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Lipid-polymer hybrid nanoparticles (NPs) combining the positive attributes of both liposomes and polymeric NPs are increasingly being considered as promising candidates to carry therapeutic agents safely and efficiently into targeted sites. Herein, a modified emulsification technique was developed and optimized for the targeting lipid-polymer hybrid NPs fabrication; the surface properties and stability of the hybrid NPs were systematically investigated, which confirmed that the hybrid NPs consisted of a poly (lactide-co-glycolide) core with ∼90% surface coverage of the lipid monolayer and a ∼4.4 nm hydrated polyethylene glycol (PEG) shell. Optimization results showed that the lipid:polymer mass ratio and the lipid-PEG:lipid molar ratio could affect the size, lipid association efficiency and stability of hybrid NPs. Furthermore, a model chemotherapy drug, 10-hydroxycamptothecin, was encapsulated into hybrid NPs with a higher drug loading compared to PLGA NPs. Surface modification of the lipid layer and the PEG conjugated targeting ligand did not affect their drug release kinetics. Finally, the cytotoxicity and cellular uptake studies indicated that the lipid coverage and the c(RGDyk) conjugation of the hybrid NPs gained a significantly enhanced ability of cell killing and endocytosis. Our results suggested that lipid-polymer hybrid NPs prepared by the modified emulsion technique have great potential to be utilized as an engineered drug delivery system with precise control ability of surface targeting modification.

We have developed a new multifunctional, non-viral gene delivery platform consisting of cationic poly(amine-co-ester) (PPMS) for DNA condensation, PEG shell for nanoparticle stabilization, poly(γ-glutamic acid) (γ-PGA) and mTAT (a cell-penetrating peptide) for accelerated cellular uptake, and a nuclear localization signal peptide (NLS) for enhanced intracellular transport of DNA to the nucleus. In vitro study showed that coating of the binary PPMS/DNA polyplex with γ-PGA promotes cellular uptake of the polyplex particles, particularly by γ-glutamyl transpeptidase (GGT)-positive cells through the GGT-mediated endocytosis pathway. Conjugating PEG to the γ-PGA led to the formation of a ternary PPMS/DNA/PGA-g-PEG polyplex with decreased positive charges on the surface of the polyplex particles and substantially higher stability in serum-containing aqueous medium. The cellular uptake rate was further improved by incorporating mTAT into the ternary polyplex system. Addition of the NLS peptide was designed to facilitate intracellular delivery of the plasmid to the nucleus--a rate-limiting step in the gene transfection process. As a result, compared with the binary PPMS/LucDNA polyplex, the new mTAT-quaternary PPMS/LucDNA/NLS/PGA-g-PEG-mTAT system exhibited reduced cytotoxicity, remarkably faster cellular uptake rate, and enhanced transport of DNA to the nucleus. All these advantageous functionalities contribute to the remarkable gene transfection efficiency of the mTAT-quaternary polyplex both in vitro and in vivo, which exceeds that of the binary polyplex and commercial Lipofectamine™ 2000/DNA lipoplex. The multifunctional mTAT-quaternary polyplex system with improved efficiency and reduced cytotoxicity represents a new type of promising non-viral vectors for the delivery of therapeutic genes to treat tumors.

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Aliphatic copolyesters consisting of diester, diol, and glycolate repeat units were enzymatically synthesized for the first time via lipase-catalyzed polycondensation reactions. Copolymerization of ethyl glycolate (EGA) with diethyl sebacate (DES) and 1,4-butanediol (BD) in the presence of Candida antarctica lipase B (CALB) resulted in the formation of poly(butylene-co-sebacate-co-glycolate) (PBSG) copolyesters with molecular weight (M w) up to 28000 and typical polydispersity between 1.2 and 1.8. The synthesized copolymers contained 10–40 mol % glycolate (GA) units depending on the monomer feed ratio employed. DSC analyses show that the copolyesters with 12–38% GA content are semicrystalline materials that melt between 43 and 59 °C. Free standing nanoparticles with an average size ranging from 250 to 400 nm were successfully fabricated from these PBSG copolymers using a single emulsification-solvent evaporation process. PBSG copolyesters were found to be hydrolytically degradable and doxorubicin- (DOX-) encapsulated PBSG nanoparticles exhibited slow and sustained release of the drug in PBS solution at 37 °C over an extended period of time (60 days). Cellular uptake studies indicate that the drug-loaded PBSG particles are absorbed by a large percentage (up to 95%) of Hela cancer cells within 4 h incubation time. In vitro cytotoxicity investigations reveal that at a same DOX concentration (0.125–2.0 μM), DOX-encapsulated PBSG nanoparticles possess either higher or comparable cytotoxicity toward Hela cells than the free drug DOX·HCl. These results suggest that the PBSG nanoparticles are promising carriers for controlled release delivery of DOX to treat cancers.