Nanotherapy Offers Innovative Approaches to Diabetic Retinopathy

Diabetes mellitus (DM) is a metabolic disorder characterized by hyperglycemia. Prolonged hyperglycemia can lead to various chronic complications, including nephropathy, cardiomyopathy, neuropathy, and retinopathy. The International Diabetes Federation predicted that the number of individuals with DM was 463 million in 2019, and they anticipate this number to rise to 700 million by 2045.¹ Diabetic retinopathy (DR), the most common and distinct complication of DM, is one of the primary causes of preventable blindness in working-age adults.^2-6

The pathways contributing to the pathogenesis of DR include increased oxidative stress, resulting in elevated vascular endothelial growth factor (VEGF) secretion leading to angiogenesis and vascular permeability; increased oxidative stress leading to leukostasis and subsequent vascular occlusion; and increased glutamate levels leading to neurodegeneration.⁷

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Currently, the most successful approach for treating DR involves managing blood glucose levels. Advanced cases of this condition may require treatments like laser therapy, anti-VEGF therapy, steroids, or vitrectomy. Laser photocoagulation is used to enhance retinal circulation in patients with microcirculation alterations of the ocular fundus. For individuals with macular edema, anti-VEGF drugs are typically administered to alleviate macular edema and improve vision. In the most severe cases, such as fundus hemorrhage or proliferative vitreoretinopathy, vitrectomy is performed.⁸

Despite these treatments, many DR patients still experience vision loss and potential side effects. Considering the limited effectiveness of conventional drugs due to low bioavailability and potential side effects, and the inherent risks of major surgery, nanotechnology has been increasingly integrated into the field of medicine, offering innovative approaches to DR treatment.⁸

Nanotechnology involves the applications and characteristics of materials with dimensions ranging from 0.1 to 100 nm. As nanotechnology has rapidly advanced, it has found extensive applications in medicine and various other disciplines and fields.^9,10 Due to its small molecular size and multiple functions, nanotechnology has also been integrated into modern drug research, providing solutions to the challenges experienced in conventional treatments.^11,12 Nanodrugs can be specifically designed to transport medications, with reduced or even eliminated side effects. Additionally, they can achieve sustained release, prolonging the action time of drugs, enhancing the stability of drugs, simplifying drug storage, and establishing new drug delivery routes.

The use of nanoparticles is a novel therapeutic strategy for DR, and various nanoparticles have been studied. Loading drugs into nanoparticles could overcome some limitations, including enzymatic and chemical degradation, reduced half-life, low solubility in solvents, high doses required to exhibit therapeutic effects, and high toxicity. The main advantages of nanotechnology include small diameter, high penetrability through the blood-retina barrier, good biocompatibility, and reduced drug degradation in the body to achieve sustained release.² The most commonly used nanoparticles to target the posterior segment of the eye include nanostructured lipid carriers, polymeric nanoparticles, solid lipid nanoparticles, cationic nanoemulsions, dendrimers, liposomes, and gold nanoparticles.¹³

Widely studied medications for diabetic retinopathy that can be delivered as nanoparticles include corticosteroids and antiangiogenic factors. Corticosteroids such as triamcinolone acetonide, dexamethasone, and fluocinolone acetonide reduce vascular permeability, prevent the breakdown of the blood-retinal barrier, down-regulate VEGF expression and/or production, and inhibit matrix metalloproteinases.^14,15 Recombinant humanized antibodies showing activity against all isoforms of VEGF-A, such as bevacizumab, ranibizumab, and pegaptanib, have demonstrated efficacy in the treatment of diabetic retinopathy, diabetic macular edema, and iris neovascularization.¹⁶

Preclinical studies and clinical trials have shown that both corticosteroidsand VEGF inhibitors can be delivered as nanoparticles, and they appear to be a promising alternative to conventional systems, which are generally associated with very low bioavailability (5% to 10%) of the administered drugs.^17-29

References

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