Synthetic polymers in 21st century therapeutics: the way forward

Nanotechnologies for Alzheimer's disease: diagnosis, therapy, and safety issues

Alzheimer's disease (AD) represents the most common form of dementia worldwide, affecting more than 35 million people. Advances in nanotechnology are beginning to exert a significant impact in neurology. These approaches, which are often based on the design and engineering of a plethora of nanoparticulate entities with high specificity for brain capillary endothelial cells, are currently being applied to early AD diagnosis and treatment. In addition, nanoparticles (NPs) with high affinity for the circulating amyloid-β (Aβ) forms may induce "sink effect" and improve the AD condition. There are also developments in relation to in vitro diagnostics for AD, including ultrasensitive NP-based bio-barcodes, immunosensors, as well as scanning tunneling microscopy procedures capable of detecting Aβ(1-40) and Aβ(1-42). However, there are concerns regarding the initiation of possible NP-mediated adverse events in AD, thus demanding the use of precisely assembled nanoconstructs from biocompatible materials. Key advances and safety issues are reviewed and discussed.

Complement activation-related pseudoallergy: a new class of drug-induced acute immune toxicity

A major goal in modern pharmacotechnology is to increase the therapeutic index of drugs by using nanoparticulate vehicle systems in order to ensure slow release or targeted delivery of drugs. With all great benefits, however, these innovative therapies can carry a risk for acute immune toxicity manifested in hypersensitivity reactions (HSRs) that do not involve IgE but arises as a consequence of activation of the complement (C) system. These anaphylactoid reactions can be distinguished within the Type I category of HSRs as "C activation-related pseudoallergy" (CARPA). Drugs and agents causing CARPA include radiocontrast media (RCM), liposomal drugs (Doxil, Ambisome and DaunoXome) and micellar solvents containing amphiphilic lipids (e.g., Cremophor EL, the vehicle of Taxol). These agents activate C through both the classical and the alternative pathways, giving rise to C3a and C5a anaphylatoxins that trigger mast cells and basophils for secretory response that underlies HSRs. Pigs provide a useful model for liposome-induced CARPA as minute amounts of reactogenic lipomes cause C activation with consequent dramatic cardiovascular and laboratory abnormalities that mimic some of the human symptoms. Consistent with the causal role of C activation in liposome-induced HSRs, a recent clinical study demonstrated correlation between the formation of C terminal complex (SC5b-9) in blood and the presence of HSRs in patients treated with liposomal doxorubicin (Doxil). Overall, the CARPA concept may help in the prediction, prevention and treatment of the acute immune toxicity of numerous state-of-the-art drugs.

New poly(lactic-co-glycolic acid) derivatives: Modular polymers with tailored properties

Poly(lactic-co-glycolic acid) (PLGA) is one of the most widely used polymers in drug delivery, despite several well-characterized shortcomings. Polymer modification is one approach to improve PLGA-based formulation properties, such as drug stability, drug release profiles, mechanism of polymer degradation and the possibility of drug targeting. A brief summary of recent reports on PLGA modifications is provided and a new class of branched polyester derivatives is introduced. In vitro and in vivo applications of the new branched polyesters as protein carriers, gene delivery vehicles, vaccine adjuvants and pulmonary drug delivery vehicles are described.: