Dendrimer Prodrugs

The main objective of this review is to describe the importance of dendrimer prodrugs in the design of new drugs, presenting numerous applications of these nanocomposites in the pharmaceutical field. Therefore, the use of dendrimer prodrugs as carrier for drug delivery, to improve pharmacokinetic properties of prototype, to promote drug sustained-release, to increase selectivity and, consequently, to decrease toxicity, are just some examples of topics that have been extensively reported in the literature, especially in the last decade. The examples discussed here give a panel of the growing interest dendrimer prodrugs have been evoking in the scientific community.

Surface Engineered Dendrimers in siRNA Delivery and Gene Silencing

BACKGROUND

Therapeutic efficacy of dreadful diseases like cancer, HIV (Human Immunodeficiency Virus) can be enhanced by delivering molecules which regulate function at gene level rather than at receptor level. Silencing RNA is one such approach recently used to silence target gene expressed diseases; and thereby reduce target protein levels. Many of the non-viral vectors are proved to act as carriers for silencing RNA. Dendrimers being one of them have less size, low poly dispersibility index, water solubility, multivalence, and easy surface modification. Many such surface modifications have been carried out to improve the delivery potential of small interfering RNA (siRNA) modified dendrimers compared to simple plain dendrimers.

METHODS

Dendrimer was taken as a core whose surface was modified with fluorine, amino acids, phosphate, lipids, folate, specific antibody or RGD (Arg-Gly-Asp). The purpose of these modifications was to increase the therapeutic siRNA efficiency, lower the toxicity and improve the targeting potential of dendrimers.

RESULTS

Fluorinated dendrimers have highest electronegativity and highest siRNA loading capacity. Amino acid functionalized dendrimers are made up of endogenous amino acids which improve biocompatibility of dendrimer and endosomal escape. Carbosilane dendrimers increase the gene transfection ability of tissues to be treated. Phosphate dendrimers having hydrophobic backbone and hydrophilic surface increase the permeability towards targeted tissue. Lipid based dendrimer causes endosomal escape and improves the permeability of dendrimers. Targeting of specific tissues is achieved by coupling dendrimer with folate, RGD and specific antibody, thereby reducing off target effect.

CONCLUSION

Thus, surface modified dendrimers render a complete pack which offers increased siRNA loading, increased transfection and permeability, efficient targeting, endosomal escape and protecting siRNA from degradation by RNase and other such enzymes. The objective of this manuscript is to provide different approaches currently available for surface modifications of dendrimers and their overall effect on transfection ability of siRNA to target tissues.

Trastuzumab Targeted Neratinib Loaded Poly-Amidoamine Dendrimer Nanocapsules for Breast Cancer Therapy

Background

Human epidermal growth factor receptor2 (Her2) positive breast cancer represents 25% of breast cancer cases. Targeted therapy with Her2 monoclonal antibody, trastuzumab (TZ), represents the first-line treatment for this type of breast cancer. In addition, neratinib, an irreversible inhibitor of the HER-2 receptor tyrosine kinase, has recently been approved as adjuvant therapy to TZ. This study aims to formulate (TZ)-grafted dendrimers loaded with neratinib, allowing a dual treatment alongside reducing the associated resistance as well as targeted therapy.

Methods

TZ was conjugated on the surface of dendrimer using hetero-cross linker, MAL-PEG-NHS, and the zeta potential, and in vitro release of neratinib from dendrimers was characterized. Formulated dendrimers were also fluorescently conjugated with fluorescein isothiocyanate to visualize and quantify their SKBR-3 cellular uptake.

Results

The G4 PAMAM dendrimer showed successful encapsulation of neratinib and a sustained release profile. Comparative in vitro studies revealed that these TZ-targeted dendrimers loaded with neratinib were more selective and have higher antiproliferation activity against SKBR-3 cells compared to neratinib alone and neratinib loaded dendrimer.

Conclusion

In the current study, neratinib loaded in plain and trastuzumab-grafted dendrimer were successfully prepared. Enhanced cellular uptake of trastuzumab conjugated dendrimers was shown, together with a higher cytotoxic effect than plain neratinib dendrimers. These findings suggest the potential of TZ-conjugated dendrimers as targeting carrier for cytotoxic drugs, including neratinib.