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A hydrogel is a three-dimensional (3D) network of hydrophilic polymers that can swell in water and hold a large amount of water while maintaining the structure due to chemical or physical cross-linking of individual polymer chains. Hydrogels were first reported by Wichterle and Lím (1960). By definition, water must constitute at least 10% of the total weight (or volume) for a material to be a hydrogel. Hydrogels also possess a degree of flexibility very similar to natural tissue due to their significant water content.
Hydrogels undergo a significant volume phase transition or gel-sol phase transition in response to certain physical and chemical stimuli. The physical stimuli include temperature, electric and magnetic fields, solvent composition, light intensity, and pressure, while the chemical or biochemical stimuli include pH, ions, and specific chemical compositions. However, in most cases such conformational transitions are reversible; therefore, the hydrogels are capable of returning to their initial state after a reaction as soon as the trigger is removed. The response of hydrogels to external stimuli is mainly determined by the nature of the monomer, charge density, pendant chains, and the degree of cross-linkage. The magnitude of response is also directly proportional to the applied external stimulus.
Hydrogels have many uses such as Scaffolds in tissue engineering. When used as scaffolds, hydrogels may contain human cells to repair tissue. They mimic 3D microenvironment of cells. Hydrogel-coated wells have been used for cell culture. Environmentally sensitive hydrogels (also known as ‘Smart Gels’ or ‘Intelligent Gels’). These hydrogels have the ability to sense changes of pH, temperature, or the concentration of metabolite and release their load as result of such a change.
Injectable hydrogels which can be used as drug carriers for treatment of diseases or as cell carriers for regenerative purposes or tissue engineering. Sustained-release drug delivery systems. Ionic strength, pH and temperature can be used as a triggering factor to control the release of the drug. Providing absorption, desloughing and debriding of necrotic and fibrotic tissue .Hydrogels that are responsive to specific molecules such as glucose or antigens, can be used as biosensors, as well as in DDS.
New Hydrogel Can Cool Down Electronic Devices and Convert Waste Heat Into Electricity
Using electronic devices for too long can cause them to overheat, which might slow them down, damage their components or even make them explode or catch fire. Now, researchers reporting in ACS’ Nano Letters have developed a hydrogel that can both cool down electronics, such as cell phone batteries, and convert their waste heat into electricity. The thin polymer-based hydrogel film can be strapped to batteries to convert heat to electricity. It works by transferring electrons when heated to generate power.
Components like batteries, LEDs, and microprocessors generate heat during operation. Sometimes, this can lead to overheating which can reduce the efficiency, reliability, and lifespan of devices. Now, researchers from Wuhan and California have reportedly developed a polymer-based hydrogel that can cool down electronics and convert their waste heat into electricity. The team’s research, published in the journal Nano Letters, describes how when attached to a heat source, the thermogalvanic hydrogel film is able to achieve efficient evaporating cooling while simultaneously converting a portion of the waste heat into electricity. The thermogalvanic hydrogel, which is strapped to the battery, is able to change its structure in response to temperature. It was made using a polyacrylamide framework consisting of an organic polymer, lubricant, and an oil recovery agent. This framework is then infused with water and ions.
When the hydrogel is heated up, two of the ions—ferricyanide and ferrocyanide—transfer electrons between electrodes, generating electricity. In the meantime, the water inside of the hydrogel evaporates, cooling it down. The hydrogel then regenerated itself by absorbing water from the surrounding air. The researchers tested their film on a smartphone battery and found that its temperature dropped by 68 degrees Fahrenheit (20 degrees Celsius). Some of the waste heat was also converted into electricity, marking the first time that scientists have developed a device that can do both at the same time. “The reduced working temperature ensures safe operation of the battery, and the electricity harvested is sufficient for monitoring the battery or controlling the cooling system.” said Dr. Xuejiao Hu from Wuhan University in China.
Profusa and Partners Announce Initiation of Study to Measure Early Signs of Influenza Through Biosensor Technology
Profusa, a digital health company that is pioneering the next generation of personalized medicine, today announced the initiation of a study that will use the Company’s minimally invasive injectable biosensor technology, the Lumee® Oxygen Platform, as a platform to potentially assist in the early detection of influenza outbreaks. The study is part of a collaboration with RTI International, a nonprofit research institute developing algorithms for illness detection, and research centers including Duke University and Imperial College London.
The study, conducted at Imperial College London, will examine how sensors monitoring physiological status, including the Lumee Oxygen Platform which measures tissue oxygen levels, provide potential indicators of human response to infection or exposure to disease in healthy volunteers. The goal of the study is to develop an early identification system to detect not only disease outbreaks, but biological attacks and pandemics up to three weeks earlier than current methods. The results of the study are anticipated to be available in 2021.
The sensor has two parts. One is a 3mm string of hydrogel, a material whose network of polymer chains is used in some contact lenses and other implants. Inserted under the skin with a syringe, the string includes a specially engineered molecule that sends a fluorescent signal outside of the body when the body begins to fight an infection. The other part is an electronic component attached to the skin. It sends light through the skin, detects the fluorescent signal and generates another signal that the wearer can send to a doctor, website, etc. It’s like a blood lab on the skin that can pick up the body’s response to illness before the presence of other symptoms, like coughing.
“This research marks an exciting step forward in the development of game-changing preventive care,” said Ben Hwang, chairman and CEO of Profusa. “The Lumee Oxygen Platform can potentially function as a sort of canary in a coal mine for infectious disease, since subtle changes in oxygen at the tissue level may signal trouble and can help clinicians course correct quickly to avoid outbreaks.”Changes in oxygen levels and other physiological measures, such as heart rate, as a result of a respiratory infection may assist researchers in the study to develop algorithms that can detect early, pre-symptomatic flu activity more quickly than what is currently possible.
