Polymeric micelles are extensively studied carriers for the delivery of poorly water-soluble drugs. Upon exposure to aqueous medium, the amphiphilic molecules are spontaneously self-assembled into supramolecular core/shell structures, and water-insoluble drugs can be loaded into the hydrophobic cores. Suitable characteristics of the tumor microenvironment and particularly, angiogenesis render the design of optimally tailored polymeric micelles suitable for anti-cancer drug delivery. Polymeric micelles are core-shell structures synthesized form amphiphilic block copolymers [7,8]. PDF | Though much progress has been made in drug delivery systems, the design of a suitable carrier for the delivery of hydrophobic drugs is.


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  • Polymeric Micelles for Drug Delivery | Insight Medical Publishing
  • Polymeric micelles for drug delivery.
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Polymeric micelles as drug delivery vehicles Z. Go to our Instructions for using Copyright Clearance Center page for details. The removal of hydrophobic fragments from the aqueous environment and the reestablishing of hydrogen bond network in water decrease free energy of the system and finally form the micelles.

The typical methods used for encapsulation of poorly water-soluble drugs are dialysis method, oil-in-water emulsion solvent evaporation method, and solid dispersion method [ polymeric micelles drug delivery38 ].

Other methods used are direct dissolution [ 39 ], complexation [ 40 ], chemical conjugation [ 41 ], and various solvent evaporation procedures [ 42 ]. Structure of PMs PMs present a great potential as a drug delivery system polymeric micelles drug delivery compounds that are hydrophobic and exhibit poor bioavailability which results from the unique core-shell structure.

Polymeric micelles for drug delivery.

The inner hydrophobic core enables incorporation of poorly water-soluble drugs thus improving their stability and bioavailability. Typically, the inner core of the PMs was formed with hydrophobic blocks of the copolymers by hydrophobic interaction.

Polymeric micelles drug delivery, it can also be formed by electrostatic interactions, using charged block copolymers of oppositely charged macromolecules, resulting in the formation of polyion complex PIC micelles [ 4344 ].

In addition, there have been reports of PMs formed by complexation via hydrogen bonding [ 45 — 47 ] as well as metal-ligand coordination interactions [ 48 ], both referred to as noncovalently connected micelles.

The outer shell of PMs was formed by the hydrophilic blocks of the copolymers, playing an important role in the in vivo behavior, particular for their steric stabilization and ability to interact with the cells [ 49 ]. Lengths of the hydrophobic and hydrophilic blocks affect the conformation of polymers in medium, as lengthier hydrophilic blocks of polymer cause it to remain monomeric in water [ 50 ].


Amphiphilic copolymers which constitute PMs are usually block copolymers [ 5152 ]. Block copolymers can be diblock copolymers or triblock copolymers. Generally, diblock copolymers of the A-B type, where A represents a hydrophilic block and B represents a hydrophobic block, are commonly used to design PMs, whereas triblock copolymers consist of two types of polymers ABA [ 53 ] or three types of polymers ABC.

Most drug carrier applications have been studied with A-B or A-B-A type block copolymers due to the close relationship between the properties of micelles and the structure of polymers [ 54 ].

The physicochemical characteristics of the building blocks influence the physical and biological properties of the PMs [ 55 ]. Hence, micelle-forming block copolymers have been the focus of several studies over the past few years.

For oral drug delivery system, the block copolymers used to form micelles should 1 spontaneously self-assemble in water, 2 enhance drug solubility by several orders of magnitude and provide high loading efficiency, 3 remain stable upon dilution in the GI tract, 4 be biocompatible and nontoxic, and 5 be easy to synthesize at large scale [ 285657 ].

The choice of core-forming polymers is the major determinant for important properties of PMs such as stability, drug loading capacity, and drug release profiles [ 58 ]. Poly propylene oxide PPO [ 5359 ] which belongs to Pluronics, poly esters such as poly lactic acid PLA [ 60 ], hydrophobic poly amino acids [ 61 ], copolymers of lactic acid and glycolic acids [ 6263 ], and poly caprolactone PCL [ 64 ], which are regarded as the commonly used core-forming blocks of Polymeric micelles drug delivery, and have been studied in the past 10 years.

These core-forming polymers cover a wide range of structural diversity and polarity for solubilizing numbers of poorly water-soluble drugs [ 5152 ]. Meanwhile, the chemical nature and molecular weight of the hydrophilic block will strongly affect the stealth properties and accordingly influence the circulation kinetics of the micellar assembly.

Polymeric Micelles: Nanocarriers for Cancer-Targeted Drug Delivery

Poly ethylene glycol PEG is most commonly used as the hydrophilic segment of the block copolymers, since it is a nontoxic polymer with FDA approval as a component of various pharmaceutical formulations. Several physicochemical parameters seem to influence translocation of micelles across the epithelium, including surface hydrophobicity, polymer nature, and particle size [ 69 ].

There polymeric micelles drug delivery many characteristics of PMs that allow them to traverse across the epithelium.

For example, PMs with appropriate particle size can be taken up and then cross the intestinal barrier [ 407071 ]. Furthermore, to achieve a good bioavailability, drugs may be delivered at a specific region in the GI tract, the so-called absorption window. To reach the absorption window, PMs can be polymeric micelles drug delivery by coupling different types of polymers or by grafting various functional groups at the hydrophilic end of the copolymer, such as the pH-sensitive [ 72 — 74 ] and receptor sensitive groups polymeric micelles drug delivery 75 ].

After oral administration, drugs will encounter the harsh physicochemical environment of the GI tract and polymeric micelles drug delivery degraded due to the variation of pH levels as well as the presence of enzymes or bile salts.

To ensure delivery of the carried drugs to the absorption sites, PMs must be able to resist rapid dissociation upon dilution and retain the stable core-shell structure before target sites. It is known that PMs possess two aspects of structural stability, thermodynamic and kinetic, provided by the entanglement of polymer chains in the inner core [ 76 — 78 ].

For a micelle to be thermodynamically stable, the copolymer concentration should be above its CMC. A reverse relationship between the CMC and hydrophobicity of the core-forming blocks has been shown in many studies: The second aspect, kinetic stability of PMs, comes into the picture when the concentration of the copolymer falls below the CMC.