The use of RNA interference mechanism and small interfering RNA (siRNA) in cancer gene therapy is a very promising approach. However, the success of gene silencing is underpinned by the efficient delivery of intact siRNA into the targeted cell. Nowadays, chitosan is one of the most widely studied non-viral vectors for siRNA delivery, since it is a biodegradable, biocompatible and positively charged polymer able to bind to the negatively charged siRNA forming nanoparticles (NPs) that will act as siRNA delivery system. However, chitosan shows several limitations such as low transfection efficiency and low solubility at physiological pH. Therefore, a variety of chemical and non-chemical structural modifications of chitosan were investigated in the attempt to develop a chitosan derivative showing the features of an ideal siRNA carrier. In this review, the most recently proposed chemical modifications of chitosan are outlined. The type of modification, chemical structure, physicochemical properties, siRNA binding affinity and complexation efficiency of the modified chitosan are discussed. Moreover, the resulting NPs characteristics, cellular uptake, serum stability, cytotoxicity and gene transfection efficiency in vitro and/or in vivo are described and compared to the unmodified chitosan. Finally, a critical analysis of a selection of modifications is included, highlighting the most promising ones for this purpose in the future.

Gene therapy has been recently shown as a promising tool for cancer treatment as nanotechnology-based safe and effective delivery methods are developed. Generally, genes are wrapped up in extremely tiny nanoparticles which could be taken up easily by cancer cells, not to their healthy neighboring cells. Several nanoparticle systems have been investigated primarily to address the problems involved in other methods of gene delivery and observed improved anticancer efficacy suggesting that nanomedicine provides novel opportunities to safely deliver genes, thus treat cancer. In this review, various nanoparticle types and related strategies, used in gene delivery for cancer treatment, have been discussed.

Objective (s): Lipid-based nanoparticles (NLP) are PEGylated carriers composed of lipids and encapsulated nucleic acids with a diameter less than 100 nm. The presence of PEG in the NLP formulation improves the particle pharmacokinetic behavior. The purpose of this study was to prepare and characterize NLPs containing MDR1 siRNA and evaluate their cytotoxicity and cellular uptake. MDR1 siRNA could be used in multidrug resistance reversal in cancer therapy.Materials and Methods: siRNAs were encapsulated into NLPs consisted of mPEG-DSPE/DOTAP/DOPE (10: 50: 40 molar ratio) by the detergent dialysis method. The particle diameters of NLPs and their surface charge were measured using dynamic light scattering. siRNA encapsulation efficiency was determined by an indirect method via filtration and free siRNA concentration determination. NLPs cytotoxicity was investigated by MTT assay. The ability of NLPs for siRNA delivery checked in two human cell lines (MCF-7/ADR and EPP85-181/RDB) by fluorescence microscopy and compared with oligofectamine.Results: NLPs containing MDR1 siRNA were prepared with the stable size of 80-90 nm and the zeta potential near to neutral. The siRNA encapsulation efficacy was more than 80%. These properties are suitable for in vivo siRNA delivery. NLPs cytotoxicity studies demonstrated they were non-toxic at the doses used. NLPs improved siRNA localization in both cell lines.Conclusion: NLPs containing MDR1 siRNA can be a good candidate for in vivo siRNA delivery studies.

Small interfering RNAs (siRNA) technology has shown great promise as a new class of therapeutic interventions for the treatment of cancer and other diseases. It is a remarkable endogenous pathway that can regulate sequence-specific gene silencing. Despite the excitement about possible applications of this biological process for sequence-specific gene regulation, the major limitations against the use of siRNA-based therapeutics are their rapid degradation by serum nuclease, poor cellular uptake, and rapid renal clearance following systemic delivery, off-target effects and the induction of immune responses. Many researchers have tried to overcome these limitations by developing nuclease-resistant chemically-modified siRNAs and a variety of synthetic and natural biodegradable lipids and polymers to enhance the efficacy and safety profiles of siRNA delivery. Ideal siRNA-based delivery systems for cancer therapy must be clinically suitable, safe and effective. In this review, we introduce the greatest challenges in achieving efficient RNAi delivery and discuss design criteria and various delivery strategies for cancer therapy, including chemical modifications, lipid-based nanovectors, polymer-mediated delivery systems, conjugate delivery systems, and others.