Attenuation of nontargeted cell-kill using a high-density lipoprotein-mimicking peptide--phospholipid nanoscaffold

Recent Progress in Lipid Nanoparticles for Cancer Theranostics: Opportunity and Challenges

Cancer is one of the major leading causes of mortality in the world. The implication of nanotherapeutics in cancer has garnered splendid attention owing to their capability to efficiently address various difficulties associated with conventional drug delivery systems such as non-specific biodistribution, poor efficacy, and the possibility of occurrence of multi-drug resistance. Amongst a plethora of nanocarriers for drugs, this review emphasized lipidic nanocarrier systems for delivering anticancer therapeutics because of their biocompatibility, safety, high drug loading and capability to simultaneously carrying imaging agent and ligands as well. Furthermore, to date, the lack of interaction between diagnosis and treatment has hampered the efforts of the nanotherapeutic approach alone to deal with cancer effectively. Therefore, a novel paradigm with concomitant imaging (with contrasting agents), targeting (with biomarkers), and anticancer agent being delivered in one lipidic nanocarrier system (as cancer theranostics) seems to be very promising in overcoming various hurdles in effective cancer treatment. The major obstacles that are supposed to be addressed by employing lipidic theranostic nanomedicine include nanomedicine reach to tumor cells, drug internalization in cancer cells for therapeutic intervention, off-site drug distribution, and uptake via the host immune system. A comprehensive account of recent research updates in the field of lipidic nanocarrier loaded with therapeutic and diagnostic agents is covered in the present article. Nevertheless, there are notable hurdles in the clinical translation of the lipidic theranostic nanomedicines, which are also highlighted in the present review along with plausible countermeasures.

Effect of apoA-I PEGylation on the Biological Fate of Biomimetic High-Density Lipoproteins

Biomimetic high-density lipoproteins (b-HDL) have in the past two decades been applied for various drug delivery applications. As b-HDL inherently have relatively long circulation half-life and high tumor accumulation, this has inspired researchers to use b-HDL to selectively deliver drugs to tumors. PEGylation of the b-HDL has been pursued to increase the circulation half-life and therapeutic efficacy even further. The b-HDL consist of lipids stabilized by a protein/peptide scaffold, and while PEGylation of the scaffold has been shown to greatly increase the circulation half-life of the scaffold, the effect of PEGylation of the lipids is much less significant. Still, it remains to be evaluated how the biological fate, including cellular uptake, biodistribution, and circulation half-life, of the b-HDL lipids is affected by PEGylation of the b-HDL scaffold. We studied this with apolipoprotein A-I (apoA-I)-based b-HDL and mono-PEGylated b-HDL (PEG b-HDL) both in vitro and in vivo. We found that PEGylation of the b-HDL scaffold only seemed to have minimal effect on the biological fate of the lipids. Both b-HDL and PEG b-HDL overall shared similar biological fates, which includes cellular uptake through the scavenger receptor class B type 1 (SR-BI) and relatively high tumor accumulation. This highlights that b-HDL are dynamic particles, and the biological fates of the b-HDL components (lipids and scaffold) can differ. A phenomenon that may also apply for other multicomponent nanoparticles.

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.

Establishment of a hTfR mAb-functionalized HPPS theranostic nanoplatform

Rational: Many efforts have been made to develop ligand-directed nanotheranostics in cancer management which could afford both therapeutic and diagnostic functions as well as tumor-tailored targeting. Theranostic nanoplatform targeting transferrin receptor (TfR) is an effective system for favorable delivery of diagnostic and therapeutic agents to malignancy site. Methods: To enable amalgamation of therapy and diagnosis to many TfR+ tumor, hTfR (human TfR) monoclonal antibody (mAb)-functionalized HPPS nanoparticle (HPPS-mAb) was prepared with hTfR mAb on the shell and with fluorophore DiR-BOA in the core. The targeting specificity was investigated in vitro by immunostaining and in vivo using a double-tumor-engrafted mouse model. HPPS-mAb/siRNA effect on HepG2 cells was determined by RT-PCR and western blot. Results: HPPS-mAb could specifically target cancer cells through TfR and achieve tumor accumulation at an early valuable time node, thus efficiently delivering therapeutic survivin siRNA into TfR+ HepG2 cells and mediating cell apoptosis. DiR-BOA can act as an imaging tool to diagnose cancer. Conclusions: Our studies provide a promising TfR mAb-directed theranostic nanoplatform candidate in tumor molecular imaging and in TfR targeted tumor therapy.

