Physicochemical Properties and Excipient Compatibility studies of Probiotic Bacillus coagulans Spores

The probiotic formulations are susceptible to loss in viability due to formulation, processing, storage and in vivo environment. The aim of the present study was to perform preformulation studies of probiotic Bacillus coagulans spores to aid designing of stable formulations. Bacillus coagulans spores were studied for hygroscopicity, resistance to compaction force, aqueous pH stability, and excipient compatibility. The spores were found to be moderately hygroscopic with a significant loss of microbiological assay at water activity value of more than 0.5. Progressive loss of viability from 95% to 58% was observed with increase in compaction force from 1000 to 4000 psi. Aqueous suspension of Bacillus coagulans spores in buffer solutions of pH 1.2 to 8 showed rapid degradation with maximal stablility in pH 6.8. Excipient compatibility studies showed reduced assay with citric acid monohydrate, meglumine and sodium starch glycolate. The loss of activity seemed to be related to the moisture uptake, free and bound water present in the bulk

Wettability and surface chemistry of crystalline and amorphous forms of a poorly water soluble drug

The present study compares energetics of wetting behavior of crystalline and amorphous forms of a poorly water soluble drug, celecoxib (CLB) and attempts to correlate it to their surface molecular environment. Wettability and surface free energy were determined using sessile drop contact angle technique and water vapor sorption energetics was measured by adsorption calorimetry. The surface chemistry was elucidated by X-ray photoelectron spectroscopy (XPS) and crystallographic evaluation. The two solid forms displayed distinctly different wetting with various probe liquids and in vitro dissolution media. The crystalline form surface primarily exhibited dispersive surface energy (47.3 mJ/m2), while the amorphous form had a slightly reduced dispersive (45.2 mJ/m2) and a small additional polar (4.8 mJ/m2) surface energy. Calorimetric measurements, revealed the amorphous form to possess a noticeably high differential heat of absorption, suggesting hydrogen bond interactions between its polar energetic sites and water molecules. Conversely, the crystalline CLB form was found to be inert to water vapor sorption. The relatively higher surface polarity of the amorphous form could be linked to its greater oxygen-to-fluorine surface concentration ratio of 1.27 (cf. 0.62 for crystalline CLB), as determined by XPS. The crystallographic studies of the preferred cleavage plane (0 2 0) of crystalline CLB further supported its higher hydrophobicity. In conclusion, the crystalline and amorphous forms of CLB exhibited disparate surface milieu, which in turn can have implications on the surface mediated events

Impact of Crystal Habit on Biopharmaceutical Performance of Celecoxib

Poor biopharmaceutical performance of Biopharmaceutical Classification System (BCS) class II drug molecules is a major hurdle in the design and development of pharmaceutical formulations. Anisotropic surface chemistry of different facets in crystalline material affects physicochemical properties, such as wettability, of drugs. In the present investigation, a molecule-centered approach is presented toward crystal habit modification of celecoxib (CEL) and its effect on oral bioavailability. Two crystal habits of CEL, acicular crystal habit (CEL-A) and a plate-shaped crystal habit (CEL-P), were obtained by recrystallization from toluene at 25 and 60 °C, respectively. Compared to CEL-A, CEL-P exhibited significantly faster dissolution kinetics in aqueous media and significantly higher <i>C</i>_max and shorter <i>T</i>_max in an oral bioavailability study. The significant enhancement in dissolution and biopharmaceutical performance of CEL-P was attributed to its more abundant hydrophilic surfaces compared to CEL-A. This conclusion was supported by wettability and surface free energy determination from contact angle measurements and surface chemistry determination by X-ray photoelectron spectroscopy (XPS), crystal structure modeling, and crystal face indexation

Solid State Characterization of Commercial Crystalline and Amorphous Atorvastatin Calcium Samples

Atorvastatin calcium (ATC), an anti-lipid BCS class II drug, is marketed in crystalline and amorphous solid forms. The objective of this study was to perform solid state characterization of commercial crystalline and amorphous ATC drug samples available in the Indian market. Six samples each of crystalline and amorphous ATC were characterized using X-ray powder diffractometry (XRPD), differential scanning calorimetry (DSC), thermogravimetric analysis, Karl Fisher titrimetry, microscopy (hot stage microscopy, scanning electron microscopy), contact angle, and intrinsic dissolution rate (IDR). All crystalline ATC samples were found to be stable form I, however one sample possessed polymorphic impurity, evidenced in XRPD and DSC analysis. Amongst the amorphous ATC samples, XRPD demonstrated five samples to be amorphous ‘form 27’, while, one matched amorphous ‘form 23’. Thermal behavior of amorphous ATC samples was compared to amorphous ATC generated by melt quenching in DSC. ATC was found to be an excellent glass former with Tg/Tm of 0.95. Residual crystallinity was detected in two of the amorphous samples by complementary use of conventional and modulated DSC techniques. The wettability and IDR of all amorphous samples was found to be higher than the crystalline samples. In conclusion, commercial ATC samples exhibited diverse solid state behavior that can impact the performance and stability of the dosage forms