Transdermal fluorescence detection of a dual fluorophore system for noninvasive point-of-care gastrointestinal permeability measurement

Acoustic percolation switches enable targeted drug delivery controlled by diagnostic ultrasound

Delivering biomedicines to specific sites of disease using remote-controlled devices is a long-standing vision in biomedical research. However, most existing externally triggered delivery systems are based on complex micromachines that are controlled with electromagnetic waves and require custom external instrumentation. Here, we present a drug delivery platform based on a simple protein-containing hydrogel that can be both imaged and triggered to release drugs at specific locations using widely available diagnostic ultrasound devices. This technology is based on the addition of air-filled protein nanostructures called gas vesicles (GVs) to hydrogel delivery vehicles. While intact, GVs sterically block the release of drug payloads and allow the vehicle to be imaged with ultrasound. An increase in ultrasound pressure causes the collapse of GVs within the delivery vehicles at the desired anatomical location, instantly creating percolation channels in the hydrogel, massively increasing diffusivity, and leading to rapid drug release. Unlike previous ultrasound-actuated delivery approaches, both the imaging and release are performed using a simple diagnostic ultrasound probe ubiquitously available in clinical settings. We implement this concept by quantifying ultrasound-controlled drug diffusion and release in vitro and demonstrating image-guided protein delivery in vivo in the gastrointestinal (GI) tract following oral administration. We further validate this technology by using it to deliver anti-inflammatory antibodies to effectively treat a rat model of colitis. Targeted acoustic percolation switches (TAPS) open a conduit for local, image-guided drug delivery with a simple formulation and commonplace ultrasound equipment.

Novel gastrointestinal tools (GI Tools) for evaluating gut functional capacity in adults with environmental enteropathy in Zambia and Zimbabwe: A cross-sectional study protocol

Background

Environmental enteropathy (EE) is a highly prevalent subclinical inflammatory intestinal disorder associated with growth failure, impaired neurocognitive development, poor response to oral vaccines, and micronutrient deficiencies. However, EE research and clinical trials are hampered by the lack of non-invasive tools for measuring intestinal function in detail. This study aims to develop new tools for the measurement of multiple domains of gut functional capacity.

Methods

The GI TOOLS project is a cross-sectional study that will recruit adults aged 18-65 years with EE in Lusaka, Zambia. Each participant will undergo assessment of gut functional capacity using novel near-point-of-care tools and provide multiple samples for detailed laboratory analyses. Participants will also undergo endoscopy for collection of duodenal biopsies. Novel techniques include stable isotopes approaches to measuring digestion, absorption, and bidirectional transmucosal amino acid flux, a non-invasive fluorescence tool for real-time evaluation of gut permeability, and assessment of reverse permeation of intravenous antibiotics to be carried out separately in Zimbabwe. Stool and duodenal microbiome sequencing using MinION sequencing, metabolome analysis applied to plasma and intestinal fluids, blood immune cell phenotyping, in vitro epithelial barrier models, and duodenal immunohistochemistry will also be used to explore EE in depth. These will all be integrated with gold standard histology and mucosal morphometry, alongside lactulose permeation data, and stool and plasma biomarker analysis. The protocol has been approved by ethics committees and regulators in Zambia, Zimbabwe, and the UK. Participants will give informed consent before they can participate.

Anticipated outcomes

Based on this extensive phenotyping, tests will be developed which can be simplified and refined for use in adults and children with EE, and for clinical trials. Findings from this project will be disseminated through in-person meetings with caregivers and regulatory bodies, presentations at conferences and in peer-reviewed journals.

Transcutaneous fluorescence spectroscopy: development and characterization of a compact, portable, and fiber-optic sensor

Significance

The integrity of the intestinal barrier is gaining recognition as a significant contributor to various pathophysiological conditions, including inflammatory bowel disease, celiac disease, environmental enteric dysfunction (EED), and malnutrition. EED, for example, manifests as complex structural and functional changes in the small intestine leading to increased intestinal permeability, inflammation, and reduced absorption of nutrients. Despite the importance of gut function, current techniques to assess intestinal permeability (such as endoscopic biopsies or dual sugar assays) are either highly invasive, unreliable, and/or difficult to perform in certain patient populations (e.g., infants).

Aim

We present a portable, optical sensor based on transcutaneous fluorescence spectroscopy to assess gut function (in particular, intestinal permeability) in a fast and noninvasive manner.

Approach

Participants receive an oral dose of a fluorescent contrast agent, and a wearable fiber-optic probe detects the permeation of the contrast agent from the gut into the blood stream by measuring the fluorescence intensity noninvasively at the fingertip. We characterized the performance of our compact optical sensor by comparing it against an existing benchtop spectroscopic system. In addition, we report results from a human study in healthy volunteers investigating the impact of skin tone and contrast agent dose on transcutaneous fluorescence signals.

Results

The first study with eight healthy participants showed good correlation between our compact sensor and the existing benchtop spectroscopic system [correlation coefficient ( r ) > 0.919 , p < 0.001 ]. Further experiments in 14 healthy participants revealed an approximately linear relationship between the ingested contrast agent dose and the collected signal intensity. Finally, a parallel study on the impact of different skin tones showed no significant differences in signal levels between participants with different skin tones (p > 0.05 ).

Conclusions

In this paper, we demonstrate the potential of our compact transcutaneous fluorescence sensor for noninvasive monitoring of intestinal health.

