Extraction of amino acids by reverse iontophoresis in vivo

Epidermal Wearable Biosensors for the Continuous Monitoring of Biomarkers of Chronic Disease in Interstitial Fluid

Healthcare technology has allowed individuals to monitor and track various physiological and biological parameters. With the growing trend of the use of the internet of things and big data, wearable biosensors have shown great potential in gaining access to the human body, and providing additional functionality to analyze physiological and biochemical information, which has led to a better personalized and more efficient healthcare. In this review, we summarize the biomarkers in interstitial fluid, introduce and explain the extraction methods for interstitial fluid, and discuss the application of epidermal wearable biosensors for the continuous monitoring of markers in clinical biology. In addition, the current needs, development prospects and challenges are briefly discussed.

Reverse iontophoresis with the development of flexible electronics: A review

Skin-centric diagnosis techniques, such as epidermal physiological parameter monitoring, have developed rapidly in recent years. The analysis of interstitial fluid (ISF), a body liquid with abundant physiological information, is a promising method to obtain health status because ISF is easily assessed by implanted or percutaneous measurements. Reverse iontophoresis extracts ISF by applying an electric field onto the skin, and it is a promising method to noninvasively obtain ISF, which, in turn, enables noninvasive epidermal physiological parameter monitoring. However, the development of reverse iontophoresis was relatively slow around the 2010s due to the rigidity and low biocompatibility of the applied devices. With the rapid development of flexible electronic technology in recent years, new progress has been made in the field of reverse iontophoresis, especially in the field of blood glucose monitoring and drug monitoring. This review summarizes the recent advances and discusses the challenges and opportunities of reverse iontophoresis.

Reverse Iontophoretic Extraction of Skin Cancer-Related Biomarkers

Non-invasive methods for early diagnosis of skin cancer are highly valued. One possible approach is to monitor relevant biomarkers such as tryptophan (Trp) and kynurenine (Kyn), on the skin surface. The primary aim of this in vitro investigation was, therefore, to examine whether reverse iontophoresis (RI) can enhance the extraction of Trp and Kyn, and to demonstrate how the Trp/Kyn ratio acquired from the skin surface reflects that in the epidermal tissue. The study also explored whether the pH of the receiver medium impacted on extraction efficiency, and assessed the suitability of a bicontinuous cubic liquid crystal as an alternative to a simple buffer solution for this purpose. RI substantially enhanced the extraction of Trp and Kyn, in particular towards the cathode. The Trp/Kyn ratio obtained on the surface matched that in the viable skin. Increasing the receiver solution pH from 4 to 9 improved extraction of both analytes, but did not significantly change the Trp/Kyn ratio. RI extraction of Trp and Kyn into the cubic liquid crystal was comparable to that achieved with simple aqueous receiver solutions. We conclude that RI offers a potential for non-invasive sampling of low-molecular weight biomarkers and further investigations in vivo are therefore warranted.

Organic Bioelectronic Devices for Metabolite Sensing

Electrochemical detection of metabolites is essential for early diagnosis and continuous monitoring of a variety of health conditions. This review focuses on organic electronic material-based metabolite sensors and highlights their potential to tackle critical challenges associated with metabolite detection. We provide an overview of the distinct classes of organic electronic materials and biorecognition units used in metabolite sensors, explain the different detection strategies developed to date, and identify the advantages and drawbacks of each technology. We then benchmark state-of-the-art organic electronic metabolite sensors by categorizing them based on their application area (in vitro, body-interfaced, in vivo, and cell-interfaced). Finally, we share our perspective on using organic bioelectronic materials for metabolite sensing and address the current challenges for the devices and progress to come.

Wearable and flexible electronics for continuous molecular monitoring

Wearable biosensors have received tremendous attention over the past decade owing to their great potential in predictive analytics and treatment toward personalized medicine. Flexible electronics could serve as an ideal platform for personalized wearable devices because of their unique properties such as light weight, low cost, high flexibility and great conformability. Unlike most reported flexible sensors that mainly track physical activities and vital signs, the new generation of wearable and flexible chemical sensors enables real-time, continuous and fast detection of accessible biomarkers from the human body, and allows for the collection of large-scale information about the individual's dynamic health status at the molecular level. In this article, we review and highlight recent advances in wearable and flexible sensors toward continuous and non-invasive molecular analysis in sweat, tears, saliva, interstitial fluid, blood, wound exudate as well as exhaled breath. The flexible platforms, sensing mechanisms, and device and system configurations employed for continuous monitoring are summarized. We also discuss the key challenges and opportunities of the wearable and flexible chemical sensors that lie ahead.

Advances in transdermal insulin delivery

Insulin therapy is necessary to regulate blood glucose levels for people with type 1 diabetes and commonly used in advanced type 2 diabetes. Although subcutaneous insulin administration via hypodermic injection or pump-mediated infusion is the standard route of insulin delivery, it may be associated with pain, needle phobia, and decreased adherence, as well as the risk of infection. Therefore, transdermal insulin delivery has been widely investigated as an attractive alternative to subcutaneous approaches for diabetes management in recent years. Transdermal systems designed to prevent insulin degradation and offer controlled, sustained release of insulin may be desirable for patients and lead to increased adherence and glycemic outcomes. A challenge for transdermal insulin delivery is the inefficient passive insulin absorption through the skin due to the large molecular weight of the protein drug. In this review, we focus on the different transdermal insulin delivery techniques and their respective advantages and limitations, including chemical enhancers-promoted, electrically enhanced, mechanical force-triggered, and microneedle-assisted methods.

