Validation of the reconstituted high-density lipoprotein (rHDL) drug delivery platform using dilauryl fluorescein (DLF)

Nanostructured lipid carriers decorated with polyphosphate coated linear and loop cell-penetrating peptides

AIM

This study aimed to evaluate the cellular uptake of nanostructured lipid carriers (NLCs) decorated with polyphosphate coated linear and loop cell-penetrating peptides (CPPs).

METHODS

Linear-CPPs and loop-CPPs were synthesized via ring-opening polymerization and anchored on the surface NLCs, followed by coating with polyphosphate (PP). These nanocarriers (NCs) were characterized in terms of particle size, polydispersity index (PDI), and zeta potential. Cell viability and hemolysis, as well as enzyme-induced charge conversion via phosphate cleavage by free and membrane-bound intestinal alkaline phosphatase (IAP) were investigated. Cellular uptake studies by Caco-2 and HEK cells were quantitatively analyzed by flow cytometry and visualized by confocal microscopy.

RESULTS

A shift in charge from positive to negative was obtained for both linear- and loop-CPPs-NLCs by coating with PP. PP-linear-CPPs-NLCs and PP-loop-CPPs-NLCs exhibited a particle size < 270 nm and a PDI of approximately 0.3. They had a minor effect on cell viability and caused in a concentration of 0.1 % (m/v) around 10 % hemolysis within 24 h. IAP triggered the cleavage and release of monophosphate from the surface of NLCs causing charge conversion from -22.2 mV to + 5.3 mV (Δ27.5 mV) for PP-linear-CPPs-NLCs and from -19.2 mV to + 11.9 mV (Δ31.1 mV) for PP-loop-CPPs-NLCs. Inhibition of alkaline phosphatase activity on Caco-2 and HEK cells confirmed the involvement of this enzyme in charge conversion. PP-linear-CPPs-NLCs showed on Caco-2 cells a higher uptake than PP-loop-CPPs-NLCs, whereas on HEK cells uptake of both types of NLCs was on the same level. The results of cellular uptake were confirmed visually by confocal microscopy.

CONCLUSION

CPPs-NLCs coated with polyphosphate are a promising approach to overcome the polycationic dilemma and to enhance cellular uptake.

Docosahexaenoic acid-loaded nanoparticles: A state-of-the-art of preparation methods, characterization, functionality, and therapeutic applications

Docosahexaenoic acid (DHA, C22:6 n-3), an omega-3 polyunsaturated fatty acid, offers several beneficial effects. DHA helps in reducing depression, autoimmune diseases, rheumatoid arthritis, attention deficit hyperactivity syndrome, and cardiovascular diseases. It can stimulate the development of brain and nerve, alleviate lipids metabolism-related disorders, and enhance vision development. However, DHA susceptibility to chemical oxidation, poor water solubility, and unpleasant order could restrict its applications for nutritional and therapeutic purposes. To avoid these drawbacks and enhance its bioavailability, DHA can be encapsulated using an effective delivery system. Several encapsulation methods are recognized, and DHA-loaded nanoparticles have demonstrated numerous benefits. In clinical studies, positive influences on the development of several diseases have been reported, but some assumptions are conflicting and need more exploration, since DHA has a systemic and not a targeted release at the required level. This might cause the applications of nanoparticles that could allow DHA release at the required level and improve its efficiency, thus resulting in a better controlling of several diseases. In the current review, we focused on researches investigating the formulation and development of DHA-loaded nanoparticles using different delivery systems, including low-density lipoprotein, zinc oxide, silver, zein, and resveratrol-stearate. Silver-DHA nanoparticles presented a typical particle size of 24 nm with an incorporation level of 97.67 %, while the entrapment efficiency of zinc oxide-DHA nanoparticles represented 87.3 %. By using zein/Poly (lactic-co-glycolic acid) stabilized nanoparticles, DHA's encapsulation level reached 84.6 %. We have also highlighted the characteristics, functionality and medical implementation of these nanoparticles in the treatment of inflammations, brain disorders, diabetes as well as hepatocellular carcinoma.

