Lower critical solution temperature LCST , thermoresponsive

Thermoresponsive acrylamide co-polymers were also used to alter the physicochemical and biopharmaceutical properties of avidin. Similar to PEG, the acrylamide co-polymers with a lower critical solution temperature (LCST) of about 37 °C were conjugated to the protein amino groups. The polymers were conjugated either by polymer multipoint attachment using polyfunctional polymers or by single chain attachment using end-chain monoactivated polymer. In both cases, the polymer conjugation was found to produce bioactive derivatives with reversible thermal character (Fig. 11.12). 

Among stimuli-responsive or thermoresponsive polymer microspheres, poly(N-isopropylacrylamidc) (PNIPA) was investigated most intensively. Cross-linked PNIPA is a thermosensitive hydrogel which undergoes a volume phase transition at its lower critical solution temperature (LCST) of around 34 °C. Several authors reported the synthesis of PNIPA microspheres [68-73]. 

Thermoresponsive Polymers. Poly[(ethylene glycol) methacrylate] (PEGMA) and poly(iV-isopropylacrylamide) (PNIPAam) are well-studied polymers for imparting thermoresponsive properties to cationic vectors. These polymers undergo a phase transition (from random coil to globular form) at a lower critical solution temperature (LCST) near the... 

Apart from these properties, the release kinetics can be manipulated in such a way that drug release occurs due to a trigger from an environmental stimulus like pH, temperature, etc. [88]. The thermoresponsive graft co-polymeric 5-FU-loaded nanoparticles made from chitosan-g-poly(A -vinylcaprolactam), prepared by an ionic crosslinking method, showed a lower critical solution temperature (LCST) at 38 C, with a prominent in vitro drug release above LCST [89]. Camptothecin-loaded polyfiV-isopropylacrylamide) (PNIPAAm)/chitosan nanoparticles were... 

The inclusion of the thermoresponsive poly(Af-isopropylacrylamide) (PNIPAM) constituent suggests the advantages of (1) degradation mechanism modulation of biodegradable polymers, (2) cytotoxicity reduction of polycationic polymers, (3) thermally localizing medication to target sites after systemic administrations while their lower critical solution temperature (LCST) is tailored to temperatures between 37°C (body temperature) and 42°C (used habitually in clinical hyperthermia), and (4) drugs released at diverse profiles in answer to stimuli such as temperature, pH, etc. [69]. 

Surface-confined PNIPAM has been one of the most studied polymer brushes due to its thermoresponsive behavior, and thus its application in medicine, membrane technologies, and catalysis [20]. PNIPAM shows lower critical solution temperature (LCST) in aqueous solutions at 32°C. At temperatures below the LCST, PNIPAM brushes are hydrophilic and hydrogen bonds with... 

SI-IMP has been used for synthesis of different types of stimuli-responsive polymer brushes that are responsive to several external stimuli, such as pFI, temperature, and ionic strength [28,58-65]. Because materials interact with their surroundings via their interfaces, the ability to fashion soft interfacial layers and tune the range, extent, and type of physicochemical interactions across interfaces is central to a variety of applications. Rahane et al. carried out sequential SI-IMP of two monomers to create bilevel poly(methacrylic acid)-Woc/c-poly(N-isopropylacrylamide) (PMAA-b-PNIPAM) block copolymer brushes that can respond to multiple stimuli [28]. They observed that each strata in the bilevel PMAA-b-PNIPAM brush retained its customary responsive characteristics PMAA being a "weak" polyelectrolyte swells as pH is increased and the thermoresponsive PNIPAM block collapses as temperature is raised through the volume phase transition temperature due to its lower critical solution temperature (LCST) behavior. As a result of ions added to make buffer solutions of various pH and because of the effect of surface confinement, the swollen-collapse transition of the PNIPAM layer occurs at a... 

The most popular examples of switchable substrates are the thermosensitive surfaces that change from hydrophobic to hydrophilic substrates upon small temperature changes. Thermoresponsive polymers, which exhibit a lower critical solution temperature (LCST) in water close to body temperature, are the mostly used responsive materials to produce surfaces with tunable cell attachment/detachment (da Silva et /., 2007). 

PNIPAAm is a widely studied thermoresponsive polymer that exhibits a lower critical solution temperature (LCST) [51, 52]. Below the LCST, the polymer is expanded and hydrophihc and is thus soluble in water. Above this critical temperature, there is an abrupt phase transition leading to a collapsed and hydrophobic polymeric structure, which renders the polymer insoluble in water [53-55]. The LCST of... 

A thermoresponsive polymer ean also use another form of energy, that is, heat. A thermoresponsive polymer is a polymer that dissolves in water but undergoes phase separation if heated to a certain temperature as a result of dehydration. This polymer possesses a lower critical solution temperature (LCST). The thermoresponsivity of acrylamide-type thermoresponsive polymers is shown in Table 1 [16]. The transition temperature (LCST) ranges from 5-70°C. The transition temperature can be readily controlled by copolymerizing two types of monomers [17] (see Fig. 2). 

Thermoresponsive polymers are promising for biomedical applications, including as smart dmg/gene delivery systems, injectable tissue engineering scaffolds, and cell culture and separation sheets/ However, either the most frequently studied thermoresponsive polymers such as poly(N-isopropylacrylamide) (PNlPAAm), oligopoly(ethylene glycol), poly(N,N -diethylacrylamide), and poly(2-carboxyisopropylacrylamide) are non-degradable or the lower critical solution temperature (LCST) cannot be tuned. 

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