Assessment of cytotoxicity of (N-isopropyl acrylamide) and poly(N-isopropyl acrylamide)-coated surfaces.

Marta A Cooperstein,Heather E Canavan

doi:10.1186/1559-4106-8-19

Abstract

Poly(N-isopropyl acrylamide) (pNIPAM) is one of the most popular stimulus-responsive polymers for research. It is especially of great interest in the field of tissue engineering. While it is known that the NIPAM monomer is toxic, there is little conclusive research on the cytotoxicity of the polymer. In this work, the relative biocompatibility of the NIPAM monomer, pNIPAM, and pNIPAM-coated substrates prepared using different polymerization (free radical and plasma polymerization) and deposition (spin coating and plasma polymerization) techniques was evaluated using appropriate cytotoxicity tests (MTS, Live/Dead, plating efficiency). Four different mammalian cell types (endothelial, epithelial, smooth muscle, and fibroblasts) were used for the cytotoxicity testing. The pNIPAM-coated surfaces were evaluated for their thermoresponse and surface chemistry using X-ray photoelectron spectroscopy and goniometry. We found that while cell viability on pNIPAM surfaces decreases when compared to controls, the viability also seems to be deposition type dependent, with sol–gel based pNIPAM surfaces being the least biocompatible. Long term experiments proved that all pNIPAM-coated surfaces were not cytotoxic to the four cell types evaluated in a direct contact test. Plating efficiency experiments did not show cytotoxicity. Cellular sensitivity to pNIPAM and to the NIPAM monomer varied depending on cell type. Endothelial cells consistently showed decreased viability after 48 hours of exposure to pNIPAM extracts and were more sensitive than the other cell lines to impurities in the polymer.

Highlights

Poly(N-isopropyl acrylamide) is a thermoresponsive polymer that undergoes a phase change in a physiologically relevant temperature range
We examine the cytotoxicity of the polymerized form of NIPAM (pNIPAM) monomer, pNIPAM, and pNIPAM films
Highlighted in the box is the region between 5.5 and 6.5 ppm, in which peaks for hydrogens adjacent to double bonded carbons usually appear. These peaks are clearly visible in the spectrum of the monomer, as N-isopropyl acrylamide (NIPAM) has 3 hydrogens adjacent to two carbons joined with a double bond

Summary

Introduction

Poly(N-isopropyl acrylamide) (pNIPAM) is a thermoresponsive polymer that undergoes a phase change in a physiologically relevant temperature range. Mammalian cells can be cultured on pNIPAM at 37°C. When the temperature is lowered to below pNIPAM’s lower critical solution temperature (LCST, 32°C), the polymer’s chains extend and cells detach in intact sheets [1,2]. This detachment method is preferred to enzymatic digestion or mechanical scraping [3,4,5]. Mechanical scraping can result in broken cell sheets and destroyed cells, while enzymatic digestion does not preserve the cell sheet, breaking it into single cells.

Methods

Results

Conclusion