curves for pantoprazole sodium sesquihydrate in each of 0.1N Hcl (pH 1.2) and phosphate buffer (pH 6.8) were assessed from absorbance values, at λmax of a series of pantoprazole sodium sesquihydrate solutions containing different concentration of pantoprazole as shown in figure (1) and figure (2).
The proposed nanoprecipitation (solvent displacement or interfacial precipitation) [143-148] method enabled the formulation of polymeric nanoparticles by using organic phase with different concentrations of Eudragit S100 (ES100) and HPMC phthalate HP55 with using Tween 80 and Poloxamer 407 as surfactant with different concentrations and different ratio of organic phase: aqueous phase. Although, all formulae produce nanoparticles, formulation factors significantly affect the size of prepared polymeric nanoparticles.
3.1. Effect of polymer concentration and polymer type on particle size of plain PNPs :
Particle size of Eudragit S100 and HPMC Phthalate HP55 nanoparticles was directly proportional to polymer concentration (Eudragit S100 and HPMC Phthalate HP55 concentration respectively) as the particles size increased with increasing polymer concentration [211, 212] and this may be due to increasing the concentration of dissolved polymer resulted in increasing organic phase viscosity and reducing the efficiency of stirring which caused formation of the bigger emulsion droplets [213] and this can be also attributed to that higher viscosity that is predictable to increase polymer – polymer and polymer-solvent interactions [147, 214].
When polymer concentration in the case of Eudragit S100 and HPMC Phthalate HP55 was increased from 0.2 gm% to 0.8 gm% with Tween 80 concentration of 0.5% w/v and phase ratio of (1:2), particle size was increased from 390±9.4634 to 714±2.0548 and from 434±3.0912 to 863±0.9428 nm respectively. The same effect of polymer concentration on particle size was the same either in the case of increasing Tween 80 concentration and /or increasing the phase ratio as shown in the tables (4, 6 and 8) and figures (3, 5 and 7).
When polymer concentration in the case of Eudragit S100 and HPMC Phthalate HP55 was increased from 0.2 gm% to 0.8 gm% with Poloxamer 407 concentration of 0.5% w/v and phase ratio of (1:2), particle size was increased from 404±8.6538 to 747±1.6997 and from 598±1.633 to 905±4.0277 nm respectively. The same effect of polymer concentration on particle size was the same either in the case of increasing Poloxamer 407 concentration and / or increasing the phase ratio as shown in the tables (5, 7 and 9) and figures (4, 6 and 8).
These results were found to agree with the results of both Galindo-Rodriguez et al., 2004 [149] who prepared nanoparticles of Eudragit L100-55 using nanoprecipitation method to determine effect of polymer concentration on nanoparticle size using different organic solvents and he found that in all cases, increasing polymer concentration in organic phase resulted in increasing mean size [149],and D. Quintanar-Guerrero et al., 199