEG-lipids, the properties of the PEGylated LNPs, and the magnitude of the observed adverse effects. Detailed knowledge and comprehension of such correlations are of foremost importance in the efforts to diminish and eliminate the undesirable immune reactions and improve the safety and efficiency of the PEGylated medicines. Here, we present an overview based on analysis of data from the CAS Content Collection regarding the PEGylated LNP immunogenicity and overall safety concerns. A comprehensive summary has been compiled outlining how various structural parameters of the PEG-lipids affect the immune responses and activities of the LNPs, with regards to their efficiency in drug delivery. This Review is thus intended to serve as a helpful resource in understanding the current knowledge in the field, in an effort to further solve the remaining challenges and to achieve full potential.

High-Precision Synthesis of RNA-Loaded Lipid Nanoparticles for Biomedical Applications

The recent development of RNA-based therapeutics in delivering nucleic acids for gene editing and regulating protein translation has led to the effective treatment of various diseases including cancer, inflammatory and genetic disorder, as well as infectious diseases. Among these, lipid nanoparticles (LNP) have emerged as a promising platform for RNA delivery and have shed light by resolving the inherent instability issues of naked RNA and thereby enhancing the therapeutic potency. These LNP consisting of ionizable lipid, helper lipid, cholesterol, and poly(ethylene glycol)-anchored lipid can stably enclose RNA and help them release into the cells' cytosol. Herein, the significant progress made in LNP research starting from the LNP constituents, formulation, and their diverse applications is summarized first. Moreover, the microfluidic methodologies which allow precise assembly of these newly developed constituents to achieve LNP with controllable composition and size, high encapsulation efficiency as well as scalable production are highlighted. Furthermore, a short discussion on current challenges as well as an outlook will be given on emerging approaches to resolving these issues.

Anti-PEG antibodies before and after a first dose of Comirnaty® (mRNA-LNP-based SARS-CoV-2 vaccine)

The early and massive vaccination campaign in Israel with the mRNA-LNP Comirnaty® (Pfizer-BioNTech) vaccine against the SARS-CoV-2 virus made available large amounts of data regarding the efficacy and safety of this vaccine. Adverse reactions to mRNA-based SARS-CoV-2 vaccines are rare events, but due to large mediatic coverage they became feared and acted as a potential source of delay for the vaccination of the Israeli population. The experience with the reactogenicity of the polyethylene glycol (PEG) moiety of PEGylated liposomes, PEGylated proteins and other PEGylated drugs raised the fear that similar adverse effects can be associated with the PEG lipid which is an essential component of currently used mRNA-LNP vaccines against COVID-19. In this study we quantified the levels of anti-PEG IgG, IgM and IgE present in the blood of 79 volunteers immediately before and 3 weeks after receiving a first dose of Comirnaty® vaccine. Our in vitro results show that different humanized anti-PEG antibodies bind the PEGylated nano-liposomes in a concentration-dependent manner, but they bind with a lower affinity to the Comirnaty vaccine, despite it having a high mole% of neutral PEG₂₀₀₀-lipid on its surface. We found an increase in IgG concentration in the blood 3 weeks after the first vaccine administration, but no increase in IgM or IgE. In addition, no severe signs of adverse reactions to the Comirnaty vaccine were observed in the population studied despite the significant pre-existing high titers of IgG before the first dose of vaccine in 2 donors.

Hydrophilic Surface Modification of Cationic Unimolecular Bottlebrush Vectors Moderate pDNA and RNP Bottleplex Stability and Delivery Efficacy

A cationic unimolecular bottlebrush polymer with chemically modified end-groups was synthesized to understand the impact of hydrophilicity on colloidal stability, nucleic acid delivery performance, and toxicity. The bottlebrush polymer template was synthesized using grafting-through techniques and was therefore composed of a polynorbornene backbone with poly(2-(dimethylamino)ethyl methacrylate) side chains with dodecyl trithiocarbonate end-groups. Postpolymerization modification was performed to fully remove the end-groups or install hydroxy and methoxy poly(ethylene glycol) functional groups on the bottlebrush exterior. The bottlebrush family was preformulated with biological payloads of pDNA and CRISPR-Cas9 RNP in both water and PBS to understand binding, aggregation kinetics, cytotoxicity, and delivery efficacy. Increasing end-group hydrophilicity and preformulation of bottleplexes in PBS increased colloidal stability and cellular viability; however, this did not always result in increased transfection efficiency. The bottlebrush family exemplifies how formulation conditions, polymer loading, and end-group functionality of bottlebrushes can be tuned to balance expression with cytotoxicity ratios and result in enhanced overall performance.

