Templated spherical high density lipoprotein nanoparticles

Radiolabeling lipoproteins to study and manage disease

PURPOSE

Lipoproteins are endogenous nanoparticles with essential roles in lipid transport and inflammation. Lipoproteins are also valuable in diagnosing and treating disease. For instance, certain lipoproteins are overexpressed in patients with atherosclerotic cardiovascular disease, and reconstituted lipoproteins have been extensively used for drug delivery. Radiolabeling has proven an especially powerful approach for studying and therapeutically exploiting lipoproteins. This review details how radiochemistry and nuclear imaging can facilitate the study of lipoproteins in health and disease. Among other topics, we discuss approaches for radiolabeling lipoproteins and detail how these have helped advance our understanding of lipoprotein biology and the diagnosis and treatment of diseases, including atherosclerosis, cancer, and hypercholesteremia.

METHODS

We performed an extensive literature search on all peer-reviewed studies involving radiolabeled lipoproteins and selected representative examples to provide a high-level overview of the most important discoveries and technological advancements.

RESULTS

More than 200 peer-reviewed papers involved radiolabeled lipoproteins, spanning mechanistic, diagnostic, and therapeutic studies across a wide range of diseases.

CONCLUSION

Radiolabeling has been critical in advancing our understanding of lipoprotein biology and leveraging these nanomaterials for diagnosing and treating disease.

Keratinocyte SR-B1 expression and targeting in cytokine-driven skin inflammation

BACKGROUND

Strategies to treat inflammatory skin conditions require identifying new targets involved in interactions between overlying epithelial and underlying dermal immune cells. Scavenger receptor class B type 1 (SR-B1) is a cell surface receptor that binds high-density lipoproteins (HDL) and mediates inflammatory responses in immune and endothelial cells. The SR-B1 receptor is also expressed in keratinocytes, but its role in inflammatory skin diseases remains unexplored.

METHODS

To investigate keratinocyte SR-B1 in the setting of inflammation, we measured its expression in skin biopsy samples obtained from patients with psoriasis; human skin explants exposed to the inflammatory cytokine, interleukin-17A (IL-17A); and mouse skin exposed to the pro-inflammatory agent, imiquimod (IMQ). We also evaluated the effects of SR-B1 knockdown on primary keratinocyte responses to IL-17A. Finally, we employed a synthetic HDL-nanoparticle (HDL NP) to investigate the therapeutic potential of targeting SR-B1 in IL-17A-stimulated keratinocytes and in male C57BL/6 mice with IMQ-induced skin inflammation.

RESULTS

Our data show SR-B1 expression is increased in diseased human skin and in both human and mouse models of skin inflammation. SR-B1 knockdown in keratinocytes exacerbates the inflammatory response to IL-17A, whereas targeting SR-B1 with HDL NP attenuates this response. In the IMQ murine model, topical application of HDL NPs improves the skin phenotype, normalizes SR-B1 expression, and reduces molecular and cellular markers of inflammation.

CONCLUSIONS

Overall, SR-B1 plays a role in skin inflammation and HDL NP-mediated targeting of SR-B1 in keratinocytes may offer a targeted new therapy for inflammatory skin disease.

Encapsulation and Delivery of the Kinase Inhibitor PIK-75 by Organic Core High-Density Lipoprotein-Like Nanoparticles Targeting Scavenger Receptor Class B Type 1

PIK-75 (F7) is a potent multikinase inhibitor that targets p110α, DNA-PK, and p38γ. PIK-75 has shown potential as a therapy in preclinical cancer models, but it has not been used in the clinic, at least in part, due to limited solubility. We therefore developed a nanoparticle to encapsulate PIK-75 and enable targeted cellular delivery. Scavenger receptor class B type 1 (SR-B1) is often overexpressed in cancer compared with normal cells, which enables targeting by synthetic lipid nanoparticles with some features of native high-density lipoprotein (HDL), the natural ligand of SR-B1. We investigated the use of organic core (oc) molecular platforms to synthesize HDL-like nanoparticles (oc-HDL NP). Employing an oc, we successfully formulated PIK-75 into oc-HDL NPs. The PIK-75 loaded oc-HDL NP (PIK-75 oc-HDL NP), comprising ∼20 PIK-75 molecules/NP, has similar size, surface charge, and surface composition as oc-HDL NP and natural human HDL. Using prostate cancer (PCa) and cutaneous T-cell lymphoma (CTCL) models known to be sensitive to inhibitors of p110α and p38γ, respectively, we found that PIK-75 oc-HDL NPs specifically targeted SR-B1 to deliver PIK-75 and potently induced cell death in vitro in PCa and CTCL and in vivo in a murine PCa model. Additionally, we found that PIK-75 oc-HDL NP, but not free PIK-75 or oc-HDL NP alone, reduced the IC50 in the NCI-60 cell line panel and additional pancreatic cancer cell lines. These data demonstrate the first example of drug-loaded oc-HDL NP that actively target SR-B1 and kill cancer cells in vitro and in vivo, encouraging further development and translation to human patients.

Nanoparticle Targeting in Chemo-Resistant Ovarian Cancer Reveals Dual Axis of Therapeutic Vulnerability Involving Cholesterol Uptake and Cell Redox Balance

Platinum (Pt)-based chemotherapy is the main treatment for ovarian cancer (OC); however, most patients develop Pt resistance (Pt-R). This work shows that Pt-R OC cells increase intracellular cholesterol through uptake via the HDL receptor, scavenger receptor type B-1 (SR-B1). SR-B1 blockade using synthetic cholesterol-poor HDL-like nanoparticles (HDL NPs) diminished cholesterol uptake leading to cell death and inhibition of tumor growth. Reduced cholesterol accumulation in cancer cells induces lipid oxidative stress through the reduction of glutathione peroxidase 4 (GPx4) leading to ferroptosis. In turn, GPx4 depletion induces decreased cholesterol uptake through SR-B1 and re-sensitizes OC cells to Pt. Mechanistically, GPx4 knockdown causes lower expression of the histone acetyltransferase EP300, leading to reduced deposition of histone H3 lysine 27 acetylation (H3K27Ac) on the sterol regulatory element binding transcription factor 2 (SREBF2) promoter and suppressing expression of this key transcription factor involved in the regulation of cholesterol metabolism. SREBF2 downregulation leads to decreased SR-B1 expression and diminished cholesterol uptake. Thus, chemoresistance and cancer cell survival under high ROS burden obligates high GPx4 and SR-B1 expression through SREBF2. Targeting SR-B1 to modulate cholesterol uptake inhibits this axis and causes ferroptosis in vitro and in vivo in Pt-R OC.

