Abstract
The present work was aimed for the preparation of a stable nanostructured lipid carrier (NLC) system for the delivery of N-palmitoylethanolamide (PEA) to the back of the eye. PEA is an interesting natural compound showing anti-inflammatory and neuroprotective activities. The limits of PEA (poor solubility and high instability) justify its nanoencapsulation into drug delivery systems. Two different well-known techniques were compared to formulate NLC: the high shear homogenization technique (HSH) and the method based on a combination of HSH technique and ultrasonication (HSH/US). Nanoparticles were evaluated in relation to mean size, homogeneity, surface charge, and physical stability by Turbiscan technology. Retinal distribution of PEA was carried out in a rat eye after single instillation of PEA-NLC ophthalmic formulation. The novel formulation delivered remarkable levels of PEA to the retina. Lastly, topical administration of PEA-NLC ophthalmic formulation was able to significantly inhibits retinal tumor necrosis factor-α (TNF-α) levels in streptozotocin-induced diabetic rats. The present findings suggest that the novel ophthalmic formulation may be useful for the treatment of retinal diseases such as diabetic retinopathy. Clinical studies are in progress to evaluate this possibility.
Highlights
Diabetic retinopathy (DR) is likely the most frequent cause of loss of sight and visual impairment and it is strongly influenced by many factors such as diabetes duration, poor glycemic control, and hypertension [1]
We evaluated two well-known techniques used to formulate lipid nanoparticles such as the high shear homogenization technique (HSH) and the method based on a combination of the HSH technique and ultrasonication (HSH/US) [17,21]
NLC1 formulated following a method based on a combination of the HSH technique and ultrasonication (HSH/US) provided better results in terms of mean particle size (Z-Ave), population homogeneity (PDI), and zeta potential (ZP) with respect to NLC2 formulated by a high shear homogenization technique (HSH)
Summary
Diabetic retinopathy (DR) is likely the most frequent cause of loss of sight and visual impairment and it is strongly influenced by many factors such as diabetes duration, poor glycemic control, and hypertension [1]. In diabetes, sustained hyperglycemia works as a trigger for a variety of events leading in vascular dysfunction. Vascular alterations in DR are related to several biochemical and immunological mechanisms that promote pro-inflammatory cytokines release such as TNF-α. Several studies showed increased levels of retinal TNF-α in diabetic patients and animals as well [2,3,4,5,6,7]. Activation of NF-kB leads to the modulation of many cytokines such as TNF-α [8]. Several works outlined an anti-inflammatory and neuroprotective action of PEA that can be useful in the treatment of different pathological conditions such as retinal diseases [9,10,11]. Several studies demonstrated the beneficial role of PEA in retinal diseases such as DR, which preserves the integrity of the blood–retinal barrier [9,14,15]
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