Lipoprotein-Like Nanoparticle Carrying Small Interfering RNA Against Spalt-Like Transcription Factor 4 Effectively Targets Hepatocellular Carcinoma Cells and Decreases Tumor Burden

Patients with advanced hepatocellular carcinoma (HCC) are often unable to tolerate chemotherapy due to liver dysfunction in the setting of cirrhosis. We investigate high-density lipoprotein (HDL)-mimicking peptide phospholipid scaffold (HPPS), which are nanoparticles that capitalize on normal lipoprotein metabolism and transport, as a solution for directed delivery of small interfering RNA (siRNA) cargo into HCC cells. Spalt-like transcription factor 4 (SALL4), a fetal oncoprotein expressed in aggressive HCCs, is specifically targeted as a case study to evaluate the efficacy of HPPS carrying siRNA cargo. HPPS containing different formulations of siRNA therapy against SALL4 were generated specifically for HCC cells. These were investigated both in vitro and in vivo using fluorescence imaging. HPPS-SALL4 effectively bound to scavenger receptor, class B type 1 (SR-BI) and delivered the siRNA cargo into HCC cells, as seen in vitro. HPPS-SALL4 effectively inhibited HCC tumor growth (P < 0.05) and induced a 3-fold increase in apoptosis of the cancer cells in vivo compared to HPPS-scramble. Additionally, there was no immunogenicity associated with HPPS-SALL4 as measured by cytokine production. Conclusion: We have developed unique HDL-like nanoparticles that directly deliver RNA interference (RNAi) therapy against SALL4 into the cytosol of HCC cells, effectively inhibiting HCC tumor growth without any systemic immunogenicity. This therapeutic modality avoids the need for hepatic metabolism in this cancer, which develops in the setting of cirrhosis and liver dysfunction. These natural lipoprotein-like nanoparticles with RNAi therapy are a promising therapeutic strategy for HCC.

The SR-B1 Receptor as a Potential Target for Treating Glioblastoma

Purpose

The goal of these studies was to provide proof of concept for a novel targeted therapy for Glioblastoma Multiforme (GBM). Methods. These studies involve the evaluation of reconstituted high density lipoprotein (rHDL) nanoparticles (NPs) as delivery agents for the drug, mammalian Target of Rapamycin (mTOR) inhibitor Everolimus (EVR) to GBM cells. Cytotoxicity studies and assessment of downstream effects, including apoptosis, migration, and cell cycle events, were probed, in relation to the expression of scavenger receptor B type 1 (SR-B1) by GBM cells.

Results

Findings from cytotoxicity studies indicate that the rHDL/EVR formulation was 185 times more potent than free EVR against high SR-B1 expressing cell line (LN 229). Cell cycle analysis revealed that rHDL/EVR treated LN229 cells had a 5.8 times higher apoptotic cell population than those treated with EVR. The sensitivity of GBM cells to EVR treatment was strongly correlated with SR-B1 expression.

Conclusions

These studies present strong proof of concept regarding the efficacy of delivering EVR and likely other agents, via a biocompatible transport system, targeted to the SR-B1 receptor that is upregulated in most cancers, including GBM. Targeting the SR-B1 receptor could thus lead to effective personalized therapy of GBM.

Tailoring Porphyrin Conjugation for Nanoassembly-Driven Phototheranostic Properties

Lipoprotein mimetic nanostructures, which consist of an amphiphilic lipid shell, a hydrophobic core, and an apolipoprotein mimetic peptide, serve as a versatile platform for the design of drug delivery vehicles as well as the investigation of supramolecular assemblies. Porphyrin incorporation into biomimetic lipoproteins allows one to take advantage of the inherent multimodal photophysical properties of porphyrins, yielding various fluorescence, photoacoustic, and photodynamic agents. To facilitate their incorporation into a lipoprotein structure, porphyrins have been conjugated through a variety of strategies. However, the effects of the conjugate structure on the associated nanoparticle's phototherapeutic properties warrants further investigation. Herein, we systematically investigated the effects of two widely utilized porphyrin conjugates, oleylamide and lipid, on biophotonic properties of their resultant porphyrin-lipoprotein nanoparticles in vitro and in vivo. Specifically, we demonstrated that incorporation of the porphyrin moiety as an oleylamide conjugate leads to a highly stable J-aggregate with strong photoacoustic contrast, while incorporation as an ampiphilic lipid moiety into the lipid shell yields an effective fluorescent and photodynamic agent. The current study proposes a rational design strategy for next-generation lipoprotein-based phototheranostic agents, for which nanoassembly-driven biophotonic and therapeutic properties can be tailored through the specific selection of porphyrin conjugate structures.

Lipoproteins for therapeutic delivery: recent advances and future opportunities

The physiological role(s) of mammalian plasma lipoproteins is to transport hydrophobic molecules (primarily cholesterol and triacylglycerols) to their respective destinations. Lipoproteins have also been studied as drug-delivery agents due to their advantageous payload capacity, long residence time in the circulation and biocompatibility. The purpose of this review is to briefly discuss current findings with the focus on each type of formulation's potential for clinical applications. Regarding utilizing lipoprotein type formulation for cancer therapeutics, their potential for tumor-selective delivery is also discussed.

