Influence of dose on liposome clearance: critical role of blood proteins

Rediscovery of mononuclear phagocyte system blockade for nanoparticle drug delivery

Rapid uptake of nanoparticles by mononuclear phagocyte system (MPS) significantly hampers their therapeutic efficacy. Temporal MPS blockade is one of the few ways to overcome this barrier - the approach rediscovered many times under different names but never extensively used in clinic. Using meta-analysis of the published data we prove the efficacy of this technique for enhancing particle circulation in blood and their delivery to tumours, describe a century of its evolution and potential combined mechanism behind it. Finally, we discuss future directions of the research focusing on the features essential for successful clinical translation of the method.

Nose-to-brain drug delivery for the treatment of glioblastoma multiforme: nanotechnological interventions

Glioblastoma multiforme (GBM) is the most aggressive malignant brain tumor with a short survival rate. Extensive research is underway for the last two decades to find an effective treatment for GBM but the tortuous pathophysiology, development of chemoresistance, and presence of BBB are the major challenges, prompting scientists to look for alternative targets and delivery strategies. Therefore, the nose to brain delivery emerged as an unorthodox and non-invasive route, which delivers the drug directly to the brain via the olfactory and trigeminal pathways and also bypasses the BBB and hepatic metabolism of the drug. However, mucociliary clearance, low administration volume, and less permeability of nasal mucosa are the obstacles retrenching the brain drug concentration. Thus, nanocarrier delivery through this route may conquer these limitations because of their unique surface characteristics and smaller size. In this review, we have emphasized the advantages and limitations of nanocarrier technologies such as polymeric, lipidic, inorganic, and miscellaneous nanoparticles used for nose-to-brain drug delivery against GBM in the past 10 years. Furthermore, recent advances, patents, and clinical trials are highlighted. However, most of these studies are in the early stages, so translating their outcomes into a marketed formulation would be a milestone in the better progression and survival of glioma patients.

Lipid nanoparticle mRNA systems containing high levels of sphingomyelin engender higher protein expression in hepatic and extra-hepatic tissues

Lipid nanoparticles (LNPs) for delivery of mRNA usually contain ionizable lipid/helper lipid/cholesterol/PEG-lipid in molar ratios of 50:10:38.5:1.5, respectively. These LNPs are rapidly cleared from the circulation following intravenous (i.v.) administration, limiting uptake into other tissues. Here, we investigate the properties of LNP mRNA systems prepared with high levels of "helper" lipids such as 1,2-distearoyl-sn-glycero-3-phosphorylcholine (DSPC) or N-(hexadecanoyl)-sphing-4-enine-1-phosphocholine (egg sphingomyelin [ESM]). We show that LNP mRNAs containing 40 mol % DSPC or ESM have a unique morphology with a small interior "solid" core situated in an aqueous compartment that is bounded by a lipid bilayer. The encapsulated mRNA exhibits enhanced stability in the presence of serum. LNP mRNA systems containing 40 mol % DSPC or ESM exhibit significantly improved transfection properties in vitro compared with systems containing 10 mol % DSPC or ESM. When injected i.v., LNP mRNAs containing 40 mol % ESM exhibit extended circulation lifetimes compared with LNP mRNA systems containing 10 mol % DSPC, resulting in improved accumulation in extrahepatic tissues. Systems containing 40 mol % ESM result in significantly improved gene expression in spleen and bone marrow as well as liver post i.v. injection compared with 10 mol % DSPC LNP mRNAs. We conclude that LNP mRNAs containing high levels of helper lipid provide a new approach for transfecting hepatic and extrahepatic tissues.

Magnetic Resonance Imaging-Guided Multi-Stimulus-Responsive Drug Delivery Strategy for Personalized and Precise Cancer Treatment

The emergence of nano-targeted controlled release liposomal drug carriers has provided a breakthrough in cancer therapy. However, their clinical efficacy is unsatisfactory, which is related to individualized differences in targeted drugs and poor in vivo release efficiency. In this paper, we prepared a class of personalized targeted and precisely controlled-release therapeutic drug carriers (GF liposomes) by co-assembling targeting and traceable o-nitrobenzyl ester lipids to propose a magnetic resonance imaging (MRI)-guided personalized in vivo targeted drug screening strategy and a multi-stimulus superimposed controlled-release strategy. Furthermore, by following the drug release process of drug-loaded liposomes (GF-D), it was found that these liposomes could rely on energy superposition to achieve more sensitive and efficient controlled drug release. In addition, the indispensable adjustment of liposome formulation for personalized MRI-based targeted therapy was verified by differential cellular uptake and in vivo magnetic resonance imaging. In the end, the 10.22-fold tumor suppression effect in the stimulus superposition group (GF-D-UV) indicates that the multi-stimulus cumulative response strategy and MRI-guided in vivo screening strategy can more effectively treat cancer. This contribution provides a concise and clever design idea for the future development of personalized precise and efficient clinical cancer therapies.

Innate and adaptive immune responses toward nanomedicines

Since the commercialization of the first liposomes used for drug delivery, Doxil/Caelyx® and Myocet®, tremendous progress has been made in understanding interactions between nanomedicines and biological systems. Fundamental work at the interface of engineering and medicine has allowed nanomedicines to deliver therapeutic small molecules and nucleic acids more efficiently. While nanomedicines are used in oncology for immunotherapy or to deliver combinations of cytotoxics, the clinical successes of gene silencing approaches like patisiran lipid complexes (Onpattro®) have paved the way for a variety of therapies beyond cancer. In parallel, the global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has highlighted the potential of mRNA vaccines to develop immunization strategies at unprecedented speed. To rationally design therapeutic and vaccines, chemists, materials scientists, and drug delivery experts need to better understand how nanotechnologies interact with the immune system. This review presents a comprehensive overview of the innate and adaptative immune systems and emphasizes the intricate mechanisms through which nanomedicines interact with these biological functions.

