Microcapsules Containing pH-Responsive, Fluorescent Polymer-Integrated MoS 2 : An Effective Platform for in Situ pH Sensing and Photothermal Heating.

We report the design of a novel microcapsule platform for in situ pH sensing and photothermal heating, which involves the encapsulation of pH-responsive polymer-coated molybdenum disulfide (MoS2 ) nanosheets (NSs) in microcapsules with an aqueous core and a semipermeable polymeric shell. The MoS2 NSs were functionalized with pH-responsive polymers having fluorescent groups at the distal end to provide pH-sensitive Förster resonance energy transfer (FRET) effect. The pH-responsive polymers were carefully designed to produce a dramatic change in the polymer conformation, which translated to a change in the FRET efficiency near pH 7.0 in response to subtle pH changes, enabling the detection of cancer cells. The pH-sensitive MoS2 NSs were microfluidically encapsulated within semipermeable membranes to yield microcapsules with a uniform size and composition. The microcapsules retained the MoS2 NSs without leakage while allowing the diffusion of small ions and water through the membrane. At the same time, the membranes excluded adhesive proteins and lipids in the surrounding media, protecting the encapsulated MoS2 NSs from deactivation and enabling in situ pH monitoring. Moreover, the encapsulated MoS2 NSs showed high-performance photothermal heating, rendering the dual-functional microcapsules highly suitable for cancer diagnosis and treatment.