Nanocarriers types

Numerous experimental therapeutics have shown potency in vitro however, when they are tested in vivo, they often lack significant efficacy. This is often attributed to unfavorable pharmacokinetic properties and systemic toxicity, which limit the maximum tolerated dose. These limitations can be overcome by use of drug carriers. Two general types of carrier systems have been designed drug conjugation to macromolecular carriers, such as polymers and proteins and drug encapsulation in nanocarriers, such as liposomes, polymersomes and micelles. 

Micellar nanocarriers have already been applied successfully for delivery of hydro-phobic drugs [86]. These carriers are usually the product of self-assembled block copolymers, consisting of a hydrophilic block and a hydrophobic block. Generally, an ELP with a transition temperature below body temperature is used as hydrophobic block and the hydrophilic block can be an ELP with a transition temperature above body temperature or another peptide or protein. The EPR effect also directs these types of carriers towards tumor tissue. 

Fig. 30 Types of nanocarriers for drug delivery, (a) Polymeric nanoparticles polymeric nanoparticles in which drugs are conjugated to or encapsulated in polymers, (b) Polymeric micelles amphiphilic block copolymers that form nanosized core-shell structures in aqueous solution. The hydrophobic core region serves as a reservoir for hydrophobic drugs, whereas hydrophilic shell region stabilizes the hydrophobic core and renders the polymer water-soluble.

An attractive strategy to improve CNS drug delivery is to link a nontransportable drug with a vector to the BBB. These moieties can work as molecular Trojan horses to transport across the BBB attached proteins, DNA molecules, and drug micro- and nanocarriers facilitating their penetration through the BBB. The choice of a vector moiety and a type of a linker is crucial for the success of this method of drug delivery. 

List types of nanocarriers for drug delivery. Describe their stiiicture, principal differences, advantages and limitations. 

Figure 47.1. Types of nanocarriers for drug delivery. A liposomes B nanoparticles C nanospheres D nanosuspensions E polymer micelles F nanogel G block ionomer complexes H nanofibers and nanombes.

Pietkiewicz J, Zielinska K, Saczko 1, Kulbacka 1, Majkowski M, and Wilk KA. (2010). New approach to hydrophobic cyanine-type photosensitizer delivery using polymeric oil-cored nanocarriers Hemolytic activity, in vitro cytotoxicity and localization in cancer cells. European Journal of Pharmaceuticals Science, 39, 322-335. 

Various types of nanocarriers have been introduced nowadays, including the... 

On the other hand, PEI nanocarriers have some toxicity problems. They are reported to show two types of toxicity one of them is immediate toxicity due to free PEI. Free PEI interacts with serum proteins which have a negative charge and also erythrocytes. This interaction results in precipitation in huge clusters, adherence to the cell membrane and damage to the plasma membrane. The other type is delayed toxicity as a consequence of cellular processing of the PEI polyplexes. Another toxicity problem also arises from the linear structure of PEI. When PEI polyplexes were administered via the intravenous route to mice, lethal side effects were observed. On the other hand, linear PEIs have higher transfection efficiency and lower cytotoxicity than branched PEIs, according to several studies. ... 

As indicated above, hb star-like architertures can exhibit a core-shell-type topography often with an amphiphilic character that renders the materials a special type of nanocarriers." " ... 

Mishra B, Patel BB, Tiwari S (2010) Colloidal nanocarriers a review on formulation technology, types and applications toward targeted dmg delivery. Nanomedicine 6 9-24... 

The advantages of enzymes-mesoporous silicates system include the potential uses under harsh environmental conditions (chaotropic solvents, high temperatures or ionic strengths, etc.). In the second case, grafting onto, the interaction of the enzyme and nanocarrier is determined not only by the molecular characteristics of both the components but mainly by the environmental conditions such as medium composition, ionic strength, water activity, pH, and temperature among others. So, for this type of system, the major properties of each component must be known. Many systems following the... 

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