Thermoresponsive Polymers for Biomedical Applications

Thermoresponsive Polymers for Biomedical Applications

Received: 1 July 2011 / Accepted: 29 July 2011 / Published: 3 August 2011 | Mark A. Ward * and Theoni K. Georgiou
Thermoresponsive polymers, a class of "smart" materials that can respond to changes in temperature, have gained significant scientific interest due to their potential applications in various fields. This review focuses on the synthesis and use of thermoresponsive polymers for biomedical applications, including drug delivery, gene delivery, and tissue engineering. The main applications are categorized based on the 3-dimensional structure of the polymers, such as hydrogels, interpenetrating networks, micelles, crosslinked micelles, polymersomes, films, and particles. Hydrogels, which are polymer networks dispersed in water, can be covalently linked or physically gelled. Covalently linked hydrogels exhibit a change in swelling degree with temperature, while physically gelled hydrogels show a sol-gel transition. Thermoresponsive polymers like poly(N-isopropylacrylamide) (PNIPAAm) are commonly used due to their LCST close to body temperature. PNIPAAm can be modified to alter its LCST by copolymerizing with hydrophilic or hydrophobic monomers. In drug delivery, thermoresponsive polymers are used to control the release of drugs at specific temperatures. For example, PNIPAAm gels shrink and entrap drugs when heated above the LCST, leading to a controlled release. Gene delivery studies have also utilized thermoresponsive polymers to enhance transfection efficiency by changing the temperature during complexation and incubation. Tissue engineering applications include using thermoresponsive polymers as substrates for cell growth and proliferation and as injectable gels for in situ scaffold formation. For instance, PNIPAAm hydrogels can be injected into the body and form physical gels upon heating, encapsulating cells within a 3D structure. Interpenetrating networks (IPNs) and micelles are other classes of thermoresponsive structures used for drug and gene delivery. IPNs consist of two covalently linked polymer networks that interact physically, while micelles are formed by block copolymers and can encapsulate hydrophobic drugs. Crosslinked micelles and polymersomes are also explored for their unique properties. Crosslinked micelles can be formed by selectively crosslinking specific blocks within the micelle, while polymersomes provide a hydrophilic interior and exterior, suitable for encapsulating both hydrophilic and hydrophobic molecules. Films and particles are another form of thermoresponsive polymers used in biomedical applications. Films can be used for sustained drug release, while particles can be used for intracellular delivery or as drug delivery devices with magnetic targeting capability. In conclusion, thermoresponsive polymers have found diverse applications in biomedical fields, including tissue engineering and drug/gene delivery. Their ability to respond to temperature changes offers significant advantages in controlling the release of therapeutic molecules and enhancing cellular interactions.Thermoresponsive polymers, a class of "smart" materials that can respond to changes in temperature, have gained significant scientific interest due to their potential applications in various fields. This review focuses on the synthesis and use of thermoresponsive polymers for biomedical applications, including drug delivery, gene delivery, and tissue engineering. The main applications are categorized based on the 3-dimensional structure of the polymers, such as hydrogels, interpenetrating networks, micelles, crosslinked micelles, polymersomes, films, and particles. Hydrogels, which are polymer networks dispersed in water, can be covalently linked or physically gelled. Covalently linked hydrogels exhibit a change in swelling degree with temperature, while physically gelled hydrogels show a sol-gel transition. Thermoresponsive polymers like poly(N-isopropylacrylamide) (PNIPAAm) are commonly used due to their LCST close to body temperature. PNIPAAm can be modified to alter its LCST by copolymerizing with hydrophilic or hydrophobic monomers. In drug delivery, thermoresponsive polymers are used to control the release of drugs at specific temperatures. For example, PNIPAAm gels shrink and entrap drugs when heated above the LCST, leading to a controlled release. Gene delivery studies have also utilized thermoresponsive polymers to enhance transfection efficiency by changing the temperature during complexation and incubation. Tissue engineering applications include using thermoresponsive polymers as substrates for cell growth and proliferation and as injectable gels for in situ scaffold formation. For instance, PNIPAAm hydrogels can be injected into the body and form physical gels upon heating, encapsulating cells within a 3D structure. Interpenetrating networks (IPNs) and micelles are other classes of thermoresponsive structures used for drug and gene delivery. IPNs consist of two covalently linked polymer networks that interact physically, while micelles are formed by block copolymers and can encapsulate hydrophobic drugs. Crosslinked micelles and polymersomes are also explored for their unique properties. Crosslinked micelles can be formed by selectively crosslinking specific blocks within the micelle, while polymersomes provide a hydrophilic interior and exterior, suitable for encapsulating both hydrophilic and hydrophobic molecules. Films and particles are another form of thermoresponsive polymers used in biomedical applications. Films can be used for sustained drug release, while particles can be used for intracellular delivery or as drug delivery devices with magnetic targeting capability. In conclusion, thermoresponsive polymers have found diverse applications in biomedical fields, including tissue engineering and drug/gene delivery. Their ability to respond to temperature changes offers significant advantages in controlling the release of therapeutic molecules and enhancing cellular interactions.
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