The mass production of wearable biosensors is made possible by the use of printable molecule-selective nanoparticles

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To make this possible, physicians first need a way to continuously measure and monitor certain biomarkers of health.
To that end, a team of Caltech engineers has developed a technique for inkjet printing arrays of special nanoparticles that enables the mass production of long-lasting wearable sweat sensors.
Wearable biosensors that incorporate the new nanoparticles have been successfully used to monitor metabolites in patients suffering from long COVID and the levels of chemotherapy drugs in cancer patients at City of Hope in Duarte, California.
Gao and his team describe the nanoparticles as core–shell cubic nanoparticles.
All of the nanoparticles were combined into one sensor that was then mass produced.

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The ability to tailor medical care to each patient’s unique needs and then provide the ideal combination of nutrients, metabolites, and medications, if required, to stabilize and improve their condition may very well be the way of the future. Doctors must first find a method to measure and track specific health biomarkers on an ongoing basis in order to accomplish this.

To achieve this, a group of Caltech engineers has created a method for inkjet printing arrays of unique nanoparticles, which makes it possible to produce durable wearable sweat sensors in large quantities. In order to give patients and their doctors the ability to continuously track changes in the levels of various biomarkers, including vitamins, hormones, metabolites, and medications, these sensors could be used to monitor those molecules in real time.

At City of Hope in Duarte, California, wearable biosensors that use the new nanoparticles have been effectively used to track the levels of chemotherapy medications in cancer patients as well as metabolites in patients with prolonged COVID.

“These are just two examples of what is possible,” says Wei Gao, a medical engineering professor at Caltech’s Andrew and Peggy Cherng Department of Medical Engineering.

Gao, the corresponding author on a paper in the journal Nature Materials outlining the new method, says, “These sensors now give us the possibility to monitor continuously and noninvasively a number of chronic conditions and their biomarkers.”.

The nanoparticles are characterized by Gao and his colleagues as core-shell cubic nanoparticles. The researchers create the cubes in a solution containing the molecule they wish to monitor, like vitamin C. The target molecule, vitamin C, is trapped inside the cubic nanoparticles as the monomers spontaneously come together to form a polymer.

A molecularly imprinted polymer shell with holes that precisely match the shapes of the vitamin C molecules is then left behind after the vitamin C molecules are specifically removed using a solvent. This process is similar to artificial antibodies that only recognize specific molecules’ shapes.

Crucially, the scientists fuse those unique polymers with a nickel hexacyanoferrate (NiHCF) nanoparticle core in the new study. Contact with perspiration or other bodily fluids can cause this material to oxidize or reduce when an electrical voltage is applied.

Using the vitamin C example once more, an electrical signal will be produced when fluid comes into contact with the NiHCF core as long as the holes shaped like vitamin C are empty.

Nevertheless, when vitamin C molecules come into contact with the polymer, they slide into those holes, preventing the core from coming into contact with perspiration or other body fluids. The electrical signal becomes weaker as a result. Thus, the electrical signal’s strength indicates the exact amount of vitamin C present.

“This core is crucial. “These sensors are perfect for long-term measurement because of the nickel hexacyanoferrate core’s high stability, even in biological fluids,” says Gao, a Ronald and JoAnne Willens Scholar and an Investigator at the Heritage Medical Research Institute.

The new core-shell nanoparticles are very adaptable and are used to print sensor arrays that use multiple nanoparticle “inks” in a single array to measure the levels of various amino acids, metabolites, hormones, or drugs in sweat or body fluids.

For instance, the researchers printed out vitamin C-binding nanoparticles in addition to other nanoparticles that bind to the amino acid tryptophan and creatinine, a biomarker that is frequently used to assess kidney function.

The sensor was created by combining all of the nanoparticles and then mass-producing it. Research on patients with protracted COVID is of interest because of these three molecules.

Likewise, the scientists created wearable sensors based on nanoparticles that were unique to three antitumor medications. These sensors were then tested on cancer patients at City of Hope.

Gao claims, “We were able to remotely monitor the amount of cancer drugs in the body at any given time, demonstrating the potential of this technology.”. “This is pointing the way toward the goal of dose personalization for many other conditions in addition to cancer. “..”.

The team also demonstrated in the paper how the nanoparticles can be used to print sensors that can be inserted just beneath the skin to accurately track the body’s drug levels.

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