Immunoliposomes directed toward VCAM-1 interact specifically with activated endothelial cells--a potential tool for specific drug delivery

VCAM-1 targeted nanocarriers of shRNA-Smad3 mitigate endothelial-to-mesenchymal transition triggered by high glucose concentrations and osteogenic factors in valvular endothelial cells

Endothelial to mesenchymal transition (EndMT) of valvular endothelial cells (VEC) is a key process in the development and progression of calcific aortic valve disease (CAVD). High expression of the Smad3 transcription factor is crucial in the transition process. We hypothesize that silencing Smad3 could hinder EndMT and provide a novel treatment for CAVD. We aimed at developing nanoparticles encapsulating short-hairpin (sh)RNA sequences specific for Smad3 targeted to the aortic valve. We synthesized VCAM-1-targeted lipopolyplexes encapsulating shRNA-Smad3 plasmid (V-LPP/shSmad3) and investigated their potential to reduce the EndMT of human VEC. VEC incubation in a medium containing high glucose concentrations and osteogenic factors (HGOM) triggers EndMT and increased expression of Smad3. Exposed to lipopolyplexes, VEC took up efficiently the V-LPP/shSmad3. The latter reduced the EndMT process in VEC exposed to HGOM by downregulating the expression of αSMA and S100A4 mesenchymal markers and increasing the expression of the CD31 endothelial marker. In vivo, V-LPP/shSmad3 accumulated in the aortic root and aorta of a murine model of atherosclerosis complicated with diabetes, without affecting the liver and kidney function. The results suggest that targeting activated VEC with lipopolyplexes to silence Smad3 could be an effective, novel treatment for CAVD mediated by the EndMT process.

Lipid Nanoparticles for Nucleic Acid Delivery to Endothelial Cells

Endothelial cells play critical roles in circulatory homeostasis and are also the gateway to the major organs of the body. Dysfunction, injury, and gene expression profiles of these cells can cause, or are caused by, prevalent chronic diseases such as diabetes, cardiovascular disease, and cancer. Modulation of gene expression within endothelial cells could therefore be therapeutically strategic in treating longstanding disease challenges. Lipid nanoparticles (LNP) have emerged as potent, scalable, and tunable carrier systems for delivering nucleic acids, making them attractive vehicles for gene delivery to endothelial cells. Here, we discuss the functions of endothelial cells and highlight some receptors that are upregulated during health and disease. Examples and applications of DNA, mRNA, circRNA, saRNA, siRNA, shRNA, miRNA, and ASO delivery to endothelial cells and their targets are reviewed, as well as LNP composition and morphology, formulation strategies, target proteins, and biomechanical factors that modulate endothelial cell targeting. Finally, we discuss FDA-approved LNPs as well as LNPs that have been tested in clinical trials and their challenges, and provide some perspectives as to how to surmount those challenges.

Targeting vascular inflammation through emerging methods and drug carriers

Acute inflammation is a common dangerous component of pathogenesis of many prevalent conditions with high morbidity and mortality including sepsis, thrombosis, acute respiratory distress syndrome (ARDS), COVID-19, myocardial and cerebral ischemia-reperfusion, infection, and trauma. Inflammatory changes of the vasculature and blood mediate the course and outcome of the pathology in the tissue site of insult, remote organs and systemically. Endothelial cells lining the luminal surface of the vasculature play the key regulatory functions in the body, distinct under normal vs. pathological conditions. In theory, pharmacological interventions in the endothelial cells might enable therapeutic correction of the overzealous damaging pro-inflammatory and pro-thrombotic changes in the vasculature. However, current agents and drug delivery systems (DDS) have inadequate pharmacokinetics and lack the spatiotemporal precision of vascular delivery in the context of acute inflammation. To attain this level of precision, many groups design DDS targeted to specific endothelial surface determinants. These DDS are able to provide specificity for desired tissues, organs, cells, and sub-cellular compartments needed for a particular intervention. We provide a brief overview of endothelial determinants, design of DDS targeted to these molecules, their performance in experimental models with focus on animal studies and appraisal of emerging new approaches. Particular attention is paid to challenges and perspectives of targeted therapeutics and nanomedicine for advanced management of acute inflammation.

VCAM-1 Targeted Lipopolyplexes as Vehicles for Efficient Delivery of shRNA-Runx2 to Osteoblast-Differentiated Valvular Interstitial Cells; Implications in Calcific Valve Disease Treatment

Calcific aortic valve disease (CAVD) is a progressive inflammatory disorder characterized by extracellular matrix remodeling and valvular interstitial cells (VIC) osteodifferentiation leading to valve leaflets calcification and impairment movement. Runx2, the master transcription factor involved in VIC osteodifferentiation, modulates the expression of other osteogenic molecules. Previously, we have demonstrated that the osteoblastic phenotypic shift of cultured VIC is impeded by Runx2 silencing using fullerene (C60)-polyethyleneimine (PEI)/short hairpin (sh)RNA-Runx2 (shRunx2) polyplexes. Since the use of polyplexes for in vivo delivery is limited by their instability in the plasma and the non-specific tissue interactions, we designed and obtained targeted, lipid-enveloped polyplexes (lipopolyplexes) suitable for (1) systemic administration and (2) targeted delivery of shRunx2 to osteoblast-differentiated VIC (oVIC). Vascular cell adhesion molecule (VCAM)-1 expressed on the surface of oVIC was used as a target, and a peptide with high affinity for VCAM-1 was coupled to the surface of lipopolyplexes encapsulating C60-PEI/shRunx2 (V-LPP/shRunx2). We report here that V-LPP/shRunx2 lipopolyplexes are cyto- and hemo-compatible and specifically taken up by oVIC. These lipopolyplexes are functional as they downregulate the Runx2 gene and protein expression, and their uptake leads to a significant decrease in the expression of osteogenic molecules (OSP, BSP, BMP-2). These results identify V-LPP/shRunx2 as a new, appropriately directed vehicle that could be instrumental in developing novel strategies for blocking the progression of CAVD using a targeted nanomedicine approach.

