Preparation and Investigation of Poly (N-isopropylacrylamide-acrylamide) Membranes in Temperature Responsive Drug Delivery

Document Type : Original Article


1 Department of Pharmaceutics, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran

2 Pharmaceutical Research Center, Avicenna Institute, Mashhad University of Medical Sciences, Mashhad, Iran


Physiological changes in the body may be utilized as potential triggers for controlled drug delivery. Based on these mechanisms, stimulus-responsive drug delivery has been developed.
Materials and Methods
In this study, a kind of poly (N-isopropylacrylamide-acrylamide) membrane was prepared by radical copolymerization. Changes in swelling ratios and diameters of the membrane were investigated in terms of temperature. On-off regulation of drug permeation through the membrane was then studied at temperatures below and above the phase transition temperature of the membrane. Two drugs, vitamin B12 and acetaminophen were chosen as models of high and low molecular weights here, respectively.
It was indicated that at temperatures below the phase transition temperature of the membrane, copolymer was in a swollen state. Above the phase transition temperature, water was partially expelled from the functional groups of the copolymer. Permeation of high molecular weight drug models such as vitamin B12 was shown to be much more distinct at temperatures below the phase transition temperature when the copolymer was in a swollen state. At higher temperatures when the copolymer was shrunken, drug permeation through the membrane was substantially decreased. However for acetaminophen, such a big change in drug permeation around the phase transition temperature of the membrane was not observed.
According to the pore mechanism of drug transport through hydrogels, permeability of solutes decreased with increasing molecular size. As a result, the relative permeability, around the phase transition temperature of the copolymer, was higher for solutes of high molecular weight.


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