Poly(N-isopropylacrylamide-co-N-vinylpyrrolidone) thermoresponsive microspheres: The low drug loading ensures the pulsatile release mechanism

Abstract

Poly(N-isopropylacrylamide-coN -vinylpyrrolidone) (poly(NIPAAm-co-NVP)) with a co-monomer molar ratio in copolymer of 91.5/8.5 (NIPAAm/NVP) was synthesized as an interesting thermosensitive material possessing a sharp phase transition at 36°C under simulated physiological conditions. The effect of the co-monomer molar ratio as well as of the ionic strength and nature of ions on the lower critical solution temperature (LCST) was investigated. Cross-linked poly(NIPAAm-co-NVP) thermoresponsive microspheres were synthesized by the suspension polymerization technique respecting the same NIPAAm/NVP molar ratio as for linear polymer. The microspheres were loaded with the model drug diclofenac (DF) by the solvent evaporation method; differential scanning calorimetry (DSC) demonstrates a dispersion of drug crystals within the polymeric matrix. The DF release rate is deeply influenced by the drug loading degree. Only microspheres with low DF loading are able to release the bioactive compound through a pulsatile mechanism.

Thermoresponsive polymers and their biomedical application in tissue engineering – a review

“…2h). 78 The adjustable LCST behaviour of the derivatives of PNIPAM and copolymers indicated that it is highly promising to be applied in biomedical field, because the transition temperature can be tuned. This might be relevant for different tissue environments.…”

Activity of Povidone in Recent Biomedical Applications with Emphasis on Micro- and Nano Drug Delivery Systems

“…Finally, the microspheres were loaded with a model drug—diclofenac. The release of that drug through the pulsatile mechanism was investigated [ 96 ]. In another try, a new microgel based on acrylamide (AAM), 1-vinyl-2-pyrrolidone (NVP), and 2-(diethylamino)ethyl methacrylate (DEAEMA) was prepared.…”

“…( b ) LCST profiles of poly(NIPAAm- co -NVP) nanoparticles under simulated physiological conditions showing influence of pVP on LCST of polymers. Reproduced with permission from [ 96 ], Budapest University of Technology and Economics, 2019 ( c ) TEM images of pVP functionalized gold nanoparticles with curcumin and scheme of possible conjugation of Cur with pVP coated Au-Nps. Reproduced with permission from [ 62 ], Elsevier, 2012.…”

Smart Supra- and Macro-Molecular Tools for Biomedical Applications

“…Interesting results can be obtained when choosing comonomers of a more different chemical nature. For example, the copolymerization of NIPAAm with N-vinylpyrrolidone (NVP) in a 91.5:8.5 ratio affords thermoresponsive systems with an LCST value of 36 • C in simulated physiological conditions [46]. Because the two comonomers have weak ionizable units, the LCST is sensible to the surrounding ionic strength and pH, higher LCST values (37.3 • C) being obtained in a simulated gastric fluid environment (pH 1.2).…”