Gene regulation of intracellular adhesion molecule-1 (ICAM-1): A molecule with multiple functions

Intracellular adhesion molecule 1 (ICAM-1) is one of the most extensively studied inducible cell adhesion molecules which is responsible for several immune functions like T cell activation, extravasation, inflammation, etc. The molecule is constitutively expressed over the cell surface and is regulated up / down in response to inflammatory mediators like cellular stress, proinflammatory cytokines, viral infection. These stimuli modulate the expression of ICAM-1 primarily through regulating the ICAM-1 gene transcription. On account of the presence of various binding sites for NF-κB, AP-1, SP-1, and many other transcription factors, the architecture of the ICAM-1 promoter become complex. Transcription factors in union with other transcription factors, coactivators, and suppressors promote their assembly in a stereospecific manner on ICAM-1 promoter which mediates ICAM-1 regulation in response to different stimuli. Along with transcriptional regulation, epigenetic modifications also play a pivotal role in controlling ICAM-1 expression on different cell types. In this review, we summarize the regulation of ICAM-1 expression both at the transcriptional as well as post-transcriptional level with an emphasis on transcription factors and signaling pathways involved.

Delivery of Anti-microRNA-712 to Inflamed Endothelial Cells Using Poly(β-amino ester) Nanoparticles Conjugated with VCAM-1 Targeting Peptide

Endothelial cells (ECs) are an important target for therapy in a wide range of diseases, most notably atherosclerosis. Developing efficient nanoparticle (NP) systems that deliver RNA interference (RNAi) drugs specifically to dysfunctional ECs in vivo to modulate their gene expression remains a challenge. To date, several lipid-based NPs are developed and shown to deliver RNAi to ECs, but few of them are optimized to specifically target dysfunctional endothelium. Here, a novel, targeted poly(β-amino ester) (pBAE) NP is demonstrated. This pBAE NP is conjugated with VHPK peptides that target vascular cell adhesion molecule 1 protein, overexpressed on inflamed EC membranes. To test this approach, the novel NPs are used to deliver anti-microRNA-712 (anti-miR-712) specifically to inflamed ECs both in vitro and in vivo, reducing the high expression of pro-atherogenic miR-712. A single administration of anti-miR-712 using the VHPK-conjugated-pBAE NPs in mice significantly reduce miR-712 expression, while preventing the loss of its target gene, tissue inhibitor of metalloproteinase 3 (TIMP3) in inflamed endothelium. miR-712 and TIMP3 expression are unchanged in non-inflamed endothelium. This novel, targeted-delivery platform may be used to deliver RNA therapeutics specifically to dysfunctional endothelium for the treatment of vascular disease.

Anti-Vascular Cell Adhesion Molecule-1 Nanosystems: A Promising Strategy Against Inflammatory Based Diseases

Inflammation underlays the onset and supports the development of several worldwide diffused pathologies, therefore in the last decades inflammatory markers have attracted a great deal of interest as diagnostic and therapeutic targets. Adhesion molecules are membrane proteins expressed by endotheliocytes and leukocytes, acting as mediators in the process of tethering, rolling, firm adhesion and diapedesis that leads the immune cells to reach an inflamed tissue. Among them, the adhesion molecule VCAM-1 has been investigated as a potential target because of its low constitutive expression and easy accessibility on the endothelium. Moreover, VCAM-1 is involved in the early stages of development of several pathologies like, among others, atherosclerosis, cancer, Alzheimer's and Parkinson's diseases, so a diagnostic or therapeutic tool directed to this protein would allow specific detection and efficacious intervention. The availability of monoclonal antibodies against VCAM-1 has recently fostered the development of various targeting technologies potentially suitable for imaging and drug delivery in VCAM-1 overexpressing pathologies. In this review we initially focus on the structure and functions of VCAM-1, giving also a brief overview of antibodies origin, structure and function; then, we summarize some of the VCAM-1 targeting nanosystems based on antibodies, gathered according to the carrier used, for diagnosis or therapeutic treatment of different inflammatory based pathologies.

Detection of Vascular Reactive Oxygen Species in Experimental Atherosclerosis by High-Resolution Near-Infrared Fluorescence Imaging Using VCAM-1-Targeted Liposomes Entrapping a Fluorogenic Redox-Sensitive Probe

Excessive production of reactive oxygen species (ROS) and the ensuing oxidative stress are instrumental in all phases of atherosclerosis. Despite the major achievements in understanding the regulatory pathways and molecular sources of ROS in the vasculature, the specific detection and quantification of ROS in experimental models of disease remain a challenge. We aimed to develop a reliable and straightforward imaging procedure to interrogate the ROS overproduction in the vasculature and in various organs/tissues in atherosclerosis. To this purpose, the cell-impermeant ROS Brite™ 700 (RB700) probe that produces bright near-infrared fluorescence upon ROS oxidation was encapsulated into VCAM-1-targeted, sterically stabilized liposomes (VLp). Cultured human endothelial cells (EC) and macrophages (Mac) were used for in vitro experiments. C57BL6/J and ApoE-/- mice were randomized to receive normal or high-fat, cholesterol-rich diet for 10 or 32 weeks. The mice received a retroorbital injection with fluorescent tagged VLp incorporating RB700 (VLp-RB700). After two hours, the specific signals of the oxidized RB700 and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (NBD-DSPE), inserted into liposome bilayers, were measured ex vivo in the mouse aorta and various organs by high-resolution fluorescent imaging. VLp-RB700 was efficiently taken up by cultured human EC and Mac, as confirmed by fluorescence microscopy and spectrofluorimetry. After systemic administration in atherosclerotic ApoE-/- mice, VLp-RB700 were efficiently concentrated at the sites of aortic lesions, as indicated by the augmented NBD fluorescence. Significant increases in oxidized RB700 signal were detected in the aorta and in the liver and kidney of atherosclerotic ApoE-/- mice. RB700 encapsulation into sterically stabilized VCAM-1-sensitive Lp could be a novel strategy for the qualitative and quantitative detection of ROS in the vasculature and various organs and tissues in animal models of disease. The accurate and precise detection of ROS in experimental models of disease could ease the translation of the results to human pathologies.

