Fluorescence Spectroscopy for Gut Permeability Assessment

Study Purpose

This research aims to develop portable devices

  • - known as fluorescence spectrometers - to monitor the leakage of fluorescent dyes out of the gut into the blood stream.
These devices will measure the leakiness (permeability) of the gut in a non-invasive manner and will provide an early warning that patients are at risk of infections caused by the unwanted flow of bacteria from the intestine to the rest of the body.

Recruitment Criteria

Accepts Healthy Volunteers

Healthy volunteers are participants who do not have a disease or condition, or related conditions or symptoms

Study Type

An interventional clinical study is where participants are assigned to receive one or more interventions (or no intervention) so that researchers can evaluate the effects of the interventions on biomedical or health-related outcomes.

An observational clinical study is where participants identified as belonging to study groups are assessed for biomedical or health outcomes.

Searching Both is inclusive of interventional and observational studies.

Eligible Ages 18 Years and Over
Gender All
More Inclusion & Exclusion Criteria

Inclusion Criteria:

  • - Ability to give informed consent.
  • - Aged 18 years or above.
  • - No evidence of prior adverse reactions to fluorescein, ICG, dextran or PEG.
  • - No evidence of prior adverse reactions to iodine (for ICG experiments only) - For healthy volunteers: healthy with no active GI/liver disease (or other condition in which increased gut permeability is expected, e.g. HIV) and no antibiotics taken within the previous four weeks.
  • - For cases: exhibiting symptoms of GI, liver or other diseases (e.g. HIV) in which increased intestinal permeability is expected.
  • - For ophthalmology patients recruited in Stage 1: healthy (i.e. as described above for healthy volunteers) and prescribed to have an ophthalmic angiography with an intravenous injection of either fluorescein or ICG.

Exclusion Criteria:

  • - Unable to give informed consent.
  • - Aged <18 years.
  • - Previous adverse reaction to fluorescein, ICG, dextran or PEG.
- Known allergy to iodine (for ICG experiments only) - Pregnancy (in Stage 1 this will be at the discretion of the patient's ophthalmologist) - Breastfeeding (in Stage 1 this will be at the discretion of the ophthalmologist)

Trial Details

Trial ID:

This trial id was obtained from ClinicalTrials.gov, a service of the U.S. National Institutes of Health, providing information on publicly and privately supported clinical studies of human participants with locations in all 50 States and in 196 countries.


Phase 1: Studies that emphasize safety and how the drug is metabolized and excreted in humans.

Phase 2: Studies that gather preliminary data on effectiveness (whether the drug works in people who have a certain disease or condition) and additional safety data.

Phase 3: Studies that gather more information about safety and effectiveness by studying different populations and different dosages and by using the drug in combination with other drugs.

Phase 4: Studies occurring after FDA has approved a drug for marketing, efficacy, or optimal use.

Lead Sponsor

The sponsor is the organization or person who oversees the clinical study and is responsible for analyzing the study data.

Imperial College London
Principal Investigator

The person who is responsible for the scientific and technical direction of the entire clinical study.

Alex J Thompson, PhD
Principal Investigator Affiliation Imperial College London
Agency Class

Category of organization(s) involved as sponsor (and collaborator) supporting the trial.

Overall Status Recruiting
Countries United Kingdom

The disease, disorder, syndrome, illness, or injury that is being studied.

Development and Validation of Gut Permeability Sensor, Permeability; Increased, Celiac Disease, Inflammatory Bowel Diseases, Liver Diseases, HIV/AIDS
Additional Details

"Leaky gut"

  • - or, increased permeability of the intestine - involves the leakage of certain intestinal constituents (e.g. endotoxins or even bacteria) from the gut into the rest of the body.
This condition is associated with many widespread diseases including coeliac disease, inflammatory bowel disease, HIV, liver cirrhosis, sepsis and environmental enteric dysfunction (EED). It has a considerable impact on quality of life and, in extreme cases (e.g. sepsis), it can even lead to death. Furthermore, in the developing world (as part of EED), it severely hampers the mental and physical development of young children. Thus, new devices that can help us to learn more about leaky gut and more accurately monitor its effects are urgently needed. In this project, patients will drink a small dose of a fluorescent dye. Then, by shining light on the patients' skin and recording the color and brightness of the light (fluorescence) that comes back, it will be possible to measure the amount of dye that has leaked into the blood (indicating the likelihood that bacteria are escaping from the gut and causing infections). We refer to this as a "Spectroscopic gut permeability test." We will also ask patients to take a traditional permeability test (known as a PEG permeability test) so that we can validate our new sensor. Overall, this research will deliver vital information that will improve our understanding of leaky gut and help guide the development of treatments for the many diseases in which it occurs.

Arms & Interventions


: 1 - Ophthalmology patients

Ophthalmology patients who are receiving an intravenous dose of either fluorescein or indocyanine green (ICG) as part of their routine ophthalmic care (e.g. as part of a fluorescence angiography examination) will be recruited to the first stage of this study. These patients will take part in preliminary studies aimed at determining whether it is possible to detect fluorescein and ICG in the blood using transcutaneous fluorescence measurements.

: 2a - Healthy subjects

Healthy subjects with no known issues of increased gut permeability. These subjects will act as negative controls in all gut permeability studies.

: 2b - Healthy subjects (gastric emptying)

A subset of healthy volunteers will be recruited to take part in experiments to help in understanding the impact of gastric emptying rate as a confounding factor in measurements of gut permeability.

: 3 - Increased permeability

Gastro-intestinal (GI) and non-GI patients who are expected to exhibit increased gut permeability (e.g. patients with celiac disease, inflammatory bowel disease (IBD), liver disease, HIV or another condition in which increased intestinal permeability is common). The more extreme cases in this group will act as positive controls.


Diagnostic Test: - Spectroscopic gut permeability test

The spectroscopic gut permeability test first involves patients receiving an oral dose of one or more fluorescent dyes. A wearable sensor will then be attached to the patients' skin and this will be used to monitor the leakage of the fluorescent dyes from the intestine into the blood stream in a non-invasive manner. In this way, a measure of the permeability of the intestine will be obtained. Note that patients in Group 1 (ophthalmology patients) will not receive oral doses of contrast agents. Instead, the wearable sensor will simply be used to detect the presence of fluorescent dyes that were administered intravenously as part of planned ophthalmic procedures. Complete details of the spectroscopic gut permeability test can be found in the attached protocol.

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International Sites

IMPERIAL COLLEGE Healthcare Trust, London, United Kingdom





London, , W2 1NY

Site Contact

Alexander J Thompson, PhD



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