Self assembly of Star Shaped Amphiphiles- potential for drug delivery

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Kolawole, OM
Uchegbu, IF
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University College London School of Pharmacy, London, United Kingdom
In order to study the influence of branching on the self-assembly of PEG amphiphiles, polyethylene glycol (PEG)-based star-shaped amphiphiles have been synthesised and studied as self-assembling systems. Palmitoyl (C16) groups were grafted to 8-armed PEG with differing degrees of palmitoylation (P8PEG1 & P8PEG4). A novel amphiphilic linear analogue (HDPEG) was also synthesised with hexadecyl (C16) pendant groups for comparison. These amphiphiles were characterised using 1H Nuclear Magnetic Resonance, Fourier Transform-Infrared and MALDI-TOF mass spectroscopy. The Pyrene probe was employed to evaluate self assembly properties while Photon Correlation Spectroscopy was used to measure particle size distribution. Molecular architecture and hydrophobic substitution had a profound effect on their self-assembly behavior; as P8PEG4 with branched architecture and the greatest degree of hydrophobic substitution had the lowest polydispersity index. Also, the critical micellar concentration (CMC) for P8PEG4, P8PEG1 and HDPEG were 3, 8 and 15 μM respectively, inferring greater micelle stability with branched architecture and increased hydrophobic substitution. Particle size and morphology were confirmed by Transmission electron microscopy as P8PEG4 and HDPEG formed mixtures of micelles and nanoparticles while a novel core-shell nano- and micro self assembly was observed for P8PEG1. Preliminary drug encapsulation studies on the amphiphiles loaded low amounts of Griseofulvin (0.04-0.09mg/ml with 5mg/ml of polymers). These resulting stable aggregates of PEG-based amphiphiles may be of benefit for drug delivery applications. However, future studies should focus on influence of polymer architecture on drug encapsulation in order to improve their encapsulation efficiency.
Self-assembly , Polyethylene glycol , palmitoyl groups , drug delivery , star shaped amphiphiles , linear amphiphiles
Kolawole OM, Uchegbu (2010). Self assembly of Star Shaped Amphiphiles- potential for drug delivery, Master of Science in Drug Delivery Dissertation