Despite the availability of antivirals and vaccines, influenza remains one of the greatest causes of illness and premature death worldwide. Seasonal influenza affects between 10% and 46% of the population each year, with mortality of up to approximately 12 deaths per 100,000 in developed countries. During the 2009 H1N1 virus pandemic, many severe cases occurred in previously healthy young adults. With the entire worldwide population potentially at risk, the prevention and improved management of seasonal and pandemic influenza are of major importance.
“The potential significance of this new technology should not be underestimated, and Profusa is proud to be part of a joint effort funded by a DARPA, or Defense Advanced Research Projects Agency, award,” said Sean Givens, head of government business for Profusa. “This is particularly exciting for Profusa as we look forward to leveraging learnings for future platform applications.” Profusa’s Lumee Patch, a wireless reader that adheres to the skin and collects and reports tissue oxygen levels sensed by the Lumee Oxygen sensor to a mobile device for real-time data visualization, will be used in the clinical study.
The Lumee Patch and software being used in this study received approval as an investigational device from Medicines and Healthcare products Regulatory Agency (MHRA) in the UK to be used in conjunction with other devices. The injectable Lumee Oxygen sensor and injector Lumee Pen being used in this study are CE Marked for use in the European Union and EEA. The project is part of DARPA’s SIGMA+ program in the Defense Sciences Office (DSO).
Army researchers explore use of gels for biological decontamination
Removing chemical, biological, radiological and toxic contaminants from a range of surface types could become as easy as peeling off a sticker. U.S. Army Edgewood Chemical Biological Center scientists and an industry partner, CBI Polymer, are researching how a HydroGel can be modified to decontaminate surfaces contaminated with biological agents, such as spores of Bacillus anthracis, which can cause anthrax disease in humans and animals.
HydroGel is a biosynthetic polymer that can be sprayed, painted or poured on a surface, said Dr. Vipin Rastogi, ECBC senior research biologist. HydroGel then dries into a film, which can be peeled away and disposed of with little to no threat to the environment or the operators. The peeled gel does not generate water waste, and it traps any toxic contaminant, such as biological spores. This removes the threat of the agent reaerosolizing, Rastogi said. Conventional decontamination methods involve spraying soapy water and liquid sporicidal agents, which generates a high volume of wastewater that could flow into drains and be added to the environment or be otherwise difficult to safely collect and dispose of. These methods also pose a threat to the operators if residual waste gets sprayed on them.
CBI Polymer created HydroGel to remove toxic material from hard surfaces in an industrial setting. The ease of use, safety and significantly reduced burden to the environment prompted ECBC scientists to explore whether HydroGel could be applicable as a sampling tool for biological contaminants on surfaces. In 2013, ECBC entered a cooperative research and development agreement with CBI Polymers to create modified HydroGel formulas that could decontaminate biological spores. Rastogi and ECBC researchers developed two advanced formulas, called DeconGel, that can successfully decontaminate multiple surfaces of biological agent.
The Department of Homeland Security researched how to decontaminate a subterranean environment, such as a subway station, if contaminated by virulent biological spores. Rastogi and Dr. Garry Edgington of CBI Polymer recommended that DeconGel could solve that issue. Donald Bansleben, a DHS science and technology program manager, sponsored the collaboration between CBIP/Metis and ECBC for the subway application. Rastogi and his team conducted research to prove that DeconGel could remove biological spores from four subway surfaces: steel, aluminum, concrete and tile. “Underground train stations are very complex with all types of curves and angles. There are multiple types of surfaces next to each other that are architecturally challenging,” Rastogi said. “A technology such as DeconGel, which is easy to apply in hard to reach places, could be a real game-changer for this scenario-specific decontamination.”
Bansleben said that DeconGel could be helpful in decontamination efforts. “A universal decontaminant does not exist, but DeconGel can be another tool in the toolkit for remediation of biological agent contamination,” he said. Lisa Smith, an ECBC research biologist, and Rastogi wanted to see whether HydroGel had potential for biological sampling applications in its original, unmodified form. As part of an ECBC basic research program, Smith and Rastogi used the base HydroGel as a potential tool to collect biological agent from porous and non-porous surfaces. “In current methods, if you suspect that a surface is contaminated, you would either use a wipe or a swab to rub down the surface, collect whatever is on it and analyze it in hopes of identifying what the substance is,” Rastogi said. “We wanted to answer the question: ‘Could the original HydroGel be used to collect, preserve and retrieve bio samples for analysis and characterization?’ ”
The difference between this HydroGel and the DeconGel use is that in DeconGel, the formulation kills the spores as gel dries into a film. Encapsulation of the spores in HydroGel allows the spores to remain intact for forensics analysis. “The answer is yes; it is very successful,” Rastogi said. HydroGel used in this way protects the sample better. While wipes and swabs are proven, successful methods, they tend to interfere with the sample by spreading it around, or at times it may not pull enough sample from the surface to enable precise contamination assessment and testing.
ECBC is initiating an inter-agency agreement with the Environmental Protection Agency to compare the cost and effectiveness of sporicidal chemicals when applied as liquids, gels and foams and predict the best option for rapid decontamination of large surfaces during a bioterrorism release. This program is an example of long-standing ongoing partnership between the two agencies, which began in 2004, Rastogi said. Rastogi said he would like to research a composition where DeconGel could be effective for chemical agent decontamination. “DeconGel has a lot of potential and could change a lot in the field of broad-hazard decontamination, including CBRNE threats,” he said. “So we are exploring it and its uses to the fullest.”