Surface modification of hydroxyapatite nanoparticles for bone regeneration by controlling their surface hydration and protein adsorption states

Autogenous bone and metallic implant grafting has been used to repair and regenerate bone defects. However, there are still many unresolved problems. It is suggested that bioceramic nanoparticles should be developed and designed to promote effective bone regeneration. In addition, it is necessary to synthesize bioceramic nanoparticles that can support proteins related to bone repair and regeneration such as collagen and albumin. As the protein-interactive bioceramic, hydroxyapatite (HA) deserves to be mentioned and has several attractive properties that are useful in biomedical fields (e.g., biocompatibility, protein adsorption capacity and stability in the physiological environment). In order to prepare novel HA nanoparticles with high biocompatibility, it can be considered that human bones are mainly composed of HA and contain a small amount of silicate, and therefore, the design of coexistence of HA with silicate can be focused. Moreover, it is proposed that the state of the hydration layer on the nanoparticle surfaces can be controlled by introducing heteroelements and polymer chains, which have a great influence on the subsequent protein adsorption and cell adhesion. In this perspective, in order to develop novel bioceramic nanoparticles for the treatment of bone defect, the design of highly biocompatible HA nanoparticles and the control of the hydration layer and protein adsorption states on the surfaces were systematically discussed based on their surface modification techniques, which are very important for the proper understanding of the interface between cells and bioceramics, leading to the further application in biomedical fields.

PEG functionalization effect of silicate-containing hydroxyapatite particles on effective collagen fibrillation with hydration layer state change

Silicate-containing hydroxyapatite (SiHA) particles were synthesized and functionalized with polyethylene glycol-silane (PEG-silane) for clarifying the effect of the bioceramic surface hydration layer states on the collagen (Col) fibrillation degree. Plate-like SiHA particles were obtained containing the SiO₄^4- ion inside and/or outside the particles. PEG-silane was successfully functionalized on SiHA particles, and the hydration layer and Col adlayer states on the particles were precisely investigated for exemplifying the importance of the water molecular states at the interface. The ratio of free to intermediate water in the hydration layers of the particles decreased when containing silicate components, and it significantly increased with increasing PEG-silane molecular occupancy, where the asymmetric stretching vibration component ratio in the free water clearly increased. In a quartz crystal microbalance with dissipation (QCM-D) measurement, the frequency change (Δf) and the energy dissipation change (ΔD) values increased with Col adsorption on the particles for 32-34 min and then Δf slightly increased (or stopped increasing) and ΔD dramatically increased, indicating the effective water mobility and state changes with the Col fibrillation at the interface. The Col fibrillation degree evaluated by tan δ and the protein secondary structure of the adlayers clearly increased due to the PEG-silane functionalization, and the tendency was supported by the increase in the fibril density under SEM observation. Surprisingly, it was found that the fibrillation degree based on the protein secondary structure was significantly correlated with the asymmetric stretching vibration component ratio in the free water molecules of the hydration layer on the particles, suggesting the importance of the hydration layer states on bioceramics for controlling Col fibrillation.

Identification and optimization of tunable endosomal escape parameters for enhanced efficacy in peptide-targeted prodrug-loaded nanoparticles

Endosomal escape of nanoparticles (NPs) is a weighty consideration for engineering successful nanomedicines. Although it is well-established that incorporation of histidine (His) in particle design improves endosomal escape for NPs, our understanding of its effects for ligand-targeted nanoparticles (TNPs) remains incomplete. Here, we systematically evaluated the cooperativity between targeting ligands and endosomolytic elements using liposomal TNPs with precise stoichiometric control over functional moieties (>90% loading efficiency). We synthesized endosomolytic lipid conjugates consisting of 1 to 10 consecutive His residues presented at the end of linkers between 2 to 45 repeating units of ethylene glycol (His_n-EG_m). His_n-EG_m had minimal effect on NP size (∼115 nm) and had no significant effect on the receptor specificity of TNPs (>90% inhibition by competing peptide). We evaluated various formulations with 8 different targeting ligands relevant to two disease models. Incorporation of His₁-EG₈ resulted in up to ∼170- and ∼12.9-fold enhancement in intracellular accumulation relative to non-endosomolytic NP and TNP, respectively. These observations were time-dependent, targeted receptor-dependent, and showed different trends for NPs and TNPs. Further evaluation demonstrated short linkers (EG_2-4) significantly enhanced nanoparticle internalization compared to EG₈ or longer by up to ∼2.5-fold. Finally, rationally optimized formulation, His₁-EG₂-TNP, improved in vitro toxicity of a DM1 prodrug to SK-BR-3 cells by ∼4.2-fold, with IC₅₀ ∼8.5 nM compared to ∼36 nM for no-His TNP, and >100 nM for non-targeted/no-His NP. This study uncovers an intricate relationship between endosomal escape and ligand-targeted drug delivery, as well as tunable parameters. Furthermore, our findings highlight the value of rational design and systematic analysis for optimization of multifunctional NPs.

Mechanistic Insight into How PEGylation Reduces the Efficacy of pH-Sensitive Liposomes from Molecular Dynamics Simulations

Liposome-based drug delivery systems composed of DOPE stabilized with cholesteryl hemisuccinate (CHMS) have been proposed as a drug delivery mechanism with pH-triggered release as the anionic form (CHSa) is protonated (CHS) at reduced pH; PEGylation is known to decrease this pH sensitivity. In this manuscript, we set out to use molecular dynamics (MD) simulations with a model with all-atom resolution to provide insight into why incorporation of poly(ethyleneglycol) (PEG) into DOPE–CHMS liposomes reduces their pH sensitivity; we also address two additional questions: (1) How CHSa stabilizes DOPE bilayers into a lamellar conformation at a physiological pH of 7.4? and (2) how the change from CHSa to CHS at acidic pH triggers the destabilization of DOPE bilayers? We found that (A) CHSa stabilizes the DOPE lipid membrane by increasing the hydrophilicity of the bilayer surface, (B) when CHSa changes to CHS by pH reduction, DOPE bilayers are destabilized due to a reduction in bilayer hydrophilicity and a reduction in the area per lipid, and (C) PEG stabilizes DOPE bilayers into the lamellar phase, thus reducing the pH sensitivity of the liposomes by increasing the area per lipid through penetration into the bilayer, which is our main focus.

