Formulation of Diblock Polymeric Nanoparticles through Nanoprecipitation Technique

Summary

This article describes a nanoprecipitation method to synthesize polymer-based nanoparticles using diblock co-polymers. We will discuss the synthesis of diblock co-polymers, the nanoprecipitation technique, and potential applications.

Abstract

Nanotechnology is a relatively new branch of science that involves harnessing the unique properties of particles that are nanometers in scale (nanoparticles). Nanoparticles can be engineered in a precise fashion where their size, composition and surface chemistry can be carefully controlled. This enables unprecedented freedom to modify some of the fundamental properties of their cargo, such as solubility, diffusivity, biodistribution, release characteristics and immunogenicity. Since their inception, nanoparticles have been utilized in many areas of science and medicine, including drug delivery, imaging, and cell biology^1-4. However, it has not been fully utilized outside of "nanotechnology laboratories" due to perceived technical barrier. In this article, we describe a simple method to synthesize a polymer based nanoparticle platform that has a wide range of potential applications.

The first step is to synthesize a diblock co-polymer that has both a hydrophobic domain and hydrophilic domain. Using PLGA and PEG as model polymers, we described a conjugation reaction using EDC/NHS chemistry⁵ (Fig 1). We also discuss the polymer purification process. The synthesized diblock co-polymer can self-assemble into nanoparticles in the nanoprecipitation process through hydrophobic-hydrophilic interactions.

The described polymer nanoparticle is very versatile. The hydrophobic core of the nanoparticle can be utilized to carry poorly soluble drugs for drug delivery experiments6. Furthermore, the nanoparticles can overcome the problem of toxic solvents for poorly soluble molecular biology reagents, such as wortmannin, which requires a solvent like DMSO. However, DMSO can be toxic to cells and interfere with the experiment. These poorly soluble drugs and reagents can be effectively delivered using polymer nanoparticles with minimal toxicity. Polymer nanoparticles can also be loaded with fluorescent dye and utilized for intracellular trafficking studies. Lastly, these polymer nanoparticles can be conjugated to targeting ligands through surface PEG. Such targeted nanoparticles can be utilized to label specific epitopes on or in cells^7-10.

Protocol

1. Synthesis of PLGA-b-PEG polymer

1. Poly(D,L-lactide-co-glycolide) (PLGA) with terminal carboxylate groups (PLGA-carboxylate) is dissolved in any solvent for PLGA (as mentioned in materials section) at a concentration of 5mM. PLGA can be dissolved at this concentration with gentle stirring.
2. Both NHS (molecular weight 115.09) and EDC (molecular weight 191.7) are dissolved in the PLGA solution at a concentration of 25mM. (Both EDC and NHS are added in a stoichiometric excess of 5 times compared to PLGA). PLGA-carboxylate is converted into PLGA-NHS by adding EDC and NHS to PLGA-carboxylate solution with gentle stirring for about 1 hour.
3. The....

Discussion

The nanoprecipitation method using diblock co-polymers represents a simple, fast method to engineer polymeric nanoparticles. The resulting nanoparticles are composed of a hydrophobic core which can be utilized for the delivery of poorly soluble compounds. The surface hydrophilic layer enables excellent aqueous solubility while providing a moiety for potential further conjugation to a targeting ligand.

There are many nanoparticle platforms, including liposomes, polymeric nanoparticles, dendrime.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
EDC	Thermo Fisher Scientific, Inc.	22980	Conjugation Reagent
NHS	Thermo Fisher Scientific, Inc.	24500	Conjugation Reagent
amine-PEG-carboxylate	Laysan Bio Inc.	Nh2-PEG-CM-5000	Polymer (Can use any PEG MW, 5000 is listed here)
PLGA-carbxylate	Lactel	B6013-2	Polymer
Dichloromethane (DCM)	Sigma-Aldrich	34856	Solvent
Acetonitrile >99% purity	Sigma-Aldrich	34851	Solvent
Methanol >99% purity	Sigma-Aldrich	34860	Wash