Structural characterisation of nucleoside loaded low density lipoprotein as a main criterion for the applicability as drug delivery system

LDL-Based Lipid Nanoparticle Derived for Blood Plasma Accumulates Preferentially in Atherosclerotic Plaque

Apolipoprotein-based drug delivery is a promising approach to develop safe nanoparticles capable of targeted drug delivery for various diseases. In this work, we have synthesized a lipid-based nanoparticle (NPs) that we have called “Aposomes” presenting native apolipoprotein B-100 (apoB-100), the primary protein present in Low-Density Lipoproteins (LDL) on its surface. The aposomes were synthesized from LDL isolated from blood plasma using a microfluidic approach. The synthesized aposomes had a diameter of 91 ± 4 nm and a neutral surface charge of 0.7 mV ± mV. Protein analysis using western blot and flow cytometry confirmed the presence of apoB-100 on the nanoparticle’s surface. Furthermore, Aposomes retained liposomes’ drug loading capabilities, demonstrating a prolonged release curve with ∼80% cargo release at 4 hours. Considering the natural tropism of LDL towards the atherosclerotic plaques, we evaluated the biological properties of aposomes in a mouse model of advanced atherosclerosis. We observed a ∼20-fold increase in targeting of plaques when comparing aposomes to control liposomes. Additionally, aposomes presented a favorable biocompatibility profile that showed no deviation from typical values in liver toxicity markers (i.e., LDH, ALT, AST, Cholesterol). The results of this study demonstrate the possibilities of using apolipoprotein-based approaches to create nanoparticles with active targeting capabilities and could be the basis for future cardiovascular therapies.

Lipoproteins-Nanocarriers as a Promising Approach for Targeting Liver Cancer: Present Status and Application Prospects

The prevalence of liver cancer is increasing over the years and it is the fifth leading cause of mortality worldwide. The intrusive features and burden of low survival rate make it a global health issue in both developing and developed countries. The recommended chemotherapy drugs for patients in the intermediate and advanced stages of various liver cancers yield a low response rate due to the nonspecific nature of drug delivery, thus warranting the search for new therapeutic strategies and potential drug delivery carriers. There are several new drug delivery methods available to ferry the targeted molecules to the specific biological environment. In recent years, the nano assembly of lipoprotein moieties (lipidic nanoparticles) has emerged as a promising and efficiently tailored drug delivery system in liver cancer treatment. This increased precision of nano lipoproteins conjugates in chemotherapeutic targeting offers new avenues for the treatment of liver cancer with high specificity and efficiency. This present review is focused on concisely outlining the knowledge of liver cancer diagnosis, existing treatment strategies, lipoproteins, their preparation, mechanism and their potential application in the treatment of liver cancer.

High Hydrostatic Pressure Induces a Lipid Phase Transition and Molecular Rearrangements in Low-Density Lipoprotein Nanoparticles

Low-density lipoproteins (LDL) are natural lipid transporter in human plasma whose chemically modified forms contribute to the progression of atherosclerosis and cardiovascular diseases accounting for a vast majority of deaths in westernized civilizations. For the development of new treatment strategies, it is important to have a detailed picture of LDL nanoparticles on a molecular basis. Through the combination of X-ray and neutron small-angle scattering (SAS) techniques with high hydrostatic pressure (HHP) this study describes structural features of normolipidemic, triglyceride-rich and oxidized forms of LDL. Due to the different scattering contrasts for X-rays and neutrons, information on the effects of HHP on the internal structure determined by lipid rearrangements and changes in particle shape becomes accessible. Independent pressure and temperature variations provoke a phase transition in the lipid core domain. With increasing pressure an inter-related anisotropic deformation and flattening of the particle are induced. All LDL nanoparticles maintain their structural integrity even at 3000 bar and show a reversible response toward pressure variations. The present work depicts the complementarity of pressure and temperature as independent thermodynamic parameters and introduces HHP as a tool to study molecular assembling and interaction processes in distinct lipoprotein particles in a nondestructive manner.

Synthetic lipoprotein as nano-material vehicle in the targeted drug delivery

High-density lipoprotein (HDL) and low-density lipoprotein (LDL), as human endogenous lipoprotein particles, have low toxicity, high selectivity, and good safety. They can avoid the recognition and clearance of human reticuloendothelial system. These synthetic lipoproteins (sLPs) have been attracted extensive attention as the nanovectors for tumor-targeted drug and gene delivery. Herein, recent advances in the field of anticancer based on these two lipid proteins and recombinant lipoproteins (rLPs) as target delivery vectors were analyzed and discussed.