Regulating Cholesterol in Tumorigenesis: A Novel Paradigm for Tumor Nanotherapeutics

During the past decade, "membrane lipid therapy", which involves the regulation of the structure and function of tumor cell plasma membranes, has emerged as a new strategy for cancer treatment. Cholesterol is an important component of the tumor plasma membrane and serves an essential role in tumor initiation and progression. This review elucidates the role of cholesterol in tumorigenesis (including tumor cell proliferation, invasion/metastasis, drug resistance, and immunosuppressive microenvironment) and elaborates on the potential therapeutic targets for tumor treatment by regulating cholesterol. More meaningfully, this review provides an overview of cholesterol-integrated membrane lipid nanotherapeutics for cancer therapy through cholesterol regulation. These strategies include cholesterol biosynthesis interference, cholesterol uptake disruption, cholesterol metabolism regulation, cholesterol depletion, and cholesterol-based combination treatments. In summary, this review demonstrates the tumor nanotherapeutics based on cholesterol regulation, which will provide a reference for the further development of "membrane lipid therapy" for tumors.

mRNA vaccine in gastrointestinal tumors: Immunomodulatory effects and immunotherapy

Gastrointestinal tumors remain a significant healthcare burden worldwide, necessitating the development of innovative therapeutic strategies. mRNA vaccines have emerged as a promising approach in cancer immunotherapy, harnessing the immune system's potential to recognize and eliminate tumor cells. mRNA vaccines offer several advantages, including their ability to elicit both innate and adaptive immune responses, ease of production, and adaptability to different tumor types. In the context of gastrointestinal tumors, mRNA vaccines hold great potential as a therapeutic strategy. In this review, we will delve into the immunomodulatory mechanisms and immunotherapy strategies of mRNA vaccines in gastrointestinal tumors. Additionally, we will discuss the challenges and ongoing research efforts in optimizing mRNA vaccine development, delivery, and stability. By understanding the potential of mRNA vaccines in addressing the unmet medical need of gastrointestinal tumors, we aim to pave the way for improved treatment strategies and better patient outcomes.

Recent Advancement in mRNA Vaccine Development and Applications

Messenger RNA (mRNA) vaccine development for preventive and therapeutic applications has evolved rapidly over the last decade. The mRVNA vaccine has proven therapeutic efficacy in various applications, including infectious disease, immunotherapy, genetic disorders, regenerative medicine, and cancer. Many mRNA vaccines have made it to clinical trials, and a couple have obtained FDA approval. This emerging therapeutic approach has several advantages over conventional methods: safety; efficacy; adaptability; bulk production; and cost-effectiveness. However, it is worth mentioning that the delivery to the target site and in vivo degradation and thermal stability are boundaries that can alter their efficacy and outcomes. In this review, we shed light on different types of mRNA vaccines, their mode of action, and the process to optimize their development and overcome their limitations. We also have explored various delivery systems focusing on the nanoparticle-mediated delivery of the mRNA vaccine. Generally, the delivery system plays a vital role in enhancing mRNA vaccine stability, biocompatibility, and homing to the desired cells and tissues. In addition to their function as a delivery vehicle, they serve as a compartment that shields and protects the mRNA molecules against physical, chemical, and biological activities that can alter their efficiency. Finally, we focused on the future considerations that should be attained for safer and more efficient mRNA application underlining the advantages and disadvantages of the current mRNA vaccines.

Engineered rHDL Nanoparticles as a Suitable Platform for Theranostic Applications

Reconstituted high-density lipoproteins (rHDLs) can transport and specifically release drugs and imaging agents, mediated by the Scavenger Receptor Type B1 (SR-B1) present in a wide variety of tumor cells, providing convenient platforms for developing theranostic systems. Usually, phospholipids or Apo-A1 lipoproteins on the particle surfaces are the motifs used to conjugate molecules for the multifunctional purposes of the rHDL nanoparticles. Cholesterol has been less addressed as a region to bind molecules or functional groups to the rHDL surface. To maximize the efficacy and improve the radiolabeling of rHDL theranostic systems, we synthesized compounds with bifunctional agents covalently linked to cholesterol. This strategy means that the radionuclide was bound to the surface, while the therapeutic agent was encapsulated in the lipophilic core. In this research, HYNIC-S-(CH2)3-S-Cholesterol and DOTA-benzene-p-SC-NH-(CH2)2-NH-Cholesterol derivatives were synthesized to prepare nanoparticles (NPs) of HYNIC-rHDL and DOTA-rHDL, which can subsequently be linked to radionuclides for SPECT/PET imaging or targeted radiotherapy. HYNIC is used to complexing 99mTc and DOTA for labeling molecules with 111, 113mIn, 67, 68Ga, 177Lu, 161Tb, 225Ac, and 64Cu, among others. In vitro studies showed that the NPs of HYNIC-rHDL and DOTA-rHDL maintain specific recognition by SR-B1 and the ability to internalize and release, in the cytosol of cancer cells, the molecules carried in their core. The biodistribution in mice showed a similar behavior between rHDL (without surface modification) and HYNIC-rHDL, while DOTA-rHDL exhibited a different biodistribution pattern due to the significant reduction in the lipophilicity of the modified cholesterol molecule. Both systems demonstrated characteristics for the development of suitable theranostic platforms for personalized cancer treatment.

Advancements in cell membrane camouflaged nanoparticles: A bioinspired platform for cancer therapy

The idea of employing natural cell membranes as a coating medium for nanoparticles (NPs) endows man-made vectors with natural capabilities and benefits. In addition to retaining the physicochemical characteristics of the NPs, the biomimetic NPs also have the functionality of source cell membranes. It has emerged as a promising approach to enhancing the properties of NPs for drug delivery, immune evasion, imaging, cancer-targeting, and phototherapy sensitivity. Several studies have been reported with a multitude of approaches to reengineering the surface of NPs using biological membranes. Owing to their low immunogenicity and intriguing biomimetic properties, cell-membrane-based biohybrid delivery systems have recently gained a lot of interest as therapeutic delivery systems. This review summarises different kinds of biomimetic NPs reported so far, their fabrication aspects, and their application in the biomedical field. Finally, it briefs on the latest advances available in this biohybrid concept.

The Functional Role of Lipoproteins in Atherosclerosis: Novel Directions for Diagnosis and Targeting Therapy

Dyslipidemia, characterized by a high level of lipids (cholesterol, triglycerides, or both), can increase the risk of developing and progressing atherosclerosis. As atherosclerosis progresses, the number and severity of aterial plagues increases with greater risk of myocardial infarction, a major contributor to cardiovascular mortality. Atherosclerosis progresses in four phases, namely endothelial dysfunction, fatty streak formation, lesion progression and plaque rupture, and eventually thrombosis and arterial obstruction. With greater understanding of the pathological processes underlying atherosclerosis, researchers have identified that lipoproteins play a significant role in the development of atherosclerosis. In particular, apolipoprotein B (apoB)-containing lipoproteins have been shown to associate with atherosclerosis. Oxidized low-density lipoproteins (ox-LDLs) also contribute to the progression of atherosclerosis whereas high-density lipoproteins (HDL) contribute to the removal of cholesterol from macrophages thereby inhibiting the formation of foam cells. Given these known associations, lipoproteins may have potential as biomarkers for predicting risk associated with atherosclerotic plaques or may be targets as novel therapeutic agents. As such, the rapid development of drugs targeting lipoprotein metabolism may lead to novel treatments for atherosclerosis. A comprehensive review of lipoprotein function and their role in atherosclerosis, along with the latest development of lipoprotein targeted treatment, is timely. This review focuses on the functions of different lipoproteins and their involvement in atherosclerosis. Further, diagnostic and therapeutic potential are highlighted giving insight into novel lipoprotein-targetted approaches to treat atherosclerosis.

Artificial high-density lipoprotein-mimicking nanotherapeutics for the treatment of cardiovascular diseases

Despite the ability of current efficacious low-density lipoprotein-cholesterol-lowering therapies to reduce total cardiovascular disease (CVD) risks, CVD still poses major risks for morbidity and mortality to the general population. Because of the pleiotropic endothelial protective effects of high-density lipoproteins (HDL), the direct infusion of reconstituted HDL (rHDL) products, including MDCO-216, CER001, and CSL112, have been tested in clinical trials to determine whether direct infusion of rHDL can reduce coronary events in CVD patients. In addition to these rHDL products, in the past two decades, there has been an increased focused on designing artificial HDL-mimicking nanotherapeutics to produce complementary therapeutic strategies for CVD patients beyond lowering of atherogenic lipoproteins. Although recent reviews have comprehensively discussed the developments of artificial HDL-mimicking nanoparticles as therapeutics for CVD, there has been little assessment of "plain" or "drug-free" HDL-mimicking nanoparticles as therapeutics alone. In this review, we will summarize the clinical outcomes of rHDL products, examine recent advances in other types of artificial HDL-mimicking nanotherapeutics, including polymeric nanoparticles, cyclodextrins, micelles, metal nanoparticles, and so on; and potential new approaches for future CVD interventions. Moreover, success stories, lessons, and interpretations of the utility and functionality of these HDL-mimicking nanotherapeutics will be an integral part of this article. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease.

