Design and in vitro characterization of multistage silicon-PLGA budesonide particles for inflammatory bowel disease.

Inflammatory bowel disease (IBD) affects a confined area of the intestine and, therefore, administration of drugs via oral route is preferable. However, obstacles such as changes in the pH along gastrointestinal tract (GIT), enzymatic activity, and intraluminal pressure may cause low drug availability in the target tissue when delivered orally. Previous studies have pointed out the benefits of using micron-sized particles for targeting inflamed intestinal mucosa and nanoparticles for delivery of anti-inflammatory agents to the affected epithelial cells. We hypothesized that by combining the benefits of micro- and nano- particles, we could create a more efficient delivery system for budesonide, a glucocorticosteroid commonly used for anti-inflammatory IBD therapy. The aim of this study was to develop a novel multistage system for oral delivery designed to increase concentrations budesonidein the inflamed intestinal tissue. The multistage system consists of Stage 1 mesoporous silicon microparticles (S1MP) loaded with stage 2 poly-lactic-glycolic acid (PLGA) budesonide-encapsulating nanoparticles (BNP). BNP were efficiently loaded into S1MP (loading efficiency of 45.9 ± 14.8%) due to the large pore volume and high surface area of S1MP and exhibited controlled release profiles with enhanced drug dissolution rate in biologically relevant pHs. Due to the robustness in acidic pH and their geometry, S1MP protected the loaded budesonide in the acidic (gastric) pH with only 20% release. This allowed for the prolonged release of the BNP in the higher pH conditions (intestinal pH). The sustained release of BNP could facilitate accumulation in the inflamed tissue, enabling BNP to penetrate inflamed mucosa and release active budesonide to the target site. The multistage systems of S1MP and BNP were further evaluated in three-dimensional (3D) in vitro model of IBD and were found to (1) increase accumulation of BNP in the inflamed areas, (2) restore the barrier function of Caco-2 inflamed monolayer, and (3) significantly reduce pro-inflammatory cytokine release almost to the level of the healthy control.

Budesonide Loaded PLGA Nanoparticles for Targeting the Inflamed Intestinal Mucosa--Pharmaceutical Characterization and Fluorescence Imaging.

PURPOSE: The purpose of this study was to evaluate the specifically targeted efficiency of budesonide loaded PLGA nanoparticles for the treatment of inflammatory bowel disease (IBD). METHODS: The nanoparticles were prepared by an oil/water (O/W) emulsion evaporation technique. The nanoparticles were characterized for their size, shape and in vitro drug release profile. Solid state characterization was carried out by differential scanning calorimetry (DSC) and X-ray Power diffraction (XPRD). In order to evaluate the targeted efficiency of nanoparticles, a particle localization study in the healthy and in the inflamed colon was determined in vivo. These data were complemented by cryo-sections. RESULTS: Nanoparticles were 200 ± 05 nm in size with a smooth and spherical shape. The encapsulation efficiency was around 85 ± 3.5%, which was find-out by both, direct and indirect methods. Release of budesonide from the nanoparticles showed a biphasic release profile with an initial burst followed by sustained release. XPRD data revealed that the drug in the polymer matrix existed in crystalline state. Nanoparticles accumulation in inflamed tissues was evaluated by in-vivo imaging system and it was found that particles are accumulated in abundance at the site of inflammation when compared to the healthy group. CONCLUSION: The study demonstrates that the budesonide loaded PLGA nanoparticles are an efficient delivery system for targeted drug delivery to the inflamed intestinal mucosa.

A 3D co-culture of three human cell lines to model the inflamed intestinal mucosa for safety testing of nanomaterials.

Oral exposure to nanomaterials is a current concern, asking for innovative biological test systems to assess their safety, especially also in conditions of inflammatory disorders. Aim of this study was to develop a 3D intestinal model, consisting of Caco-2 cells and two human immune cell lines, suitable to assess nanomaterial toxicity, in either healthy or diseased conditions. Human macrophages (THP-1) and human dendritic cells (MUTZ-3) were embedded in a collagen scaffold and seeded on the apical side of transwell inserts. Caco-2 cells were seeded on top of this layer, forming a 3D model of the intestinal mucosa. Toxicity of engineered nanoparticles (NM101 TiO2, NM300 Ag, Au) was evaluated in non-inflamed and inflamed co-cultures, and also compared to non-inflamed Caco-2 monocultures. Inflammation was elicited by IL-1ß, and interactions with engineered NPs were addressed by different endpoints. The 3D co-culture showed well preserved ultrastructure and significant barrier properties. Ag NPs were found to be more toxic than TiO2 or Au NPs. But once inflamed with IL-1ß, the co-cultures released higher amounts of IL-8 compared to Caco-2 monocultures. However, the cytotoxicity of Ag NPs was higher in Caco-2 monocultures than in 3D co-cultures. The naturally higher IL-8 production in the co-cultures was enhanced even further by the Ag NPs. This study shows that it is possible to mimic inflamed conditions in a 3D co-culture model of the intestinal mucosa. The fact that it is based on three easily available human cell lines makes this model valuable to study the safety of nanomaterials in the context of inflammation.

