Smarter Smart Phones

But why target smart phones? “Phones have such great computational, communication, and sensing capabilities – it is now feasible for them to perform tasks that previously could only be performed by large and expensive laboratory instruments,” says Cunningham. A single smart phone- based instrument is clearly not geared to high throughput analysis. Rather, the focus is on bringing detection to the sample or patient in environments that previously made analysis difficult or impossible.

“On the medical side, we started by thinking of assays for nutritional deficiency in remote parts of the world where there are not many doctors or diagnostic lab facilities,” says Cunningham. “We have also been thinking of ways that people could more easily monitor the status of their health or the status of their treatment regimen through regular monitoring of a biomarker.”

While medical applications are a tempting prize, Cunningham recognizes the regulatory hurdles. “I think that the regulatory path for medical applications can be expensive and lengthy, but fortunately there are many other applications that can be addressed. For example, detection of pathogens in food/water, measuring the protein or chemical contents of food or even of pharmaceutical source materials,” he says.

So, how far from a portable biosensor in every pocket or purse? “In five years I think there will be inexpensive add- ons that will enable the most popular phones to perform analysis by using biosensor cartridges that contain the reagents and automate the assay protocol,” says Cunningham. Moreover, the use of an intelligent app can provide detailed instructions to perform the assay as well as analyze and display the results. “I think such approaches will eventually gain FDA approval for certain applications. Apps will be able to share data with a Cloud-based data management system to enable large- scale studies (for example, mapping the gluten content of the crusts from every pizza restaurant in New York City) or analysis of medical conditions by a remote physician. There are a huge number of potential applications,” concludes Cunningham.

How it Works

1. Functionalized photonic crystal fixed to standard microscope slide.
2. Slide placed into optical path of cradle
3. External broadband light passes through biosensor (resonant at only narrow band of wavelengths)
4. Diffraction grating spreads non-resonant wavelengths over smart phone camera pixels.
5. App displays photonic crystal’s high-resolution transmission spectrum and calculates resonant wavelength with 0.009nm accuracy.
6. Slide exposed to sample and re-measured
7. The degree of resonant wavelength shift indicates amount of target molecule present in sample
   
   Cost: $200
   Analysis time: ~ 2 min per sample

Researchers at the University of Illinois have developed a cradle accessory for the iPhone that aligns its integral camera with a series of optical components to analyze a primed slide. The result? A portable biosensing spectrophotometer that rivals a $50,000 laboratory instrument for accuracy, according to the team. In their paper in Lab on a Chip (1), an immune system protein was the main focus, but the sample slide can be primed for any biological molecule or cell type. Team leader Brian Cunningham tells The Analytical Scientist: “So far, we have demonstrated detection based on label-free photonic crystal biosensors and enzyme-linked immunosorbent assay (ELISA). We are working towards using the same detection hardware to perform fluorescence resonance energy transfer (FRET) and fluorescence polarization (FP) assays. We will be sharing results from those approaches soon.”