Related Experiment Video
Updated: Jun 14, 2026

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications
Published on: February 6, 2016
Proton-Resistant Quantum Dots: Stability in Gastrointestinal Fluids and Implications for Oral Delivery of
Aaron M Mohs1, Hongwei Duan, Brad A Kairdolf
1Departments of Biomedical Engineering and Chemistry, Emory University and Georgia Institute of Technology, 101 Woodruff Circle NE, Suite 2001, Atlanta, Georgia 30322, USA.
Abstract:
Semiconductor quantum dots (QDs) have shown great promise as fluorescent probes for molecular, cellular and in-vivo imaging. However, the fluorescence of traditional polymer-encapsulated QDs is often quenched by proton-induced etching in acidic environments. This is a major problem for QD applications in the gastrointestinal tract because the gastric (stomach) environment is strongly acidic (pH 1-2). Here we report the use of proton-resistant surface coatings to stabilize QD fluorescence under acidic conditions. Using both hyperbranched polyethylenimine (PEI) and its polyethylene glycol derivative (PEG grafted PEI), we show that the fluorescence of core-shell CdSe/CdS/ZnS QDs is effectively protected from quenching in simulated gastric fluids. In comparison, amphiphilic lipid or polymer coatings provide no protection under similarly acidic conditions. The proton-resistant QDs are found to cause moderate membrane damage to cultured epithelial cells, but PEGylation (PEG grafting) can be used to reduce cellular toxicity and to improved nanoparticle stability.
Related Concept Videos
Bioavailability Enhancement: Drug Stability Enhancement and GI Retention
Factors Affecting Dissolution: Drug Permeability, Stability and Stereochemistry
Factors Affecting Dissolution: Drug pKa, Lipophilicity and GI pH
A drug's pKa and the pH of the gastrointestinal (GI) tract play crucial roles in drug...
Oral Drug Delivery Systems: Delayed-Release Systems
Factors Influencing Drug Absorption: Physicochemical Parameters
Enhanced drug absorption can be achieved by reducing particle sizes and increasing surface areas, thereby facilitating...
Bioavailability Enhancement: Drug Permeability Enhancement

