Analysis of PEG 400 and 4000 in urine for gut permeability assessment using solid phase extraction and gel permeation chromatography with refractometric detection

Current status of in vivo bioanalysis of nano drug delivery systems

The development of nano drug delivery systems (NDDSs) provides new approaches to fighting against diseases. The NDDSs are specially designed to serve as carriers for the delivery of active pharmaceutical ingredients (APIs) to their target sites, which would certainly extend the benefit of their unique physicochemical characteristics, such as prolonged circulation time, improved targeting and avoiding of drug-resistance. Despite the remarkable progress achieved over the last three decades, the understanding of the relationships between the in vivo pharmacokinetics of NDDSs and their safety profiles is insufficient. Analysis of NDDSs is far more complicated than the monitoring of small molecular drugs in terms of structure, composition and aggregation state, whereby almost all of the conventional techniques are inadequate for accurate profiling their pharmacokinetic behavior in vivo. Herein, the advanced bioanalysis for tracing the in vivo fate of NDDSs is summarized, including liquid chromatography tandem-mass spectrometry (LC-MS/MS), Förster resonance energy transfer (FRET), aggregation-caused quenching (ACQ) fluorophore, aggregation-induced emission (AIE) fluorophores, enzyme-linked immunosorbent assay (ELISA), magnetic resonance imaging (MRI), radiolabeling, fluorescence spectroscopy, laser ablation inductively coupled plasma MS (LA-ICP-MS), and size-exclusion chromatography (SEC). Based on these technologies, a comprehensive survey of monitoring the dynamic changes of NDDSs in structure, composition and existing form in system (i.e. carrier polymers, released and encapsulated drug) with recent progress is provided. We hope that this review will be helpful in appropriate application methodology for investigating the pharmacokinetics and evaluating the efficacy and safety profiles of NDDSs.

Identification of somatostatin receptors using labeled PEGylated octreotide, as an active internalization

Numerous normal and tumors cells are well-known to express the somatostatin receptors (SSTRs) on their surface which makes the receptor be useful for tumor scintigraphy. Thus, the identification of SSTRs is beneficial, especially SSTR₂. The somatostatin analog, Octreotide (OCT), was chosen as a ligand, as it is known to selectively bind to SSTR₂. Moreover, polyethylene glycol (PEG), 8armPEG, was used as a branched PEG to provide a low nonspecific cell binding and easily chemical modification. OCT and fluorescein (Flu) were conjugated to branched PEG using a water-soluble carbodiimide (EDC) and N-hydroxy succinimide (NHS) so as to activate its carboxylic acid group. 8armPEG-tagged Flu and OCT was characterized by gel permeation chromatography (GPC) to proof the conjugation of OCT to 8armPEG. Finally, cellular uptake was studied using pancreatic cancer cells with well-expressed somatostatin receptors using a confocal laser scanning microscope (CLMS) and fluorescence activated cell sorting (FACS). GPC showed increases in molecular mass since it showed a difference in elution time of 8armPEG itself and 8armPEG labeled with Flu. CLMS and FACS showed high binding with the positive SSTR₂ cells expression and showed negative results with negative expressing SSTR₂. These bindings were decreased when the receptors were occupied with free OCT which confirms the specific binding to SSTR₂. Therefore, we formulated a novel model to easily identify SSTR₂ and other receptors which serves as a promising platform for identification of tumor cells overexpressing the SSTR₂, which would be a hopeful target for cancer therapy and tumor scintigraphy.

Analytical method for the determination of polyethylenglycole 400 as marker in porcine plasma

Polyethylenglycole (PEG) is a widespread linear polymer which can be utilized as a solute digestive and intestinal permeability marker in nutritional physiology studies depending on chain length/molecular mass. PEG 400 is proposed to be an ideal permeability marker. Due to its molecular mass (238-590 g/mol) and characteristics, PEG 400 is suggested to be used as a surrogate for studying the paracellular permeability of small hydrophilic molecules. For this purpose, a liquid chromatographic-tandem mass spectrometric method has been developed for the determination of the major oligomers of PEG 400 in porcine plasma. The analysis included a simple and rapid clean-up step where proteins were precipitated. The most intense ions corresponding to seven PEG 400 oligomers were separated within 7 min. Validation of the optimized method was performed in the range of 500-18,000 ng/mL. Mean recoveries between 93 and 105% were achieved using spiked plasma samples in three different concentration levels. The limit of quantification ranged between 11 and 244 ng/mL. The applicability of the method was demonstrated by the analysis of porcine plasma samples obtained from an animal experiment with barrows. The kinetic course of administrated PEG 400 was shown based on the dataset of two barrows selected from the control group, and it was figured out that relative proportion of each PEG oligomer in portal plasma decreased with increasing molecular mass.

Polyethylene glycol versus dual sugar assay for gastrointestinal permeability analysis: is it time to choose?

