Preparation and characterization of self-nano emulsifying powders
As shown in Table 2, solid self-nanoemulsifying formulations were prepared by loading optimized liquid SNEF i.e. SNEF2 over the surface of the adsorbent carriers like neusilin US2, aerosil 200, avicel PH 101, maltodextrin, and pearlitol SD 200 at varying carrier loads to overcome the major problems associated with the liquid SNEFs such as drug leakage, low stability and portability. Among the various carriers verified neusilin US2 showed high loading capacity (0.7 gram of neusilin US2 per one gram of liquid SNEF) compared to other carriers and produced free flowing self-nano emulsifying powder with 58.8% load of liquid SNEF. This may be due to larger surface area (300 m2/g), low bulk density (0.15 g/mL) and high oil adsorbing capacity (3.2 mL/g) of neusilin US2. The flow properties of the SNEPN prepared using neusilin US2 showed good flow characteristics with an angle of repose value of 34.53±2.1º and flow rate of less than 10 sec from funnel. Whereas the SNEPs prepared with other carriers required large quantities of carriers (Table 2) to obtain free flowing powders. Based on these results SNEPN prepared using neusilin US2 as carrier was optimized and studied further.
Redispersibility of SNEPN
The reconstitution nature of the SNEPN was tested by determining globule size, polydispersity index, zeta potential and comparing them with the results obtained for SNEF. The globule size of the emulsion formed form the SNEPN was found to be 35.8±0.21nm with polydispersity index of 0.17±0.05 and zeta potential of -10.3±0.1mV. The size analysis results of SNEP when compared with SNEF were not statistically significant (<0.05) indicating the preservation of the self-emulsification ability of SNEF even after solidification using inert carrier (neusilin US2). This was in accordance with the previous reports.5
Solid state characterization
Fourier transform infrared spectroscopic studies
FTIR studies were performed to know the physicochemical interactions between drug and components of SNEPN based on characteristic drug peaks absence or shifting. The FTIR spectrum of pure ISR, neusilin US2 and SNEPN were shown in Figure 2. The spectrum of pure ISR showed intense, well defined characteristic absorption peaks at 3354 (N-H amine stretching), 2945 (C-H alkane stretching), 1698, 1661 (N-H amine in the plane bending vibrations, C=O carboxylic acid stretching), 1485 (CH3 alkane in the plane bending, C=C aromatic stretching), 1367, 1309 (C-O carboxylic acid stretching), 1233, 1212, 1120, 1106, 1019 (C-N amine stretching), 998 (O-H carboxylic acid out of plane bending), 867, 756, 748, 622 (C-H aromatic out of plane bending). Neusilin US2 showed principle absorption peaks at 3457 cm−1, 1638 cm−1, 1021 cm−1, 680 cm−1, 449 cm−1. The infrared spectrum of SNEPN showed all the characteristic peaks of neusilin US2 at the same positions along with drug peaks at 2945 cm−1, 1485 cm−1, 1698 cm−1, 1485, 1367 cm−1 and...