Abstract
The need to incorporate advanced engineering tools in biology, biochemistry and medicine is in great demand. With the rapid emergence of nanotechnologies during the past decade, it is becoming hard to deny the great impact the new technologies can make on our everyday life and especially the fields of biology and medicine. In this review article, we discuss one such technology, nanoliter-volume nuclear magnetic resonance spectroscopy (NMR), which could be used for chemical signature-based detection of ultra-small quantities of biomolecules. NMR spectroscopy has been used by biochemists for over two decades. However, conventional NMR spectrometers are relatively costly, bulky and often require special laboratory environment for their proper operation. Such NMR systems require ultra-high magnetic field, i.e., of the order of several Tesla, in a relatively large volume and therefore require special shielding and installation. The major challenge for successful scaling of the conventional NMR systems down to the nanoscale range is the difficulty in maintaining adequate (for reasonable signal detection) signal-to-noise ratio (SNR). This paper discusses a new technology aimed to develop NMR spectrometers that not only could be scaled down to the nanoscale range but also could operate with adequate SNR at field strengths as low as 1/4 Tesla. The largest physical component of this system is a ring-shaped permanent magnet that has an outer diameter of 40 mm. The system was designed via computer simulations to consider the magnetostatic interactions between relatively components of the system (magnets, coils, sensors, shields, and so on) and also spin dependent nanoscale magnetic devices which could be used to further boost the net signal to noise ratio of the system. Particularly, a special tunneling magneto-resistive sensor array was designed to achieve the goal of further increasing SNR. The computational tools include direct digital synthesis to generate RF signals with an ultra-high frequency precision, digital signal processing to filter and condition the retrieved NMR signal and a special backpropagation neural network based computer chip to find the optimum match for the NMR spectrum of a sample under investigation. This portable NMR system is intended to analyze samples with volumes as small as a few hundreds of nanoliters at room temperature. In the future, the discussed technology could be further developed to detect a wide range of chemicals at a single-molecule level.
