BLOGS

Topics: Bioengineering, Optical Physics, Nanorods, Nanotechnology

Even in the dark, rattlesnakes and their fellow pit vipers can strike accurately at small warm-blooded prey from a meter away. Those snakes, and a few others, can see in the IR—but not with their eyes. Rather, they have a pair of specialized sensory organs, called pit organs, located between their eyes and their nostrils and lined with nerve cells rich in temperature-sensitive proteins that cause the neurons to fire when heated.¹ The pits work like pinhole cameras to focus incoming thermal radiation onto their heat-sensitive back walls; the thermal images are then superimposed with visual images in the snake’s brain.

Heat-responsive neurons are not unique to snakes. We have them over every inch of our skin, to feel objects warm to the touch, and on our tongues, to taste spicy food. But the snakes’ ability to resolve the source of radiated heat at a distance is unusual.

Inspired by the snakes, Dasha Nelidova and her colleagues at the Institute of Molecular and Clinical Ophthalmology in Basel, Switzerland, are developing a new treatment for forms of blindness caused by the degeneration of retinal photoreceptors.² Using gene therapy, they endow remaining retinal cells with thermoresponsive proteins, thereby compensating for their lost light sensitivity with heat sensitivity. The proteins by themselves aren’t sensitive enough to rival normal vision, so the researchers tether them to gold nanorods, as shown in figure 1. The 80-nm-long nanorods strongly absorb near-IR light at 915 nm and convey the concentrated heat to the attached proteins.

Near-IR nanosensors help blind mice see, Johanna L. Miller, Physics Today

A lattice scaffold 3D printed directly onto soft living tissue. (Courtesy: Ohio State University)

Topics: 3D Printing, Bioengineering, Biofabrication, Biology, Tissue Engineering

Tissue engineering is an emerging field in which cells, biomaterials and biotechnologies are employed to replace or regenerate damaged or diseased tissues. Currently, this is achieved by generating a biomaterial scaffold outside of the body, maturation in a bioreactor and then surgically implanting the created tissue into the patient. This surgery, however, poses the added risk of infection, increases recovery time and may even negate the therapeutic benefits of the implant.

To prevent such complications, a US research team is developing a way to fabricate 3D tissue scaffolds inside a living patient – so-called intracorporeal tissue engineering. The researchers, from the Terasaki Institute, Ohio State University and Pennsylvania State University, aim to use robotic direct-write 3D printing to dispense cell-laden biomaterials (bioinks) in a highly precise, programmable manner. The printed bioinks are delivered through minimally invasive surgical incisions and the body itself acts as the bioreactor for maturation.

Any technique used to directly print tissues inside the body, however, must meet a specific set of requirements. The biomaterial must be 3D printable at body temperature (37 °C), for example, and all procedural steps should not harm the patient. For example, current methods use UV light to crosslink the constructed tissue, which is not safe for use within the body.

To meet these requirements, the team produced a specially-formulated bioink designed for printing directly in the body. They used the hydrogel gelatin methacryloyl (GelMA) as the biomaterial, and introduced Laponite and methylcellulose as rheological modifiers to enhance printability. “This bio-ink formulation is 3D printable at physiological temperature, and can be crosslinked safely using visible light inside the body,” explains first author Ali Asghari Adib.

Tissue engineering moves closer to 3D printing inside the body, Tami Freeman, Physics World