Nano and microtechnologies for ophthalmic administration, an overview

Abstract

Ocular drug delivery is one of the most challenging fields of pharmaceutical research. They are generally employed to overcome the static (different layers of cornea, sclera, and retina including blood aqueous and blood-retinal barriers) and dynamic barriers (choroidal and conjunctival blood flow, lymphatic clearance, and tear dilution) of the eye. Ophthalmic formulations must be sterile, and the biomaterials used in the preparation of pharmaceutical systems completely compatible and extremely well tolerated by ocular tissues. The location of the target tissue in the eye will determine the route of administration. Ophthalmic administration systems are intended for topical, intraocular and periocular administration. In this review we describe the main pharmaceutical nano-and microsystems currently under study to administrate drugs in the eye, covering microparticles, nanoparticles, liposomes, microemulsions, niosomes and dendrimers. We have performed the corresponding revision of the published scientific literature always emphasizing the technological aspects. The review discusses also the biomaterials used in the preparation of the nano and microsystems of ophthalmic drug delivery, fabrication techniques, therapeutic significances, and future possibilities in the field.

Imprinted Contact Lenses for Sustained Release of Polymyxin B and Related Antimicrobial Peptides

“…In situ forming gels, suspensions, muco-adhesive polymers, nanoparticles, and implants have been shown to enhance, to a certain extent, ocular drug bioavailability, as long as they can prolong drug residence on the ocular surface or promote its penetration. [2][3][4] Nevertheless, discomfort symptoms caused by the formulation itself, such as sticking and blurring effects, do not facilitate patient compliance. Using soft contact lenses as drug delivery platforms can minimize these drawbacks, whereas significantly increase ocular bioavailability by entrapping the drug in the lachrymal fluid between the lens and the cornea.…”

Gelatin Nanoparticles-HPMC Hybrid System for Effective Ocular Topical Administration of Antihypertensive Agents

“…Although, an important number of different nanodevices composed by diverse materials are being evaluated for topical ocular drug delivery purposes in the past decades, not all of them have been properly tested in terms of ocular tolerance, which is an imperative previous step in order to guarantee good in vivo tolerance of the proposed systems [22]. That is why, in this work, we have in vitro corroborated the selection of nanoparticle concentrations with optimal ocular tolerance.…”

“…Several novel drug delivery systems have been developed like nanoparticles, microparticles, microemulsions, hydrogels or contact lenses among others, to achieve more effective therapies [17][18][19][20][21]. However, it is mandatory to keep always in mind that all excipients used must be highly compatible with ocular tissues [22]. Most efforts that have been made focused on increasing the retention time of formulations, and the contained drug, on the ocular surface as an initial step for the passive transport of the active compounds through the cornea [8,20,23].…”

“…As mentioned before, another interesting approach to increase the drug retention time on the ocular surface and, hence, its ocular bioavailability, is the use of nanoparticles [22,34,35]. Due to their nanometric range and large surface area, they seem to have an enhanced capacity to be entrapped over the precorneal film and even to permeate the ocular surface epithelium [36].…”

Development and Characterization of Potential Ocular Mucoadhesive Nano Lipid Carriers Using Full Factorial Design

“…Mucoadhesives contribute to the formation of a viscous, continuous layer on the surface of the eye that partially protects the drug from elimination by tearing, prolonging the retention time on the eye surface. Different polymers such as carboxymethylcellulose, hydroxypropyl methylcellulose (HPMC), hyaluronic acid or xanthan gum have been used for this purpose in ophthalmic drug deliveries [3][4][5] due to their good tolerance on the eye both in vitro and in vivo [6].…”