Reconstituted high-density lipoproteins: novel biomimetic nanocarriers for drug delivery

High-density lipoproteins (HDL) are naturally-occurring nanoparticles that are biocompatible, non-immunogenic and completely biodegradable. These endogenous particles can circulate for an extended period of time and transport lipids, proteins and microRNA from donor cells to recipient cells. Based on their intrinsic targeting properties, HDL are regarded as promising drug delivery systems. In order to produce on a large scale and to avoid blood borne pollution, reconstituted high-density lipoproteins (rHDL) possessing the biological properties of HDL have been developed. This review summarizes the biological properties and biomedical applications of rHDL as drug delivery platforms. It focuses on the emerging approaches that have been developed for the generation of biomimetic nanoparticles rHDL to overcome the biological barriers to drug delivery, aiming to provide an alternative, promising avenue for efficient targeting transport of nanomedicine.

Personalized siRNA-Nanoparticle Systemic Therapy using Metastatic Lymph Node Specimens Obtained with EBUS-TBNA in Lung Cancer

Inhibiting specific gene expression with siRNA provides a new therapeutic strategy to tackle many diseases at the molecular level. Recent strategies called high-density lipoprotein (HDL)-mimicking peptide-phospholipid nanoscaffold (HPPS) nanoparticles have been used to induce siRNAs-targeted delivery to scavenger receptor class B type I receptor (SCARB1)-expressing cancer cells with high efficiency. Here, eight ideal therapeutic target genes were identified for advanced lung cancer throughout the screenings using endobronchial ultrasonography-guided transbronchial needle aspiration (EBUS-TBNA) and the establishment of a personalized siRNA-nanoparticle therapy. The relevance of these genes was evaluated by means of siRNA experiments in cancer cell growth. To establish a therapeutic model, kinesin family member-11 (KIF11) was selected as a target gene. A total of 356 lung cancers were analyzed immunohistochemically for its clinicopathologic significance. The antitumor effect of HPPS-conjugated siRNA was evaluated in vivo using xenograft tumor models. Inhibition of gene expression for these targets effectively suppressed lung cancer cell growth. SCARB1 was highly expressed in a subset of tumors from the lung large-cell carcinoma (LCC) and small-cell lung cancer (SCLC) patients. High-level KIF11 expression was identified as an independent prognostic factor in LCC and squamous cell carcinoma (SqCC) patients. Finally, a conjugate of siRNA against KIF11 and HPPS nanoparticles induced downregulation of KIF11 expression and mediated dramatic inhibition of tumor growth in vivoImplications: This approach showed delivering personalized cancer-specific siRNAs via the appropriate nanocarrier may be a novel therapeutic option for patients with advanced lung cancer. Mol Cancer Res; 16(1); 47-57. ©2017 AACR.

Targeting SR-BI for Cancer Diagnostics, Imaging and Therapy

Scavenger receptor class B type I (SR-BI) plays an important role in trafficking cholesteryl esters between the core of high density lipoprotein and the liver. Interestingly, this integral membrane protein receptor is also implicated in the metabolism of cholesterol by cancer cells, whereby overexpression of SR-BI has been observed in a number of tumors and cancer cell lines, including breast and prostate cancers. Consequently, SR-BI has recently gained attention as a cancer biomarker and exciting target for the direct cytosolic delivery of therapeutic agents. This brief review highlights these key developments in SR-BI-targeted cancer therapies and imaging probes. Special attention is given to the exploration of high density lipoprotein nanomimetic platforms that take advantage of upregulated SR-BI expression to facilitate targeted drug-delivery and cancer diagnostics, and promising future directions in the development of these agents.

Lipoprotein based drug delivery: Potential for pediatric cancer applications

While survival rates for patients with childhood cancers have substantially improved, the quality of life of the survivors is often adversely impacted by the residual effects of chemo and radiation therapy. Because of the existing metabolic and physiological disparities between pediatric and adult patients, the treatment of pediatric cancer patients poses special challenges to oncologists. While numerous clinical trials being conducted, to improve treatment outcomes for pediatric cancer patients, new approaches are required to increase the efficacy and to minimize the drug related toxic side effects. Nanotechnology is a potentially effective tool to overcome barriers to effective cancer therapeutics including poor bioavailability and non-specific targeting. Among the nano-delivery approaches, lipoprotein based formulations have shown particularly strong promise to improve cancer therapeutics. The present article describes the challenges faced in the treatment of pediatric cancers and reviews the potential of lipoprotein-based therapeutics for these malignancies.

Learning from biology: synthetic lipoproteins for drug delivery

Synthetic lipoproteins represent a relevant tool for targeted delivery of biological/chemical agents (chemotherapeutics, siRNAs, photosensitizers, and imaging contrast agents) into various cell types. These nanoparticles offer a number of advantages for drugs delivery over their native counterparts while retaining their natural characteristics and biological functions. Their ultra-small size (<30 nm), high biocompatibility, favorable circulation half-life, and natural ability to bind specific lipoprotein receptors, i.e., low-density lipoprotein receptor (LDLR) and Scavenger receptor class B member 1 (SRB1) that are found in a number of pathological conditions (e.g., cancer, atherosclerosis), make them superior delivery strategies when compared with other nanoparticle systems. We review the various approaches that have been developed for the generation of synthetic lipoproteins and their respective applications in vitro and in vivo. More specifically, we summarize the approaches employed to address the limitation on use of reconstituted lipoproteins by means of natural or recombinant apolipoproteins, as well as apolipoprotein mimetic molecules. Finally, we provide an overview of the advantages and disadvantages of these approaches and discuss future perspectives for clinical translation of these nanoparticles.

