Multifunctional hydrogel microsphere with reflection in near-infrared region for in vivo pH monitoring and drug release in tumor microenvironment

Abstract

• Near-infrared (NIR) reflective microspheres for continuous monitoring of pH. • pH monitoring and simultaneous drug release in tumor microenvironment. • Results of continuous pH monitoring correlated to the effectiveness of drug treatment. Tumor microenvironment (TME) is a pivotal factor in tumor progression. Here we report an injectable multifunctional hydrogel microsphere with responsive photonic structure for in vivo monitoring of TME pH. The pH determination is based on measurement of the characteristic reflection peak of the hydrogel microsphere in near-infrared (NIR) region that is sensitive to pH, and decreasing pH leads to a blue shift of the peak. With deep tissue penetration ability of the NIR light, the pH of normal and tumor tissues of mice are continuously monitored in vivo using the microspheres injected subcutaneously. The biocompatibility and the cytotoxicity of the material is investigated based on MTT assays to evaluate its potential for long-term continuous in vivo monitoring of TME pH. A drug for cancer treatment is also preloaded into the hydrogel microsphere for simultaneous drug release in TME and monitoring of the treatment effectiveness of drug by the TME pH tests.