Tiny, Touch-Based Sensor Could Help Patients Stay on Top of Their Medications

Lithium can lessen the signs and symptoms of bipolar illness and depression when used at the proper dosage. Amounts that are either too little or too much can have harmful effects. Invasive blood tests are necessary for patients to accurately track the concentration of this medicine in their bodies. Today, however, scientists announce the creation of a tiny sensor that can in just 30 seconds detect lithium levels from perspiration on the surface of a fingertip. It saves time and eliminates the need to visit the clinic.                                                                                        

Last week, the researchers presented their findings at the American Chemical Society's fall meeting (ACS). Nearly 11,000 talks covering a wide range of science topics were presented at ACS Fall 2022.

Lithium must be taken at a certain dosage, and patients frequently struggle to take medication exactly as directed. They may even forget to take their pills. This means that medical professionals need to be aware of how much medication the patient is actually taking when the medication doesn't seem to be working. The monitoring options available today, however, have several serious shortcomings. For instance, blood tests are intrusive and time-consuming, but they yield accurate findings. In contrast, pill counters don't actually track how much medication is consumed. The research team looked at another bodily fluid to get around these restrictions.

The human body constantly produces perspiration, albeit often in very little amounts, according to Shuyu Lin, Ph.D. Jialun Zhu, a graduate student, and Lin, a postgraduate research student, co-presented the findings at the meeting. "That perspiration contains tiny drug-derived compounds, including lithium. We saw this as a chance to create a brand-new kind of sensor that could find these chemicals.

Sam Emaminejad, Ph.D., the project's lead researcher and a professor at the University of California, Los Angeles, claims that the new device may acquire clinically useful molecular-level data about what is circulating in the body with just a single touch (UCLA). "We already use a lot of touch-based technology in our daily lives, like cellphones and keyboards, so this sensor might fit right in."

However, there were certain technical difficulties in developing a sensor to detect lithium. Small amounts of sweat are usually present, but the aqueous, or watery, environment was necessary for the electrochemical sensitivity required to identify charged particles of lithium. The researchers created a glycerol-containing water-based gel to deliver it. This additional component kept the gel from drying up and created a regulated environment for the sensor's electronic components.

After the lithium ions had passed through the gel, the scientists utilized an ion-selective electrode to capture them. Ion accumulation causes an electrical potential differential when compared to a reference electrode. The difference allowed the researchers to calculate the amount of lithium in sweat. Together, these parts form a tiny, rectangular sensor that can detect lithium in about 30 seconds and is no larger than the head of a thumbtack. The study team hopes to eventually integrate the sensor into a bigger, yet-to-be-designed system that gives the patient or provider visual input, even if it is still in the preliminary testing stage.

The sensor was first described using a synthetic fingertip, and then real people—including one who was receiving lithium treatment—were enlisted to test it. Prior to and following the medication's administration, the team measured this person's lithium levels. They found that these readings were fairly close to those obtained from saliva, which previous studies have demonstrated to detect lithium levels precisely. The scientists intend to investigate how lotion and other skin care items affect the data from the sensor in the future.

There are uses for this technology that go beyond lithium. Emaminejad is studying the possibility of detecting additional chemicals while creating similar touch-based sensors to monitor alcohol and acetaminophen, a painkiller also known by the brand name Tylenol®. A robotic distribution system that only distributes medication when the patient has a low level in their bloodstream, or, for medications that are frequently abused, encryption protected by a fingerprint, might be included in the full sensing systems.

The National Science Foundation, the Brain and Behavior Foundation, Precise Advanced Technologies and Health Systems for Underserved Populations, and the UCLA Henry Samueli School of Engineering and Applied Sciences have all provided money and assistance to the research team.

Lithium monitoring via touch that is non-invasive and based on an organohydrogel sensing interface

One of the most frequently prescribed psychiatric drugs for people with bipolar disorder is lithium salt. It requires constant monitoring to maximize treatment efficacy due to its small therapeutic window (0.6 - 1.2 mM) and significant nonadherence rate ( 40%). Standard lithium monitoring procedures for precise dose are restricted to centralized hospitals and include intrusive blood sampling and expensive, time-consuming lab analyses. Additionally, there is currently no direct monitoring solution for lithium adherence available, and indirect monitoring methods (such as pill counters) are unable to confirm the actual consumption event (inherently non-specific).

Here, we created a touch-based non-invasive lithium monitoring technology to get over these restrictions and control lithium medication on a decentralized basis. This method relies on a hydrogel-coated sensing surface that gathers and analyzes (in-situ) the flux of circulating lithium molecules that partition onto hands. A thin organohydrogel-coated lithium ion-selective electrode (TOH-ISE) was used to create this interface, and the TOH coating was specifically designed to provide stabilized conditions for sensing. In specifically, the gel was given an anti-dehydration characteristic (negligible weight loss for > 2 weeks of storage in an ambient setting) by utilizing a water-glycerol bi-solvent matrix, overcoming the dehydration difficulty of previously-reported hydrogel-based interfaces. Additionally, the TOH coating functions as a controlled microenvironment to condition the ISE in-situ in the proposed interface configuration, minimizing ISE signal drift (a key challenge prohibiting the translation of ISEs in real-life applications).

The created touch-based sensing interface was tested on a patient who had been prescribed a lithium-based medication to demonstrate the clinical applicability of our technology. The elevation of the circulating drug levels following the medication ingestion was successfully captured. Overall, our first findings show that our touch-based approach is appropriate for managing lithium-based pharmacotherapy and for monitoring adherence to prescribed doses of lithium.

                                                                                                                    By AMERICAN CHEMICAL SOCIETY