Tiny spongelike machines sop up blood sugar | Science News for Students

Tiny spongelike machines sop up blood sugar

In mice, microscopic devices patrol the bloodstream to treat diabetes
Sep 22, 2017 — 8:01 am EST
insulin shot

Some people with diabetes must give themselves shots of medication every day. The injections contain a hormone called insulin. This keeps their blood sugar level from rising too high. But researchers are inventing shot-free ways to control diabetes.

AndreyPopov/istockphoto

This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.

In a laboratory in China, a horde of miniscule, bloblike machines flow in a mouse’s blood. The tiny machines, or nanomachines, are a brand-new invention. They could completely change the way people treat a disease called diabetes.

Diabetes disrupts the body’s ability to control the level of sugar in the blood. If blood sugar gets too high or too low, a person (or mouse) could get sick or even die.

These nanomachines are working to prevent that. They patrol the blood, seeking sugar. Each machine is a hollow, plastic ball just one one-hundredth the diameter of a human hair. When a lot of sugar is in the blood, the nanomachine sops it up and swells in size. When the blood sugar level is low, sugar seeps out of the ball.

Chemist Jianzhong Du of Tongji University in Shanghai, China, invented this nanomachine. He calls it a “sugar sponge.”

sugar sponge
The “sugar sponge” is a tiny, plastic machine that absorbs sugar. At left is a picture of the nanomachine without sugar inside. As it fills up, it swells in size (shown at right).
Reprinted (adapted) with permission from Y. Xiao ​et​ ​al/JACS, 2017.​ ​​Copyright 2017 American Chemical Society

In healthy people (or mice), the body maintains a consistent level of sugar in the blood on its own. This sugar comes from food. After digestion, sugar travels through the bloodstream, providing fuel the body needs.

The body’s cells feast on a form of sugar called glucose. They need a steady supply of the stuff in order to do their jobs. Since people don’t eat constantly, the body must store some sugar for later. The liver plays an important role in this process. It tucks away extra sugar, releasing it gradually as the body needs it. The liver can also make sugar itself.

But the liver needs a way to know how much sugar is in the blood already. Hormones help with this. These chemicals are like keys that unlock certain liver cells. Depending on which kind of key arrives, the liver will either make or stash more sugar. Insulin is a hormone that signals the liver to store sugar.

Tiny ‘sponges’ sop up and squeeze out sugar

In people with diabetes, the body either doesn’t make any insulin or doesn’t use it correctly. Without insulin, the whole system gets out of whack. The level of glucose in the blood can get dangerously high or low. People with diabetes must carefully track the level of sugar in their blood. Some must also give themselves shots of insulin. Sometimes, they need to do this several times a day. Ouch! Other times, they may forget a shot or take too much insulin. A mistake like this could make a person very sick.

Du wondered if a new approach might improve the lives of people with diabetes. Maybe he could help them avoid pesky insulin shots. He decided to develop a nanomachine that could absorb and release sugar. “The natural function of the liver inspired me to develop this new technique,” he says.

The sugar sponge is essentially a hollow, plastic sphere. But its surface also contains a special protein called concanavalin A. This protein sticks to glucose, trapping it within the sphere. Du says, “Like sponges sop up water and swell, our sugar sponge absorbs glucose and swells.” The process works in reverse, too. A soaking wet sponge on a dry surface leaks slowly. Similarly, when the amount of glucose in the blood stream is low, the sugar sponge can’t hold onto all its sugar. It will release it slowly.

Du’s team tested the sugar sponge in mice. The team started with a group of 20 diabetic mice. Five mice received a sugar sponge injection. The rest got injections with similar materials that didn’t absorb sugar. Only the sugar sponge made a difference. It brought the level of sugar in the mice’s blood into a normal range. The benefit lasted for two days. After that, the diabetic mice once again had too much sugar in their blood.

Du and his colleagues reported their results in the Journal of the American Chemical Society in May.

The invention is not yet ready for people to use. “There is still a long way to go,” says Du. His team is working to increase the amount of time that the effect lasts. “We are aiming for [the treatment] to last one week, one month or even longer,” he says. Getting a sugar sponge injection every month would certainly be more convenient than insulin shots every day.

Omid Veiseh, who was not involved in the research, thinks the concept of the sugar sponge is imaginative and creative. However, he worries about the fact that the sugar sponges contain concanavalin A. This protein could trigger an allergic reaction, he says.

To better understand how the treatment might affect humans, Du says, his team must take several steps. First, they must test the sugar sponge on animals that are more similar to humans, such as macaque monkeys. They also need to make sure that the proteins and plastics in the sugar sponge won’t damage organs such as the kidney and liver.

A shield for new insulin-making cells

Veiseh is trying a different approach to help diabetics avoid insulin injections. He is a bioengineer at Rice University in Houston, Texas. A bioengineer is a scientist who builds tools to solve medical problems.

Some people develop diabetes because their own immune systems attack and destroy the cells that make insulin. Veiseh and his colleagues have found a way to replace these cells. They start with stem cells. These are seedlike cells that can develop into any type of cell in the body. Genes provide the instructions that tell stem cells what to grow into. Veiseh’s team used specific genes to prompt human stem cells to grow into insulin-making cells.

