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.