Many nucleic acid tests (NATs) rely on a DNA amplification step as the detection mechanism for pathogens, viral load, and so on. Usually, DNA concentration is measured using a spectrophotometric instrument that costs tens of thousands of dollars. In this paper, Heather Whitehead used an inexpensive dye that binds to DNA and a cell phone to measure the concentration of double stranded DNA in the same concentration range commonly used to analyze NAT results. The color of Nile Blue dye shifts from blue to blue-purple to blue as it binds to DNA. While it's been known for many years that Nile Blue dye changes color when it binds to DNA, and that property has been used to develop instrumental assays, Heather figured out that by using different concentrations of the Nile Blue dye and monitoring the red, green, and blue channel intensities, the concentration of double stranded DNA can be measured with an error of less than 10 ug/ml. …
A global problem
Many of the pharmaceuticals that are purchased in the developing world are substandard or outright fake drugs. Although there is no global system for monitoring the quality of medicine, study after study reveals pervasive poor quality and products that are worthless or even harmful to patients. Many countries in the developing world do not have the technological infrastructure or regulatory resources to keep low quality medicines off the market shelves. And since the pharmaceutical trade is a lucrative global market, low quality medicine can cross borders and harm people anywhere in the world.
Negligence by manufacturers
- A heart medicine called "Isotab" killed over 200 people in Pakistan when one batch was manufactured using toxic quantities of an antimalarial medicine in place of the inert filler that was supposed to be added. According to the Pakistani government's report (pathology_of_negligence_pic_drug_inquiry_report_2012.pdf) the antimalarial drug got wet during delivery, and was moved into a drum marked "starch". No-one ever changed the label or noticed the substitution.
Deliberate falsification by manufacturers or distributors
- Fortune Magazine has a great investigatory report on Ranbaxy's contribution to this area.
- Even secure supply chains fall victim; see this WHO report on testing company Semler Research faking bioequivalence studies.
New ways to find fake medicines
Paper analytical devices (PADs) are test cards that can quickly determine whether a drug tablet contains the correct medicines. They are cheap and easy to use. They don't require power, chemicals, solvents, or any expensive instruments, so they can be deployed rapidly at large scale whereever a problem with pharmaceutical quality is suspected.
Partnering with regulatory agencies
By sharing our results directly with medical regulatory agencies, we help them quickly discover poor quality medicines in their markets. This enables them to negotiate with manufacturers and distributors from a position of knowledge and to take other regulatory and legal actions to protect patients from poor quality products.
Bringing market forces to bear
In the developing world, most buyers have to trust what the seller tells them about the quality of the pharmaceuticals they purchase. Unscrupulous manufacturers and distributors know that there is little chance that their medicines will be screened in a lab. These paper test cards don't need a lab, and they will enable people all over the world to quickly detect low quality medicines and remove them from the market.