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Introduction to Responsive Membranes
Published in Randeep Singh, Piyal Mondal, Mihir Kumar Purkait, pH-Responsive Membranes, 2021
Randeep Singh, Piyal Mondal, Mihir Kumar Purkait
The materials that respond to an external temperature change by change in their shape or conformation are known as temperature–responsive materials. These materials, when used to synthesize membranes, result in the formation of temperature responsive membranes. These materials contain a characteristic feature of having a lower critical solution temperature (LCST). For example, poly(N-isopropylacrylamide), commonly termed PNIPAAM, shows a characteristic LCST of 32°C [2]. Further, due to its thermo-responsive property, it is widely used for the synthesis of various temperature-responsive materials including membranes [1–3]. Additionally, poly-vinylcaprolactam (PVCL) is also a commonly used thermo-responsive polymer. The use of temperature-responsive materials with other polymers result in an increase or decrease in their LCST. The temperature-responsive materials are also used to synthesize dual- or multi-responsive materials by using materials that respond to a different external stimuli with the potential for different applications [1].
Stimuli-Responsive Polymeric Nanomaterials
Published in Klaus D. Sattler, 21st Century Nanoscience – A Handbook, 2020
One of many useful applications of these technologies is cancer therapy. For example, thermo-sensitive amphiphilic copolymer poly(2-(2-methoxyethoxy) ethyl methacrylate-co-oligo(ethylene glycol)methacrylate)-co-2-(dimethylamino) ethyl methacrylate-b-poly(D, L-lactideco-glycolide) can be assembled into core–shell structured nanoparticles with co-encapsulation of two cytotoxic drugs doxorubicin and paclitaxel (NP-DT), and absorption of small interfering RNAs (siRNA) against surviving (NP-DTS).123 This copolymer exhibits low toxicity, low immunogenicity, and thermal sensitivity owing to the presence of polyethylene glycol(PEG) and PNIPAM.124 The LCST can be precisely tuned during polymerization by changing the amount of chain transfer agent and MEO2MA and OEGMA ratio. The LCST was designed slightly above physiological temperature which upon body contact triggers the collapse of nanoparticles to release the drug. The outer layers of the drug-loaded nanoparticles can be modified with polydopamine (PDA) (named NPDTS-PDA), preventing premature burst release and NIR laser-triggered nanoparticle collapse. This process is shown in Figure 2.5a–c.
Nanogels for Brain Targeting
Published in Raj K. Keservani, Anil K. Sharma, Rajesh K. Kesharwani, Nanocarriers for Brain Targeting, 2019
Nagarjun Rangaraj, Sunitha Sampathi
Lower critical solution temperature (LCST) is the temperature below which the polymer is soluble and above which the polymer shows phase transition from soluble state (random coil form) to an insoluble state (collapsed or globule form) (Chaterji et al., 2007). There exists an inverse relationship between the temperature and the solubility hence these gels are called negative temperature responsive nanogels (Zha et al., 2011). Conversely, the temperature above which the polymers solubilize is called as Upper critical solution temperature (UCST). These polymers are called positive temperature sensitive owing to their direct relation between the temperature and solubility (Bajpai et al., 2008). Polymers exhibiting LCST and UCST behavior are quoted in Table 15.3.
Synthesis of temperature-responsive P(vinyl pyrrolidone-co-methyl methacrylate) micelle for controlled drug release
Published in Journal of Dispersion Science and Technology, 2022
Soo Chan Park, Garima Sharma, Jin-Chul Kim
Figure 3 shows the OD at 600 nm of P(VP-co-MMA)(100/0) solution, P(VP-co-MMA)(95/5) solution, P(VP-co-MMA) (94/6) solution, and P(VP-co-MMA)(92.5/7.5) solution while the solution was heated from 20 to 50 °C. The P(VP-co-MMA)(100/0) solution exhibited almost zero OD in the full temperature range tested. This indicates the high water solubility of the copolymer in the experimental temperature range. It was observed that the increase in temperature did not show any effect on the solubility of P(VP-co-MMA) (100/0) polymer. The P(VP-co-MMA)(95/5) solution exhibited almost zero OD in the range of 20–40 °C. However, its OD increased when the temperature was increased from 40 to 50 °C, indicating that heating the solution above 40 °C makes the copolymer insoluble in the aqueous solution due to a phase transition that results in its precipitation. The temperature after which copolymer becomes hydrophobic is known as LCST point. As previously evidenced, when VP monomer copolymerizes with a hydrophobic monomer it results in the synthesis of copolymer that exhibit LCST phenomenon.[26] In accordance, the LCST of P(VP-co-MMA)(95/5) synthesized in this study seemed to be about 40 °C, as indicated by the increase in the OD after this temperature point.
Near-infrared triggered on-demand local anesthesia using a jammed microgels system
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Qiying Pang, Jia Zhao, Shuchi Zhang, Xiaoqing Zhang
GOs in microgels were not only used to physically cross-link P(NIPAM-co-PEG), but also took the responsibility to realize photo thermal conversion, because GOs possess high absorption and conduction efficiency to light in the NIR region [31]. Combination of GOs in hydrogels can endow the hydrogel with NIR-responsive ability, and has been applied for optical control switch [31], intelligent drive [32], cell release [33] and dimming materials [34]. At the same time, PNIPAM, as well as its copolymers are well-known thermo-sensitive polymers, possessing the LCST that associated with its swelling and collapse. When the temperature is lower than LCST, PNIPAM is hydrophilic and swells in H2O. While when the temperature is higher than LCST, PNIPAM molecular chains change their conformation and become hydrophobic, thus collapse and de-swell. It is worth noting that the LCST of PNIPAM could be controlled by the copolymerization of APEG according to the present study. Together with its biocompatibility, PNIPAM has received much attention as a biomaterial [35]. Thus, combination of GOs and PNIPAM in the present study contributed to the NIR-response of the system, realizing the phototriggered local anesthesia in vivo.