A Spontaneous Assembling Lipopeptide Nanoconjugate Transporting the Anthracycline Drug N-Benzyladriamycin-14-valerate for Personalized Therapy of Ewing Sarcoma

To meet the current need for a tumor-selective, targeted therapy regimen associated with reduced toxicity, our laboratory has developed a spontaneously assembled nanostructure that resembles high-density lipoproteins (HDLs). These myristoyl-5A (MYR-5A) nanotransporters are designed to safely transport lipophilic pharmaceuticals, including a novel anthracycline drug (N-benzyladriamycin-14-valerate (AD198)). This formulation has been found to enhance the therapeutic efficacy and reduced toxicity of drugs in preclinical studies of 2D and 3D models of Ewing sarcoma (EWS) and cardiomyocytes. Our findings indicate that the MYR-5A/AD198 nanocomplex delivers its payload selectively to cancer cells via the scavenger receptor type B1 (SR-B1), thus providing a solid proof of concept for the development of an improved and highly effective, potentially personalized therapy for EWS while protecting against treatment-associated cardiotoxicity.

An innovative viewpoint on the existing and prospectiveness of SR-B1

Scavenger Receptor Class B Type 1 (SR-B1), a receptor protein expressed on the cell membrane, plays a crucial role in the metabolism and transport of cholesterol and other lipids, contributing significantly to the homeostasis of lipid levels within the body. Bibliometric analysis involves the application of mathematical and statistical methods to quantitatively analyze different types of documents. It involves the analysis of structural and temporal trends in scholarly articles, coupled with the identification of subject emphasis and variations. Through a bibliometric analysis, this study examines the historical background, current research trends, and future directions in the exploration of SR-B1. By offering insights into the research status and development of SR-B1, this paper aims to assist researchers in identifying novel pathways and areas of investigation in this field of study. Following the screening process, it can be concluded that research on SR-B1 has consistently remained a topic of significant interest over the past 17 years. Interestingly, SR-B1 has recently garnered attention in areas beyond its traditional research focus, including the field of cancer. The primary objective of this review is to provide a concise and accessible overview of the development process of SR-B1 that can help readers who are not well-versed in SR-B1 research quickly grasp its key aspects. Furthermore, this review aims to offer insights and suggestions to researchers regarding potential future research directions and areas of emphasis relating to SR-B1.

Mannose-Coated Reconstituted Lipoprotein Nanoparticles for the Targeting of Tumor-Associated Macrophages: Optimization, Characterization, and In Vitro Evaluation of Effectiveness

Reconstituted high-density lipoprotein nanoparticles (rHDL NPs) have been utilized as delivery vehicles to a variety of targets, including cancer cells. However, the modification of rHDL NPs for the targeting of the pro-tumoral tumor-associated macrophages (TAMs) remains largely unexplored. The presence of mannose on nanoparticles can facilitate the targeting of TAMs which highly express the mannose receptor at their surface. Here, we optimized and characterized mannose-coated rHDL NPs loaded with 5,6-dimethylxanthenone-4-acetic acid (DMXAA), an immunomodulatory drug. Lipids, recombinant apolipoprotein A-I, DMXAA, and different amounts of DSPE-PEG-mannose (DPM) were combined to assemble rHDL-DPM-DMXAA NPs. The introduction of DPM in the nanoparticle assembly altered the particle size, zeta potential, elution pattern, and DMXAA entrapment efficiency of the rHDL NPs. Collectively, the changes in physicochemical characteristics of rHDL NPs upon the addition of the mannose moiety DPM indicated that the rHDL-DPM-DMXAA NPs were successfully assembled. The rHDL-DPM-DMXAA NPs induced an immunostimulatory phenotype in macrophages pre-exposed to cancer cell-conditioned media. Furthermore, rHDL-DPM NPs delivered their payload more readily to macrophages than cancer cells. Considering the effects of the rHDL-DPM-DMXAA NPs on macrophages, the rHDL-DPM NPs have the potential to serve as a drug delivery platform for the selective targeting of TAMs.

