Human colon adenocarcinoma (Caco-2) cells, when grown on semipermeable filters, spontaneously differentiate in culture to form confluent monolayers which both structurally and functionally resemble the small intestinal epithelium. Because of this property they show promise as a simple, in vitro model for the study of drug absorption and metabolism during absorption in the intestinal mucosa. In the present study, the transport of several model solutes across Caco-2 cell monolayers grown in the Transwell diffusion cell system was examined. Maximum transport rates were found for the actively transported substance glucose and the lipophilic solutes testosterone and salicyclic acid. Slower rates were observed for urea, hippurate, and saliylate anions and were correlated with the apparent partition coefficient of the solute. These results are similar to what is found with the same compounds in other, in vivo absorption model systems. It is concluded that the Caco-2 cell system may give useful predictions concerning the oral absorption potential of new drug substances.
"To date, there are no studies comparing the absorption properties of IS in TFH and its pure form and elucidating the possible interaction mechanism. The Caco-2 cell line was derived from human colorectal carcinoma , and its monolayers were a well-accepted model of human intestinal absorption because they could exhibit many morphological and functional characteristics with mature enterocytes (Artursson and Karlsson, 1991; Hilgers et al., 1990). Thus, the present study characterizes the absorption properties of IS in TFH and its pure form through transepithelial transport and cellular uptake experiments using a Caco-2 cell model. "
"Cellular toxicity/permeability screening was performed as previously described ,  with minor modifications. Briefly, Caco-2 cells were grown to confluence for 16 days on 1 µm filters in 24-well plates. "
[Show abstract][Hide abstract] ABSTRACT: Developing siRNA therapeutics poses technical challenges including appropriate molecular design and testing in suitable pre-clinical models. We previously detailed sequence-selection and modification strategies for siRNA candidates targeting STAT6. Here, we describe methodology that evaluates the suitability of candidate siRNA for respiratory administration. Chemically-modified siRNA exhibited similar inhibitory activity (IC50) against STAT6 in vitro compared to unmodified siRNA and apical exposure testing with Caco-2 cell monolayers showed modification was not associated with cellular toxicity. Use of a modified RNA extraction protocol improved the sensitivity of a PCR-based bio-analytical assay (lower limit of siRNA strand quantification = 0.01 pg/µl) which was used to demonstrate that lung distribution profiles for both siRNAs were similar following intra-tracheal administration. However, after 6 hours, modified siRNA was detected in lung tissue at concentrations >1000-fold higher than unmodified siRNA. Evaluation in a rat model of allergic inflammation confirmed the persistence of modified siRNA in vivo, which was detectable in broncho-alveolar lavage (BAL) fluid, BAL cells and lung tissue samples, 72 hours after dosing. Based upon the concept of respiratory allergy as a single airway disease, we considered nasal delivery as a route for respiratory targeting, evaluating an intra-nasal exposure model that involved simple dosing followed by fine dissection of the nasal cavity. Notably, endogenous STAT6 expression was invariant throughout the nasal cavities and modified siRNA persisted for at least 3 days after administration. Coupled with our previous findings showing upregulated expression of inflammatory markers in nasal samples from asthmatics, these findings support the potential of intranasal siRNA delivery. In summary, we demonstrate the successful chemical modification of STAT6 targeting siRNA, which enhanced bio-availability without cellular toxicity or reduced efficacy. We have established a robust, sensitive method for determining siRNA bio-distribution in vivo, and developed a nasal model to aid evaluation. Further work is warranted.
PLoS ONE 02/2014; 9(2):e90338. DOI:10.1371/journal.pone.0090338 · 3.23 Impact Factor
"4.8.2. Cell-based models More than two decades after their introduction (Hidalgo et al., 1989; Artursson, 1990; Hilgers et al., 1990), cultures of cell monolayers , such as Caco-2, are still routinely used in drug development to assess intestinal drug permeability. Although the cell-based models cannot compete with artificial membranes with respect to speed and price, they are applied when more quantitative information is required. "
[Show abstract][Hide abstract] ABSTRACT: Preformulation measurements are used to estimate the fraction absorbed in vivo for orally administered compounds and thereby allow an early evaluation of the need for enabling formulations. As part of the Oral Biopharmaceutical Tools (OrBiTo) project, this review provides a summary of the pharmaceutical profiling methods available, with focus on in silico and in vitro models typically used to forecast active pharmaceutical ingredient's (APIs) in vivo performance after oral administration. An overview of the composition of human, animal and simulated gastrointestinal (GI) fluids is provided and state-of-the art methodologies to study API properties impacting on oral absorption are reviewed. Assays performed during early development, i.e. physicochemical characterization, dissolution profiles under physiological conditions, permeability assays and the impact of excipients on these properties are discussed in detail and future demands on pharmaceutical profiling are identified. It is expected that innovative computational and experimental methods that better describe molecular processes involved in vivo during dissolution and absorption of APIs will be developed in the OrBiTo. These methods will when successful provide early insights into successful pathways (medicinal chemistry or formulation strategy) and are anticipated to increase the number of new APIs with good oral absorption being discovered.
European journal of pharmaceutical sciences: official journal of the European Federation for Pharmaceutical Sciences 11/2013; 57(1). DOI:10.1016/j.ejps.2013.10.015 · 3.35 Impact Factor
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