Cationic lipid nanoparticle production by microfluidization for siRNA delivery

Microfluidization has been investigated as a new, scalable, and basic component saving method to produce cationic lipid nanoparticles, in particular for the delivery of short interfering RNAs (siRNAs). The design of experiment (DoE) allowed to reach optimized characteristics in terms of nanocarrier size reduction and low polydispersity. The structure of cationic liposomes and siRNA-lipoplexes was characterized. The optimized preparation parameters were identified as three microfluidization passages at a pressure of 10,000 psi, with a thin film hydration volume of 4 ml. Microfluidized liposomes mean size was 160 nm, with a polydispersity index of 0.2-0.3 and a zeta potential of +40 mV to +60 mV. Positive versus negative charge ratio between the charges of the cationic lipid and the phosphate charges of the siRNAs is a key factor determining the structure and silencing efficacy of siRNA lipoplexes. At a (+/-) charge ratio of 8, a proportion of 88% of the siRNA was associated to microfluidized lipoplexes, which remained stable for one month. These lipoplexes exhibited moderate cytotoxicity and gene silencing efficacy, which should be further optimized.

The effect of RGD-targeted and non-targeted liposomal Galbanic acid on the therapeutic efficacy of pegylated liposomal doxorubicin: From liposomal preparation to in-vivo studies

The anti-cancer therapeutic application of Galbanic acid (Gba) as a strong antiangiogenic sesquiterpene coumarin has been limited due to its low water solubility. This issue necessitates developing new liposomal formulations for the efficient delivery of Gba in vivo. In this study, various liposomal formulations were prepared by a thin-film hydration method, and Gba was incorporated into the liposomal bilayers, which consequently increased its release profile compared to formulations in our previous study prepared by remote loading methods. The most stable formulation with desired properties was selected and decorated with RGD peptide (cyclo [Arg-Gly-Asp-D-Tyr-Cys]) to target tumor vasculature actively. The fluorescently-labeled model liposomes showed that the targeting could improve the receptor-mediated endocytosis of the liposomes higher than those prepared in our previous study in vitro in human umbilical vein endothelial cells (HUVECs), which was confirmed by chicken chorioallantoic membrane angiogenesis (CAM) model in vivo. Although not significant, it also could increase the accumulation of liposomes in colon tumors. In BALB/c mice bearing colon cancer, not only non-targeted Gba liposomes but also even RGD-targeted ones combinatorial therapy with pegylated liposomal doxorubicin could improve the anti-tumor efficacy as compared to their monotherapy. These outcomes have strong consequences for cancer therapy.

The Effect of Chemical Structure of OEG Ligand Shells with Quaternary Ammonium Moiety on the Colloidal Stabilization, Cellular Uptake and Photothermal Stability of Gold Nanorods

PURPOSE

Plasmonic photothermal cancer therapy by gold nanorods (GNRs) emerges as a promising tool for cancer treatment. The goal of this study was to design cationic oligoethylene glycol (OEG) compounds varying in hydrophobicity and molecular electrostatic potential as ligand shells of GNRs. Three series of ligands with different length of OEG chain (ethylene glycol units = 3, 4, 5) and variants of quaternary ammonium salts (QAS) as terminal functional group were synthesized and compared to a prototypical quaternary ammonium ligand with alkyl chain - (16-mercaptohexadecyl)trimethylammonium bromide (MTAB).

METHODS

Step-by-step research approach starting with the preparation of compounds characterized by NMR and HRMS spectra, GNRs ligand exchange evaluation through characterization of cytotoxicity and GNRs cellular uptake was used. A method quantifying the reshaping of GNRs was applied to determine the effect of ligand structure on the heat transport from GNRs under fs-laser irradiation.

RESULTS

Fourteen out of 18 synthesized OEG compounds successfully stabilized GNRs in the water. The colloidal stability of prepared GNRs in the cell culture medium decreased with the number of OEG units. In contrast, the cellular uptake of OEG+GNRs by HeLa cells increased with the length of OEG chain while the structure of the QAS group showed a minor role. Compared to MTAB, more hydrophilic OEG compounds exhibited nearly two order of magnitude lower cytotoxicity in free state and provided efficient cellular uptake of GNRs close to the level of MTAB. Regarding photothermal properties, OEG compounds evoked the photothermal reshaping of GNRs at lower peak fluence (14.8 mJ/cm2) of femtosecond laser irradiation than the alkanethiol MTAB.

