Abstract
Introduction
Thermoresponsive polymers have been widely investigated in modern drug delivery and gene delivery systems, due to their potential to load and release the payload by simply modifying local temperature [1]. Previous work by some of us has shown that the thermoresponsive copolymers poly(N-isopropylacrylamide)n-block-poly((3-acrylamidopropyl) trimethylammonium chloride)m (PNIPAAMn-b-PAMPTMA(+)m) can efficiently deliver DNA and siRNA to HeLa [2] and HT1080 cells [3]. The transfection efficiency and cytotoxicity were highly dependent on the length and ratio of the two blocks (n:m) [2,3]. In anticancer therapy, such polymers may be able to deliver drugs precisely at the tumour site by local and transient thermal treatment [1]. Having this in mind, in this work, we took the first step towards expanding the scope of use of the PNIPAAMn-b-PAMPTMA(+)m copolymers by investigating their cytotoxicity in human cancer cell lines and in a normal breast cell line.
Materials and methods
The copolymers (n:m ratio 48:6, 48:10 and 65:20) were dissolved in varying concentrations in cell culture medium, as described before [2] and were incubated at 37 °C with each of the tested cell lines for 6 h. After that, the medium was replaced, and the cells were incubated for 48 h/37 °C. The viability of cells was measured by the MTT cytotoxicity assay. Untreated cells were used as negative control (representing 100% viability). Cell lines: HeLa (cervical cancer), HCC1806 (breast cancer) and MCF10A (non-tumorigenic breast epithelial cell line).
Results
In this preliminary study the cytotoxicity of the PNIPAAMn-b-PAMPTMAm(+) copolymers was shown to be dependent on the polymer concentration, n:m ratio and cell line. MCF10A cells were very tolerant to the presence of the copolymer 48:6, even at the highest concentration (Figure 1), followed by HeLa and HCC1806. Discussion and conclusions: The low toxicity shown particularly for the non-tumorigenic cell line but higher toxicity towards the cancer cell lines makes the tested copolymers highly appealing as drug carriers in anti-cancer therapy.
Figure 1.
Cell viability in the presence of the 48:6 (n:m) copolymer. Mean ± SD. Comparisons were made at the same cell line at the immediately precedent concentration (*p < 0.05) and for the same concentration between lines (#p < 0.05).
Acknowledgements
This work received funding from the FCT-PTDC/BIM-MEC/6631/2014 and Egas Moniz, CRL.
References
- 1.Calejo MT, Sande SA, Nyström B.. Thermoresponsive polymers as gene and drug delivery vectors: architecture and mechanism of action. Expert Opin. Drug Deliv. 2014;10:1669–1686. [DOI] [PubMed] [Google Scholar]
- 2.Calejo MT, Cardoso AM, Kjøniksen A-L, et al. Temperature-responsive cationic block copolymers as nanocarriers for gene delivery. Int J Pharm. 2013;448(1):105–114. [DOI] [PubMed] [Google Scholar]
- 3.Cardoso AM, Calejo MT, Morais CM, et al. Application of thermoresponsive PNIPAAM-b-PAMPTMA diblock copolymers in siRNA delivery. Mol Pharma. 2014;11(3):819–827. [DOI] [PubMed] [Google Scholar]