Bi-functional nanohybrid comprising a metal oxide-based nanoparticle to the surface of which are covalently coupled one or more, identical or different, groups of formula, wherein said nanoparticle is a natural material, accidentally formed or manufactured containing free particles, in the form of an aggregate or an agglomerate, of which at least 50% of the particles, in the size distribution, have one or more external dimensions between 1 nm and 100 nm, and wherein: said group of formula is as follows: where • Ra1 represents a bioorthogonal 1,2,4,5-tetrazine function of formula wherein R 5 is selected from: ✔ an oxygen atom, a sulphur atom ✔ a -NRp- group with Rp being a hydrogen atom or a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, ✔ one of the following groups R 7 may be absent or when present is selected from: ✔ an oxygen atom, a sulphur atom ✔ a -NRp- group with Rp being a hydrogen atom or a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, ✔ one of the following groups R 5 and R 7 being the same or different, • Rb represents o an halogen atom, o a -ORc or -SRc group with Rc being a hydrogen atom, o a -COORc group with Rc being a hydrogen atom, o a -NRnRz with Rn and Rz being independently from each other a hydrogen atom, a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, a phenyl group or a pyridinyl group o an azide group, o a maleimidyl group, o a (C 1 -C 4)alkynyl group, o an imidazolyl group, o a pyridinyl group, o a 1,2,4-triazine of formula, when Ra1 is a 1,2,4,5-tetrazine of formula with R 8 being either in position 3 or 6 of said 1,2,4-triazine of formula and selected from • X1 and X2, same or different, may be absent or when present represent a spacer selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, isopentyl, and hexyl, with the proviso that the ratio between Ra1 and Rb is equal to 1/1. • Ra1 represents a bioorthogonal 1,2,4,5-tetrazine function of formula wherein R 5 is selected from: ✔ an oxygen atom, a sulphur atom ✔ a -NRp- group with Rp being a hydrogen atom or a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, ✔ one of the following groups R 7 may be absent or when present is selected from: ✔ an oxygen atom, a sulphur atom ✔ a -NRp- group with Rp being a hydrogen atom or a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, ✔ one of the following groups R 5 and R 7 being the same or different, R 5 is selected from: ✔ an oxygen atom, a sulphur atom ✔ a -NRp- group with Rp being a hydrogen atom or a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, ✔ one of the following groups ✔ an oxygen atom, a sulphur atom ✔ a -NRp- group with Rp being a hydrogen atom or a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, ✔ one of the following groups R 7 may be absent or when present is selected from: ✔ an oxygen atom, a sulphur atom ✔ a -NRp- group with Rp being a hydrogen atom or a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, ✔ one of the following groups R 5 and R 7 being the same or different, ✔ an oxygen atom, a sulphur atom ✔ a -NRp- group with Rp being a hydrogen atom or a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, ✔ one of the following groups • Rb represents o an halogen atom, o a -ORc or -SRc group with Rc being a hydrogen atom, o a -COORc group with Rc being a hydrogen atom, o a -NRnRz with Rn and Rz being independently from each other a hydrogen atom, a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, a phenyl group or a pyridinyl group o an azide group, o a maleimidyl group, o a (C 1 -C 4)alkynyl group, o an imidazolyl group, o a pyridinyl group, o a 1,2,4-triazine of formula, when Ra1 is a 1,2,4,5-tetrazine of formula with R 8 being either in position 3 or 6 of said 1,2,4-triazine of formula and selected from o an halogen atom, o a -ORc or -SRc group with Rc being a hydrogen atom, o a -COORc group with Rc being a hydrogen atom, o a -NRnRz with Rn and Rz being independently from each other a hydrogen atom, a (C 1 -C 4)alkyl group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, a phenyl group or a pyridinyl group o an azide group, o a maleimidyl group, o a (C 1 -C 4)alkynyl group, o an imidazolyl group, o a pyridinyl group, o a 1,2,4-triazine of formula, when Ra1 is a 1,2,4,5-tetrazine of formula with R 8 being either in position 3 or 6 of said 1,2,4-triazine of formula and selected from • X1 and X2, same or different, may be absent or when present represent a spacer selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, isopentyl, and hexyl,