Applications of a 7-day Caco-2 cell model in drug discovery and development.

Oral delivery is the preferred route of administration and therefore good absorption after oral dosing is a prerequisite for a compound to be successful in the clinic. The prediction of oral bioavailability from in vitro permeability assays is thus a valuable tool during drug discovery and development. Caco-2 cell monolayers mimic the human intestinal epithelium in many aspects.

Using ovality to predict nonmutagenic, orally efficacious pyridazine amides as cell specific spleen tyrosine kinase inhibitors.

Inhibition of spleen tyrosine kinase has attracted much attention as a mechanism for the treatment of cancers and autoimmune diseases such as asthma, rheumatoid arthritis, and systemic lupus erythematous. We report the structure-guided optimization of pyridazine amide spleen tyrosine kinase inhibitors. Early representatives of this scaffold were highly potent and selective but mutagenic in an Ames assay.

In vitro to in vivo extrapolation and physiologically based modeling of cytochrome P450 mediated metabolism in beagle dog gut wall and liver.

The beagle dog is a widely used in vivo model to guide clinical formulation development and to explore the potential for food effects. However, the results in dogs are often not directly translatable to humans. Consequently, a physiologically based modeling strategy has been proposed, using the dog as a validation step to verify model assumptions before making predictions in humans.

Liposomal siRNA delivery.

With the recent discovery of small interfering RNA (siRNA), to silence the expression of genes in vitro and in vivo, there has been a need to deliver these molecules to the cell nucleus. Forming a lipid/nucleic acid complex has become a solution and is explored here. Certain methods and ideas are used, such as: the positive/negative electrostatic interaction with a cationic lipid and an anionic RNA molecule, the size of the lipid vesicle aiding the uptake target tissues, targeted lipoplexes which can increase efficiency, and the protection of the siRNA molecule from the natural defenses of the immune system.

Effect of lyophilization and freeze-thawing on the stability of siRNA-liposome complexes.

The purpose of this research was to describe the application of lyophilization in the delivery of siRNA using cationic lipids by addressing the long-term formulation/stability issues associated with cationic lipids and to understand the mechanism of lyoprotection. siRNA liposomes complexes were formed in different potential cyro/lyoprotectants and subjected to either lyophilization or freeze thaw cycles. siRNA, liposomes and/or lipoplexes were tested for activity, SYBR Green I binding, cellular uptake and particle size.

Liposome fluidity alters interactions between the ganglioside GM1 and cholera toxin B subunit.

Cholera toxin is a complex protein with a biologically active protein (A subunit) and a cell targeting portion (B subunit). The B subunit is responsible for specific cell binding and entry of the A subunit. One way to limit potential toxicity of the toxin after exposure is to introduce cellular decoys to bind the toxin before it can enter cells.

Evaluation of two cationic delivery systems for siRNA.

Small interference RNA (siRNA) is an important research tool, and also has the potential for clinical application. RNA interference (RNAi) approaches allow degradation of selective mRNA coding for pathogenic or disease-related proteins. RNAi pathway can be taken advantage of by the delivery of chemically synthesized siRNA.

A gene delivery approach for antimicrobials: expression of defensins.

Introduction: Peptide antibiotics as new therapeutic agents are becoming a popular option to investigate due to their broad bacterial target selectivity and limited resistance problems. Although attractive, these new drug candidates have several limitations including low potency and delivery issues which face all peptides/proteins.

Methods: In this study, we designed a plasmid expression system for human beta defensin 3.

Antimicrobial activities of human beta-defensins against Bacillus species.

Natural defences in the human body function to protect us from numerous environmental toxins and exposure to potential harmful biological agents. An important frontline defence is antimicrobial peptides. These peptides occur at environmental interfaces and serve to limit bacterial invasion.

Sulfhydryl based cationic surfactants and the impact of polyanions on disulfide bond formation: implications for gene transfer vectors.

Compacting plasmid DNA (pDNA) into a small size is a fundamental necessity for the efficient in vivo transfer of nucleic acids to somatic cells. An approach for accomplishing this is to condense pDNA using cationic detergents with sulfhydryl groups, near their critical micelle concentration. In this study, a model surfactant was used to study how the rate of disulfide bond formation relates to environmental factors.

Polyethylenimine strategies for plasmid delivery to brain-derived cells.

The introduction of effective transfection reagents has had a dramatic impact on basic scientific studies over the past decade and is methodically becoming a clinical relevant agent. An area where these agents have had little impact to date is in transfection of neuronal cells either in vivo or in vitro. The poor results, obtained with these cells, likely arise from the innate properties of the cell itself such as its post-mitotic state and its fragility to the transfection agent.