A Design of Experiment Study of Nanoprecipitation and Nano Spray Drying as Processes to Prepare PLGA Nano- and Microparticles with Defined Sizes and Size Distributions.

PURPOSE: Aim of this study was to explore the potential of a design of experiments approach to nanoprecipitation (NPR) and nano spray drying (NSD) as processes for preparing poly (lactic-co-glycolic acid, PLGA) nano- and microparticles. In particular, we determined the feasible size range, critical factors influencing particle size, size distribution or yield, and the robustness towards variations of the batch size. METHODS: A fractional factorial design for response surface was applied to study the influence on continuous, categorical and discrete factors. RESULTS: NPR yielded nanoparticles (150-200 nm) with narrow size distribution (PDI < 0.15). Polymer concentration was the main factor in this process, which was found to be very robust to varying the batch size (0.625-50.0 ml). In contrast, NSD yielded microparticles (2-163 µm). The latter process appeared, however, to be influenced by various factors and, therefore, more difficult to control and less robust towards varying the batch size (5-40 ml). By a factorial design approach to NPR, we succeeded to derive an equation, which allowed the prediction of several optimal formulations with defined particle sizes and distributions. CONCLUSION: DOE can help to understand innovative manufacturing processes for nano- and microparticulate drug delivery systems, as well as to optimize these processes regarding particle size, size distribution and yield. Such understanding of these processes is instrumental for their subsequent scale up and quality control as needed for preclinical and clinical test batches.

Utility of models of the gastrointestinal tract for assessment of the digestion and absorption of engineered nanomaterials released from food matrices.

Engineered metal/mineral, lipid and biochemical macromolecule nanomaterials (NMs) have potential applications in food. Methodologies for the assessment of NM digestion and bioavailability in the gastrointestinal tract are nascent and require refinement. A working group was tasked by the International Life Sciences Institute NanoRelease Food Additive project to review existing models of the gastrointestinal tract in health and disease, and the utility of these models for the assessment of the uptake of NMs intended for food. Gastrointestinal digestion and absorption could be addressed in a tiered approach using in silico computational models, in vitro non-cellular fluid systems and in vitro cell culture models, after which the necessity of ex vivo organ culture and in vivo animal studies can be considered. Examples of NM quantification in gastrointestinal tract fluids and tissues are emerging; however, few standardized analytical techniques are available. Coupling of these techniques to gastrointestinal models, along with further standardization, will further strengthen methodologies for risk assessment.

PBTK modelling platforms and parameter estimation tools to enable animal-free risk assessment: recommendations from a joint EPAA--EURL ECVAM ADME workshop.

Information on toxicokinetics is critical for animal-free human risk assessment. Human external exposure must be translated into human tissue doses and compared with in vitro actual cell exposure associated to effects (in vitro-in vivo comparison). Data on absorption, distribution, metabolism and excretion in humans (ADME) could be generated using in vitro and QSAR tools. Physiologically-based toxicokinetic (PBTK) computer modelling could serve to integrate disparate in vitro and in silico findings. However, there are only few freely-available PBTK platforms currently available. And although some ADME parameters can be reasonably estimated in vitro or in silico, important gaps exist. Examples include unknown or limited applicability domains and lack of (high-throughput) tools to measure penetration of barriers, partitioning between blood and tissues and metabolic clearance. This paper is based on a joint EPAA--EURL ECVAM expert meeting. It provides a state-of-the-art overview of the availability of PBTK platforms as well as the in vitro and in silico methods to parameterise basic (Tier 1) PBTK models. Five high-priority issues are presented that provide the prerequisites for wider use of non-animal based PBTK modelling for animal-free chemical risk assessment.

Crossing biological barriers for advanced drug delivery.

