Introduction to Bioresponsive Polymers
Deepa H. Patel in Bioresponsive Polymers, 2020
Modern bioresponsive materials are gradually developed to interface with biological tissues in well-defined ways. Significant classes of bioresponsive materials are those that are highly hydrated-hydrogels. Bioresponsive hydrogel polymers, which have been developed to engaged in a conversation with their biological surroundings. A biological incident takes place upon interaction with the material, which can be accomplished by introducing target moiety that binds specific biomolecules into the material structure. These target moieties offer instructions to manage or direct biological interactions. Hydrogels made up of elastic cross-linked networks with interstitial spaces that include as much as 90–99% w/w water. Hydrogels are prepared by different methods such as chemical polymerization or by physical self-assembly of synthetic or naturally occurring building blocks.
Injectable Scaffolds for Bone Tissue Repair and Augmentation
Naznin Sultana, Sanchita Bandyopadhyay-Ghosh, Chin Fhong Soon in Tissue Engineering Strategies for Organ Regeneration, 2020
Injectable scaffolds for bone tissue regeneration are particularly interesting, not only because the use of these materials can potentially avoid the surgical interventions to implant the scaffolds at defective/fractured areas, but they can also reassemble within a short interval and can fill any irregularly shaped defects once inside the body (Hou et al. 2004, Jin et al. 2009, Naahidi et al. 2017). An injectable system also takes the advantage of a more homogeneous distribution of bioactive molecules within the matrix, that can readily be obtained by virtue of the scaffold components being in suspension or solution before solidification in vivo. The promising injectable materials that can be used as bone scaffolds are primarily based on hydrogel (Temenoff and Mikos 2000, Hou et al. 2004, Nourmohammadi et al. 2016) and paste (Migliaresi et al. 2007). Hydrogels are soft materials, having cross-linked hydrophilic networks that can absorb large quantities of water (or biological fluids) while maintaining their original structure (Ahmed and Aggor 2010, Jung et al. 2017, Portnov et al. 2017). When hydrogels are injected, they can readily wet all surfaces of the injured site and create a low-density aqueous cavity that contains the components necessary for bone tissue regeneration. Paste based injectable scaffolds are usually developed from calcium phosphate cements (CPC) and are also considered to be clinically important owing to their biocompatibility, bioactivity, ease of handling, moldability, and injectability (Li et al. 2009).
3D In Vitro/Ex Vivo Systems
Anthony J. Hickey, Sandro R.P. da Rocha in Pharmaceutical Inhalation Aerosol Technology, 2019
Hydrogels have evolved from being constructed of natural materials to synthetic polymers. This transition allowed the researcher to have greater control over different components of the hydrogel system such as absorbency and flexibility to increase the accuracy of their models (Ahmed 2015). Hydrogels are widely utilized in the field of regenerative medicine because they possess many properties of tissue. Recently, three-dimensional hydrogels have been created from an advanced network of polymer chains and water filling the open spaces between the macromolecules. These systems are multi-component in comparison to the original natural and synthetic hydrogels. They are hydrophilic and have been made to accurately resemble living tissue because they can absorb large amounts of water. They are also porous and possess an overall soft consistency. As a result, these three-dimensional hydrogel models can successfully represent the tissue macro and microenvironment. Thus, researchers can gain a more accurate and comprehensive understanding of the cells being studied (Caló and Khutoryanskiy 2015).
A review on the treatment of intimal hyperplasia with perivascular medical devices: role of mechanical factors and drug release kinetics
Published in Expert Review of Medical Devices, 2023
Ankur J. Raval, Jigisha K. Parikh, Meghal A. Desai
Hydrogels are a group of materials mainly consisting of hydrophilic three-dimensional network that readily captures and holds a large amount of water in its polymeric structure. The water content ranges within 70–90%, similar to the tissues in physical terms, and gives them excellent biocompatibility [47]. The hydrophilic network provides a high capacity to encapsulate drugs with similar physicochemical properties. Upon cross-linking, their physical properties change drastically, making them stiff, and their mechanical properties resemble solids which can further be tuned based on the end-user application. For example, the elastic modulus could be adjusted in the range of 0.5 kPa to 5 MPa to resemble the mechanical strength of various soft tissues [48,49]. Based on the end-use application, different hydrogel properties, like size, architectural network, and function, could be tuned to develop unique drug delivery systems. These properties could be adjusted by the material involved (e.g. polymer/copolymers, block-co-polymers), its concentration, molecular weight, and structure [50].
Polysaccharide-based hydrogels for drug delivery and wound management: a review
Published in Expert Opinion on Drug Delivery, 2022
Dhruv Sanjanwala, Vaishali Londhe, Rashmi Trivedi, Smita Bonde, Sujata Sawarkar, Vinita Kale, Vandana Patravale
Hydrogels are three-dimensional crosslinked networks of hydrophilic polymers, synthesized using physical or chemical crosslinking, and are capable of absorbing large quantities of water or aqueous fluids. Hydrogels can entrap large volumes of water (in some cases, several times their own weight) in their crosslinked networks and swell greatly. This high hydrophilicity of hydrogels can be attributed to the abundant hydrophilic groups present in the polymeric chains. Hydrogels can be fabricated from synthetic as well as natural polymers. Synthetic polymer-based hydrogels are usually non-biodegradable as opposed to natural hydrogels, which are environment-friendly and easily degradable. Natural polymers commonly used for fabricating hydrogels include biological macromolecules such as proteins (collagen, gelatin), polysaccharides (cellulose, chitosan, hyaluronic acid (HA), agarose), and nucleic acids. Among these, carbohydrate polymers are used extensively, mainly due to their abundance, nontoxicity, renewability, and high biocompatibility. Moreover, they can be chemically modified to accurately mimic various body tissues [1–3]. Table 1 lists the most common natural polysaccharides and their semisynthetic derivatives used to fabricate hydrogels for biomedical applications.
Application of nanotechnology in management and treatment of diabetic wounds
Published in Journal of Drug Targeting, 2022
Filipa Mascarenhas-Melo, Maria Beatriz S. Gonçalves, Diana Peixoto, Kiran D. Pawar, Victoria Bell, Vivek P. Chavda, Hajra Zafar, Faisal Raza, Ana Cláudia Paiva-Santos
Hydrogels, which are very common therapeutic and cosmetic dosage forms used in wound repair, also face inherent challenges to their use. Not only are more studies needed to improve their efficacy, to monitor their toxicity and biodegradation, but also, their industrial-scale production is still defiant, mainly due to the high purity levels required [89]. Given this, nanofibers also face some disadvantages. To avoid a burst release and control the delivery of various molecules in the same nanofiber membrane, their arrangement, porosity, and orientation should be optimised. Most of the studies mentioned above were conducted on a small population of diabetic patients or on experimental animals. Therefore, more studies have to be performed to achieve representative conditions. Moreover, to obtain realistic results in humans more clinical trials are necessary [33]. Biodegradability is also an extremely relevant strength of these strategies that should also be considered [21].