Tumor necrosis factor (TNF)-functionalized nanostructured particles for the stimulation of membrane TNF-specific cell responses

Most members of the tumor necrosis factor (TNF) ligand family occur in both a membrane-bound and a soluble form, which can possess differential bioactivities. The aim of this work was the construction of a synthetic-biological hybrid system consisting of chemically nanostructured core-shell particles with a diameter of 100 nm, 1 μm, or 10 μm and the cytokine TNF to obtain a tool that mimics the bioactivity of naturally occurring membrane-bound TNF. Synthetic core-shell nanoparticles consisting of an inorganic silica core and an ultrathin organic shell bearing a maleimide group at the shell surface which allowed for a covalent and site-directed coupling of CysHisTNF mutants were prepared. The TNF mutants were modified at the N-terminus by PCR cloning by introducing a His-Tag for purification and a free cysteine group for reaction with the particle-attached maleimide group. The resulting nanostructured hybrid particles initiated strong TNF receptor type 2 specific responses, otherwise only seen for the membrane-bound form of TNF, but not the soluble cytokine, thus clearly demonstrating new and membrane TNF-like properties of the bioconjugated soluble TNF.