Dendrimerlike mesoporous silica nanoparticles as pH-responsive nanocontainers for targeted drug delivery and bioimaging

In this work, we employed dendrimerlike mesoporous silica nanoparticles with hierarchical pores (HPSNs) to fabricate drug delivery system bioimaging and targeted tumor therapy in vivo. N,N-phenylenebis(salicylideneimine)dicarboxylic acid (Salphdc) was used both as the gatekeeper of HPSNs via pH-responsive coordination bonds between -COOH of Salphdc and In(3+) ions and as a fluorescence imaging agent. Folic acid was then conjugated to Salphdc as the targeting unit. The results revealed that the system could deliver model drug DOX to the tumor site with high efficiency and then cause cell apoptosis and tumor growth inhibition. Moreover, the conjugated Salphdc was proved to be a promising fluorescence probe for tracing distribution of the system in vivo. The study affords a potential nanoconainer for cancer therapy and biological imaging.

A PEGylation-Free Biomimetic Porphyrin Nanoplatform for Personalized Cancer Theranostics

PEGylation (PEG) is the most commonly adopted strategy to prolong nanoparticles' vascular circulation by mitigating the reticuloendothelial system uptake. However, there remain many concerns in regards to its immunogenicity, targeting efficiency, etc., which inspires pursuit of alternate, non-PEGylated systems. We introduced here a PEG-free, porphyrin-based ultrasmall nanostructure mimicking nature lipoproteins, termed PLP, that integrates multiple imaging and therapeutic functionalities, including positron emission tomography (PET) imaging, near-infrared (NIR) fluorescence imaging and photodynamic therapy (PDT). With an engineered lipoprotein-mimicking structure, PLP is highly stable in the blood circulation, resulting in favorable pharmacokinetics and biodistribution without the need of PEG. The prompt tumor intracellular trafficking of PLP allows for rapid nanostructure dissociation upon tumor accumulation to release monomeric porphyrins to efficiently generate fluorescence and photodynamic reactivity, which are highly silenced in intact PLP, thus providing an activatable mechanism for low-background NIR fluorescence imaging and tumor-selective PDT. Its intrinsic copper-64 labeling feature allows for noninvasive PET imaging of PLP delivery and quantitative assessment of drug distribution. Using a clinically relevant glioblastoma multiforme model, we demonstrated that PLP enabled accurate delineation of tumor from surrounding healthy brain at size less than 1 mm, exhibiting the potential for intraoperative fluorescence-guided surgery and tumor-selective PDT. Furthermore, we demonstrated the general applicability of PLP for sensitive and accurate detection of primary and metastatic tumors in other clinically relevant animal models. Therefore, PLP offers a biomimetic theranostic nanoplatform for pretreatment stratification using PET and NIR fluorescence imaging and for further customized cancer management via imaging-guided surgery, PDT, or/and potential chemotherapy.

Theranostic lipid nanoparticles for cancer medicine

Disease heterogeneity within and between patients necessitates a patient-focused approach to cancer treatment. This exigency forms the basis for the medical practice termed personalized medicine. An emerging, important component of personalized medicine is theranostics. Theranostics describes the co-delivery of therapeutic and imaging agents in a single formulation. Co-delivery enables noninvasive, real-time visualization of drug fate, including drug pharmacokinetic and biodistribution profiles and intratumoral accumulation. These technological advances assist drug development and ultimately may translate to improved treatment planning at the bedside. Nanocarriers are advantageous for theranostics as their size and versatility enables integration of multiple functional components in a single platform. This chapter focuses on recent developments in advanced lipid theranostic nanomedicine from the perspective of the "all-in-one" or the "one-for-all" approach. The design paradigm of "all-in-one" is the most common approach for assembling theranostic lipid nanoparticles, where the advantages of theranostics are achieved by combining multiple components that each possesses a specific singular function for therapeutic activity or imaging contrast. We will review lipoprotein nanoparticles and liposomes as representatives of the "all-in-one" approach. Complementary to the "all-in-one" approach is the emerging paradigm of the "one-for-all" approach where nanoparticle components are intrinsically multifunctional. We will discuss the "one-for-all" approach using porphysomes as a representative. We will further discuss how the concept of "one-for-all" might overcome the regulatory hurdles facing theranostic lipid nanomedicine.

