Responsive Nanoparticles

Responsive nanoparticles are hollow particles wherein the permeability of the particle changes in response to a change in one or more environmental conditions, such as pH, temperature, light, ionic strength, electric field, magnetic field, solvent composition, etc. The particles could be used for drug delivery, wherein the drug is released from the particle when it reaches the pH of the small intestine, for example.

The particles are made by one of a number of methods from a stimulus-responsive polymer. For example, polyacrylic acid can be made into hollow particles that are contracted at pH less than 5. At a higher pH, the acrylic groups become charged, leading to repulsion of the charged acrylate groups and expansion of the particles. This creates pores through which certain "active agents" can pass. Active agents refers to drugs as well as perfumes, dyes, proteins, genes, etc.

An appropriate polymer is chosen depending upon the type of stimulus that can be applied, i.e. pH, temperature, etc. The intensity of the stimulus required can be varied by selection of the polymer, crosslinking density of the polymer, and inclusion of comonomers.

Amphiphilic Self-Assembling Nanocapsules and Planar Membranes

The nanocapsules and planar membranes are made from amphiphilic copolymers. The copolymers are formed into hollow vesicles or planar membranes through self-assembly methods. The vesicles or planar membranes are stabilized by crosslinking the copolymers to form nanocapsules or stabilized planar membranes. The amphiphilic copolymers can be ABA copolymers, where one of A and B is hydrophilic and the other is hydrophobic. The nanocapsules can be used for a number of purposes. In one embodiment, the nanocapsules are used to deliver a therapeutic, prophylactic, or diagnostic agent to a patient in need thereof. For example, if an ABA copolymer is used, a hydrophilic drug can be encapsulated inside the vesicles or a hydrophobic drug can be encapsulated in the middle layer of the vesicles. Molecules, such as membrane proteins, can be incorporated into the wall of the nanocapsules.

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