Micelles and vesicles have long been proposed as carriers for low molecular weight molecules including drugs. Especially micelles are found to be useful for the encapsulation of hydrophobic drugs in the core while maintaining the water solubility of the system with the hydrophilic shell [1]. In addition, their sizes between 20 – 100 nm makes them perfect to target the drug passively to the tumour. Despite their high stability, micelles still tend to break up upon dilution once they reached their lower critical aggregation concentration. Several approaches have been undertaken to stabilise these structures using the crosslinking of the core or shell.
The uptake of the micelle into the tumor cells seems to be the key to success. The ability of several peptides, called cell penetrating peptides (CCPs) or protein transduction domains (PTDs), to translocate across the cell membrane into the cytoplasm and nucleus in an energy independent or receptor-independent manner has been described vividly in literature. The improvement of cell uptake has been reported to be dependent on the presence of arginine and not on the secondary structure. Although many peptides are easily available, we are aiming at exploring synthetic alternatives, which are probably commercially more viable. A range of studies have shown that polymers with guanidine functionalities can indeed enhance cellular uptake [2]. This approach holds great promise, although the potential toxicity of these cationic groups needs to be considered.
Here, we discuss the design of the drug carrier for a range of delivery problems including metal-based drugs [3].