Synthesis and Ex Vivo Trans-Corneal Permeation of Penetratin Analogues as Ophthalmic Carriers: Preliminary Results.

Silvia Pescina,Carmine Ostacolo,Patrizia Santi,Cristina Padula,Marina Sala,Pietro Campiglia,Sara Nicoli,Maria Carmina Scala

doi:10.3390/pharmaceutics12080728

Silvia Pescina, Carmine Ostacolo + Show 6 more

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https://doi.org/10.3390/pharmaceutics12080728

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Abstract

Among enhancing strategies proposed in ocular drug delivery, a rising interest is directed to cell penetrating peptides (CPPs), amino acid short sequences primarily known for their intrinsic ability to cell internalization and, by extension, to cross biological barriers. In fact, CPPs may be considered as carrier for delivering therapeutic agents across biological membranes, including ocular tissues. Several CPPs have been proposed in ophthalmic delivery, and, among them, penetratin (PNT), a 16-amino acids natural peptide, stands out. Therefore, we describe the synthesis via the mimotopic approach of short fluorescently labeled analogues of both PNT and its reversed sequence PNT-R. Their ability to cross ocular membranes was checked ex vivo using freshly explanted porcine cornea. Furthermore, some sequences were studied by circular dichroism. Despite the hydrophilic nature and the relatively high molecular weight (approx. 1.6 kDa), all analogues showed a not negligible trans-corneal diffusion, indicating a partial preservation of penetration activity, even if no sequences reached the noteworthy ability of PNT. It was not possible to find a correlation between structure and corneal penetration ability, and further studies, exploring peptides distribution within corneal layers, for example using imaging techniques, deserve to be performed to figure out a possible difference in intracellular delivery.

Highlights

Ophthalmic administration, despite the large availability of many effective drugs, is still challenging for both the anterior and the posterior segments of the eye, due to several types of barriers, exerting static, dynamic and metabolic resistance [1]
Among enhancing strategies proposed in ocular drug delivery, a rising interest is directed to cell penetrating peptides (CPPs), amino acid short sequences primarily known for their intrinsic ability to cell internalization and, by extension, to cross biological barriers
Several CPPs have been proposed in ophthalmic delivery, and, among them, penetratin (PNT), a 16-amino acids natural peptide, stands out

Summary

Introduction

Ophthalmic administration, despite the large availability of many effective drugs, is still challenging for both the anterior and the posterior segments of the eye, due to several types of barriers, exerting static, dynamic and metabolic resistance [1]. Anterior segment of the eye might benefit from CPPs application for a more effective treatment of diseases affecting cornea, and the anterior chamber and the lens To explore this perspective, following the mimotopic approach, we previously designed and prepared short PEP-1 derived CPPs. The mimotopic approach allowed us to obtain shortened PEP-1 sequences, more affordable and with a comparable penetration capacity. The synthesized peptides and PEP-1 itself showed a preferential paracellular penetration route in comparison with the intracellular penetration route of PNT [6] According to these evidences, the aim of the present paper is the design and synthesis of new PNT analogues by the mimotopic approach and the study of their capability to cross porcine cornea ex vivo

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