This special issue compiles invited and contributed papers of the 9th International Conference and Workshop "Biological Barriers", 29 February-9 March 2012 at Saarland University, Saarbrücken Germany.

Nano- and microscaled particles for drug targeting to inflamed intestinal mucosa: a first in vivo study in human patients.

Most of the drugs used in the treatment of inflammatory bowel disease (IBD) become systemically bioavailable and potentially bear strong adverse effects. Targeting the inflamed areas of the intestine and keeping the drug localised at its site of action can reduce adverse effects. In animal studies, luminal uptake into inflamed mucosal areas has been shown to be size dependent. We investigated the potential of nano- and microparticle uptake into the rectal mucosa of human IBD patients. Fluorescently labelled placebo nanoparticles (NP) 250nm in size and microparticles (MP) 3.0µm in size were prepared. 2h after rectal application to patients with Crohn's disease (CD) or ulcerative colitis (UC), confocal laser endomicroscopy was performed to visualise the particles in inflamed mucosal areas. In biopsies, ex vivo mucosal transport processes were investigated in miniaturised Ussing chambers. We examined 33 patients with IBD (19 patients with CD, 14 patients with UC) and 6 healthy controls. A significantly enhanced accumulation of MP in ulcerous lesions was observed (covered area=1.28% (range 0.83%-3.45%) vs. 0% in controls; p=0.011), while NP were visible only in traces on mucosal surfaces of all patients. The Ussing chamber experiments suggest persorption of particles through cellular voids; statistical significance was only reached for NP. Drug-containing particles may have great potential to more specifically target intestinal lesions to maximise therapeutic efficacy and minimise potential side effects. Nanoparticles may not be required for local drug delivery to intestinal lesions in humans, thereby minimising the risk of unintended translocation into the blood system.

Screening of budesonide nanoformulations for treatment of inflammatory bowel disease in an inflamed 3D cell-culture model.

Drug formulation screenings for treatment of inflammatory bowel disease (IBD) are mostly conducted in chemically induced rodent models that represent acute injury-caused inflammation instead of a chronic condition. To accurately screen drug formulations for chronic IBD, a relevant model that mimics the chronic condition in vitro is urgently needed. In an effort to reduce and potentially replace this scientifically and ethically questionable animal testing for IBD drugs, our laboratory has developed an in vitro model for the inflamed intestinal mucosa observed in chronic IBD, which allows high-throughput screening of anti-inflammatory drugs and their formulations. The in vitro model consists of intestinal epithelial cells, human blood-derived macrophages, and dendritic cells that are stimulated by the inflammatory cytokine interleukin-1ß. In this study, the model was utilized for evaluation of the efficacy and deposition of budesonide, an anti-inflammatory drug, in three different pharmaceutical formulations: (1) a free drug solution, (2) encapsulated into PLGA nanoparticles, and (3) encapsulated into liposomes. The in vitro model of the inflamed intestinal mucosa demonstrated its ability to differentiate therapeutic efficacy among the formulations while maintaining the convenience of conventional in vitro studies and adequately representing the complex pathophysiological changes observed in vivo.

Nano- and microparticulate drug carriers for targeting of the inflamed intestinal mucosa.

Conventional treatment of inflammatory bowel disease (IBD) is based on the daily administration of high doses of immune-suppressant or anti-inflammatory drugs, often complicated by serious adverse effects. Thus, a carrier system that delivers the drug specifically to the inflamed intestinal regions and shows prolonged drug release would be desirable. The advent of TNF-α antibodies and other biopharmaceuticals as potent and specific immune modulators in recent years has broadened the treatment options in IBD, but further increases the necessity for adequate drug delivery, as integrity and bioactivity of the biological active have to be ensured. Exploiting the pathophysiological idiosyncrasies of IBD such as increased mucus production, changes in the structure of the intestinal epithelium and invasion of activated macrophages, different colloidal drug carrier systems have been designed to passively or actively target the site of inflammation. This review introduces different micro- or nanoparticulate drug delivery systems for oral application in IBD therapy for the delivery of small molecular compounds and next generation therapeutics from the group of biological (i.e. peptide and nucleotide based) drugs.

Soluplus® as an effective absorption enhancer of poorly soluble drugs in vitro and in vivo.

