Dual Nanofriction Force Microscopy/Fluorescence Microscopy Imaging Reveals the Enhanced Force Sensitivity of Polydiacetylene by pH and NaCl

Jianlu Zheng; Seiko Jo; Jiali Chen; Bratati Das; Levente Juhasz; Horacio Cabral; Kaori Sugihara

doi:10.1021/acs.analchem.3c01433

Dual Nanofriction Force Microscopy/Fluorescence Microscopy Imaging Reveals the Enhanced Force Sensitivity of Polydiacetylene by pH and NaCl

Anal Chem. 2023 Aug 1;95(30):11335-11341. doi: 10.1021/acs.analchem.3c01433. Epub 2023 Jul 19.

Authors

Jianlu Zheng¹, Seiko Jo¹, Jiali Chen¹, Bratati Das¹, Levente Juhasz², Horacio Cabral³, Kaori Sugihara¹

Affiliations

¹ Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo 153-8505, Japan.
² Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland.
³ Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.

PMID: 37465896
DOI: 10.1021/acs.analchem.3c01433

Abstract

Polydiacetylene (PDA) is a popular mechanochromic material often used in biosensing. The effect of its headgroup-headgroup interactions on thermochromism such as pH or salt concentration dependency has been extensively studied before; however, their effect on mechanochromism at the nanoscale is left unstudied. In this work, nanofriction force microscopy and fluorescence microscopy were combined to study the effect of pH and ionic strength on the polydiacetylene (PDA) force sensitivity at the nanoscale. We found that the increase in pH from 5.7 to 8.2 caused an 8-fold enhancement in force sensitivity. The elevation of NaCl concentration from 10 to 200 mM also made the PDA 5 times more force-sensitive. These results suggest that the PDA force sensitivity at the nanoscale can be conveniently enhanced by "pre-stimulation" with pH or ionic strength.