In vivo blockade of mononuclear phagocyte system with solid nanoparticles: Efficiency and affecting factors

Smart nanomaterials, contrast nanoparticles and drug nanocarriers of advanced targeting architecture were designed for various biomedical applications. Most of such agents demonstrate poor pharmacokinetics in vivo due to rapid elimination from the bloodstream by cells of the mononuclear phagocyte system (MPS). One of the promising methods to prolong blood circulation of the nanoparticles without their modification is MPS blockade. The method temporarily decreases macrophage endocytosis in response to uptake of a low-toxic non-functional material. The effect of different factors on the efficiency of macrophage blockade in vivo induced by solid nanomaterials has been studied here. Those include: blocker nanoparticle size, ζ-potential, surface coating, dose, mice strain, presence of tumor or inflammation. We found that the blocker particle coating type had the strongest effect on MPS blockade efficiency, which allowed to prolong functional particle blood circulation half-life 18 times. The mechanisms capable of regulation of the MPS blockade have been demonstrated, which can promote application of this phenomenon in medicine for improving delivery of diagnostic and therapeutic nanomaterials.

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.

Local Skin Inflammation in Cutaneous Leishmaniasis as a Source of Variable Pharmacokinetics and Therapeutic Efficacy of Liposomal Amphotericin B

Disfiguring skin lesions caused by several species of the Leishmania parasite characterize cutaneous leishmaniasis (CL). Successful treatment of CL with intravenous (i.v.) liposomal amphotericin B (LAmB) relies on the presence of adequate antibiotic concentrations at the dermal site of infection within the inflamed skin.

Disfiguring skin lesions caused by several species of the Leishmania parasite characterize cutaneous leishmaniasis (CL). Successful treatment of CL with intravenous (i.v.) liposomal amphotericin B (LAmB) relies on the presence of adequate antibiotic concentrations at the dermal site of infection within the inflamed skin. Here, we have investigated the impact of the local skin inflammation on the pharmacokinetics (PK) and efficacy of LAmB in two murine models of localized CL (Leishmania major and Leishmania mexicana) at three different stages of disease (papule, initial nodule, and established nodule). Twenty-four hours after the administration of one 25 mg/kg of body weight LAmB (i.v.) dose to infected BALB/c mice (n = 5), drug accumulation in the skin was found to be dependent on the causative parasite species (L. major > L. mexicana) and the disease stage (papule > initial nodule > established nodule > healthy skin). Elevated tissue drug levels were associated with increased vascular permeability (Evans blue assay) and macrophage infiltration (histomorphometry) in the infected skin, two pathophysiological parameters linked to tissue inflammation. After identical treatment of CL in the two models with 5 × 25 mg/kg LAmB (i.v.), intralesional drug concentrations and reductions in lesion size and parasite load (quantitative PCR [qPCR]) were all ≥2-fold higher for L. major than for L. mexicana. In conclusion, drug penetration of LAmB into CL skin lesions could depend on the disease stage and the causative Leishmania species due to the influence of local tissue inflammation.

Impact of Anti-Biofouling Surface Coatings on the Properties of Nanomaterials and Their Biomedical Applications

Understanding and subsequently controlling non-specific interactions between engineered nanomaterials and biological environment have become increasingly important for further developing and advancing nanotechnology for biomedical applications. Such non-specific interactions, also known as the biofouling effect, mainly associate with the adsorption of biomolecules (such as proteins, DNAs, RNAs, and peptides) onto the surface of nanomaterials and the adhesion or uptake of nanomaterials by various cells. By altering the surface properties of nanomaterials the biofouling effect can lead to in situ changes of physicochemical properties, pharmacokinetics, functions, and toxicity of nanomaterials. This review provides discussions on the current understanding of the biofouling effect, the factors that affect the non-specific interactions associated with biofouling, and the impact of the biofouling effect on the performances and functions of nanomaterials. An overview of the development and applications of various anti-biofouling coating materials to preserve and improve the properties and functions of engineered nanomaterials for intended biomedical applications is also provided.

Pharmacodynamics and Biodistribution of Single-Dose Liposomal Amphotericin B at Different Stages of Experimental Visceral Leishmaniasis

Visceral leishmaniasis is a neglected tropical disease that causes significant morbidity and mortality worldwide. Characterization of the pharmacokinetics and pharmacodynamics of antileishmanial drugs in preclinical models is important for drug development and use. Here we investigated the pharmacodynamics and drug distribution of liposomal amphotericin B (AmBisome) in Leishmania donovani-infected BALB/c mice at three different dose levels and two different time points after infection. We additionally compared drug levels in plasma, liver, and spleen in infected and uninfected BALB/c mice over time. At the highest administered dose of 10 mg/kg AmBisome, >90% parasite inhibition was observed within 2 days after drug administration, consistent with drug distribution from blood to tissue within 24 h and a fast rate of kill. Decreased drug potency was observed in the spleen when AmBisome was administered on day 35 after infection, compared to day 14 after infection. Amphotericin B concentrations and total drug amounts per organ were lower in liver and spleen when AmBisome was administered at the advanced stage of infection and compared to those in uninfected BALB/c mice. However, the magnitude of difference was lower when total drug amounts per organ were estimated. Differences were also noted in drug distribution to L. donovani-infected livers and spleens. Taken together, our data suggest that organ enlargement and other pathophysiological factors cause infection- and organ-specific drug distribution and elimination after administration of single-dose AmBisome to L. donovani-infected mice. Plasma drug levels were not reflective of changes in drug levels in tissues.

