A hydrotropic agent, salicylic acid (SA), was grafted to chitosan oligosaccharide (CSO) backbone to develop a CSO/SA conjugate. The CSO/SA self-assembled to form nanoparticles (NPs) in aqueous medium. The sizes of the NPs were smaller as more SA was grafted and when lower molecular weight CSO was used. The ζ-potentials of all CSO/SA NPs were above 40 mV. The critical aggregation concentrations of NPs decreased from 454.79 to 164.0 μg/mL by increasing the grafted SA content or the CSO Mw. Paclitaxel (PTX)-loaded NPs were prepared by a dialysis method; the particle sizes and ζ-potentials were smaller than the blank NPs. A series of PTX-loaded CSO28,000/SA50% NPs were prepared; as the size decreased or the drug content increased, the in vitro release rate increased. The in vitro cytotoxicity of blank CSO/SA NPs was determined using the MCF-7 cell line. The CSO/SA provides a new means of making a stable delivery for PTX.
Understanding of the mechanism and dynamics of DNA loading into carbon nanotubes (CNTs) is very important for the promising applications of CNTs in DNA sequencing, drug delivery and gene delivery systems etc. In this work, the loading mechanism and dynamics of different ssDNA oligomers into singlewalled carbon nanotubes (SWNTs) was investigated through molecular dynamics simulations, steered molecular dynamics simulation and binding free energy calculations. Our simulation results showed that the loading of different ssDNA oligomers into the zigzag SWNT is much easier than the armchair SWNT does. Confined in both zigzag and armchair type SWNTs, ssDNA oligomers have helical structure and their bases adapt the orientation that parallel to the interior wall. From detailed analysis of the interaction energy, potential of mean force (PMF) of unloading process and nucleotide binding free energy, our results show that the chirality of SWNTs has large effect on the binding strength of nucleotides, and hence affect the loading dynamics of ssDNA into SWNTs.
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