Myeloperoxidase: A versatile mediator of endothelial dysfunction and therapeutic target during cardiovascular disease

Myeloperoxidase (MPO) is a prominent mammalian heme peroxidase and a fundamental component of the innate immune response against microbial pathogens. In recent times, MPO has received considerable attention as a key oxidative enzyme capable of impairing the bioactivity of nitric oxide (NO) and promoting endothelial dysfunction; a clinically relevant event that manifests throughout the development of inflammatory cardiovascular disease. Increasing evidence indicates that during cardiovascular disease, MPO is released intravascularly by activated leukocytes resulting in its transport and sequestration within the vascular endothelium. At this site, MPO catalyzes various oxidative reactions that are capable of promoting vascular inflammation and impairing NO bioactivity and endothelial function. In particular, MPO catalyzes the production of the potent oxidant hypochlorous acid (HOCl) and the catalytic consumption of NO via the enzyme's NO oxidase activity. An emerging paradigm is the ability of MPO to also influence endothelial function via non-catalytic, cytokine-like activities. In this review article we discuss the implications of our increasing knowledge of the versatility of MPO's actions as a mediator of cardiovascular disease and endothelial dysfunction for the development of new pharmacological agents capable of effectively combating MPO's pathogenic activities. More specifically, we will (i) discuss the various transport mechanisms by which MPO accumulates into the endothelium of inflamed or diseased arteries, (ii) detail the clinical and basic scientific evidence identifying MPO as a significant cause of endothelial dysfunction and cardiovascular disease, (iii) provide an up-to-date coverage on the different oxidative mechanisms by which MPO can impair endothelial function during cardiovascular disease including an evaluation of the contributions of MPO-catalyzed HOCl production and NO oxidation, and (iv) outline the novel non-enzymatic mechanisms of MPO and their potential contribution to endothelial dysfunction. Finally, we deliver a detailed appraisal of the different pharmacological strategies available for targeting the catalytic and non-catalytic modes-of-action of MPO in order to protect against endothelial dysfunction in cardiovascular disease.

Axial pharmaceutical properties of liposome in cancer therapy: Recent advances and perspectives

Evaluation of axial properties including preparation, surface functionalization, and pharmacokinetics for delivery of pharmacologically active molecules and genes lead to pharmaceutical development of liposome in cancer therapy. Here, analysis of effects of the axial properties of liposome based on cancer treatment modalities as individually and coherently is vital and shows deserving further investigation for the future. In this review, recent progress in the analysis of preparation approaches, optimizing pharmacokinetic parameters, functionalization and targeting improvement and modulation of biological factors and components resulting in a better function of liposome in cancer for drug/gene delivery and immunotherapy are discussed. Here, recent developments on liposome with vaccines and immunoadjuvant carriers, and antigen-carrier system to cancer immunotherapy are introduced.

Selective targeting of nanomedicine to inflamed cerebral vasculature to enhance the blood-brain barrier

Drug targeting to inflammatory brain pathologies such as stroke and traumatic brain injury remains an elusive goal. Using a mouse model of acute brain inflammation induced by local tumor necrosis factor alpha (TNFα), we found that uptake of intravenously injected antibody to vascular cell adhesion molecule 1 (anti-VCAM) in the inflamed brain is >10-fold greater than antibodies to transferrin receptor-1 and intercellular adhesion molecule 1 (TfR-1 and ICAM-1). Furthermore, uptake of anti-VCAM/liposomes exceeded that of anti-TfR and anti-ICAM counterparts by ∼27- and ∼8-fold, respectively, achieving brain/blood ratio >300-fold higher than that of immunoglobulin G/liposomes. Single-photon emission computed tomography imaging affirmed specific anti-VCAM/liposome targeting to inflamed brain in mice. Intravital microscopy via cranial window and flow cytometry showed that in the inflamed brain anti-VCAM/liposomes bind to endothelium, not to leukocytes. Anti-VCAM/LNP selectively accumulated in the inflamed brain, providing de novo expression of proteins encoded by cargo messenger RNA (mRNA). Anti-VCAM/LNP-mRNA mediated expression of thrombomodulin (a natural endothelial inhibitor of thrombosis, inflammation, and vascular leakage) and alleviated TNFα-induced brain edema. Thus VCAM-directed nanocarriers provide a platform for cerebrovascular targeting to inflamed brain, with the goal of normalizing the integrity of the blood-brain barrier, thus benefiting numerous brain pathologies.

Functional Role of VCAM-1 Targeted Flavonoid-Loaded Lipid Nanoemulsions in Reducing Endothelium Inflammation

Citrus flavonoids have well-documented protective effects on cardiovascular system, but the poor water solubility and reduced bioavailability restrict their therapeutic use. We aimed to overcome these limitations and encapsulated naringenin and hesperetin into lipid nanoemulsions (LNs), targeted to vascular cell adhesion molecule-1 (VCAM-1), which is expressed on activated endothelial cells (ECs). LNs were characterized by a hydrodynamic size of ~200 nm, negative zeta potential, an encapsulation efficiency of flavonoids higher than 80%, good in vitro stability and steady release of the cargo. The LNs were neither cytotoxic to human ECs line EA.hy926, nor provoked in vitro lysis of murine erithrocytes. Then, we tested whether these nanoformulations reduce tumor necrosis factor-alpha (TNF-α) induced EC-activation. We found that flavonoid-loaded LNs, either non-targeted or targeted to the endothelium, were taken up by the EA.hy926 cells in a dose-dependent manner, but dependent on TNF-α only in the case of endothelium-targeted LNs. Moreover, these nanoparticles inhibited both the adhesion and transmigration of THP-1 monocytes on/through activated ECs, by mechanisms involving a reduced expression of the pro-inflammatory chemokine monocyte chemotactic protein 1 (MCP-1) and diminished nuclear translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB).

In vitro comparison of liposomal drug delivery systems targeting the oxytocin receptor: a potential novel treatment for obstetric complications

Introduction

Targeted intervention to the uterus has great potential for the treatment of obstetric complications (eg, preterm birth, dysfunctional labor, and postpartum hemorrhage) by improving the effectiveness and safety of therapeutic compounds. In particular, targeting the oxytocin receptor (OTR) is a novel approach for drug delivery to the uterus. The aim of this study was to report the complete data set for the pharmaceutical synthesis and in vitro characterization of PEGylated liposomes conjugated with anti-OTR monoclonal antibodies (OTR-Lipo) or atosiban (ATO-Lipo, OTR antagonist).

Methods

OTR-targeted liposomal platforms composed of 1,2-distearoyl-sn-glycero-2-phosphocholine and cholesterol were prepared according to the method of dried lipid film hydration. Ligands were conjugated with the surface of liposomes using optimized methods to maximize conjugation efficiency. The liposomes were characterized for particle size, ligand conjugation, drug encapsulation, liposome stability, specificity of binding, cellular internalization, mechanistic pathway of cellular uptake, and cellular toxicity.

Results

Both OTR-Lipo and ATO-Lipo showed significant and specific binding to OTRs in a concentration-dependent manner compared to all control groups. There was no significant difference in binding values between OTR-Lipo and ATO-Lipo across all concentrations evaluated. In addition, OTR-Lipo (81.61%±7.84%) and ATO-Lipo (85.59%±8.28%) demonstrated significantly increased cellular internalization in comparison with rabbit IgG immunoliposomes (9.14%±1.71%) and conventional liposomes (4.09%±0.78%) at 2.02 mM phospholipid concentration. Cellular association following liposome incubation at 4.05 mM resulted in similar findings. Evaluation of the mechanistic pathway of cellular uptake indicated that they undergo internalization through both clathrin- and caveolin-mediated mechanisms. Furthermore, cellular toxicity studies have shown no significant effect of both liposomal platforms on cell viability.