Synthetic high-density lipoprotein nanoparticles: Good things in small packages

Medicine has been a great beneficiary of the nanotechnology revolution. Nanotechnology involves the synthesis of functional materials with at least one size dimension between 1 and 100 nm. Advances in the field have enabled the synthesis of bio-nanoparticles that can interface with physiological systems to modulate fundamental cellular processes. One example of a diverse acting nanoparticle-based therapeutic is synthetic high-density lipoprotein (HDL) nanoparticles (NP), which have great potential for treating diseases of the ocular surface. Our group has developed a spherical HDL NP using a gold nanoparticle core. HDL NPs: (i) closely mimic the physical and chemical features of natural HDLs; (ii) contain apoA-I; (iii) bind with high-affinity to SR-B1, which is the major receptor through which HDL modulates cell cholesterol metabolism and controls the selective uptake of HDL cargo into cells; (iv) are non-toxic to cells and tissues; and (v) can be chemically engineered to display nearly any surface or core composition desired. With respect to the ocular surface, topical application of HDL NPs accelerates re-epithelization of the cornea following wounding, attenuates inflammation resulting from chemical burns and/or other stresses, and effectively delivers microRNAs with biological activity to corneal cells and tissues. HDL NPs will be the foundation of a new class of topical eye drops with great translational potential and exemplify the impact that nanoparticles can have in medicine.

Atherosclerosis: Conventional intake of cardiovascular drugs versus delivery using nanotechnology - A new chance for causative therapy?

Atherosclerosis is the leading cause of death in developed countries. The pathogenetic mechanism relies on a macrophage-based immune reaction to low density lipoprotein (LDL) deposition in blood vessels with dysfunctional endothelia. Thus, atherosclerosis is defined as a chronic inflammatory disease. A plethora of cardiovascular drugs have been developed and are on the market, but the major shortcoming of standard medications is that they do not address the root cause of the disease. Statins and thiazolidinediones that have recently been recognized to exert specific anti-atherosclerotic effects represent a potential breakthrough on the horizon. But their whole potential cannot be realized due to insufficient availability at the pathological site and severe off-target effects. The focus of this review will be to elaborate how both groups of drugs could immensely profit from nanoparticulate carriers. This delivery principle would allow for their accumulation in target macrophages and endothelial cells of the atherosclerotic plaque, increasing bioavailability where it is needed most. Based on the analyzed literature we conclude design criteria for the delivery of statins and thiazolidinediones with nanoparticles for anti-atherosclerotic therapy. Nanoparticles need to be below a diameter of 100 nm to accumulate in the atherosclerotic plaque and should be fabricated using biodegradable materials. Further, the thiazolidinediones or statins must be encapsulated into the particle core, because especially for thiazolidindiones the uptake into cells is prerequisite for their mechanism of action. For optimal uptake into targeted macrophages and endothelial cells, the ideal particle should present ligands on its surface which bind specifically to scavenger receptors. The impact of statins on the lectin-type oxidized LDL receptor 1 (LOX1) seems particularly promising because of its outstanding role in the inflammatory process. Using this pioneering concept, it will be possible to promote the impact of statins and thiazolidinediones on macrophages and endothelial cells and significantly enhance their anti-atherosclerotic therapeutic potential.

Reconstituted high density lipoprotein (rHDL), a versatile drug delivery nanoplatform for tumor targeted therapy

rHDL is a synthesized drug delivery nanoplatform exhibiting excellent biocompatibility, which possesses most of the advantages of HDL. rHDL shows almost no toxicity and can be degraded to non-toxic substances in vivo. The severe limitation of the application of various antitumor agents is mainly due to their low bioavailability, high toxicity, poor stability, etc. Favorably, antitumor drug-loaded rHDL nanoparticles (NPs), which are known as an important drug delivery system (DDS), help to change the situation a lot. This DDS shows an outstanding active-targeting ability towards tumor cells and improves the therapeutic effect during antitumor treatment while overcoming the shortcomings mentioned above. In the following text, we will mainly focus on the various applications of rHDL in tumor targeted therapy by describing the properties, preparation, receptor active-targeting ability and antitumor effects of antineoplastic drug-loaded rHDL NPs.

Patent highlights October-November 2020

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

Structure and intermolecular interactions in spheroidal high-density lipoprotein subpopulations

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High-density lipoprotein subpopulations have unique surface profiles and dynamics.

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Relative hydrophobic surface area decreases with increasing lipoprotein size.

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Core lipid exposure at the lipoprotein surface decreases with increasing size.

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Cholesterol molecules localise near apolipoprotein A-I central helices.

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Lipid and protein interactions stabilise multifoil models of apolipoprotein A-I.

Human serum high-density lipoproteins (HDLs) are a population of small, dense protein-lipid aggregates that are crucial for intravascular lipid trafficking and are protective against cardiovascular disease. The spheroidal HDL subfraction can be separated by size and density into five major subpopulations with distinct molecular compositions and unique biological functionalities: HDL_3c, HDL_3b, HDL_3a, HDL_2a and HDL_2b. Representative molecular models of these five subpopulations were developed and characterised for the first time in the presence of multiple copies of its primary protein component apolipoprotein A-I (apoA-I) using coarse-grained molecular dynamics simulations. Each HDL model exhibited size, morphological and compositional profiles consistent with experimental observables. With increasing particle size the separation of core and surface molecules became progressively more defined, resulting in enhanced core lipid mixing, reduced core lipid exposure at the surface, and the formation of an interstitial region between core and surface molecules in HDL_2b. Cholesterol molecules tended to localise around the central helix-5 of apoA-I, whilst triglyceride molecules predominantly interacted with aromatic, hydrophobic residues located within the terminal helix-10 across all subpopulation models. The three intermediate HDL models exhibited similar surface profiles despite having distinct molecular compositions. ApoA-I in trefoil, quatrefoil and pentafoil arrangements across the surface of HDL particles exhibited significant warping and twisting, but largely retained intermolecular contacts between adjacent apoA-I chains. Representative HDL subpopulations differed in particle size, morphology, intermolecular interaction profiles and lipid and protein dynamics. These findings reveal how different HDL subpopulations might exhibit distinct functional associations depending on particle size, form and composition.

