Visualization of the pH Response through Autofluorescent Poly(styrene-alt-N-maleimide) Polyelectrolyte Brushes

Abstract

Polyelectrolyte brushes can undergo reversible conformational transitions in response to changes in environmental pH and ionic strength. Therefore, they offer great potential for the design of “smart” surfaces and surface-based sensing devices. Herein, we report weak acidic polyelectrolyte brushes with pH-dependent autofluorescence based on alternating copolymers of styrene and tailor-made N-maleimides, which exhibit “clusteroluminescence” due to the through-space conjugation of π-chromophoric subfluorophores. Swelling behavior of the polyelectrolyte brushes was evaluated as a function of pH via in-solution atomic force microscopy (AFM) analyses. The correlation between the pH-induced conformational transitions and autofluorescence was confirmed with confocal laser scanning microscopy (CLSM) and two-photon laser scanning microscopy. Poly(styrene-alt-N-maleimide)-based well-defined, stable polyelectrolyte brushes, generating optical signals from conformational changes without conventional fluorophores, may enable the design of sensors and optoelectronic devices.

Advancing Glucose Sensing Through Auto‐Fluorescent Polymer Brushes: From Surface Design to Nano‐Arrays

“…However, during the transition from collapsed to extended state, the segments of the polymer chains enter the diluted state due to hydration and electrostatic repulsion which limits intra‐ and interchain interactions and consequently leads to weak emissions. [ 41 ]…”

“…However, during the transition from collapsed to extended state, the segments of the polymer chains enter the diluted state due to hydration and electrostatic repulsion which limits intra-and interchain interactions and consequently leads to weak emissions. [41] In this study, two-photon laser scanning microscopy was used in combination with atomic force microscopy to perform fluorescence characterizations and investigate pH-and glucoseresponsive behavior of the boronic acid integrated brush-based nanoplatforms. The glucose as a cis-diol reacts readily with the boronic ester through the formation of a cyclic ester.…”

“…Previously, we demonstrated that polymer brushes built from auto‐fluorescent polymers can generate optical signals from pH‐induced conformational changes without conventional fluorophores. [ 41 ] In this work, we extend this methodology to design and fabricate patterned glucose‐responsive surfaces by integrating auto‐fluorescent poly(styrene‐ alt ‐maleic anhydride) (pSMA) copolymer brushes with boronic acid receptors.…”

Fluorescence-readout as a powerful macromolecular characterisation tool

“…[334][335][336][337] With the demand for simple and versatile surface modications, polymer brushesmore generally dened as thin lms of polymer chains tethered at one end to a surface 338 have become particularly attractive to achieve nely tuned surface properties including amphiphilic, stimuli-sensitive, antifouling, lubricating and conductive. [339][340][341][342][343][344][345][346] Two approaches -'graing to' and 'graing from'are generally used for the preparation of polymer brushes. The former functioning by graing pre-formed polymer chains to the surface, while the latter is a bottom-up approach where polymer chains are grown directly from the substrate via surface-initiated polymerisation.…”

“…The spatial read-out capability of uorescence microscopy further allows to spatially resolve the polymer brush conformation. [372][373][374][375][376] Polymer brush surfaces with the ability to change the conformation and structure of polymer chains in response to external stimuli hold signicant potential for applications in drug delivery, self-healing coatings, sensors and actuators. 339,364 These external stimuli include temperature, light, applied force and a variety of chemical stimuli, such as solvent type, pH and ionic strength.…”