CONCLUSION

OEG+GNRs appear to be optimal for clinical applications with systemic administration of NPs not-requiring irradiation at high laser intensity such as drug delivery and photothermal therapy inducing apoptosis.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Apolipoprotein E Binding Drives Structural and Compositional Rearrangement of mRNA-Containing Lipid Nanoparticles

Emerging therapeutic treatments based on the production of proteins by delivering mRNA have become increasingly important in recent times. While lipid nanoparticles (LNPs) are approved vehicles for small interfering RNA delivery, there are still challenges to use this formulation for mRNA delivery. LNPs are typically a mixture of a cationic lipid, distearoylphosphatidylcholine (DSPC), cholesterol, and a PEG-lipid. The structural characterization of mRNA-containing LNPs (mRNA-LNPs) is crucial for a full understanding of the way in which they function, but this information alone is not enough to predict their fate upon entering the bloodstream. The biodistribution and cellular uptake of LNPs are affected by their surface composition as well as by the extracellular proteins present at the site of LNP administration, e.g., apolipoproteinE (ApoE). ApoE, being responsible for fat transport in the body, plays a key role in the LNP's plasma circulation time. In this work, we use small-angle neutron scattering, together with selective lipid, cholesterol, and solvent deuteration, to elucidate the structure of the LNP and the distribution of the lipid components in the absence and the presence of ApoE. While DSPC and cholesterol are found to be enriched at the surface of the LNPs in buffer, binding of ApoE induces a redistribution of the lipids at the shell and the core, which also impacts the LNP internal structure, causing release of mRNA. The rearrangement of LNP components upon ApoE incubation is discussed in terms of potential relevance to LNP endosomal escape.

Zwitterionic self-assembled nanoparticles as carriers for Plasmodium targeting in malaria oral treatment

The current decline in antimalarial drug efficacy due to the evolution of resistant Plasmodium strains calls for new strategies capable of improving the bioavailability of antimalarials, especially of those whose lipophilic character imparts them a low solubility in biological fluids. Here we have designed, synthesized and characterized amphiphilic zwitterionic block copolymers forming nanoparticles capable of penetrating the intestinal epithelium that can be used for oral administration. Poly(butyl methacrylate-co-morpholinoethyl sulfobetaine methacrylate) (PBMA-MESBMA)-based nanoparticles exhibited a specific targeting to Plasmodium falciparum-infected vs. parasite-free red blood cells (74.8%/0.8% respectively), which was maintained upon encapsulation of the lipophilic antimalarial drug curcumin (82.6%/0.3%). The in vitro efficacy of curcumin upon encapsulation was maintained relative to the free compound, with an IC50 around 5 μM. In vivo assays indicated a significantly increased curcumin concentration in the blood of mice one hour after being orally fed PBMA-MESBMA-curcumin in comparison to the administration of free drug (18.7 vs. 2.1 ng/ml, respectively). At longer times, however, plasma curcumin concentration equaled between free and encapsulated drug, which was reflected in similar in vivo antimalarial activities in Plasmodium yoelii yoelii-infected mice. Microscopic analysis in blood samples of fluorescently labeled PBMA-MESBMA revealed the presence of the polymer inside P. yoelii yoelii-parasitized erythrocytes one hour after oral administration to infected animals.

Manipulating Phospholipid Vesicles at the Nanoscale: A Transformation from Unilamellar to Multilamellar by an n-Alkyl-poly(ethylene oxide)

We investigated the influence of an n-alkyl-PEO polymer on the structure and dynamics of phospholipid vesicles. Multilayer formation and about a 9% increase in the size in vesicles were observed by cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), and small-angle neutron/X-ray scattering (SANS/SAXS). The results indicate a change in the lamellar structure of the vesicles by a partial disruption caused by polymer chains, which seems to correlate with about a 30% reduction in bending rigidity per unit bilayer, as revealed by neutron spin echo (NSE) spectroscopy. Also, a strong change in lipid tail relaxation was observed. Our results point to opportunities using synthetic polymers to control the structure and dynamics of membranes, with possible applications in technical materials and also in drug and nutraceutical delivery.

Quantitative Cryo-TEM Reveals New Structural Details of Doxil-Like PEGylated Liposomal Doxorubicin Formulation

Nano-drugs based on nanoparticles (NP) or on nano-assemblies as carriers of the active pharmaceutical ingredient (API) are often expected to perform better compared to conventional dosage forms. Maximum realization of this potential though requires optimization of multiple physico-chemical, including structural and morphological, parameters. Meaningful distributions of these parameters derived from sufficient populations of individual NPs rather than ensemble distributions are desirable for this task, provided that relevant high-resolution data is available. In this study we demonstrate powerful capabilities of the up-to-date cryogenic transmission electron-microscopy (cryo-TEM) as well as correlations with other techniques abundant in the nano-research milieu. We explored Doxil^®-like (an anticancer drug and the first FDA-approved nano-drug) (75–100 nm) PEGylated liposomes encapsulating single doxorubicin-sulfate nano-rod-crystals (PLD). These crystals induce liposome sphere-to-ellipsoid deformation. Doxil^® was characterized by a multitude of physicochemical methods. We demonstrate, that accompanied by advanced image-analysis means, cryo-TEM can successfully enable the determination of multiple structural parameters of such complex liposomal nano-drugs with an added value of statistically-sound distributions. The latter could not be achieved by most other physicochemical approaches. It seems that cryo-TEM is capable of quantitative description of individual liposome morphological features, including meaningful distributions of all structural elements, with averages that correlate with other physical methods. Here it is demonstrated that such quantitative cryo-TEM analysis is a powerful tool in determining what is the optimal drug to lipid ratio in PLD, which is found to be the drug to lipid ratio existing in Doxil^®.