A systematic review of the biodistribution of biomimetic high-density lipoproteins in mice

For the past two decades, biomimetic high-density lipoproteins (b-HDL) have been used for various drug delivery applications. The b-HDL mimic the endogenous HDL, and therefore possess many attractive features for drug delivery, including high biocompatibility, biodegradability, and ability to transport and deliver their cargo (e.g. drugs and/or imaging agents) to specific cells and tissues that are recognized by HDL. The b-HDL designs reported in the literature often differ in size, shape, composition, and type of incorporated cargo. However, there exists only limited insight into how the b-HDL design dictates their biodistribution. To fill this gap, we conducted a comprehensive systematic literature search of biodistribution studies using various designs of apolipoprotein A-I (apoA-I)-based b-HDL (i.e. b-HDL with apoA-I, apoA-I mutants, or apoA-I mimicking peptides). We carefully screened 679 papers (search hits) for b-HDL biodistribution studies in mice, and ended up with 24 relevant biodistribution profiles that we compared according to b-HDL design. We show similarities between b-HDL biodistribution studies irrespectively of the b-HDL design, whereas the biodistribution of the b-HDL components (lipids and scaffold) differ significantly. The b-HDL lipids primarily accumulate in liver, while the b-HDL scaffold primarily accumulates in the kidney. Furthermore, both b-HDL lipids and scaffold accumulate well in the tumor tissue in tumor-bearing mice. Finally, we present essential considerations and strategies for b-HDL labeling, and discuss how the b-HDL biodistribution can be tuned through particle design and administration route. Our meta-analysis and discussions provide a detailed overview of the fate of b-HDL in mice that is highly relevant when applying b-HDL for drug delivery or in vivo imaging applications.

Interparticle Molecular Exchange of Surface Chemical Components of Native High-Density Lipoproteins to Complementary Nanoparticle Scaffolds

High-density lipoproteins (HDL) are constitutionally dynamic nanoparticles that circulate in the blood. The biological functions of HDLs are impacted by interchangeable surface chemical components, like cholesterol and HDL-associated proteins. Current methods to quantify the chemical constituents of HDL are largely restricted to clinical or academic laboratories and require expensive instrumentation, and there is no commonality to the techniques required to detect and quantify different analytes (e.g., cholesterol versus HDL-associated protein). To potentially facilitate and streamline the analysis of HDL composition, we hypothesized that mixing native HDLs with similarly sized gold nanoparticles whose surfaces are endowed with phospholipids, called complementary nanoparticle scaffolds (CNS), would enable interparticle exchange of surface components. Then, easy isolation of the newly formed particles could be accomplished using benchtop centrifugation for subsequent measurement of HDL components exchanged to the surface of the CNS. As proof-of-concept, data demonstrate that CNS incubated with only a few microliters of human serum rapidly (1 h) sequester cholesterol and HDL-associated proteins with direct correlation to native HDLs. As such, data show that the CNS assay is a single platform for rapid isolation and subsequent detection of the surface components of native HDLs.

Atherosclerosis and Nanomedicine Potential: Current Advances and Future Opportunities

Atherosclerosis is the leading inducement of cardiovascular diseases, which ranks the first cause of global deaths. It is an arterial disease associated with dyslipidemia and changes in the composition of the vascular wall. Besides invasive surgical strategy, the current conservative clinical treatment for atherosclerosis falls into two categories, lipid regulating-based therapy and antiinflammatory therapy. However, the existing strategies based on conventional drug delivery systems have shown limited efficacy against disease development and plenty of side effects. Nanomedicine has great potential in the development of targeted therapy, controlled drug delivery and release, the design of novel specific drugs and diagnostic modalities, and biocompatible scaffolds with multifunctional characteristics, which has led to an evolution in the diagnosis and treatment of atherosclerosis. This paper will focus on the latest nanomedicine strategies for atherosclerosis diagnosis and treatment as well as discussing the potential therapeutic targets during atherosclerosis progress, which could form the basis of development of novel nanoplatform against atherosclerosis.

Nanotechnology as a Platform for the Development of Injectable Parenteral Formulations: A Comprehensive Review of the Know-Hows and State of the Art

Within recent decades, the development of nanotechnology has made a significant contribution to the progress of various fields of study, including the domains of medical and pharmaceutical sciences. A substantially transformed arena within the context of the latter is the development and production of various injectable parenteral formulations. Indeed, recent decades have witnessed a rapid growth of the marketed and pipeline nanotechnology-based injectable products, which is a testimony to the remarkability of the aforementioned contribution. Adjunct to the ability of nanomaterials to deliver the incorporated payloads to many different targets of interest, nanotechnology has substantially assisted to the development of many further facets of the art. Such contributions include the enhancement of the drug solubility, development of long-acting locally and systemically injectable formulations, tuning the onset of the drug’s release through the endowment of sensitivity to various internal or external stimuli, as well as adjuvancy and immune activation, which is a desirable component for injectable vaccines and immunotherapeutic formulations. The current work seeks to provide a comprehensive review of all the abovementioned contributions, along with the most recent advances made within each domain. Furthermore, recent developments within the domains of passive and active targeting will be briefly debated.

Reconfiguring Nature's Cholesterol Accepting Lipoproteins as Nanoparticle Platforms for Transport and Delivery of Therapeutic and Imaging Agents

Apolipoproteins are critical structural and functional components of lipoproteins, which are large supramolecular assemblies composed predominantly of lipids and proteins, and other biomolecules such as nucleic acids. A signature feature of apolipoproteins is the preponderance of amphipathic α-helical motifs that dictate their ability to make extensive non-covalent inter- or intra-molecular helix-helix interactions in lipid-free states or helix-lipid interactions with hydrophobic biomolecules in lipid-associated states. This review focuses on the latter ability of apolipoproteins, which has been capitalized on to reconstitute synthetic nanoscale binary/ternary lipoprotein complexes composed of apolipoproteins/peptides and lipids that mimic native high-density lipoproteins (HDLs) with the goal to transport drugs. It traces the historical development of our understanding of these nanostructures and how the cholesterol accepting property of HDL has been reconfigured to develop them as drug-loading platforms. The review provides the structural perspective of these platforms with different types of apolipoproteins and an overview of their synthesis. It also examines the cargo that have been loaded into the core for therapeutic and imaging purposes. Finally, it lays out the merits and challenges associated with apolipoprotein-based nanostructures with a future perspective calling for a need to develop "zip-code"-based delivery for therapeutic and diagnostic applications.

Dual-Targeted Synthetic Nanoparticles for Cardiovascular Diseases

Atherosclerosis is one of the world's most aggressive diseases, claiming over 17.5 million lives per year. This disease is usually caused by high amounts of lipoproteins circulating in the blood stream, which leads to plaque formation. Ultimately, these plaques can undergo thrombosis and lead to major heart damage. A major contributor to these vulnerable plaques is macrophage apoptosis. Development of nanovehicles that carry contrast and therapeutic agents to the mitochondria within these macrophages is attractive for the diagnosis and treatment of atherosclerosis. Here, we report the design and synthesis of a dual-targeted synthetic nanoparticle (NP) to perform the double duty of diagnosis and therapy in atherosclerosis treatment regime. A library of dual-targeted NPs with an encapsulated iron oxide NP, mito-magneto (MM), with a magnetic resonance imaging (MRI) contrast enhancement capability was elucidated. Relaxivity measurements revealed that there is a substantial enhancement in transverse relaxivities upon the encapsulation of MM inside the dual-targeted NPs, highlighting the MRI contrast-enhancing ability of these NPs. Successful in vivo imaging documenting the distribution of MM-encapsulated dual-targeted NPs in the heart and aorta in mice ensured the diagnostic potential. The presence of mannose receptor targeting ligands and the optimization of the NP composition facilitated its ability to perform therapeutic duty by targeting the macrophages at the plaque. These dual-targeted NPs with the encapsulated MM were able to show therapeutic potential and did not trigger any toxic immunogenic response.

