The detection of molecular biomarkers in serum can help with successful disease diagnosis or enable researchers to follow the progression or regression of a disease during clinical trials. New research, published in the Journal of the American Chemical Society by a group led by Dr Cagri Savran of Purdue University in the US details the development of a detection system that uses magnetic beads to 'stick' proteins of interest into a 'diffraction grating' pattern that can be used to determine biomarker concentration when interrogated by a laser. Many methods are currently available to detect disease biomarkers however the researchers believe that there are "important challenges that still remain in minimising sensor size, reducing detection time, eliminating target labelling, minimising signal amplification steps and developing simple and inexpensive fabrication protocols." In an attempt to overcome these challenges, the researchers combined a one-step magnetic bead-based capture process with an optical diffraction grating detection method. The microfabrication of such gratings is a step that can introduce cost and the need for signal amplification. However, the researchers developed a method whereby the magnetic beads 'self-assemble' on a gold-coated glass slide printed with a capture agent in the pattern of a diffraction grating. Because of the large size of the beads compared with the capture agent and biomarkers, the presence of the beads is easily distinguishable by their diffraction intensity and significantly lower analyte diffraction limits. The method was applied to the detection of folate receptor (FR), also known as folate binding protein (FBP), which is over-expressed on the surface of malignant cancer cells and eventually enters the blood serving as a potential tumour biomarker. Using optical microscopes they found that the packing density of the beads increases with increasing concentrations of FR and that the diffraction intensity of the plates. When the gratings were illuminated by a laser the concentration dependence of the packing density was mirrored with the diffraction efficiency observed. They continued by demonstrating the utility of the set up on blood samples from cancer patients diagnosed with different types of cancer "The same principles presented here should apply for detection of many other disease markers present in various body fluids," state the researchers. "Due to its simplicity and high sensitivity, we expect this method to be extremely useful both in research laboratories and in development of devices for point-of-care diagnostics."