A hydrogel is a biphasic material, a mixture of porous, permeable solids and at least 10% by weight or volume of interstitial fluid composed completely or mainly by water. In hydrogels the porous permeable solid is a water insoluble three dimensional network of natural or synthetic polymers and a fluid, having absorbed a large amount of water or biological fluids. These properties underpin several applications, especially in the biomedical area. Many hydrogels are synthetic, but some are derived from nature. The term 'hydrogel' was coined in 1894.
In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural polymers.
Molecular machines are a class of molecules typically described as an assembly of a discrete number of molecular components intended to produce mechanical movements in response to specific stimuli, mimicking macromolecular devices such as switches and motors. Naturally occurring or biological molecular machines are responsible for vital living processes such as DNA replication and ATP synthesis. Kinesins and ribosomes are examples of molecular machines, and they often take the form of multi-protein complexes. For the last several decades, scientists have attempted, with varying degrees of success, to miniaturize machines found in the macroscopic world. The first example of an artificial molecular machine (AMM) was reported in 1994, featuring a rotaxane with a ring and two different possible binding sites.
The Paternò–Büchi reaction, named after Emanuele Paternò and George Büchi, who established its basic utility and form, is a photochemical reaction, specifically a 2+2 photocycloaddition, which forms four-membered oxetane rings from an excited carbonyl and reacting with an alkene.
A photoswitch is a type of molecule that can change its structural geometry and chemical properties upon irradiation with electromagnetic radiation. Although often used interchangeably with the term molecular machine, a switch does not perform work upon a change in its shape whereas a machine does. However, photochromic compounds are the necessary building blocks for light driven molecular motors and machines. Upon irradiation with light, photoisomerization about double bonds in the molecule can lead to changes in the cis- or trans- configuration. These photochromic molecules are being considered for a range of applications.
Chi-Huey Wong is a Taiwanese-American biochemist. He is currently the Scripps Family Chair Professor at the Scripps Research Institute, California in the department of chemistry. He is a member of the United States National Academy of Sciences, won the Wolf Prize in Chemistry and the RSC Robert Robinson Award. and has published more than 700 papers and holds more than 100 patents.
The term "polymer" refers to large molecules whose structure is composed of multiple repeating units and the prefix "supra" meaning "beyond the limits of". Supramolecular polymers are a new category of polymers that can potentially be used for material applications beyond the limits of conventional polymers. By definition, supramolecular polymers are polymeric arrays of monomeric units that are connected by reversible and highly directional secondary interactions–that is, non-covalent bonds. These non-covalent interactions include van der Waals interactions, hydrogen bonding, Coulomb or ionic interactions, π-π stacking, metal coordination, halogen bonding, chalcogen bonding, and host–guest interaction. The direction and strength of the interactions are precisely tuned so that the array of molecules behaves as a polymer in dilute and concentrated solution, as well as in the bulk.
William (Bill) DeGrado is a professor at the University of California, San Francisco, where he is the Toby Herfindal Presidential Professor of Entrepreneurship and Innovation in the Department of Pharmaceutical Chemistry. As an early pioneer of protein design, he coined the term de novo protein design. He is also active in discovery of small molecule drugs for a variety of human diseases. He is a member of the U.S. National Academy of Sciences (1999), American Academy of Arts & Sciences (1997) and National Academy of Inventors. He also is a scientific cofounder of Pliant therapeutics.
A molecular switch is a molecule that can be reversibly shifted between two or more stable states. The molecules may be shifted between the states in response to environmental stimuli, such as changes in pH, light, temperature, an electric current, microenvironment, or in the presence of ions and other ligands. In some cases, a combination of stimuli is required. The oldest forms of synthetic molecular switches are pH indicators, which display distinct colors as a function of pH. Currently synthetic molecular switches are of interest in the field of nanotechnology for application in molecular computers or responsive drug delivery systems. Molecular switches are also important in biology because many biological functions are based on it, for instance allosteric regulation and vision. They are also one of the simplest examples of molecular machines.
Stefan Hecht is a German chemist.
Polyaspartic acid (PASA) is a biodegradable, water-soluble condensation polymer based on the amino acid aspartic acid. It is a biodegradable replacement for water softeners and related applications. PASA can be chemically crosslinked with a wide variety of methods to yield PASA hydrogels. The resulting hydrogels are pH-sensitive such that under acidic conditions, they shrink, while the swelling capacity increases under alkaline conditions.
