الفهرس 
General IntroductionOnly 14 pages are availabe for public view
 |  | from | 251 |  |  |
| | | from | 251 | | |
Abstract
The ultimate goal of this work was to fabricate and characterize stable redispersible spray dried nanosuspension (SDN) of a poorly soluble anti glaucoma drug, acetazolamide (ACZ), eligible for ocular delivery. The characteristics of ACZ nanosuspension (NS) allowed for targeting the cornea overcoming the ocular biological barriers by modulating NS characteristics through treatment with polymers known with their mucoadhesive nature.
The antisolvent precipitation (AS-PT) coupled with sonication was adopted for fabrication of ACZ-NS. Using a systematic one factor at a time experimental design, various process and formulation variables were optimized to ensure the highest ACZ loading efficiency, particle size (PS) in the range of 100-300nm and a homogenous PS distribution. The system stability was also modulated by combining steric and electrostatic stabilization through the inclusion of charged surfactant (SAA) soya lecithin (SL), cationic polymer chitosan (CS) and anionic polymers hyaluronic acid (Y) and poly-γ-glutamic acid (PG).
Aiming at enhancing long term stability, spray drying was adopted to convert NS into a redispersible dry powder. Various process conditions as well as antiadherent and matrix former combinations (leucine (Leu) and mannitol (Man)) and nanoparticles to carrier ratio (NPs/C) were optimized to attain the best yield, redispersibility and association efficiency. Redispersion of SDN in isotonicity adjusting agents and sterilization of final product were also considered. Special concern was given to the assessment of the safety and biological activity of the prepared ACZ-SDN implying the modified Draize test and ocular hypertensive model, respectively.
The optimum formulation and process conditions using the polymeric stabilizer polyvinyl alcohol (PVA) were found to be: ACZ concentration: 50mg/mL, solvent to antisolvent ratio: 1:50, 0.2%w/v PVA. The optimized ACZ-NS scored an average PS of 117.4±11.1nm while exhibiting a bimodal particle size distribution (PSD). Combining PVA with the natural lipid soya lecithin (SL) imparted a sort of electrostatic stabilization leading to a unimodal PSD. The PS of ACZ-NS prepared with this stabilizer combination increased with increased SL concentration while 0.05%w/v represented the optimum SL concentration. Using probe sonication for 3min resulted in NS with optimum properties: PS of 105±1.7nm, PDI of 0.23±0.005 and ζ of -31.5±2.8mV.
The combination of PVA with cationic (chitosan (CS)) or anionic (hyaluronic acid (Y) and poly-γ-glutamic acid (PG)) polymers resulted in larger particles with non-uniform preparations. Conversely treating the NS, prepared with the stabilizer combination PVA/SL, with the same polymers did not affect the size significantly. The selected NS showed spherical, uniformly distributed particles with smooth surface when visualized using TEM. DSC and XRPD revealed that both crystalline and amorphous forms of ACZ were present in NS prepared by AS-PT technique. Significant enhancement in ACZ saturation solubility was achieved following formulation of the NS reaching up to seven fold ACZ solubility.
Based on attaining the highest yield and a fast recovery into small nanoparticles following redispersion of the spray dried powders (SDP) in water, the optimum spray drying conditions were found to be: inlet temperature: 110˚C, pump rate: 3%, carrier (C) composition: Leu and Man in the ratio 1:1 and NPs: C ratio of 1:2. The optimized SDN scored a high yield reaching 72.6±0.79%w/w, small PS of 177.9±12.6nm after redipsersion in deionized water and high AE of 96.6±3.2%w/w. The absence of DMSO in the SDP was confirmed by proton magnetic resonance and the thermogravimetric analysis revealed the presence of low moisture content (less than 4%w/w). Non agglomerated, collapsed, doughnut shaped particles decorated with fine crystals on their surfaces were clearly shown in the SEM. ACZ-SDN crystallinity was investigated using DSC and XRPD which showed a reduced crystallinity compared to untreated ACZ. The release of ACZ from ACZ-SDN was completed after 480min and the presence of treating polymers did not affect the release ACZ from the SDN. Glycerol of 2.6%w/v concentration represented the best isotonicity adjusting agent that maintained NS properties, while the resultant pH was in range of 5.65- 5.89 the most suitable pH for both ACZ stability and eye comfort. The recovery of NPs from SDN redispersed in 2.6% w/v glycerol was successfully achieved and confirmed using TEM revealing spherical particles in the range of 100-300nm. Gamma radiation of 5KGy was a successful approach to obtain sterile product, while maintaining NS physicochemical properties. selected SDN formula was found to be stable for 180 days in desiccator and also after redispersion in selected isotonic agent for 10 days at 5˚C without significant changes in PS, PDI and ζ.
The safety of the selected ACZ-SDN was confirmed using the Modified Draize test. Through the test scoring (Iirr) and the histopathological examination, it was evident that tested formulae did not induce significant irritation or alteration in ocular tissues; hence it was a safe formulation for ocular delivery. The ocular hypotensive efficacy of ACZ-SDN was further assessed following induction of glaucoma in rabbits. The selected formula was capable of reducing intraocular pressure for more than 8h in a significant manner compared to untreated ACZ.
Hence, it could be concluded that safe and efficacious formulation for ocular delivery of poorly soluble anti glaucoma drug (ACZ) was successfully prepared and characterized implying the innovation of nanosuspension technology coupled with spray drying technique.
Keywords: Acetazolamide, class IV drug, ocular delivery, spray drying, nanoprecipitation, hyaluronic acid, leucine, mannitol, poly-γ-glutamic acid, chitosan.