Effect of the ammonium salt anion on the structure of doxorubicin complex and PEGylated liposomal doxorubicin nanodrugs

BACKGROUND

In Doxil®, PEGylated nanoliposomes are created by hydration of the lipids in ammonium sulfate, and are remotely loaded with doxorubicin by a transmembrane ammonium gradient. The ammonium sulfate is then removed from the external aqueous phase, surrounding the liposomes, and replaced by an isoosmotic sucrose solution in 10 mM histidine buffer at pH 6.5.

METHODS

We prepared PEGylated liposomal doxorubicin (PLD) with a series of ammonium monovalent salts that after remote loading became the intraliposome doxorubicin counteranions. We analyzed the liposomes by solution X-ray scattering, differential scanning calorimetry, and electron micropscopy.

RESULTS

PLDs prepared with sulfonic acid derivatives as counteranion exhibited chemical and physical stabilities. We determined the effect of these ammonium salt counteranions on the structure, morphology, and thermotropic behavior of the PEGylated nanoliposomes, formed before and after doxorubicin loading, and the bulk properties of the doxorubicin-counteranion complexes. By comparing the structure of the doxorubicin complexes in the bulk and inside the nanoliposomes, we revealed the effect of confinement on the structure and doxorubicin release rate for each of the derivatives of the ammonium sulfonic acid counteranions.

CONCLUSIONS

We found that the extent and direction of the doxorubicin confinement effect and its release rate were strongly dependent on the type of counteranion. The counteranions, however, neither affected the structure and thermotropic behavior of the liposome membrane, nor the thickness and density of the liposome PEG layers. In an additional study, it was demonstrated that PLD made with ammonium-methane sulfonate exhibit a much lower Hand and Foot syndrome.

GENERAL SIGNIFICANCE

The structure, physical state, and pharmacokinetics of doxorubicin in PEGylated nanoliposomes, prepared by transmembrane remote loading using gradients of ammonium salts, strongly depend on the counteranions.

Poly(Ethylene Glycol) Interacts with Hyaluronan in Aqueous Media

We report here the first evidence for the interaction of poly(ethylene glycol) (PEG) with hyaluronan (HA) in aqueous solutions. PEG-HA complexes (K_app = 45,000 ± 8000 M^-1) contained about 3.3 ± 0.1 of ethylene glycol units per disaccharide of HA. The carboxyl of the D-glucuronic acid and the amide of the N-acetyl-D-glucosamine did not participate in PEG binding. Similar experiments performed with dextran and monosaccharides showed that multiple free primary hydroxyls regularly distributed along the polysaccharide chain are necessary for PEG binding. Another novelty of our study is contraction of HA upon PEG binding. The effect was observed with HA in solution or adsorbed on positively charged liposomes. The thickness of the HA layer on the liposomes decreased 2-fold upon PEG addition. HA compaction induced by PEG may underlie the changes in the plasma membrane properties and resealing of mechanical injuries induced by Pluronics.

Cryogenically frozen PEGylated liposomes and micelles: Water penetration and polarity profiles

Poly(ethylene glycol) (PEG)-grafted lipid dispersions are widely investigated in fundamental and biotechnological research for their successful use in drug-delivery. Here, we consider mixtures of the bilayer-forming lipid dipalmitoylphosphatidylcholine (DPPC) with the micelle-forming lipid PEG:2000-phosphatidilethanolamine (PEG:2000-DPPE) fully hydrated in D₂O and measured at 77 K. Electron Spin Echo Envelope Modulation and continuous wave Electron Paramagnetic Resonance of chain-labelled lipids are employed to detect the extent of solvent permeation and the environmental polarity, respectively, across the hydrocarbon regions of the lipid assemblies. Sigmoidal water penetration and polarity profiles are described in sterically stabilized liposomes (SSL) formed at submicellar content of PEG:2000-DPPE incorporated in DPPC. Compared to DPPC bilayers, SSL show increased hydrophobicity at both the polar/apolar interface and the chain termini, and a broader transition that is shifted toward the interface. Solvent exposure and polarity decrease on going down the chain in PEG:2000-DPPE micelles. However, compared to SSL, polymer-lipid micelles show higher solvent permeation at any chain segment and the chain termini are accessible to water. In any sample, heterogeneity is found in H-bond formation between the spin-label nitroxide groups and the solvent molecules. The results at cryogenic temperature add new insights into the biophysico-chemical characterization of PEGylated lipid dispersions.