Liposomal Delivery Systems: Design Optimization and Current Applications

The liposome, a closed phospholipid bilayered vesicular system, has received considerable attention as a pharmaceutical carrier of great potential over the past 30 years. The ability of liposomes to encapsulate both hydrophilic and hydrophobic drugs, coupled with their biocompatibility and biodegradability, make liposomes attractive vehicles in the field of drug delivery. In addition, great technical advances such as remote drug loading, triggered release liposomes, ligand-targeted liposomes, liposomes containing combinations of drugs, and so on, have led to the widespread use of liposomes in diverse areas as delivery vehicles for anti-cancer, bio-active molecules, diagnostics, and therapeutic agents. In this review, we summarize design optimization of liposomal systems and invaluable applications of liposomes as effective delivery systems.

Binding of human serum albumin to PEGylated liposomes: insights into binding numbers and dynamics by fluorescence correlation spectroscopy

Liposomes for medical applications are often administered by intravenous injection. Once in the bloodstream, the liposomes are covered with a "protein corona", which impacts the behavior and eventual fate of the liposomes. Currently, many aspects of the liposomal protein corona are not well understood. For example, there is generally a lack of knowledge about the liposome binding affinities and dynamics of common types of blood plasma proteins. Fluorescence correlation spectroscopy (FCS) is a powerful experimental technique that potentially can provide such knowledge. In this study, we have used FCS to investigate the binding of human serum albumin (HSA) to standard types of PEGylated fluid-phase liposomes (consisting of DOPC and DOPE-PEG2k) and PEGylated gel-phase liposomes (consisting of DSPC and DSPE-PEG2k) with various PEG chain surface densities. We detected no significant binding of HSA to the PEGylated fluid-phase liposomes. In contrast, we found that HSA bound tightly to the PEGylated gel-phase liposomes, although only a low number of HSA molecules could be accommodated per liposome. Overall, we believe that our data provides a useful benchmark for other researchers interested in studying the liposomal protein corona.

Lipid-Based Drug Delivery Systems in Cancer Therapy: What Is Available and What Is Yet to Come

Cancer is a leading cause of death in many countries around the world. However, the efficacy of current standard treatments for a variety of cancers is suboptimal. First, most cancer treatments lack specificity, meaning that these treatments affect both cancer cells and their normal counterparts. Second, many anticancer agents are highly toxic, and thus, limit their use in treatment. Third, a number of cytotoxic chemotherapeutics are highly hydrophobic, which limits their utility in cancer therapy. Finally, many chemotherapeutic agents exhibit short half-lives that curtail their efficacy. As a result of these deficiencies, many current treatments lead to side effects, noncompliance, and patient inconvenience due to difficulties in administration. However, the application of nanotechnology has led to the development of effective nanosized drug delivery systems known commonly as nanoparticles. Among these delivery systems, lipid-based nanoparticles, particularly liposomes, have shown to be quite effective at exhibiting the ability to: 1) improve the selectivity of cancer chemotherapeutic agents; 2) lower the cytotoxicity of anticancer drugs to normal tissues, and thus, reduce their toxic side effects; 3) increase the solubility of hydrophobic drugs; and 4) offer a prolonged and controlled release of agents. This review will discuss the current state of lipid-based nanoparticle research, including the development of liposomes for cancer therapy, different strategies for tumor targeting, liposomal formulation of various anticancer drugs that are commercially available, recent progress in liposome technology for the treatment of cancer, and the next generation of lipid-based nanoparticles.

Nanocarriers for the treatment of glioblastoma multiforme: Current state-of-the-art

Glioblastoma multiforme, a grade IV glioma, is the most frequently occurring and invasive primary tumor of the central nervous system, which causes about 4% of cancer-associated-deaths, making it one of the most fatal cancers. With present treatments, using state-of-the-art technologies, the median survival is about 14 months and 2 year survival rate is merely 3-5%. Hence, novel therapeutic approaches are urgently necessary. However, most drug molecules are not able to cross the blood-brain barrier, which is one of the major difficulties in glioblastoma treatment. This review describes the features of blood-brain barrier, and its anatomical changes with different stages of tumor growth. Moreover, various strategies to improve brain drug delivery i.e. tight junction opening, chemical modification of the drug, efflux transporter inhibition, convection-enhanced delivery, craniotomy-based drug delivery and drug delivery nanosystems are discussed. Nanocarriers are one of the highly potential drug transport systems that have gained huge research focus over the last few decades for site specific drug delivery, including drug delivery to the brain. Properly designed nanocolloids are capable to cross the blood-brain barrier and specifically deliver the drug in the brain tumor tissue. They can carry both hydrophilic and hydrophobic drugs, protect them from degradation, release the drug for sustained period, significantly improve the plasma circulation half-life and reduce toxic effects. Among various nanocarriers, liposomes, polymeric nanoparticles and lipid nanocapsules are the most widely studied, and are discussed in this review. For each type of nanocarrier, a general discussion describing their composition, characteristics, types and various uses is followed by their specific application to glioblastoma treatment. Moreover, some of the main challenges regarding toxicity and standardized evaluation techniques are narrated in brief.

