Ocular in situ gel: An overview

Abstract

Eye is the most sensitive organ of the body. Designing of ocular drug delivery system is the most challenging field for pharmaceutical scientists as less than 5% of administered drug enters the eye due to the complicated anatomical structure of the eye, small absorptive surface and low transparency of the cornea, lipophilicity of corneal epithelium, pre corneal loss (due to nasolacrimal drainage), bonding of the drug with proteins contained in tear fluid, blinking, low capacity of conjunctival sac, that restricts the entry of drug molecule at the site of action and ultimately leads to poor ocular therapy. To improve ophthalmic drug bioavailability, there are considerable efforts directed towards newer drug delivery systems for ophthalmic administration. These novel drug delivery systems offer manifold advantages over conventional systems as they increase the efficiency of drug delivery by improving the release profile and also reduce drug toxicity. A lot of research going on in this area proves the fact that in situ gelling systems can be beneficial in the ocular drug delivery. In situ gel forming systems are drug delivery systems that are in solution form before administration in the body but once administered, undergo in situ gelation, to form a gel triggered by external stimulus such as temperature, pH etc. This review is to Specify a brief summary about in situ gels, various approaches for in situ gelling systems, different types of polymers used in in situ gels, their mechanisms of gel formation and evaluation of polymeric in situ gel.Keywords: in situ gel, polymers, Temperature induced in situ gel system, pH induced in situ gel system, Ion activated systems.

Combination of Nanomicellar Technology and In Situ Gelling Polymer as Ocular Drug Delivery System (ODDS) for Cyclosporine-A

“…Here, the optimized CyA nanomicellar formulation was added to different GG-LA concentrations in an aqueous vehicle where an equilibrium among mono- and divalent ions was chosen. According to Majeed and Khan [ 25 ], gelation should prolong the residence time of the drug at the target site and should increase its bioavailability, calculated as the area under curve.…”

“…The amount of CyA solubilized (CyA-In) by using the different binary surfactant mixtures was determined by RP-HPLC [ 25 ]. An aliquot (1.0 mL) of each NxCyA-ASN was added to acetonitrile (ACN, 20.0 mL) to favor the dissolution of CyA into organic solvent [ 32 ].…”

“…COR-100 EpiCorneal™ reconstituted tissues were chosen as biological substrate to evaluate the capability of CyA loaded into ASN formulations to permeate through corneal tissues [ 25 ]. COR-100 EpiCorneal™ reconstituted tissues were preliminary equilibrated overnight in culture medium (COR-100 ASY medium) at Standard Cell Culture Conditions (SCC, 37 °C, 5% CO 2 ) in line with the Mattek protocol, whereupon the tissues were transferred into two different 12-well plates and equilibrated with 500 µL of Krebs Ringer Bicarbonate buffer (KRB, pH 7.4, receiving phase) for 30 min before the beginning of each treatment.…”

“…CyA detection wavelength and retention time was 210 nm and 32 min, respectively. The amount of drug in the samples was determined by comparison with appropriate external standard curves [ 25 ]. The calibration curves were obtained by applying the least square linear regression analysis by using Prism 8 software (GraphPad Software 164 Inc., San Diego, CA, USA).…”

“…Although it has been proven that they are more effective in increasing the bioavailability and/or reducing the ocular toxicity of the drug, blurred vision due to excessive viscosity was reported as an adverse effect [ 24 ]. This unpleasant effect, although to a lesser extent than those observed for ointments, is associated with other positive features such as decreased drug nasolacrimal drainage, reduced systemic side effects and possibility to administer a well-determined and reproducible amount of drug, in contrast to the typical gel [ 25 ].…”