Point of Care: an iPod-sized biosensor

The miniature NMR biosensor is an ongoing nanotechnological challenge. A recent Nature article describes one such device (figure shown above) made with a simple permanent magnet, miniaturized NMR electronics, microfluidics for sample handling and an array of microcoils for making NMR measurements. Basically, the device takes in a sample, presumably through some well, and sends it through a network of microfluidic channels that mix it with magnetic nanoparticles that are sensitive to some analyte within the sample. Upon binding to a target, the magnetic nanoparticles cluster and have a shorter T2. Having multiple microfluidic channels enables parallel analysis of different samples. Since you can only fit so many such channels into something the size of an iPod nano, the panel of microfluidic channels will have to be recyclable or replaceable.

Point of Care: Personalized Medicine II

Personalized medicine is poised to change the way we relate to our health. The sequencing of the human genome has fundamentally affected our understanding of certain diseases, forcing an ideological retreat from the one-size-fits all approach to treating disease.
Two necessary criteria must be satisfied by any device that aims to do for medicine what the iPhone has done to ICT. This pocket-diagnostician must be both miniature and integrationist in its design. T2 Biosystems' NanoDx is small enough to be carried out into the field and used at home but doesn't quite make the cut as a handy device in today's world. The NanoDx uses NMR, MRI's scientific cousin, to detect viruses and signature proteins in blood, saliva and urine. The sample is loaded onto a disposable cartridge containing magnetic nanoparticles. The presence of an analyte causes the nanoparticles to cluster, resulting in a cooperative enhancement in the magnetic properties of the particles. These magnetic particles, in turn, reduce the time it takes for the net transverse magnetization (T2) of neighboring water protons in a sample to be completely dephased or lost in a magnetic field. This physical effect is translated into a readout.
The key advantage of using NMR over other techniques lies in its capacity to analyze "dirty" samples. Sticking your head in an MRI machine generates an image because it maps the behavior of water protons in your body based on their location. Magnetic resonance (MR) analysis does away with the need for building a purification system into the device. A simpler device means a cheaper device.
These issues of simplicity and cost are especially crucial if a technology is to be utilized in developing countries. More on miniaturist design and cost issues in my next blog.