The material which contains a zinc oxide compound not only captures moisture but releases it without additional energy requirements. And better yet the gel can be cycled more than 1,000 times before losing its absorptive characteristics. The researchers, Dilip Krishna Nandakumar, Yaoxin Zhang, Sai Kishore Ravi, Na Guo, Chun Zhang, and Swee Ching Tan, published their findings in January of this year in the journal Advanced Materials.

They note that what motivated them to find a hygroscopic nanomaterial (one that readily captures moisture from the air, or from saltwater sources), is the growing freshwater crisis around the world exacerbated by anthropogenic climate change and human population growth. The researchers chose a zinc-based compound capable of sustainably harvesting water from humid air to 420% of its own weight. The hydrogel when exposed to natural sunlight and heated to 55 Celsius (131 Fahrenheit), releases its water burden providing energy-less water harvesting which would make it ideal in Developing World countries. A kilogram of the hydrogel can harvest more than 10 liters (2.6 U.S. gallons) of water daily.

In Singapore with its high relative humidity of between 70 and 80%, the air is saturated. This is the ideal environment for air-harvesting freshwater using the gel which can absorb more than 2.5 times its weight in water vapour. The additional benefit is zinc oxide is abundant and cheap. And with no need to add electricity for the gel to work, it has considerable appeal as a solution the world needs presently.

The hydrogel can actually be used as a coating on windows and walls where on the former it would lower room humidity, and on the latter bring down room temperatures. How does it do the latter? When it is absorbing the water it turns from transparent to opaque and can block up to 50% of infrared radiation responsible for heating a room in direct sunlight. How much cooling are we talking about? As much as 7 Celsius (over 12 Fahrenheit) degrees.

Swee Ching Tan, the lead developer of the hydrogel sees the invention “as a floating water-capturing farm” where such an approach “could benefit rural communities where access to clean water remains a challenge,” serving to mitigate the global freshwater crisis.

A number of conducted field tests used floating mats of the hydrogel which once saturated were placed in glass boxes and left to sit in the sunlight. Not only did the hydrogel absorb the water from the sea as advertised, but it also released water vapour which coated the walls of the glass and then ran down the sides to be collected. Temperatures inside the glass boxes reached between 45 and 50 Celsius (113 and 122 Fahrenheit).

The hydrogel may even have other properties which may make it a useful material as a conducting medium in flexible electronics. But consider its primary use and some recent headlines with cities like Cape Town, South Africa, or Sao Paulo, Brazil, almost running out of water, or a story that broke this week about Harare, Zimbabwe, where a drought is causing city residents to line up for hours to get a few pails of water every few days, and you can see just how impactful this invention may prove to be.

I have a personal interest in MSC for use in treating osteoarthritis, something I have suffered from for more than 45 years. I have always been concerned about the viability of stem cell injections particularly in terms of rates of survival once transplanted into an injury site. One reason for concern is how the cells will defend themselves from the body’s natural immune system. MSC implants could be subject to attack from T-cells and other white cells that would treat their arrival as a foreign substance.

But what Ghosh and her colleagues have created is a protective transporting hydrogel shell that contains the MSC supporting the viability of the cells for as much as a month after injection. The hydrogel is a concoction of cellulose-like material and chitosan, a derivative of chitin which forms the exoskeleton of crustaceans like shrimp.

In an article appearing in yesterday’s The Hindu Business Line, Ghosh is quoted stating, “the hydrogel addresses the issue of the long- term survival of adult stem cells in simulated cultures that mimic the actual body tissue. We observed that cells survive and multiply for a period of one month, which is sufficient time for tissue regrowth.” In other words, the hydrogel doesn’t interfere with the capability of the MSC to interact with neighbouring cells and stimulate division.

Ghosh’s hydrogel, following implantation, supports normal functioning of the MSC contained within it. Subsequently the MSC secrete a growth factor called paracrine which signals nearby non-stem cells to alter behaviours. MSC injected into a knee joint protected by the Ghosh hydrogel would, as a result, in no way inhibit signaling to chondrocytes, cartilage cells, or osteocytes, bone cells, to begin to multiply. It is interesting that the two cells tested by Ghosh and her team were chondrocytes, and fibroblasts, the latter skin cells, and showed no inhibiting factors. The next step will be to apply what they have learned in the laboratory to animal studies. And if those are successful we should see human clinical trials in the near future.

The potential of the hydrogel-MSC composite injection serving as scaffolding for reconstructing knee cartilage or repairing wounds and damaged organs cannot be underestimated. The injectable’s ability to take the required shape within an injection site and provide adhesion to the surrounding tissue is a significant breakthrough that if replicable in animal and subsequent human patients, could change the way osteoarthritic joints and other injuries get treated in the near future.

The focus of the Duke research was on creating a meniscus, the cartilage that cushions the inside of the knee between femur and tibia. The meniscus acts as a natural shock absorber and is the usual suspect when a knee begins to fail. I know this from personal experience since my mid-20s because I have severe osteoarthritis in my left knee and less than 10% of my original cartilage. I have had MRIs, x-rays and ultrasounds to check the health of my knee on several occasions. A number of years ago I was informed that knee replacement was recommended. But I have been reluctant to consider a mechanical knee joint believing that I would be better off holding onto my original parts as long as possible. That’s made me look at other therapies including cortisone, hyaluronic acid, platelet and stem cell injections. Currently, I get cortisone injections every three months.

But the work at Duke is fascinating even if it is still at an early stage. Duke used a two-step process to 3D print, at room temperature, a series of hydrogel implants to create a synthetic meniscus precisely designed to fit a knee joint. The choice of material, hydrogel, was based on its inherent adaptability, biocompatibility, and  stability when placed within the body.

Finding the right hydrogel was the important breakthrough. It needed to match the properties of cartilage. At the same time, it had to be printable. Creating accurate digital renderings that could be translated to a printer was the least of the challenges the inventors faced. MRI, x-ray and other imaging technologies could accurately produce 3D representations which could then be rendered to a 3D plot with instructions sent to a printer.

The search for the right hydrogel led to the discovery by a young Duke graduate student, Feichen Yang, who combined two hydrogels together and then added liquid clay to produce a combination of stiffness, softness and stretch. Yang combined the three weaving the distinct polymer chains and clay particles together which formed a liquid. One of the tricks was to alter the proportions of the hydrogel constituents depending on the location within the meniscus. The clay served two purposes. It helped create a liquid consistency that allowed the hydrogel to flow through the print head. Once through the clay hardened giving the hydrogel a stable structure. One meniscus took a day to print.

What Yang has invented can apply to more than knee joints. In fact, it is probably the start of what will be a new printing industry, creating replacement parts for people with damaged hips, knees, shoulders and other areas of anatomy. The variable will be in the materials extruded through the printing head. Even living cells may serve as printer ink.