Low density lipoprotein - rosiglitazone - chitosan-calcium alginate/nanoparticles inhibition of human tenon's fibroblasts activation and proliferation

Anti-fibrotic therapeutic methods with safety and efficiency after glaucoma filtration surgery (GFS) are desirable. In our previous study, by using Human Tenon's Fibroblasts (HTFs) as a model, we proved the expression of peroxisome proliferator activates receptor-γ (PPAR-γ) in HTFs; in addition, rosiglitazone (RSG), an agonist of PPAR-γ, can inhibit transforming growth factorsβ1 (TGF-β1)-induced reactivation of HTFs, thus to inhibit specifically scarring after GFS through intervening TGF-β/Smads signal pathway. However, a better drug delivery way of RSG, to prolong the duration of its function, and to reduce the toxicity of RSG to ocular tissue still remains challenges. Low density lipoprotein receptor (LDLr) is strongly expressed in hyper-proliferation HTFs after GFS. Therefore, we structured targeting LDL-RSG complexes and channel them into HTFs through LDL-LDLr pathway in order to promote anti-proliferation of HTFs and reduce the toxicity to ocular tissue. Meanwhile, in order to improve the release properties of LDL-RSG complexes, we structured slow release system of LDL-RSG/chitosan-calcium alginate - nanoparticles (CSNP), which effectively inhibited TGF-β1-induced HTFs proliferation, synthesis of extracellular matrix and activation of TGF-β1/SMAD pathway. These data suggested that LDL-RSG/CSNP can be a new anti-fibrotic therapeutic method on scarring after GFS and also a novelty administration of RSG.

Lipoprotein-Related and Apolipoprotein-Mediated Delivery Systems for Drug Targeting and Imaging

The integration of lipoprotein-related or apolipoprotein-targeted nanoparticles as pharmaceutical carriers opens new therapeutic and diagnostic avenues in nanomedicine. The concept is to exploit the intrinsic characteristics of lipoprotein particles as being the natural transporter of apolar lipids and fat in human circulation. Discrete lipoprotein assemblies and lipoprotein-based biomimetics offer a versatile nanoparticle platform that can be manipulated and tuned for specific medical applications. This article reviews the possibilities for constructing drug loaded, reconstituted or artificial lipoprotein particles. The advantages and limitations of lipoproteinbased delivery systems are critically evaluated and potential future challenges, especially concerning targeting specificity, concepts for lipoprotein rerouting and design of innovative lipoprotein mimetic particles using apolipoprotein sequences as targeting moieties are discussed. Finally, the review highlights potential medical applications for lipoprotein-based nanoparticle systems in the fields of cardiovascular research, cancer therapy, gene delivery and brain targeting focusing on representative examples from literature.

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.

In vitro and in vivo effects of free and chalcones-loaded nanoemulsions: insights and challenges in targeted cancer chemotherapies

Several obstacles are encountered in conventional chemotherapy, such as drug toxicity and poor stability. Nanotechnology is envisioned as a strategy to overcome these effects and to improve anticancer therapy. Nanoemulsions comprise submicron emulsions composed of biocompatible lipids, and present a large surface area revealing interesting physical properties. Chalcones are flavonoid precursors, and have been studied as cytotoxic drugs for leukemia cells that induce cell death by different apoptosis pathways. In this study, we encapsulated chalcones in a nanoemulsion and compared their effect with the respective free compounds in leukemia and in non-tumoral cell lines, as well as in an in vivo model. Free and loaded-nanoemulsion chalcones induced a similar anti-leukemic effect. Free chalcones induced higher toxicity in VERO cells than chalcones-loaded nanoemulsions. Similar results were observed in vivo. Free chalcones induced a reduction in weight gain and liver injuries, evidenced by oxidative stress, as well as an inflammatory response. Considering the high toxicity and the side effects induced generally by all cancer chemotherapies, nanotechnology provides some options for improving patients’ life quality and/or increasing survival rates.

Co-opting biology to deliver drugs

The goal of drug delivery is to improve the safety and therapeutic efficacy of drugs. This review focuses on delivery platforms that are either derived from endogenous pathways, long-circulating biomolecules and cells or that piggyback onto long-circulating biomolecules and cells. The first class of such platforms is protein-based delivery systems--albumin, transferrin, and fusion to the Fc domain of antibodies--that have a long-circulation half-life and are designed to transport different molecules. The second class is lipid-based delivery systems-lipoproteins and exosomes-that are naturally occurring circulating lipid particles. The third class is cell-based delivery systems--erythrocytes, macrophages, and platelets--that have evolved, for reasons central to their function, to exhibit a long life-time in the body. The last class is small molecule-based delivery systems that include folic acid. This article reviews the biology of these systems, their application in drug delivery, and the promises and limitations of these endogenous systems for drug delivery.