Synthetic high-density lipoprotein-like nanoparticles for cancer therapy

High-density lipoproteins (HDLs) are a diverse group of natural nanoparticles that are most well known for their role in cholesterol transport. However, HDLs have diverse functions that provide significant opportunities for cancer therapy. Presented is a focused review of the ways that synthetic versions of HDL have been used as targeted therapies for cancer, and as vehicles for the delivery of diverse therapeutic cargo to cancer cells. As such, synthetic HDLs are likely to play a central role in the development of next-generation cancer therapies.

Nasopharyngeal cancer-specific therapy based on fusion peptide-functionalized lipid nanoparticles

Current treatment of advanced-stage nasopharyngeal carcinoma (NPC) is not satisfactory. Targeted therapies offer hope for extending survival. Here, we developed simple, robust, and NPC-specific therapeutic lipid nanoparticles based on a fusion peptide, α-NTP, made up of an amphipathic α-helical peptide (α-peptide) linked to an NPC-specific therapeutic peptide (NTP). We found that α-NTP not only retained the sub-30 nm nanostructure-controlling ability of the α-peptide but also displayed the enhanced NPC-targeting ability of the NTP, in which the α-peptide accelerated the uptake of the NTP by NPC cells, with a 4.8-fold increase. Following uptake, α-NTP-based lipid nanoparticles (α-NTP-LNs) exerted coordinated cytotoxicity by inducing cell death via apoptosis and autophagy. In vivo and ex vivo optical imaging data showed that systemically administered α-NTP-LNs efficiently accumulated in the NPC xenograft tumor and displayed high contrast between tumor and normal tissues, which was further confirmed by flow cytometry that there had been a 13-fold uptake difference between tumor cells and hepatocytes. More importantly, the therapeutic efficacy of α-NTP-LNs was specific to NPC xenograft formed with 5-8F cells but not to fibrosarcoma xenograft formed with HT1080 cells in vivo. The growth of 5-8F tumors was significantly inhibited by α-NTP-LNs, with more than 85% inhibition relative to control groups (e.g., α-NTP and PBS treatment). In a lung metastasis model of NPC, survival was significantly improved by α-NTP-LN treatment. In a word, these excellent properties of α-NTP-LNs worked in sync and synergistically, maximizing the therapeutic efficacy of α-NTP-LNs against NPC and its metastasis.

PEG-stabilized bilayer nanodisks as carriers for doxorubicin delivery

Spherical nanoparticles as a classic delivery vehicle for anticancer drugs have been extensively investigated, but study on the shape of nanoparticles has received little attention until now. Here, a nonspherical poly(ethylene glycol) (PEG)-stabilized bilayer nanodisk consisting of 1,2-distearyl-sn-glycero-3-phosphocholine (DSPC) and PEG5000-glyceryl distearate (PEG5K-GCDS) was prepared for doxorubicin delivery, called DOX-Disks. The prepared disks were open bilayer structures, with a hydrophobic discoid center built by DSPC and a hydrophilic PEG edge. Mean particle diameter of the disk was 80.14 nm, and the disk height was about 6 nm with aspect ratio about 12. Encapsulation efficiency of DOX-Disks was as high as 96.1%, and DOX release from DOX-Disks was pH-dependent (25.6% of total DOX released at 24 h in pH 7.4). The pharmacokinetic performances showed that DOX-Disks demonstrated long circulation time in blood and larger AUC (11.7-fold of t1/2 and 31.7-fold of AUC) in rats compared with DOX solutions (DOX-Sol). Tissue distribution in H22 tumor bearing mice demonstrated higher tumor accumulation (9.7-fold) and lower heart toxicities (25.7-fold) at 48 h after iv administration, in comparison with DOX-Sol. In addition, DOX-Disks exhibited much effectiveness in inhibiting tumor cell growth, and the IC50 values were 2.03, 0.85, and 0.86 μg/mL for DOX-Sol and 0.23, 0.24, and 0.20 μg/mL for DOX-Disks after treatment for 48, 72, and 96 h against MCF-7/Adr cells, respectively. DOX-Disks were taken up into MCF-7/Adr cells via energy-dependent endocytosis processes, involved in clathrin-mediated, macropinocytosis-mediated, and non-clathrin- and non-caveolae-mediated endocytosis pathways. In summary, such PEG-stabilized bilayer nanodisks could be one of the promising carriers for antitumor drugs via extended blood circulation and improved tumor distribution.

Development and evaluation of transferrin-stabilized paclitaxel nanocrystal formulation

The aim of the present study was to prepare and evaluate a paclitaxel nanocrystal-based formulation stabilized by serum protein transferrin in a non-covalent manner. The pure paclitaxel nanocrystals were first prepared using an antisolvent precipitation method augmented by sonication. The serum protein transferrin was selected for use after evaluating the stabilizing effect of several serum proteins including albumin and immunoglobulin G. The formulation contained approximately 55-60% drug and was stable for at least 3months at 4°C. In vivo antitumor efficacy studies using mice inoculated with KB cells demonstrate significantly higher tumor inhibition rate of 45.1% for paclitaxel-transferrin formulation compared to 28.8% for paclitaxel nanosuspension treatment alone. Interestingly, the Taxol(®) formulation showed higher antitumor activity than the paclitaxel-transferrin formulation, achieving a 93.3% tumor inhibition rate 12days post initial dosing. However, the paclitaxel-transferrin formulation showed a lower level of toxicity, which is indicated by a steady increase in body weight of mice over the treatment period. In comparison, treatment with Taxol(®) resulted in toxicity issues as body weight decreased. These results suggest the potential benefit of using a serum protein in a non-covalent manner in conjunction with paclitaxel nanocrystals as a promising drug delivery model for anticancer therapy.