Mannose-coated polydiacetylene (PDA)-based nanomicelles: synthesis, interaction with concanavalin A and application in the water solubilization and delivery of hydrophobic molecules

Carbohydrate-lectin interactions are involved in a number of relevant biological events including fertilization, immune response, cell adhesion, tumour cell metastasis, and pathogen infection. Lectins are also tissue specific, making carbohydrates not only promising drug candidates but also excellent low molecular weight ligands for active drug delivery system decorations. In order for these interactions to be effective multivalency is essential, as the interaction of a lectin with its cognate monovalent carbohydrate epitope usually takes place with low affinity. Unlike the covalent approach, supramolecular self-assembly of glyco-monomers mediated by non-covalent forces allows accessing multivalent systems with diverse topology, composition, and assembly dynamics in a single step. In order to fine-tune the size and sugar adaptability of spherical micelles at the nanoscale for an optimal glycoside cluster effect, herein we report the synthesis of mannose-coated static micelles from diacetylene-based mannopyranosyl glycolipids differing in the length of the poly(ethyleneglycol) (PEG) chains and the oxidation state of the anomeric sulfur atom. The reported shot-gun like synthetic approach for the synthesis of dilution-insensitive micelles is based on the ability of diacetylenic-based neoglycolipids to self-assemble into micelles in water and to undergo an easy photopolymerization by a simple irradiation at 254 nm. The affinity of the obtained 6 nanosystems was assessed by enzyme-linked lectin assay (ELLA) using the mannose-specific concanavalin A lectin as a model receptor. Relative binding potency enhancements, compared to methyl α-d-mannopyranoside used as control, from 20-, to 29- to 300-fold on a sugar molar basis were observed for micelles derived from sulfonyl-, sulfinyl- and thioglycoside monomers with a tatraethyleneglycol spacer, respectively, indicative of a significant cluster glycoside effect. Moreover, pMic1 micelles are able to solubilize and slowly liberate lipophilic clinically relevant drugs, and show the enhanced cytotoxic effect of docetaxel toward prostate cancer cells. These findings highlight the potential of mannose-coated photopolymerized micelles pMic1 as an efficient nanovector for active delivery of cytotoxic hydrophobic molecules.

Premature Drug Release from Polyethylene Glycol (PEG)-Coated Liposomal Doxorubicin via Formation of the Membrane Attack Complex

Anti-polyethylene glycol (PEG) antibodies are present in many healthy individuals as well as in patients receiving polyethylene glycol-functionalized drugs. Antibodies against PEG-coated nanocarriers can accelerate their clearance, but their impact on nanodrug properties including nanocarrier integrity is unclear. Here, we show that anti-PEG IgG and IgM antibodies bind to PEG molecules on the surface of PEG-coated liposomal doxorubicin (Doxil, Doxisome, LC-101, and Lipo-Dox), resulting in complement activation, formation of the membrane attack complex (C5b-9) in the liposomal membrane, and rapid release of encapsulated doxorubicin from the liposomes. Drug release depended on both classical and alternative pathways of complement activation. Doxorubicin release of up to 40% was also observed in rats treated with anti-PEG IgG and PEG-coated liposomal doxorubicin. Our results demonstrate that anti-PEG antibodies can disrupt the membrane integrity of PEG-coated liposomal doxorubicin through activation of complement, which may alter therapeutic efficacy and safety in patients with high levels of pre-existing antibodies against PEG.

Identification of a moderate affinity CD22 binding peptide and in vitro optimization of peptide-targeted nanoparticles for selective uptake by CD22+ B-cell malignancies

B cell malignancies, such as B cell leukemia and lymphoma, have CD22 overexpression with ∼7% of patients. A short CD22 binding peptide (PV3) with a moderate affinity (Kd ∼ 9 μM) was identified by screening multiple peptide candidates determined through analysis of CD22-epratuzumab complex crystal structure. PV3 binding specificity was confirmed via competitive binding inhibition, then was used as the targeting moiety on CD22-targeted liposomal nanoparticle (TNPPV3) formulations. To maximize the potential therapeutic outcome of TNPPV3 formulation, nanoparticle design parameters, such as peptide hydrophilicity, ethylene glycol linker length, valency, and particle size were optimized for maximum selective cellular uptake by CD22+ malignant cancer cells. The effects of altering design parameters one at a time on TNP uptake were evaluated using flow cytometry, and the optimal parameters for TNPPV3 were determined to be 8% peptide density, EG18 linker, and 3 lysines of 100 nm nanoparticles. This optimally designed TNPPV3 achieved ∼4 and 40-fold enhancement of cellular uptake by CD22+ Raji cells over CD22- Jurkat and MOLT-4 cells, respectively, demonstrating selectivity for malignant cells with CD22 overexpression. Overall, this study establishes PV3 to be CD22 binding peptide with proven effectiveness as a targeting element. In future, the optimal TNPPV3 formulation will potentially achieve maximal in vivo therapeutic outcomes by efficiently targeting CD22+ blood cancer cells in vivo.