Nanoformulation and encapsulation approaches for poorly water-soluble drug nanoparticles

During the last few decades the nanomedicine sector has emerged as a feasible and effective solution to the problems faced by the high percentage of poorly water-soluble drugs. Decreasing the size of such drug compounds to the nanoscale can significantly change their physical properties, which lays the foundation for the use of nanomedicine for pharmaceutical applications. Various techniques have been developed to produce poorly water-soluble drug nanoparticles, mainly to address the poor water-soluble issues but also for the efficient and targeted delivery of such drugs. These techniques can be generally categorized into top-down, bottom-up and encapsulation approaches. Among them, the top-down approaches have been the main choice for industrial preparation of drug nanoparticles while other methods are actively investigated by researchers. In this review, we aim to give a comprehensive overview and latest progress of the top-down, bottom-up, and encapsulation methods for the preparation of poorly water-soluble drug nanoparticles and how solvents and additives can be selected for these methods. In addition to the more industrially applied top-down approaches, the review is focused more on bottom-up and encapsulation methods, particularly covering supercritical fluid-related methods, cryogenic techniques, and encapsulation with dendrimers and responsive block copolymers. Some of the approved and mostly used nanodrug formulations on the market are also covered to demonstrate the applications of poorly water-soluble drug nanoparticles. This review is complete with perspectives on the development and challenges of fabrication techniques for more effective nanomedicine.

Improvement of the Targeting of Radiolabeled and Functionalized Liposomes with a Two-Step System Using a Bispecific Monoclonal Antibody (Anti-CEA × Anti-DTPA-In)

This study proposes liposomes as a new tool for pretargeted radioimmunotherapy (RIT) in solid tumors. Tumor pretargeting is obtained by using a bispecific monoclonal antibody [BsmAb, anti-CEA × anti-DTPA-indium complex (DTPA–In)] and pegylated radioactive liposomes containing a lipid-hapten conjugate (DSPE–PEG–DTPA–In). In this work, the immunospecificity of tumor targeting is demonstrated both in vitro by fluorescence microscopy and in vivo by biodistribution studies.

Structure-Activity Relationship of PEGylated Polylysine Peptides as Scavenger Receptor Inhibitors for Non-Viral Gene Delivery

PEGylated polylysine peptides of the general structure PEG30 kDa-Cys-Trp-LysN (N = 10 to 30) were used to form fully condensed plasmid DNA (pGL3) polyplexes at a ratio of 1 nmol of peptide per μg of DNA (ranging from N:P 3:1 to 10:1 depending on Lys repeat). Co-administration of 5 to 80 nmols of excess PEG-peptide with fully formed polyplexes inhibited the liver uptake of (125)I-pGL3-polyplexes. The percent inhibition was dependent on the PEG-peptide dose and was saturable, consistent with inhibition of scavenger receptors. The scavenger receptor inhibition potency of PEG-peptides was dependent on the length of the Lys repeat, which increased 10-fold when comparing PEG30 kDa-Cys-Trp-Lys10 (IC50 of 20.2 μM) with PEG30 kDa-Cys-Trp-Lys25 (IC50 of 2.1 μM). We hypothesize that PEG-peptides inhibit scavenger receptors by spontaneously forming small 40 to 60 nm albumin nanoparticles that bind to and saturate the receptor. Scavenger receptor inhibition delayed the metabolism of pGL3-polyplexes, resulting in efficient gene expression in liver hepatocytes following delayed hydrodynamic dosing. PEG-peptides represent a new class of scavenger inhibitors that will likely have broad utility in blocking unwanted liver uptake and metabolism of a variety of nanoparticles.

Nanomedicine for gene therapy

Viruses are promising vehicles that result in high gene expression level, but issues of safety and virulent nature prevented its extensive use. Therefore, nonviral approach was investigated with the intervention of nanomedicine. The science of nanomedicine offered an excellent platform for therapeutic delivery as they provide options to include functionalities and engineer the system. As the term 'nano' refers to the generation of a very small dimension structure, their unique physicochemical characteristics with increased surface area/volume ratio made them potential vectors to perform gene therapy. Various forms of nanoparticles are continued to be synthesised, and this review discusses the immediate barriers that nanoparticles have to encounter both during systemic movement in the body and intracellular trafficking to deliver the genes at the site of action.

Recent advances in liposomal nanohybrid cerasomes as promising drug nanocarriers

Liposomes have been extensively investigated as possible carriers for diagnostic or therapeutic agents due to their unique properties. However, liposomes still have not attained their full potential as drug and gene delivery vehicles because of their insufficient morphological stability. Recently, a super-stable and freestanding hybrid liposomal cerasome (partially ceramic- or silica-coated liposome) has drawn much attention as a novel drug delivery system because its atomic layer of polyorganosiloxane surface imparts higher morphological stability than conventional liposomes and its liposomal bilayer structure reduces the overall rigidity and density greatly compared to silica nanoparticles. Cerasomes are more biocompatible than silica nanoparticles due to the incorporation of the liposomal architecture into cerasomes. Cerasomes combine the advantages of both liposomes and silica nanoparticles but overcome their disadvantages so cerasomes are ideal drug delivery systems. The present review will first highlights some of the key advances of the past decade in the technology of cerasome production and then review current biomedical applications of cerasomes, with a view to stimulating further research in this area of study.

