When I was younger (possibly too young) I was fascinated by the film The Hollow Man. As a fan of all things girly and predictable, it certainly wasn’t the explosions or the horror that drew me to that particular film. In fact it was one small scene, only 30 minutes in, in which they turned Kevin Bacon invisible. For those of you that haven’t seen this, they injected into him a serum which made him invisible, one layer at a time, starting with skin and muscle, and for a short time, leaving just blood vessels and nerves visible. Gross, but cool. Ignoring the fact that the film ended on an invisibility induced power crazy murdering spree, it’s clear to see the potential advantages of being able to make tissues transparent for research; to be able to see the brain, liver, lungs, to see damage caused or to see problems before they arise.
Dr Viviana Gradinaru leads a lab at Caltech aiming to do essentially this. They have developed a technique which uses hydrogels, injected directly into the tissue or organism of choice, to replace cell membranes, rendering tissues and even whole organisms transparent without affecting their structure. This allows for systems such as the circulatory system or the central nervous system to be visualised as it would appear in nature, giving strong insight into how previously unobservable peripheral tissues are organised.
This model has great potential to provide advances in tissue research. In the Gradinaru lab alone, the technique has already been used extensively to map the neuronal network in brains and to understand the biological basis of epilepsy, as well as to look at viral transportation across the blood brain barrier. Dr Gradinaru has chosen to give away this technology for free, giving the hydrogel formula and methods to anyone who wishes to use the technique and we should expect to see many advances in the field.
Although this is not quite the Hollow Man and we cannot yet turn living organisms invisible, it is certainly a step along the path. Someone just needs to keep check on the psychology of the subjects. No more Kevin Bacons please.
Structural and molecular interrogation of intact biological systems. Nature 497, 332–337 (16 May 2013)
Optogenetic Delay of Status Epilepticus Onset in an In Vivo Rodent Epilepsy Model. PLOSone 8, 4 (24 April 2014)