Drug targeting to choroidal neovascularization

Red Light-Triggered Anti-Angiogenic and Photodynamic Combination Therapy of Age-Related Macular Degeneration

Choroidal neovascularization (CNV) is the key pathological event of wet age-related macular degeneration (wAMD) leading to irreversible vision loss. Currently, anti-angiogenic therapy with anti-vascular endothelial growth factor (VEGF) agents has become the standard treatment for wAMD, while it is still subject to several limitations, including the safety concerns of monthly intravitreal administration and insufficient efficacy for neovascular occlusion. Combined therapy with photodynamic therapy (PDT) and anti-angiogenic agents has emerged as a novel treatment paradigm. Herein, a novel and less-invasive approach is reported to achieve anti-angiogenic and photodynamic combination therapy of wAMD by intravenous administration of a photoactivatable nanosystem (Di-DAS-VER NPs). The nanosystem is self-assembled by reactive oxygen species (ROS)-sensitive dasatinib (DAS) prodrug and photosensitizer verteporfin (VER). After red-light irradiation to the diseased eyes, intraocular release of anti-angiogenic DAS is observed, together with selective neo-vessels occlusion by VER-generated ROS. Notably, Di-DAS-VER NPs demonstrates promising therapeutic efficacy against CNV with minimized systemic toxicity. The study enables an efficient intravenous wAMD therapy by integrating a photoactivation process with combinational therapeutics into one simple nanosystem.

Targeted Noninvasive Treatment of Choroidal Neovascularization by Hybrid Cell-Membrane-Cloaked Biomimetic Nanoparticles

Choroidal neovascularization (CNV) is the leading cause of vision loss in many blinding diseases, but current antiangiogenic therapies with invasively intravitreal injection suffer from poor patient compliance and a rate of devastating ocular complications. Here, we develop an alternative antiangiogenic agent based on hybrid cell-membrane-cloaked nanoparticles for noninvasively targeted treatment of CNV. The retinal endotheliocyte membrane coating provides as-fabricated nanoagents with homotypic targeting capability and binding ability to the vascular endothelial growth factor. The fusion of red blood cell membranes protects the hybrid membrane-coated nanoparticles from phagocytosis by macrophages. In a laser-induced wet age-related macular degeneration mouse model, a significantly enhanced accumulation is observed in CNV regions after intravenous delivery of the hybrid membrane-coated nanoparticles. Moreover, an excellent therapeutic efficacy is achieved in reducing the leakage and area of CNV. Overall, the biomimetic antiangiogenic nanoagents provide an effective approach for noninvasive treatment of CNV.

Intravenous treatment of choroidal neovascularization by photo-targeted nanoparticles

Choroidal neovascularization (CNV) is the major cause of vision loss in wet age-related macular degeneration (AMD). Current therapies require repeated intravitreal injections, which are painful and can cause infection, bleeding, and retinal detachment. Here we develop nanoparticles (NP-[CPP]) that can be administered intravenously and allow local drug delivery to the diseased choroid via light-triggered targeting. NP-[CPP] is formed by PEG-PLA chains modified with a cell penetrating peptide (CPP). Attachment of a DEACM photocleavable group to the CPP inhibits cellular uptake of NP-[CPP]. Irradiation with blue light cleaves DEACM from the CPP, allowing the CPP to migrate from the NP core to the surface, rendering it active. In mice with laser-induced CNV, intravenous injection of NP-[CPP] coupled to irradiation of the eye allows NP accumulation in the neovascular lesions. When loaded with doxorubicin, irradiated NP-[CPP] significantly reduces neovascular lesion size. We propose a strategy for non-invasive treatment of CNV and enhanced drug accumulation specifically in diseased areas of the eye.

Current treatments of wet age-related macular degeneration require repeated injections of active drugs into the vitreous. Here Wang et al. develop nanoparticles that when injected intravenously can be targeted to the eye by irradiation with blue light, allowing local and enhanced drug release in the back of the eye, and providing an alternative to current delivery strategies.

In vivo photothermal optical coherence tomography of endogenous and exogenous contrast agents in the eye

Optical coherence tomography (OCT) has become a standard-of-care in retinal imaging. OCT allows non-invasive imaging of the tissue structure but lacks specificity to contrast agents that could be used for in vivo molecular imaging. Photothermal OCT (PT-OCT) is a functional OCT-based technique that has been developed to detect absorbers in a sample. We demonstrate in vivo PT-OCT in the eye for the first time on both endogenous (melanin) and exogenous (gold nanorods) absorbers. Pigmented mice and albino mice (n = 6 eyes) were used to isolate the photothermal signal from the melanin in the retina. Pigmented mice with laser-induced choroidal neovascularization lesions (n = 7 eyes) were also imaged after a systemic injection of gold nanorods to observe their passive accumulation in the retina. This experiment demonstrates the feasibility of PT-OCT to image the distribution of both endogenous and exogenous absorbers in the mouse retina.