High density lipoprotein mimicking nanoparticles for atherosclerosis

Atherosclerosis is a major contributor to many cardiovascular events, including myocardial infarction, ischemic stroke, and peripheral arterial disease, making it the leading cause of death worldwide. High-density lipoproteins (HDL), also known as "good cholesterol", have been shown to demonstrate anti-atherosclerotic efficacy through the removal of cholesterol from foam cells in atherosclerotic plaques. Because of the excellent anti-atherosclerotic properties of HDL, in the past several years, there has been tremendous attention in designing HDL mimicking nanoparticles (NPs) of varying functions to image, target, and treat atherosclerosis. In this review, we are summarizing the recent progress in the development of HDL mimicking NPs and their applications for atherosclerosis.

Biomimetic Magnetic Nanostructures: A Theranostic Platform Targeting Lipid Metabolism and Immune Response in Lymphoma

B-cell lymphoma cells depend upon cholesterol to maintain pro-proliferation and pro-survival signaling via the B-cell receptor. Targeted cholesterol depletion of lymphoma cells is an attractive therapeutic strategy. We report here high-density lipoprotein mimicking magnetic nanostructures (HDL-MNSs) that can bind to the high-affinity HDL receptor, scavenger receptor type B1 (SR-B1), and interfere with cholesterol flux mechanisms in SR-B1 receptor positive lymphoma cells, causing cellular cholesterol depletion. In addition, the MNS core can be utilized for its ability to generate heat under an external radio frequency field. The thermal activation of MNS can lead to both innate and adaptive antitumor immune responses by inducing the expression of heat shock proteins that lead to activation of antigen presenting cells and finally lymphocyte trafficking. In the present study, we demonstrate SR-B1 receptor mediated binding and cellular uptake of HDL-MNS and prevention of phagolysosome formation by transmission electron microscopy, fluorescence microscopy, and ICP-MS analysis. The combinational therapeutics of cholesterol depletion and thermal activation significantly improves therapeutic efficacy in SR-B1 expressing lymphoma cells. HDL-MNS reduces the T₂ relaxation time under magnetic resonance imaging (MRI) more effectively compared with a commercially available contrast agent, and the specificity of HDL-MNS toward the SR-B1 receptor leads to differential contrast between SR-B1 positive and negative cells suggesting its utility in diagnostic imaging. Overall, we have demonstrated that HDL-MNSs have cell specific targeting efficiency, can modulate cholesterol efflux, can induce thermal activation mediated antitumor immune response, and possess high contrast under MRI, making it a promising theranostic platform in lymphoma.

The Composition of Reconstituted High-Density Lipoproteins (rHDL) Dictates the Degree of rHDL Cargo- and Size-Remodeling via Direct Interactions with Endogenous Lipoproteins

The application of reconstituted high-density lipoproteins (rHDL) as a drug-carrier has during the past decade been established as a promising approach for effective receptor-mediated drug delivery, and its ability to target tumors has recently been confirmed in a clinical trial. The rHDL mimics the endogenous HDL, which is known to be highly dynamic and undergo extensive enzyme-mediated remodulations. Hence, to reveal the physiological rHDL stability, a thorough characterization of the dynamics of rHDL in biologically relevant environments is needed. We employ a size-exclusion chromatography (SEC) method to evaluate the dynamics of discoidal rHDL in fetal bovine serum (FBS), where we track both the rHDL lipids (by the fluorescence from lipid-conjugated fluorophores) and apoA-I (by human apoA-I ELISA). We show by using lipoprotein depleted FBS and isolated lipoproteins that rHDL lipids can be transferred to endogenous lipoproteins via direct interactions in a nonenzymatic process, resulting in rHDL compositional- and size-remodeling. This type of dynamics could lead to misinterpretations of fluorescence-based rHDL uptake studies due to desorption of labile lipophilic fluorophores or off-target side effects due to desorption of incorporated drugs. Importantly, we show how the degree of rHDL remodeling can be controlled by the compositional design of the rHDL. Understanding the correlation between the molecular properties of the rHDL constituents and their collective dynamics is essential for improving the rHDL-based drug delivery platform. Taken together, our work highlights the need to carefully consider the compositional design of rHDL and test its stability in a biological relevant environment, when developing rHDL for drug delivery purposes.

Nanomaterials for the theranostics of obesity

As a chronic and lifelong disease, obesity not only significant impairs health but also dramatically shortens life span (at least 10 years). Obesity requires a life-long effort for the successful treatment because a number of abnormalities would appear in the development of obesity. Nanomaterials possess large specific surface area, strong absorptivity, and high bioavailability, especially the good targeting properties and adjustable release rate, which would benefit the diagnosis and treatment of obesity and obesity-related metabolic diseases. Herein, we discussed the therapy and diagnosis of obesity and obesity-related metabolic diseases by using nanomaterials. Therapies of obesity with nanomaterials include improving intestinal health and reducing energy intake, targeting and treating functional cell abnormalities, regulating redox homeostasis, and removing free lipoprotein in blood. Diagnosis of obesity-related metabolic diseases would benefit the therapy of these diseases. The development of nanomaterials will promote the diagnosis and therapy of obesity and obesity-related metabolic diseases.

Nanoparticle-siRNA: a potential strategy for ovarian cancer therapy?

Ovarian cancer is one of the most common causes of mortality throughout the world. Unfortunately, chemotherapy has failed to cure advanced cancers developing multidrug resistance (MDR). Moreover, it has critical side effects because of nonspecific toxicity. Thanks to specific silencing of oncogenes and MDR-associated genes, nano-siRNA drugs can be a great help address the limitations of chemotherapy. Here, we review the current advances in nanoparticle-mediated siRNA delivery strategies such as polymeric- and lipid-based systems, rigid nanoparticles and nanoparticles coupled to specific ligand systems. Nanoparticle-based codelivery of anticancer drugs and siRNA targeting various mechanisms of MDR is a cutting-edge strategy for ovarian cancer therapy, which is completely discussed in this review.

Supramolecular Assembly of High-Density Lipoprotein Mimetic Nanoparticles Using Lipid-Conjugated Core Scaffolds

Synthetic high-density lipoprotein (HDL) mimics have emerged as promising therapeutic agents. However, approaches to date have been unable to reproduce key features of spherical HDLs, which are the most abundant human HDL species. Here, we report the synthesis and characterization of spherical HDL mimics using lipid-conjugated organic core scaffolds. The core design motif constrains and orients phospholipid geometry to facilitate the assembly of soft-core nanoparticles that are approximately 10 nm in diameter and resemble human HDLs in their size, shape, surface chemistry, composition, and protein secondary structure. These particles execute salient HDL functions, including efflux of cholesterol from macrophages, cholesterol delivery to hepatocytes, support lecithin:cholesterol acyltransferase activity, and suppress inflammation. These results represent a significant step toward a genuine functional mimic of human HDLs.

Hybrid lipid-nanoparticle complexes for biomedical applications

Biomolecule-nanoparticle hybrids have proven to be one of most promising frontiers in biomedical research. In recent years, there has been an increased focus on the development of hybrid lipid-nanoparticle complexes (HLNCs) which inherit unique properties of both the inorganic nanoparticles and the lipid assemblies (i.e. liposomes, lipoproteins, solid lipid nanoparticles, and nanoemulsions) that comprise them. In combination of their component parts, HLNCs also gain new functionalities which are utilized for numerous biomedical applications (i.e. stimuli-triggered drug release, photothermal therapy, and bioimaging). The localization of nanoparticles within the lipid assemblies largely dictates the attributes and functionalities of the hybrid complexes and are classified as such: (i) liposomes with surface-bound nanoparticles, (ii) liposomes with bilayer-embedded nanoparticles, (iii) liposomes with core-encapsulated nanoparticles, (iv) lipid assemblies with hydrophobic core-encapsulated nanoparticles, and (v) lipid bilayer-coated nanoparticles. Herein, we review the properties of each hybrid and the rational design of HLNCs for biomedical applications as reported by recent investigations. Future directions in advancing and expanding the scope of HLNCs are also proposed.