As many new active pharmaceutical ingredients are poorly water soluble, solubility enhancers are one possibility to overcome the hurdles of drug dissolution and absorption in oral drug delivery. In the present work a novel solubility enhancing excipient (Soluplus®) was tested for its capability to improve intestinal drug absorption. BCS class II compounds danazol, fenofibrate and itraconazole were tested both in vivo in beagle dogs and in vitro in transport experiments across Caco-2 cell monolayers. Each drug was applied as pure crystalline substance, in a physical mixture with Soluplus®, and as solid solution of the drug in the excipient. In the animal studies a many fold increase in plasma AUC was observed for the solid solutions of drug in Soluplus® compared to the respective pure drug. An effect of Soluplus® in a physical mixture with the drug could be detected for fenofibrate. In vitro transport studies confirm the strong effect of Soluplus® on the absorption behavior of the three tested drugs. Furthermore, the increase of drug flux across Caco-2 monolayer is correlating to the increase in plasma AUC and C(max)in vivo. For these poorly soluble substances Soluplus® has a strong potential to improve oral bioavailability. The applicability of Caco-2 monolayers as tool for predicting the in vivo transport behavior of the model drugs in combination with a solubility enhancing excipient was shown. Also the improvement of a solid dispersion compared to physical mixtures of the drugs and the excipient was correctly reflected by Caco-2 experiments. In the case of fenofibrate the possible improvement by a physical mixture was demonstrated, underscoring the value of the used tool as alternative to animal studies.

A three-dimensional coculture of enterocytes, monocytes and dendritic cells to model inflamed intestinal mucosa in vitro.

While epithelial cell culture models (e.g., Caco-2 cell line) are widely used to assess the absorption of drug molecules across healthy intestinal mucosa, there are no suitable in vitro models of the intestinal barrier in the state of inflammation. Thus development of novel drugs and formulations for the treatment of inflammatory bowel disease is largely bound to animal models. We here report on the development of a complex in vitro model of the inflamed intestinal mucosa, starting with the selection of suitable enterocyte cell line and proinflammatory stimulus and progressing to the setup and characterization of a three-dimensional coculture of human intestinal epithelial cells and immunocompetent macrophages and dendritic cells. In the 3D setup, controlled inflammation can be induced allowing the mimicking of pathophysiological changes occurring in vivo in the inflamed intestine. Different combinations of proinflammatory stimuli (lipopolysaccharides from Escherichia coli and Salmonella typhimurium, interleukin-1ß, interferon-γ) and intestinal epithelial cell lines (Caco-2, HT-29, T84) were evaluated, and only Caco-2 cells were responsive to stimulation, with interleukin-1ß being the strongest stimulator. Caco-2 cells responded to the proinflammatory stimulus with a moderate upregulation of proinflammatory markers and a slight, but significant, decrease (20%) of transepithelial electrical resistance (TEER) indicating changes in the epithelial barrier properties. Setting up the coculture model, macrophages and dendritic cells derived from periphery blood monocytes were embedded in a collagen layer on a Transwell filter insert and Caco-2 cells were seeded atop. Even in the presence of immunocompetent cells Caco-2 cells formed a tight monolayer. Addition of IL-1ß increased inflammatory cytokine response more strongly compared to Caco-2 single culture and stimulated immunocompetent cells proved to be highly active in sampling apically applied nanoparticles. Thus the 3D coculture provides additional complexity and information compared to the stimulated single cell model. The coculture system may serve as a valuable tool for developing drugs and formulations for the treatment of inflammatory bowel diseases, as well as for studying the interaction of xenobiotics and nanoparticles with the intestinal epithelial barrier in the state of inflammation.

Vitamin E TPGS P-glycoprotein inhibition mechanism: influence on conformational flexibility, intracellular ATP levels, and role of time and site of access.

Previous work conducted in our laboratories established the notion that TPGS 1000 (d-alpha-tocopheryl polyethylene glycol 1000 succinate), a nonionic surfactant, modulates P-glycoprotein (P-gp) efflux transport via P-gp ATPase inhibition. The current in vitro research using Caco-2 cells was conducted to further explore the P-gp ATPase inhibition mechanism. Using a monoclonal CD243 P-gp antibody shift assay (UIC2), we probed P-gp conformational changes induced via TPGS 1000. In the presence of TPGS 1000, UIC2 binding was slightly decreased. TPGS 1000 does not appear to be a P-gp substrate, nor does it function as a competitive inhibitor in P-gp substrate efflux transport. The reduction in UIC2 binding with TPGS 1000 was markedly weaker than with orthovanadate, data ruling out trapping P-gp in a transition state by direct interaction with one or both of the P-gp ATP nucleotide binding domains. An intracellular ATP depletion mechanism could be ruled out in the UIC2 assay, and by monitoring intracellular ATP levels in the presence of TPGS 1000. Indicating slow distribution of TPGS 1000 into the membrane, and in agreement with an intramembranal or intracellular side of action, Caco-2 cell monolayer experiments preincubated with TPGS 1000 produce stronger substrate inhibitory activity than those conducted by direct substrate and surfactant coapplication.