Background

Increased intestinal permeability is an important measure of disease activity and prognosis. Currently, many permeability tests are available and no consensus has been reached as to which test is most suitable. The aim of this study was to compare urinary probe excretion and accuracy of a polyethylene glycol (PEG) assay and dual sugar assay in a double-blinded crossover study to evaluate probe excretion and the accuracy of both tests.

Methods

Gastrointestinal permeability was measured in nine volunteers using PEG 400, PEG 1500, and PEG 3350 or lactulose-rhamnose. On 4 separate days, permeability was analyzed after oral intake of placebo or indomethacin, a drug known to increase intestinal permeability. Plasma intestinal fatty acid binding protein and calprotectin levels were determined to verify compromised intestinal integrity after indomethacin consumption. Urinary samples were collected at baseline, hourly up to 5 hours after probe intake, and between 5 and 24 hours. Urinary excretion of PEG and sugars was determined using high-pressure liquid chromatography-evaporative light scattering detection and liquid chromatography-mass spectrometry, respectively.

Results

Intake of indomethacin increased plasma intestinal fatty acid-binding protein and calprotectin levels, reflecting loss of intestinal integrity and inflammation. In this state of indomethacin-induced gastrointestinal compromise, urinary excretion of the three PEG probes and lactulose increased compared with placebo. Urinary PEG 400 excretion, the PEG 3350/PEG 400 ratio, and the lactulose/rhamnose ratio could accurately detect indomethacin-induced increases in gastrointestinal permeability, especially within 2 hours of probe intake.

Conclusion

Hourly urinary excretion and diagnostic accuracy of PEG and sugar probes show high concordance for detection of indomethacin-induced increases in gastrointestinal permeability. This comparative study improves our knowledge of permeability analysis in man by providing a clear overview of both tests and demonstrates equivalent performance in the current setting.

The Relationship between Small-Intestinal Bacterial Overgrowth and Intestinal Permeability in Patients with Irritable Bowel Syndrome

BACKGROUND/AIMS

Small-intestinal bacterial overgrowth (SIBO) is a frequent finding in patients with irritable bowel syndrome (IBS). Many patients with IBS also have abnormal intestinal permeability, which is probably due to low-grade inflammation in the intestinal mucosa. Our aim was to verify the relationship between SIBO and small-intestinal permeability in IBS patients.

METHODS

A cohort of 38 IBS patients (20 women and 18 men; age range 16-70 years; mean age 40.2 years) with symptoms that fulfilled Rome-II criteria, and 12 healthy controls (5 women and 7 men; age range 25-52 years; mean age: 37.8 years) were recruited. All subjects underwent lactulose breath tests (LBTs) and intestinal permeability tests using the polyethylene glycol (PEG) 3350/400 retrieval ratio.

RESULTS

A positive LBT was found in 18.4% (7/38) of patients with IBS and 8.3% (1/12) of control subjects. Intestinal permeability was significantly increased in patients with IBS compared with the normal controls (0.82+/-0.09 vs 0.41+/-0.05 [mean+/-SD], respectively; p<0.05). However, the intestinal permeability did not differ significantly between IBS patients with a positive LBT and those with a negative LBT (0.90+/-0.13 and 0.80+/-0.11, respectively; p>0.05).

CONCLUSIONS

Intestinal permeability was increased in patients with IBS, but this finding did not correlated with the occurrence of SIBO.

Increased intestinal macromolecular permeability and urine nitrite excretion associated with liver cirrhosis with ascites

AIM: To determine intestinal permeability, the serum tumor necrosis factor (TNF)-α level and urine nitric oxide (NO) metabolites are altered in liver cirrhosis (LC) with or without ascites.

METHODS: Fifty-three patients with LC and 26 healthy control subjects were enrolled in the study. The intestinal permeability value is expressed as the percentage of polyethylene glycol (PEG) 400 and 3350 retrieval in 8-h urine samples as determined by high performance liquid chromatography. Serum TNF-α concentrations and urine NO metabolites were determined using an enzyme-linked immunosorbent assay (ELISA) and Greiss reaction method, respectively.

RESULTS: The intestinal permeability index was significantly higher in patients with LC with ascites than in healthy control subjects or patients with LC without ascites (0.88 ± 0.12 vs 0.52 ± 0.05 or 0.53 ± 0.03, P < 0.05) and correlated with urine nitrite excretion (r = 0.98). Interestingly, the serum TNF-α concentra-tion was significantly higher in LC without ascites than in control subjects or in LC with ascites (198.9 ± 55.8 pg/mL vs 40.9 ± 12.3 pg/mL or 32.1 ± 13.3 pg/mL, P < 0.05). Urine nitrite excretion was significantly higher in LC with ascites than in the control subjects or in LC without ascites (1170.9 ± 28.7 &mgr;mol/L vs 903.1 ± 55.1 &mgr;mol/L or 956.7 ± 47.7 &mgr;mol/L, P < 0.05).

CONCLUSION: Increased intestinal macromolecular permeability and NO is probably of importance in the pathophysiology and progression of LC with ascites, but the serum TNF-α concentration was not related to LC with ascites.