Diamond and graphite, for example, are but two of the many polymorphs of carbon, meaning that both have the same chemical composition and differ only in the manner in which their atoms are connected. But what a world of difference that connectivity makes: The former goes into a ring and costs thousands of dollars, while the latter has to sit content within a humble pencil.
The inorganic compound hafnium dioxide commonly used in optical coatings likewise has several polymorphs, including a tetragonal form with highly attractive properties for computer chips and other optical elements. However, because this form is stable only at temperatures above 3100 degrees Fahrenheit — think blazing inferno — scientists have had to make do with its more limited monoclinic polymorph. Until now.
A team of researchers led by University of Kentucky chemist Beth Guiton and Texas A&M University chemist Sarbajit Banerjee in collaboration with Texas A&M materials science engineer Raymundo Arroyave has found a way to achieve this highly sought-after tetragonal phase at 1100 degrees Fahrenheit — think near-room-temperature and potential holy grail for the computing industry, along with countless other sectors and applications.
The team’s research, published today in Nature Communications, details their observation of this spectacular atom-by-atom transformation, witnessed with the help of incredibly powerful microscopes at Oak Ridge National Laboratory. After first shrinking monoclinic hafnium dioxide particles down to the size of tiny crystal nanorods, they gradually heated them, paying close attention to the barcode-like structure characterizing each nanorod and, in particular, its pair of nanoscale, fault-forming stripes that seem to function as ground zero for the transition.
The molecular machinery of the human body typically relies on genetic templates to carry out construction. For example, molecular machines called DNA polymerases read DNA base-by-base to build accurate copies.
There are, however, a few black sheep in the world of molecular biology that do not require a template. One such outlier, called terminal deoxynucleotidyl transferase (TdT), works in the immune system and catalyzes the template-free addition of nucleotides — the building blocks of DNA — to a single-stranded DNA.
Seemingly random nucleotide sequences in a single DNA strand wouldn’t seem to have much of a biological use — but materials scientists have figured out what to do with it.
In a new paper, Duke University researchers build on their previous work and now describe in detail how the TdT enzyme can produce precise, high molecular weight, synthetic biomolecular structures much more easily than current methods. Researchers can tailor synthesis to create single-stranded DNA that self-assemble into ball-like containers for drug delivery or to incorporate unnatural nucleotides to provide access to a wide range of medically useful abilities.
The results appear online on May 15, 2017 in the journal Angewandte Chemie International Edition.
“We’re the first to show how TdT can build highly controlled single strands of DNA that can self-assemble into larger structures,” said Stefan Zauscher, the Sternberg Family Professor of Mechanical Engineering and Materials Science at Duke University. “Similar materials can already be made, but the process is long and complicated, requiring multiple reactions. We can do it in a fraction of the time in a single pot.”
Using specialized equipment needed, physicians at UT Southwestern Medical Center’s Harold C. Simmons Comprehensive Cancer Center began using the fusion biopsy procedure about three years ago for its ability to blend live ultrasound images with captured MRI images. The fused image creates the 3D model, and flags anomalies that could be areas of concern. That helps guide urologists to get tissue samples called biopsies to determine whether cancer is present.
UT Southwestern’s early adoption of the cutting-edge technology allowed researchers to report on the superior diagnostic performance of this novel approach compared to traditional methods for diagnosing prostate cancer. Furthermore, these researchers have partnered with colleagues in Brazil to conduct follow up studies that now show the technique consistently improved detection of clinically significant prostate cancer under a wide variety of conditions, even when radiologists were using different equipment and protocols.
“In the past, we diagnosed prostate cancer by random biopsies of the prostate in men with elevated PSA values. With fusion biopsy, we actually find more cancer, we can differentiate between dangerous tumors and less aggressive tumors, and in some cases we perform fewer biopsies,” said Dr. Daniel Costa, Assistant Professor of Radiology and with the Advanced Imaging Research Center (AIRC) at UT Southwestern.
Prostate cancer is the second most common cancer diagnosed in men, after skin cancer. Prostate cancer risk increases with age, with most cases occurring after age 60. According to the National Cancer Institute (NCI), about 180,890 men will be diagnosed this year, and about 14 percent of men will be diagnosed sometime during their lifetime.