Selection of an analytical method for evaluating bovine serum albumin concentrations in pharmaceutical polymeric formulations

Bovine serum albumin (BSA) is a commonly used model protein in the development of pharmaceutical formulations. In order to assay its release from various dosage forms, either the bicinchoninic acid (BCA) assay or a more specific size-exclusion high performance liquid chromatography (SE-HPLC) method are commonly employed. However, these can give erroneous results in the presence of some commonly-used pharmaceutical excipients. We therefore investigated the ability of these methods to accurately determine BSA concentrations in pharmaceutical formulations that also contained various polymers and compared them with a new and compared with a new reverse-phase (RP)–HPLC technique. We found that the RP-HPLC technique was the most suitable method. It gave a linear response in the range of 0.5 -100 µg/ml with a correlation coefficient of 0.9999, a limit of detection of 0.11 µg/ml and quantification of 0.33 µg/ml. The performed ‘t’ test for the estimated and theoretical concentration indicated no significant difference between them providing the accuracy. Low % relative standard deviation values (0.8-1.39%) indicate the precision of the method. Furthermore, the method was used to quantify in vitro BSA release from polymeric freeze-dried formulations.

Alternative antecedents, probabilities, and the suppression of fallacies in Wason's selection task

Three experiments examined the influence of a second rule on the pattern of card selections on Wason's selection task. In Experiment 1 participants received a version of the task with a single test rule or one of two versions of the task with the same original test rule together with a second rule. The probability of q was manipulated in the two-rules conditions by varying the size of the antecedent set in the second rule. The results showed a significant suppression of q card and not-p card selections in the alternative-rule conditions, but no difference as a function of antecedent set size. In Experiment 2 the size of the antecendent set in the two-rules conditions was manipulated using the context of a computer printing double-sided cards. The results showed a significant reduction of q card selections in the two-rules conditions, but no effect of p set size. In Experiment 3 the scenario accompanying the rule was manipulated, and it specified a single alternative antecedent or a number of alternative antecedents. The q card selection rates were not affected by the scenario manipulation but again were suppressed by the presence of a second rule. Our results suggest that people make inferences about the unseen side of the cards when engaging with the task and that these inferences are systematically influenced by the presence of a second rule, but are not influenced by the probabilistic characteristics of this rule. These findings are discussed in the context of decision theoretic views of selection task performance (Oaksford Chater, 1994).

A two compartment in vitro release model for the testing of HIV microbicide formulations

BACKGROUND: In vitro release testing of vaginal formulations is usually performed in a one-compartment model (OCM) where the release medium, usually comprising pH-adjusted water, an aqueous surfactant solution or a solvent-water solution, provides sink conditions throughout the release experiment. Although this model is useful in evaluating the effect of formulation parameters upon release, it rarely reflects in vivo conditions. Here we report use of a two-compartment diffusion cell model (TCM, comprising a small volume donor, a large volume receptor, and separated by a model epithelial membrane) to more closely mimic in vivo vaginal release and tissue absorption following administration of a UC781 vaginal ring.

METHODS: Macaque-sized matrix silicone elastomer vaginal rings containing 100mg UC781 were prepared by injection molding, and in vitro release testing performed using both OCM (20mL simulated vaginal fluid, SVF) and TCM (5mL SVF in donor cell and variable quantities of Tween 80; silicone elastomer membrane; 100mL 3:2 ethanol/water in receptor cell). In the TCM, drug levels were measured by HPLC in both donor and receptor cells, representing fluid and tissue levels respectively. Rings containing 100mg UC781 and 10% w/w Tween 80 were also manufactured and tested.

RESULTS: The amount of UC781 released from rings was significantly influenced by the choice of release model. Greatest release (56mg/14 days) was measured in the ethanol/water OCM, compared with no measurable release into SVF only. Increasing the concentration of Tween 80 in the SVF medium (1, 3 and 5% w/w) led to increased UC781 release (11, 16 and 18mg, respectively), demonstrating that vaginal fluid solubility of UC781 may be rate-determining in vivo. In the TCM, UC781 accumulates in the receptor cell medium over time, despite not being measured in the donor medium containing the ring device. Incorporation of Tween 80 directly into the ring provided enhanced release in both donor and receptor cells.

CONCLUSIONS: Release of UC781 was influenced by the choice of release medium and the inclusion of Tween 80 in the ring. Although use of SVF-only in the OCM indicated no measurable UC781 release from rings, data from the TCM confirms that UC781 is not only released but is also capable of penetrating across the model epithelial membrane. The TCM may therefore provide a more representative in vitro release model for mimicking in vivo absorption.

HDQ (1-hydroxy-2-dodecyl-4(1H)quinolone), a high affinity inhibitor for mitochondrial alternative NADH dehydrogenase

Alternative NADH dehydrogenases (NADH:ubiquinone oxidoreductases) are single subunit respiratory chain enzymes found in plant and fungal mitochondria and in many bacteria. It is unclear how these peripheral membrane proteins interact with their hydrophobic substrate ubiquinone. Known inhibitors of alternative NADH dehydrogenases bind with rather low affinities. We have identified 1-hydroxy-2-dodecyl-4(1H)quinolone as a high affinity inhibitor of alternative NADH dehydrogenase from Yarrowia lipolytica. Using this compound, we have analyzed the bisubstrate and inhibition kinetics for NADH and decylubiquinone. We found that the kinetics of alternative NADH dehydrogenase follow a ping-pong mechanism. This suggests that NADH and the ubiquinone headgroup interact with the same binding pocket in an alternating fashion.

Secondary Transfer Effects of Intergroup Contact: Alternative Accounts and Underlying Processes

Although intergroup contact is one of the most prominent interventions to reduce prejudice. the generalization of contact effects is still a contentious issue This research further examined the rarely studied secondary transfer effect (STE, Pettigrew, 2009) by which contact with a primary outgroup reduces prejudice toward secondary groups that are not directly involved in the contact Across 3 cross-sectional studies conducted in Cyprus (N = 1.653), Northern Ireland (N = 1,973). and Texas (N = 275) and 1 longitudinal study conducted in Northern Ireland (N = 411). the present research sought to systematically rule out alternative accounts of the STE and to investigate 2 potential mediating mechanisms (ingroup reappraisal and attitude generalization) Results indicated that, consistent with the STE. contact with a primary outgroup predicts attitudes toward secondary outgroups. over and above contact with the secondary outgroup, socially desirable responding. and prior attitudes Mediation analyses found strong evidence for attitude generalization but only limited evidence for ingroup reappraisal as an underlying process Two out of 3 tests of a reverse model, where contact with the secondary outgroup predicts attitudes toward the primary outgroup. provide further evidence for an indirect effect through attitude generalization Theoretical and practical implications of these results are discussed, and directions for future research are identified