Conclusion

This study further supports OTRs as a novel pharmaceutical target for drug delivery. OTR-targeted liposomal platforms may provide an effective way to deliver existing therapies directly to myometrial tissue and avoid adverse effects by circumventing non-target tissues.

Synthesis and in vitro characterization of oxytocin receptor targeted PEGylated immunoliposomes for drug delivery to the uterus

Targeted delivery of therapeutics to the uterus is an important goal in the treatment of obstetric complications, such as preterm labour, postpartum hemorrhage, and dysfunctional labour. Current treatment for these obstetric complications is challenging, as there are limited effective and safe therapeutic options available. We have developed a targeted drug delivery system for the uterus by conjugating anti-oxytocin receptor (OTR) antibodies to the surface of PEGylated liposomes (OTR-PEG-ILs). The functionality of the OTR-PEG-ILs has previously been evaluated on human and murine myometrial tissues as well as in vivo in a murine model of preterm labour. The aim of this study was to report the pharmaceutical synthesis and characterization of the OTR-PEG-ILs and investigate their specific cellular interaction with OTR-expressing myometrial cells in vitro. Immunoliposomes composed of 1,2-distearoyl-sn-glycero-2-phosphocholine (DSPC) and cholesterol were prepared using an optimized method for the coupling of low concentrations of antibody to liposomes. The liposomes were characterized for particle size, antibody conjugation, drug encapsulation, liposome stability, specificity of binding, cellular internalization, mechanistic pathway of cellular uptake, and cellular toxicity. Cellular association studies demonstrated specific binding of OTR-PEG-ILs to OTRs and significant cellular uptake following binding. Evaluation of the mechanistic pathway of cellular uptake indicated that they undergo internalization through both clathrin- and caveolin-mediated mechanisms. Furthermore, cellular toxicity studies have shown no significant effect of OTR-PEG-ILs or the endocytotic inhibitors on cell viability. This study further supports oxytocin receptors as a novel pharmaceutical target for drug delivery to the uterus.

Dual-functional drug liposomes in treatment of resistant cancers

Efficacy of regular chemotherapy is significantly hampered by multidrug resistance (MDR) and severe systemic toxicity. The reduced toxicity has been evidenced after administration of drug liposomes, consisting of the first generation of regular drug liposomes, the second generation of long-circulation drug liposomes, and the third generation of targeting drug liposomes. However, MDR of cancers remains as an unsolved issue. The objective of this article is to review the dual-functional drug liposomes, which demonstrate the potential in overcoming MDR. Herein, dual-functional drug liposomes are referring to the drug-containing phospholipid bilayer vesicles that possess a dual-function of providing the basic efficacy of drug and the extended effect of the drug carrier. They exhibit unique roles in treatment of resistant cancer via circumventing drug efflux caused by adenosine triphosphate binding cassette (ABC) transporters, eliminating cancer stem cells, destroying mitochondria, initiating apoptosis, regulating autophagy, destroying supply channels, utilizing microenvironment, and silencing genes of the resistant cancer. As the prospect of an estimation, dual-functional drug liposomes would exhibit more strength in their extended function, hence deserving further investigation for clinical validation.

Breast cancer metastasis: Putative therapeutic role of vascular cell adhesion molecule-1

BACKGROUND

Breast cancer is a notable cause of cancer-related death in women worldwide. Metastasis to distant organs is responsible for ~90% of this death. Breast cells convert to malignant cancer cells after acquiring the capacity of invasion/intravasation into surrounding tissues and, finally, extravasation/metastasis to distant organs (i.e., lymph nodes, lungs, bone, brain). Metastasis to distant organs depends on interactions between disseminated tumor cells (DTCs) and the endothelium of blood vessels present in the tumor microenvironment. Among several known endothelial adhesion molecules, vascular cell adhesion molecule-1 (VCAM-1) has been found to be involved in this process. It has been shown that VCAM-1 is aberrantly expressed in breast cancer cells and that it can bind to its natural ligand α4β1integrin, also denoted as very late antigen 4 (VLA-4). This binding appears to be responsible for the metastasis of breast cancer cells to lung, bone and brain. The α4β1 integrin - VCAM-1 interaction thus represents a potential therapeutic target for metastatic breast cancer cells. The development of inhibitors of this interaction may be instrumental for the clinical management of breast cancer patients.

CONCLUSIONS

This study focuses on recent progress on the role of VCAM-1, an important glycoprotein belonging to the immunoglobulin (Ig) superfamily of cell surface adhesion molecules in breast cancer angiogenesis, survival and metastasis. Targeting VCAM-1, expressed on the surface of breast cancer cells, and/or its specific ligand VLA-4/α4β1 integrin, expressed on cells at the site of metastasis, may be a useful strategy to reduce breast cancer cell invasion and metastasis. Various approaches to therapeutically target VCAM-1 and VLA-4 are also discussed.

Therapeutically targeting SELF-reinforcing leukemic niches in acute myeloid leukemia: A worthy endeavor?

A tight relationship between the acute myeloid leukemia (AML) population and the bone marrow (BM) microenvironment has been convincingly established. The AML clone contains leukemic stem cells (LSCs) that compete with normal hematopoietic stem cells (HSCs) for niche occupancy and remodel the niche; whereas, the BM microenvironment might promote AML development and progression not only through hypoxia and homing/adhesion molecules, but also through genetic defects. Although it is still unknown whether the niche influences treatment results or contains any potential target for treatment, this dynamic AML-niche interaction might be a promising therapeutic objective to significantly improve the AML cure rate.

Technique for the Characterization of Phospholipid Microbubbles Coatings by Transmission Electron Microscopy

Gas microbubbles stabilized by a surfactant or polymer coating are of considerable clinical interest because of their imaging and drug delivery potential under ultrasound exposure. The utility of microbubbles for a given application is intrinsically linked to their structure and stability. These in turn are highly sensitive to coating composition and fabrication techniques. Various methods including fluorescence and atomic force microscopy have been applied to characterize microbubble properties, but direct observation of coating structure at the nanoscale still poses a considerable challenge. Here we describe a transmission electron microscopy (TEM) technique to observe the surface of microbubbles. Images from a series of phospholipid-coated microbubble systems, including those decorated with nanoparticles, are presented. They indicate that the technique enables visualization of the coating structure, in particular lipid discontinuities and nanoparticle distribution. This information can be used to better understand how microbubble surface structure relates to formulation and/or processing technique and ultimately to functionality.

