Development of Vaccine Adjuvants Using Polymeric Nanoparticles and Their Potential Applications for Anti-HIV Vaccine

Polymers in the Delivery of siRNA for the Treatment of Virus Infections

Viral diseases remain a major cause of death worldwide. Despite advances in vaccine and antiviral drug technology, each year over three million people die from a range of viral infections. Predominant viruses include human immunodeficiency virus, hepatitis viruses, and gastrointestinal and respiratory viruses. Now more than ever, robust, easily mobilised and cost-effective antiviral strategies are needed to combat both known and emerging disease threats. RNA interference and small interfering (si)RNAs were initially hailed as a “magic bullet”, due to their ability to inhibit the synthesis of any protein via the degradation of its complementary messenger RNA sequence. Of particular interest was the potential for attenuating viral mRNAs contributing to the pathogenesis of disease that were not able to be targeted by vaccines or antiviral drugs. However, it was soon discovered that delivery of active siRNA molecules to the infection site in vivo was considerably more difficult than anticipated, due to a number of physiological barriers in the body. This spurred a new wave of investigation into nucleic acid delivery vehicles which could facilitate safe, targeted and effective administration of the siRNA as therapy. Amongst these, cationic polymer delivery vehicles have emerged as a promising candidate as they are low-cost and easy to produce at an industrial scale, and bind to the siRNA by non-specific electrostatic interactions. These nanoparticles (NPs) can be functionally designed to target the infection site, improve uptake in infected cells, release the siRNA inside the endosome and facilitate delivery into the cell cytoplasm. They may also have the added benefit of acting as adjuvants. This chapter provides a background around problems associated with the translation of siRNA as antiviral treatments, reviews the progress made in nucleic acid therapeutics and discusses current methods and progress in overcoming these challenges. It also addresses the importance of combining physicochemical characterisation of the NPs with in vitro and in vivo data.

Polymer-drug interactions in tyrosine-derived triblock copolymer nanospheres: a computational modeling approach

A combination of molecular dynamics (MD) simulations and docking calculations was employed to model and predict polymer-drug interactions in self-assembled nanoparticles consisting of ABA-type triblock copolymers, where A-blocks are poly(ethylene glycol) units and B-blocks are low molecular weight tyrosine-derived polyarylates. This new computational approach was tested on three representative model compounds: nutraceutical curcumin, anticancer drug paclitaxel and prehormone vitamin D3. Based on this methodology, the calculated binding energies of polymer-drug complexes can be correlated with maximum drug loading determined experimentally. Furthermore, the modeling results provide an enhanced understanding of polymer-drug interactions, revealing subtle structural features that can significantly affect the effectiveness of drug loading (as demonstrated for a fourth tested compound, anticancer drug camptothecin). The present study suggests that computational calculations of polymer-drug pairs hold the potential of becoming a powerful prescreening tool in the process of discovery, development and optimization of new drug delivery systems, reducing both the time and the cost of the process.