Lipid-based nanoparticles in the systemic delivery of siRNA

RNAi therapeutics are believed to be the future of personalized medicine and have shown promise in early clinical trials. However, many physiological barriers exist in the systemic delivery of siRNAs to the cytoplasm of targeted cells to perform their function. To overcome these barriers, many siRNA delivery systems have been developed. Among these, lipid-based nanoparticles have great potential owing to their biocompatibility and low toxicity in comparison with inorganic nanoparticles and viral systems. This review discusses the hurdles of systemic siRNA delivery and highlights the recent progress made in lipid-based nanoparticles, which are categorized based on their key lipid components, including cationic lipid, lipoprotein, lipidoid, neutral lipid and anionic lipid-based nanoparticles. It is expected that these lipid nanoparticle-based siRNA delivery systems will have an enabling role for personalized cancer medicine, where siRNA delivery will join forces with genetic profiling of individual patients to achieve the best treatment outcome.

Hybrid melittin cytolytic Peptide-driven ultrasmall lipid nanoparticles block melanoma growth in vivo

The cytolytic peptide melittin is a potential anticancer candidate that may be able to overcome tumor drug resistance due to its lytic properties. However, in vivo applications of melittin are limited due to its main side effect, hemolysis, which is especially pronounced following intravenous administration. Here, we designed a hybrid cytolytic peptide, α-melittin, in which the N-terminus of melittin is linked to the C-terminus of an amphipathic α-helical peptide (α-peptide) via a GSG linker. The strong α-helical configuration allows α-melittin to interact with phospholipids and self-assemble into lipid nanoparticles, with a high efficiency for α-melittin encapsulation (>80%) and a strong ability to control the structure of the nanoparticle (~20 nm). This α-melittin-based lipid nanoparticle (α-melittin-NP) efficiently shields the positive charge of melittin (18.70 ± 0.90 mV) within the phospholipid monolayer, resulting in the generation of a neutral nanoparticle (2.45 ± 0.56 mV) with reduced cytotoxicity and a widened safe dosage range. Confocal imaging data confirmed that α-melittin peptides were efficiently released from the nanoparticles and were cytotoxic to the melanoma cells. Finally, α-melittin-NPs were administered to melanoma-bearing mice via intravenous injection. The growth of the melanoma cells was blocked by the α-melittin-NPs, with an 82.8% inhibition rate relative to the PBS-treated control group. No side effects of treatment were found in this study. Thus, the excellent properties of α-melittin-NP give it potential clinical applications in solid tumor therapeutics through intravenous administration.

Scavenger receptor B1 is a potential biomarker of human nasopharyngeal carcinoma and its growth is inhibited by HDL-mimetic nanoparticles

Nasopharyngeal carcinoma (NPC) is a very regional malignant head and neck cancer that has attracted widespread attention for its unique etiology, epidemiology and therapeutic options. To achieve high cure rates in NPC patients, theranostic approaches are actively being pursued and improved efforts remain desirable in identifying novel biomarkers and establishing effective therapeutic approaches with low long-term toxicities. Here, we discovered that the scavenger receptor class B type I (SR-B1) was overexpressed in all investigated NPC cell lines and 75% of NPC biopsies, demonstrating that SR-B1 is a potential biomarker of NPC. Additional functional analysis showed that SR-B1 has great effect on cell motility while showing no significant impact on cell proliferation. As high-density lipoproteins (HDL) exhibit strong binding affinities to SR-B1 and HDL mimetic peptides are reportedly capable of inhibiting tumor growth, we further examined the SR-B1 targeting ability of a highly biocompatible HDL-mimicking peptide-phospholipid scaffold (HPPS) nanocarrier and investigated its therapeutic effect on NPC. Results show that NPC cells with higher SR-B1 expression have superior ability in taking up the core constituents of HPPS. Moreover, HPPS inhibited the motility and colony formation of 5-8F cells, and significantly suppressed the NPC cell growth in nude mice without inducing tumor cell necrosis or apoptosis. These results indicate that HPPS is not only a NPC-targeting nanocarrier but also an effective anti-NPC drug. Together, the identification of SR-B1 as a potential biomarker and the use of HPPS as an effective anti-NPC agent may shed new light on the diagnosis and therapeutics of NPC.