Multifunctional Nanoparticles Facilitate Molecular Targeting and miRNA Delivery to Inhibit Atherosclerosis in ApoE(-/-) Mice

The current study presents an effective and selective multifunctional nanoparticle used to deliver antiatherogenic therapeutics to inflamed pro-atherogenic regions without off-target changes in gene expression or particle-induced toxicities. MicroRNAs (miRNAs) regulate gene expression, playing a critical role in biology and disease including atherosclerosis. While anti-miRNA are emerging as therapeutics, numerous challenges remain due to their potential off-target effects, and therefore the development of carriers for selective delivery to diseased sites is important. Yet, co-optimization of multifunctional nanoparticles with high loading efficiency, a hidden cationic domain to facilitate lysosomal escape and a dense, stable incorporation of targeting moieties is challenging. Here, we create coated, cationic lipoparticles (CCLs), containing anti-miR-712 (∼1400 molecules, >95% loading efficiency) within the core and with a neutral coating, decorated with 5 mol % of peptide (VHPK) to target vascular cell adhesion molecule 1 (VCAM1). Optical imaging validated disease-specific accumulation as anti-miR-712 was efficiently delivered to inflamed mouse aortic endothelial cells in vitro and in vivo. As with the naked anti-miR-712, the delivery of VHPK-CCL-anti-miR-712 effectively downregulated the d-flow induced expression of miR-712 and also rescued the expression of its target genes tissue inhibitor of metalloproteinase 3 (TIMP3) and reversion-inducing-cysteine-rich protein with kazal motifs (RECK) in the endothelium, resulting in inhibition of metalloproteinase activity. Moreover, an 80% lower dose of VHPK-CCL-anti-miR-712 (1 mg/kg dose given twice a week), as compared with naked anti-miR-712, prevented atheroma formation in a mouse model of atherosclerosis. While delivery of naked anti-miR-712 alters expression in multiple organs, miR-712 expression in nontargeted organs was unchanged following VHPK-CCL-anti-miR-712 delivery.

Nanoengineering of therapeutics for retinal vascular disease

Retinal vascular diseases, including diabetic retinopathy, neovascular age related macular degeneration, and retinal vein occlusion, are leading causes of blindness in the Western world. These diseases share several common disease mechanisms, including vascular endothelial growth factor (VEGF) signaling, hypoxia, and inflammation, which provide opportunities for common therapeutic strategies. Treatment of these diseases using laser therapy, anti-VEGF injections, and/or steroids has significantly improved clinical outcomes. However, these strategies do not address the underlying root causes of pathology, and may have deleterious side effects. Furthermore, many patients continue to progress toward legal blindness despite receiving regular therapy. Nanomedicine, the engineering of therapeutics at the 1-100 nm scale, is a promising approach for improving clinical management of retinal vascular diseases. Nanomedicine-based technologies have the potential to revolutionize the treatment of ophthalmology, through enabling sustained release of drugs over several months, reducing side effects due to specific targeting of dysfunctional cells, and interfacing with currently "undruggable" targets. We will discuss emerging nanomedicine-based applications for the treatment of complications associated with retinal vascular diseases, including angiogenesis and inflammation.

The influence of blood on targeted microbubbles

The ability to successfully target the delivery of drugs and other therapeutic molecules has been a key goal of biomedical research for many decades. Despite highly promising in vitro results, however, successful translation of targeted drug delivery into clinical use has been extremely limited. This study investigates the significance of the characteristics of whole blood, which are rarely accounted for in vitro assays, as a possible explanation for the poor correlation between in vitro and in vivo experiments. It is shown using two separate model systems employing either biochemical or magnetic targeting that blood causes a substantial reduction in targeting efficiency relative to saline under the same flow conditions. This finding has important implications for the design of targeted drug delivery systems and the assays used in their development.

Vascular cell adhesion molecule-1 (VCAM-1)--an increasing insight into its role in tumorigenicity and metastasis

Vascular cell adhesion molecule-1 (VCAM-1) first attracted attention more than two decades ago as endothelial adhesion receptor with key function for leukocyte recruitment in term of cellular immune response. The early finding of VCAM-1 binding to melanoma cells, and thus a suggested mechanistic contribution to metastatic spread, was the first and for a long time the only link of VCAM-1 to cancer sciences. In the last few years, hallmarked by a growing insight into the molecular understanding of tumorigenicity and metastasis, an impressive variety of VCAM-1 functionalities in cancer have been elucidated. The present review aims to provide a current overview of VCAM-1 relevance for tumor growth, metastasis, angiogenesis, and related processes. By illustrating the intriguing role of VCAM-1 in cancer disease, VCAM-1 is suggested as a new and up to now underestimated target in cancer treatment and in clinical diagnosis of malignancies.

VCAM-1 specific PEGylated SAINT-based lipoplexes deliver siRNA to activated endothelium in vivo but do not attenuate target gene expression

In recent years much research in RNA nanotechnology has been directed to develop an efficient and clinically suitable delivery system for short interfering RNA (siRNA). The current study describes the in vivo siRNA delivery using PEGylated antibody-targeted SAINT-based-lipoplexes (referred to as antibody-SAINTPEGarg/PEG2%), which showed superior siRNA delivery capacity and effective down-regulation of VE-cadherin gene expression in vitro in inflammation-activated primary endothelial cells of different vascular origins. PEGylation of antibody-SAINTPEGarg resulted in more desirable pharmacokinetic behavior than that of non-PEGylated antibody-SAINTPEGarg. To create specificity for inflammation-activated endothelial cells, antibodies against vascular cell adhesion molecule-1 (VCAM-1) were employed. In TNFα-challenged mice, these intravenously administered anti-VCAM-1-SAINTPEGarg/PEG2% homed to VCAM-1 protein expressing vasculature. Confocal laser scanning microscopy revealed that anti-VCAM-1-SAINTPEGarg/PEG2% co-localized with endothelial cells in lung postcapillary venules. Furthermore, they did not exert any liver and kidney toxicity. Yet, lack of in vivo gene silencing as assessed in whole lung and in laser microdissected lung microvascular segments indicates that in vivo internalization and/or intracellular trafficking of the delivery system and its cargo in the target cells are not sufficient, and needs further attention, emphasizing the essence of evaluating siRNA delivery systems in an appropriate in vivo animal model at an early stage in their development.

