Abstract
Poly(N-isopropylacrylamide) (PNIPAM)-based thermosensitive hydrogels demonstrate great potential in biomedical applications. However, they have inherent drawbacks such as low mechanical strength, limited drug loading capacity and low biodegradability. Formulating PNIPAM with other functional components to form composited hydrogels is an effective strategy to make up for these deficiencies, which can greatly benefit their practical applications. This review seeks to provide a comprehensive observation about the PNIPAM-based composite hydrogels for biomedical applications so as to guide related research. It covers the general principles from the materials choice to the hybridization strategies as well as the performance improvement by focusing on several application areas including drug delivery, tissue engineering and wound dressing. The most effective strategies include incorporation of functional inorganic nanoparticles or self-assembled structures to give composite hydrogels and linking PNIPAM with other polymer blocks of unique properties to produce copolymeric hydrogels, which can improve the properties of the hydrogels by enhancing the mechanical strength, giving higher biocompatibility and biodegradability, introducing multi-stimuli responsibility, enabling higher drug loading capacity as well as controlled release. These aspects will be of great help for promoting the development of PNIPAM-based composite materials for biomedical applications.
Highlights
Hydrogels are based on using hydrophobic and hydrophilic components to form three-dimensional (3D) network structures under physical and/or chemical interactions, which can imbibe a large amount of water molecules and freeze their movements [1,2,3,4]
Composite hydrogelsPNIPAM-based formulation can help to optimizehydrogels the properties of the wound dressings to have biomedical areas, from drug delivery to tissue engineering and wound dressings
A specific advantage the merits of moisture retaining, enhanced adhesiveness, high comfortableness, temperatureis that PNIPAM has a lower critical solution temperature (LCST) of about 32 ◦ C and can be triggered by body temperature to give a triggered precise drug delivery, long time inhibition of infection and allowing supervision of the phase transition, which makes PNIPAM-based hydrogels highly suitable for practical applications
Summary
Hydrogels are based on using hydrophobic and hydrophilic components to form three-dimensional (3D) network structures under physical and/or chemical interactions, which can imbibe a large amount of water molecules and freeze their movements [1,2,3,4]. Based on NIPAM monomer; b molar ratio of dextrin to PNIPAM; c weight ratio of the second polymer block to NIPAM; G0 : Storage modulus; Y: Young’s modulus; CS: Compressive strength; NAC: N-acetyl-cysteine; Alg:Allyl-substituted alginate Another effective method for modulating the properties of a hydrogel is incorporation of another polymer in the hydrogel matrix to produce IPN hydrogels. Wang et al [55,56] and Alvarez-Lorenzo et al [57] have used chitosan to composite with PNIPAM to fabricate either full-IPN hydrogels or semi-IPN hydrogels For these hydrogels, the properties such as gelation rate, thermoresponsive phase transition, swelling dynamics, drug loading capacity and release profile can be effectively modulated, which are promising for the design and preparation of PNIPAM-based hydrogels for biomedical applications. Some comprehensive review papers on the related topics are available [5,15,18,20] and we will not provide an exhaustive discussion of the topic here
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