A composition comprising nanoparticulate constructs wherein said nanoparticulate constructs comprise: a) an amphiphilic stabilizer, and b) a conjugate of the formula active − linker n − hydrophobic moiety wherein n is an integer of 1-100; "active" refers to a compound that has a desired activity; "linker" is a divalent residue of an organic molecule, which divalent residue is selectively cleavable by reduction or hydrolysis upon exposure to a predefined stimulus to, thereby, control the release of said active from the hydrophobic moiety and the nanoparticulate construct, the cleavage being either within the divalent residue, at the bond that couples the linker to the active, or at the bond that couples the linker to the hydrophobic moiety; and "hydrophobic moiety" refers to the residue of an organic molecule that is insoluble in aqueous solution; and i) wherein the one or more active is a therapeutic agent or a diagnostic agent; or ii) wherein the one or more active is a compound other than a pharmaceutical agent and other than a diagnostic agent; wherein the hydrophobic moiety is a polymer having a molecular weight between 800 and 200,000 g/mole or is a natural product selected from the group consisting of hydrophobic vitamins, carotenoids, retinols, cholecalciferol, calcitriol, hydroxycholecalciferol, ergocalciferol, α-tocopherol, α-tocopherol acetate, α-tocopherol nicotinate, and estradiol, and the amphiphilic stabilizer is a copolymer having a hydrophilic region and a hydrophobic region, which copolymer is a graft, block or random amphiphilic copolymer and has a molecular weight between 1,000 g/mole and 50,000 g/mole. a) an amphiphilic stabilizer, and b) a conjugate of the formula active − linker n − hydrophobic moiety wherein n is an integer of 1-100; "active" refers to a compound that has a desired activity; "linker" is a divalent residue of an organic molecule, which divalent residue is selectively cleavable by reduction or hydrolysis upon exposure to a predefined stimulus to, thereby, control the release of said active from the hydrophobic moiety and the nanoparticulate construct, the cleavage being either within the divalent residue, at the bond that couples the linker to the active, or at the bond that couples the linker to the hydrophobic moiety; and "hydrophobic moiety" refers to the residue of an organic molecule that is insoluble in aqueous solution; and i) wherein the one or more active is a therapeutic agent or a diagnostic agent; or ii) wherein the one or more active is a compound other than a pharmaceutical agent and other than a diagnostic agent; wherein the hydrophobic moiety is a polymer having a molecular weight between 800 and 200,000 g/mole or is a natural product selected from the group consisting of hydrophobic vitamins, carotenoids, retinols, cholecalciferol, calcitriol, hydroxycholecalciferol, ergocalciferol, α-tocopherol, α-tocopherol acetate, α-tocopherol nicotinate, and estradiol, and the amphiphilic stabilizer is a copolymer having a hydrophilic region and a hydrophobic region, which copolymer is a graft, block or random amphiphilic copolymer and has a molecular weight between 1,000 g/mole and 50,000 g/mole. wherein n is an integer of 1-100; "active" refers to a compound that has a desired activity; "linker" is a divalent residue of an organic molecule, which divalent residue is selectively cleavable by reduction or hydrolysis upon exposure to a predefined stimulus to, thereby, control the release of said active from the hydrophobic moiety and the nanoparticulate construct, the cleavage being either within the divalent residue, at the bond that couples the linker to the active, or at the bond that couples the linker to the hydrophobic moiety; and "hydrophobic moiety" refers to the residue of an organic molecule that is insoluble in aqueous solution; and i) wherein the one or more active is a therapeutic agent or a diagnostic agent; or ii) wherein the one or more active is a compound other than a pharmaceutical agent and other than a diagnostic agent; i) wherein the one or more active is a therapeutic agent or a diagnostic agent; or ii) wherein the one or more active is a compound other than a pharmaceutical agent and other than a diagnostic agent; wherein the hydrophobic moiety is a polymer having a molecular weight between 800 and 200,000 g/mole or is a natural product selected from the group consisting of hydrophobic vitamins, carotenoids, retinols, cholecalciferol, calcitriol, hydroxycholecalciferol, ergocalciferol, α-tocopherol, α-tocopherol acetate, α-tocopherol nicotinate, and estradiol, and the amphiphilic stabilizer is a copolymer having a hydrophilic region and a hydrophobic region, which copolymer is a graft, block or random amphiphilic copolymer and has a molecular weight between 1,000 g/mole and 50,000 g/mole.