But just placing these new cells into the body of a person with diabetes wouldn’t help. The person’s immune system would attack and destroy them. The cells needed a shield. The researchers decided to use a gel called alginate, which originally comes from brown algae. They tested 800 variations of this gel in experiments with mice and primates. One worked better than all the others to protect the cells from an immune system attack.

“We call it a protective bubble,” says Veiseh. In a follow-up experiment, his team implanted shielded cells into mice with diabetes. The cells helped the mice produce their own insulin again. His team reported their results in the March 2016 issue of Nature Medicine.

Miniature protective bubbles and tiny sugar-seeking spheres both sound like something out of a science fiction story. But both are real. Thanks to innovators like Du and Veiseh, the field of medicine is getting more and more high-tech every day.

Power Words

(for more about Power Words, click here)

algae     Single-celled organisms, once considered plants (they aren’t). As aquatic organisms, they grow in water. Like green plants, they depend on sunlight to make their food.

bioengineer     Someone who applies engineering to solve problems in biology or in systems that will use living organisms.

blood sugar     The body circulates glucose, a type of simple sugar, in blood to tissues of the body where it will be used as a fuel. The body extracts this simple sugar from breakdown of sugars and starches. However, some diseases, most notably diabetes, can allow an unhealthy concentration of this sugar to build up in blood.

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

colleague     Someone who works with another; a co-worker or team member.

diabetes     A disease where the body either makes too little of the hormone insulin (known as type 1 disease) or ignores the presence of too much insulin when it is present (known as type 2 diabetes).

diameter     The length of a straight line that runs through the center of a circle or spherical object, starting at the edge on one side and ending at the edge on the far side.

disrupt     (n. disruption) To break apart something; interrupt the normal operation of something; or to throw the normal organization (or order) of something into disorder.

fiction     (adj. fictional) An idea or a story that is made-up, not a depiction of real events.

field     An area of study, as in: Her field of research was biology. Also a term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street. It is the opposite of an artificial setting, such as a research laboratory.

fuel     Any material that will release energy during a controlled chemical or nuclear reaction. Fossil fuels (coal, natural gas and petroleum) are a common type that liberate their energy through chemical reactions that take place when heated (usually to the point of burning).

function     A relationship between two or more variables in which one variable (the dependent one) is exactly determined by the value of the other variables.

gel     A gooey or viscous material that can flow like a thick liquid.

gene     (adj. genetic) A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

glucose     A simple sugar that is an important energy source in living organisms. As an energy source moving around the bloodstream, it may be known as “blood sugar.” It is half of the molecule that makes up table sugar (also known as sucrose).

hormone     (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.

immune     Able to ward off a particular infection. Alternatively, this term can be used to mean an organism shows no impacts from exposure to a particular poison or process. More generally, the term may signal that something cannot be hurt by a particular drug, disease or chemical.

immune system     The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.

insulin     A hormone produced in the pancreas (an organ that is part of the digestive system) that helps the body use glucose as fuel.

journal     (in science) A publication in which scientists share their research findings with experts (and sometimes even the public). Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.

kidney     Each in a pair of organs in mammals that filters blood and produces urine.

liver     An organ of the body of animals with backbones that performs a number of important functions. It can store fat and sugar as energy, break down harmful substances for excretion by the body, and secrete bile, a greenish fluid released into the gut, where it helps digest fats and neutralize acids.

macaque     A monkey with cheek pouches and a short tail that lives mainly in the forest.

organ     (in biology) Various parts of an organism that perform one or more particular functions. For instance, an ovary is an organ that makes eggs, the brain is an organ that makes sense of nerve signals and a plant’s roots are organs that take in nutrients and moisture.

plastic     Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.

primate     The order of mammals that includes humans, apes, monkeys and related animals (such as tarsiers, the Daubentonia and other lemurs).

protein     A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.

science fiction     A field of literary or filmed stories that take place against a backdrop of fantasy, usually based on speculations about how science and engineering will direct developments in the distant future. The plots in many of these stories focus on space travel, exaggerated changes attributed to evolution or life in (or on) alien worlds.

society     An integrated group of people or animals that generally cooperate and support one another for the greater good of them all.

sponge     A primitive aquatic animal with a soft, porous body.

stem cell     A “blank slate” cell that can give rise to other types of cells in the body. Stem cells play an important role in tissue regeneration and repair.

Texas     The second largest state in the United States, located along the southern border with Mexico. It is about 1,270 kilometers (790 miles) long and covers an area of 696,000 square kilometers (268,581 square miles).

tool     An object that a person or other animal makes or obtains and then uses to carry out some purpose such as reaching food, defending itself or grooming.

Citation

Journal:​ ​​Y. Xiao ​et​ ​al.​ Sugar-breathing glycopolymersomes for regulating glucose level.​ ​​Journal​ of the American Chemical Society.​ ​​Vol.​ ​139,​ ​ May 16, 2017, p. 7640-7647. doi:​ ​10.1021/jacs.7b03219.

Journal: A.J. Vegas et al. Long-term glycemic control using polymer-encapsulated human stem cell–derived beta cells in immune-competent mice. Nature Medicine. Vol. 22, March 2016, p. 306-311. doi:10.1038/nm.4030.