In this study a new pH-responsive nanogel probe containing a complementary non-radiative resonance energy transfer (NRET) fluorophore pair is investigated and its ability to act as a versatile probe of network-related changes in three hydrogels demonstrated. Fluorescent sensing using NRET is a powerful method for studying relationships between Angstrom length scale structure and macroscopic properties of soft matter. Unfortunately, inclusion of NRET fluorophores into such materials requires material-specific chemistry. The nanogel probes (NGPh/An) were prepared by copolymerization of methyl methacryate (MMA), methacrylic acid (MAA), ethyleneglycol dimethacrylate (EGDMA), (9-phenanthryl)methyl methacrylate (Ph) and (9-anthryl)methacrylate (An). The NGPh/An dispersions were pH-responsive (Fig. 1a) and also showed changes in their photoluminescence (PL) as the particles swelled (Fig. 1b and c) as a consequence of NRET. The intensity ratios also showed reversibility that was not affected by aggregation (Fig. 1d). Ratiometric PL data for the gels labelled with the nanogel probes enabled pH-triggered swelling and de-swelling to be studied as well as Ca2+-triggered collapse and solute release. PL measurements during compression of a nanogel probe-labelled nanocomposite gel demonstrated mechanochromic behavior and strain sensing. The new nanogel probes have excellent potential for provide a versatile ratiometric fluorescent platform for studying pH and strain within gels.

A responsive nanogel probe for ratiometric fluorescent sensing of pH and strain in hydrogels

255th National Meeting (2018)

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