First-in-Human Assessment of Gut Permeability in Crohn's Disease Patients Using Fluorophore Technology

Background and Aims

The dual sugar absorption test as a classic measure of human intestinal permeability has limited clinical utility due to lengthy and cumbersome urine collection, assay variability, and long turnaround. We aimed to determine if the orally administered fluorophore MB-102 (relmapirazin) (molecular weight [MW] = 372) compares to lactulose (L) (MW = 342) and rhamnose (R) (MW = 164)-based dual sugar absorption test as a measure of gut permeability in people with a spectrum of permeability including those with Crohn's disease (CD).

Methods

We performed a single-center, randomized, open-label, crossover study comparing orally administered MB-102 (1.5 or 3.0 mg/kg) to L (1000 mg) and R (200 mg). Adults with active small bowel CD on magnetic resonance enterography (cases) and healthy adults (controls) were randomized to receive either MB-102 or L and R on study day 1, and the other tracer 3 to 7 days later. Urine was collected at baseline and 1, 2, 4, 6, 8, 10, and 12 hours after tracer ingestion to calculate the cumulative urinary percent excretion of MB-102 and L and R.

Results

Nine cases and 10 controls completed the study without serious adverse events. Urinary recovery of administered MB-102 correlated with recovery of lactulose (r-squared = 0.83) for all participants. MB-102 urine recovery was also tracked with the L:R ratio urine recovery (r-squared = 0.57). In controls, the percentages of L and MB-102 recovered were similar within a narrow range, unlike in CD patients.

Conclusion

This first-in-human study of an orally administered fluorophore to quantify gastrointestinal permeability in adults with CD demonstrates that MB-102 is well tolerated, and its recovery in urine mirrors that of percent L and the L:R ratio.

Impaired Intestinal Permeability Assessed by Confocal Laser Endomicroscopy-A New Potential Therapeutic Target in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD) represent a global phenomenon, with a continuously rising prevalence. The strategies concerning IBD management are progressing from clinical monitorization to a targeted approach, and current therapies strive to reduce microscopic mucosal inflammation and stimulate repair of the epithelial barrier function. Intestinal permeability has recently been receiving increased attention, as evidence suggests that it could be related to disease activity in IBD. However, most investigations do not successfully provide adequate information regarding the morphological integrity of the intestinal barrier. In this review, we discuss the advantages of confocal laser endomicroscopy (CLE), which allows in vivo visualization of histological abnormalities and targeted optical biopsies in the setting of IBD. Additionally, CLE has been used to assess vascular permeability and epithelial barrier function that could correlate with prolonged clinical remission, increased resection-free survival, and lower hospitalization rates. Moreover, the dynamic evaluation of the functional characteristics of the intestinal barrier presents an advantage over the endoscopic examination as it has the potential to select patients at risk of relapses. Along with mucosal healing, histological or transmural remission, the recovery of the intestinal barrier function emerges as a possible target that could be included in the future therapeutic strategies for IBD.

Non-invasive assessment of intestinal permeability in healthy volunteers using transcutaneous fluorescence spectroscopy

The permeability of the intestinal barrier is altered in a multitude of gastrointestinal conditions such as Crohn's and coeliac disease. However, the clinical utility of gut permeability is currently limited due to a lack of reliable diagnostic tests. To address this issue, we report a novel technique for rapid, non-invasive measurement of gut permeability based on transcutaneous ('through-the-skin') fluorescence spectroscopy. In this approach, participants drink an oral dose of a fluorescent dye (fluorescein) and a fibre-optic fluorescence spectrometer is attached to the finger to detect permeation of the dye from the gut into the blood stream in a non-invasive manner. To validate this technique, clinical trial measurements were performed in 11 healthy participants. First, after 6 h of fasting, participants ingested 500 mg of fluorescein dissolved in 100 ml of water and fluorescence measurements were recorded at the fingertip over the following 3 h. All participants were invited back for a repeat study, this time ingesting the same solution but with 60 g of sugar added (known to transiently increase intestinal permeability). Results from the two study datasets (without and with sugar respectively) were analysed and compared using a number of analysis procedures. This included both manual and automated calculation of a series of parameters designed for assessment of gut permeability. Calculated values were compared using Student's T-tests, which demonstrated significant differences between the two datasets. Thus, transcutaneous fluorescence spectroscopy shows promise in non-invasively discriminating between two differing states of gut permeability, demonstrating potential for future clinical use.

Rapid, non-invasive measurement of gastric emptying rate using transcutaneous fluorescence spectroscopy

Gastric emptying rate (GER) signifies the rate at which the stomach empties following ingestion of a meal and is relevant to a wide range of clinical conditions. GER also represents a rate limiting step in small intestinal absorption and so is widely assessed for research purposes. Despite the clinical and physiological importance of gastric emptying, methods used to measure GER possess a series of limitations (including being invasive, slow or unsuitable for certain patient populations). Here, we present a new technique based on transcutaneous (through-the-skin) fluorescence spectroscopy that is fast, non-invasive, and does not require the collection of samples or laboratory-based analysis. Thus, this approach has the potential to allow immediate reporting of clinical results. Using this new method, participants receive an oral dose of a fluorescent contrast agent and a wearable probe detects the uptake of the agent from the gut into the blood stream. Analysis of the resulting data then permits the calculation of GER. We compared our spectroscopic technique to the paracetamol absorption test (a clinically approved GER test) in a clinical study of 20 participants. Results demonstrated good agreement between the two approaches and, hence, the clear potential of transcutaneous fluorescence spectroscopy for clinical assessment of GER.