Effective siRNA delivery to inflamed primary vascular endothelial cells by anti-E-selectin and anti-VCAM-1 PEGylated SAINT-based lipoplexes

The endothelium represents an attractive therapeutic target due to its pivotal role in many diseases including chronic inflammation and cancer. Small interfering RNAs (siRNAs) specifically interfere with the expression of target genes and are considered an important new class of therapeutics. However, due to their size and charge, siRNAs do not spontaneously enter unperturbed endothelial cells (EC). To overcome this problem, we developed novel lipoplexes for siRNA delivery that are based on the cationic amphiphilic lipid SAINT-C18. Antibodies recognizing disease induced cell adhesion molecules were employed to create cell specificity resulting in so-called antibody-SAINTargs. To improve particle stability, antibody-SAINTargs were further optimized for EC-specific siRNA-mediated gene silencing by addition of polyethylene glycol (PEG). Although PEGylated antibody-SAINTargs maintained specificity, they lost their siRNA delivery capacity. Coupling of antibodies to the distal end of PEG (so-called antibody-SAINTPEGargs), resulted in anti-E-selectin- and anti-vascular cell adhesion molecule (VCAM)-1-SAINTPEGarg that preserved their antigen recognition and their capability to specifically deliver siRNA into inflammation-activated primary endothelial cells. The enhanced uptake of siRNA by antibody-SAINTPEGargs was followed by improved silencing of the target gene VE-cadherin, demonstrating that antibody-SAINTPEGargs were capable of functionally delivering siRNA into primary endothelial cells originating from different vascular beds. In conclusion, the newly developed, physicochemically stable, and EC-specific siRNA carrying antibody-SAINTPEGargs selectively down-regulate target genes in primary endothelial cells that are generally difficult to transfect.

Targeting sites of inflammation: intercellular adhesion molecule-1 as a target for novel inflammatory therapies

Targeted drug delivery to sites of inflammation will provide effective, precise, and safe therapeutic interventions for treatment of diverse disease conditions, by limiting toxic side effects and/or increasing drug action. Disease-site targeting is believed to play a major role in the enhanced efficacy observed for a variety of drugs when formulated inside lipid vesicles. This article will focus on the factors and mechanisms involved in drug targeting to sites of inflammation and the importance of cell adhesion molecules, in particular intercellular adhesion molecule-1, in this process.

Inflammation in atherosclerosis: a cause or a result of vascular disorders?

Sound data support the concept that in atherosclerosis, inflammation and dyslipidemia intersect each other and that irrespective of the initiator, both participate from the early stages to the ultimate fate of the atheromatous plaque. The two partakers manoeuvre a vicious circle in atheroma formation: dyslipidaemia triggers an inflammatory process and inflammation elicits dyslipidaemia. Independent of the initial cause, the atherosclerotic lesions occur focally, in particular arterial-susceptible sites, by a process that, although continuous, can be arbitrarily divided into a sequence of consecutive stages that lead from fatty streak to the fibro-lipid plaque and ultimately to plaque rupture and thrombosis. In the process, the initial event is a change in endothelial cells (EC) constitutive properties. Then, the molecular alarm signals send by dysfunctional EC are decoded by specific blood immune cells (monocytes, T lymphocytes, neutrophils, mast cells) and by the resident vascular cells, that respond by initiating a robust inflammatory process, in which the cells and the factors they secrete hasten the atheroma development. Direct and indirect crosstalk between the cells housed within the nascent plaque, complemented by the increase in risk factors of atherosclerosis lead to atheroma development and outcome. The initial inflammatory response can be regarded as a defense/protective reaction mechanism, but its further amplification, speeds up atherosclerosis. In this review, we provide an overview on the role of inflammation and dyslipidaemia and their intersection in atherogenesis. The data may add to the foundation of a novel attitude in the diagnosis and treatment of atherosclerosis.

Molecular targeting of liposomal nanoparticles to tumor microenvironment

Liposomes are biodegradable and can be used to deliver drugs at a much higher concentration in tumor tissues than in normal tissues. Both passive and active drug delivery by liposomal nanoparticles can significantly reduce the toxic side effects of anticancer drugs and enhance the therapeutic efficacy of the drugs delivered. Active liposomal targeting to tumors is achieved by recognizing specific tumor receptors through tumor-specific ligands or antibodies coupled onto the surface of the liposomes, or by stimulus-sensitive drug carriers such as acid-triggered release or enzyme-triggered drug release. Tumors are often composed of tumor cells and nontumor cells, which include endothelial cells, pericytes, fibroblasts, stromal, mesenchymal cells, innate, and adaptive immune cells. These nontumor cells thus form the tumor microenvironment, which could be targeted and modified so that it is unfavorable for tumor cells to grow. In this review, we briefly summarized articles that had taken advantage of liposomal nanoparticles as a carrier to deliver anticancer drugs to the tumor microenvironment, and how they overcame obstacles such as nonspecific uptake, interaction with components in blood, and toxicity. Special attention is devoted to the liposomal targeting of anticancer drugs to the endothelium of tumor neovasculature, tumor associated macrophages, fibroblasts, and pericytes within the tumor microenvironment.

Targeted polymeric therapeutic nanoparticles: design, development and clinical translation

Polymeric materials have been used in a range of pharmaceutical and biotechnology products for more than 40 years. These materials have evolved from their earlier use as biodegradable products such as resorbable sutures, orthopaedic implants, macroscale and microscale drug delivery systems such as microparticles and wafers used as controlled drug release depots, to multifunctional nanoparticles (NPs) capable of targeting, and controlled release of therapeutic and diagnostic agents. These newer generations of targeted and controlled release polymeric NPs are now engineered to navigate the complex in vivo environment, and incorporate functionalities for achieving target specificity, control of drug concentration and exposure kinetics at the tissue, cell, and subcellular levels. Indeed this optimization of drug pharmacology as aided by careful design of multifunctional NPs can lead to improved drug safety and efficacy, and may be complimentary to drug enhancements that are traditionally achieved by medicinal chemistry. In this regard, polymeric NPs have the potential to result in a highly differentiated new class of therapeutics, distinct from the original active drugs used in their composition, and distinct from first generation NPs that largely facilitated drug formulation. A greater flexibility in the design of drug molecules themselves may also be facilitated following their incorporation into NPs, as drug properties (solubility, metabolism, plasma binding, biodistribution, target tissue accumulation) will no longer be constrained to the same extent by drug chemical composition, but also become in-part the function of the physicochemical properties of the NP. The combination of optimally designed drugs with optimally engineered polymeric NPs opens up the possibility of improved clinical outcomes that may not be achievable with the administration of drugs in their conventional form. In this critical review, we aim to provide insights into the design and development of targeted polymeric NPs and to highlight the challenges associated with the engineering of this novel class of therapeutics, including considerations of NP design optimization, development and biophysicochemical properties. Additionally, we highlight some recent examples from the literature, which demonstrate current trends and novel concepts in both the design and utility of targeted polymeric NPs (444 references).

