Use of chemotherapeutic agents is often limited by systemic drug toxicity and poor aqueous solubility. Drug-delivery systems based on block copolymer micelles are considered to be a promising approach for improving the therapeutic index and reducing systemic toxicity.– As an amphiphilic diblock copolymer, the biodegradable PCL–PEG copolymer is widely studied for its self-assembling properties and its potential use as a drug carrier., PEG chains on nanoparticle surfaces have been described as efficient drug carriers in the bloodstream with a range of applications, including prolonging the systemic cycle time of colloidal drug delivery systems and evading recognition by cells of the mononuclear phagocyte system. In theory, tumors have vessels with poorly aligned endothelial cells and wide fenestrations, so the long circulation time of block copolymer micelles can increase site-specific tumor accumulation. Meanwhile, PEI, reported to be a “proton sponge”, has been extensively studied in recent years as a nonviral gene vector, because it can absorb DNA by positive and negative electrical interactions. The formation of nanometer-scale complexes showed enhanced potentiation of transfection in vitro and in vivo. In a previous study, a PEI (molecular weight 800) chain was connected to classic PEG-PCL amphiphilic compounds to track the metabolism and distribution of the self-assembled micelles in tumor tissue. Self-assembled micelles were constructed with a positive charge, with the potential for DNA binding. To investigate the feasibility of codelivery of both drug and gene in vitro, mPEG–PCL-g–PEI of various compositions was synthesized. As a three-block amphiphilic polymer, mPEG–PCL-g–PEI contained mPEG, PEI as a hydrophilic segment and PCL as a hydrophobic segment. When the copolymer was dissolved in aqueous solution, hydrophobic molecules spontaneously formed a hydrophobic region by molecular interaction; at the same time, the hydrophilic mPEG chain formed a hydrophilic shell. Following a temperature increase, the molecular movement became more active, and micelles were formed with hydrophilic shells and hydrophobic cores.
Nano-structures of metals such as silver, gold, palladium, platinum, copper, and nickel have been successfully synthesized by using DNA network templates[5-9].In recent years, a number of Ag nanoparticles with different shapes have been widely synthesized by using DNA as the template because of its self-assembly and mechanical properties, as well as the high affinity between DNA bases with Ag+ cations.
Influenza Vaccines for the Future — NEJM
Wang M, Lowik DW, Miller AD and Thanou M (2009b) Targeting the urokinase plasminogen activator receptor with synthetic self‐assembly nanoparticles. Bioconjugate Chemistry 20: 32–40.