Test for Clarity test: The clarity of the formulated solution is determined by visual inspection under a black and white background.
Texture analysis: The consistency, firmness, and cohesiveness of in-situ gel are assessed using a texture profile analyzer. This analyzer mainly indicates gel strength and ease of administration in vivo. Higher values of gel adhesiveness are needed to maintain intimate contact with mucous surfaces.
Determination of pH: pH can be determined by formulation
is taken in a beaker and 1 ml sodium
hydroxide is added dropwise with continuous stirring. pH is checked by using a pH
meter.
Gelling capacity: In-situ gel is mixed with simulated
tear fluid (in the proportion of 25: 7
i.e. application volume 25 µl and normal volume of tear fluid in the eye is 7
µl) to find out the gelling capacity of the ophthalmic product. The gelation was
assessed visually by noting the time for and time taken for dissolution of the
formed gel.
Rheological studies: The viscosity was measured by
using a Brookfield viscometer, cone &
plate viscometer. In-situ gel formulation is placed in the sample tube. The
formulation should have a viscosity of 5-1000 mPas, before gelling, and after
ion gel activation by the eye will have a viscosity of about 50-50,000 mPas.
In-vitro drug release studies: In-vitro release study
of insitu gel solution is carried out by using Franz diffusion cell. The best-fit
model is checked for Krosmeyers Peppas and Fickinian diffusion mechanisms for
their kinetics.
Sterility testing: Sterility testing is carried out
as per the IP 1996. The formulation is incubated for not less than 14 days at
300- 350°C in the fluid thioglycollate medium to find the growth of bacteria
and at 200-250°C in the soybean casein digest medium to find the growth of
fungi in the formulation.
Isotonicity evaluation: Isotonicity is an important
characteristic of the ophthalmic preparations. Isotonicity has to be maintained
to prevent tissue damage or irritation of the eye. All ophthalmic preparations
are subjected to isotonicity testing since they exhibited good release
characteristics gelling capacity and the requisite viscosity.