Recent Development of LDL-Based Nanoparticles for Cancer Therapy

Low-density lipoprotein (LDL), a natural lipoprotein transporting cholesterol in the circulatory system, has been a possible drug carrier for targeted delivery. LDL can bind to the LDL receptor (LDLR) with its outside apolipoprotein B-100 and then enter the cell via LDLR-mediated endocytosis. This targeting function inspires researchers to modify LDL to deliver different therapeutic drugs. Drugs can be loaded in the surficial phospholipids, hydrophobic core, or apolipoprotein for the structure of LDL. In addition, LDL-like synthetic nanoparticles carrying therapeutic drugs are also under investigation for the scarcity of natural LDL. In addition to being a carrier, LDL can also be a targeting molecule, decorated to the surface of synthetic nanoparticles loaded with cytotoxic compounds. This review summarizes the properties of LDL and the different kinds of LDL-based delivery nanoparticles, their loading strategies, and the achievements of the recent anti-tumor advancement.

Targeted photodynamic therapy using reconstituted high-density lipoproteins as rhodamine transporters

Reconstituted high-density lipoprotein (rHDL) nanoparticles are excellent transporters of molecules and very useful for targeted therapy as they specifically recognize the scavenger receptor, class B1 (SR-B1) that is present on the surface of a wide range of tumor cells. However, they have rarely been employed to transport photosensitizers (PS) for photodynamic therapy (PDT). Rhodamine (R) compounds have been dismissed as useful PSs for PDT due to their low ¹O₂ production, excitation wavelengths with little tissue penetration, and poor selectivity for tumor cells. It was recently demonstrated that when irradiating at 532 nm or with Cerenkov radiation (CR) from a β-emitting radionuclide, R123, R6G, and RB undergo electron transfer reactions (type I reaction) with folic acid. R6G also produces type I reactions with O₂. In this work, the photodynamic effects of the rHDL-R system were evaluated in vitro. rHDL nanoparticles loaded with R123, R6G, and RB were synthesized, and the PS was internalized into T47D tumor cells. When cells were irradiated with a 532-nm laser in the presence of an rHDL-R systems, a cytotoxic photodynamic effect was obtained in the order R6G > R123 > RB. In the presence of CR from a ¹⁷⁷Lu source, cytotoxicity showed the order R6G > RB > R123. The higher cytotoxicity induced by R6G in both cases corresponds to higher cellular internalization and larger production of type I and II reactions. Thus, in this work, it is proposed that rHDL-R/¹⁷⁷Lu system can be applied in theragnostics as a multimodal radiotherapy-PDT-imaging system (imaging by SPECT or Cerenkov) and in hypoxic solid tumors in which external radiation is not effective and ¹⁷⁷Lu-CR acts as light source.

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.

Reconstituted HDL: Drug Delivery Platform for Overcoming Biological Barriers to Cancer Therapy

Drug delivery to malignant tumors is limited by several factors, including off-target toxicities and suboptimal benefits to cancer patient. Major research efforts have been directed toward developing novel technologies involving nanoparticles (NPs) to overcome these challenges. Major obstacles, however, including, opsonization, transport across cancer cell membranes, multidrug-resistant proteins, and endosomal sequestration of the therapeutic agent continue to limit the efficiency of cancer chemotherapy. Lipoprotein-based drug delivery technology, "nature's drug delivery system," while exhibits highly desirable characteristics, it still needs substantial investment from private/government stakeholders to promote its eventual advance to the bedside. Consequently, this review focuses specifically on the synthetic (reconstituted) high-density lipoprotein rHDL NPs, evaluating their potential to overcome specific biological barriers and the challenges of translation toward clinical utilization and commercialization. This highly robust drug transport system provides site-specific, tumor-selective delivery of anti-cancer agents while reducing harmful off-target effects. Utilizing rHDL NPs for anti-cancer therapeutics and tumor imaging revolutionizes the future strategy for the management of a broad range of cancers and other diseases.

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.