Synthesis of nanostructured silica/hydroxyapatite hybrid particles containing amphiphilic triblock copolymer for effectively controlling hydration layer structures with cytocompatibility

We synthesized nanostructured mesoporous silica (MS)/hydroxyapatite (HA) hybrid particles in the presence of amphiphilic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO₂₀PPO₇₀PEO₂₀) triblock copolymer (P123). The particles exhibited slit-shaped mesostructures and underwent hybridization reaction between the MS and HA phases containing P123. Furthermore, the aggregated form of the particles exhibited dispersion stability in water in the monodispersed state (average particle size: 145 nm and coefficient of variation: 4.3% in the case of the maximum added amount of P123). Then, the structures of the hydration layer and the adsorbed protein on the particles were investigated to understand the effect of the hydration layer structures on the protein secondary structures. The ratio of the bonding water (intermediate and nonfreezing water) to free water increased upon hybridization, and it decreased with increasing P123 concentration. Upon hybridization, the component ratio of the asymmetric O-H stretching vibration between free water molecules decreased, and that of the symmetric O-H stretching vibration of intermediate water molecules increased. With increasing P123 concentration, the asymmetric O-H stretching vibration between free water molecules increased and the symmetric O-H stretching vibration of intermediate water molecules decreased. It was found that the protein native state component ratios of α-helix and β-sheet increased with increasing symmetric O-H stretching vibration between intermediate water molecules, and they decreased with decreasing asymmetric O-H stretching vibration between free water molecules. Moreover, the cytotoxicity against osteoblasts (MC3T3-E1) was evaluated and the hybrid particles exhibited a high cell density, indicating their bioactivity. On the hybrid particles interacting with P123, the cells were three-dimensionally assembled and uniaxially grown with the culture. Therefore, this is the first successful report of the synthesis of nanostructured MS/HA hybrid particles interacting with P123, and the controlled hydration layer structures on the particle surfaces were found to contribute to the protein secondary structures, promoting cytocompatibility.

Study of Structural stability and formation mechanisms in DSPC and DPSM liposomes: A coarse-grained molecular dynamics simulation

Liposomes or biological vesicles can be created from cholesterol, phospholipid, and water. Their stability is affected by their phospholipid composition which can influence disease treatment and drug delivery efficacy. In this study, the effect of phospholipid type on the formation and stability of liposomes using coarse-grained molecular dynamics simulations is investigated. For this purpose, the simulation study of the DSPC (1,2-distearoyl-sn-glycero-3-phosphocholine) and DPSM (Egg sphingomyelin) lipids were considered. All simulations were carried out using the Gromacs software and Martini force field 2.2. Energy minimization (3000 steps) model, equilibrium at constant volume to adjust the temperature at 400 Kelvin and equilibrium at constant pressure to adjust the pressure, at atmospheric pressure (1 bar) have been validated. Microsecond simulations, as well as formation analysis including density, radial distribution function, and solvent accessible surface area, demonstrated spherical nanodisc structures for the DPSM and DSPC liposomes. The results revealed that due to the cylindrical geometric structure and small-size head group, the DSPC lipid maintained its perfectly spherical structure. However, the DPSM lipid showed a conical geometric structure with larger head group than other lipids, which allows the liposome to form a micelle structure. Although the DSPC and DPSM lipids used in the laboratory tests exhibit liposome and micelle behaviors, the simulation results revealed their nanodisc structures. Energy analysis including overall energy, Van der Waals interaction energy, and electrostatic interaction energy showed that DPSM liposome is more stable than DSPC liposome.

Size-adaptable and ligand (biotin)-sheddable nanocarriers equipped with avidin scavenging technology for deep tumor penetration and reduced toxicity

The conventional active-targeting nano-chemotherapy suffers from poor tumor tissue penetration and non-negligible toxicity due to the size/ligand dilemmas and insufficient target selectivity. In this report, a stimuli-responsive size-adaptable and ligand (biotin)-sheddable drug delivery system (DDS) combined with two-step strategy of biotin-avidin system was designed to seek a balance between tumor targeting and penetration as well as to self-scavenge the nonresponsive nanocarriers in normal tissues. This DDS was composed of 'multi-seed' polymeric liposomes (ASL-BIO-MPL) with asulacrine-loaded micelles as seeds in their aqueous cavities. The shell of such liposomes was modified with MMP-9 cleavable polymer-polypeptide functionalized with the tumor targeting ligand biotin. ASL-BIO-MPL could disintegrate into mixture of irregularly-shaped liposomes (~200 nm) and scattered tiny micelles (~40 nm) after incubation with MMP-9. The fluorescence-labeled BIO-MPL could travel to the center of the 4T1 breast tumor spheroids under the action of MMP-9, possibly benefited from the relay of released tiny micelles. Conversely, neither the biotin-modified micelles nor non-MMP-9-responsive multi-seed liposomes could penetrate into the spheroids possibly due to the potent binding-site barrier of biotin and large size, respectively. In tumor-bearing mice, ASL-BIO-MPL exhibited the strongest drug penetrability and thus the optimal inhibition of tumor growth compared to other formulations. Following administration of avidin with a rational dosage regimen, the number of apoptotic cells in normal tissues induced by ASL-BIO-MPL reduced without affecting their targeting effect, suggesting the followed administration of adivin could scavenge the DDS in non-target site. Overall, the size/ligand adapting MPL system combined with two-step strategy of biotin-avidin may provide potential avenues for nanocarriers to enhance deep tumor tissue targeting and protect normal tissues.