Covalent Surface Modification of Lipid Nanoparticles by Rapid Potassium Acyltrifluoroborate Amide Ligation

Because of the recent increasing demand for the synthetic biomimetic nanoparticles as in vivo carriers of drugs and imaging probes, it is very important to develop reliable, stable, and orthogonal methods for surface functionalization of the particles. To address these issues, in this study, a recently reported chemoselective amide-forming ligation reaction [potassium acyltrifluoroborate (KAT) ligation] was employed for the first time, as a mean to provide the surface functionalization of particles for creating covalent attachments of bioactive molecules. A KAT derivative of oleic acid (OA-KAT, 1) was added to a mixture of three lipid components (triolein, phosphatidyl choline, and cholesteryl oleate), which have been commonly used as substrates for lipid nanoparticles. After sonication and extrusion in a buffer, successfully obtained lipid nanoparticles containing OA-KAT (NP-KAT) resulted to be well-dispersed with mean diameters of about 40-70 nm by dynamic light scattering. After preliminary confirmation of the fast and efficient KAT ligation in a solution phase using the identical reaction substrates, the "on-surface (on-particle)" KAT ligation on the NP-KAT was tested with an N-hydroxylamine derivative of fluorescein 2. The ligation was carried out in a phosphate buffer (10 mM, pH 5.2) at room temperature with reactant concentration ranges of 250 μM. Reaction efficiency was evaluated based on the amount of boron (determined by inductively coupled plasma mass spectrometry) and fluorescein (determined by fluorescence emission) in the particles before and after the reaction. As a result, the reaction proceeded in a significantly efficient way with ca. 40-50% conversion of the OA-KAT incorporated in the particles. Taken together with the fact that KAT ligation does not require any additional coupling reagents, these results indicated that the "on-surface" chemical functionalization of nanoparticles by KAT ligation is a useful method and represents a powerful and potentially versatile tool for the production of nanoparticles with a variety of covalently functionalized biomolecules and probes.

Immune lipoprotein nanostructures inspired relay drug delivery for amplifying antitumor efficiency

Chemo-immunotherapy represents an appealing approach to improving cancer treatment. Simultaneously administrating chemotherapeutics with immunoadjuvants can elicit potent tumor death and immune responses. Herein, high density lipoprotein (HDL) inspired immune lipoprotein was proposed for relay drug delivery and amplifying antitumor therapy. Lipophilic AS1411 aptamer-immunoadjuvant CpG fused sequences (Apt-CpG-DSPE) were conjugated to facilitate decoration onto HDLs; and doxorubicin (Dox) was successively intercalated into the consecutive base pairs of Apt-CpG to complete immune HDL nanodrug imHDL/Apt-CpG-Dox. For relay drug delivery, imHDL/Apt-CpG-Dox underwent site-specific structure collapse in tumor intercellular substances inspired from HDL biofunctions (sequential module I); subsequently, dissociated Apt-CpG-Dox was endocytosed into tumor cells mediated by the recognition of AS1411 and nucleolin (sequential module II), translocating Dox to nucleus and enabling tumor ablation and antigens release. The liberated CpG motif further evoked antigen recognition, induced vast secretion of pro-inflammatory cytokines and potentiated host antitumor immunity. Our studies demonstrated that HDL biomimetic platform based relay drug delivery strategy outperformed the monotherapy counterparts in malignant tumor models, eventually generating an augmented antitumor efficacy.

Endocytosis of lipoproteins

During their metabolism, all lipoproteins undergo endocytosis, either to be degraded intracellularly, for example in hepatocytes or macrophages, or to be re-secreted, for example in the course of transcytosis by endothelial cells. Moreover, there are several examples of internalized lipoproteins sequestered intracellularly, possibly to exert intracellular functions, for example the cytolysis of trypanosoma. Endocytosis and the subsequent intracellular itinerary of lipoproteins hence are key areas for understanding the regulation of plasma lipid levels as well as the biological functions of lipoproteins. Indeed, the identification of the low-density lipoprotein (LDL)-receptor and the unraveling of its transcriptional regulation led to the elucidation of familial hypercholesterolemia as well as to the development of statins, the most successful therapeutics for lowering of cholesterol levels and risk of atherosclerotic cardiovascular diseases. Novel limiting factors of intracellular trafficking of LDL and the LDL receptor continue to be discovered and to provide drug targets such as PCSK9. Surprisingly, the receptors mediating endocytosis of high-density lipoproteins or lipoprotein(a) are still a matter of controversy or even new discovery. Finally, the receptors and mechanisms, which mediate the uptake of lipoproteins into non-degrading intracellular itineraries for re-secretion (transcytosis, retroendocytosis), storage, or execution of intracellular functions, are largely unknown.

HDL-AuNPs-BMS Nanoparticle Conjugates as Molecularly Targeted Therapy for Leukemia

Gold nanoparticles (AuNPs) with adsorbed high-density lipoprotein (HDL) have been utilized to deliver oligonucleotides, yet HDL-AuNPs functionalized with small-molecule inhibitors have not been systematically explored. Here, we report an AuNP-based therapeutic system (HDL-AuNPs-BMS) for acute myeloid leukemia (AML) by delivering BMS309403 (BMS), a small molecule that selectively inhibits AML-promoting factor fatty acid-binding protein 4. To synthesize HDL-AuNPs-BMS, we use AuNP as a template to control conjugate size ensuring a spherical shape to engineer HDL-like nanoparticles containing BMS. The zeta potential and size of the HDL-AuNPs obtained from transmission electron microscopy demonstrate that the HDL-AuNPs-BMS are electrostatically stable and 25 nm in diameter. Functionally, compared to free drug, HDL-AuNPs-BMS conjugates are more readily internalized by AML cells and have more pronounced effects on downregulation of DNA methyltransferase 1 (DNMT1), induction of DNA hypomethylation, and restoration of epigenetically silenced tumor suppressor p15^INK4B coupled with AML growth arrest. Importantly, systemic administration of HDL-AuNPs-BMS conjugates into AML-bearing mice inhibits DNMT1-dependent DNA methylation, induces AML cell differentiation, and diminishes AML disease progression without obvious side effects. In summary, these data, for the first time, demonstrate HDL-AuNPs as an effective delivery platform with great potential to attach distinct inhibitors and HDL-AuNPs-BMS conjugates as a promising therapeutic platform to treat leukemia.

Nitric Oxide-Delivering High-Density Lipoprotein-like Nanoparticles as a Biomimetic Nanotherapy for Vascular Diseases

Disorders of blood vessels cause a range of severe health problems. As a powerful vasodilator and cellular second messenger, nitric oxide (NO) is known to have beneficial vascular functions. However, NO typically has a short half-life and is not specifically targeted. On the other hand, high-density lipoproteins (HDLs) are targeted natural nanoparticles (NPs) that transport cholesterol in the systemic circulation and whose protective effects in vascular homeostasis overlap with those of NO. Evolving the AuNP-templated HDL-like nanoparticles (HDL NPs), a platform of bioinspired HDL, we set up a targeted biomimetic nanotherapy for vascular disease that combines the functions of NO and HDL. A synthetic S-nitrosylated (SNO) phospholipid (1,2-dipalmitoyl-sn-glycero-3-phosphonitrosothioethanol) was synthesized and assembled with S-containing phospholipids and the principal protein of HDL, apolipoprotein A-I, to construct NO-delivering HDL-like particles (SNO HDL NPs). SNO HDL NPs self-assemble under mild conditions similar to natural processes, avoiding the complex postassembly modification needed for most synthetic NO-release nanoparticles. In vitro data demonstrate that the SNO HDL NPs merge the functional properties of NO and HDL into a targeted nanocarrier. Also, SNO HDL NPs were demonstrated to reduce ischemia/reperfusion injury in vivo in a mouse kidney transplant model and atherosclerotic plaque burden in a mouse model of atherosclerosis. Thus, the synthesis of SNO HDL NPs provides not only a bioinspired nanotherapy for vascular disease but also a foundation to construct diversified multifunctional platforms based on HDL NPs in the future.

