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ABSTRACT
Introduction: The development of ophthalmic formulations able to deliver hydrophilic and hydrophobic drugs to the inner structures of the eye and restore the preocular tear film has been a leading topic of discussion over the last few years. In this sense, liposomes represent a suitable strategy to achieve these objectives in ocular drug delivery.
Areas covered: Knowledge of the different physiological and anatomical eye structures, and specially the ocular surface are critical to better understanding and comprehending the characteristics required for the development of topical ophthalmic liposomal formulations. In this review, several features of liposomes are discussed such as the main materials used for their fabrication, basic structure and preparation methods, from already established to novel techniques, allowing the control and design of special characteristics. Besides, physicochemical properties, purification processes and strategies to overcome delivery or encapsulation challenges are also presented.
Expert opinion: Regarding ocular drug delivery of liposomes, there are some features that can be redesigned. Specific biocompatible and biodegradable materials presenting therapeutic properties, such as lipidic compounds or polymers significantly change the way of tackling ophthalmic diseases. Besides, liposomes entail an effective, safe and versatile strategy for the treatment of diseases in the clinical practice.
Acknowledgments
All the figures were created with BioRender (www.biorender.com). M.G.C. thanks for a PhD fellowship from the Spanish MECD (FPU18/03445).
Disclosure
Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.
Declaration of interest
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
Article highlights
The precorneal tear film preserves ocular surface integrity, cornea and conjunctiva.
Corneal low permeability entails a challenge to deliver active substances that target both the anterior and posterior segment of the eye.
Liposomes are biocompatible and biodegradable lipid-made spherical vesicles that resemble cell membranes able to permeate and deliver both hydrophilic and hydrophobic drugs.
The use of liposomes with similar components to those present in the precorneal tear film entails a novel strategy in the treatment of dry eye disease.
Methods based on ethanol injection and microfluidics resulted the best options for liposome scaling-up due to their feasibility, robustness and optimization potential.
Technological strategies such as the incorporation of bioadhesive biocompatible polymers or positively charged phospholipids help increase mucoadhesion, retention time and permeation of liposomes in the cornea.
One of the major issues that limits the use of liposomal formulations is the sterilization. A combination of sterilizing filtration and cold methods seems to be the most suitable alternative to industrial fabrication of liposomes.
A simultaneous administration of topical ophthalmic liposomal formulations with supplements, such as vitamins or fatty acids, represent an important strategy for the recovery of the tear film lipid layer in ocular surface pathologies such as the dry eye syndrome.
Development of technological strategies that increase the stability of liposomal dispersion is required.
The attachment of highly specific biomolecules to the liposomal surface and using intrinsic therapeutic materials might entail the next generation of nano-liposome formulations.
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