الفهرس 
Pharmaceutical study on some ocular drug delivery systems
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Abstract
Ocular infections are classified into superficial keratitis, conjunctivitis or deep infections
such as corneal abscesses and blepharitis. The eye is characterized by the presence of
physiological and anatomical barriers such as the corneal epithelium, blood-aqueous barrier
and blood-retinal barrier that contribute to inefficient drug delivery to the organ tissues.
Herein, we focused on the development of a formulation that could prolong the residence
time of the antibacterial agent and enhance its corneal penetration to maximize the drug effects
both superficially and at the deep tissues.
The ionic gelation method was used to prepare nanoparticles (NPs) from CS polymer using
sodium tripolyphosphate (TPP) by the induced precipitation method.
A full factorial design applied to evaluate the effect of three independent variables namely a)
CS concentration, b) CS:TPP ratio, and c) %Tween on particle size and morphology of blank
NPs was evaluated using images generated from Transmission electron microscope (TEM).
Gemifloxacin (GM) is a fourth-generation fluoroquinolone approved by the Food and Drug
Administration (FDA) in April 2003. Its antibacterial activity is exerted by inhibiting DNA
synthesis via the inhibition of type II, IV topoisomerase and DNA gyrase enzymes. Most
fluoroquinolone’s activity is attributed to one enzyme that renders them ineffective as a result
of single mutations in their target. GM is a dual targeting agent and retains its activity against
mutations in either or both targets.
Compared with other fluoroquinolones, GM possesses enhanced in vitro activity against
Streptococcus pneumonia, gram-negative and atypical pathogens. It has favorable
pharmacokinetic/pharmacodynamic characteristics that could
preserve the potential of this drug class and offer optimally effective regimens for patients.
Eight forms of GM-loaded CS nanoparticles (NPs) were formulated by ionotropic gelation.
The effect of independent formulation factors on particle size, entrapment efficiency, and
cumulative in-vitro release were studied, the optimal formula was selected using Design
Expert® software, then Differential scanning calorimetry (DSC) and X-ray diffraction (XRD)
carried out on the selected formulation and demonstrated the interaction between CS and GM.
The biological performance of the selected formulation was carried out on albino rabbits.
Pharmacokinetic and pharmacodynamic studies revealed that the ocularly-administered NPs
significantly improve the pharmacokinetic profile of the loaded GM as well as the therapeutic
efficacy against ocular infections.
Accordingly, our study illustrated the capability of the CS NPs to promote the antibacterial
activity of GM against eye infections via ocular administration. The obtained results can be
summarized as follow:
• The wavelength of maximum absorbance (λmax) for GM was 264.5 in a CS solution
of pH 5.
• FTIR thermograms showed that similar peaks of pure components were identified in
the spectrum of their physical mixture and blend film with minor differences in
frequencies in addition to the presence of new peaks, confirming the formation of an
intercalated structure.
• Agar dilution test of GM against Staphylococcus aureus showed a minimum inhibitory
concentration (MIC) of 0.06 µg/ml that was raised to 0.125 µg/ml on mixing with CS.
• Agar dilution test of GM against Pseudomonas aeruginosa showed MIC 1 µg/ml that
was not affected by mixing with CS. Blank CS NPs (Sample1:Sample18) were formulated and the effect of variable
formulation factors on particle size and morphology was studied, it was revealed that
higher CS concentration (X1) increased the particle size and CS:TPP ratio (X2) that
negatively affected the particle size, whereas %Tween (X3) showed a minor effect on
particle size.
• GM loaded CS NPs (F1:F8) were successfully prepared by the ionotropic gelation
technique using a 23
factorial design. Each variable was tested on 2 levels, and they were
characterized for particle size (PS), percent entrapment efficiency (%EE) and percent
cumulative release (%CR). Design Expert® 7.0.0 software (STAT-EASE, USA)-
generated equations were used to investigate the effect of independent formulation
factors on the previously stated dependent counterparts and the study revealed that:
o CS concentration (X1) exerted the main effect on PS in a significant model with
a p-value of 0.047, R- Squared value (R2
) of 0.9994 and equation terms (X2,
X1 X2, X1 X3, X2 X3, and X1 X2 X3).
o %EE was evaluated through a significant model with a P-value of 0.0457, R2
of 0.709 and terms of significance were X1 and X2.
o A model of P-Value 0.028 and R2
value 0.9887 were implied to analyze %CR,
the model terms were X1, X2, X3, X1 X2, X2X3.
• The release profile of the drug from the selected formula fitted the Koresmayer Peppas
diffusion model, according to the diffusion exponent “n” value the drug release from
the formulated NPs followed non-Fickian diffusion except F5 that followed Fickian
diffusion, where the ‘n’ value was 0.48, 0.54, 0.44, 0.50, 0.42, 0.59, 0.48 and 0.82 for
the eight formulas from F1to F8, respectively.
• Applying statistical analysis using one-way ANOVA followed by Bonferroni post-test
to compare the effect of formulation factors on the PS, EE and %CR data obtained from
the eight formulations showed significance (p<0.05) of different formulation factors on
the studied parameters.
• Based on applying the desirability function on Design Expert® software regarding the
particle size, %EE, and %CR, the optimized formula named F5 with mean diameter of
158. 4 nm, average entrapment efficiency 46.6% and cumulative release 74.9% was
chosen for further in-vitro and in-vivo evaluation.
• Pharmacokinetics studies were carried out on rabbits revealed that the ocularlyadministered NPs significantly increased the loaded GM concentration in the tear and
aqueous humour samples that suggested enhancement of precorneal retention and
transcorneal permeation, respectively.
• Pharmacodynamic studies manifested that ocularly-administered chitosan NPs
intensified the in vivo antibacterial activity of the loaded GM against Staphylococcus
aureus and Pseudomonas aeruginosa.
The above-mentioned outcomes point out the potentiality of formulating GM in the form of
mucoadhesive CS nanoparticles for better corneal retention, permeation, sustained release
profile and steady concentration that could ultimately enhance drug efficacy against ocular
infections and reduce possibilities of both resistance emerging and systemic effect.