Contact lens could measure blood glucose

Continuous glucose monitoring helps reduce the risk of diabetes-related health problems. Currently, however, this is usually performed by electrodes inserted under the skin, which can be painful, and may cause skin irritation or infections. Gregory Herman from Oregon State University and colleagues are developing transparent biosensors embedded into contact lenses that could one day allow patients to continuously monitor their blood glucose levels without invasive tests. The biosensing lenses could also potentially be used to track drug use or serve as an early detection system for cancer and other medical conditions. The researchers presented the work at the American Chemical Society National Meeting.

Herman and colleagues developed low-cost methods to make indium gallium zinc oxide (IGZO) electronics. They then fabricated a biosensor containing a transparent sheet of IGZO field-effect transistors and glucose oxidase, an enzyme that breaks down glucose. When they added glucose, the enzyme oxidized the blood sugar, shifting the pH level in the mixture and triggering changes in the electrical current flowing through the IGZO transistor. To increase the biosensor's sensitivity, they created a nanostructured IGZO network that detects glucose at concentrations much lower than found in tears. In theory, says Herman, more than 2500 biosensors could be embedded in a 1 mm2 patch of contact lens. The team has already used the IGZO system in catheters to measure uric acid, a key indicator of kidney function, and is exploring the possibility of using it for early cancer detection. However, it could be a year or more before a prototype biosensing contact lens is ready for animal testing.

Filter device offers non-invasive cancer diagnosis

Researchers at Washington State University (WSU) are developing a filter-like device that isolates prostate cancer indicators from other cellular information in blood and urine. The device could provide a reliable and non-invasive alternative to prostate biopsy. The WSU team fitted a mat of glass nanosprings with biomarkers designed to attract exosomes – fatty droplets of proteins and RNA that tumour cells shed into body fluids. These exosomes contain genetic information that can be analysed to determine a cancer's molecular composition. The researchers say that their capture technique is more efficient than previous approaches at isolating prostate tumour exosomes from other cellular information. They are now designing a version of their filter-like device for use in a clinical setting (J. Mater. Sci. 52 6907).

The exosome capture technique could enable doctors to determine how cancer patients are responding to different treatments without performing invasive biopsies. For example, a urine sample from a patient with prostate cancer could be passed through the device to measure the number of exosomes specifically from prostate cancer cells. The physician would then propose a treatment plan, and the amount of exosomes in a follow-up urine sample could indicate the therapy's effectiveness. "It may be possible to predict which drugs would be most effective in treating a patient's cancer," said Clifford Berkman, who led the design of the biomarkers. "More broadly, this technology could be expanded to other types of cancers and diseases."

Nanowell chip rapidly picks effective antibiotic

Bacterial infections remain a major cause of death in the Western world, with antibiotic-resistant bacteria strains increasing every day. It is therefore vitally important for doctors to identify which antibiotic works as rapidly as possible, but currently, this process can take two or more days. Now, Israeli scientists have piloted silicon biosensor chips that can direct clinicians to the best antibiotics for treating bacterial infections in around 2–6 hours. The new technology, which is still in development, was presented at the recent European Association of Urology congress.

The researchers developed silicon biosensor chips containing thousands of nanowells, which are coated with a material that allows bacteria to stick to the chip. Once the bacteria have attached to the well, technicians use reflected visual light to count the bacteria, and to see whether the colony is growing. They can then add a different antibiotic in various dilutions to each chip to see which best inhibits bacterial growth. "So far, we have used the system to rapidly identify antibiotics for a range of bacteria, such as E. Coli, which causes many urinary tract infections," said team leader Ester Segal from the Technion – Israel Institute of Technology.

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