Liposomes for cardiovascular targeting

Liposome-based pharmaceuticals used within the cardiovascular system are reviewed in this article. The delivery of diagnostic and therapeutic agents by plain liposomes and liposomes with surface-attached targeting antibodies or polyethylene glycol to prolong their circulation time and accumulation at vascular injuries, ischemic zones or sites of thrombi are also discussed. An overview of the advantages and disadvantages of liposome-mediated in vitro, ex vivo and in vivo targeting is presented, including discussion of the targeting of liposomes to pathological sites on the blood vessel wall and a description of liposomes that can be internalized by endothelial cells. Diagnostic liposomes used to target myocardial infarction and the relative importance of liposome size, targetability of immunoliposomes and prolonged circulation time on the efficiency of sealing hypoxia-induced plasma membrane damage to cardiocytes are discussed as a promising approach for therapy. The progress in the use of targeted liposomal plasmids for the transfection of hypoxic cardiomyocytes and myocardium is presented. Stent-mediated liposomal-based drug delivery is also reviewed briefly.

Complementary targeting of liposomes to IL-1α and TNF-α activated endothelial cells via the transient expression of VCAM1 and E-selectin

Inflammation is in part defined by the transient upregulation of cell adhesion molecules on the surface of endothelial cells (ECs) in response to cytokines. We hypothesized that liposomes with a complementary surface presentation of antibodies to the pattern of molecules on the EC surface may enhance targeting. We quantified the expression of vascular cell adhesion molecule-1 (VCAM1) and endothelial leukocyte cell adhesion molecule-1 (E-selectin) on ECs upon exposure to either tumor necrosis factor-α (TNF-α) or interleukin-1α (IL-1α) as a function of time. Liposomes, composed of 95 mol% dioleoyl phosphatidylcholine (DOPC) and 5 mol% dodecanyl phosphatidylethanolamine (N-dod-PE), were prepared by conjugating different molar ratios of antibodies against VCAM1 (aVCAM1) and E-selectin (aE-selectin). Increased binding was observed when immunoliposomes complemented the presentation of VCAM1:E-selectin expressed on TNF-α activated ECs. The 1:1 aVCAM1:aE-selectin liposomes had maximal binding at both 6 and 24 h on IL-1α activated ECs due to differences in molecular organization. The results demonstrate that liposomes targeting to inflamed endothelium may be optimized by exploiting the dynamic expression of VCAM1 and E-selectin on the EC surface.

Inflamed leukocyte-mimetic nanoparticles for molecular imaging of inflammation

Dysregulated host inflammatory response causes many diseases, including cardiovascular and neurodegenerative diseases, cancer, and sepsis. Sensitive detection of the site of inflammation will, therefore, produce a wide-ranging impact on disease diagnosis and treatment. We hypothesized that nanoprobes designed to mimic the molecular interactions occurring between inflamed leukocytes and endothelium may possess selectivity toward diverse host inflammatory responses. To incorporate inflammation-sensitive molecular interactions, super paramagnetic iron oxide nanoparticles were conjugated with integrin lymphocyte function-associated antigen (LFA)-1 I domain, engineered to mimic activated leukocytes in physiology. Whole body optical and magnetic resonance imaging in vivo revealed that leukocyte-mimetic nanoparticles localized preferentially to the vasculature within and in the invasive front of the tumor, as well as to the site of acute inflammation. This study explored in vivo detection of tumor-associated vasculature with systemically injected inflammation-specific nanoparticles, presenting a possibility of tumor detection by inflamed tumor microenvironment.

Receptor-targeted nanocarriers for therapeutic delivery to cancer

Efficient and site-specific delivery of therapeutic drugs is a critical challenge in clinical treatment of cancer. Nano-sized carriers such as liposomes, micelles, and polymeric nanoparticles have been investigated for improving bioavailability and pharmacokinetic properties of therapeutics via various mechanisms, for example, the enhanced permeability and retention (EPR) effect. Further improvement can potentially be achieved by conjugation of targeting ligands onto nanocarriers to achieve selective delivery to the tumour cell or the tumour vasculature. Indeed, receptor-targeted nanocarrier delivery has been shown to improve therapeutic responses both in vitro and in vivo. A variety of ligands have been investigated including folate, transferrin, antibodies, peptides and aptamers. Multiple functionalities can be incorporated into the design of nanoparticles, e.g., to enable imaging and triggered intracellular drug release. In this review, we mainly focus on recent advances on the development of targeted nanocarriers and will introduce novel concepts such as multi-targeting and multi-functional nanoparticles.

Dynamic and cellular interactions of nanoparticles in vascular-targeted drug delivery

Vascular-targeted drug delivery systems could provide more efficient and effective pharmaceutical interventions for treating a variety of diseases including cardiovascular, pulmonary, inflammatory, and malignant disorders. However, several factors must be taken into account when designing these systems. The diverse blood hemodynamics and rheology, and the natural clearance process that tend to decrease the circulation time of foreign particles all lessen the probability of successful carrier interaction with the vascular wall. An effective vascular-targeted drug delivery system must be able to navigate through the bloodstream while avoiding immune clearance, attach to the vascular wall, and release its therapeutic cargo at the intended location. This review will summarize and analyze current literature reporting on (1) nanocarrier fabrication methods and materials that allow for optimum therapeutic encapsulation, protection, and release; (2) localization and binding dynamics of nanocarriers as influenced by hemodynamics and blood rheology in medium-to-large vessels; (3) blood cells' responses to various types of nanocarrier compositions and its effects on particle circulation time; and (4) properties that affect nanocarrier internalization at the target site.

Dynamic and cellular interactions of nanoparticles in vascular-targeted drug delivery (review)

Vascular-targeted drug delivery systems could provide more efficient and effective pharmaceutical interventions for treating a variety of diseases including cardiovascular, pulmonary, inflammatory, and malignant disorders. However, several factors must be taken into account when designing these systems. The diverse blood hemodynamics and rheology, and the natural clearance process that tend to decrease the circulation time of foreign particles all lessen the probability of successful carrier interaction with the vascular wall. An effective vascular-targeted drug delivery system must be able to navigate through the bloodstream while avoiding immune clearance, attach to the vascular wall, and release its therapeutic cargo at the intended location. This review will summarize and analyze current literature reporting on (1) nanocarrier fabrication methods and materials that allow for optimum therapeutic encapsulation, protection, and release; (2) localization and binding dynamics of nanocarriers as influenced by hemodynamics and blood rheology in medium-to-large vessels; (3) blood cells' responses to various types of nanocarrier compositions and its effects on particle circulation time; and (4) properties that affect nanocarrier internalization at the target site.