Imaging the cytosolic drug delivery mechanism of HDL-like nanoparticles

PURPOSE

Molecular therapeutics often require an effective nanoparticle-based delivery strategy to transport them to cytosolic organelles to be functional. Recently, a cytosolic delivery strategy based on the scavenger receptor class B type I (SR-BI) mediated pathway has shown great potential for the effective delivery of theranostics agents into the cytoplasm of cells without detrimental endosomal entrapment. This study elucidates this unique delivery mechanism for improving cytosolic drug delivery.

METHODS

Multifluorophore-labeled HDL-mimicking peptide phospholipid scaffold (HPPS) nanoparticles were developed. Fluorescence imaging was utilized to examine HPPS transporting payloads into cells step by step through sequential inhibition studies.

RESULTS

HPPS specifically recognizes and binds to SR-BI, then interacts with SR-BI, which results in direct transport of payload molecules into the cell cytoplasm without entire particles internalization. The cytosolic transport of payloads occurred through a temperature- and energy-independent pathway, and was also different from actin- and clathrin-mediated endocytosis. Furthermore, this transport was significantly inhibited by disruption of lipid rafts using filipin or methyl-β-cyclodextrin.

CONCLUSIONS

The cytosolic delivery of payloads by HPPS via SR-BI targeting is predominately mediated through a lipid rafts/caveolae-like pathway. This cytosolic delivery strategy can be utilized for transporting molecular therapeutics that require their action sites to be within cytosolic organelles to enhance therapeutic effect.

Pre-Clinical Evaluation of rHDL Encapsulated Retinoids for the Treatment of Neuroblastoma

Despite major advances in pediatric cancer research, there has been only modest progress in the survival of children with high risk neuroblastoma (NB) (HRNB). The long term survival rates of HRNB in the United States are still only 30-50%. Due to resistance that often develops during therapy, development of new effective strategies is essential to improve the survival and overcome the tendency of HRNB patients to relapse subsequent to initial treatment. Current chemotherapy regimens also have a serious limitation due to off target toxicity. In the present work, we evaluated the potential application of reconstituted high density lipoprotein (rHDL) containing fenretinide (FR) nanoparticles as a novel approach to current NB therapeutics. The characterization and stability studies of rHDL-FR nanoparticles showed small size (<40 nm) and high encapsulation efficiency. The cytotoxicity studies of free FR vs. rHDL/FR toward the NB cell lines SK-N-SH and SMS-KCNR showed 2.8- and 2-fold lower IC50 values for the rHDL encapsulated FR vs. free FR. More importantly, the IC50 value for retinal pigment epithelial cells (ARPE-19), a recipient of off target toxicity during FR therapy, was over 40 times higher for the rHDL/FR as compared to that of free FR. The overall improvement in in vitro selective therapeutic efficiency was thus about 100-fold upon encapsulation of the drug into the rHDL nanoparticles. These studies support the potential value of this novel drug delivery platform for treating pediatric cancers in general, and NB in particular.

QUANTIFYING NANOPARTICLE TRANSPORT IN VIVO USING HYPERSPECTRAL IMAGING WITH A DORSAL SKINFOLD WINDOW CHAMBER

We have developed a noninvasive imaging method to quantify in vivo drug delivery pharmacokinetics without the need for blood or tissue collection to determine drug concentration. By combining the techniques of hyperspectral imaging and a dorsal skinfold window chamber, this method enabled the real-time monitoring of vascular transport and tissue deposition of nanoparticles labeled with near-infrared (NIR) dye. Using this imaging method, we quantified the delivery pharmacokinetics of the native high-density lipoprotein (HDL) and epidermal growth factor receptor (EGFR)-targeted HDL nanoparticles and demonstrated these HDLs had long circulation time in blood stream (half-life >12 h). These HDL nanoparticles could efficiently carry cargo DiR-BOA to extravasate from blood vessels, diffuse through extracellular matrix, and penetrate and be retained in the tumor site. The EGFR targeting specificity of EGFR-targeted HDL (EGFR-specific peptide conjugated HDL) was also visualized in vivo by competitive inhibition with excess EGFR-specific peptide. In summary, this imaging technology may help point the way toward the development of novel imaging-based pharmacokinetic assays for preclinical drugs and evaluation of drug delivery efficiency, providing a dynamic window into the development and application of novel drug delivery systems.

Drug delivery via lipoprotein-based carriers: answering the challenges in systemic therapeutics

Plasma lipoproteins are transporters of lipids and other hydrophobic molecules in the mammalian circulation. Lipoproteins also have a strong potential to serve as drug-delivery vehicles due to their small size, long residence time in the circulation and high-drug payload. Consequently, lipoproteins and synthetic/reconstituted lipoprotein preparations have been evaluated with increasing interest towards clinical applications, particularly for cancer diagnostics/imaging and chemotherapy. In this review, past and current studies on lipoproteins and similar alternative drug carriers are discussed regarding their suitability as agents to deliver drugs, primarily to cancer cells and tumors. A lipoprotein-based delivery strategy may also provide a novel platform for improving the therapeutic efficacy of drugs that have previously been judged unsuitable or had only limited application due to poor solubility. An additional, and perhaps the most important aspect of the drug-delivery process via lipoprotein-type carriers, is the receptor-mediated uptake of the payload from the lipoprotein complex. Monitoring the expression of specific receptors prior to treatment could, thus, give rise to efficient selection of optimally responsive patients, resulting in a successful personalized therapy regimen.

