Roger Narayan, M.D., Ph.D.

Biomedical engineer Roger Narayan recently completed his Fulbright project at the Institute of Chemistry at the University of Sao Paulo in Brazil, where he lectured, taught a graduate course on biomaterials and collaborated on joint research activities.

The core Fulbright Scholar Program attracts some 800 U.S. faculty and professionals each year to 140 countries to lecture, teach and conduct research. An equal number of academics and professionals from overseas visit the United States each year under a Fulbright Scholar grant.

Almost every day it seems there’s a new use for 3-D printing.

In medicine, the printers are already making prosthetic hands, hearing aid cases and parts of human ears.

But the materials used in some 3-D printing processes could be toxic to humans, particularly if the products get inside the body. So researchers have been looking for ways found a way to replace some of the bad stuff with naturally occurring riboflavin, or vitamin B2.

Riboflavin is found in lots of food, including green veggies, nuts and fish. Our cells aren’t programmed to reject it, which could make it handy for use in 3-D printed medical implants, microneedles or scaffolding to build custom body parts in the lab.

The researchers focused on a 3-D printing technique called two-photon polymerization, which can produce finely detailed, microscopic structures. The 3-D printer uses lasers to transform a potion of light-sensitive chemicals into a solid structure.

But some of the chemicals in that potion can be bad for us, says biomedical engineer Roger Narayan, one of the researchers behind the new technique. “And if they leach out of the material they can cause problems,” he says.

Researchers from North Carolina State University, the University of North Carolina at Chapel Hill and Laser Zentrum Hannover have discovered that a naturally-occurring compound can be incorporated into three-dimensional (3-D) printing processes to create medical implants out of non-toxic polymers. The compound is riboflavin, which is better known as vitamin B2.

“This opens the door to a much wider range of biocompatible implant materials, which can be used to develop customized implant designs using 3-D printing technology,” says Dr. Roger Narayan, senior author of a paper describing the work and a professor in the joint biomedical engineering department at NC State and UNC-Chapel Hill.

The researchers in this study focused on a 3-D printing technique called two-photon polymerization, because this technique can be used to create small objects with detailed features – such as scaffolds for tissue engineering, microneedles or other implantable drug-delivery devices.

Two-photon polymerization is a 3-D printing technique for making small-scale solid structures from many types of photoreactive liquid precursors. The liquid precursors contain chemicals that react to light, turning the liquid into a solid polymer. By exposing the liquid precursor to targeted amounts of light, the technique allows users to “print” 3-D objects.

Two-photon polymerization has its drawbacks, however. Most chemicals mixed into the precursors to make them photoreactive are also toxic, which could be problematic if the structures are used in a medical implant or are in direct contact with the body.

But now researchers have determined that riboflavin can be mixed with a precursor material to make it photoreactive. And riboflavin is both nontoxic and biocompatible – it’s a vitamin found in everything from asparagus to cottage cheese.

Researchers from North Carolina State University have developed a new technique for controlling the crystalline structure of titanium dioxide at room temperature. The development should make titanium dioxide more efficient in a range of applications, including photovoltaic cells, hydrogen production, antimicrobial coatings, smart sensors and optical communication technologies.

Titanium dioxide most commonly comes in one on of two major “phases,” meaning that its atoms arrange themselves in one of two crystalline structures. These phases are “anatase” or “rutile.” The arrangement of atoms dictates the material’s optical, chemical and electronic properties. As a result, each phase has different characteristics. The anatase phase has characteristics that make it better suited for use as an antibacterial agent and for applications such as hydrogen production. The rutile phase is better suited for use in other applications, such as photovoltaic cells, smart sensors and optical communication technologies.

“Traditionally, it has been a challenge to stabilize titanium dioxide in the desired phase,” says Dr. Jay Narayan, John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and co-author of a paper describing the work. “The material tends to transform into the anatase phase below 500 degrees Celsius [C], and transform into the rutile phase at temperatures above 500 C.

Researchers from North Carolina State University, Sandia National Laboratories, and the University of California, San Diego have developed new technology that uses microneedles to allow doctors to detect real-time chemical changes in the body – and to continuously do so for an extended period of time.

“We’ve loaded the hollow channels within microneedles with electrochemical sensors that can be used to detect specific molecules or pH levels,” says Dr. Roger Narayan, co-author of a paper describing the research, and a professor in the joint biomedical engineering department of NC State’s College of Engineering and the University of North Carolina at Chapel Hill.

Existing technology relies on taking samples and testing them, whereas this approach allows continuous monitoring, Narayan explains. “For example, it could monitor glucose levels in a diabetic patient,” Narayan says. Microneedles are very small needles in which at least one dimension – such as length – is less than one millimeter.

Researchers from North Carolina State University have developed extremely small microneedles that can be used to deliver medically-relevant nanoscale dyes called quantum dots into skin – an advance that opens the door to new techniques for diagnosing and treating a variety of medical conditions, including skin cancer.

“We were able to fabricate hollow, plastic microneedles using a laser-based rapid-prototyping approach,” says Dr. Roger Narayan, one of the lead researchers, “and found that we could deliver a solution containing quantum dots using these microneedles.” Microneedles are very small needles in which at least one dimension – such as length – is less than one millimeter. Narayan is a professor in the joint biomedical engineering department of NC State’s College of Engineering and the University of North Carolina at Chapel Hill.

“The motivation for the study was to see whether we could use microneedles to deliver quantum dots into the skin,” Narayan says. “Our findings are significant, in part, because this technology will potentially enable researchers to deliver quantum dots, suspended in solution, to deeper layers of skin. That could be useful for the diagnosis and treatment of skin cancers, among other conditions.” Quantum dots are nanoscale crystals with unique properties in terms of light emission. They hold promise as a tool in medical diagnosis.The researchers created the plastic microneedles and tested them using pig skin, which has characteristics closely resembling human skin. Using a water-based solution containing quantum dots, the researchers were able to capture images of the quantum dots entering the skin using multiphoton microscopy. These images show the mechanism by which the quantum dots enter the layers of skin, allowing the researchers to verify the effectiveness of the microneedles as a delivery mechanism for quantum dots.

A team led by researchers from North Carolina State University has developed two new approaches for incorporating antimicrobial properties into microneedles – vanishingly thin needles that hold great promise for use in portable medical devices. Researchers expect the findings to spur development of new medical applications using microneedles.

Microneedles cause less pain, tissue damage and skin inflammation for patients, and could be a significant component of portable medical devices for patients with chronic conditions, such as Parkinson’s disease or diabetes. However, longstanding concerns regarding the possibility of infection associated with microneedles have been an obstacle to their widespread adoption – until now.

A team led by researchers from North Carolina State University has published a paper that describes the use of a technique called atomic layer deposition to incorporate “biological functionality” into complex nanomaterials, which could lead to a new generation of medical and environmental health applications. For example, the researchers show how the technology can be used to develop effective, low-cost water purification devices that could be used in developing countries.

“Atomic layer deposition is a technique that can be used to create thin films for coating metals or ceramics, and is especially useful for coating complex nanoscale structures,” says Dr. Roger Narayan, the paper’s lead author. “This paper shows how atomic layer deposition can be used to create biologically functional materials, such as materials that have antibacterial properties. Another example would be a material that does not bond to proteins in the body, which could be used for implantable medical sensors.” Narayan is a professor in the joint biomedical engineering department of NC State’s College of Engineering and the University of North Carolina at Chapel Hill.