Potential of Lipoprotein-Based Nanoparticulate Formulations for the Treatment of Eye Diseases

Lipoproteins are naturally occurring nanoparticles and their main physiological function is the promotion of lipid metabolism. They can be prepared in vitro for use as drug carriers, and these reconstituted lipoproteins show similar biological activity to their natural counterparts. Some lipoproteins can cross the blood-retinal barrier and are involved in intraocular lipid metabolism. Drug-loaded lipoproteins can be delivered to the retina for the treatment of posterior eye diseases. In this review, we have discussed the therapeutic applications of lipoproteins for eye diseases and introduced the emerging animal models used for the evaluation of their therapeutic effects.

Polymer-coated pH-responsive high-density lipoproteins

Intracellular drug delivery by nanoparticles is often hampered by their endosomal entrapment followed by their degradation in the lysosomal compartment and/or exocytosis. Here, we show that internalization and endosomal escape of cargoes in a cationized natural nanocarrier, high-density lipoprotein (HDL), can be controlled in a pH-dependent manner through stable complexation with a membranolytic anionic block polymer. A genetically and chemically cationized form of HDL (catHDL) is prepared for the first time by both genetic fusion with YGRKKRRQRRR peptide and incorporation of 1,2-dioleoyloxy-3-(trimethylammonium)propane. Upon addition of poly(ethylene glycol)-block-poly(propyl methacrylate-co-methacrylic acid) (PA), catHDL yields inhibition of internalization at neutral pH and its subsequent recovery at mildly acidic pH. catHDL forms a stable discoidal-shape complex with PA (catHDL/PA) (ca. 50 nm in diameter), even in the presence of serum. Significant enhancement of endosomal escape of a catHDL component is observed after a 1-h treatment of human cancer cells with catHDL/PA. Doxorubicin and curcumin, fluorescent anti-cancer drugs, encapsulated into catHDL/PA are also translocated outside of endosomes, compared with that into catHDL, and their cytotoxicities are enhanced inside the cells. These data suggest that catHDL/PA may have a potential benefit to improve the cellular delivery and endosomal escape of therapeutics under mildly acidic conditions such as in tumor tissues.

Near-infrared-triggered in situ hybrid hydrogel system for synergistic cancer therapy

The photo-polymerization of PEGDA hydrogel and its synergetic anti-tumor effect triggered by a single NIR laser.

Mesoscopic metal nanoparticles doubly functionalized with natural and engineered lipidic dispersants for therapeutics

Surface engineering of mesoscopic metal nanoparticles to increase biocompatibility and cell interaction is important for improvement of their therapeutic properties. Here, we describe a strategy to stabilize mesoscopic metal nanoparticles and to enhance their cell interaction by stepwise addition of (Z)-9-octadecenoate (oleate) and a cell-penetrating peptide-fused high-density lipoprotein (cpHDL). Oleate replaces a cytotoxic dispersant on the surface of gold nanorods (AuNRs), which enables subsequent cpHDL binding without causing aggregation. Notably, these two lipidic dispersants are probably intercalated on the surface. This procedure was also used to stabilize 20 nm spherical gold nanoparticles and 40 nm aggregates of 10 nm magnetite nanoparticles. cpHDL-bound AuNRs were internalized greater than 80 times more efficiently than poly(ethylene glycol)-conjugated AuNRs and were able to elicit cancer cell photoablation.

Novel biodegradable heparin-coated nanocomposite system for targeted drug delivery

HP–SPIO NPs (42 nm) were formulated by co-precipitation. Doxorubicin and paclitaxel were loaded into the SPIO NP core. HP–SPIO NPs had sustained release of DOX (87%) and PTX (75%) at pH 6.0. Drug loaded HP–SPIO NPs caused 95 and 84%, and 85 and 77% apoptosis in A2780 and OVCAR-3 cells, respectively. DOX–HP–SPIO NPs and PTX–HP–SPIO NPs caused a sharp decrease in bcl-2 and survivin proteins.