Delivery of neostigmine and glycopyrrolate by iontophoresis: a nonrandomized study in individuals with spinal cord injury

STUDY DESIGN

Phase I Clinical Trial.

OBJECTIVES

In this proof-of-principle study, the effectiveness and safety of transdermal administration of neostigmine/glycopyrrolate to elicit a bowel movement was compared to intravenous administration in patients with spinal cord injury.

SETTING

James J. Peters Veterans Affairs Medical Center (Bronx, NY).

METHODS

Individuals were screened for responsiveness (Physical Response) to intravenous neostigmine (0.03 mg/kg)/glycopyrrolate (0.006 mg/kg). Intravenous neostigmine/glycopyrrolate responders (Therapeutic Response) were administered low-dose transdermal neostigmine/glycopyrrolate [(0.05 mg/kg)/(0.01 mg/kg)] by iontophoresis. Non-responders to low-dose transdermal neostigmine/glycopyrrolate were administered high-dose transdermal neostigmine/glycopyrrolate [(0.07 mg/kg)/(0.014 mg/kg)] by iontophoresis. Bowel movement, bowel evacuation time, and cholinergic side effects were recorded. Visits were separated by 2 to 14 days.

RESULTS

Eighteen of 25 individuals (72.0%) had a bowel movement (20 ± 22 min) after intravenous neostigmine/glycopyrrolate. Of these 18 individuals, 5 individuals experienced a bowel movement with low-dose transdermal neostigmine/glycopyrrolate. Another five individuals had a bowel movement after high-dose transdermal neostigmine/glycopyrrolate administration. Fewer side effects were observed in individuals who received neostigmine/glycopyrrolate transdermally compared to those who were administered intravenous neostigmine/glycopyrrolate.

CONCLUSIONS

Transdermal administration of neostigmine/glycopyrrolate by iontophoresis appears to be a practical, safe, and effective approach to induce bowel evacuation in individuals with spinal cord injury.

Reverse Iontophoretic Extraction of Metabolites from Living Plants and their Identification by Ion-chromatography Coupled to High Resolution Mass Spectrometry

INTRODUCTION

The identification and characterisation of cellular metabolites has now become an important strategy to obtain insight into functional plant biology. However, the extraction of metabolites for identification and analysis is challenging and, at the present time, usually requires destruction of the plant.

OBJECTIVE

To detect different plant metabolites in living plants with no pre-treatment using the combination of iontophoresis and ion-chromatography with mass spectrometry detection.

METHODOLOGY

In this work, the simple and non-destructive method of reverse iontophoresis has been used to extract in situ multiple plant metabolites from intact Ocimum basilicum leaves. Subsequently, the analysis of these metabolites has been performed with ion chromatography coupled directly to high resolution mass spectrometric detection (IC-MS).

RESULTS

The application of reverse iontophoresis to living plant samples has avoided the need for complex pre-treatments. With this approach, no less than 24 compounds, including organic acids and sugars as well as adenosine triphosphate (ATP) were successfully detected.

CONCLUSION

The research demonstrates that it is feasible to monitor, therefore, a number of important plant metabolites using a simple, relatively fast and non-destructive approach. Copyright © 2016 John Wiley & Sons, Ltd.

Transdermal reverse iontophoresis: A novel technique for therapeutic drug monitoring

Application of transdermal reverse iontophoresis for diagnostic purpose is a relatively new concept but its short span of research is full of ups and downs. In early nineties, when the idea was floated, it received a dubious welcome by the scientific community. Yet to the disbelief of many, 2001 saw the launching of GlucoWatch® G2 Biographer, the first device that could measure the blood sugar level noninvasively. Unfortunately, the device failed to match the expectation and was withdrawn in 2007. However, the concept stayed on. Research on reverse iontophoresis has diversified in many fields. Numerous in vitro and in vivo experiments confirmed the prospect of reverse iontophoresis as a noninvasive tool in therapeutic drug monitoring and clinical chemistry. This review provides an overview about the recent developments in reverse iontophoresis in the field of therapeutic drug monitoring.

Transdermal iontophoretic drug delivery: advances and challenges

The stratum corneum continues to pose considerable impediment to transdermal drug delivery. One of the effective ways of circumventing this challenge is through the use of iontophoresis. Iontophoresis uses low-level current to drive charged compounds across the skin. This review discusses progress made in the field of iontophoretic transport of small and large molecules. The major obstacles are also touched upon and advances made in the last few decades described. A number of iontophoretic systems approved for clinical use by regulatory authorities is also discussed.

Amikacin reverse iontophoresis: optimization of in vitro extraction

The aim of this work was to optimize amikacin reverse iontophoretic extraction across the skin in vitro, for non-invasive drug monitoring. Reverse iontophoresis experiments were performed using vertical diffusion cells. The lower chamber, simulating body fluids, contained amikacin bisulphate and acetaminophen, as marker for electroosmosis, while the upper chamber was filled with the appropriate extraction solution. The effect of concentration of amikacin in the dermal bathing solution and the effect of extraction solution composition and pH were studied. The results show that the extraction of amikacin was independent of pH and always in the anode-to-cathode direction, in agreement with the positive charge of the drug. The presence of amikacin in the bathing solution did not modify acetaminophen extraction at pH 4.0, while the extraction was reduced at pH 8.0. In conclusion, amikacin can be extracted across the skin in vitro by reverse iontophoresis. Owing to the charge of the molecule, extraction takes place at the cathode. Using acetaminophen as neutral marker, it was shown that amikacin can interact with the skin and alter its permselectivity at pH 8.0.