Biman Bagchi is an Indian scientist currently serving as a SERB-DST National Science Chair Professor and Honorary Professor at the Solid State and Structural Chemistry Unit of the Indian Institute of Science. He is a theoretical physical chemist and biophysicist known for his research in the area of statistical mechanics; particularly in the study of phase transition and nucleation, solvation dynamics, mode-coupling theory of electrolyte transport, dynamics of biological macromolecules, protein folding, enzyme kinetics, supercooled liquids and protein hydration layer. He is an elected fellow of the Indian National Science Academy, the Indian Academy of Sciences, The World Academy of Sciences and an International honorary member of the American Academy of Arts and Sciences. Along with several scientific articles, he has authored three books, (i) Molecular Relaxation in Liquids, (ii) Water in Biological and Chemical Processes: From Structure and Dynamics to Function, and (iii) Statistical Mechanics for Chemistry and Materials Science.
Hydrogels are three-dimensional networks consisting of chemically or physically cross-linked hydrophilic polymers. The insoluble hydrophilic structures absorb polar wound exudates and allow oxygen diffusion at the wound bed to accelerate healing. Hydrogel dressings can be designed to prevent bacterial infection, retain moisture, promote optimum adhesion to tissues, and satisfy the basic requirements of biocompatibility. Hydrogel dressings can also be designed to respond to changes in the microenvironment at the wound bed. Hydrogel dressings should promote an appropriate microenvironment for angiogenesis, recruitment of fibroblasts, and cellular proliferation.
The SpyTag/SpyCatcher system is a technology for irreversible conjugation of recombinant proteins. The peptide SpyTag spontaneously reacts with the protein SpyCatcher to form an intermolecular isopeptide bond between the pair. DNA sequence encoding either SpyTag or SpyCatcher can be recombinantly introduced into the DNA sequence encoding a protein of interest, forming a fusion protein. These fusion proteins can be covalently linked when mixed in a reaction through the SpyTag/SpyCatcher system.
Aline Fiona Miller is a Professor of Biomolecular Engineering at the University of Manchester. She specialises in the characterisation of polymer, biopolymer and peptides, using neutron and x-ray scattering, as well as the development of functionalised nanostructures for regenerative medicine and toxicology testing.
Julia Ann Kalow is an assistant professor of chemistry at Northwestern University. She is primarily a synthetic chemist, who works on polymers, photochemistry and tissue engineering. She is interested in synthetic strategies that can turn molecular structure and chemical reactivity into macroscopic properties. She has been awarded the National Science Foundation CAREER Award, Thieme Award and was selected by the University of Chicago as a Rising Star in Chemistry.
Heather D. Maynard is the Dr Myung Ki Hong Professor in Polymer Science at the University of California, Los Angeles. She works on protein-polymer conjugates and polymeric drugs. Maynard is a Fellow of the Royal Society of Chemistry and the American Association for the Advancement of Science.
Jayaraman Sivaguru (Siva) is the Antonia and Marshall Wilson Professor of Chemistry and the Associate Director, Center for Photochemical Sciences at the Department of Chemistry, Bowling Green State University, Bowling Green, Ohio. He is a recipient of 2008 National Science Foundation CAREER Award, 2010 Grammaticakis-Neumann Prize from the Swiss Chemical Society, 2011 young-investigator award from the Inter-American Photochemical Society (I-APS), and 2012-young investigator award from Sigma Xi. His honors also include Excellence in Research award, 2011 Excellence in Teaching award, and the 2012 PeltierAward for Innovation in Teaching. Prof. Siaguru was a visiting young professor at the Global Centre for Excellence at Osaka University, Japan and was a visiting fellow for the Chinese Academy of Sciences President's International Fellowship Initiative in 2018. He is an editor for the Journal of Photochemistry and Photobiology A: Chemistry and from 2020 serves as the co-Editor-in-Chief of Journal of Photochemistry and Photobiology published by Elsevier. He is an international board member of the International Union of Pure and Applied Chemistry (IUPAC) photochemistry symposium.
Kristi Lynn Kiick is the Blue and Gold Distinguished Professor of Materials Science and Engineering at the University of Delaware. She studies polymers, biomaterials and hydrogels for drug delivery and regenerative medicine. She is a Fellow of the American Chemical Society, the American Institute for Medical and Biological Engineering, and of the National Academy of Inventors. She served for nearly eight years as the deputy dean of the college of engineering at the University of Delaware.
Jason Micklefield is a British Biochemist and a professor in the Department of Chemistry at The University of Manchester. His research involves the discovery, characterisation and engineering of biosynthetic pathways to new bioactive natural products, particularly antibiotics. He is also interested in the discovery, structure, mechanism and engineering of enzymes for synthetic applications, including the integration of enzymes with chemocatalysis for telescoping routes to pharmaceuticals and other valuable products.
