Lignin biomaterial as agricultural drug carrier

Abstract

The present invention provides lignin nanoparticles containing a hydrophobic active agent and a process for the production of the lignin nanoparticles. The process involves the following steps: (i) dissolving modified lignin and a hydrophobic active agent in an organic solvent having low solubility in water; (ii) combining the solution with water and a surfactant to form a pre-emulsion; (iii) forming an emulsion from the pre-emulsion; and (iv) crosslinking the modified lignin to form the lignin nanoparticles, in which the modified lignin is lignin which is chemically modified to contain at least two functional groups suitable for polymerization and/or crosslinking.

1 . Lignin nanoparticles comprising crosslinked lignin and a hydrophobic active agent. 
     
     
         2 . The lignin nanoparticles of  claim 1 , wherein the lignin nanoparticles are not hollow. 
     
     
         3 . The lignin nanoparticles of  claim 1 , having a number average diameter of from 50 nm to 1 μm as determined by DLS. 
     
     
         4 . The lignin nanoparticles of  claim 1 , obtained by a process comprising the following steps:
 (i) dissolving modified lignin and a hydrophobic active agent in an organic solvent having low solubility in water;   (ii) combining the solution with water and a surfactant to form a pre-emulsion;   (iii) forming an emulsion from the pre-emulsion; and   (iv) crosslinking the modified lignin to form lignin nanoparticles comprising the hydrophobic active agent,   wherein the modified lignin is lignin which is chemically modified to comprise at least two functional groups suitable for polymerization and/or crosslinking.   
     
     
         5 . The lignin nanoparticles of  claim 4 , further comprising after the crosslinking step (iv) a step (v):
 (v) evaporating the organic solvent.   
     
     
         6 . The lignin nanoparticles of  claim 4 , wherein the modified lignin is a lignin which is chemically modified to comprise at least two functional groups per modified lignin molecule which are suitable for polymerization and/or crosslinking, wherein the functional groups are (meth)acrylate groups. 
     
     
         7 . The lignin nanoparticles of  claim 4 , wherein the organic solvent having low solubility in water is selected from hydrocarbon solvents, halogenated hydrocarbons, alcohols and organic compounds having a nitro group. 
     
     
         8 . The lignin nanoparticles of  claim 4 , wherein the hydrophobic active agent is a pesticide. 
     
     
         9 . The lignin nanoparticles of  claim 4 , wherein the organic solvent having low solubility in water employed in step (i) comprises an osmotic pressure agent. 
     
     
         10 . The lignin nanoparticles of  claim 4 , wherein the modified lignin is lignin having terminal double bonds and the crosslinking in step (iv) is achieved by:
 (1) adding an amine compound having at least two amino groups and/or a thiol compound having at least two thiol groups to the emulsion obtained in step (iii) and conducting a Michael addition;   (2) conducting radical polymerization; or   (3) adding a diene to the emulsion obtained in step (iii) and conducting olefin metathesis.   
     
     
         11 . The lignin nanoparticles of  claim 4 , wherein the (meth)acrylated lignin is obtained by one of the following methods:
 (a) reacting OH-groups of lignin with (meth)acrylic anhydride;   (b) reacting OH-groups of lignin with (meth)acryloyl chloride; or   (c) reacting OH-groups of lignin with epichlorohydrin and reacting the reaction product with (meth)acrylic acid.   
     
     
         12 . An aqueous dispersion containing the lignin nanoparticles of  claim 1 . 
     
     
         13 . A method of treating plants against fungal or bactericidal infection comprising applying the lignin nanoparticles of  claim 1 , wherein the hydrophobic active agent is a fungicide or bactericide. 
     
     
         14 . A method of treating a plant against fungal or bactericidal infection by injecting the aqueous dispersion of  claim 12  into the stem of the plant, wherein the hydrophobic active agent is a fungicide or bactericide. 
     
     
         15 . A process for producing the lignin nanoparticles of  claim 1 , comprising the following steps:
 (i) dissolving modified lignin and a hydrophobic active agent in an organic solvent having low solubility in water;   (ii) combining the solution with water and a surfactant to form a pre-emulsion;   (iii) forming an emulsion from the pre-emulsion; and   (iv) crosslinking the modified lignin to form lignin nanoparticles comprising the hydrophobic active agent,   wherein the modified lignin is lignin which is chemically modified to comprise at least two functional groups suitable for polymerization and/or crosslinking.   
     
     
         16 . The process of  claim 15 , further comprising after the crosslinking step (iv) a step (v):
 (v) evaporating the organic solvent.   
     
     
         17 . The process of  claim 15 , wherein the modified lignin is a lignin which is chemically modified to comprise at least two functional groups per modified lignin molecule which are suitable for polymerization and/or crosslinking, wherein the functional groups are (meth)acrylate groups. 
     
     
         18 . The process of  claim 15 , wherein the organic solvent having low solubility in water is selected from hydrocarbon solvents, halogenated hydrocarbons, alcohols and organic compounds having a nitro group. 
     
     
         19 . The process of  claim 15 , wherein the hydrophobic active agent is a pesticide. 
     
     
         20 . The process of  claim 15 , wherein the organic solvent having low solubility in water employed in step (i) comprises an osmotic pressure agent. 
     
     
         21 . The process of  claim 15 , wherein the modified lignin is lignin having terminal double bonds and the crosslinking in step (iv) is achieved by:
 (1) adding an amine compound having at least two amino groups and/or a thiol compound having at least two thiol groups to the emulsion obtained in step (iii) and conducting a Michael addition;   (2) conducting radical polymerization; or   (3) adding a diene to the emulsion obtained in step (iii) and conducting olefin metathesis.   
     
     
         22 . The process of  claim 15 , wherein the (meth)acrylated lignin is obtained by one of the following methods:
 (a) reacting OH-groups of lignin with (meth)acrylic anhydride;   (b) reacting OH-groups of lignin with (meth)acryloyl chloride; or   (c) reacting OH-groups of lignin with epichlorohydrin and reacting the reaction product with (meth)acrylic acid.