Functional and biodegradable dendritic macromolecules with controlled architectures as nontoxic and efficient nanoscale gene vectors

Gene therapy has provided great potential to revolutionize the treatment of many diseases. This therapy is strongly relied on whether a delivery vector efficiently and safely directs the therapeutic genes into the target tissue/cells. Nonviral gene delivery vectors have been emerging as a realistic alternative to the use of viral analogs with the potential of a clinically relevant output. Dendritic polymers were employed as nonviral vectors due to their branched and layered architectures, globular shape and multivalent groups on their surface, showing promise in gene delivery. In the present review, we try to bring out the recent trend of studies on functional and biodegradable dendritic polymers as nontoxic and efficient gene delivery vectors. By regulating dendritic polymer design and preparation, together with recent progress in the design of biodegradable polymers, it is possible to precisely manipulate their architectures, molecular weight and chemical composition, resulting in predictable tuning of their biocompatibility as well as gene transfection activities. The multifunctional and biodegradable dendritic polymers possessing the desirable characteristics are expected to overcome extra- and intracellular obstacles, and as efficient and nontoxic gene delivery vectors to move into the clinical arena.

Efficient hepatic delivery of drugs: novel strategies and their significance

Liver is a vital organ responsible for plethora of functions including detoxification, protein synthesis, and the production of biochemicals necessary for the sustenance of life. Therefore, patients with chronic liver diseases such as viral hepatitis, liver cirrhosis, and hepatocellular carcinoma need immediate attention to sustain life and as a result are often exposed to the prolonged treatment with drugs/herbal medications. Lack of site-specific delivery of these medications to the hepatocytes/nonparenchymal cells and adverse effects associated with their off-target interactions limit their continuous use. This calls for the development and fabrication of targeted delivery systems which can deliver the drug payload at the desired site of action for defined period of time. The primary aim of drug targeting is to manipulate the whole body distribution of drugs, that is, to prevent distribution to non-target cells and concomitantly increase the drug concentration at the targeted site. Carrier molecules are designed for their selective cellular uptake, taking advantage of specific receptors or binding sites present on the surface membrane of the target cell. In this review, various aspects of liver targeting of drug molecules and herbal medications have been discussed which elucidate the importance of delivering the drugs/herbal medications at their desired site of action.

Bioavailability of polyphenol liposomes: a challenge ahead

Dietary polyphenols, including flavonoids, have long been recognized as a source of important molecules involved in the prevention of several diseases, including cancer. However, because of their poor bioavailability, polyphenols remain difficult to be employed clinically. Over the past few years, a renewed interest has been devoted to the use of liposomes as carriers aimed at increasing the bioavailability and, hence, the therapeutic benefits of polyphenols. In this paper, we review the causes of the poor bioavailability of polyphenols and concentrate on their liposomal formulations, which offer a means of improving their pharmacokinetics and pharmacodynamics. The problems linked to their development and their potential therapeutic advantages are reviewed. Future directions for liposomal polyphenol development are suggested.

Multimodal in vivo imaging exposes the voyage of nanoparticles in tumor microcirculation

Tumors present numerous biobarriers to the successful delivery of nanoparticles. Decreased blood flow and high interstitial pressure in tumors dictate the degree of resistance to extravasation of nanoparticles. To understand how a nanoparticle can overcome these biobarriers, we developed a multimodal in vivo imaging methodology, which enabled the noninvasive measurement of microvascular parameters and deposition of nanoparticles at the microscopic scale. To monitor the spatiotemporal progression of tumor vasculature and its vascular permeability to nanoparticles at the microcapillary level, we developed a quantitative in vivo imaging method using an iodinated liposomal contrast agent and a micro-CT. Following perfusion CT for quantitative assessment of blood flow, small animal fluorescence molecular tomography was used to image the in vivo fate of cocktails containing liposomes of different sizes labeled with different NIR fluorophores. The animal studies showed that the deposition of liposomes depended on local blood flow. Considering tumor regions of different blood flow, the deposition of liposomes followed a size-dependent pattern. In general, the larger liposomes effectively extravasated in fast flow regions, while smaller liposomes performed better in slow flow regions. We also evaluated whether the tumor retention of nanoparticles is dictated by targeting them to a receptor overexpressed by the cancer cells. Targeting of 100 nm liposomes showed no benefits at any flow rate. However, active targeting of 30 nm liposomes substantially increased their deposition in slow flow tumor regions (∼12-fold increase), which suggested that targeting prevented the washout of the smaller nanoparticles from the tumor interstitium back to blood circulation.

Marqibo® (vincristine sulfate liposome injection) improves the pharmacokinetics and pharmacodynamics of vincristine

Vincristine (VCR) is a mainstay of treatment of hematologic malignancies and solid tumors due to its well-defined mechanism of action, demonstrated anticancer activity and its ability to be combined with other agents. VCR is an M-phase cell cycle-specific anticancer drug with activity that is concentration and exposure duration dependent. The pharmacokinetic profile of standard VCR is described by a bi-exponential elimination pattern with a very fast initial distribution half-life followed by a longer elimination half-life. VCR also has a large volume of distribution, suggesting diffuse distribution and tissue binding. These properties may limit optimal drug exposure and delivery to target tissues as well as clinical utility as a single agent or as an effective component of multi-agent regimens. Vincristine sulfate liposome injection (VSLI), Marqibo^®, is a sphingomyelin and cholesterol-based nanoparticle formulation of VCR that was designed to overcome the dosing and pharmacokinetic limitations of standard VCR. VSLI was developed to increase the circulation time, optimize delivery to target tissues and facilitate dose intensification without increasing toxicity. In xenograft studies in mice, VSLI had a higher maximum tolerated dose, superior antitumor activity and delivered higher amounts of active drug to target tissues compared to standard VCR. VSLI recently received accelerated FDA approval for use in adults with advanced, relapsed and refractory Philadelphia chromosome-negative ALL and is in development for untreated adult ALL, pediatric ALL and untreated aggressive NHL. Here, we summarize the nonclinical data for VSLI that support its continued clinical development and recent approval for use in adult ALL.