Photophysical characterization of anticancer drug valrubicin in rHDL nanoparticles and its use as an imaging agent

Nanoparticles are target-specific drug delivery agents that are increasingly used in cancer therapy to enhance bioavailability and to reduce off target toxicity of anti-cancer agents. Valrubicin is an anti-cancer drug, currently approved only for vesicular bladder cancer treatment because of its poor water solubility. On the other hand, valrubicin carrying reconstituted high density lipoprotein (rHDL) nanoparticles appear ideally suited for extended applications, including systemic cancer chemotherapy. We determined selected fluorescence properties of the free (unencapsulated) drug vs. valrubicin incorporated into rHDL nanoparticles. We have found that upon encapsulation into rHDL nanoparticles the quantum yield of valrubicin fluorescence increased six fold while its fluorescence lifetime increased about 2 fold. Accordingly, these and potassium iodide (KI) quenching data suggest that upon incorporation, valrubicin is localized deep in the interior of the nanoparticle, inside the lipid matrix. Fluorescence anisotropy of the rHDL valrubicin nanoparticles was also found to be high along with extended rotational correlation time. The fluorescence of valrubicin could also be utilized to assess its distribution upon delivery to prostate cancer (PC3) cells. Overall the fluorescence properties of the rHDL: valrubicin complex reveal valuable novel characteristics of this drug delivery vehicle that may be particularly applicable when used in systemic (intravenous) therapy.

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.

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.

Preparation, characterizations, and in vitro metabolic processes of paclitaxel-loaded discoidal recombinant high-density lipoproteins

Discoidal recombinant high-density lipoproteins (d-rHDLs) are attractive candidates for anticancer agents because of their favorable biocompatibility, biodegradability, and receptor-mediated endocytosis. Paclitaxel (PTX)-loaded d-rHDLs (P-d-rHDLs) were prepared by thin-film dispersion/detergent dialysis methods in this study. To investigate metabolic processes that P-d-rHDLs probably encounter in circulation, influences of lecithin-cholesterol acyltransferase (LCAT) on structural and compositional changes of P-d-rHDLs were studied in vitro. The shape of P-d-rHDLs converted from discoid into sphere, particle size increased, and cholesteryl ester (CE) generated simultaneously, which were referred to as remodeling behaviors. In vitro releases tests showed that release rate of PTX from P-d-rHDLs became faster when LCAT was added to P-d-rHDLs suspensions. Human breast cancer cells' cytotoxicity and cellular uptake of P-d-rHDLs were higher than liposomes and Taxol, and decreased in the presence of LCAT. Explorations of above phenomena found that drug entrapment did not influence remodeling processes induced by LCAT, whereas there was drug leakage occurring in remodeling processes. Therefore, drug leakage resulting from remodeling processes under the action of LCAT should be paid more attentions to when using d-rHDLs as drug vehicles for anticancer drugs. This study first focuses on metabolic processes of drug carriers and elucidates them through in vitro tests.

Enhanced solubility and functionality of valrubicin (AD-32) against cancer cells upon encapsulation into biocompatible nanoparticles

Among numerous drug-delivery approaches, reconstituted high-density lipoprotein (rHDL) nanocarriers have proven particularly applicable for delivering highly hydrophobic drugs. In this study, we have investigated the enhancement of the therapeutic impact of valrubicin (AD-32), an antineoplastic agent that has been limited to intravesicular application against bladder cancer, despite the encouraging original preclinical data. Earlier studies validated the superior therapeutic efficacy of AD-32 over doxorubicin. In the present study, rHDL/AD-32 nanoparticles were formulated and characterized with regard to encapsulation efficiency, physicochemical properties, selective toxicity, and receptor-mediated uptake. The half maximal inhibitory concentration values (IC₅₀) for rHDL/AD-32 nanoparticles were 1.8 and 2.6 times lower than the free AD-32 for prostate (PC-3) and ovarian (SKOV-3) cancer cell lines, respectively, whereas nonmalignant cell lines demonstrated 5 and 1.48 times higher IC₅₀ doses with rHDL/AD-32 formulations. The data obtained demonstrated effective receptor- mediated uptake of AD-32 from the rHDL nanocarriers by PC-3 and SKOV-3 cancer cells via a targeted drug-delivery process. The rHDL/AD-32 formulation was stable for 6 months when stored at 4°C or at −20°C, as 92% of the AD-32 was retained in the nanoparticles. The findings from this study show that the rHDL/AD-32 formulation can overcome the solubility barriers of AD-32 and thus serve as an effective systemically administered chemotherapeutic agent.