Low-density lipoprotein-mediated delivery of docosahexaenoic acid selectively kills murine liver cancer cells

AIM

The natural omega-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA), has recently been credited for possessing anticancer properties. Herein, we investigate the cytotoxic actions of DHA-loaded low-density lipoprotein (LDL) nanoparticles in normal and liver cancer cells.

MATERIALS & METHODS

LDL-DHA nanoparticles were prepared and subjected to extensive biophysical characterization. The therapeutic utility of LDL-DHA nanoparticles was evaluated in normal and malignant murine hepatocyte cell lines, TIB-73 and TIB-75, respectively.

RESULTS & DISCUSSION

The engineered LDL-DHA nanoparticles possessed enhanced physical and oxidative stabilities over native LDL and free DHA. Dose-response studies showed that therapeutic doses of LDL-DHA nanoparticles that completely killed TIB-75 were innocuous to TIB-73. The selective induction of lipid peroxidation and reactive oxygen species in the cancer cells was shown to play a central role in LDL-DHA nanoparticle-mediated cytotoxicity.

CONCLUSION

In summary, these findings indicate that LDL-DHA nanoparticles show great promise as a selective anticancer agent against hepatocellular carcinoma.

Human Plasma Very Low-Density Lipoproteins Are Stabilized by Electrostatic Interactions and Destabilized by Acidic pH

Very low-density lipoproteins (VLDL) are precursors of low-density lipoproteins (LDL, or “bad cholesterol”). Factors affecting structural integrity of VLDL are important for their metabolism. To assess the role of electrostatic interactions in VLDL stability, we determined how solvent ionic conditions affect the heat-induced VLDL remodeling. This remodeling involves VLDL fusion, rupture, and fission of apolipoprotein E-containing high-density lipoprotein-(HDL-) like particles similar to those formed during VLDL-to-LDL maturation. Circular dichroism and turbidity show that increasing sodium salt concentration in millimolar range reduces VLDL stability and its enthalpic component. Consequently, favorable electrostatic interactions stabilize VLDL. Reduction in pH from 7.4 to 6.0 reduces VLDL stability, with further destabilization detected at pH < 6, which probably results from titration of the N-terminal α-amino groups and free fatty acids. This destabilization is expected to facilitate endosomal degradation of VLDL, promote their coalescence into lipid droplets in atherosclerotic plaques, and affect their potential use as drug carriers.

Nanostructured nonionic thymidine nucleolipid self-assembly materials

Three nucleoside lipids have been synthesized: 3'-oleoylthymidine, 3',5'-dioleoylthymidine, and 3'-phytanoylthymidine. Differential scanning calorimetry and X-ray diffraction have been employed to characterize the physical properties of these neat lipids. Polarizing optical microscopy, small-angle X-ray scattering, and cryo-transmission electron microscopy techniques have been used to investigate the phase behavior in aqueous systems. Both oleoyl-based nucleoside lipids adopted a lamellar crystalline phase in the neat form at room temperature, and the phytanoyl derivative exhibited a fluid isotropic phase. Under excess water conditions, the presence of one branched (phytanoyl) or one unsaturated (oleoyl) chain promoted the formation of a liquid-crystalline lamellar phase at physiological temperatures. In contrast, the 3',5'-dioleoylthymidine derivative is nonswelling and does not exhibit lyotropic liquid-crystalline phase behavior. The nucleolipids' propensity for DNA-type binding and recognition has been evaluated by using a monolayer system to measure surface pressure-area isotherms in a Langmuir trough and indicates that the nucleoside base is available for nonspecific hydrogen bonding in the monolayer liquid expanded state for the single-chain nucleolipids but not for the dual-chain amphiphile.

Dynamic alteration of low-density lipoprotein receptor after exposure to transforming growth factor-beta2 in human Tenon's capsule fibroblasts

PURPOSE

The present study investigated dynamic alteration of low-density lipoprotein receptor and its binding and uptake of low-density lipoprotein (LDL) after exposure to transforming growth factor-beta(2) (TGF-beta(2)) in human Tenon's capsule fibroblasts.