Liposome-based delivery system for vaccine candidates: constructing an effective formulation

The discovery of liposomes in 1965 by Bangham and coworkers changed the prospects of drug delivery systems. Since then, the application of liposomes as vaccine delivery systems has been studied extensively. Liposomal vaccine delivery systems are made up of nano- or micro-sized vesicles consisting of phospholipid bilayers, in which the bioactive molecule is encapsulated/entrapped, adsorbed or surface coupled. In general, liposomes are not immunogenic on their own; thus, liposomes combined with immunostimulating ligands (adjuvants) or various other formulations have been used as vaccine delivery systems. A thorough understanding of formulation parameters allows the design of effective liposomal vaccine delivery systems. This article provides an overview of various factors that influence liposomal immunogenicity. In particular, the effects of vesicle size, surface charge, bilayer composition, lamellarity, pegylation and targeting of liposomes are described.

Treatment of experimental murine colitis with CD40 antisense oligonucleotides delivered in amphoteric liposomes

BACKGROUND AND AIMS

CD40-CD40L interactions appear to play an important role in the pathogenesis of experimental colitis. We tested the effect and investigated the underlying mechanism of action of systemically administered antisense oligonucleotide (ASO) targeting CD40 formulated in amphoteric liposomes (nov038/CD40). The charge characteristics of the amphoteric liposomes (anionic surface charge at physiological pH that becomes cationic at low pH), facilitate efficient sequestration of the ASO inside the liposomes at low pH and the direction of the carriers towards macrophages and dendritic cells under physiological conditions.

METHODS

Colitis was induced in Balb/c mice using 2,4,6-Trinitrobenzene sulphonic acid (TNBS) and treated with nov038/CD40. Disease was monitored by body weight, histology, cytokine profiling and changes in immune cell populations. CD40 expression on different cell subsets was analyzed by flow cytometry. An antigen challenge model was used to determine neoimmunity under CD40 modulation.

RESULTS

Administration of nov038/CD40 inhibited the development of TNBS colitis as assessed by weight loss, histology and cytokine profiles; unformulated CD40 ASO or nov038 encapsulating an unrelated ASO (nov038/SCR) were ineffective. The novel agent is potent as it completely suppressed even established colitis with a single treatment and significantly reduced T-cell activation as well as levels of pro-inflammatory mediators in serum. The inhibition of CD40 specifically occurred in macrophages, but not in B-cells. In contrast to prednisolone, standard treatment for inflammatory bowel diseases (IBD) that is effective in a single administration and involves extensive immunosuppression, nov038/CD40 did not affect the number of B- or Treg cells. Eventually, we observed a largely intact neoimmunity under conditions of a CD40 inhibition.

CONCLUSIONS

Administration of nov038/CD40, but neither naked CD40 ASO nor nov038/SCR, prevents the development and treats established colitis in mice. Delivery of CD40 ASO in nov038 is highly cell-specific as it selectively suppresses CD40 on macrophages, but not on B-cells; the novel agent has strong anti-inflammatory characteristics without being immunosuppressive.

Factors affecting the pharmacokinetics and pharmacodynamics of liposomal drugs

Various attempts to increase the therapeutic index of the drug while minimizing side effects have been made in drug delivery systems. Among several promising strategies, liposomes represent an advanced technology to target active molecules to the site of action. Rapid clearance of circulating liposomal drugs administered intravenously has been a critical issue because circulation time in the blood affects drug exposure at the target site. The clinical use of liposomal drugs is complicated by large intra- and interindividual variability in their pharmacokinetics (PK) and pharmacodynamics (PD). Thus, it is important to understand the factors affecting the PK/PD of the liposomal formulation of drugs and to elucidate the mechanisms underlying the variability in the PK/PD of liposomal drugs. In this review article, we describe the characteristics of liposome formulations and discuss the effects of various factors, including liposome-associated factors, host-associated factors, and treatment on the PK/PD of liposomal agents.

The journey of a drug-carrier in the body: an anatomo-physiological perspective

Recent advances in chemistry and material sciences have witnessed the emergence of an increasing number of novel and complex nanosized carriers for the delivery of drugs and imaging agents. Nevertheless, this raise in complexity does not necessarily offer more efficient systems. The lack of performance experienced by several colloidal drug carriers during the preclinical and clinical development processes can be explained by inadequate pharmacokinetic/biodistribution profiles and/or unacceptable toxicities. A comprehensive understanding of the body characteristics is necessary to predict and prevent these problems from the early stages of nanomaterial conception. In this manuscript, we review and discuss the anatomical and physiological elements which must be taken into account when designing new carriers for delivery or imaging purposes. This article gives a general overview of the main organs involved in the elimination of nanosized materials and briefly summarizes the knowledge acquired over more than 30 years of research and development in the field of drug targeting.