Targeting of ICAM-1-directed immunoliposomes specifically to activated endothelial cells with low cellular uptake: use of an optimized procedure for the coupling of low concentrations of antibody to liposomes

Targeted delivery of therapeutics to the endothelium is an important goal in the treatment of inflammatory diseases. The aim of this work was to exploit the overexpression of intercellular adhesion molecule-1 (ICAM-1) on activated endothelial cells for the targeting of anti-ICAM-1-coupled immunoliposomes with the intent for further use as drug carriers. Immunoliposomes were prepared from using an optimized method for the coupling of low concentrations of antibody to liposomes, thereby preventing the loss of antibody through the derivatization, extraction, and activation process. This is especially suitable for limiting ligand conjugates that are isolated or synthesized in small quantities, such as monoclonal antibodies (mAbs). To investigate the functionality of the resulting immunoliposomes, the specificity of binding and cellular internalization studies of liposomes, either nonconjugated or conjugated with mAbs to ICAM-1 or to irrelevant IgG to high endothelial venule (HEV) cells, were analyzed by fluorescence microplate spectroscopy at 4 and 37°C. Immunoliposomes specifically directed against ICAM-1 were shown to bind selectively and specifically to tumor necrosis factor alpha-activated endothelial cells in vitro, with minimal cellular internalization. This study provides a novel delivery system that has the potential for targeting therapeutics to inflammatory tissue.

Recent advances in tumor vasculature targeting using liposomal drug delivery systems

Tumor vessels possess unique physiological features that might be exploited for improved drug delivery. The targeting of liposomal anticancer drugs to tumor vasculature is increasingly recognized as an effective strategy to obtain superior therapeutic efficacy with limited host toxicity compared with conventional treatments. This review introduces recent advances in the field of liposomal targeting of tumor vasculature, along with new approaches that can be used in the design and optimization of liposomal delivery systems. In addition, cationic liposome is focused on as a promising carrier for achieving efficient vascular targeting. The clinical implications are discussed of several approaches using a single liposomal anticancer drug formulation: dual targeting, vascular targeting (targeting tumor endothelial cells) and tumor targeting (targeting tumor cells).

Flow dynamics, binding and detachment of spherical carriers targeted to ICAM-1 on endothelial cells

Vascular drug delivery by administration of carriers targeted to endothelial surface determinants, such as intercellular adhesion molecule (ICAM-1), holds considerable promise to improve disease treatment. As a model to define elusive factors controlling the interplay between carrier motion in the bloodstream and its interactions with molecular targets in the endothelial wall, we used 1 mum beads coated with ICAM-1 monoclonal antibody (Ab) at 370, 1100 or 4100 Ab/microm2. Carriers were perfused at two shear rates over resting or activated endothelial cells, expressing minimum vs. maximum ICAM-1 levels, to determine carrier rolling, binding and detachment. Even at 0.1 Pa and 4100 Ab/microm2, carriers attached only to activated cells (21 fold increase over resting cells), ideal for specific drug targeting to sites of pathology. Binding was increased by raising the Ab surface density on the carrier, e.g., 59.4+/-11.1% increase for carriers having 4100 vs. 1100 Ab/microm2, as a consequence of decreased rolling velocity. Carrier binding was stable even under a high shear stress: carriers with 1100 and 4100 Ab/microm2 withstand shear stress over 3 Pa without detaching from the cells. This is further supported by theoretical modeling. These results will guide vascular targeting of drug carriers via rational design of experimentally tunable parameters.

Passive and active drug targeting: drug delivery to tumors as an example

The paradigm of using nanoparticulate pharmaceutical carriers has been well established over the past decade, both in pharmaceutical research and in the clinical setting. Drug carriers are expected to stay in the blood for long time, accumulate in pathological sites with affected and leaky vasculature (tumors, inflammations, and infarcted areas) via the enhanced permeability and retention (EPR) effect, and facilitate targeted delivery of specific ligand-modified drugs and drug carriers into poorly accessible areas. Among various approaches to specifically target drug-loaded carrier systems to required pathological sites in the body, two seem to be most advanced--passive (EPR effect-mediated) targeting, based on the longevity of the pharmaceutical carrier in the blood and its accumulation in pathological sites with compromised vasculature, and active targeting, based on the attachment of specific ligands to the surface of pharmaceutical carriers to recognize and bind pathological cells. Here, we will consider and discuss these two targeting approaches using tumor targeting as an example.

Lipid-based nanoparticles as pharmaceutical drug carriers: from concepts to clinic

In recent years, various nanotechnology platforms in the area of medical biology, including both diagnostics and therapy, have gained remarkable attention. Moreover, research and development of engineered multifunctional nanoparticles as pharmaceutical drug carriers have spurred exponential growth in applications to medicine in the last decade. Design principles of these nanoparticles, including nanoemulsions, dendrimers, nano-gold, liposomes, drug-carrier conjugates, antibody-drug complexes, and magnetic nanoparticles, are primarily based on unique assemblies of synthetic, natural, or biological components, including but not limited to synthetic polymers, metal ions, oils, and lipids as their building blocks. However, the potential success of these particles in the clinic relies on consideration of important parameters such as nanoparticle fabrication strategies, their physical properties, drug loading efficiencies, drug release potential, and, most importantly, minimum toxicity of the carrier itself. Among these, lipid-based nanoparticles bear the advantage of being the least toxic for in vivo applications, and significant progress has been made in the area of DNA/RNA and drug delivery using lipid-based nanoassemblies. In this review, we will primarily focus on the recent advances and updates on lipid-based nanoparticles for their projected applications in drug delivery. We begin with a review of current activities in the field of liposomes (the so-called honorary nanoparticles), and challenging issues of targeting and triggering will be discussed in detail. We will further describe nanoparticles derived from a novel class of amphipathic lipids called bolaamphiphiles with unique lipid assembly features that have been recently examined as drug/DNA delivery vehicles. Finally, an overview of an emerging novel class of particles (based on lipid components other than phospholipids), solid lipid nanoparticles and nanostructured lipid carriers will be presented. We conclude with a few examples of clinically successful formulations of currently available lipid-based nanoparticles.