Self-assembly Of Graphene Based Nanocapsules Loading An Anti-cancer Drug Capable Of Burst Release Under Remote Control

First, the stable dispersion of graphene oxide (GO) in polyelectrolyte matrix is obtained. Low molecular weight PAH in0.5mol-L-1NaCl solution proves to be essential to inhibit the aggregation of GO nanosheets bridge-linked by polyelectrolyte. On the basis of the aggregation inhibition, the GO-templated nanocapsules are prepared by layer-by-layer (LbL) assembly of poly (allylamine hydrochloride)(PAH) and poly (sodium4-styrenesulfonate)(PSS) on graphene oxide (GO) nanosheets (1.5-2.5μm wide and1.0nm thick). Further, GO is loaded a hydrophobic drug, paclitaxel (PTX), denoted by GO+PTX. Deposition of polyelectrolytes on the GO+PTX nanosheets as template produces nanocapsules capable of burst release at neutral pH, which solves the problem that only low pH=2(the pH range of cancer cells is about5.6-7.6) is reported to stimulate the release of drugs on GO. In order to realize the quick release of PTX at neutral pH by these gold nanoparticles (AuNPs,20-60nm wide), the negatively charged GO and AuNPs are bounded together by the positively charged PAH layer, which can make nanocapsules absorb near infrared (NIR) light. Then we assemble PTX and AuNPs in GO-templated nanocapsules, represented by (GO+PTX)/(PAH/AuNPs)/(PAH/PSS)/PAH. About87%of PTX releases fast from the (GO+PTX)/(PAH/AuNPs)/(PAH/PSS)/PAH nanocapsules within300s under NIR irradiation. A mechanism of burst release of PTX at neutral pH is proposed as follows. AuNPs absorb and convert NIR energy to local heat, decreasing the interactions (π-π stacking and hydrogen bonds) between GO and PTX. The local heat from AuNPs also increases the permeability of the polyelectrolyte layers by changing their conformation, thus enabling fast release of PTX from the nanocapsules. Monodisperse GO (500-680nm wide and0.6nm thick) is also prepared in this thesis by density gradient ultracentrifugation rate, which serves as template for nanocapsules. The corresponding loading capacity of PTX is as high as0.8mg·mg-1. Remotely controlled release of PTX under NIR irradiation is realized as well. This work not only understands better the colloid and interface chemistry of the dispersion stability of GO nanosheets in aqueous solution of polyelectrolytes, but also paves new paths for the development of GO-based advanced nanomaterials and pharmaceutics.