Influence of cationic lipid composition on gene silencing properties of lipid nanoparticle formulations of siRNA in antigen-presenting cells

Lipid nanoparticles (LNPs) are currently the most effective in vivo delivery systems for silencing target genes in hepatocytes employing small interfering RNA. Antigen-presenting cells (APCs) are also potential targets for LNP siRNA. We examined the uptake, intracellular trafficking, and gene silencing potency in primary bone marrow macrophages (bmMΦ) and dendritic cells of siRNA formulated in LNPs containing four different ionizable cationic lipids namely DLinDAP, DLinDMA, DLinK-DMA, and DLinKC2-DMA. LNPs containing DLinKC2-DMA were the most potent formulations as determined by their ability to inhibit the production of GAPDH target protein. Also, LNPs containing DLinKC2-DMA were the most potent intracellular delivery agents as indicated by confocal studies of endosomal versus cytoplamic siRNA location using fluorescently labeled siRNA. DLinK-DMA and DLinKC2-DMA formulations exhibited improved gene silencing potencies relative to DLinDMA but were less toxic. In vivo results showed that LNP siRNA systems containing DLinKC2-DMA are effective agents for silencing GAPDH in APCs in the spleen and peritoneal cavity following systemic administration. Gene silencing in APCs was RNAi mediated and the use of larger LNPs resulted in substantially reduced hepatocyte silencing, while similar efficacy was maintained in APCs. These results are discussed with regard to the potential of LNP siRNA formulations to treat immunologically mediated diseases.

Functional lipids and lipoplexes for improved gene delivery

Cationic lipids are the most common non-viral vectors used in gene delivery with a few currently being investigated in clinical trials. However, like most other synthetic vectors, these vectors suffer from low transfection efficiencies. Among the various approaches to address this challenge, functional lipids (i.e., lipids responding to a stimuli) offer a myriad of opportunities for basic studies of nucleic acid-lipid interactions and for in vitro and in vivo delivery of nucleic acid for a specific biological/medical application. This manuscript reviews recent advances in pH, redox, and charge-reversal sensitive lipids.

Active methods of drug loading into liposomes: recent strategies for stable drug entrapment and increased in vivo activity

INTRODUCTION

The use of liposomes increases the therapeutic index of many drugs, and also offers drug targeting and controlled release. The commercial impact of liposomes is strengthened by the invention of several active drug encapsulation methods, allowing the encapsulation of several weak base or weak acid drugs with very high drug-to-lipid ratios.

AREAS COVERED

In recent years, there have been reports on several new approaches to retain more hydrophobic drugs inside liposomes, in the circulation. Most of these methods apply drug precipitation inside preformed liposomes, as low soluble complexes with ions or chemicals. In some cases, drug derivatization was applied to enable active encapsulation of hydrophobic drugs, previously not reported to encapsulate, by active or remote loading. This review presents and compares most of the existing methods of active drug encapsulation and outlines recent strategies to achieve stable drug encapsulation in vivo.

EXPERT OPINION

At present, there is no single universal encapsulation method that offers stable encapsulation of most drugs; each drug requires a different approach to manage all of its properties. Now is the time to combine all these strategies to achieve the goal of a complex, but successful, anticancer therapy.

Biocompatible Nanocomplexes for Molecular Targeted MRI Contrast Agent

Accurate diagnosis in early stage is vital for the treatment of Hepatocellular carcinoma. The aim of this study was to investigate the potential of poly lactic acid-polyethylene glycol/gadolinium-diethylenetriamine-pentaacetic acid (PLA-PEG/Gd-DTPA) nanocomplexes using as biocompatible molecular magnetic resonance imaging (MRI) contrast agent. The PLA-PEG/Gd-DTPA nanocomplexes were obtained using self-assembly nanotechnology by incubation of PLA-PEG nanoparticles and the commercial contrast agent, Gd-DTPA. The physicochemical properties of nanocomplexes were measured by atomic force microscopy and photon correlation spectroscopy. The T(1)-weighted MR images of the nanocomplexes were obtained in a 3.0 T clinical MR imager. The stability study was carried out in human plasma and the distribution in vivo was investigated in rats. The mean size of the PLA-PEG/Gd-DTPA nanocomplexes was 187.9 +/- 2.30 nm, and the polydispersity index was 0.108, and the zeta potential was -12.36 +/- 3.58 mV. The results of MRI test confirmed that the PLA-PEG/Gd-DTPA nanocomplexes possessed the ability of MRI, and the direct correlation between the MRI imaging intensities and the nano-complex concentrations was observed (r = 0.987). The signal intensity was still stable within 2 h after incubation of the nanocomplexes in human plasma. The nanocomplexes gave much better image contrast effects and longer stagnation time than that of commercial contrast agent in rat liver. A dose of 0.04 mmol of gadolinium per kilogram of body weight was sufficient to increase the MRI imaging intensities in rat livers by five-fold compared with the commercial Gd-DTPA. PLA-PEG/Gd-DTPA nanocomplexes could be prepared easily with small particle sizes. The nanocomplexes had high plasma stability, better image contrast effect, and liver targeting property. These results indicated that the PLA-PEG/Gd-DTPA nanocomplexes might be potential as molecular targeted imaging contrast agent.

