Nanoscale & Nanoscale Advances Blog

In this article, Scheutjens-Fleer self-consistent field (SF-SCF) theory simulations were used to accurately predict the position of a nanoparticle attached to the end-group of a responsive polymer chain surrounded by a majority of non-responsive polymer chains in a mixed brush system.

Certain stimuli such as pH or temperature can be used to create a defined ‘on-off’ switch between a protected ‘off’ state, where the responsive polymer chain is contracted thus burying the nanoparticles well within the non-responsive components, or an ‘on’ state where the nanoparticle is exposed to the medium through swelling of the responsive polymer chains.

The solvent quality was parameterised by the Flory-Huggins interaction parameter (χ) and for nearly all investigated systems there was a sharp transition at the so-called critical χ value between the on-off state.   Design variables for mixed polymer brushes such as grafting density, chain length and nanoparticle size were investigated and all had an effect on the critical χ value, with a larger particle size and grafting density leading to an increase in χ. Fixing the polymer chain length for both responsive and non-responsive polymer chains led to the most optimal switching.

The authors are planning to develop materials from these findings and use the mixed polymer brush-nanoparticle systems as rapidly responsive (bio)sensors with single molecule sensitivity.

Responsive polymer brushes for controlled nanoparticle exposure
Namik Akkilic, Frans A. M. Leermakers and Wiebe M. de Vos
Nanoscale, 2015,7, 17871-17878, DOI: 10.1039/C5NR05150A

Dr Mike Barrow is a guest web writer for the Nanoscale blog, he currently works as a Postdoctoral Researcher at the University of Liverpool. Twitter: @mikesyb

Researchers from Chinese Academy of Sciences have investigated the use of molecular beacons (MBs) for the simultaneous detection of multiple microRNA (miRNA) biomarkers.

The MBs were immobilized onto gold nanoparticles (AuNPs) via poly-adenine (poly-A) spacer. In addition, the authors used short oligonucleotides (oligos) consisting of 5 As in order to fill the gaps between MBs on the AuNP surface to ensure stability in salt solutions and obtain greater fluorescence signals.

MBs with 3 different fluorophores were employed in order to enable multiplexed detection of miRNAs in simulated serum samples. The authors reported that each MB specifically bound to its corresponding miRNA target in the presence of 10% fetal bovine serum (FBS), thereby demonstrating the applicability of this method for real biological sample detection.

In recent years, miRNA has emerged as a potential biomarker for many types of diseases, such as cancer, neurological disorders and cardiovascular disease. The need for rapid and sensitive assays for miRNA detection is therefore of great interest. Wang et al. have demonstrated a step in this direction with the research presented here.

Elaborately designed diblock nanoprobes for simultaneous multicolor detection of microRNAs
Chenguang Wang, Huan Zhang, Dongdong Zeng, Wenliang Sun, Honglu Zhang, Ali Aldalbahi, Yunsheng Wang, Lili San, Chunhai Fan, Xiaolei Zuo and Xianqiang Mi
Nanoscale, 2015,7, 15822-15829, DOI: 10.1039/C5NR04618A

Dr Lee Barrett is a guest web writer for the Nanoscale blog. Lee is currently a postdoctoral researcher in the Centre for Molecular Nanometrology at the University of Strathclyde. His research is currently focused on the development of nanoparticle-based sensors and surface enhanced Raman scattering (SERS). Follow him on twitter @L_Bargie