Smartphone camera can illuminate bacteria causing acne, dental plaque

smart phone camera illuminates bacteria
PHOTO: Antonioguillem 123RF

Researchers in the US have developed a method that uses smartphone-derived images to identify potentially harmful bacteria on skin and in oral cavities. 

Their approach—published in Optics and Lasers in Engineering—can visually identify microbes on skin contributing to acne and slow wound healing, as well as bacteria in the oral cavity that can cause gingivitis and dental plaque.

The team at the University of Washington combined a smartphone-case modification with image-processing methods to illuminate bacteria on images taken by a conventional smartphone camera. This approach yielded a relatively low-cost and quick method that could be used at home to assess whether potentially harmful bacteria are present on skin and in the oral cavity.

“Bacteria on skin and in our mouths can have wide impacts on our health—from causing tooth decay to slowing down wound healing,” project lead Professor Ruikang Wang said.

“Since smartphones are so widely used, we wanted to develop a cost-effective, easy tool that people could use to learn about bacteria on skin and in the oral cavity.”

Bacteria aren’t easy to see using conventional smartphone images. Smartphone cameras are RGB cameras that essentially funnel all the different wavelengths of light in the visual spectrum into three different colours: red, green and blue. Every pixel in a smartphone-generated image is a combination of those colours. But bacteria emit many colours beyond red, green and blue, which a typical smartphone camera misses.

Professor Wang’s team augmented the smartphone camera’s capabilities by attaching a small 3D-printed ring containing 10 LED black lights around a smartphone case’s camera opening. The researchers used the LED-augmented smartphone to take images of the oral cavity and skin on the face of two research subjects.

The LED lights ‘excite’ a class of bacteria-derived molecules called porphyrins, causing them to emit a red fluorescent signal that the smartphone camera can then pick up.

Other components in the image—such as proteins or oily molecules produced by our bodies, as well as skin, teeth and gums—won’t glow red under LED. They’ll fluoresce in other colours.

Many bacteria produce porphyrins as a byproduct of their growth and metabolism. The porphyrins can accumulate on skin and in our mouths where bacteria are present in high amounts.

The LED illumination gave the team enough visual information to computationally ‘convert’ the RGB colours from the smartphone-derived images into other wavelengths in the visual spectrum. This generates a ‘pseudo-multispectral’ image consisting of 15 different sections of the visual spectrum—rather than the three in the original RGB image. 

With their greater degree of visual discrimination, the pseudo-multispectral images clearly resolved porphyrin clusters on the skin and within the oral cavity. 

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