**8. Conclusion**

Although there has been great interest in the development of new topical ocular delivery systems, the topical administration of drugs is not as effective as intravitreal delivery in treating retinal diseases. During topical delivery, drug molecules must cross several anatomic and physiologic barriers before reaching the posterior segment of the eye. Consequently, very low concentrations, with almost no clinical effect, are usually obtained. However, dramatic changes have been observed in the field of ocular drug delivery over the last decade, and nanomedicine is one of the most promising technologies for efficient drug delivery into intraocular tissues. Nanocarriers have a great potential to solve the challenge of releasing drugs into the posterior segment of the eyeball and reaching deeper intraocular tissues. Different nanocarriers, such as NPs, LPs, micelles, dendrimers, cyclodextrin nanoparticles, and liposomes, have been developed for the safe and effective drug delivery to the vitreous and the retina. Nevertheless, only a few of these particles have clinically been approved (liposomes and CDs among them).

Liposomes have lately been of great interest as carriers for advanced drug delivery in medicine and, especially, in ophthalmology due to their potential to avoid sophisticated ocular barriers when they are topically used. Liposomal drug delivery systems have a bright future in ophthalmology and, particularly, for the retina for several reasons. First, features such as the passive-targeting effect may substantially

**47**

**Author details**

intraocular illnesses.

Zapopan, Jalisco, México

Zapopan, Jalisco, México

*Breaking down the Barrier: Topical Liposomes as Nanocarriers for Drug Delivery…*

enhance the amount of drug in target tissues. Second, liposomal technology allows the therapeutic index of already established drugs, with well-established therapeutic profiles, to be improved. This eliminates some of the considerable risks associated with the development of new pharmaceutical products. Third, many of the potential new pharmaceutical products arising from advances in biotechnology would come from macromolecules such as proteins, peptides, oligonucleotides, and plasmids, which could easily be carried by liposomes so as to access target tissues and cells. Additionally, liposomes possess features of optimal drug delivery systems to get to the ocular surface and intraocular tissues, for instance, sustained and controlled drug delivery, ease to instill for the patient, good corneal-scleral penetration, and the fact that they reach appropriate concentrations of the drug in the target tissue, avoid side effects produced by conventional systems (like IVT injections), there is better patient compliance, and they are potentially affordable for patients. A proof of the clinical advantages of liposomes is represented by recent trials where

TA-loaded liposomes have successfully been used to treat macular edema.

Considering that liposomes collect the main characteristics of an optimal drug delivery system and that these nanocarriers have proven their capacity not only to deliver drugs but also genetic materials to the posterior segment of the eye, we consider that liposomes are promising nanoparticles for the therapy of multiple

Arturo Santos1,2\*, Juan C. Altamirano-Vallejo1,2, José Navarro-Partida1,2,

1 Tecnológico de Monterrey, Escuela de Medicina y Ciencias de la Salud,

3 OPKO Health Inc., Miami, Florida, United States of America

\*Address all correspondence to: asantos@e-retina.com

provided the original work is properly cited.

2 Centro de Retina Médica y Quirúrgica S.C., Centro Médico Puerta de Hierro,

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Alejandro González-De la Rosa1,2 and Jane H. Hsiao3

*DOI: http://dx.doi.org/10.5772/intechopen.86601*

*Breaking down the Barrier: Topical Liposomes as Nanocarriers for Drug Delivery… DOI: http://dx.doi.org/10.5772/intechopen.86601*

enhance the amount of drug in target tissues. Second, liposomal technology allows the therapeutic index of already established drugs, with well-established therapeutic profiles, to be improved. This eliminates some of the considerable risks associated with the development of new pharmaceutical products. Third, many of the potential new pharmaceutical products arising from advances in biotechnology would come from macromolecules such as proteins, peptides, oligonucleotides, and plasmids, which could easily be carried by liposomes so as to access target tissues and cells. Additionally, liposomes possess features of optimal drug delivery systems to get to the ocular surface and intraocular tissues, for instance, sustained and controlled drug delivery, ease to instill for the patient, good corneal-scleral penetration, and the fact that they reach appropriate concentrations of the drug in the target tissue, avoid side effects produced by conventional systems (like IVT injections), there is better patient compliance, and they are potentially affordable for patients. A proof of the clinical advantages of liposomes is represented by recent trials where TA-loaded liposomes have successfully been used to treat macular edema.

Considering that liposomes collect the main characteristics of an optimal drug delivery system and that these nanocarriers have proven their capacity not only to deliver drugs but also genetic materials to the posterior segment of the eye, we consider that liposomes are promising nanoparticles for the therapy of multiple intraocular illnesses.
