Introduction. Most ocular drugs when given by topical administration are rapidly cleared by the aqueous humor flowing into the anterior chamber and flushing the drug out via the trabecular meshwork, should they permeate the cornea. The drug will often therefore fail to reach reproducible therapeutic levels near the retina. Unfortunately, drugs in solution can rapidly clear within hours from the posterior cavity upon IVT injection. This reduces efficacy and frequent injections are required, which can lead to undesirable side effects and reduce patient compliance [1]. Electrospinning is one of the technics for production of different fibers for medical and pharmaceutical needs. This technic is being used to enhance the solubility substances in ophthalmology. We have conducted an overview of the polymers investigated in the production of films or tablets for oral dosage forms. Previous studies [1, 2] of electrospun formulations of acyclovir, ciprofloxacin and cyanocobalamin for ocular drug delivery demonstrate that electrospun matrices, such as those prepared in this work, have potential for use as intravitreal implants and improve the solubility of such a water-insoluble substance like acyclovir.

The aim of this review is to describe the main types of fibers for the development of a potential ophthalmological dosage form.

Tasks: to describe suitable polymers for the development of ocular dosage forms prepared by electrospinning.

Results and discussion. The traditional ophthalmological dosage forms have a low bioavailability, a rapid precorneal clearance, and a low corneal permeability. The gelling system or system with a prolonged action (prolonged eye-drops) may be overcome by the application of fibers.

Anatomy of the eye is demonstrated in close connection with ophthalmic delivery and bioavailability of drugs. Combining different properties of pharmaceutical formulations appears to offer a synergy in bioavailability and sustained release with very comfortable conditions of use and prolonged action. Novel formulations, such as prolonged eye-drops and gels or thinnest films for the eye, will be developed and tested in vitro studies.

Table 1. demonstrates the most useful types of polymers in ophthalmology.

Table 1

The most useful types of polymers in ophthalmology

PCL is one of the most useful polymers in the medicine, but in ophthalmology, fibers were described in papers [1] and [9]. Both studies report on fibers with antimicrobial agents. Karataş A. et all develop ofloxacin loaded electrospun fibers for ocular drug delivery. The microbiological study of properties of this fibers shows that freely released ofloxacin from fibers inhibited the growth of the tested bacteria. This study demonstrates that electrospinning had no adverse effects on the activity of the incorporated drug in fibers. That data is interesting for future development of dosage forms with antimicrobial agents for ophthalmology.

Simões S.M. [10] describes syringeable self-assembled cyclodextrin gels for drug delivery: CDs were obtained in two systems to form inclusion complexes. Both types of complexes show stability with variety of drugs via interactions between substances and polymers. Functional groups of polymers are not involved in the other complexes. Other authors, Hu QD et all [11], describe the host-guest interactions of αCD and βCD between polymer and substances. They also report about modification of CDs with polymers due to the potential benefits rendered by cationic protection and improved capability. This modifications help to improve the controlled release by application of responsive structures.

Another benefit of using CDs for nanomedicine includes electrospun fibers of cyclodextrins and poly(cyclodextrins) [12]. They include therapeutic agents. These complexes demonstrate a slowl release that is the most suitable for a perspective ocular dosage form.

Cellulose fibers (HPMC in this studies) with polyethylene oxide PEO [13] were produced by Aydogdu A et all. A uniform structure of these fibers was achieved by increasing a polymer concentration, and their structure was semicrystalline. For next studies and combining PEO with HPMC the developments of uniform and stability fibers for ocular films may be interesting.

In the other studies of Kuang G et al, there were developed polyblend nanofibers for local cancer treatment [14]. PEO was included in the mixture of polymers as a hydrophilic polymer. This study will be used in a new concept of local chemotherapy.

 Cellulose derivatives were prepared by incorporating polyaniline (PAn) fibers into polyvinyl alcohol (PVA) by Bai Y. [15]. These fibers are interesting for ophthalmological drug development because they show excellent water-, thermal-, and near-infrared (NIR) light- properties. Of course, the concentration of polymers should be changed for drug development.

Karczewski A. et al have developed an antimicrobial drug delivery system [16] with PDS fibers. Chitosan, as a more adequate stimulus to facilitate the cell, was used in these fibers. This fiber shows an antimicrobial activity against all bacteria and is cell-friendly. The experience in the use of these fibers have a potential for ophtalmology drug development.

The results of the review of the most useful polymers show that in most cases all polymers are used together. A huge number of ophthalmologic pathologies call for a correct approach to each nosology in each case. The electrospinning method will stipulate for the future development of customized tools for the treatment of ophthalmic pathologies. The development of an ophthalmic insert with the possible introduction of several medicinal substances depending on the condition of each patient is promising.

No conflict of interest was recorded with respect to this article.