Targeted-nanoliposomal combretastatin A4 (CA-4) as an efficient antivascular candidate in the metastatic cancer treatment

A number of antiangiogenic drugs have been approved by the Food and Drug Administration which are used in cancer therapy, and variety of other agents in several stages of clinical development or in preclinical assessment. Among these, combretastatin A4 (CA-4) is an under-researched inhibitor of angiogenesis that shows potential activity in the treatment of advanced tumors with migration capacity. However, its clinical application has been limited due to poor water solubility, low bioavailability, rapid metabolism, and systemic elimination. During the last decade, numerous investigations have been done to overcome these problems by using different CA-4 delivery systems or developing produgs of CA-4 or its structural analogs. Nevertheless, these strategies could not be efficient out of the undesired side effects on normal tissues. Nanoliposomal CA-4 not only benefits from the advantage of using liposomal drugs as opposed to free drugs but also can accumulate in the tumor site via specific targeting ligands, which leads to efficient targeting and enhancement of bioavailability. To the best of our knowledge, we consider an important attempt to understand different factors that might influence the CA-4 loading and release pattern of liposomes and the consequent results in tumor therapy. In this review, we shed light on various studied liposomal CA-4 formulations showing application thereof in cancer treatment.

Optimization of Polyarginine-Conjugated PEG Lipid Grafted Proliposome Formulation for Enhanced Cellular Association of a Protein Drug

The purpose of this study was to develop an oral proliposomal powder of protein using poly-l-arginine-conjugated 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol) (DSPE-PEG) (PLD) for enhancing cellular association upon reconstitution and to compare its effects with a non-grafted and PEGylated formulation. Cationic proliposome (CATL), PLD-grafted CATL (PLD-CATL), PEGylated CATL (PEG CATL), and PLD grafted-PEG CATL (PLD-PEG CATL) were prepared and compared. Successful conjugation between poly-l-arginine and DSPE-PEG was confirmed by ¹H NMR and FT-IR. PLD was successfully grafted onto the proliposomal powder during the slurry process. Although reconstituted liposomal sizes of CATL and PLD-CATL were increased by agglomeration, PEGylation reduced the agglomeration and increased the encapsulation. The viabilities of cells treated with both CATL and PLD-CATL formulations were low but increased following PEGylation. With regard to cellular association, PLD-CATL enhanced cellular association/uptake more rapidly than did CATL. Upon PEGylation, PEG CATL showed a lower level of cellular association/uptake compared with CATL while PLD-PEG CATL did not exhibit the rapid cellular association/uptake as seen with PLD-CATL. However, PLD-PEG CATL still enhanced the higher cellular association/uptake than PEG CATL did without PLD. In conclusion, proliposomes with PLD could accelerate cellular association/uptake but also caused high cellular toxicity. PEGylation reduced cellular toxicity and also changed the cellular association pattern of the PLD formulation.

Comparison of two different PEGylation strategies for the liposomal adjuvant CAF09: Towards induction of CTL responses upon subcutaneous vaccine administration

Using subunit vaccines, e.g., based on peptide or protein antigens, to teach the immune system to kill abnormal host cells via induction of cytotoxic T lymphocytes (CTL) is a promising strategy against intracellular infections and cancer. However, customized adjuvants are required to potentiate antigen-specific cellular immunity. One strong CTL-inducing adjuvant is the liposomal cationic adjuvant formulation (CAF)09, which is composed of dimethyldioctadecylammonium (DDA) bromide, monomycoloyl glycerol (MMG) analogue 1 and polyinosinic:polycytidylic acid [poly(I:C)]. However, this strong CTL induction requires intraperitoneal administration because the vaccine forms a depot at the site of injection (SOI) after subcutaneous (s.c.) or intramuscular (i.m.) injection, and depot formation impedes the crucial vaccine targeting to the cross-presenting dendritic cells (DCs) residing in the lymph nodes (LNs). The purpose of the present study was to investigate the effect of polyethylene glycol (PEG) grafting of CAF09 on the ability of the vaccine to induce antigen-specific CTL responses after s.c. administration. We hypothesized that steric stabilization and charge shielding of CAF09 by PEGylation may reduce depot formation at the SOI and enhance passive drainage to the LNs, eventually improving CTL induction. Hence, the vaccine (antigen/CAF09) was post-grafted with a novel type of anionic PEGylated peptides based on GDGDY repeats, which were end-conjugated with one or two PEG₁₀₀₀ moieties, resulting in mono- and bis-PEG-peptides of different lengths (10, 15 and 20 amino acid residues). For comparison, CAF09 was also grafted by inclusion of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy(PEG)-2000 (DSPE-PEG₂₀₀₀) in the bilayer structure during preparation. Grafting of CAF09 with either type of PEG resulted in charge shielding, evident from a reduced surface charge. Upon s.c. immunization of mice with the model antigen ovalbumin (OVA) adjuvanted with PEGylated CAF09, stronger CTL responses were induced as compared to immunization of mice with unadjuvanted OVA. Biodistribution studies confirmed that grafting of CAF09 with DSPE-PEG₂₀₀₀ improved the passive drainage of the vaccine to LNs, because a higher dose fraction was recovered in DCs present in the draining LNs, as compared to the dose fraction detected for non-PEGylated CAF09. In conclusion, PEGylation of CAF09 may be a useful strategy for the design of an adjuvant, which induces CTL responses after s.c. and i.m. administration. In the present studies, CAF09 grafted with 10 mol% DSPE-PEG₂₀₀₀ is the most promising of the tested adjuvants, but additional studies are required to further elucidate the potential of the strategy.