Polymeric nanoparticles assembled from the amphiphilic graft copolymer with cyclic benzylidene acetal-functionalized backbone and short poly(2-hydroxyethyl methacrylate) side chains can remain structurally stable at pH 7.4, but undergo stepwise disassembly in mildly acidic conditions due to the acid-triggered cleavage of the acetals, providing a promising nanocarrier for cancer therapy.
Hydrophobization of cationic polymers, as an efficient strategy, had been widely developed in the structure of cationic polymer micelles to improve the delivery efficiency of nucleic acids. However, the distribution of hydrophobic segments in the polymer chains is rarely considered. Here, we have elaborated three types of hydrophobized polyethylene glycol (PEG)-blocked cationic polymers with different distributions of the hydrophobic segments in the polymer chains PEG–PAM–PDP (E–A–D), PEG–PDP–PAM (E–D–A), and PEG–P(AM/DP) (E–(A/D)), which were synthesized by reversible addition–fragmentation chain transfer polymerization of methoxy PEG, cationic monomer aminoethyl methacrylate, and pH-sensitive hydrophobic monomer 2-diisopropylaminoethyl methacrylate, respectively. In aqueous solution, all of the three copolymers, E–A–D, E–D–A, and E–(A/D), were able to spontaneously form nanosized micelles (100–150 nm) (ME–A–D, ME–D–A, and ME–(A/D)) and well-incorporated small interfering RNA (siRNA) into complex micelles (CMs). The effect of distributions of the hydrophobic segments on siRNA delivery had been evaluated in vitro and in vivo. Compared with ME–D–A and ME–(A/D), ME–A–D showed the best siRNA binding capacity to form stable ME–A–D/siRNA CMs less than 100 nm, mediated the best gene-silencing efficiency and inhibition effect of tumor cell growth in vitro, and showed better liver gene-silencing effect in vivo. In the case of ME–(A/D) with a random distribution of cationic and hydrophobic segments, a gene-silencing efficiency higher than Lipo2000 but lesser than ME–A–D and ME–D–A was obtained. As the mole ratio of positive and negative charges increased, ME–D–A/siRNA and ME–A–D/siRNA showed similar performances in size, zeta potential, cell uptake, and gene silencing, but ME–(A/D)/siRNA showed reversed performances. In addition, ME–A–D as the best siRNA carrier was evaluated in the tumor tissue in the xenograft murine model and showed good anticancer capacity. Obviously, the distribution of the hydrophobic segments in the amphiphilic cationic polymer chains should be seriously considered in the design of siRNA vectors.
Abstract The chemical composition of the essential oil obtained from pine cones of Pinus koraiensis and Pinus sylvestris from northeast China was analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS), and 35 and 31 components were identified, respectively. α-pinene (35.2%), limonene (18.4%), β-pinene (8.7%), β-caryophyllene (3.5%) and myrcene (3.0%) were the main components in P. koraiensis cone oil. Aromadendrene (20.2%), α-pinene (18.5%), α-longipinene (10.5%) and α-terpineol (5.5%) were the main components in P. sylvestris cone oil. The antioxidant activity of the oils from P. koraiensis and P. sylvestris was evaluated using the DPPH.
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