HDL nanoparticles targeting sonic hedgehog subtype medulloblastoma

Medulloblastoma is the most common paediatric malignant brain cancer and there is a need for new targeted therapeutic approaches to more effectively treat these malignant tumours, which can be divided into four molecular subtypes. Here, we focus on targeting sonic hedgehog (SHH) subtype medulloblastoma, which accounts for approximately 25% of all cases. The SHH subtype relies upon cholesterol signalling for tumour growth and maintenance of tumour-initiating cancer stem cells (CSCs). To target cholesterol signalling, we employed biomimetic high-density lipoprotein nanoparticles (HDL NPs) which bind to the HDL receptor, scavenger receptor type B-1 (SCARB1), depriving cells of natural HDL and their cholesterol cargo. We demonstrate uptake of HDL NPs in SCARB1 expressing medulloblastoma cells and depletion of cholesterol levels in cancer cells. HDL NPs potently blocked proliferation of medulloblastoma cells, as well as hedgehog-driven Ewing sarcoma cells. Furthermore, HDL NPs disrupted colony formation in medulloblastoma and depleted CSC populations in medulloblastoma and Ewing sarcoma. Altogether, our findings provide proof of principle for the development of a novel targeted approach for the treatment of medulloblastoma using HDL NPs. These findings present HDL-mimetic nanoparticles as a promising therapy for sonic hedgehog (SHH) subtype medulloblastoma and possibly other hedgehog-driven cancers.

Scavenger Receptor Type B1 and Lipoprotein Nanoparticle Inhibit Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSC) are innate immune cells that potently inhibit T cells. In cancer, novel therapies aimed to activate T cells can be rendered ineffective due to the activity of MDSCs. Thus, targeted inhibition of MDSCs may greatly enhance T-cell-mediated antitumor immunity, but mechanisms remain obscure. Here we show, for the first time, that scavenger receptor type B-1 (SCARB1), a high-affinity receptor for spherical high-density lipoprotein (HDL), is expressed by MDSCs. Furthermore, we demonstrate that SCARB1 is specifically targeted by synthetic high-density lipoprotein-like nanoparticles (HDL NP), which reduce MDSC activity. Using in vitro T-cell proliferation assays, data show that HDL NPs specifically bind SCARB1 to inhibit MDSC activity. In murine cancer models, HDL NP treatment significantly reduces tumor growth, metastatic tumor burden, and increases survival due to enhanced adaptive immunity. Flow cytometry and IHC demonstrate that HDL NP-mediated suppression of MDSCs increased CD8⁺ T cells and reduced Treg cells in the metastatic tumor microenvironment. Using transgenic mice lacking SCARB1, in vivo data clearly show that the HDL NPs specifically target this receptor for suppressing MDSCs. Ultimately, our data provide a new mechanism and targeted therapy, HDL NPs, to modulate a critical innate immune cell checkpoint to enhance the immune response to cancer. Mol Cancer Ther; 17(3); 686-97. ©2017 AACR.

Rational Targeting of Cellular Cholesterol in Diffuse Large B-Cell Lymphoma (DLBCL) Enabled by Functional Lipoprotein Nanoparticles: A Therapeutic Strategy Dependent on Cell of Origin

Cancer cells have altered metabolism and, in some cases, an increased demand for cholesterol. It is important to identify novel, rational treatments based on biology, and cellular cholesterol metabolism as a potential target for cancer is an innovative approach. Toward this end, we focused on diffuse large B-cell lymphoma (DLBCL) as a model because there is differential cholesterol biosynthesis driven by B-cell receptor (BCR) signaling in germinal center (GC) versus activated B-cell (ABC) DLBCL. To specifically target cellular cholesterol homeostasis, we employed high-density lipoprotein-like nanoparticles (HDL NP) that can generally reduce cellular cholesterol by targeting and blocking cholesterol uptake through the high-affinity HDL receptor, scavenger receptor type B-1 (SCARB1). As we previously reported, GC DLBCL are exquisitely sensitive to HDL NP as monotherapy, while ABC DLBCL are less sensitive. Herein, we report that enhanced BCR signaling and resultant de novo cholesterol synthesis in ABC DLBCL drastically reduces the ability of HDL NPs to reduce cellular cholesterol and induce cell death. Therefore, we combined HDL NP with the BCR signaling inhibitor ibrutinib and the SYK inhibitor R406. By targeting both cellular cholesterol uptake and BCR-associated de novo cholesterol synthesis, we achieved cellular cholesterol reduction and induced apoptosis in otherwise resistant ABC DLBCL cell lines. These results in lymphoma demonstrate that reduction of cellular cholesterol is a powerful mechanism to induce apoptosis. Cells rich in cholesterol require HDL NP therapy to reduce uptake and molecularly targeted agents that inhibit upstream pathways that stimulate de novo cholesterol synthesis, thus, providing a new paradigm for rationally targeting cholesterol metabolism as therapy for cancer.

Engineering Single Nanopores on Gold Nanoplates by Tuning Crystal Screw Dislocation

Compared with the large variety of solid gold nanostructures, synthetic approaches for their hollow counterparts are limited, largely confined to chemical and irradiation-based etching of preformed nanostructures. In particular, the preparation of through nanopore structures is extremely challenging. Here, a unique strategy for direct synthesis of gold nanopores in solution without the need for sacrificial templates or postsynthesis processing is reported. By controlling the degree of crystal screw dislocation, a single through pore with diameter ranging from sub-nanometer to tens of nanometers, in the center of large gold nanoplates, can be engineered with precision. Ionic current rectification behaviors are observed using the gold nanopore, potentially enabling new capabilities in biosensing, sequencing, and imaging.

Synthetic high-density lipoproteins as targeted monotherapy for chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) remains incurable despite the introduction of new drugs. Therapies targeting receptors and pathways active specifically in malignant B cells might provide better treatment options. For instance, in B cell lymphoma, our group has previously shown that scavenger receptor type B-1 (SR-B1), the high-affinity receptor for cholesterol-rich high-density lipoproteins (HDL), is a therapeutic target. As evidence suggests that targeting cholesterol metabolism in CLL cells may have therapeutic benefit, we examined SR-B1 expression in primary CLL cells from patients. Unlike normal B cells that do not express SR-B1, CLL cells express the receptor. As a result, we evaluated cholesterol-poor synthetic HDL nanoparticles (HDL NP), known for targeting SR-B1, as a therapy for CLL. HDL NPs potently and selectively induce apoptotic cell death in primary CLL cells. HDL NPs had no effect on normal peripheral blood mononuclear cells from healthy individuals or patients with CLL. These data implicate SR-B1 as a target in CLL and HDL NPs as targeted monotherapy for CLL.