Exclusive photothermal heat generation by a gadolinium bis(naphthalocyanine) complex and inclusion into modified high-density lipoprotein nanocarriers for therapeutic applications

A hydrophobic gadolinium bis(naphthalocyanine) sandwich complex (GdSand) possessing several absorbances across visible and infrared wavelengths (up to 2500 nm) was solubilized in aqueous solution by uptake into a nascent mutant high-density lipoprotein (HDL) nanocarrier. The HDL nanocarrier was additionally functionalized with a trans-activator of transcription peptide sequence to promote efficient cell penetration of the drug delivery system (cpHDL). The dye-loaded nanocarrier (GdSand@cpHDL) exhibited photothermal heat generation properties upon irradiation with near-infrared (NIR) laser light, with controllable heat generation abilities as a function of the incident laser light power. Comparison of the photothermal behavior of the dyes GdSand and the well-explored molecular photothermal agent indocyanine green (ICG) in the cpHDL nanocarrier (i.e., ICG@cpHDL) revealed two significant advantages of GdSand@cpHDL: (1) the ability to maintain elevated temperatures upon light absorption for extended periods of time, with a reduced degree of self-destruction of the dye, and (2) exclusive photothermal heat generation with no detectable singlet oxygen production leading to improved integrity of the cpHDL nanocarrier after irradiation. Finally, GdSand@cpHDL was successfully subjected to an in vitro study against NCI-H460 human lung cancer cells, demonstrating the proof-of-principle utility of lanthanide sandwich complexes in photothermal therapeutic applications.

Delivery of hydrophilic drug doxorubicin hydrochloride-targeted liver using apoAI as carrier

High-density lipoprotein (HDL) particles can deliver cholesterol from peripheral tissues to the liver through apolipoprotein A1 (Apo A1), which specifically binds to the scavenger receptor class B type 1 (SR-B1) receptor on the surface of hepatocytes. Therefore, ApoA1 can be potentially used to target drugs to the liver. In this study, we successfully loaded doxorubicin hydrochloride (Dox or Dox-HCl), which is a hydrophilic drug used in a wide variety of clinical applications, into the core of reconstituted HDL (rHDL prepared by apoAI and egg phospholipids) to form a doxorubicin-HDL complex (rHDL-Dox). The MTT assays showed that rHDL-Dox particles also had higher cytotoxicity against several cells lines compared to free drug or Dox encapsulated into liposomes. A cellular uptake assay demonstrated that rHDL-Dox had higher absorption in SR-BI receptor positive liver cells. Importantly, in vivo experiments showed that rHDL-Dox can reduce tumor growth more effectively than liposomes. In addition, an in vitro hemolysis assay showed that rHDL-Dox caused only limited hemolysis in the case of high doses. Taken together, our findings indicate that rHDL is a safe and effective drug delivery system for targeting liver.

Co-encapsulation of magnetic Fe3O4 nanoparticles and doxorubicin into biodegradable PLGA nanocarriers for intratumoral drug delivery

In this study, the authors constructed a novel PLGA [poly(D,L-lactic-co-glycolic acid)]-based polymeric nanocarrier co-encapsulated with doxorubicin (DOX) and magnetic Fe₃O₄ nanoparticles (MNPs) using a single emulsion evaporation method. The DOX-MNPs showed high entrapment efficiency, and they supported a sustained and steady release of DOX. Moreover, the drug release was pH sensitive, with a faster release rate in an acidic environment than in a neutral environment. In vitro, the DOX-MNPs were easily internalized into murine Lewis lung carcinoma cells and they induced apoptosis. In vivo, the DOX-MNPs showed higher antitumor activity than free DOX solution. Furthermore, the antitumor activity of the DOX-MNPs was higher with than without an external magnetic field; they were also associated with smaller tumor volume and a lower metastases incidence rate. This work may provide a new modality for developing an effective drug delivery system.

Intracellular drug delivery by genetically engineered high-density lipoprotein nanoparticles

Aim: Nascent high-density lipoprotein (HDL) capable of intracellularly delivering anticancer drugs was developed to potentiate antitumor activities. Materials & methods: Apolipoprotein A-I, a major component protein of HDL, was genetically fused to TAT peptide, a protein transduction domain. Nascent HDL was prepared with this mutant and phospholipids. Results & discussion: Intracellular delivery of doxorubicin (DXR) by TAT-fused HDL was confirmed by confocal microscopy. Treatment of cancer cells with TAT-fused HDL–DXR complex resulted in enhanced growth inhibition. Furthermore, TAT-fused HDL–DXR complex suppressed tumor growth in mice more efficiently than HDL–DXR complex. No bodyweight loss was observed for the TAT complex. These results clearly demonstrate the usefulness of TAT fusion to nascent HDL to potentiate the antitumor activity of DXR. Conclusion: The genetic fusion of apoA-I with biologically active peptides potentially enables a simple assembly of biocompatible and versatile drug carriers.