Mechanism of inhibition of P-glycoprotein mediated efflux by vitamin E TPGS: influence on ATPase activity and membrane fluidity.

Efflux pump (e.g., P-gp, MRP1, and BCRP) inhibition has been recognized as a strategy to overcome multi-drug resistance and improve drug bioavailability. Besides small-molecule inhibitors, surfactants such as Tween 80, Cremophor EL, several Pluronics, and Vitamin E TPGS (TPGS 1000) are known to modulate efflux pump activity. Competitive inhibition of substrate binding, alteration of membrane fluidity, and inhibition of efflux pump ATPase have been proposed as possible mechanisms. Focusing on TPGS 1000, the aim of our study was to unravel the inhibitory mechanism by comparing the results of inhibition experiments in a Caco-2 transport assay with data from electron spin resonance (ESR) and from ATPase activity studies. ESR results, on Caco-2 cells using 5-doxyl stearic acid (5-SA) as a spin probe, ruled out cell membrane fluidization as a major contributor; change of membrane fluidity was only observed at surfactant concentrations 100 times higher than those needed to achieve full efflux inhibition. Concurrently, TPGS 1000 inhibited substrate induced ATPase activity without inducing significant ATPase activity on its own. By investigating TPGS analogues that varied by their PEG chain length, and/or possessed a modified hydrophobic core, transport studies revealed that modulation of ATPase activity correlated with inhibitory potential for P-gp mediated efflux. Hence, these results indicate that ATPase inhibition is an essential factor in the inhibitory mechanism of TPGS 1000 on cellular efflux pumps.

Influence of vitamin E TPGS poly(ethylene glycol) chain length on apical efflux transporters in Caco-2 cell monolayers.

D-alpha-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS 1000) is a widely used form of vitamin E. TPGS 1000 is comprised of a hydrophilic polar (water-soluble) head and a lipophilic (water-insoluble) alkyl tail. TPGS 1000 has been used as a solubilizer, an emulsifier and as a vehicle for lipid-based drug delivery formulations. Most recently, TPGS 1000 has been recognized as an effective oral absorption enhancer. An enhancing effect is consistent with a surfactant-induced inhibition of P-glycoprotein (P-gp), and perhaps other drug transporter proteins; however, the exact inhibition mechanism(s) remain unclear. Therefore, in an attempt to generate additional knowledge, we have synthesized and tested various TPGS analogs containing different PEG chain length (TPGS 200/238/400/600/1000/2000/3400/3500/4000/6000). These results demonstrate a relationship between TPGS PEG chain length and influence on rhodamine 123 (RHO) transport in Caco-2 monolayers, a relationship which may be illustrated using a Weibull distribution.

Towards an in vitro model of cystic fibrosis small airway epithelium: characterisation of the human bronchial epithelial cell line CFBE41o-.

The CFBE41o- cell line was generated by transformation of cystic fibrosis (CF) tracheo-bronchial cells with SV40 and has been reported to be homozygous for the DeltaF508 mutation. A systematic characterisation of these cells, which however, is a pre-requisite for their use as an in vitro model, has not been undertaken so far. Here, we report an assessment of optimal culture conditions, the expression pattern of drug-transport-related proteins and the stability/presence of the CF transmembrane conductance regulator (CFTR) mutation in the gene and gene product over multiple passages. The CFBE41o- cell line was also compared with a wild-type airway epithelial cell line, 16HBE14o-, which served as model for bronchial epithelial cells in situ. The CFBE41o- cell line retains at least some aspects of human CF bronchial epithelial cells, such as the ability to form electrically tight cell layers with functional cell-cell contacts, when grown under immersed (but not air-interfaced) culture conditions. The cell line is homozygous for DeltaF508-CFTR over multiple passages in culture and expresses a number of proteins relevant for pulmonary drug absorption (e.g. P-gp, LRP and caveolin-1). Hence, the CFBE41o- cell line should be useful for studies of CF gene transfer or alternative treatment with small drug molecules and for the gathering of further information about the disease at the cellular level, without the need for primary culture.