Self-Assembling Cyclic d,l-α-Peptides as Modulators of Plasma HDL Function. A Supramolecular Approach toward Antiatherosclerotic Agents

There is great interest in developing new modes of therapy for atherosclerosis to treat coronary heart disease and stroke, particularly ones that involve modulation of high-density lipoproteins (HDLs). Here, we describe a new supramolecular chemotype for altering HDL morphology and function. Guided by rational design and SAR-driven peptide sequence enumerations, we have synthesized and determined the HDL remodeling activities of over 80 cyclic d,l-α-peptides. We have identified a few distinct sequence motifs that are effective in vitro in remodeling human and mouse plasma HDLs to increase the concentration of lipid-poor pre-beta HDLs, which are key initial acceptors of cholesterol in the reverse cholesterol transport (RCT) process, and concomitantly promote cholesterol efflux from macrophage cells. Functional assays with various control peptides, such as scrambled sequences, linear and enantiomeric cyclic peptide variants, and backbone-modified structures that limit peptide self-assembly, provide strong support for the supramolecular mode of action. Importantly, when the lead cyclic peptide c[wLwReQeR] was administered to mice (ip), it also promoted the formation of small, lipid-poor HDLs in vivo, displayed good plasma half-life (∼6 h), did not appear to have adverse side effects, and exerted potent anti-inflammatory effects in an acute in vivo inflammation assay. Given that previously reported HDL remodeling peptides have been based on α-helical apoA-I mimetic architectures, the present study, involving a new structural class, represents a promising step toward new potential therapeutics to combat atherosclerosis.

Molecular Dynamics Simulation and Experimental Studies of Gold Nanoparticle Templated HDL-like Nanoparticles for Cholesterol Metabolism Therapeutics

High-density lipoprotein (HDL) plays an important role in the transport and metabolism of cholesterol. Mimics of HDL are being explored as potentially powerful therapeutic agents for removing excess cholesterol from arterial plaques. Gold nanoparticles (AuNPs) functionalized with apolipoprotein A-I and with the lipids 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[3-(2-pyridyldithio)propionate] have been demonstrated to be robust acceptors of cellular cholesterol. However, detailed structural information about this functionalized HDL AuNP is still lacking. In this study, we have used X-ray photoelectron spectroscopy and lecithin/cholesterol acyltransferase activation experiments together with coarse-grained and all-atom molecular dynamics simulations to model the structure and cholesterol uptake properties of the HDL AuNP construct. By simulating different apolipoprotein-loaded AuNPs, we find that lipids are oriented differently in regions with and without apoA-I. We also show that in this functionalized HDL AuNP, the distribution of cholesteryl ester maintains a reverse concentration gradient that is similar to the gradient found in native HDL.

Properties of Native High-Density Lipoproteins Inspire Synthesis of Actively Targeted In Vivo siRNA Delivery Vehicles

Efficient systemic administration of therapeutic short interfering RNA (siRNA) is challenging. High-density lipoproteins (HDL) are natural in vivo RNA delivery vehicles. Specifically, native HDLs: 1) Load single-stranded RNA; 2) Are anionic, which requires charge reconciliation between the RNA and HDL, and 3) Actively target scavenger receptor type B-1 (SR-B1) to deliver RNA. Emphasizing these particular parameters, we employed templated lipoprotein particles (TLP), mimics of spherical HDLs, and self-assembled them with single-stranded complements of, presumably, any highly unmodified siRNA duplex pair after formulation with a cationic lipid. Resulting siRNA templated lipoprotein particles (siRNA-TLP) are anionic and tunable with regard to RNA assembly and function. Data demonstrate that the siRNA-TLPs actively target SR-B1 to potently reduce androgen receptor (AR) and enhancer of zeste homolog 2 (EZH2) proteins in multiple cancer cell lines. Systemic administration of siRNA-TLPs demonstrated no off-target toxicity and significantly reduced the growth of prostate cancer xenografts. Thus, native HDLs inspired the synthesis of a hybrid siRNA delivery vehicle that can modularly load single-stranded RNA complements after charge reconciliation with a cationic lipid, and that function due to active targeting of SR-B1.

Lipoproteins and lipoprotein mimetics for imaging and drug delivery

Lipoproteins are a set of natural nanoparticles whose main role is the transport of fats within the body. While much work has been done to develop synthetic nanocarriers to deliver drugs or contrast media, natural nanoparticles such as lipoproteins represent appealing alternatives. Lipoproteins are biocompatible, biodegradable, non-immunogenic and are naturally targeted to some disease sites. Lipoproteins can be modified to act as contrast agents in many ways, such as by insertion of gold cores to provide contrast for computed tomography. They can be loaded with drugs, nucleic acids, photosensitizers or boron to act as therapeutics. Attachment of ligands can re-route lipoproteins to new targets. These attributes render lipoproteins attractive and versatile delivery vehicles. In this review we will provide background on lipoproteins, then survey their roles as contrast agents, in drug and nucleic acid delivery, as well as in photodynamic therapy and boron neutron capture therapy.

Targeted Nanotherapies for the Treatment of Surgical Diseases

OBJECTIVE

To describe the components of targeted nanotherapeutics and to review their applications in the treatment of surgical diseases.

BACKGROUND

Targeted nanotherapeutic is a novel strategy for treating a variety of diseases and is an emerging technology that offers advantages over current treatment strategies. The nanoscale size, combined with the ability to surface functionalize the delivery vehicle to enable targeting and incorporate a therapeutic payload, provides a new and innovative therapeutic platform to treat surgical diseases that has yet to be fully realized in the surgical arena.

METHODS

A comprehensive literature review of nanotherapeutics, targeting strategies, and their utility in treating surgical diseases is performed.

RESULTS

Targeted nanotherapeutics have demonstrated safety and biocompatibility in treating surgical diseases. The ability to surface functionalize the nanoparticles affords a unique tailorability that enables targeting specificity and therapeutic payload delivery to treat a variety of surgical diseases. Moreover, the small size and targeting capabilities allow access to biological compartments, such as the blood-brain barrier, that have previously been difficult to treat.

CONCLUSIONS

Targeted nanotherapeutics represent a novel therapeutic platform and have great potential to impact the treatment of surgical diseases.

Mosaic Interdigitated Structure in Nanoparticle-Templated Phospholipid Bilayer Supports Partial Lipidation of Apolipoprotein A-I

Using gold nanoparticle-templated high-density lipoprotein-like particles as a model, the nanoparticle-templated phospholipid bilayer is studied from the bottom-up. Data support the phospholipids have a mosaic interdigitated structure. The discontinuous lipid milieu supports partial lipidation of apolipoprotein A-I, different from an ordinary phospholipid bilayer, suggesting that synergy between nanoparticle templates and bound phospholipid layers can modulate amphiphilic proteins for desired functions.

DNA micelle flares: a study of the basic properties that contribute to enhanced stability and binding affinity in complex biological systems

DMFs are spherical DNA-diacyllipid nanostructures formed by hydrophobic effects between lipid tails coupled to single-stranded DNAs. Such properties as high cellular permeability, low critical micelle concentration (CMC) and facile fabrication facilitate intracellular imaging and drug delivery. While the basic properties of NFs have been amply described and tested, few studies have characterized the fundamental properties of DMFs with particular respect to aggregation number, dissociation constant and biostability. Therefore, to further explore their conformational features and enhanced stability in complex biological systems, we herein report a series of characterization studies. Static light scattering (SLS) demonstrated that DMFs possess greater DNA loading capacity when compared to other DNA-based nanostructures. Upon binding to complementary DNA (cDNA), DMFs showed excellent dissociation constants (Kd) and increased melting temperatures, as well as constant CMC (10 nM) independent of DNA length. DMFs also present significantly enhanced stability in aqueous solution with nuclease and cell lysate. These properties make DMFs ideal for versatile applications in bioanalysis and theranostics studies.