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Stimuli-Responsive Polymer Coatings
Published in Sanjay Mavinkere Rangappa, Jyotishkumar Parameswaranpillai, Suchart Siengchin, Polymer Coatings, 2020
Fabrice Ofridam, Mohamad Tarhini, Waisudin Badri, Wei Liao, Noureddine Lebaz, Émilie Gagnière, Denis Mangin, Emilie Dumas, Sami Ghnimi, Abdelhamid Errachid El Salhi, Adem Gharsallaoui, Hatem Fessi, Abdelhamid Elaissari
pH-sensitive polymers are a group of stimuli-responsive polymers that can respond to environment pH through structural and property changes such as surface activity, chain, conformation, solubility, and configuration [46]. Materials referred to as pH-responsive polymers present the property to have potential ionizable groups in their structure. These groups are weak acidic or basic moieties sensible to pH variations and confer the pH sensitivity to the overall molecule [4]. Sensitivity to pH in response to environmental pH modification is made through the acceptance or the release of protons leading to conformational changes and changes in the colloidal behaviour of the polymer, such as flocculation, chain collapse or extension, and/or precipitation of homopolymers [46,47]. pH-responsive polymers can be produced using different polymerization techniques. Emulsion polymerization is the technique used for the preparation of most of the pH-responsive polymers due to the well-controlled size distribution. Moreover, anionic polymerization, group transfer polymerization, stable free radical polymerization, atom transfer radical polymerization, atom transfer radical polymerization, and reversible addition–fragmentation chain-transfer polymerization are other polymerization techniques used for the preparation of pH-responsive polymers [48].
4D bioprinting
Published in Ali Khademhosseini, Gulden Camci-Unal, 3D Bioprinting in Regenerative Engineering, 2018
Qingzhen Yang, Yuan Ji, Feng Xu
The pH-sensitive materials can deform according to the pH value of environment. A typical example is hydrogel composed of pendant-acidic (e.g., carboxylic and sulfonic acids) or -basic (e.g., ammonium salts) groups that could accept or release protons when changing the environmental pH value [28,29]. The dissociation of polymer will sense and respond to the changes of environmental pH, regulating the ion concentration within the hydrogel network. For instance, poly (N, N′-diethylaminoethyl methacrylate) (PDEAEM) tends to become ionized at a low pH value. However, poly (acrylic acid) (PAA) becomes ionized when the pH is high [19,30]. Cationic polyelectrolytes (e.g., PDEAEM) dissolve more or swell more if it is cross-linked at low pH, whereas polyanions (e.g., PAA) dissolve more at high pH. The variation of ion concentration causes the absorbing or releasing of water and thus the deformation of hydrogel. This deformation mechanism is very similar to these thermal-sensitive hydrogels except the trigger in this case is pH value.
Sensing pH for the Perfect Tomato
Published in Denise Wilson, Sensing the Perfect Tomato, 2019
In an electromechanical sensor, pH is converted to a change in one or more mechanical properties of the sensor (e.g., bending, mass, shape, elasticity). These mechanical changes are intermediates that are subsequently converted to an electrical output. One of the most popular designs for an electromechanical sensor is the micro- or nanoscale cantilever beam. The beam is coated with a material that responds to pH by changing size, shape, elasticity, mass, or some other mechanical property. The change in pH-sensitive material deforms the beam and the deformation is measured using piezoresitive, capacitive, or similar techniques to identify pH.
Humic acid embedded chitosan/poly (vinyl alcohol) pH-sensitive hydrogel: Synthesis, characterization, swelling kinetic and diffusion coefficient
Published in Chemical Engineering Communications, 2019
Nergiz Kanmaz, Didem Saloglu, Julide Hizal
Stimuli-responsive hydrogels derived from natural polymers have received significant interest in recent years. To exploit the potential of these hydrogels, smart gels are synthesized to respond to environmental factors such as pH, temperature, light, and electric fields and they are composed of functional groups on polymer structure, which result from non-covalent bonding, hydrophobic interactions, or electrostatic interactions (Kwon et al., 2015). Among them, pH-sensitive hydrogels containing acidic or basic groups that either accept or release protons in response to changes in environmental pH. Such hydrogels have potential applications in drug-delivery systems and new biomaterials for biotechnological applications.
Construction of pH-sensitive sodium alginates/sodium carboxymethyl cellulose/zeolite P composite hydrogel microspheres loaded with potassium diformate
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Bei Fu, ZhongXin Yang, Xing Li, WenQin Xu, GuangHua Pan, NanChun Chen, QingLin Xie, XiuLi Wang
This study demonstrated that composite hydrogel microspheres, which form by embedding KDF and Zeolite P into ALG and CMC and then crosslinking with Ca2+ using the sharp-hole coagulation bath method, is an effective system for controlled drug delivery. The XRD, SEM, and TGA results reveal that Zeolite P can be effectively encapsulated into composite hydrogel microspheres to form a dense three-dimensional network structure and improve the structural stability and thermal stability of the microspheres. The interaction between the ALG and CMC functional groups is conducive to the formation of a double crosslinked network structure, and has good swelling behavior and drug-controlled release behavior in different pH environments. In addition, the prepared hydrogel microspheres are pH-sensitive. The FTIR results revealed that the reduction of the -OH group was caused by the formation of hydrogen bonds between ALG and CMC, and the reduction of -COO– is related to the combination of Ca2+ to form an ‘egg-box’ structure, which acts as a protective layer to prevent drug exudation. In vitro inhibition experiments revealed that the composite hydrogel has a significant inhibition effect on E. coli, S. aureus, and B. subtilis with the inhibition circle size of 32.4 mm, 22.2 mm, and 23.5 mm, respectively. The bacterial growth curve results reveal that different antimicrobial agent concentrations have different effects on bacterial growth. The inhibition agent concentrations of 48 mg/mL and 24 mg/mL exerted significant inhibition effects on the growth of all three bacteria. Hence, the prepared pH-sensitive ALG/CMC/Zeolite P composite hydrogel microspheres have good swelling and slow-release properties and are a good carrier that can be implemented in controlled drug delivery systems.