The disclosure provides, methods for preparing scavenging particles, as well as methods for attaching capture agents to the particles. The disclosure further provides compositions that bind to and inhibit the biological activity of soluble biomolecules, as well as pharmaceutical compositions thereof. The compositions may comprise a plurality of particles that specifically bind a target, such as a soluble biomolecule or a biomolecule on the surface of a pathogen, to inhibit the target (or pathogen) from interacting with other molecules or cells. Also provided herein are a number of applications (e.g., therapeutic applications) in which the compositions are useful.