“Molecular Buoys” – Hollow Silica Microspheres for Buoyancy-Assisted Cell Separation

Separation of cells and microorganisms from complex biological mixtures is a critical first step in many analytical applications ranging from clinical diagnostics to environmental monitoring for food and waterborne contaminants. Yet, existing techniques for cell separation are plagued by high reagent and/or instrumentation costs that limit their use in many remote or resource-poor settings, such as field clinics or developing countries.

We developed an innovative approach to isolate infectious pathogens from biological fluids using buoyant hollow silica microspheres that function as “molecular buoys” for affinity-based target capture and separation by floatation. In this process, antibody functionalized glass microspheres are mixed with a complex biological sample, such as stool. When mixing is stopped, the target-bound, low-density microspheres float to the air/liquid surface, which simultaneously isolates and concentrates the target analytes from the sample matrix.

Molecular buoy


The microspheres are highly tunable in terms of size, density, and surface functionality for targeting diverse analytes with separation times of ≤ 2 minutes in viscous solutions. This low-cost method for phenotypic cell/pathogen separation from complex mixtures is expected to have widespread use in clinical diagnostics as well as basic research.

This work is funded by NSF Partnership for Research and Education in Materials (DMR-1205670) and the Research Triangle Materials Research Science and Engineering Center (DMR-1121107).