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Analytical and Bioanalytical Chemistry

, Volume 406, Issue 22, pp 5369–5378 | Cite as

Preparation of QP4VP-b-LCP liquid crystal block copolymer and its application as a biosensor

  • Muhammad Omer
  • Soo-Young ParkEmail author
Research Paper

Abstract

The interface between nematic liquid crystal, 4-cyano-4′-pentylbiphenyl (5CB), and water in a transmission electron microscopy (TEM) grid cell coated with QP4VP-b-LCP (quaternized poly(4-vinylpyridine) (QP4VP) and poly(4-cyanobiphenyl-4′-oxyundecylacrylate) (LCP)) was examined for protein and DNA detection. QP4VP-b-LCP was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Quaternization of P4VP with iodomethane (CH3I) made it a strong cationic polyelectrolyte and allowed QP4VP-b-LCP to form complexes with oppositely charged biological species. Several proteins, such as bovine serum albumin (BSA), hemoglobin (Hb), α chymotrypsinogen-A (ChTg), and lysozyme (LYZ), were tested for nonspecific protein detection. By injecting the protein solutions into the TEM grid cell, the initial homeotropic orientation of the TEM grid cell changed to a planar orientation above their isoelectric points (PIs) due to electrostatic interactions between QP4VP (+charge) and proteins (−charge), which did not occur below the PIs of the tested proteins. Their minimum concentrations at which the homeotropic to planar configurational change (H-P change) occurred were 0.01, 0.02, 0.03, and 0.04 wt.% for BSA, ChTg, Hb, and LYZ, respectively. One of the strong anionic polyelectrolytes, deoxyribonucleic acid (DNA) (due to the phosphate deoxyribose backbone) was also tested. A H-P change was observed with as little as 0.0013 wt.% salmon sperm DNA regardless of the pH of the cell. A H-P change occurred in 5CB and was observed by polarized optical microscopy. This simple and inexpensive setup for nonspecific biomaterial detection provides the basic idea for developing effective selective biosensors by introducing specific binding groups, such as the aptamer and antibody.

Keywords

Strong cationic polyelectrolyte QP4VP-b-LCP Protein DNA RAFT polymerization Biosensor 

Notes

Acknowledgments

This work was supported by the National Research Foundation of Korea (NRF-2011-0020264).

Supplementary material

216_2014_7900_MOESM1_ESM.pdf (265 kb)
ESM 1 (PDF 264 kb)

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Department of Polymer ScienceKyungpook National UniversityDaeguSouth Korea

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