The effect of circulation lifetime and drug-to-lipid ratio of intravenously administered lipid nanoparticles on the biodistribution and immunostimulatory activity of encapsulated CpG-ODN

The encapsulation of conventional drugs in lipid nanoparticles (LNs) has been extensively utilized to enhance therapeutic activity by altering their pharmacokinetic (PK) and biodistribution (BD) properties. We have previously shown that the immunostimulatory activity of unmethylated cytidine-guanosine (CpG)-containing immunostimulatory oligodeoxynucleotides (ODN) is greatly enhanced when encapsulated in an LN (LN CpG-ODN). Here, we investigate the effect of circulation lifetime (determined by lipid composition) and drug-to-lipid (D/L) ratio of intravenously (i.v.) administered LN CpG-ODN on PK, BD, and cellular uptake and correlate these parameters with the immunostimulatory activity. Results from these studies show that despite significant differences in the circulation lifetime and the D/L ratio, the immune response is similar with respect to immune cell activation and cytolytic activity in the spleen and the blood compartments. Our findings indicate that the benefits of liposomal nanoparticles for the delivery of immunomodulatory drugs such as CpG-ODN are defined by a different paradigm than that for conventional drugs.

Time-dependent changes in opsonin amount associated on nanoparticles alter their hepatic uptake characteristics

The relationship between the time-dependent change in serum proteins adsorbed on nanoparticles and their disposition to the liver was investigated by employing lecithin-coated polystyrene nanosphere with a size of 50 nm (LNS-50) as a model nanoparticle in rats. The total amount of proteins adsorbed on LNS-50 increased and the qualitative profile of serum proteins adsorbed on LNS-50 changed during the incubation with serum up to 360 min. The liver perfusion study indicated that the hepatic uptake of LNS-50 incubated with serum for 360 min was significantly larger than those of LNS-50 incubated for shorter period. It was suggested that the increase in the hepatic uptake of LNS-50 with the increase in incubation time would be ascribed mainly to the increase in the opsonin-mediated uptake by Kupffer cells. Semi-quantification of major opsonins, complement C3 (C3) and immunoglobulin G (IgG), and in vitro uptake study in primary cultured Kupffer cells demonstrated that the increase in C3 and IgG amounts adsorbed on LNS-50 was directly reflected in the increased disposition of LNS-50 to Kupffer cells. These results indicate that the amounts of opsonins associated on nanoparticles would change over time and this process would be substantially reflected in the alteration of their hepatic disposition characteristics.

Influence of poly(ethylene glycol) grafting density and polymer length on liposomes: Relating plasma circulation lifetimes to protein binding

The incorporation of poly(ethylene glycol) (PEG)-conjugated lipids in lipid-based carriers substantially prolongs the circulation lifetime of liposomes. However, the mechanism(s) by which PEG-lipids achieve this have not been fully elucidated. It is believed that PEG-lipids mediate steric stabilization, ultimately reducing surface-surface interactions including the aggregation of liposomes and/or adsorption of plasma proteins. The purpose of the studies described here was to compare the effects of PEG-lipid incorporation in liposomes on protein binding, liposome-liposome aggregation and pharmacokinetics in mice. Cholesterol-free liposomes were chosen because of their increasing importance as liposomal delivery systems and their marked sensitivity to protein binding and aggregation. Specifically, liposomes containing various molecular weight PEG-lipids at a variety of molar proportions were analyzed for in vivo clearance, aggregation state (size exclusion chromatography, quasi-elastic light scattering, cryo-transmission and freeze fracture electron microscopy) as well as in vitro and in vivo protein binding. The results indicated that as little as 0.5 mol% of 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE) modified with PEG having a mean molecular weight of 2000 (DSPE-PEG(2000)) substantially increased plasma circulation longevity of liposomes prepared of 1,2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC). Optimal plasma circulation lifetimes could be achieved with 2 mol% DSPE-PEG(2000). At this proportion of DSPE-PEG(2000), the aggregation of DSPC-based liposomes was completely precluded. However, the total protein adsorption and the protein profile was not influenced by the level of DSPE-PEG(2000) in the membrane. These studies suggest that PEG-lipids reduce the in vivo clearance of cholesterol-free liposomal formulations primarily by inhibition of surface interactions, particularly liposome-liposome aggregation.

Characterization of the drug retention and pharmacokinetic properties of liposomal nanoparticles containing dihydrosphingomyelin

The drug retention and circulation lifetime properties of liposomal nanoparticles (LN) containing dihydrosphingomyelin (DHSM) have been investigated. It is shown that replacement of egg sphingomyelin (ESM) by DHSM in sphingomyelin/cholesterol (Chol) (55/45; mol/mol) LN results in substantially improved drug retention properties both in vitro and in vivo. In the case of liposomal formulations of vincristine, for example, the half-times for drug release (T(1/2)) were approximately 3-fold longer for DHSM/Chol LN as compared to ESM/Chol LN, both in vitro and in vivo. Further increases in T(1/2) could be achieved by increasing the drug-to-lipid ratio of the liposomal vincristine formulations. In addition, DHSM/Chol LN also exhibit improved circulation lifetimes in vivo as compared to ESM/Chol LN. For example, the half-time for LN clearance (Tc(1/2)) at a low lipid dose (15 micromol lipid/kg, corresponding to 8 mg lipid/kg body weight) in mice was 3.8 h for ESM/Chol LN compared to 6 h for DHSM/Chol LN. In addition, it is also shown that DHSM/Chol LN exhibit much longer half-times for vincristine release as compared to LN with the "Stealth" lipid composition. It is anticipated that DHSM/Chol LN will prove useful as drug delivery vehicles due to their excellent drug retention and circulation lifetime properties.