METHODS

Tenon's capsule fibroblasts obtained from elective cataract surgery patients were cultured and stimulated with different concentrations (0.1-10 ng/mL) of TGF-beta(2) for 24, 48, and 72 h. The LDLr mRNA and protein levels were analyzed by relative quantification real-time RT-PCR and Western blot analysis, respectively. The binding and uptake of DiO (3,3'-dioctadecyloxacarbocyanine)-labeled LDL was assessed by confocal microscopy.

RESULTS

Real-time RT-PCR and Western blot analyses showed similar results revealing that after exposure to TGF-beta(2), the expression of protein and mRNA of LDLr occurred in a concentration-dependent and time-dependent manner with a peak at a concentration of 1.0 ng/mL at 72 h in Tenon's capsule fibroblasts. Confocal microscopy showed that DiO-LDL binding and uptake were time-dependent, reaching saturation at approximately 6 h.

CONCLUSIONS

This study shows that LDLrs were overexpressed in the activated Tenon's capsule fibroblasts in a concentration-dependent and time-dependent manner after exposure to TGF-beta(2). The results suggest that LDLr in the activated Tenon's capsule fibroblasts may become a novel focus as a target receptor for controlled drug delivery, particularly in anti-scarring therapy during excessive conjunctival wound healing.

Prospects and challenges of the development of lipoprotein-based formulations for anti-cancer drugs

This review evaluates drug delivery systems that involve intact plasma lipoproteins or some of their components. These complex macromolecules transport highly water-insoluble compounds (cholesteryl esters and triacylglycerols) in their natural environment - a property that renders them ideal carriers of hydrophobic drugs. Particular emphasis is placed on the application of lipoproteins as drug delivery agents in cancer chemotherapy. The history and present activity regarding lipoprotein-based formulations are reviewed, with the primary focus on the smaller sized (low and high density) lipoprotein-based formulations and their potential clinical and commercial value. The use of both native and synthetic lipoproteins as drug delivery agents are discussed from the standpoint of therapeutic efficacy, as well as commercial feasibility. The advantages of lipoprotein-based drug delivery formulations are compared with other drug delivery models, with the primary focus on liposomal preparations. Finally, an expert opinion is provided, regarding the potential use of lipoprotein-based formulations in cancer treatment, taking into consideration the major advantages (biocompatibility, safety, drug solubility) and the barriers (manufacturing protein components, financial interest, investments) to their commercial development.

Delivery systems to increase the selectivity of antibiotics in phagocytic cells

Many infectious diseases are caused by facultative organisms that are able to survive in phagocytic cells. The intracellular location of these microorganisms protects them from the host defence systems and from some antibiotics with poor penetration into phagocytic cells. One strategy used to improve the penetration of antibiotics into phagocytic cells is the use of carrier systems that deliver these drugs directly to the target cell. Delivery systems such as liposomes, micro/nanoparticles, lipid systems, conjugates, and biological carriers such as erythrocyte ghosts may contribute to increasing the therapeutic efficacy of antibiotics and antifungal agents in the treatment of infections caused by intracellular microorganisms. The main objective of this review is to analyze recent advances and current perspectives in the use of antibiotic delivery systems in the treatment of intracellular infections such as mycobacterial infections, brucellosis, salmonellosis, listeriosis, fungal infections, visceral leishmaniasis, and HIV.

Mimicking nature’s nanocarrier: synthetic low-density lipoprotein-like nanoparticles for cancer-drug delivery

Evaluation of: Nikanjam M, Blakely EA, Bjornstad KA, Shu X, Budinger TF, Forte TK: Synthetic nano-low density lipoprotein as targeted drug delivery vehicle for glioblastoma multiforme. Int. J. Pharm. 3287, 86–94 (2007) [1] . Low-density lipoproteins have long been recognized as a viable nanocarrier for targeted delivery of drug and imaging agents. Many groups have published promising initial findings; however, progress in this field has been impeded by the need to isolate low-density lipoproteins from fresh donor plasma. In a recent paper by Nikanjam and colleagues, synthetic low-density lipoprotein-like nanoparticles were prepared from commercial lipids and a bifunctional synthetic peptide containing the low-density lipoprotein receptor-binding domain and the lipid-binding motif. These particles were shown to behave similarly to native low-density lipoproteins and also to bind to the low-density lipoprotein receptor on cancer cells. Herein, we evaluate the utility of this novel delivery vehicle and discuss what role this technology may have in nanomedicine.