A method for encapsulating a water soluble agent comprising: dissolving the water soluble agent and a copolymer in a polar process solvent to form a first process solution; and continuously mixing the first process solution with a nonprocess solvent to form a mixed solution from which a nanoparticle assembles and precipitates, wherein the copolymer comprises at least one region that is more polar and at least one region that is less polar, wherein the nonprocess solvent is less polar than the polar process solvent, wherein the nanoparticle comprises a core and a shell, wherein the core comprises the more polar region of the copolymer and the water soluble agent, wherein the shell comprises the less polar region of the copolymer that is soluble in the nonprocess solvent, and wherein the mixing causes no more than 20 percent by volume of the polar process solvent to phase separate from the mixed solution, wherein the water soluble agent is a biologic material, an amino acid, a peptide, a protein, DNA, RNA, a saccharide, glutathione, tryptophan, a lysozyme, glucagon-like peptide-1 (GLP-1), a small molecule therapeutic, tobramycin, vancomycin, an imaging agent, eosin, eosin Y, tartrazine, a metal chelate, a gadolinium chelate, and gadolinium diethylene triamine pentaacetic acid (GD-DTPA), or combinations, wherein the at least one more polar region of the copolymer comprises at least one anionic more polar region, wherein the at least one anionic more polar region comprises poly(acrylic acid), hyaluronic acid, poly(glutamic acid), poly(aspartic acid), or combinations; wherein the at least one less polar region of the copolymer comprises poly(n-butyl acrylate), poly(lactic acid), poly(lactic-co-glycolic acid) (PLGA), or combinations. dissolving the water soluble agent and a copolymer in a polar process solvent to form a first process solution; and continuously mixing the first process solution with a nonprocess solvent to form a mixed solution from which a nanoparticle assembles and precipitates, wherein the copolymer comprises at least one region that is more polar and at least one region that is less polar, wherein the nonprocess solvent is less polar than the polar process solvent, wherein the nanoparticle comprises a core and a shell, wherein the core comprises the more polar region of the copolymer and the water soluble agent, wherein the shell comprises the less polar region of the copolymer that is soluble in the nonprocess solvent, and wherein the mixing causes no more than 20 percent by volume of the polar process solvent to phase separate from the mixed solution, wherein the water soluble agent is a biologic material, an amino acid, a peptide, a protein, DNA, RNA, a saccharide, glutathione, tryptophan, a lysozyme, glucagon-like peptide-1 (GLP-1), a small molecule therapeutic, tobramycin, vancomycin, an imaging agent, eosin, eosin Y, tartrazine, a metal chelate, a gadolinium chelate, and gadolinium diethylene triamine pentaacetic acid (GD-DTPA), or combinations, wherein the at least one more polar region of the copolymer comprises at least one anionic more polar region, wherein the at least one anionic more polar region comprises poly(acrylic acid), hyaluronic acid, poly(glutamic acid), poly(aspartic acid), or combinations; wherein the at least one less polar region of the copolymer comprises poly(n-butyl acrylate), poly(lactic acid), poly(lactic-co-glycolic acid) (PLGA), or combinations.