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Hydrogels with Ubiquitous Roles in Biomedicine and Tissue Regeneration
Published in Harishkumar Madhyastha, Durgesh Nandini Chauhan, Nanopharmaceuticals in Regenerative Medicine, 2022
Priyanka, Pooja A Chawla, Aakriti, Viney Chawla, Durgesh Nandini Chauhan, Bharti Sapra
In general, three main components of the hydrogel preparation are monomer, initiator, and cross-linker (Figure 10.2). Any technique that is used to put in order a cross-linked polymer is used to prepare a hydrogel also. Preparation methods of both natural and synthetic origin hydrogels are described in Figure 10.3 (Ahmed, 2015).
Bioresponsive Hydrogels for Controlled Drug Delivery
Published in Deepa H. Patel, Bioresponsive Polymers, 2020
Tamgue Serges William, Dipali Talele, Deepa H. Patel
Hydrogels are cross-linked polymer networks that are able to swell in a liquid medium. Hydrogels may absorb from 10–20% up to thousands of times of their dry weight in water. When a dry hydrogel starts to absorb water, the initial water molecules moving into the matrix will hydrate the most polar, hydrophilic groups, leading to primary bound water. This leads to the swelling of hydrogel linkage and exposes hydro-phobic groups which also intermingle with water molecules, resulting in hydrophobically-bound water or secondary bound water. Primary and secondary bound water are often merged and solely called as total bound water. Progressively as the network swells, if the network chains are degradable, the gel will initiate to disintegrate and dissolve at a rate depending on its composition. Various methods are employed to evaluate the relative amounts of bound and free water contained in the hydrogel, such as differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) [17].
Neuroprotection
Published in Glenn J. Jaffe, Paul Ashton, P. Andrew Pearson, Intraocular Drug Delivery, 2006
Dennis W. Rickman, Melissa J. Mahoney
Hydrogels, insoluble yet water-swellable cross-linked polymer networks have also received considerable interest as three-dimensional matrices supporting cell growth and differentiation. In most cases, gelation can be induced directly, in the presence of cells, resulting in uniform cell density throughout the implant. The combined high water content and elasticity of polymer hydrogels lead to many tissue-like properties of these materials, making them ideal candidates for tissue engineering. For example, hydrogels of poly[N-2-(hydroxypropyl)methacrylamide] (PHPMA) loaded with BDNF producing fibroblasts inserted into cavities made in the optic tract resulted in increased in-growth of axons into implants. Retinal axons exhibited a complex branching pattern and they regrew the greatest distances within implants containing BDNF after four to eight weeks (139). Similar effects have been observed for gels implanted into lesioned cavities in the cerebral hemispheres and spinal cord (140).
Hydrogels for localized chemotherapy of liver cancer: a possible strategy for improved and safe liver cancer treatment
Published in Drug Delivery, 2022
Jianyong Ma, Bingzhu Wang, Haibin Shao, Songou Zhang, Xiaozhen Chen, Feize Li, Wenqing Liang
Some major hydrogel classes are formed as a result of the preparation method. Following are the example of these:Homopolymeric hydrogels: Monomers are the fundamental constituents of polymer networks, and homopolymeric hydrogels are networks composed entirely of a single monomer species (Iizawa et al., 2007). Cross-linked structures can be found in homopolymers depending on the nature of their monomer and the method used for polymerization.Copolymeric hydrogels: Copolymeric hydrogels are composed of two or more distinct monomer species that contain at least one hydrophilic component. The polymer network may have a random, block, or alternating configuration (Yang et al., 2002).Multipolymer interpenetrating polymeric hydrogel (IPN), a type of hydrogel, is composed of two independent cross-linked synthetic and/or natural polymer components held together in a network form. One component of semi-IPN hydrogel is a cross-linked polymer, while the other is a non-cross-linked polymer (Maolin et al., 2000).
In situ gelling and mucoadhesive polymers: why do they need each other?
Published in Expert Opinion on Drug Delivery, 2018
Forouhe Zahir-Jouzdani, Julian Dominik Wolf, Fatemeh Atyabi, Andreas Bernkop-Schnürch
Click chemistry comprises practical and reliable reactions allowing for modular synthesis of larger molecules. ‘Spring loaded’ reactants form carbon-heteroatom bonds via different mechanisms such as strain-promoted azide-alkyne cycloaddition (SPAAC), [3 + 2] cycloaddition or Diels-Alder cycloaddition. Within the last years this approach has aroused more and more interest for the development of in situ gelling systems. For example, azadibenzocyclooctyne and azide functionalized PEG chains were used to generate cross-linked polymer networks via SPAAC. Without need for catalysts or external stimuli these systems gelled within seconds and mechanical as well as rheological properties were adjustable by varying the molecular mass and degree of substitution of the PEG [45]. Truong et al. [11] chose a dual-click approach to achieve a tough double network under physiological conditions. A loose network was generated via tetrazine-norbornene inverse-electron demand Diels-Alder cycloaddition between norbornene-functionalized CS and PEG-ditetrazine, whereas nucleophilic thiol-alkyne addition between PEG-dithiol and PEG-tetraalkyne formed the dense network. In this way, they were able to prepare a hydrogel exhibiting high mechanical strength as well as small pore sizes being suitable for a range of applications.
Exploring new frontiers in drug delivery with minimally invasive microneedles: fabrication techniques, biomedical applications, and regulatory aspects
Published in Expert Opinion on Drug Delivery, 2023
Niha Sultana, Ayesha Waheed, Asad Ali, Samreen Jahan, Mohd Aqil, Yasmin Sultana, Mohd. Mujeeb
Ceramics with a wide range of options, such as calcium phosphate dehydrate [Brushite (CaHPO4.2H2O)], can also be employed. A calcium sulfate dihydrate called gypsum [CaSO4.2H2O] can also be utilized [44]. An organically modified ceramic known as Ormocer® has been in use recently. It is a cross-linked polymer with three-dimensional structure [45]. Polymerization allows for the creation of polymers with a wide range of properties by combining different types of organic components. They are made using a technology called micro-molding. Ceramic slurry is exposed to micro-molding, and this technology has the potential to be scaled up because it is easy to reproduce, cheaper, and more cost-effective.