3D paper sensor could detect malaria, HIV
Researchers in the US have developed a 3D paper sensor that could test for diseases such as malaria and HIV for less than $0.10.
Inspired by the paper folding art of origami, the low cost point-of-care device is expected to be of great use in developing world, where the resources often don't exist to pay for lab based tests, and where, even if the money is available, the infrastructure often doesn't exist to transport biological samples to the lab.
"This is about medicine for everybody," said Richard Crooks, Professor of Chemistry at the University of Texas at Austin.
Compared to one dimensional paper sensors - such as those used in pregnancy tests - Crooks says the 3D sensors can test for more substances in a smaller surface area and provide results for more complex tests.
"Anybody can fold them up," he notes. "You don't need a specialist, so you could easily imagine an NGO (non-governmental organisation) with some volunteers folding these things up and passing them out. They're easy to produce as well, so the production could be shifted to the clientele as well. They don't need to be made in the developed world."
Inspired by a 3D microfluidic paper sensor developed by Harvard University chemist George Whitesides, Crooks and doctoral student Hong Liu, looked to build a similar device that was less expensive and less time consuming to produce.
Within a few weeks of experiments, Liu had fabricated the sensor on one simple sheet using a simple office printer in the university's lab. Folding it over into multiple layers, he says, takes less than a minute and requires no tools or special alignment techniques.
Crooks believes that the principles underlying the sensor, which have been successfully tested on glucose and a common protein, are related to the home pregnancy test. A hydrophobic material, such as wax or photoresist, is laid down into tiny canyons on chromatography paper. It channels the sample that's being tested - urine, blood, or saliva, for instance - to spots on the paper where test reagents have been embedded.
If the sample has whatever targets the sensor is designed to detect, it'll react in an easily detectable manner. It might turn a specific colour, for instance, or fluoresce under a UV light. Then it can be read by eye.
"Biomarkers for all kinds of diseases already exist," said Crooks. "Basically you spot test reagents for these markers on these paper fluidics. They're entrapped there. Then you introduce your sample. At the end you unfold this piece of paper, and if it's one colour, you've got a problem, and if not, then you're probably OK."
Crooks and Liu have also engineered a way to add a simple battery to their sensor so that it can run tests that require power. Their prototype uses aluminium foil and looks for glucose in urine.
Crooks estimates that including such a battery would add only a few cents to the cost of producing the sensor. A urine sample is said to be all that is needed for it to be activated.