Efficient systemic delivery of siRNA by using high-density lipoprotein-mimicking peptide lipid nanoparticles

The main challenge for RNAi therapeutics lies in systemic delivery of siRNA to the correct tissues and transporting them into the cytoplasm of targeted cells, at safe, therapeutic levels. Recently, we developed a high-density lipoprotein-mimicking peptide-phospholipid scaffold (HPPS) and demonstrated its direct cytosolic delivery of siRNA in vitro, thereby bypassing endosomal trapping.

AIM

We investigate the in vivo implementation of HPPS for siRNA delivery.

METHOD & RESULTS

After systemic administration in KB tumor-bearing mice, HPPS prolonged the blood circulation time of cholesterol-modified siRNA (chol-siRNA) by a factor of four, improved its biodistribution and facilitated its uptake in scavenger receptor class B type I overexpressed tumors. For therapeutic targeting to the bcl-2 gene, the HPPS-chol-si-bcl-2 nanoparticles downregulated Bcl-2 protein, induced enhanced apoptosis (2.5-fold) in tumors when compared with controls (saline, HPPS, HPPS-chol-si-scramble and chol-si-bcl-2) and significantly inhibited tumor growth with no adverse effect.

CONCLUSION

HPPS is a safe, efficient nanocarrier for RNAi therapeutics in vivo.

Physical properties and biocompatibility of a core-sheath structure composite scaffold for bone tissue engineering in vitro

Scaffolds play a critical role in the practical realization of bone tissue engineering. The purpose of this study was to assess whether a core-sheath structure composite scaffold possesses admirable physical properties and biocompatibility in vitro. A novel scaffold composed of poly(lactic-co-glycolic acid)/β-tricalcium phosphate (PLGA/β-TCP) skeleton wrapped with Type I collagen via low-temperature deposition manufacturing (LDM) was prepared, and bone mesenchymal stem cells (BMSCs) were used to evaluate cell behavior on the scaffold. PLGA/β-TCP skeleton was chosen as the control group. Physical properties were evaluated by pority ratio, compressive strength, and Young's modulus. Scanning electron microscope (SEM) was used to study morphology of cells. Hydrophilicity was evaluated by water absorption ratio. Cell proliferation was tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay (MTT). Osteogenic differentiation of BMSCs was evaluated by alkaline phosphates activity (ALP). The results indicated that physical properties of the novel scaffold were as good as those of the control group, hydrophilicity was observably better (P < 0.01) than that of control group, and abilities of proliferation and osteogenic differentiation of BMSCs on novel scaffold were significantly greater (P < 0.05) than those of control group, which suggests that the novel scaffold possesses preferable characteristics and have high value in bone tissue engineering.

Lipoprotein-inspired nanoparticles for cancer theranostics

Over hundreds of millions of years, animals have evolved endogenous lipoprotein nanoparticles for shuttling hydrophobic molecules to different parts of the body. In the last 70 years, scientists have developed an understanding of lipoprotein function, often in relationship to lipid transport and heart disease. Such biocompatible, lipid–protein complexes are also ideal for loading and delivering cancer therapeutic and diagnostic agents, which means that lipoprotein and lipoprotein-inspired nanoparticles also offer opportunities for cancer theranostics. By mimicking the endogenous shape and structure of lipoproteins, the nanocarrier can remain in circulation for an extended period of time, while largely evading the reticuloendothelial cells in the body’s defenses. The small size (less than 30 nm) of the low-density (LDL) and high-density (HDL) classes of lipoproteins allows them to maneuver deeply into tumors. Furthermore, lipoproteins can be targeted to their endogenous receptors, when those are implicated in cancer, or to other cancer receptors.

In this Account, we review the field of lipoprotein-inspired nanoparticles related to the delivery of cancer imaging and therapy agents. LDL has innate cancer targeting potential and has been used to incorporate diverse hydrophobic molecules and deliver them to tumors. Nature’s method of rerouting LDL in atherosclerosis provides a strategy to extend the cancer targeting potential of lipoproteins beyond its narrow purview. Although LDL has shown promise as a drug nanocarrier for cancer imaging and therapy, increasing evidence indicates that HDL, the smallest lipoprotein, may also be of use for drug targeting and uptake into cancer cells. We also discuss how synthetic HDL-like nanoparticles, which do not include human or recombinant proteins, can deliver molecules directly to the cytoplasm of certain cancer cells, effectively bypassing the endosomal compartment. This strategy could allow HDL-like nanoparticles to be used to deliver drugs that have increased activity in the cytoplasm. Lipoprotein nanoparticles have evolved to be ideal delivery vehicles, and because of that specialized function, they have the potential to improve cancer theranostics.