Researchers in the US have developed a new microscopy technique that can pinpoint unlabelled molecules in biological tissue at depths of up to several millimetres. This is much deeper than current methods, which are limited to about 100 µm. Called vibrational photoacoustic (VPA) microscopy, the technique has been used to make 3D images of plaque lining arteries and could be used for diagnosing diseases such as atherosclerosis.
In recent years, scientists have developed microscopy techniques that can locate specific molecules in a biological sample without the need to label those molecules. Although techniques such as stimulated Raman scattering and coherent anti-Stokes Raman scattering have revolutionized biological imaging, their use is limited by their relatively small penetration depth.
Now, a team led by Ji-Xin Cheng at Purdue University has increased this depth by being the first to demonstrate VPA microscopy. Exploiting the photoacoustic effect in imaging and microscopy is not a new idea, but what the researchers do differently is to use the effect to target specific molecules.