Topical ocular delivery to laser-induced choroidal neovascularization by dual internalizing RGD and TAT peptide-modified nanoparticles

A nanoparticle (NP) was developed to target choroidal neovascularization (CNV) via topical ocular administration. The NPs were prepared through conjugation of internalizing arginine-glycine-aspartic acid RGD (iRGD; Ac-CCRGDKGPDC) and transactivated transcription (TAT) (RKKRRQRRRC) peptide to polymerized ethylene glycol and lactic-co-glycolic acid. The iRGD sequence can specifically bind with integrin α_vβ₃, while TAT facilitates penetration through the ocular barrier. ¹H nuclear magnetic resonance and high-performance liquid chromatography demonstrated that up to 80% of iRGD and TAT were conjugated to poly(ethylene glycol)– poly(lactic-co-glycolic acid). The resulting particle size was 67.0±1.7 nm, and the zeta potential of the particles was −6.63±0.43 mV. The corneal permeation of iRGD and TAT NPs increased by 5.50- and 4.56-fold compared to that of bare and iRGD-modified NPs, respectively. Cellular uptake showed that the red fluorescence intensity of iRGD and TAT NPs was highest among primary NPs and iRGD- or TAT-modified NPs. CNV was fully formed 14 days after photocoagulation in Brown Norway (BN) rats as shown by optical coherence tomography and fundus fluorescein angiography analyses. Choroidal flat mounts in BN rats showed that the red fluorescence intensity of NPs followed the order of iRGD and TAT NPs > TAT-modified NPs > iRGD-modified NPs > primary NPs. iRGD and TAT dual-modified NPs thus displayed significant targeting and penetration ability both in vitro and in vivo, indicating that it is a promising drug delivery system for managing CNV via topical ocular administration.

Phospholipid-based self-assembled mesophase systems for light-activated drug delivery

Biocompatible phospholipid–cholesterol matrix undergoes photothermal transition on irradiation with near infrared light for drug release applications.

Peptides in cancer nanomedicine: drug carriers, targeting ligands and protease substrates

Peptides are attracting increasing attention as therapeutic agents, as the technologies for peptide development and manufacture continue to mature. Concurrently, with booming research in nanotechnology for biomedical applications, peptides have been studied as an important class of components in nanomedicine, and they have been used either alone or in combination with nanomaterials of every reported composition. Peptides possess many advantages, such as smallness, ease of synthesis and modification, and good biocompatibility. Their functions in cancer nanomedicine, discussed in this review, include serving as drug carriers, as targeting ligands, and as protease-responsive substrates for drug delivery.

Hybrid nanocrystals: University of Kentucky US20060280680A1

This patent application claims an interesting and novel combination of passive accumulation of drug nanocrystals within diseased tissue, in combination with active uptake of the nanocrystals by diseased cells. The patent application further claims the hybrid nanocrystals combining imaging or stabilizing molecules as inclusions in the crystal matrix. There is a focus on cancer chemotherapy and imaging, but the initial claims are not disease specific. In this patent evaluation, the novelty and utility of this application is examined, while the state of the art in nanocrystal formulations and formulation is discussed.

[Use of nanoparticles in ophthalomology]

Nanotechnology, the manufacture and use of structures and implements of around a few 100 nm in size, is becoming a key technology of the twenty-first century. An important element for the manufacture of nanoparticles is gold. Gold nanoparticles can be custom made and chemically modified in their size and form. Initial investigations have shown that they are physiologically non-hazardous. A potential application is in neovascular age-related macular degeneration. Gold nanoparticles of suitable dimensions introduced into newly forming blood vessels can be targeted and heated which selectively destroys these blood vessels. This principle has already been demonstrated in cultivated endothelial cells.

Suprachoroidal drug delivery to the back of the eye using hollow microneedles

PURPOSE

In this work, we tested the hypothesis that microneedles provide a minimally invasive method to inject particles into the suprachoroidal space for drug delivery to the back of the eye.

METHODS

A single, hollow microneedle was inserted into the sclera, and infused nanoparticle and microparticle suspensions into the suprachoroidal space. Experiments were performed on whole rabbit, pig, and human eyes ex vivo. Particle delivery was imaged using brightfield and fluorescence microscopy as well as microcomputed tomography.

RESULTS

Microneedles were shown to deliver sulforhodamine B as well as nanoparticle and microparticle suspensions into the suprachoroidal space of rabbit, pig, and human eyes. Volumes up to 35 μL were administered consistently. Optimization of the delivery device parameters showed that microneedle length, pressure, and particle size played an important role in determining successful delivery into the suprachoroidal space. Needle lengths of 800-1,000 μm and applied pressures of 250-300 kPa provided most reliable delivery.

CONCLUSIONS

Microneedles were shown for the first time to deliver nanoparticle and microparticle suspensions into the suprachoroidal space of rabbit, pig and human eyes. This shows that microneedles may provide a minimally invasive method for controlled drug delivery to the back of the eye.

Prospects for nanomedicine in treating age-related macular degeneration

Polyion complex (PIC) micelles have a size range of tens of nanometers formed through electrostatic interaction. In experimental choroidal neovascularization (CNV) in rats, the PIC micelle accumulates to the CNV lesions and is retained. PIC micelles can be used for effective drug delivery to CNV. A novel dendritic photosensitizer encapsulated by a polymeric-micelle formulation was employed for an effective photodynamic therapy for age-related macular degeneration. With its highly selective accumulation on experimental CNV lesions, this treatment resulted in a remarkably efficacious CNV occlusion with minimal unfavorable phototoxicity. Gene therapy is a promising approach to treat age-related macular degeneration. A ternary complex, composed of a core containing DNA packaged with cationic peptides and enveloped in the anionic dendrimer phthalocyanine, has been developed, which provides the photosensitizing action. Subconjunctival injection of the ternary complex followed by laser irradiation resulted in transgene expression only in the laser-irradiated site in rats.

Effective accumulation of polyion complex micelle to experimental choroidal neovascularization in rats

Exudative age-related macular degeneration, characterized by choroidal neovascularization (CNV), is a major cause of visual loss. In this study, we examined the distribution of the polyion complex (PIC) micelle encapsulating FITC-P(Lys) in blood and in experimental CNV in rats to investigate whether PIC micelle can be used for treatment of CNV. We demonstrate that PIC micelle has long-circulating characteristics, accumulating to the CNV lesions and is retained in the lesion for as long as 168 h after intravenous administration. These results raise the possibility that PIC micelles can be used for achieving effective drug targeting to CNV.