Silica-based nanoparticles (SiNPs) are presented to harvest complex membrane proteins, which have been embedded into unilammelar polymersomes via in vitro membrane assisted protein synthesis (iMAP). Size-optimized SiNPs have been surface-modified with polymer-targeting antibodies, which are employed to harvest the protein-containing polymersomes. The polymersomes mimic the cellular membrane. They are chemically defined and preserve their structural-functional integrity as virtually any membrane protein species can be synthesized into such architecture via the ribosomal context of a cellular lysate. The SiNPs resemble 'heavy leg irons' catching the polymersomes in order to enable gravity-based generic purification and concentration of such proteopolymersomes from the crude mixture of cellular lysates.